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Wind Tunnel Test to Determine Pantograph Noise Contribution on a High-speed Train

Korea Railroad Research Institute-Heemin Noh
  • Technical Paper
  • 2020-01-1517
To be published on 2020-06-03 by SAE International in United States
In this study, we investigated the characteristics and the influence of the aero-acoustic noise generated from a pantograph using various experimental approaches in a wind tunnel. First, the noise generated at various flow velocities was measured and analyzed using a full-scale pantograph model. Then, the noise generated from the main position of the pantograph was derived using a microphone array attached to one side of a wind tunnel. The noise contributions of the main components of the pantograph were derived from the noise measurements obtained from a step-by-step disassembly of the full-scale model.Through this study, we have investigated the aero-acoustic noise contribution of the major components of a pantograph, and we have developed effective noise-reduction measures for the panhead collector.
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Numerical Investigation of Tonal Noise at Automotive Side Mirrors Due to Aeroacoustic Feedback

Daimler AG-Alexander Schell, Mark Eiselt
  • Technical Paper
  • 2020-01-1514
To be published on 2020-06-03 by SAE International in United States
In addition to the typical broadband noise character of wind noise, tonal noise phenomena can be much more disruptive, regardless of the overall interior noise quality of the vehicle. Whistling sounds usually occur by flow over sharp edges and resonant gaps, but can also be caused by the feedback of sound waves with laminar boundary layers or separation bubbles and the resulting frequency-selective growth of boundary layer instabilities. Such aeroacoustic feedback can e.g. occur at the side mirror of a vehicle and one compellingly needs the coupling of acoustic and flow field. A compressible large eddy simulation (LES) is in principle suitable but one has to take care of any numerical artifacts which can disturb the entire acoustic field. This paper describes the possibility to resolve aeroacoustic feedback with a commercial 2nd/3rd order finite volume CFD code. A zonal RANS/LES approach is used to ensure a realistic flow around the exterior side mirror mounted at a Mercedes-Benz C-Class. The provided compressible LES are using non-reflecting boundary conditions in combination with a sponge zone approach to…
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Sound Field Synthesis by Synthetic Array (SFS-SA) for Diffuse Field or TBL Structural Excitation

SONORHC-Guillaume guyader
Saint-Gobain-Fabien Dalzin
  • Technical Paper
  • 2020-01-1522
To be published on 2020-06-03 by SAE International in United States
Diffuse field or TBL excitation of vehicles are of huge interest in automotive industry, for such excitation reveberent rooms of wind tunnels are necessary, this means high cost experiments. The idea of sound field synthesis to create the acoustic effect corresponding to diffuse field or TBL excitation is of major interest to reduce drastically the cost of experiments. Originally techniques based on Loud speakers antenna [], [], were used. However, a major difficulty appeared due to driving simultaneously a huge number of Loud speakers. To avoid this difficulty a new technique based on Synthetic antenna was proposed in reference [] , instead of an array of loud speakers , just one loud speaker is used for scanning the surface where the acoustic field excite the structure. A post processing based on plane wave decomposition, is then applied to collected data in order to get the response of the structure or the sound transmission through the structure. Different post processing can be applied to get the vibro-acoustics response of structural component due to diffuse field or…
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General Motors Full Scale Wind Tunnel Upgrade

General Motors LLC-Nina Tortosa
Jacobs Technology-Paul Nagle, Tyler Brooker
  • Technical Paper
  • 2020-01-0687
To be published on 2020-04-14 by SAE International in United States
The General Motors Aero Lab’s Full Scale Wind Tunnel Facility, which came into operation in August of 1980, has undergone the significant upgrade of installing a state-of-the-art moving ground plane system. After almost four decades of continued use the full-scale wind tunnel also received some significant maintenance to other areas, including a new heat exchanger, main fan overhaul, and replacement of the test section acoustic treatment. A 5-belt system was installed along with an integrated vehicle lift system. The center belt measures 8m long, and can accommodate two belt widths of 1100mm and 900mm. Flow quality and other wind tunnel performance parameters were maintained to prior standards which are on par with the latest industry standards. The new 5-belt rolling road system maintains GM’s industry leading vehicle aerodynamic development and the improved acoustic panels ensure GM continues to develop vehicles with leading class acoustics.
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Stability of Flowing Combustion in Adaptive Cycle Engines

Illinois Institute of Technology-Prashanth Tamilselvam, Francisco Ruiz
  • Technical Paper
  • 2020-01-0296
To be published on 2020-04-14 by SAE International in United States
In an Adaptive Cycle Engine (ACE), thermodynamics favors combustion starting while the compressed, premixed air and fuel are still flowing into the cylinder through the transfer valve. Since the flow velocity is typically high and is predicted to reach sonic conditions by the time the transfer valve closes, the flame might be subjected to extensive stretch, thus leading to aerodynamic quenching. It is also unclear whether a single spark, or even a succession of sparks, will be sufficient to achieve complete combustion. Given that the first ACE prototype is still being built, this issue is addressed by numerical simulation using the G-equation model, which accounts for the effect of flame stretching, over a 3D domain representing a flat-piston ACE cylinder, both with inward- and outward-opening valves. A k-epsilon turbulence model was used for the highly turbulent flow field. It was found that the flame would suffer local blow-off under most operating conditions, but the blow-off is never complete so that the regions affected are later re-ignited by the remaining parts of the flame, and combustion…
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Investigation of the Effect of Tire Deformation on Open-Wheel Aerodynamics

Graz University of Technology-Philipp Eder, Cornelia Lex
U.A.S. Graz-Thomas Gerstorfer, Thomas Amhofer
  • Technical Paper
  • 2020-01-0546
To be published on 2020-04-14 by SAE International in United States
This paper introduces a finite element (FE) approach to determine tire deformation and its effect on open-wheeled racecar aerodynamics. In recent literature the tire deformation was measured optically using cameras during wind tunnel testing. Combined loads like accelerat-ing at corner exit are difficult to reproduce in wind tunnels and would require several camer-as to measure the tire deformation. In contrast, an FE approach is capable of determining the tire deformation in combined load states accurately and additionally provides the possibility to vary further parameters, for example, the coefficient of friction. The FE tire model was validated using stiffness measurements, contact patch measurements and steady-state cornering measurements on a flat belt tire test rig. The deformed shape of the FE model was used in a computational fluid dynamics (CFD) simulation. A sensitivity study was created to determine the effect of the tire deformation on aerodynamics for un-loaded, purely vertically loaded and combined vertical, lateral and longitudinal forces. In addition, the influence of these three tire deformations was investigated in a CFD study using a full vehicle…
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A Study on the Effect of Debris Location on a Double Element Wing in Ground Effect

Loughborough University-Tom Marsh, Graham Hodgson, Andrew Garmory, Dipesh Patel
  • Technical Paper
  • 2020-01-0693
To be published on 2020-04-14 by SAE International in United States
Multi-element front wings are essential in numerous motorsport series, such as Formula 1, for the generation of downforce and control of the onset flows to other surfaces and cooling systems. Rubber tyre debris from the soft compounds used in such series can become attached to the wing, reducing downforce, increasing drag and altering the wake characteristics of the wing. This work studies, through force balance and Particle Image Velocimetry measurements, the effect a piece of debris has on an inverted double element wing in ground effect. The wing was mounted at a ride height determined to minimise separation from a fixed false-floor in the Loughborough University Large Wind Tunnel. The debris is modelled using a hard-setting putty and is located at different span and chord-wise positions around the wing. The sensitivity to location is studied and the effect on the wake analysed using PIV measurements. The largest effect on downforce was observed when the debris was located on the underside of the wing towards the endplates. The wake was most effected when the debris was…
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Investigation of the Effectiveness of a Passive Device for Soiling Mitigation for Vehicle Side-Cameras

Ontario Tech University-William Collings, Wing Yi Pao, Martin Agelin-chaab
  • Technical Paper
  • 2020-01-0699
To be published on 2020-04-14 by SAE International in United States
The development of modern autonomous automotive technology depends heavily on the reliable performance of external sensors that are vulnerable to soiling. Existing active cleaning devices, such as washers and wipers, are relatively complex, expensive or unsuitable. Furthermore, little research has been done on alternative soiling mitigation strategies and devices for sensors. With the emerging trend to replace side-mirrors with camera monitor systems, it is important for such systems to stay clean even in adverse weather in order to provide critical navigation information. To meet this need, a passive aerodynamics-based cleaning device was investigated. A converging vent device was integrated into the side-camera housing and the subsequent degree of soiling was estimated at wind speeds of 15, 20, and 25 m/s (representing city and country driving speeds). The vent outlet width, outlet jet angle, and outlet jet velocity of the vent device were varied and the variants were compared to the non-vented reference model. The degree of soiling was evaluated computationally and experimentally. A single phase simulation was performed using ANSYS® Fluent where the degree of…
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Investigation of Transient Aerodynamic Effects on Public Highways in Comparison to Individual Driving Situations on a Test Site

FKFS-Felix Wittmeier, Andreas Wagner, Jochen Wiedemann
German Aerospace Center (DLR)-Henning Wilhelmi, Andreas Dillmann
  • Technical Paper
  • 2020-01-0670
To be published on 2020-04-14 by SAE International in United States
Natural wind, roadside obstacles, terrain roughness, and traffic can influence the incident flow of a vehicle driven on public roads. These on-road conditions differ from the idealized statistical steady-state flow environment utilized in CFD simulations and wind tunnel experiments. To understand these transient on-road conditions better, measurements were taken on a test site and on German Autobahn, resulting in the characterization of the transient aerodynamic effects around a vehicle. A compact car was equipped with a measurement system that is capable of determining the transient airflow around the vehicle and the vehicle’s actual driving state. This vehicle was driven several times on a fixed route to investigate different traffic densities on public highways in southern Germany. The tests were conducted under consistent weather conditions and average wind velocities of 2-5 m/s. During the tests the transient incident flow and pressure distribution on the vehicle surface were measured. With the same vehicle, individual driving situations were recreated on a test site. This paper presents a comparison of the aerodynamic characteristics measured by the vehicle during a…
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Optimization of the Aerodynamic Lift and Drag of LYNK&CO 03+ with Simulation and Wind Tunnel Test

Dassault Systemes(Shanghai) Information Technology Co.-Weiliang Xie, Bo Li, Xiaowei Zhao
Geely Automobile Research Institute-Qian Feng, Biaoneng Luo, Huixiang Zhang, Hong Peng, Zhenying Zhu, Zhi Ding, Ling Zhu
  • Technical Paper
  • 2020-01-0672
To be published on 2020-04-14 by SAE International in United States
Based on the first sedan of the LYNK&CO brand from Geely, a high performance configuration with the additional aerodynamic package was developed. The aerodynamic package including the front wheel deflector, the front lip, the side skirt, the rear spoiler and the rear diffuser, were upgraded to generate enough aerodynamic downforce for better handing stability, without too much compromising of the aerodynamic drag of the vehicle to keep a low fuel consumption. Simulation approach with PowerFLOW, combined with the design space exploration method were used to optimize both of the aerodynamic lift and drag. Wind tunnel test was also used to firstly calibrate the simulation results and finally to validate the optimized design. The results turn out to be appropriate trade-off between the lift and the drag to meet the aerodynamics requirement, and a consistently good matching between the simulation and test.