Browse Topic: Vehicle roofs

Items (41)
Surface Flow Visualization on a Full-Scale Passenger Car with Quantitative Tuft Image Processing2016-01-15824/5/2016
Flow visualization techniques are widely used in aerodynamics to investigate the surface trace pattern. In this experimental investigation, the surface flow pattern over the rear end of a full-scale passenger car is studied using tufts. The movement of the tufts is recorded with a DSLR still camera, which continuously takes pictures. A novel and efficient tuft image processing algorithm has been developed to extract the tuft orientations in each image. This allows the extraction of the mean tuft angle and other such statistics. From the extracted tuft angles, streamline plots are created to identify points of interest, such as saddle points as well as separation and reattachment lines. Furthermore, the information about the tuft orientation in each time step allows studying steady and unsteady flow phenomena. Hence, the tuft image processing algorithm provides more detailed information about the surface flow than the traditional tuft method. The main advantages over other flow visualization methods, such as oil paint, is that experimental facilities are not contaminated and statistical data can be extracted. The investigated surface pattern shows a symmetric flow on the entire rear end section of the passenger car. The flow field on the roof, backlight, and upper trunk deck is attached almost everywhere. However, two small regions indicate the presence of two counter-rotating vortices at the lower edge of the backlight (rear window). Those vortices are also detectable in the distribution of the tuft angle standard deviation. A bifurcation line is present at each side of the trunk due to the streamwise vortices originating at the C-pillars. The tuft streamlines created with this novel tuft method are compared to a standard oil paint flow visualization to validate the calculated tuft flow pattern. A critical comparison between the methods confirms that the flow tuft analysis algorithm functions flawlessly as a highly detailed flow analysis tool without the mess of oil paint.
Wieser, DirkBonitz, SabineLofdahl, LennartBroniewicz, AlexanderNayeri, ChristianPaschereit, ChristianLarsson, Lars
SUV Solar Roof with Photo-Thermal Effect for Ventilation ORC System2016-01-02404/5/2016
The Organic Rankine Cycle System (ORC) is an effective means to use the solar energy. The system adopts the solar energy on the car roof as the heat source to make the ORC work and drive the thermoelectric air-conditioner. It can improve the entering comfort on the parking condition and the vehicle energy utilization efficiency. In this research, the system comprehensively applied the principle of sunshine concentration, heat collection and photo electricity. Then considering the working condition and performance features of ORC system, the car roof was designed to have a compact structure, through which the efficiency of the solar vehicle system could be improved. Firstly, the research analyzed the heat source temperature and the heat flux impact on the output power of the ORC system. After that, the performance of heat collection was identified according to the given thermoelectric air-condition’s power requirements. After building the model of three kinds of solar collectors, through the analysis and frequency division utilization of it, the basic requirements about stable output power by the solar energy could meet on the condition of different illumination. By the research and analysis, the ORC system could run normally and the output power was changed by sunlight’s condition with a certain scope of illuminance and a certain incident angle. Besides, the use of roof’s solar power could supply energy for a part of vehicle’s electric system and reduce energy consumption.
Zhan, RuobingTan, GangfengYang, BoZhang, ZhiweiWang, TieLiu, CenyiWu, XintongRen, YanjunXu, Haobo
Numerical and Experimental Study of Sound Power Reduction Performance of Acoustic Black Holes in Rectangular Plates2015-01-22706/15/2015
Global attenuation of structural velocities is one of the most effective approaches in order to reduce noise emitted by shell structures such as a car roof or aircraft fuselage panels. This global reduction can be achieved by the application of passive damping treatments like constraint layer damping on large fractions of the vibrating surface. The main disadvantage of this approach arises from the fact that it leads to increasing total cost and weight of the structure. To overcome this problem, acoustic black holes can be used to create locations with high vibration amplitudes and low bending waves velocity in order to dissipate the energy of structure borne sound by very limited application of damping treatments. Acoustic black holes are funnel shaped thickness reductions that attract sound radiating bending waves and allow a global vibration reduction by an acceptable use of additional damping. This paper presents the results of a numerical and experimental study of acoustic black holes located on a rectangular plate. The presented work is focused on the influence of size, position and number of acoustic black holes on the acoustic performance. A large number of different configurations of these parameters is studied by finite-element-analysis and evaluated in terms of vibration amplitude and sound power level. In order to confirm simulation results the most efficient configuration is implemented in laboratory setup and characterized in terms of vibrational and acoustic performance.
Unruh, OliverBlech, ChristopherMonner, Hans Peter
Assessment of Broadband Noise Generated by a Vehicle Sunroof at Different Flow Conditions using a Digital Wind Tunnel2015-01-23216/15/2015
For the automotive industry, the quality and level of the wind noise contribution has a growing importance and therefore should be addressed as early as possible in the development process. Each component of the vehicle is designed to meet its individual noise target to ensure the wind noise passenger comfort level inside the vehicle is met. Sunroof broadband noise is generated by the turbulent flow developed over the roof opening. A strong shear layer and vortices impacting on the trailing edge of the sunroof are typical mechanisms related to the noise production. Sunroof designs are tested to meet broadband noise targets. Experimentally testing designs and making changes to meet these design targets typically involves high cost prototypes, expensive wind tunnel sessions and potentially late design changes. To reduce the associated costs as well as development times, there is strong motivation for the use of a reliable numerical prediction capability early in the vehicle design process. Previous investigations have shown the possibility to use transient CFD/CAA simulations based on Lattice Boltzmann Methods to assess the wind noise performance of mirrors, wipers, underbody designs and buffeting performance of sunroofs and open side windows. This paper presents the use of this computational approach on two production vehicles to assess the broadband noise generated by a fully open sunroof. Computational predictions of mesh deflectors as well as yaw effect were validated against wind tunnel measurements. Also, detailed flow analysis was performed to understand the noise generation mechanisms and to explain the effect of the mesh deflector and flow yaw angle on the interior noise. Accurate prediction of the wind noise performance of the sunroof and the insight provided by the flow analysis proves that this computational approach can be used to make design decisions during the vehicle development process.
Oettle, NicholasBissell, AndrewSenthooran, SivapalanMeskine, Mohammed
ABSTRACT Inspired watching Glenn Curtiss landing to refuel on his historic 1910 flight from Albany to New York City, the almost 5-year old John McDonald "Johnny" Miller decided he wanted to be a pilot, a decision reinforced five years later in a chance encounter with famed aviatrix Ruth Law (3rd licensed woman pilot in America) at the Curtiss Flying school in Mineola, Long Island. Miller taught himself to fly in used WWI Jenny from a text by Captain Horatio Barber, a book Miller still had in his family home in Poughkeepsie, NY eighty years later. His career in aviation, begun in a $1,500 used WWI aircraft, would span eight decades and see him as an Eastern Airline pilot flying jets - a career captured in his email address adopted in his ninth decade from jennys2jets, but Miller was most famous for being the man who beat Amelia Earhart in the first transcontinental Autogiro flight in 1931 and the 1939-1940 experimental Autogiro Airmail Route between the 30th Street Post Office roof in Philadelphia and Camden, NJ. In between, Miller supported himself with maintenance work on bootleggers airplanes and airshow performances, one of which resulted in the death of 'Al' Wilson whose replica Curtiss biplane fatally crashed in a mock dogfight with Miller's PCA-2 Autogiro. Miller's career spanned 85 years and, at his death at 102 & 1/2, he was still a licensed and active pilot. He had thrilled thousands with his Autogiro exhibitions, and while he was not the first, his daring Autogiro 'loop-the-loop' never failed to have the crowd cheering and was captured in the 1935 film Ladies Crave Excitement. Miller was an outsider - not part of the Pitcairn business enterprise which championed Earhart and, from such a truly unique vantage point, was in a special position to observe and comment. His triumphant transcontinental flight in 1931 and the 1939-1940 Autogiro Airmail Route neatly bracket the age of the American Autogiro - John McDonald Miller was part that decade, and his frequent writings provide a unique record and attest to the fabulous life of this American original.
Charnov, Bruce
FEA Development of Spot Weld Modeling with Fracture Forming Limit Diagram(FFLD) Failure Criteria and Its Application to Vehicle Body Structure2015-01-13164/14/2015
Spot weld separation in vehicle development stage is one of the critical phenomena in structural analyses regarding quasi-static test condition, like roof strength or seat/belt pull. It directly reduces structural performance by losing connected load path and occasionally introduces tearing on surrounding sheet metals. Traditionally many efforts have been attempted to capture parent metal ductile fracture, but not applied to spot weld separations in automotive FEA simulations. [1,2,3] This paper introduces how to develop FFLD failure criteria from a series of parametric study on ultra high strength sheet steel and deals with failure criteria around spot weld and parent metal. Once the fracture strains for sheet steels are determined, those developed values were applied to traditional spot weld coupon FEA simulations and tests. Full vehicle level roof strength FEA simulations on a typical automotive body structure were performed and verified to the physical tests. Developed FFLD curves have been used for both spot weld and parent metal and good correlations have been achieved. Various mesh patterns and sizes around spot welds have been investigated. Finally, an optimized weld pattern and mesh size have been suggested for quasi static load cases and successfully applied to vehicle body structures.
Lee, HwawonPolice, ParvathKoch, LisaKomarivelli, RajmouliWillis, Brice
A City Bus Electrification Supported by the Photovoltaic Power Modules2014-01-289810/13/2014
This paper examines the possible electric energy collected by the photovoltaic (PV) modules installed on the roof of the bus. The tests were carried out for Mercedes Conecto LF12 buses equipped with CI engine meeting the standards of Euro 5. The research was conducted in the urban contexts/operation. Detailed results of the measurements such as fuel consumption, electric energy consumption, engine speed and vehicle speed are shown. Additional measurements included: the quantity of solar energy coming from the roof of the moving vehicle and electric energy generated from the photovoltaic modules installed. The study was conducted on a city bus taking different routes in the city of Lublin in Eastern Poland. The research bus was supplied with photovoltaic modules and a measurement system. The test results enabled to determine the ratio of the amount of electric energy acquired through the photovoltaic modules mounted on a bus to equivalent amount of energy acquired by a non-shaded photovoltaic system arranged horizontally on the roof of the building. The engine idle speed percentage distribution within the urban operation was specified to the value of 45%.The Photovoltaic system mounted on a bus on average produces 17.6% less energy compared to an identical stationary system. The PV system could provide 26% of the annual demand for electric energy of a city bus. Thus it may save reduce fuel-associated operation costs by 3% per year, as a result of generating up to 26% electric energy from free solar power rather than depending on fuel combustion.
Geca, MichalWendeker, MiroslawGrabowski, Lukasz
Integrated CAE Methods for Perceived Quality Assurance of Vehicle Outer Panels2014-01-03664/1/2014
Oil canning and initial stiffness of the automotive roofs and panels are considered to be sensitive customer ‘perceived quality’ issues. In an effort to develop more accurate objective requirements, respective simulation methods are continuously being developed throughout automotive industries. This paper discusses a latest development on oil canning predictions using LS-DYNA® Implicit, including BNDOUT request, MORTAR contact option and with the stamping process involved, which resulted in excellent correlations especially when it comes to measurements at immediate locations to the feature lines of the vehicle outer panels. Furthermore, in pursuit of light-weighting vehicles with thinner roofs, a new CAE method was recently developed to simulate severe noise conditions exhibited on some of developmental properties while going through a car wash. This paper introduces such a method to discuss Fluid Structure Interaction (FSI) approach using an Arbitrary Lagrangian Eulerian (ALE) formulation in LS-DYNA® for vehicle roof car wash boom noise prediction. This CAE method was developed to simulate force behavior from airflow as the car wash air blowers are expelling high speed air at the vehicle roofs during car wash. LS-DYNA® was proven an appropriate tool to precisely simulate popping noises by creating instantaneous local instabilities - recoverable/non-recoverable - and continuous fluttering of the roof. This paper additionally briefs the history of oil canning CAE method developments from inaccurate hand push evaluation to approaches using MSC Nastran® to Abaqus/Standard®, and then the final evolution to LS-DYNA® Implicit to provide optimized vehicle solutions.
Jang, Jaehyuk
Fuel Economy and Emissions Effects of Low Tire Pressure, Open Windows, Roof Top and Hitch-Mounted Cargo, and Trailer2014-01-16144/1/2014
To quantify the fuel economy (FE) effect of some common vehicle accessories or alterations, a compact passenger sedan and a sport utility vehicle (SUV) were subjected to SAE J2263 coastdown procedures. Coastdowns were conducted with low tire pressure, all windows open, with a roof top or hitch-mounted cargo carrier, and with the SUV pulling an enclosed cargo trailer. From these coastdowns, vehicle dynamometer coefficients were developed which enabled the execution of vehicle dynamometer experiments to determine the effect of these changes on vehicle FE and emissions over standard drive cycles and at steady highway speeds. In addition, two minivans were subjected to coastdowns to examine the similarity in derived coefficients for two duplicate vehicles of the same model. The FE penalty associated with the rooftop cargo box mounted on the compact sedan was as high as 25-27% at higher speeds, where the aerodynamic drag is most pronounced. For both vehicles, use of a hitch mounted cargo tray carrying a similar load resulted in very small FE penalties, unlike the rooftop cargo box. The results for the SUV pulling a 3500 pound enclosed cargo trailer were rather dramatic, resulting in FE penalties ranging from 30%, for the city cycle, to 50% at 80 mph, at which point significant CO generation indicated protective enrichment due to high load. Low tire pressure cases resulted in negligible to 10% FE penalty depending on the specific case and test point. Driving with all four windows open decreased FE by 4-8.5% for the compact sedan, and 1-4% for the SUV.
Thomas, JohnHuff, SheanWest, Brian
Analysis of Damage Caused to Vehicle Body Panels by Impacting Hail and Various Tools and Objects2013-01-14384/8/2013
On the 25th December 2011 there was a hail storm in the state of Victoria, Australia, which caused approximately AU$712 million worth of damage. Some of this damage was caused to passenger vehicles. The authors conducted a number of inspections of hail-damaged vehicles as a result of insurance claims being disputed or rejected on the basis that some, or all, of the alleged hail damage was not created by hail but instead created intentionally by the vehicles' owners with the use of different tools and/or objects. As a result of the inspections and investigations of potentially fraudulent claims, the authors conducted a total of 119 tests designed to replicate damage caused to vehicle body panels by impacting hail and to recreate claimed hail damage by using tools and other objects. To do so, the authors created two sizes of hail: Ø20 mm and Ø40 mm hail. A total of 15 impact tests were conducted with Ø20 mm hail. The impact speed for the Ø20 mm hail varied between 75 km/h and 144 km/h, with the average being 113 km/h. A total of 50 impact tests were conducted with Ø40 mm hail. The impact speed for the Ø40 mm hail varied between 66 km/h and 133 km/h, with the average being 101 km/h. The testing impact speeds were generally higher than the terminal velocities of the corresponding hail, so the damage observed is expected to be an over estimation of the actual damage caused by hail. The hail was projected at the test vehicle using a purpose-built projectile launching device that used a sling-like mechanism to project hail in a horizontal direction at a test vehicle. The test vehicle was a white-colored 2001 model Holden Commodore with non-metallic paint. The body panels tested were: bonnet, roof, boot, all four doors, the vehicle pillars and cant rail. High speed cameras were used to determine the impact speed of the hail. Damage was photographed and recorded. In addition to impacting the vehicle with hail, a number of different tools and objects were used to recreate man-made damage. Tools and objects used were: claw hammer (conventional), welding hammer, ball-peen hammer, mason hammer, lead ball sink in a sock, golf ball in a sock, ratchet, breaker bar, crowbar and center punch. The conducted tests revealed the following findings: 1. hail impacting the vehicle body panels will not scratch or mark the paint but the paint may chip if hail impacts the vehicle near a fold or edge of a panel; 2. dents caused by hail will cause the light to move smoothly and continuously across the dent and the light will not "break" or crease; 3. where dents were caused by tools and objects the light will crease into multiple (two or more) distinct areas as it passes over the dent; 4. scratches and/or markings in the paint were identified on dents caused by tools and objects; 5. folds and curves on the panels did not affect the size of the dent caused to the panel; using the same tool and force to impact two different body panels (A-pillar and roof) resulted in dents that were very similar in physical appearance; 6. for the same impact speed the larger Ø40 mm hail caused more damage than the Ø20 mm hail; and 7. for the same size hail the higher impact speed hail caused more damage.
Josevski, NikolaSandvik, AndreasJones, ChrisPok, TandyOrton, TiaRichardson, Shane
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