Browse Topic: Sunroofs and moonroofs

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Impact of Sunroof Deflector on Interior Sound Quality2015-01-23246/15/2015
When a sunroof opens to let in fresh air while driving, there might be several noise issues associated with it. The most common and painful one is the wind throb issue, which is nevertheless largely resolved by implementing a sufficiently high wind deflector along the front edge of the sunroof. However, with the wind throb suppressed, other sound quality issues might emerge. The most notable one is the hissing noise issue, which becomes increasingly objectionable with the increase of vehicle speed. This work looks into the impact of sunroof deflector on interior sound quality with the consideration of wind throb, hissing noise and booming noise in terms of psychoacoustic attributes that could be felt subjectively. The goal is to achieve a better understanding of the sound quality associated with the sunroof deflector design, and inspire a balanced design, potentially targeting the most NVH demanding customers in the premium vehicle segment.
Hou, Hangsheng, Yue, Guiping
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, Nicholas, Bissell, Andrew, Senthooran, Sivapalan, Meskine, Mohammed
A Computational Approach to Assess Buffeting and Broadband Noise Generated by a Vehicle Sunroof2015-01-15324/14/2015
Car manufacturers put large efforts into reducing wind noise to improve the comfort level of their cars. 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 designs are tested to meet low-frequency buffeting (also known as boom) targets and broadband noise targets for the fully open sunroof with deflector and for the sunroof in vent position. 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. In the past, a computational approach based on a Lattice Boltzmann Method has been extensively validated for assessing 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 the Range Rover production vehicle to assess the sunroof buffeting performance with and without a mesh deflector added, which are commonly used to improve the buffeting performance. This approach was extended to assess the broadband noise generated by the deflector up and the sunroof at vent position. Computational predictions were validated against wind tunnel measurements for all these configurations. Also detailed flow analysis was performed to provide insight into the noise generation mechanisms. Accurate prediction of the wind noise performance of the sunroof and the insight provided by the flow analysis prove that this computational approach can be used to make design decisions during the vehicle development process.
Oettle, Nicholas, Meskine, Mohammed, Senthooran, Sivapalan, Bissell, Andrew, Balasubramanian, Gana, Powell, Robert
Fast and Efficient Detection of Shading of the Objects2015-01-03714/14/2015
The human thermal comfort, which has been a subject of extensive research, is a principal objective of the automotive climate control system. Applying the results of research studies to the practical problems require quantitative information of the thermal environment in the passenger compartment of a vehicle. The exposure to solar radiation is known to alter the thermal environment in the passenger compartment. A photovoltaic-cell based sensor is commonly used in the automotive climate control system to measure the solar radiation exposure of the passenger compartment of a vehicle. The erroneous information from a sensor however can cause thermal discomfort to the occupants. The erroneous measurement can be due to physical or environmental parameters. Shading of a solar sensor due to the opaque vehicle body elements is one such environmental parameter that is known to give incorrect measurement. The fundamental geometric principles of the intersection of a line segment and a plane can be used to determine if sensor is shaded, for given position of the sun with respect to a vehicle and geometry of the passenger compartment. However, realization of these principles using the fixed-point arithmetic is computationally expensive, due to their high memory and execution time requirements. The analytical method that uses relatively simple geometric relations is proposed to obtain the exact same results at significantly lower cost. The proposed method uses a constant azimuth curve to determine the range of elevation for each transparent body element of a vehicle, such as windshield, side glasses, rear glass and sun roof, for which a solar sensor is exposed to the direct-beam solar radiation. A sensor is said to be shaded if the current solar elevation angle is not included in any of the calculated ranges. The corrective action to the erroneous solar intensity while sensor is shaded, is suggested such that its influence on the thermal comfort of occupants is minimum.
Kakade, Rupesh Sonu, Mer, Prashant
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
Progress in Aeroacoustic and Climatic Wind Tunnels for Automotive Wind Noise and Acoustic Testing2013-01-13524/8/2013
There has been significant progress in developing test facilities for automotive wind noise and automotive components since the early 1990s. The test technology is critical to the development of modern vehicles, and essentially every major automotive manufacturer owns and operates their own aeroacoustic wind tunnel, or has rental access to one and conducts a significant amount of wind noise testing. The current status for climatic wind tunnels is that many new CWTs are being defined with acoustic test requirements. These test capabilities in AAWTs and CWTs will continue to enable the development of vehicles with better wind noise attributes, fewer problems with sunroof ‘booming’, and lower noise levels for HVAC and auxiliary systems. In the future, it is expected that the test demand for AAWTs and CWTs with low acoustic background noise will continue to increase as customers expect better automotive products, especially across more of the product line. The objective of this work is to present some of the progress and challenges involved in designing wind tunnels with low background noise in order to meet the requirements of automotive companies for their product development needs.
Duell, Edward G., Walter, Joel, Yen, Joseph, Nagle, Tony
Effects of Notches on Surface Pressure Fluctuations Downstream of a Leading Edge Spoiler2009-01-22385/19/2009
Notched spoilers have been observed to be more effective than uniform spoilers to suppress the flow-induced cavity resonance of vehicles with open sunroofs. In this study, a few mechanisms possibly involved in buffeting suppression from notched spoilers were investigated experimentally and numerically. One objective was to investigate the spatial coherence and phase of the wall pressure fluctuations downstream of notched spoilers in comparison with the same quantities for uniform spoilers. Another objective was to gather detailed measured data to allow the verification of computer simulations of the flow over the notched spoiler. Experiments were performed to measure the velocity and wall pressure fields downstream of spoilers mounted on the rigid floor of a closed test section wind tunnel for different spoiler heights. Efforts were made to reproduce the spoiler and wind tunnel geometry and boundary conditions of the experimental set-up in the numerical simulations. The numerical investigation used the Lattice Boltzmann Method (LBM), with the so-called Very Large Eddy Simulation (VLES) viscosity turbulence model. The results of the numerical investigation were in satisfactory agreement with measured data at low frequencies, where buffeting is expected to occur. The results clearly showed that the notches act as streamwise vortex generators. They reduced spoiler drag, resulting in an upstream shift of the flow reattachment region. The results confirmed that the streamwise vortices break down the homogeneity of the leading edge cross-stream vortices predominantly responsible for the cavity excitation. This decreased the cross-stream coherence of the surface pressure field, thereby reducing the magnitude of the net equivalent excitation force acting over the surface downstream.
Park, Jong Beom, Mongeau, Luc, Mejia, Paloma Y.
Polycarbonate Glazing: Maximum and Effective Temperatures for Outdoor Weathering Exposure in the Desert of Arizona2009-01-05734/20/2009
We define an effective temperature (Teff) as an irradiance-weighted average temperature of a material during weathering. It is the constant temperature that would give the same amount of damage as the sample sustains during natural cycling and serves as a benchmark for predicting lifetimes. It is weakly dependant on the activation energy (Ea) of the degradation process. The annual effective ambient and black panel temperatures at an Arizona test site were 30° and 42°C, respectively, for Ea = 4–7 kcal/mol. Privacy color polycarbonate minivan sunroof windows had surface Teff = 45–46°C exterior, 54–58°C interior, and 49–52°C exterior blackout surfaces. Maximum recorded temperatures were 73°C, 87°C, and 81°C, respectively.
Sargent, Jonathan R., Shuler, Stephen, Pickett, James E.
Helmholtz Resonators Acting as Sound Source in Automotive Aeroacoustics2009-01-01834/20/2009
Helmholtz-resonators are discussed in technical acoustics normally in conjunction with attenuation of sound, not with amplification or even production of sound. On the other hand everybody knows the sound produced by a bottle, when someone blows over the orifice. During the investigation of the sound produced in body gaps it was found that the underlying flow physics are closely related to the Helmholtz-resonator. But different from the typical Helmholtz-resonator generated noise – as for example the blown bottle or, from the automotive world, the sun roof buffeting – there is no fluid resonance involved in the process. For body gaps the random pressure fluctuation of the turbulent boundary layer is sufficient to excite the acoustic resonance in the cavity. The sound generation is characterized by a continuous rise in sound pressure level with increasing velocity, the rise is proportional to U with varying exponents. It will be shown that the fluid resonance is shifted to much higher velocities than one would expect from Rossiters feedback model. This is the reason that it can not be found in body gaps. Nevertheless even without fluid resonance the body gaps represent the most important noise source for modern automobiles. A vehicle is much more silent in the interior if all gaps are closed as if, for example, the wing mirrors are removed and the A-Pillar-radius is doubled. The shift of the fluid resonance to higher velocities mentioned above is associated with a reduced transport velocity for vortices over small orifices. Experimental evidence will be shown that this transport velocity is dramatically reduced for orifices buried under a thick turbulent boundary layer.
Wickern, Gerhard, Brennberger, Martin
PLM Promotes a Smart Outsourcing Model that Balances Cost with Intellectual Property Protection2008-21-004410/20/2008
Capitalism has followed cheap labor since before the Industrial Revolution. However, high-skilled work like programming and engineering has recently begun traveling to low-cost nations, and as a result, the eternal challenge of balancing cost and risk has even more serious consequences. The new outsourcing models that help companies stay cost-competitive in the short run, may hurt them in the long run by creating competitors who adapt or outright steal their intellectual property. This paper outlines how product lifecycle management (PLM) solutions can be used to outsource engineering without sacrificing cost controls, intellectual property integrity, or in-house engineering talent. It describes collaboration models built around advanced design technology that inject efficiency into engineering processes at every level, enabling companies to balance short and long term concerns.
Brincheck, Bob
Overview of a Study on Direction-of-Motion Stereotype Strengths for Automobile Controls9101152/1/1991
Virginia Polytechnic Institute and State University recently conducted an SAE sponsored research study investigating directional stereotypes of six types of automobile controls: power mirrors, power windows, manual windows, stalks, generic controls, and power door locks. The objective was to determine stereotype strength and the reasons for the strengths. Two hundred subjects participated in this study. This paper provides an overview of the results of the study and recommendations made therefrom.
Wierwille, Walter W., McFarlane, John
Sunroofs and the Cooling Loads of Automobile Air Conditioners8700312/1/1987
Thermal characteristics of sunroof of automobile are discussed. Its impact on the transient temperature responses of the vehicle when exposed to the solar radiation is studied. The effect of the sunroof on the cooling load demands of the automobile is presented. The acceptance of sunroofs by the car buyers seems to have risen in the last several years. More advanced study on the sunroof and its impact on the automobile heating and cooling systems are needed.
Chiou, J. P.
MULTI-PURPOSE BODIES - FROM PLUSH PICKUPS TO PINT-SIZED PULLMANS5900861/1/1959
KOEHLER, WALTER O.
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