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An Aerodynamic Equation of State—Part I: Introduction and Aerospace Applications - QA Test Tatsiana01-17-01-00014/19/2023
Abstract In subsonic aircraft design, the aerodynamic performance of aircraft is compared meaningfully at a system level by evaluating their range and endurance, but cannot do so at an aerodynamic level when using lift and drag coefficients, CL and CD , as these often result in misleading results for different wing reference areas. This Part I of the article (i) illustrates these shortcomings, (ii) introduces a dimensionless number quantifying the induced drag of aircraft, and (iii) proposes an aerodynamic equation of state for lift, drag, and induced drag and applies it to evaluate the aerodynamics of the canard aircraft, the dual rotors of the hovering Ingenuity Mars helicopter, and the composite lifting system (wing plus cylinders in Magnus effect) of a YOV-10 Bronco. Part II of this article applies this aerodynamic equation of state to the flapping flight of hovering and forward-flying insects. Part III applies the aerodynamic equation of state to some well-trodden cases in fluid mechanics found in fluid-mechanics textbooks.
Burgers, Phillip
Aerodynamic Optimization of Vehicle Configuration Based on Adjoint Method2020-01-09154/14/2020
Due to the increasingly stringent environmental regulations all around the world confronted by exhaust emission and energy consumption, improving fuel economy has been the top priority for most automotive manufacturers. In this context, the basic process for vehicle shape development has evolved into optimizing the design to achieve better aerodynamic characteristics, especially drag reduction. Of all the optimization approaches, the gradient-based adjoint method has currently received extensive attention for its high efficiency in calculating the objective sensitivity with respect to geometry parameters, which is the first and foremost step for subsequent shape modification. In this work, the main goal is to explore the adjoint method through optimizing the vehicle shape for a lower drag based on a production SUV. Firstly, the influence of different mesh schemes was discussed on sensitivity prediction of aerodynamic drag. Secondly, according to the sensitivity distribution, several key areas, like the side mirrors, A pillars, air dam, and rear lamps, were respectively altered through mesh morphing process. Furthermore, the optimized effect was validated by steady as well as transient simulation. Steady Reynolds Averaged Navier Stokes (RANS) approach was used for the primal flow solution of adjoint calculations, while transient simulation with Stress Blended Eddy Simulation (SBES) was also performed on the baseline and the optimized vehicle for more detailed flow field structure. The overall drag reduction is approximately 8counts for steady result, and 10counts for unsteady solution. Finally, the drag reduction effect of the optimized side mirrors and air dam was correlated with full-scale wind tunnel test. This paper evaluates the effectiveness of adjoint method for aerodynamic optimization of a production vehicle, which indicates more extensive and promising application of this approach in the early stage of vehicle development for its high efficiency as well as strong robustness.
Ren, Chao, Zhou, Hua, Wu, Haibo, Chen, Qian, Jadhav, Tushar
Hyundai brings brave new tech to 2020 Sonata20AUTP02_131/1/2020
Amid a steadily contracting sedan universe, Hyundai has dug in its heels and thoroughly redesigned and engineered its Sonata for 2020. The eighth-generation model sports a shapely (to our eyes) exterior form slightly reminiscent of Audi's A7. It's underpinned by a new platform shared with its 2021 Kia Optima cousin that will serve multiple FWD/AWD passenger cars and crossovers, according to senior U.S. product-planning manager, Mike Evanoff. New technology applications include a “Digital Key” that allows Sonata drivers to unlock and start their cars via their smart phones, Hyundai's first continuously-variable valve duration system in the new 1.6-L turbo engine, and a solar array that extends driving range in a new hybrid propulsion option.
Brooke, Lindsay
Nonlinear IMM-SUKF Algorithm for Maneuvering Target Tracking with Bearings-Only Measurement2019-01-600512/30/2019
Abstract In this paper, we present an efficient filtering algorithm to perform accurate estimation in jump Markov nonlinear systems, which we aim to contribute in solving the problem of model-based body motion estimation using bearings-only measurement, the Interacting Multiple Model (IMM) algorithm is specially designed to track accurately maneuvering targets whose state and/or measurement (assumed to be linear) models change during motion transition. However, when these models are nonlinear, the IMM algorithm must be modified in order to guarantee an accurate track. In this paper we propose to avoid the Extended Kalman Filter (EKF) because of its limitations and substitute it with the Scaled Unscented Kalman Filter (SUKF) which seems to be more efficient especially according to the simulation results obtained with the Interacting Multiple Model Scaled Unscented Kalman Filter (IMM-SUKF).
Sebbagh, Abdennour, Kechida, Sihem
Understanding Base Oils and Lubricants for Electric Drivetrain Applications2019-01-233712/19/2019
ABSTRACT The penetration of hybridization and electrification (HEV and EV) technology into automotive powertrain designs is an evolving trend resulting from global regulations intended to reduce transportation-related emissions of greenhouse gases and other pollutants and to improve vehicle fuel efficiency. In many HEV and EV hardware designs, drivetrain fluids have contact with the integrated electric motor (e-motor), which requires electrical and thermal properties to be considered in addition to traditional fluid properties. This paper discusses new insights gained around electrical and thermal properties of drivetrain fluids, with a specific emphasis on understanding the critical impacts of base oils (BOs). Electrical and thermal properties data as a function of temperature for a range of BOs as well as automatic transmission fluids are shared. We found that BOs and their viscosities play a critical role in cooling performance, while additives play a critical role in electrical conductivity (EC). That being said, we also have observed that additives in BOs can modify cooling performance. We will demonstrate how each component in the additive package affects EC and in some cases cooling performance. The successful utilization of this knowledge is demonstrated on a proof-of-principle basis to show that fluids with appropriate electrical and thermal properties can be designed to meet critical factors for electrification such as cooling capacity and EC, while still maintaining essential performance features for conventional driveline fluids.
Kwak, Yungwan, Cleveland, Christopher, Adhvaryu, Atanu, Fang, Xinggao, Hurley, Susie, Adachi, Tsuneo
Three-dimensional simulations of oil dilution in DI diesel engines under motoring conditions with varying injection timing2019-01-218612/19/2019
ABSTRACT This study presents a simulation method for oil dilution in diesel engines by a post injection to understand the oil dilution mechanism and to improve an empirical model predicting the evolution of oil dilution. To consider the wall film, two-dimensional governing equations are additionally solved along the cylinder wall. Primary critical Weber numbers are used to determine adhesion or a splash of droplets at wall impingements. Motoring engine simulations at different injection timings show that dilution ratios in simulations are in good agreements with those in experiments. Oil dilution is not proportional to injection timings in this motoring conditions.
Hori, Tsukasa, Yamaji, Kohei, Akamatsu, Fumiteru
Analysis on flow motion and combustion process in pre-chamber and main chamber for low-speed two-stroke dual-fuel engine2019-01-217512/19/2019
ABSTRACT Low-speed two-stroke dual-fuel engines has been paid more attention due to the energy efficiency design index and Tier III emissions limitations issued by International Marine Organization. Although the dual-fuel engines have strong merits on emissions reduction, which can reach the IMO Tier III without aftertreatment, the power output is much lower than that of diesel engines. Therefore, the dual-fuel engine is also needed to improve continuously. However, the mixing and combustion processes in the engine have not been fully understood. In this study, a 3D-CFD model of the dual-fuel engine was established using CONVERGE to explore the mixing and combustion processes. Locally embedding fine grids are considered at scavenging ports, natural gas injection ports, pre-chamber. The model was validated by experimental in-cylinder pressure. Then, the flow motion, mixing of natural gas and air, flow in pre-chamber, torch and combustion in main-chamber were analyzed based on swirl variation, flow velocity distribution, equivalence ratio distribution and torch propagation.
Liu, Long, Wu, Yue, Xiong, Qian, Liu, Teng
CFD-Driven Preliminary Investigation of Ethanol-Diesel Diffusive Combustion in Heavy-Duty Engines2019-01-219212/19/2019
ABSTRACT The introduction of renewable alcohols as fuels for heavy-duty engines may play a relevant role for the reduction of the carbon footprint of the transport sector. The direct injection of ethanol as main fuel and diesel as pilot fuel in the engine combustion chamber through two separate injectors may allow good combustion controllability over the entire engine operating range by targeting diffusive combustion. Closed-cycle combustion simulations have been carried out using AVL FIRE coupled to AVL TABKIN for the implementation of the Flamelet Generated Manifold (FGM) chemistry reduction technique in order to investigate the influence of the injection system geometry and the injection strategy of pure ethanol and diesel fuel on ignition characteristics and combustion at different operating conditions.
Giramondi, Nicola, Mihaescu, Mihai, Erlandsson, Anders Christiansen, Jäger, Anders
Wall Heat Transfer Modeling Based on the Energy Equation For Zero Dimensional Engine Simulation2019-01-231312/19/2019
ABSTRACT It was important for predicting wall heat flux to apply wall heat transfer model by taking into account of the behavior of turbulent kinetic energy and density change in wall boundary layer. Although energy equation base wall heat transfer model satisfied above requirements, local physical amounts such as turbulent kinetic energy in near wall region should be applied. In this study, in order to predict wall heat transfer by zero dimensional analysis, how to express wall heat transfer by using mean physical amounts in engine combustion chamber was considered by experimental and numerical approaches.
Harada, Yuji, Uchida, Kenji, Yamashita, Hiroyuki
Oxidation of Soybean Biodiesel Fuel in Diesel Engine Oils04-12-03-001512/5/2019
Abstract During diesel engine operation, some fuel is entrained in engine oil, particularly as a consequence of strategies to regenerate NOx traps or particle filters. This “fuel dilution” of oil can adversely affect engine oil properties and performance. Compared to diesel fuel, biodiesel is more prone to fuel dilution and more susceptible to oxidation. Oxidation stability experiments were conducted at 160°C using a modified Rapid Small-Scale Oxidation Test (RSSOT) and a Rancimat instrument with 0, 5, 10, and 20 wt% biodiesel in four fully formulated engine oils, two partially formulated engine oils, and two base oils. These experiments showed decreasing oxidation stability with increasing biodiesel content. An exception was noted with the least stable oils (two base oils and one engine oil) in which 5 wt% biodiesel improved the oxidation stability relative to oil without biodiesel. Experiments with biodiesel distillation fractions identified this stability enhancement within the least volatile biodiesel fraction, consistent with natural antioxidants in the biodiesel. Omission of two engine oil additives, antioxidants and zinc dialkyldithiophosphates (ZDDP), led to an unexpected increase in oxidation stability (with and without biodiesel). Time-series oxidation experiments at 160°C with one of the fully formulated engine oils, with and without 20 wt% biodiesel, demonstrated that the biodiesel caused greater oxidation instability and extent of oxidation, greater formation of peroxides and reduction in total base number (TBN), increased ester content, and higher density. Kinematic viscosity increased with aging time and eventually surpassed that of the engine oil aged without biodiesel. With extended aging time, the fully formulated engine oil containing biodiesel “broke,” forming black tar-like materials with high viscosity.
Ball, James C., Anderson, James E., Duckworth, Jacob A., Uy, Dairene, Wallington, Timothy J.
Gas Metal Arc Welding Process Parameter Optimization to Reduce Porosity Defect in a Longitudinal Seam Welding of Pressure Vessels05-13-01-000512/2/2019
Abstract Pressure vessels are critical equipment used in industries for storing liquids or gases at a pressure significantly different from ambient conditions. Porosity is one of the major weld defects in pressure vessels that leads to failure during inspection and as well as during its service. Gas Metal Arc Welding (GMAW) process is widely used in industries to fabricate pressure vessels using carbon steel “IS 2062 E250BR” material for storing compressed air. The main objective of this article is to reduce the porosity defect in the longitudinal seam (LS) welding of the pressure vessels. Detailed analysis is carried out to identify the parameters which are influencing the porosity defect. Central Composite Design (CCD) and Response Surface Methodology (RSM) approaches are used to find the optimum value of the weld parameters which produce weld without porosity or any major defects in the pressure vessel. An experimental setup has been established and welding experiments have been conducted under a controlled environment. Experiments were conducted without any external disturbances ensuring clean weld surface and filler wire without any moisture, rust, oil, and the presence of any organic materials. For all the weld specimens, visual and radiography examinations were carried out to identify the severity of porosity. A porosity index is proposed in this study for conducting statistical analysis. Statistical analysis shows current, travel speed, gas flow rate, and torch angle have a linear relationship and stickout distance has a nonlinear relationship with porosity. In square term, stickout distance has a significant influence on porosity defect. In two-way interaction studies, current and gas flow rate, current and torch angle, and travel speed and torch angle have a significant influence on porosity. Confirmatory tests were carried out to validate the optimum weld parameters obtained in this study.
Kuppusamy, A., Rameshkumar, K., Sumesh, A., Premkumar, S.
Aerodynamic Analysis of Race Car Using Active Wing Concept2019-28-239511/21/2019
In high speed race cars, aerodynamics is an important aspect for determining performance and stability of vehicle. It is mainly influenced by front and rear wings. Active aerodynamics consist of any type of movable wing element that change their position based on operating conditions of the vehicle to have better performance and handling. In this work, front and rear wings are designed for race car prototype of race car. The high down force aerofoil profiles have been used for design of front and rear wing. The first aerodynamic analysis has been performed on baseline model without wings using CFD tool. For investigation, parameters considered are angle of attack in the range of 0-18° for front as well as rear wing at different test speeds of 60, 80, 100 and 120 kmph. The simulation is carried out by using ANSYS Fluent. The simulation results show significant improvement in vehicle performance and handling parameters. To validate the results, a scaled model prototype is manufactured and tested in wind tunnel.
P Bhanushali, Prakash, Agrewale, Mohammad Rafiq, Vora, Kamalkishore
Stall Mitigation and Lift Enhancement of NACA 0012 with Triangle-Shaped Surface Protrusion at a Reynolds Number of 105 01-12-02-000711/21/2019
Abstract Transient numerical simulations are conducted over a NACA 0012 airfoil with triangular protrusions at a Reynolds number (Re) of 100000 using the γ-Reθ transition Shear Stress Transport (SST) turbulence model. Protrusions of heights 0.5%c, 1%c, and 2%c are placed at one of the three locations, viz, the leading edge (LE), 5%c on the suction surface, and 5%c on the pressure surface, while the angle of attack (AOA) is varied between 0° and 20°. Results obtained from the time-averaged solution of the unsteady Navier-Stokes equation indicate that the smaller protrusion placed at 5%c on the suction surface improves the post-stall lift coefficient by up to 59%, without altering the pre-stall characteristics. The improvement in time-averaged lift coefficients comes with enhanced flow unsteadiness due to vigorous vortex shedding. For a given protrusion height, the vortex shedding frequency decreases as the AOA is increased, while the amplitude of fluctuations in lift coefficient increases as the protrusion height is increased or as the AOA is increased. Nevertheless, mitigation of static stall phenomena is observed for most configurations investigated, and this finding can be beneficial for the design of Unmanned Aerial Vehicles (UAVs) and Micro Aerial Vehicles (MAVs). The enhancement in the vortex shedding frequencies due to triangular protrusion can be utilized for Vortex-Induced Vibrations (VIVs)-based energy generators.
Bodavula, Aslesha, Yadav, Rajesh, Guven, Ugur
Aerodynamic Analysis of a Passenger Car to Reduce Drag Using Active Grill Shutter and Active Air Dam2019-28-240811/21/2019
Active aerodynamics can be defined as the concept of reducing drag by making real-time changes to certain devices such that it modifies the airflow around a vehicle. Using such devices also have the added advantages of improving ergonomics and performance along with aesthetics. A significant reduction in fuel consumption can also be seen when using such devices. The objective of this work is to reduce drag acting on a passenger car using the concept of active aerodynamics with grill shutters and air dams. First, analysis has been carried out on a baseline passenger car and further simulated using active grill shutters and air dams for vehicle speed ranging from 60 kmph to 120 kmph, with each active device open from 0° to 90°. The optimized model is then validated for a scaled down prototype in a wind tunnel at 80kmph. Vehicle has been modelled using SolidWorks tool and the simulation has been carried out using ANSYS Fluent. The result shows a significant drag reduction of 12.23% using active grill shutters and air dams.
Tandon, Raghav, Agrewale, Mohammad Rafiq, Vora, Kamalkishore
Material Characterization of Extruded Aluminum Axial Tubes as Energy-Absorbing Structural Members05-13-01-000411/21/2019
Abstract The increasing use of aluminum alloy extrusion in automotive vehicle chassis as structural members has necessitated the need to investigate their crushing behaviors. This article experimentally examines in detail, for the first time with respect to strength, ductility, and microstructure, AA6063-T7 (overaged) condition and the standard T6 temper and their capacity to meet crashworthiness requirements. Both tempers were assessed based on their mechanical properties (strength, ductility, true stress/strain behavior to necking, plastic anisotropy, strain rate sensitivity, and post-instability ductility to fracture) and microstructure, which were determined using basic tensile testing methods and metallographic approach. The implications of these properties/microstructures were further assessed experimentally by investigating the crushing behavior and energy absorption capacities of two extruded geometric profiles: a general rectangular profile and a novel cross-shaped profile investigated in a previous study. Typical modes of collapse were observed for rectangular tubes. In the case of the cross-shaped tubes, geometric modifications in the form of horizontal grooves along the sidewalls were introduced to promote controlled, stable, and repeatable folding patterns during the collapse in addition to serving as peak force reducers. It was concluded that the basic tensile test data recorded up to the point of necking failed to describe accurately the performances of both tempers (T6 and T7) of AA6063 alloy. The post-instability data of the alloys served as a better predictor of material behavior in assessing the crashworthiness of tubes under axial compression. Furthermore, novel cross-shaped tubes outperformed conventional rectangular shaped tubes and showed tremendous potential as energy-absorbing members for applications where weight savings is desired by using aluminum alloys over steel alloys.
Ali, Muhammad, Ohioma, Eboreime, Kraft, Frank, Jenson, Sean
An Optimization Framework for Fixture Layout Design for Nonrigid Parts: An Automotive Perspective05-13-01-000111/19/2019
Abstract The inspection process of non-rigid parts during manufacturing and assembly is inherently challenging. This is exacerbated by the need for accurate real-time part data in the digital age. Although many ad hoc techniques exist, there are no rigorous methods to evaluate the quality of a fixture layout before final parts and gauges are available. This typically happens so late in the manufacturing process that errors found can scarcely be remedied. Additionally, the modifications to the gauge are usually costly and can result in significant delays, when performed this late in the process. This article proposes an optimization-driven mathematical approach tailored toward non-rigid parts to identify the best locator layout, early in the part design phase. A metric is proposed using robotic grasping theory to quantify the quality of the locating scheme and serves as the objective of optimization. The proposed method is implemented using a tolerancing software that performs finite element analysis (FEA) on the parts to predict its state given the force and torque inputs, including the effect of gravity. An evolutionary algorithm is used that optimizes the performance of the fixture layout. We demonstrate a significant improvement in gauge repeatability when compared with an arbitrary layout scheme on two design problems. The first problem is a representative design problem using a sheet metal part, while the second one is an actual automotive production part. General recommendations regarding fixture layout design for non-rigid parts are made, as well as directions for future work are provided.
Slon, Christopher, Pandey, Vijitashwa
Nondestructive Measurement of Residual Strain in Connecting Rods Using Neutrons05-12-03-001810/15/2019
Abstract Increasing the strength of materials is effective in reducing weight and boosting structural part performance, but there are cases where the residual strain generated during the process of manufacturing of high-strength materials results in a decline of durability. It is therefore important to understand how the residual strain in a manufactured component changes due to processing conditions. In the case of a connecting rod, because the strain load on the connecting rod rib sections is high, it is necessary to clearly understand the distribution of strain in the ribs. However, because residual strain is generally measured by using X-ray diffractometers or strain gauges, measurements are limited to the surface layer of the parts. Neutron beams, however, have a higher penetration depth than X-rays, allowing for strain measurement in the bulk material. The research discussed within this article consists of nondestructive residual strain measurements in the interior of connecting rods using the Second Generation Neutron Residual Stress Mapping Facility (NRSF2) at Oak Ridge National Laboratory (ORNL), measuring the Fe (211) diffraction peak position of the ferrite phase. The interior strain distribution of the connecting rod, which was prepared under different manufacturing processes, was revealed. By the visualization of interior strains, clear understandings of differences in various processing conditions were obtained. In addition, it is known that the peak width, which is also obtained during measurement, is suggestive of the size of crystallites in the structure; however, the peak width can additionally be caused by microstresses and material dislocations.
Ikeda, Tomohiro, Jeffery, Bunn R., Fancher, Christopher M., Motani, Ryuta, Matsuda, Hideki, Okayama, Tatsuya
Comparison of Regulated and Unregulated Emissions and Fuel Economy of SI Engines with Three Fuels: RON95, M15, and E1004-12-03-001310/4/2019
Abstract This article focuses on a comparative research of the emissions discharged from four vehicles equipped with SI engines, which comply with different emission control systems (Euro 6, Euro 5, and Euro 3). The vehicles used for this work were installed with two different fuel injection technologies (direct injection and port fuel injection) and were operated with three different types of fuels (RON 95, M15, and E10). The tests were performed at the Joint Research Center (JRC) in Ispra using a state-of-the-art emissions test facility according to the European emissions legislation. The test bench included a chassis dynamometer and two different driving cycles were used: NEDC and US06. The main conclusions observed by this article are: (1) Emissions levels from vehicles fueled with M15 are similar to or lower than from those fueled with RON95. (2) Using M15 has the potential to decrease carbon dioxide emissions and to save fuel on an energetic basis. (3) PM emissions are lower for gasoline/alcoholic fuels. (4) No statistically significant effects on carbonyl emissions were found with M15.
Goldwine, Gideon, Sher, Eran, Sher, Diana
Safety and Lateral Dynamics Improvement of a Race Car Using Active Rear Wing Control2019-01-06434/2/2019
As the forward speed of a car increases, the safety of the vehicle and the driver becomes a more significant concern. Active aerodynamic control can effectively enhance the lateral stability of high speed vehicles over tight cornering maneuvers. A split rear wing has been proposed. By means of manipulating the attack angles for the right and/or left parts of the split rear wing, a favorable yaw moment may be achieved to ensure the lateral stability of the vehicle. However, active control of the split rear wing has not been adequately explored. This paper proposes a novel active split rear wing, which can improve the lateral stability over tight cornering maneuvers, and will not degrade the longitudinal dynamics of the vehicle. A Linear Quadratic Regulator (LQR) based controller for the active split rear wing is designed using a linear vehicle model. In order to examine the performance of the active split rear wing, Numerical simulation is carried out using the LQR based controller and a yaw-plane vehicle model designed in MATLAB. The effectiveness of the proposed active split rear wing is demonstrated by the results derived from the numerical simulation.
Hammad, Mohammed, Qureshi, Khizar, He, Yuping
Using Computational Fluid Dynamics for the Design, Assessment and Optimization of an Aerodynamic Body Kit on a Newly Designed Formula SAE Collegiate Competition Vehicle2019-01-06424/2/2019
Formula SAE Collegiate Competition teams now regularly integrate aerodynamic body kits with their vehicles which have significant benefits in producing downforce. This use of body kits (or aero packages) and the improvement to vehicle aerodynamics they provide, have resulted in these systems becoming a necessity for any team wishing to remain competitive in Formula SAE (FSAE). To address this the Lawrence Technological University (LTU) Formula SAE team incorporated an aerodynamic body kit into their 2018 vehicle. Using computational fluid dynamics (CFD) an aerodynamic analysis was performed comparing the efficacy of a car that did not have an aero package to a car that did. Two separate simulation programs were employed to effectively and accurately assess this change. By using both SolidWorks and SimScale software to generate data, the results of each were compared to assess the accuracy of each. These programs were selected due to their accessibility to engineering students, as well as their parent companies being LTU Formula SAE team sponsors. Simulations were run under different conditions to determine the optimal design of the aero package, as well as to understand how the body kit performed at different velocities. It is expected that the approaches used and understanding gained from this initial effort will serve as a foundational body-of-knowledge for future LTU teams. Those LTU teams each year will be able to modify and refine these now-available CFD tools to assess and optimize their aero package for each new vehicle they design and build annually.
Alemara, Mohammed, McCann, Morgan, Fletcher, Robert, Al-Qarishey, Hussein, Fine, Joshua
Aerodynamic Development of the 2019 Chevrolet Corvette C7 ZR12019-01-06654/2/2019
This paper presents an overview of the aerodynamic development of the 2019 Chevrolet Corvette C7 ZR1. Extensive wind tunnel testing and computational fluid dynamics simulations were completed to engineer the ZR1’s aerodynamics to improve lift-to-drag efficiency and track capability over previous Corvette offerings. The ZR1 architecture changes posed many aerodynamic challenges including increased vehicle cooling, strict packaging demands, wider front track width, and aggressive exterior styling. Through motorsports-inspired aerodynamic development, the ZR1 was engineered to overcome these challenges through the creation of new devices such as a raised rear wing and front underwing. The resulting Standard ZR1 achieved a top speed of 212 mph making it the fastest Corvette ever [1]. Optionally, the ZR1 with the ZTK Performance Package provides the highest downforce of any Corvette, generating approximately 950 pounds at the ZTK’s top speed [1].
Nastov, Alexander, Caples, David
Increasing the Aerodynamic Performance of a Formula Student Race Car by Means of Active Flow Control2019-01-06524/2/2019
This article involves an experimental study regarding the capability of fluidic actuators to increase the aerodynamic performance of a four-element race car rear wing. Sweeping jet actuators are integrated in the upper flap, of which the angle of attack is increased by up to ΔαF3 = 40° with reference to a passively optimized setup. Different velocities of the emitted sweeping jets are applied to study the influence of momentum coefficients cμ = 0.04 … 0.98%. To prove the feasibility of the approach, flow control is first applied to a stand-alone rear wing tested in a small wind tunnel. Subsequently, a realistic race car model featuring the controlled rear wing is investigated in a larger-scale wind tunnel. Employing particle image velocimetry, flow visualization techniques as well as pressure and force measurements, we show that the velocity field on the suction side of the upper flap is characterized by flow separation of different degrees when the angle of attack is increased beyond ΔαF3 = 20° (rear wing only) and ΔαF3 = 30° (complete race car). Generally, the employed fluidic devices have a positive impact in terms of the aerodynamic performance for all investigated angles of attack as overall downforce increases by up to 22 % are achieved, however accompanied by larger drag. Nonetheless, an in-house simulation indicates a potential lap time reduction of 0.17 % at the Formula Student endurance race circuit at Hockenheim under permanent actuation. Even greater gains are to be expected for a selective employment during cornering only or for skidpad and acceleration competitions.
Steinfurth, Ben, Berthold, Arne, Feldhus, Steffen, Haucke, Frank, Weiss, Julien
Fine Tuning the SST k − ω Turbulence Model Closure Coefficients for Improved NASCAR Cup Racecar Aerodynamic Predictions2019-01-06414/2/2019
Faster turn-around times and cost-effectiveness make the Reynolds Averaged Navier-Stokes (RANS) simulation approach still a widely utilized tool in racecar aerodynamic development, an industry where a large volume of simulations and short development cycles are constantly demanded. However, a well-known flaw of the RANS methodology is its inability to properly characterize the separated and wake flow associated with complex automotive geometries using the existing turbulence models. Experience suggests that this limitation cannot be overcome by simply refining the meshing schemes alone. Some earlier researches have shown that the closure coefficients involved in the RANS turbulence modeling transport equations most times influence the simulation prediction results. The current study explores the possibility of improving the performance of the SST k − ω turbulence model, one of the most popular turbulence models in motorsports aerodynamic applications, by re-evaluating the values of certain model closure constants. A detailed full-scale current generation NASCAR Cup racecar was used for the investigation. The simulations were run using a commercial CFD package STAR-CCM+ (version 13.04.010). Five different closure coefficients in the SST k − ω model, σk1, σk2, σω1, σω2 and β∗, were examined. The investigation suggests the influence of each closure coefficient on the simulation prediction results are significantly different. β∗ appeared to be the most sensitive closure coefficient whereas both σk1 and σk2 had almost no effect on the NASCAR Cup racecar aerodynamic predictions. This study proposes a new set of SST k − ω turbulence model closure coefficients which has the potential of providing better-correlated aerodynamic predictions of a NASCAR Cup racecar under a range of different operating conditions.
Fu, Chen, Bounds, Charles, Uddin, Mesbah, Selent, Christian
Investigation of Drag Reduction Technologies for Light-Duty Vehicles Using Surface, Wake and Underbody Pressure Measurements to Complement Aerodynamic Drag Measurements2019-01-06444/2/2019
A multi-year, multi-vehicle study was conducted to quantify the aerodynamic drag changes associated with drag reduction technologies for light-duty vehicles. Various technologies were evaluated through full-scale testing in a large low-blockage closed-circuit wind tunnel equipped with a rolling road, wheel rollers, boundary-layer suction and a system to generate road-representative turbulent winds. The technologies investigated include active grille shutters, production and custom underbody treatments, air dams, wheel curtains, ride height control, side mirror removal and combinations of these. This paper focuses on mean surface-, wake-, and underbody-pressure measurements and their relation to aerodynamic drag. Surface pressures were measured at strategic locations on four sedans and two crossover SUVs. Wake total pressures were mapped using a rake of Pitot probes in two cross-flow planes at up to 0.4 vehicle lengths downstream of the same six vehicles in addition to a minivan and a pick-up truck. A smaller rake was used to map underbody total pressures in one cross-flow plane downstream of the rear axle for three of these vehicles. The results link drag reduction due to various technologies with specific changes in vehicle surface, rear underbody and wake pressures, and provide a database for numerical studies. In particular, the results suggest that existing or idealized prototype technologies such as active grille shutters, sealing the external grille and ride height control reduce drag by redirecting incoming flow from the engine bay or underbody region to smoother surfaces above and around the vehicle. This mechanism can enhance the reduction in wheel drag due to reduced wheel exposure at lowered ride height. Sealing the external grille was found to redirect the flow more efficiently than closing the grille shutters, and resulted in greater drag reduction. Underbody treatments were also found in some cases to redistribute the flow around the vehicle to reduce pressure drag in addition to underbody friction drag. The magnitude and spatial extent of the measured pressure changes due to the various technologies were often consistent with the amount of drag reduction.
de Souza, Fenella, Raeesi, Arash, Belzile, Marc, Caffrey, Cheryl, Schmitt, Andreas
Porsche's 911: Not slippery when wet19AUTP04_144/1/2019
Porsche has provided detail on its new Wet Mode technology for its latest, eighth-generation (aka 992-series) 911 coupe. The assistance system, which “listens” for potential wet road danger indicators, has been developed to detect significant wet conditions and deliver a solution for increased driving stability. Described as a “world first” it is a contribution to safety, and something that drivers of early air-cooled 911s (which could present very rapid oversteer situations) would have welcomed with relief. Unlike some overly enthusiastic ESC systems that can become intrusive-taking the edge off the true dynamic capabilities of a chassis and dulling driver enjoyment-Porsche has undertaken to achieve a “grown-up” solution that supports the driver but doesn't become intrusively dominant.
Birch, Stuart
Nissan concept sport sedan is all-electric, driver-optional19AUTP03_123/1/2019
Nissan looks to pump up the fun factor with the IMs, an all-electric sports sedan concept with autonomous driving capability. The car made its global debut at the 2019 North American International Auto Show. “While still being a driver's car, this concept lives within our very graspable future of creating/engineering a thrilling autonomous ride, bringing the car into the realm of ‘entertainment’, Giovanny Arroba, Nissan's program design director, told Automotive Engineering. IMs features dual electric motors in the front and the rear with an estimated 483 hp (360 kW) and 590 lb·ft (800 N·m) for all wheel drive capability. The 115 kWh battery pack, packaged under the floor, provides an estimated 380-mi (611.5-km) driving range. The sedan's dedicated EV platform essentially mirrors that of Nissan's IMx KURO electric crossover concept that debuted at the Tokyo Motor Show in 2017.
Buchholz, Kami
On the Aerodynamics of an Enclosed-Wheel Racing Car: An Assessment and Proposal of Add-On Devices for a Fourth, High-Performance Configuration of the DrivAer Model2018-01-07254/3/2018
A modern benchmark for passenger cars - DrivAer model - has provided significant contributions to aerodynamics-related topics in automotive engineering, where three categories of passenger cars have been successfully represented. However, a reference model for high-performance car configurations has not been considered appropriately yet. Technical knowledge in motorsport is also restricted due to competitiveness in performance, reputation and commercial gains. The consequence is a shortage of open-access material to be used as technical references for either motorsport community or academic research purposes. In this paper, a parametric assessment of race car aerodynamic devices are presented into four groups of studies. These are: (i) forebody strakes (dive planes), (ii) front bumper splitter, (iii) rear-end spoiler, and (iv) underbody diffuser. The simplified design of these add-ons focuses on the main parameters (such as length, position, or incidence), leading to easier manufacturing for experiments and implementation in computational studies. Consequently, a proposed model aims to address enclosed-wheel racing car categories, adapting a simplified, 35% scaled-model DrivAer Fastback shape (i.e. smooth underbody, no wheels, and with side mirrors). Experimental data were obtained at the 8 ft x 6 ft Cranfield Wind Tunnel using an internal balance for force and moment measurements. The aerodynamic performance of each group of add-on was assessed individually in a range of ride heights over a moving belt. All cases represent the vehicle at a zero-yaw condition, Reynolds number (car length-based) of 4.2 × 106 and Mach number equal to 0.12. The proposed high-performance configuration (DrivAer hp-F) was tested and a respective Reynolds number dependency study is also provided. In line with the open-access concept of the DrivAer model, the CAD geometry and experimental data will be made available online to the international community to support independent studies.
Soares, Renan Francisco, Knowles, Andrew, Goñalons Olives, Sergio, Garry, Kevin, Holt, Jennifer
Numerical Three-Dimensional Study of an Open Wheel Race Car Undertray2018-01-07234/3/2018
An Undertray is an aerodynamic downforce generator used in racing cars to enhance traction. It has the highest downforce to drag ratio among other aerodynamic devices. The objective of this study is to optimize the performance of a FSAE undertray through full vehicle three-dimensional numerical experiments. Based on Preliminary experiments, the basic undertray features are chosen. A simple sequential analysis approach is taken to study the downforce trends versus the variation of three undertray geometrical parameters. It is found that downforce generated is proportional to the diffuser angle until breakdown caused by separation of flow in the lower diffuser duct. A secondary diffuser guide vane is found to retard said separation, allowing uniform expansion at higher diffuser angles. Lower ground clearances cause boundary layer chocking and advanced separation. Finally the effect of the undertray on the aerodynamic wings is studied, and found to be negligible.
Abdel Hady, Nouran
Aerodynamic Investigation of Cooling Drag of a Production Pickup Truck Part 1: Test Results2018-01-07404/3/2018
The airflow that enters the front grille of a ground vehicle for the purpose of component cooling has a significant effect on aerodynamic drag. This drag component is commonly referred to as cooling drag, which denotes the difference in drag measured between open grille and closed grille conditions. When the front grille is closed, the airflow that would have entered the front grille is redirected around the body. This airflow is commonly referred to as cooling interference airflow. Consequently, cooling interference airflow can lead to differences in vehicle component drag; this component of cooling drag is known as cooling interference drag. One mechanism that has been commonly utilized to directly influence the cooling drag, by reducing the engine airflow, is active grille shutters (AGS). For certain driving conditions, the AGS system can restrict airflow from passing through the heat exchangers, which significantly reduces cooling drag. The difference in drag between the AGS vanes being open and closed is referred to as AGS drag. Another vehicle component that influences the cooling drag is chin spoilers. Chin spoilers are components that lie within cooling interference airflow paths for many vehicles and can be used/designed to affect cooling drag. This study focuses on the influence of the chin spoiler on cooling and AGS drag of a production-level F-150 in a wind tunnel test environment. The chin spoiler variables tested were height and curvature (sweep). All experiments were conducted in both stationary and moving ground wind tunnel conditions at 80 MPH between yaw angles of ±7°. In addition to overall vehicle drag coefficients, surface pressures at discrete locations and cooling pack airflow rates were measured to provide better insight into the internal and external airflow behavior. Ground and yaw conditions were shown to heavily influence chin spoiler design. Cooling and AGS drag were also strongly influenced by chin spoiler face height at 0° yaw; at higher angles of yaw this influence was lessened but was still present. Chin spoiler sweep was shown to have a significantly lesser (though non-negligible) impact than chin spoiler face height on all metrics in all conditions.
Larson, Levon, Woodiga, Sudesh
An Extensive Validation of an Open Source Based Solution for Automobile External Aerodynamics2017-01-15243/28/2017
The number of computational fluid dynamics (CFD) simulations performed during the vehicle aerodynamic development process continues to expand at a rapid rate. One key contributor to this trend is the number of analytically based designed experiments performed to support vehicle aerodynamic shape development. A second contributor is the number of aerodynamic optimization studies performed for vehicle exterior components such as mirrors, underbody shields, spoilers, etc. A third contributor is the increasing number of “what if” exploratory studies performed early in the design process when the design is relatively fluid. Licensing costs for commercial CFD solutions can become a significant constraint as the number of simulations expands. A number of alternative products (e.g., independently developed, supported and documented forks of the popular open-source OpenFOAM® toolbox [1]) have become available in recent years, offering a lower cost alternative to traditional commercial CFD products. This paper summarizes results from a broad and deep evaluation of the capability of iconCFD® to substitute for the more traditional commercial CFD solutions currently used to support vehicle aerodynamic development early in the program development cycle. Included in this study were detailed B-car, sedan, SUV and truck shapes as well as multiple variants of each shape. The study investigated both static and moving ground boundary conditions as well as alternative turbulence models. Trends of the predicted aerodynamic drag coefficients (Cd) are compared against experimental data. Both transient and steady state simulation ranking accuracy of total vehicle Cd were found to be equivalent to that historically observed with more traditional commercial solver results. A consistent upward bias in absolute Cd values was observed in the transient results.
Lietz, Robert, Larson, Levon, Bachant, Peter, Goldstein, John, Silveira, Rafael, Shademan, Mehrdad, Ireland, Pete, Mooney, Kyle
Effects of Active Aerodynamic Wings on Handling Performance of High-Speed Vehicles2017-01-15923/28/2017
In this research, active aerodynamic wings are investigated using numerical simulation in order to improve vehicle handling performance under emergency scenarios, such as tight cornering maneuvers at high speeds. Air foils are selected and analyzed to determine the basic geometric features of aerodynamic wings. Built upon the airfoil analysis, the 3-D aerodynamic wing model is developed. Then, the virtual aerodynamic wings are assembled with the 3-D vehicle model. The resulting 3-D geometry model is used for aerodynamic analysis based on numerical simulation using a computational fluid dynamics (CFD) software package. The CFD-based simulation data and the vehicle dynamic model generated are combined to study the effects of active aerodynamic wings on handling performance of high-speed vehicles. The systematic numerical simulation method and achieved results may provide design guidance for the development of active aerodynamic wings for high-speed road vehicles.
Cai, Jingdong, Kapoor, Saurabh, Sikder, Tushita, He, Yuping
Validation of Aerodynamic Simulation and Wind Tunnel Test of the New Buick Excelle GT2017-01-15123/28/2017
The validation of vehicle aerodynamic simulation results to wind tunnel test results and simulation accuracy improvement attract considerable attention of many automotive manufacturers. In order to improve the simulation accuracy, a simulation model of the ground effects simulation system of the aerodynamic wind tunnel of the Shanghai Automotive Wind Tunnel Center was built. The model includes the scoop, the distributed suction, the tangential blowing, the moving belt and the wheel belts. The simulated boundary layer profile and the pressure distribution agree well with test results. The baseline model and multiple design changes of the new Buick Excelle GT are simulated. The simulation results agree very well with test results.
Wang, Fuliang, Yin, Zhangshun, Yan, Shi, Zhan, Jia, Friz, Heinz, Li, Bo, Xie, Weiliang
Aerodynamic Analysis of Grand Prix Cars Operating in Wake Flows2017-01-15463/28/2017
The effect of the upstream wake of a Formula 1 car on a following vehicle has been investigated using experimental and computational methods. Multiple vehicle studies in conventional length wind tunnels pose challenges in achieving a realistic vehicle separation and the use of a short axial length wake generator provides an advantage here. Aerodynamic downforce and drag were seen to reduce, with greater force reductions experienced at shorter axial spacings. With lateral offsets, downforce recovers at a greater rate than drag, returning to the level for a vehicle in isolation for offsets greater than half a car width. The effect of the wake was investigated in CFD using multiple vehicle simulations and non-uniform inlet boundary conditions to recreate the wake. Results closely matched those for a full two-vehicle simulation provided the inlet condition included unsteady components of the onset wake. Creating a nonuniform inlet condition allowed the wake parameters to be modified to test sensitivity to different wake features. Dynamic pressure deficit in the wake is shown to have the greatest impact on the following vehicle, reducing loading on the downforce producing surfaces. Wake up-wash and vortex flows are shown to have a smaller effect on downforce generated by the following car, but have an important role in diverting the dynamic pressure deficit upwards and over the following car. Future regulation changes, aimed at reducing the downforce loss experienced when following another car, should aim to reduce the velocity deficit onset to the following car; either by reducing wheel and underbody wakes, or by extracting the wake using up-wash from the rear wing.
Newbon, Joshua, Sims-Williams, David, Dominy, Robert
Evaluation of the Aerodynamics of Drag Reduction Technologies for Light-duty Vehicles: a Comprehensive Wind Tunnel Study2016-01-16134/5/2016
In a campaign to quantify the aerodynamic drag changes associated with drag reduction technologies recently introduced for light-duty vehicles, a 3-year, 24-vehicle study was commissioned by Transport Canada. The intent was to evaluate the level of drag reduction associated with each technology as a function of vehicle size class. Drag reduction technologies were evaluated through direct measurements of their aerodynamic performance on full-scale vehicles in the National Research Council Canada (NRC) 9 m Wind Tunnel, which is equipped with a the Ground Effect Simulation System (GESS) composed of a moving belt, wheel rollers and a boundary layer suction system. A total of 24 vehicles equipped with drag reduction technologies were evaluated over three wind tunnel entries, beginning in early 2014 to summer 2015. Testing included 12 sedans, 8 sport utility vehicles, 2 minivans and 2 pick-up trucks. Two categories of drag reduction technologies were evaluated: i) those currently offered by the original equipment manufacturers (i.e. active grille shutters, partial underbody covers, bumper and wheel air dams); and, ii) emerging technologies that have market introduction potential, i.e., active ride height control, actively deployable bumper air dams and full under-body covers. The main findings of the experiments are presented in this paper by categories of vehicles and drag reduction technologies. A discussion on the use of wind averaged drag to evaluate the full impact of the technologies on fuel consumption is also presented.
Larose, Guy, Belluz, Leanna, Whittal, Ian, Belzile, Marc, Klomp, Ryan, Schmitt, Andreas
Integrated Aero-Thermal Testing of a Race Car in a Full Scale Climatic Wind Tunnel2016-01-15884/5/2016
Wind tunnels with integrated aerodynamic and thermodynamic testing with yaw capabilities are not common. In this study however, an integrated aerodynamic and thermodynamic testing system with yaw capabilities is developed and applied in the climatic wind tunnel at the University of Ontario-Institute of Technology (UOIT). This was done by installing an incremental force measuring system (FMS) on the large turntable that features a chassis dynamometer. The testing system was utilized to implement an integrated aero-thermal test on a full-scale race car. An efficient testing protocol was developed to streamline the integrated testing process. The FMS was used to enhance the test car’s stability, cornering speed, and fuel efficiency by using aerodynamic devices. These objectives were achieved by installing a high rear wing to increase the rear downforce, a modified front splitter extension to produce a front downforce gain, and front canards to contribute to drag reduction. In addition, a thermodynamic test was conducted to study the effect of yaw on upperbody and underbody temperature distribution during the car’s operational condition. Temperature analysis from this test revealed that radiator performance was jeopardized in yaw. It also showed that some aerodynamic devices (such as a rear diffuser) can contribute negatively to the underbody cooling performance of the car. The implications of this study demonstrate that the climatic wind tunnel at UOIT is a viable tool for integrated motorsport testing, which can be used to achieve a significant competitive advantage.
Abdel-Rahman, Abdalla, Agelin-Chaab, Martin, Elfstrom, Gary, Komar, John
Optimization of Modified Car Body Using Mesh Morphing Techniques in CFD2016-01-00094/5/2016
Today's strict fuel economy requirement produces the need for the cars to have really optimized shapes among other characteristics as optimized cooling packages, reduced weight, to name a few. With the advances in automotive technology, tight global oil resources, lightweight automotive design process becomes a problem deserving important consideration. It is not however always clear how to modify the shape of the exterior of a car in order to minimize its aerodynamic resistance. Air motion is complex and operates differently at different weather conditions. Air motion around a vehicle has been studied quite exhaustively, but due to immense complex nature of air flow, which differs with different velocity, the nature of air, direction of flow et cetera, there is no complete study of aerodynamic analysis for a car. Something always can be done to further optimize the air flow around a car body. Computational Fluid Dynamics (CFD) solvers can be partnered with optimization software which guide model design changes and evaluate the corresponding results. Design changes can be executed by modifying a parameterized geometry or using mesh morphing techniques. In the present paper, ANSYS Fluent will be used in conjunction with the optimization software ANSYS DesignXplorer to study ways of reducing drag and lift for a car body. The body in question in this study is the Ahmed body[1] which has been used numerous times for CFD code validation. This geometry represents a road legal car which is used to study the effect of different forces like, aerodynamic drag force, lift force, and some other major forces which affect a car’s motion significantly. However, after thorough research and application, it has been concluded that a rear spoiler is always beneficial for fast cars, since the car tends to be much stable aerodynamically after the application of the spoiler. However, different angle of the spoiler reacts differently to different air flow conditions. We have modified the Ahmed body by making a few design changes and attaching a Clark-Y foil. Accurate prediction of its aerodynamic performance often requires very accurate and computationally expensive calculations. Optimization of the design will be achieved by using reduced resources, by analyzing how air at different velocity affect the body and what changes might be necessary for a further optimized performance. This paper will demonstrate that optimization can be performed with limited resources relying on information about drag deltas rather than absolute values. Keeping limiting resources in mind, a grid independence study wasn’t done.
Bakshi, Soham, Jawad, Badih, Arslan, Selin, Liu, Liping, Yee, Kingman
Lighter, more powerful 2016 Honda Pilot15AUTP10_0210/1/2015
The third-generation SUV gets a sleek new look and plenty of slick technology for enhanced performance and safety. Programs for new re-engineered vehicles pose a great challenge for the engineers and other professionals assigned to them: load the vehicle with more advanced technology, consumer-friendly amenities, and safety features required to meet stringent requirements, all while trimming weight from any area necessary to maintain-or ideally decrease-overall weight compared to the previous generation. The 2016 Honda Pilot development team, faced with said challenge, succeeded brilliantly. The new three-row SUV is 289 lb (131 kg) lighter-the previous Pilot Touring weighed 4632 lb (2101 kg) vs. the new Pilot Elite, which includes more features but weighs 4343 lb (1970 kg)-while recently earning a 2015 Top Safety Pick+ rating from the Insurance Institute for Highway Safety (IIHS).
Gehm, Ryan
On the Development of a Fully Automated Numerical Methodology to Improve Vehicle’s Aerodynamics Optimizing its External Shape2015-36-01979/22/2015
Car manufacturers have a growing interest in developing more efficient vehicles. New technologies have emerged in different areas one of them is vehicle aerodynamics. The aerodynamic resistance, i.e., the forces generated by the air in a vehicle, has considerable influence on fuel consumption. In this paper it´s presented a computational methodology using CFD (Computational Fluid Dynamics) and optimization tool to evaluate production vehicle and indicate possible ways to reduce its drag coefficient. Efforts are concentrated on modifying the geometry of the external design, a procedure whereby vehicle´s regions of interest are chosen to be valued on a pre-set geometric range parameters, arranging a DOE (Design of Experiments) that are evaluated virtually. In a fully automated procedure, changes are made to these parameters using morphing tools and then CFD calculations are performed. Software ANSA and Star-CCM + are respectively used. Results are then evaluated according to the statistical approach of DOE indicating which regions have higher sensitivities on the drag coefficient. Full automation of the process makes it cheaper and faster. Its results become a very important information for developing a more aerodynamic vehicle and so, improving fuel economy.
Zolet, Thiago, Sanvezzo, Joel, Rosa, Samara Cunha
Harmonized Provisions for Installation of Exterior Lamps and Retro-Reflecting Devices on Road Vehicles Except MotorcyclesJ2442_201507 (Current)7/22/2015
This SAE Recommended Practice applies to road vehicles except motorcycles. It describes the commonalities of installation requirements for lighting and light signaling devices contained in the regulatory requirements and industry standards of North America, Japan, and the widely-adopted UNECE ("European") Regulations. It does not apply to installation of lighting and light signaling devices specific to special purpose vehicles, including but not limited to police, medical and other emergency or public service vehicles. This document does not carry force of law and does not replace regulatory requirements in effect at the time of application. It is subject to change to reflect additional experience, technical advances, and especially changes in government and industry documents used as references. Users of this document are advised to mind the applicable legal requirements in effect where their vehicles will be sold and registered.
International Cooperation Committee
Fluid Structure Interaction Simulations Applied to Automotive Aerodynamics2015-01-15444/14/2015
One of the passive methods to reduce drag on the unshielded underbody of a passenger road vehicle is to use a vertical deflectors commonly called air dams or chin spoilers. These deflectors reduce the flow rate through the non-streamlined underbody and thus reduce the drag caused by underbody components protruding in to the high speed underbody flow. Air dams or chin spoilers have traditionally been manufactured from hard plastics which could break upon impact with a curb or any solid object on the road. To alleviate this failure mode vehicle manufacturers are resorting to using soft plastics which deflect and deform under aerodynamic loading or when hit against a solid object without breaking in most cases. This report is on predicting the deflection of soft chin spoiler under aerodynamic loads. The aerodynamic loads deflect the chin spoiler and the deflected chin spoiler changes the fluid pressure field resulting in a drag change. This fluid structure interaction (FSI) between chin spoiler and the air around it is simulated using coupled fluid and structural solvers. The local and global flow field changes due to FSI and their effect on vehicle drag is discussed. The FSI simulation method is explained and the results compared with test data.
Patil, Sunil, Lietz, Robert, Woodiga, Sudesh, Ahn, Hojun, Larson, Levon, Gin, Ronald, Elmore, Michael, Simpson, Alexander
CFD Investigation of the Effect of the Salient Flow Features in the Wake of a Generic Open-Wheel Race Car2015-01-15394/14/2015
It is well known that in motorsport the wake from an upstream vehicle can be detrimental to the handling characteristics of a following vehicle, in particular in formulae with high levels of downforce. Previous investigations have been performed to characterize the wake from an open wheel race car and its effect on a following car, either through the use of multiple vehicles or purpose-built wake generators. This study investigates how the wake of an upstream race car impacts the aerodynamic performance of a following car in a close-following scenario. Wakes are imposed on the inlet of a CFD simulation and wake parameters (eg: velocity deficit, trailing vorticity) are directly manipulated to investigate their individual impacts on the following vehicle. The approach provides a useful alternative to the simulation of multi-vehicle cases but a better simulation could be achieved by including wake unsteadiness from the upstream vehicle. Arguably the most significant impact of a wake on the following vehicle was found to be the rearward movement of the vehicle center of pressure. Secondary flow (eg: upwash, vorticity) on a bulk scale had the beneficial impact of moving the wake up and over the following vehicle but more localized impacts could be positive or negative according to the detailed interaction with downstream vehicle features.
Newbon, Joshua, Dominy, Robert, Sims-Williams, David
Underbody Drag Reduction Study for Electric Car Using CFD Simulations2015-26-02111/14/2015
Electric cars are the future of urban mobility which have very less carbon foot print. Unlike the conventional cars which uses BIW (Body in White), some of the electric cars are made with a space frame architecture, which is light weight and suitable for low volume production. In this architecture, underbody consists of frames, battery pack, electronics housing and electric motor. Underbody drag increases due to air entrapment around these components. Aerodynamic study for baseline model using CFD simulations showed that there was a considerable air resistance due to underbody components. To reduce the underbody drag, different add-ons are used and their effect on drag is studied. A front spoiler (air dam) is used to deflect the incoming air towards sides of the car. A under hood cover for front components, trailing arm cover for trailing arm and rear bumper cover for rear components were used to reduce underbody drag. Finally it is observed that aerodynamic behavior of the car improved drastically due to these add-ons. In the current paper, results of different simulations are discussed in detail with respect to the underbody drag reduction of an electric car. Results of the CFD simulations are validated with wind tunnel measurements. Good correlation is achieved with the test results.
Gorre, Parandhamaiah, Prasad, Pln, Kumbhar, Mansinh, Kale, Gajanan, Pathapadu, Vamsi
Study on Effect of Ground Clearance on Performance of Aerodynamic Drag Reduction Devices for Passenger Vehicle Using CFD Simulations2015-26-01971/14/2015
Reducing the carbon footprint by meeting stringent emission regulations and improving the fuel efficiency has become an essential feature in 21st century product design cycle for automobiles. Aerodynamic drag affects the fuel efficiency of the vehicle considerably. Various drag reduction devices such as air dam, rim cover, spoiler and undercover etc. are added in order to reduce the drag. This paper aims at understanding the effect of ground clearance on the performance of various aerodynamic drag reduction devices like - air-dam, spoiler, wheel cover and their combinations for hatchback vehicle using Computational Fluid Dynamics (CFD). CFD has been extensively used for exploring the various design configurations and has helped in selecting the optimized aero-parts configuration based on aerodynamic performance at concept stage which has ultimately reduced the vehicle drag coefficient by 10%. CFD results have been compared with wind tunnel testing for base configurations which is having around 96 % correlation.
Kumar, Ashit, Singh, Amarjeet, Regin A, Felix
The Aerodynamics Development of the New Nissan Qashqai2014-01-05724/1/2014
This paper aims to provide a brief description on the aerodynamics development process of the new Nissan Qashqai using full-scale wind tunnel testing and Computational Fluid Dynamics simulations (CFD). Aerodynamic drag reduction ideas were developed by means of numerical simulations with confirmation of the aerodynamics properties full-scale clay models were tested in the wind tunnel. Key aerodynamic features were developed including the optimization of hood and windscreen angle, roof camber, plan view corner radius, rear combination lamp with boundary layer trip edge and a large rear spoiler with incorporated winglet. The drag contribution of the under body was reduced by optimizing deflectors and panels. The A-pillar and door mirrors were designed to reduce drag and wind noise. Furthermore, the bumper opening area was optimized to balance the airflow for engine cooling and a low cooling drag contribution. In addition, an active grille shutter was developed to limit the amount of cooling airflow into the lower bumper opening to a minimum. Overall, the attention to details has lead to a class leading drag coefficient without compromising the styling scheme. The final off-tool vehicle was tested in three different wind tunnels in order to investigate the effect of different ground simulations on the overall drag of the vehicle. Each wind tunnel had different ground simulation techniques including moving ground and rotating wheels, stationary ground with boundary layer suction and stationary ground without boundary layer treatment. The results will be discussed briefly in this paper.
Kremheller, Andreas
Effect of Unsteady Lift Force on Vehicle Dynamics in Heave and Pitch Motion2014-01-05764/1/2014
The change in the aerodynamic lift force (henceforth CL) by heave motion is discussed in this paper in order to clarify the effect of aerodynamic characteristics on the vehicle dynamic performance. We considered that phenomenon in actual car running at 160km/h and 1Hz heave frequency. Using a towing tank to change its water from the air to the working fluid to more easily observe this phenomenon. That makes possible to observe the same phenomenon with reduced velocity and small models under same Strouhal number condition. This method can be reducing vehicle speed to 3m/s (1/15 actual) and frequency to 0.2Hz (1/5 actual) in case using 40% scaled model. The results of these tests showed that unsteady CL is proportional to heave motion. These results showed the proportional relationship between unsteady CL and heave motion. The formularization of unsteady CL made it possible to introduce shape coefficients to vehicle dynamics simulations as functions of heave velocity. This makes it possible to consider the effect of unsteady CL on dynamic performance at the initial stages of the development process. In addition, unsteady CFD was conducted by means of URANS with dynamic mesh in order to study the mechanism of unsteady CL, and the predictive accuracy of the method was verified. Predictive accuracy was within 10%, making the method adequate for an understanding of qualitative phenomena. The flow visualization by this unsteady CFD method clarified that unsteady CL during heave motion was produced by the pressure change in the under-floor area. Next, the unsteady front and rear CL during vehicle vibration was obtained accurately in slow motion by towing test. These values were analyzed with a two-degree-of-freedom mass-spring-damper model to quantify the effect of unsteady CL on flat ride. Moreover, we investigate about pitch motion. Numerical simulations were conducted with the change in the initial vehicle ride height and frequency of pitch motion in order to investigate the sensitivity of unsteady CL to these parameters. These simulation results indicated that the shape coefficient αl changed significantly from Strouhal number around 1.0. In initial ride height, αl increases as the closer to the ground by ground effect. It was possible to perform introduction CL change into the vehicle motion by formulating the test results with a simple model in heave motion. it is also analyzed by CFD. This will enable us to show the possibility to study the dynamics of the early stages of vehicle development.
Kawamura, Tetsuhiro, Ogawa, Atsushi
Methodology for the Design of an Aerodynamic Package for a Formula SAE Vehicle2014-01-05964/1/2014
Recent changes to the rules regarding aerodynamics within Formula SAE, combined with faster circuits at the European FSAE events, have made the implementation of aerodynamic devices, to add down-force, a more relevant topic. As with any race series it is essential that a detailed analysis is completed to establish the costs and benefits of including an aerodynamic package on the vehicle. The aim of the work reported here was to create a methodology that would fully evaluate all aspects of the package and conclude with an estimate of the likely gain in points at a typical FSAE event. The paper limits the analysis to a front and rear wing combination, but the approach taken can be applied to more complex aerodynamic packages. An initial wind tunnel investigation of the potential flow interactions between the driver's helmet and rear wing using a multi-hole pressure probe is reported and the data used in a two-dimensional CFD calculation to provide an accurate prediction of the likely down-force from the wing package. The chosen configurations are tested in a comprehensive wind tunnel program and a map of potential setups generated. The potential aerodynamic configurations are assessed in both quasi-static and dynamic handling analysis to demonstrate the effects of aerodynamic lift, lift distribution, aerodynamic drag, and the effect of additional weight, weight distribution and height of the center of gravity. The paper includes a description of the wind tunnel model and scaling considerations and a description of the handling model and the lap simulation methods. The results shows that a simple front and rear wing combination, providing relative low down-force (1000N at 110kph on a vehicle of 280kg, including driver), gives an improvement in performance equating to a gain of approximately 40 points during the event. The largest improvements are seen during the autocross and endurance events. This gain is considered sufficient to justify the inclusion of the package on the vehicle.
Craig, Christopher, Passmore, Martin A.
Aerodynamic Structure and Development of Formula 1 Racing Car Wakes2014-01-06004/1/2014
For the modern Formula 1 racing car, the degradation in aerodynamic performance when following another car is well documented. The problem can be broken into two parts; firstly the wake flow generated by these vehicles and the subsequent interaction a following car has with this field. Previous research [1, 2 & 3] has focused upon investigating the later without completely characterizing the former. This paper seeks to address this deficiency with initial data from a newly commissioned 30% scale Formula One wind tunnel model built to the 2011 technical regulations. Experimentation was carried out in the Industrial Wind-Tunnel (IWT) at RMIT University. In the absence of a rolling road an elevated ground plane was implemented; the results obtained show good agreement with the limited published material available. Using a high frequency response, four-hole pressure probe the aft body flow was investigated at multiple downstream locations. Time-averaged velocity, turbulence and secondary flow vectors were plotted. These data were supplemented through flow visualization techniques to better understand the salient aerodynamic features. The influence of geometric changes to the aerodynamic devices upon the rear of the car (i.e. drag reduction system currently used within Formula 1) was also investigated.
Watts, Matthew, Watkins, Simon
Differences between Air-Dam Spoiler Performances in Wind Tunnel and On-Road Tests2014-01-06094/1/2014
An air-dam spoiler is commonly used to reduce aerodynamic drag in production vehicles. However, it inexplicably tends to show different performances between wind tunnel and coast-down tests. Neither the reason nor the mechanism has been clarified. We previously reported that an air-dam spoiler contributed to a change in the wake structure behind a vehicle. In this study, to clarify the mechanism, we investigated the coefficient of aerodynamic drag CD reduction effect, wake structure, and underflow under different boundary layer conditions by conducting wind tunnel tests with a rolling road system and constant speed on-road tests. We found that the air-dam spoiler changed the wake structure by deceleration of the underflow under stationary floor conditions. Accordingly, the base pressure was recovered by approximately 30% and, the CD value reduction effect was approximately 10%. The ratio of the base pressure recovery to the CD value reduction effect was approximately 90%, suggesting that the main mechanism is the base pressure recovery produced by changing the wake structure. In contrast, the air-dam spoiler did not change the wake structure in on- road tests and under moving floor conditions. Consequently, the base pressure recovery and CD value reduction effect decreased to approximately 20% and 4%, respectively, owing to the deceleration of the underflow being insufficient to change the wake structure. In other words, the boundary layer of the floor helped to decelerate the underflow and to change the wake structure under stationary floor conditions, suggesting that we overestimated the air-dam spoiler performance under stationary floor conditions.
Katoh, Daichi, Koremoto, Kensuke, Kaneko, Munetsugu, Hashizume, Yoshimitsu
CAA Application to Automobile Wind Throb Prevention Design2014-01-05934/1/2014
When a window opens to provide the occupant with fresh air flow while driving, wind throb problems may develop along with it. This work focuses on an analytical approach to address the wind throb issue for passenger vehicles when a front window or sunroof is open. The first case of this paper pertains to the front window throb issue for the current Ford Escape. Early in a program stage, CAA (Computational Aeroacoustics) analysis predicted that the wind throb level exceeded the program wind throb target. When a prototype vehicle became available, the wind tunnel test confirmed the much earlier analytical result. In an attempt to resolve this issue, the efforts focused on a design proposal to implement a wind spoiler on the side mirror sail, with the spoiler dimension only 6 millimeters in height. This work showed that the full vehicle CAA analysis could capture the impact of this tiny geometry variation on the wind throb level inside the vehicle cabin. The independent wind tunnel effort came to the same conclusion, and the difference between the analysis and testing is only about 1 dB. With the implementation of this spoiler, the program target was finally met. The second case of this paper deals with the sunroof throb issue for an SUV. The work concentrates on the modeling method of wind deflectors made of meshed fabric material and carrying out CAA analysis to access the sunroof wind throb level. The result shows that CAA can predict very well the impact of the wind deflector made of meshed fabric material on the wind throb level, in line with the subjective evaluation on proving ground. In summary, this work manifests that CAA is a very effective tool for wind throb prevention design when hardware prototypes are not available.
Hou, Hangsheng
DESIGNING FOR DOWNFORCE14AUTP02_012/4/2014
Airflow is paramount for performance vehicles, which require aerodynamic enhancements to promote high-speed stability and greater cornering capability. Aerodynamics currently is a hot topic for the transportation sector, from passenger vehicles all the way to Class 8 trucks. Along with advanced powertrain technologies and lightweight materials, aerodynamics is an area receiving considerable engineering attention due to its potential for improving vehicle fuel efficiency-a major goal as stricter regulations loom for cars and light-duty trucks as well as medium- and heavy-duty vehicles. But for cars that easily surpass the 100-mph (161-km/h) mark and feel as at home on the racetrack as on the road, airflow takes on added significance. Their speed potential must be complemented with the appropriate aerodynamic solutions to keep such cars safely and firmly planted to the driving surface at high speeds.
Gehm, Ryan
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