The Sideways Dynamic Force on Passenger Cars in Turbulent Winds

The dynamic response of cars in turbulent winds is investigated in three wind-tunnel experiments: a 1:12 sharp-edged car model; a 1:10 Audi A4 model; and a racing and passenger full-scale car. The resultant side force spectra for various turbulence levels were measured which showed a phenomena not previously observed in cars: the side force spectral bandwidth becomes narrower with increase in turbulence. The vortex-shedding Strouhal number of the cars was found to be 0.27. As this can be close to the resonance of cars, it is suggested that suspensions be tuned accordingly and turbulence should be modelled in dynamic testing in wind tunnels.