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Viewing 1 to 30 of 2605
2016-06-15
Technical Paper
2016-01-1803
Hannes Frank, Claus-Dieter Munz
Avoiding narrowband components in the acoustic spectrum is one of the most critical objectives in the automotive aeroacoustic optimization process. The underlying physical mechanisms are not completely understood. In a preceding numerical and experimental investigation, we performed large eddy simulations of an early-development stage realistic side-view mirror, where tonal noise was captured and the principle mechanisms were identified. In this contribution, we present simulations on a simplified two-dimensional geometry that is based on these findings. It is shown that the basic flow topology relevant for tonal noise generation on the original side-view mirror as well as the tonal noise source is reproduced in the 2D case. Furthermore, we present comparisons with measurements and the necessity and influence of a splitter plate downstream of the 2D body to avoid large scale vortex shedding.
2016-06-15
Technical Paper
2016-01-1807
Olga Roditcheva, Lennart Carl Lofdahl, Simone Sebben, Pär Harling cEng, Holger Bernhardsson
Abstract This paper presents an experimental study of aeroacoustical sound sources generated by the turbulent flow around the side mirror of a Volvo V70. Measurements were carried out at the Volvo Cars aerodynamical wind tunnel (PVT) and at the aeroacoustical wind tunnel of Stuttgart University (FKFS). Several different measurement techniques were applied in both tunnels and the results were compared to each other. The configurations considered here were: side mirror with a cord and without the cord. The results discussed in this paper include intensity probe measurements in the flow around the side mirror, sound source localization with beamforming technique using a three-dimensional spherical array as well as standard measurements inside the car with an artificial head. This experimental study focused on understanding the differences between testing at the PVT and FKFS.
2016-06-15
Technical Paper
2016-01-1804
Stefan Becker, Katrin Nusser, Marco Oswald
Aim of the ongoing development of passenger cars is to predict the interior acoustics early in the development process. A significant noise component results from the flow phenomena in the area of the side window. The complex turbulent flow field in the wake of the a-pillar and the side mirror is characterized by velocity and pressure fluctuations. The flow field results in sound sources which transmit noise into the passenger cabin. In addition to that, it excites the structure, resulting in a radiation of structure-borne noise into the interior of the car. In the present work, as a first step in solving this three part problem, a Large Eddy simulation of the flow was conducted to investigate the sound generation due to external air turbulence. For this purpose, a simplified model of an automobile was used. In addition to the LES, a Delayed-Detached Eddy simulation (DDES) and an unsteady RANS (URANS) simulation of the same model were carried out.
2016-04-20
Standard
ARP6852A
This document describes methods that are known to have been used by aircraft manufacturers to evaluate aircraft aerodynamic performance and handling effects following application of aircraft ground deicing/anti-icing fluids (“fluids”), as well as methods under development. Guidance and insight based upon those experiences are provided, including: - Similarity Analyses - Icing Wind Tunnel Tests - Flight Tests - Computational Fluid Dynamics and other Numerical Analyses This document also describes: - The history of evaluation of the aerodynamic effects of fluids - The effects of fluids on aircraft aerodynamics - The testing for aerodynamic acceptability of fluids for SAE and regulatory qualification performed in accordance with AS5900 - Additionally, Appendices A to E present individual aircraft manufacturers’ histories and methodologies which substantially contributed to the improvement of knowledge and processes for the evaluation of fluid aerodynamic effects.
2016-04-14
Event
It's vital that we continue to explore fundamental aerodynamic effects and processes, to underpin future vehicle development. This two-part session underlines the importance of simplified models in building our understanding of wake structure, wheel rotation, cooling flows, onset flow turbulence and crosswinds. Beyond this, careful analysis of existing cars is used to provide further insights into multiple-vehicle platooning, and drag reduction technologies.
2016-04-14
Event
In this session the use of the Adjoint Method and its role in vehicle shape optimization will be explored. New simulation approaches will be presented, including Partially-Averaged Navier-Stokes (PANS) and a novel RANS and Implicit LES Hybrid Turbulence Model. The use of CFD for Cooling Drag sensitivity analysis is also discussed.
2016-04-14
Event
It's vital that we continue to explore fundamental aerodynamic effects and processes, to underpin future vehicle development. This two-part session underlines the importance of simplified models in building our understanding of wake structure, wheel rotation, cooling flows, onset flow turbulence and crosswinds. Beyond this, careful analysis of existing cars is used to provide further insights into multiple-vehicle platooning, and drag reduction technologies.
2016-04-13
Event
The emergence of unsteady simulation as a viable tool along with the continuing development of experimental methods has led to an increasing focus on the unsteady aerodynamic effects experienced by cars in use. This session investigates aerodynamics influences on vehicle dynamics: dynamic pitching, cross wind effects. Surface contamination is receiving increased attention as customer expectations rise. Hence, simulating soiling of rear vehicle surfaces and wetting of brake discs are explored.
2016-04-13
Event
Experimental facilities and methods continue to develop. This session covers wind tunnel interferences and their correction, along with a new ground simulation system and methods for introducing atmospheric levels of turbulence into wind tunnel testing. Developments presented in measurement techniques include: Tomographic PIV, Quantitative Tuft Image Processing, Strip Tube pressure measurement and a new small-scale PIV system.
2016-04-12
Event
Aerodynamics Development takes a practical view of the application of aerodynamics in industry. Starting with examining the use of CFD for the evaluation of early concepts, moving onto the development of a light truck - including on-road testing and culminating with drag reduction for EVs subject to crosswind.
2016-04-12
Event
Commercial vehicle aerodynamics is considered from both a component and test facility perspective. The effect of side-skirts is explored using a water tank. CFD is used to explore blockage effects in full scale wind tunnel tests. Finally, Scania’s New CD7 Climatic Wind Tunnel Facility for Heavy Trucks and Buses is described.
2016-04-12
WIP Standard
J2881
This Recommend Practics provides a procedure for documenting the aerodynamic performance for passenger vehicles, i.e., mass-produced cars and light-duty trucks intended primarily for individual consumers.
2016-04-12
Standard
J2084_201604
The scope of this SAE Information Report is confined to wind-tunnel testing, although it is recognized that many aspects of the aerodynamic characteristics of road vehicles can be investigated in other test facilities (such as water-tanks) or, especially, on the road. For example, coastdown testing is often used to determine aerodynamic drag (either in isolation or as part of the total resistance), and artificial gust generators are used to investigate the sensitivity of vehicles to cross-wind gusts. Also excluded from the present Report are climatic wind-tunnel tests of road vehicles, which are defined in more detail in Section 3. The Report covers the aerodynamic requirements of a wind-tunnel for automotive testing, together with the facility equipment needed and the requirements affecting the test vehicle or model.
2016-04-12
Event
Exploring the role of aerodynamics in Motorsports, from the development of a low-pitching-moment-helmet, through to combined aero-thermal testing and modelling aerodynamic effects on performance predictions. The session concludes with a survey of velocity fields and vortical structures around a Formula One Car, using PIV.
2016-04-12
Event
Aeroacoustics widely recognised as an important element in customer perceptions of vehicle quality. This session covers the simulation of rear side window buffeting, along with combining exterior time-resolved simulation with vibro-acoustics to predict wind noise in the cabin of a car.
2016-04-12
WIP Standard
J1594
This terminology is intended to provide a common nomenclature for use in publishing road vehicle aerodynamics data and reports.
2016-04-05
Journal Article
2016-01-1316
Vincent Rovedatti, Jacob Milhorn, Richard DeJong, Gordon Ebbitt
Abstract A 1/4 scale model vehicle profile has been tested in a wind tunnel with speeds up to 360 km/h. In order to simulate the free field flow over the vehicle, the top surface of the wind tunnel is contoured. A CFD simulation of the free field flow at various speeds is used to identify the desired top streamline. Then the boundary layer growth on the top surface is calculated and the top contour is adjusted accordingly. Since this contour changes very little with flow speeds of interest, an average contour is used for a fixed top surface of the wind tunnel. Pressure drop measurements are used to verify the flow similarity to the CFD model. Wind noise measurements using surface mounted pressure transducer arrays are used to determine the acoustic loads on the vehicle surfaces.
2016-04-05
Technical Paper
2016-01-0009
Soham Bakshi, Badih Jawad, Selin Arslan, Liping Liu, Kingman Yee
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.
2016-04-05
Journal Article
2016-01-1577
Tateru Fukagawa, Shinnosuke Shimokawa, Eiji Itakura, Hiroyuki Nakatani, Kenichi Kitahama
Abstract The aerodynamic stability of energy-saving, lightweight, and low-drag vehicles is reduced by crosswind disturbances. In particular, crosswinds cause unsteady motion in vehicles with low-drag body shapes due to aerodynamic yaw moment. To verify fluctuations in the unsteady aerodynamic forces of a vehicle, a direct measurement method of these forces in a crosswind test was established using inertial force and tire load data. The former uses an inertia sensor comprised of a gyro, acceleration sensor, and GPS sensor, and the latter uses a wheel force sensor. Noise in the measurement data caused by the natural frequency of the tires was reduced using a spectral subtraction method. It was confirmed that aerodynamic data measured in the crosswind test corresponded to wind tunnel test data. Numerical expressions were defined to model the unsteady aerodynamic forces in a crosswind.
2016-04-05
Journal Article
2016-01-1583
Brian R. McAuliffe, Alanna Wall, Guy Larose
Abstract During the past year, a novel turbulence generation system has been commissioned in the National Research Council (NRC) 9 m Wind Tunnel. This system, called the Road Turbulence System was developed to simulate with high fidelity the turbulence experienced by a heavy duty vehicle on the road at a geometrical scale of 30%. The turbulence characteristics that it can simulate were defined based on an extensive field measurement campaign on Canadian roads for various conditions (heavy and light traffic, topography, exposure) at heights above ground relevant not only for heavy duty vehicles but also for light duty vehicles. In an effort to improve continually the simulation of the road conditions for aerodynamic evaluations of ground vehicles, a study was carried out at NRC to define the applicability of the Road Turbulence System to aerodynamic testing of full-scale light duty vehicles.
2016-04-05
Technical Paper
2016-01-1584
Kenichi Ando, Naoshi Kuratani, Hideo Fukuda
Abstract An aerodynamic styling evaluation system employed at an early automotive development stage was constructed. The system based on CFD consists of exterior model morphing, computational mesh generation, flow calculation and result analysis, and the process is automatically and successively executed by process automation software. Response surfaces and a parallel coordinates chart output by the system allow users to find a well-balanced exterior form, in terms of aerodynamics and exterior styling, in a wide design space which are often arduous to be obtained by a conventional CAE manner and scale model wind tunnel testing. The system was designed so that 5-parameter study is completed within approximately two days, and consequently, has been widely applied to actual exterior styling development. An application for a hatchback vehicle is also introduced as an actual example.
2016-04-05
Technical Paper
2016-01-1586
Sinisa Krajnovic, Guglielmo Minelli, Branislav Basara
Partially-Averaged Navier-Stokes Simulations (PANS) were made of flow around a generic vehicle influenced by side wind at four different yaw angles to investigate the prediction capabilities of PANS. Comparisons with results of LES show clear advantages of PANS in predicting pressure-induced separation resulting in the trailing vortices aligned with the direction of the flow. Poorer agreement was obtained in the near wake when the boundary layer separates at the end of the surface at the rear end. A possible explanation for the lack of accuracy at the rear end of the body was found in the formulation of the switching coefficient fk which produces too low values resulting in too low eddy viscosity in this region.
2016-04-05
Journal Article
2016-01-1585
Takafumi Makihara, Takahiro Kitamura, Taro Yamashita, Kazuhiro Maeda, Chisachi Kato, Tsutomu Takayama, Kohei Yamamoto, Yoshinobu Yamade, Yasumasa Suzuki
Abstract It is important to reduce aerodynamic drag for reducing fuel consumption. Conventionally reduction of aerodynamic drag has been carried out by shape optimization of each part of a vehicle based on the investigations of the time-averaged flows around the vehicle. However, the general tendency of drag reduction has been saturated recently and it is required to develop a new flow-control technique to achieve further reduction in aerodynamic drag. We therefore focus on the unsteadiness of the flow around a vehicle to achieve it because the aerodynamic drag of a vehicle fluctuates over time due to repetitions of generation, growth, merging and disappearance of various sizes of vortices around it. These vortices are formed by flow separations, for which the longitudinal coherent vortices inside turbulent boundary layers on vehicle surfaces are presumably playing an important role.
2016-04-05
Technical Paper
2016-01-1581
Felix Wittmeier, Armin Michelbach, Jochen Wiedemann, Victor Senft
Abstract With its recent wind tunnel upgrade, FKFS installed the first interchangeable three-belt / five-belt-system (FKFS first®) in a full scale automotive wind tunnel. With the five-belt system, which today is a state-of-the-art ground simulation technique, the system is ideally suited for production vehicle development work. The five-belt system offers high flexibility, quick access to the underfloor and vehicle fixation, and setting the vehicle’s ride height by the restraint device. The first results of the five-belt system have already been published in SAE 2015-01-1557 [1]. The three-belt system on the other hand, offers a much more sophisticated ground simulation technique which is necessary especially for sports and racing cars. For such vehicles with very low ground clearances, it is important to have a more accurate ground simulation, in order to capture the same aerodynamic modes of action and response as on the road.
2016-04-05
Technical Paper
2016-01-1606
Charalampos Kounenis, Sabine Bonitz, Emil Ljungskog, David Sims-Williams, Lennart Lofdahl, Alexander Broniewicz, Lars Larsson, Simone Sebben
Abstract The aerodynamic drag, fuel consumption and hence CO2 emissions, of a road vehicle depend strongly on its flow structures and the pressure drag generated. The rear end flow which is an area of complex three-dimensional flow structures, contributes to the wake development and the overall aerodynamic performance of the vehicle. This paper seeks to provide improved insight into this flow region to better inform future drag reduction strategies. Using experimental and numerical techniques, two vehicle shapes have been studied; a 30% scale model of a Volvo S60 representing a 2003MY vehicle and a full scale 2010MY S60. First the surface topology of the rear end (rear window and trunk deck) of both configurations is analysed, using paint to visualise the skin friction pattern. By means of critical points, the pattern is characterized and changes are identified studying the location and type of the occurring singularities.
2016-04-05
Journal Article
2016-01-1605
Daniel Stoll, Christoph Schoenleber, Felix Wittmeier, Timo Kuthada, Jochen Wiedemann
Abstract In this paper the influence of different turbulent flow conditions on the aerodynamic drag of a quarter scale model with notchback and estate back rear ends is investigated. FKFS swing® (Side Wind Generator) is used to generate a turbulent flow field in the test section of the IVK model scale wind tunnel. In order to investigate the increase in drag with increasing yaw, a steady state yaw sweep is performed for both vehicle models. The shape of the drag curves vary for each vehicle model. The notchback model shows a more pronounced drag minimum at 0° yaw angle and experiences a more severe increase in drag at increasing yaw when compared to the estate back model. Unsteady time averaged aerodynamic drag values are obtained at two flow situations with different turbulent length scales, turbulence intensities, and yaw angle amplitudes. While the first one is representing light wind, the second one is recreating the presence of strong gusty wind.
2016-04-05
Journal Article
2016-01-1610
Anna-Kristina Perry, Mathew Almond, Martin Passmore, Robert Littlewood
Abstract This paper demonstrates the use of large scale tomographic PIV to study the wake region of a Windsor model. This forms part of a larger study intending to understand the mechanisms that drive drag force changes when rear end optimizations are applied. For the first time, tomographic PIV has been applied to a large airflow volume (0.125m3, 500 x 500 x 500mm), which is of sufficient size to capture the near wake of a 25% scale Windsor model in a single measurement. The measurement volume is illuminated using a 200mJ double pulsed Nd:Yag laser fitted with a volume optic and seeded with 300μm helium filled soap bubbles generated by a novel high output seeder. Images were captured using four 4M Pixel LaVision cameras. The tomographic results are shown to produce high quality data with the setup used, but further improvements and tests at higher Reynolds number could be conducted if an additional seeding rake was used to increase seeding density.
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