Research Papers: Flows in Complex Systems

Forces and Flow Structures on a Simplified Car Model Exposed to an Unsteady Harmonic Crosswind

[+] Author and Article Information
Valérie Ferrand

Université de Toulouse,
Institut Supérieur de l'Aéronautique et
de l'Espace (ISAE),
10 Avenue Edouard Belin,
31400 Toulouse, France
e-mail: valerie.ferrand@isae.fr

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received July 19, 2012; final manuscript received August 28, 2013; published online October 7, 2013. Assoc. Editor: D. Keith Walters.

J. Fluids Eng 136(1), 011101 (Oct 07, 2013) (8 pages) Paper No: FE-12-1336; doi: 10.1115/1.4025466 History: Received July 19, 2012; Revised August 28, 2013

A ground vehicle traveling along a road is subject to unsteady crosswinds in a number of situations. In windy conditions, for example, the natural atmospheric wind can exhibit strong lateral gusts. Other situations, such as tunnel exits or overtaking induce sudden changes in crosswinds, as well. The interaction of this unsteady oncoming flow with the vehicle and the resulting aerodynamic forces and moments affect the vehicle stability and comfort. The objectives of the current study are to improve the understanding of flow physics of such transient flow and ultimately to develop measurement techniques to quantify the vehicle’s sensitivity to unsteady crosswind. A square back simplified car model is exposed to a forced oscillating yaw and results are compared to static measurements. Tests are conducted at Reynolds number Re = 3.7 × 105 and reduced frequencies ranging from 0.265 × 10−2 to 5.3 × 10−2. Unsteady side force and yawing moment measurements are associated with particle image velocimetry flow fields to interpret dynamic loads in link with flow topology evolution. Phase average force and moment measurements are found to exhibit a phase shift between static and dynamic tests that increases with oscillating frequency. Velocity fields reveal that the phase-shift seems to originate from the rear part of the car model. Moreover, lateral vortical structures appearing on the lee side from β = 15 deg increase this phase-shift and consequently appear to be favorable to the lateral stability of the vehicle.

Copyright © 2014 by ASME
Your Session has timed out. Please sign back in to continue.


Hucho, W. H., 1998, Aerodynamics of Road Vehicles, 4th ed., SAE International, Chap. 5.
Baker, C. J., 1986, “A Simplified Analysis of Various Types of Wind Induced Road Vehicle Accidents,” J. Wind Eng. Ind. Aerodyn., 22, pp. 69–85. [CrossRef]
Cooper, R., 1984, “Atmospheric Turbulence With Respect to Moving Ground Vehicles,” J. Wind Eng. Ind. Aerodyn., 17, pp. 215–238. [CrossRef]
Baker, C. J., 1991, “Ground Vehicles in High Cross Winds part II: Unsteady Aerodynamic Forces,” J. Fluids Struct., 5, pp. 91–111a. [CrossRef]
Bearman, P., and Mullarkey, S., 1994, “Aerodynamic Forces on Road Vehicles Due to Steady Side Winds and Gusts,” RAeS Conference on Vehicle Aerodynamics, Loughborough, UK.
Bocciolone, M., Cheli, F., Corradi, R., Muggiasca, S., and Tomasini, G., 2008, “Crosswind Action on Rail Vehicles: Wind Tunnel Experimental Analyses,” J. Wind Eng. Ind. Aerodyn., 96, pp. 584–610. [CrossRef]
Passmore, M. A., Richardson, S., and Imam, A., 2001, “An Experimental Study of Unsteady Vehicle Aerodynamics,” Proc. Inst. Mech. Eng., 215 (part D), pp. 779–788. [CrossRef]
Baker, C. J., and Humphreys, N. D., 1996, “Assessment of the Adequacy of Various Wind Tunnel Techniques to Obtain Aerodynamic Data for Ground Vehicles in Cross Winds,” J. Wind Eng. Ind. Aerodyn., 60, pp. 49–68. [CrossRef]
Sims-Williams, D., 2011, “Cross Winds and Transients: Reality, Simulation and Effects”, SAE Technical Paper No. 2011-01-0172.
Volpe, R., Da Silva, A., Ferrand, V., Le Moyne, L., 2013, “Experimental and Numerical Validation of a Wind Gust Facility,” ASME J. Fluid Eng., 135, p. 011106. [CrossRef]
Beauvais, F., 1967, “Transient Nature of Wind Gust Effects on an Automobile, SAE Technical Paper No. 670608.
Cairns, R. S., 1994, “Lateral Aerodynamic Characteristics of Motor Vehicles in Transient Crosswinds,” Ph.D. thesis, Cranfield Institute of Technology, Cranfield, Bedford, UK.
Chadwick, A., 1999, “Crosswind Aerodynamics of Sports Utility Vehicles,” Ph.D. thesis, Cranfield University, Cranfield, Bedford, UK.
Tsubokura, M., Nakashima, T., Kitayama, M., Ikawa, Y., Doh, D. H., and Kobayashi, T., 2010, “Large Eddy Simulation on the Unsteady Aerodynamic Response of a Road Vehicle in Transient Crosswinds,” Int. J. Heat Fluid Flow, 31, pp. 1075–1086. [CrossRef]
Krajnovic, S., Ringqvist, P., Nakade, K., and Basara, B., 2012, “Large Eddy Simulation of the Flow Around a Simplified Train Moving Through a Crosswind Flow,” J. Wind Eng. Ind. Aerodyn., 110, pp. 86–99. [CrossRef]
Dominy, R., and Ryan, A., 1999, “An Improved Wind Tunnel Configuration for the Investigation of Aerodynamic Crosswind Gust Response,” SAE Technical Paper No. 1999-01-0808.
Favre, T., and Efraimsson, G., 2011, “An Assessment of Detached-Eddy Simulations of Unsteady Crosswind Aerodynamics of Road Vehicles,” Flow, Turbulence and Combustion, 87, pp. 133–163. [CrossRef]
Garry, K. P., and Cooper, K. R., 1998, “Comparison of Quasi-Static and Dynamic Wind Tunnel Measurements on Simplified Tractor-Trailer Models,” J. Wind Eng. Ind. Aerodyn., 22, pp. 185–194. [CrossRef]
Mansor, S., and Passmore, M. A., 2007, “Estimation of Bluff Body Transient Aerodynamics Using an Oscillating Model Rig,” J. Wind Eng. Ind. Aerodyn., 96, pp. 1218–1231. [CrossRef]
Chometon, F., Strzelecki, A., Ferrand, V., Dechipre, H., Dufour, P. C., Gohlke, M., and Herbert, V., 2005, “Experimental Study of Unsteady Wakes Behind an Oscillating Car model,” SAE Technical Paper No. 2005-01-0604.
Wojciak, J., Theissen, P., Heuler, K., Indinger, T., Adams, N., and Demuth, R., 2011, “Experimental Investigation of Unsteady Vehicle Aerodynamics under Time-Dependent Flow Conditions-Part 2,” SAE Technical Paper No. 2011-01-0164.
Guilmineau, E., and Chometon, F., 2007, “Experimental and Numerical Analysis of the Effect of Side Wind on a Simplified Car Model,” SAE Technical Paper No. 2007-01-0108.
Guilmineau, E., and Chometon, F., 2009, “Effect of Side Wind on a Simplified Car Model: Experimental and Numerical Analysis,” ASME J. Fluid Eng., 131, p. 021104. [CrossRef]
Krajnovic, S., Basara, B., and Bengtsson, A., 2011, “Large Eddy Simulation Investigation of the Hysteresis Effects in the Flow Around an Oscillating Ground Vehicle,” ASME J. Fluid Eng., 133, p. 121103. [CrossRef]
Diana, G., Resta, F., and Rocchi, D., 2008, “A New Numerical Approach to Reproduce Bridge Aerodynamic Nonlinearities in Time Domain,” J. Wind Eng. Ind. Aerodyn., 96, pp. 1871–1884. [CrossRef]
Diana, G., Rocchi, D., Argentini, T., and Muggiasca, S., 2010, “Aerodynamic Instability of a Bridge Deck Section Model: Linear and Nonlinear Approach to Force Modeling,” J. Wind Eng. Ind. Aerodyn., 98, pp. 363–374. [CrossRef]
Gohlke, M., Beaudoin, J. F., Amielh, M., and Anselmet, F., 2007, “Experimental Analysis of Flow Structures and Forces on a 3D-Bluff-Body in Constant Cross-Wind,” Exp. Fluids, 43, pp. 579–594. [CrossRef]
Goetz, H., 1995, “Crosswind Facilities and Procedures,” SAE Paper No. 1109.
Kum, R., 1998, “Investigation of the Comparison Method for the Dynamic Calibration of Force Transducers,” Measurements, 3, pp. 239–245. [CrossRef]


Grahic Jump Location
Fig. 1

Experimental test bench: elevated floor and turntable dispositive

Grahic Jump Location
Fig. 2

One period of the dynamic yaw movement for f* = 1.325 × 10−2 and -10 deg≤β≤10 deg

Grahic Jump Location
Fig. 3

Top, side, and front views of the “Willy” body

Grahic Jump Location
Fig. 4(a)

The two-component force balance and (b) front and rear load cell contribution to a point side force “Fcalibration

Grahic Jump Location
Fig. 5

Schematic view of force balance dynamic calibration equipment

Grahic Jump Location
Fig. 6

PIV configurations

Grahic Jump Location
Fig. 7

Static evolution of Cy with β

Grahic Jump Location
Fig. 8

Static evolution of CN with β

Grahic Jump Location
Fig. 9

Static evolution of the center of pressure XCP/Lref with β

Grahic Jump Location
Fig. 10

Static mean velocity field at X/Lref = 0.5, colored by the normalized mean vorticity Ωx.Lref/U0. Data extracted from PIV measurements.

Grahic Jump Location
Fig. 11

Static mean velocity field at Z/Lref = 0.45, colored by the normalized mean length (U2+V2)1/2/U0. Data extracted from PIV measurements.

Grahic Jump Location
Fig. 12

(U2+V2)1/2/U0 distribution along the curve C. Data extracted from PIV measurements.

Grahic Jump Location
Fig. 13

Cy and CN measured for the reduced frequencies f* = 0.265 × 10−2, 1.325 × 10 − 2, 2.65 × 10−2, 5.3 × 10−2, and -10 deg≤β≤10 deg compared to the corresponding static curve

Grahic Jump Location
Fig. 14

Cy and CN measured for the reduced frequencies f* = 0.265 × 10−2, 1.325 × 10−2, 2.65 × 10−2, 5.3 × 10−2, and 10 deg≤β≤30 deg compared to the corresponding static curve

Grahic Jump Location
Fig. 15

Dephasing Δϕ (in deg) of the dynamic case (f* = 5.3 × 10−2) compared to the static case for Cy and CN. The two yaw ranges -10 deg≤β≤10 deg and 10 deg≤β≤30 are presented.

Grahic Jump Location
Fig. 16

(U2+V2)1/2/U0 distribution along the curve C. Comparison of static and dynamic cases.

Grahic Jump Location
Fig. 17

Comparison of static and dynamic (f* = 5.3 × 10−2) mean velocity fields at X/Lref = 0.5 for β = 28 deg, colored by the normalized mean vorticity Ωx.Lref/U0. Data extracted from PIV measurements.

Grahic Jump Location
Fig. 18

Side force coefficients associated with the front and rear load cell measurements. Static and dynamic cases (f* = 5.3 × 10−2) for the two yaw angle ranges -10 deg≤β≤10 deg and10 deg≤β≤30 deg



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In