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The measured windscreen defrost pattern for a saloon car has been compared with two CFD simulation methods and with the results obtained using a thermal imaging camera. The objectives were to determine: if CFD could be used with confidence to simulate defrost performance; the difference between the two CFD methods; the ability of the thermal imaging technique to predict defrost performance; the most appropriate use of these techniques during an HVAC development programme. There was a good comparison between the defrost pattern on the windscreen and the results from the thermal imaging camera and the two CFD methods. The CFD methods have been shown to be suitable for fault finding and recommending their use is reinforced for development work of ducts and vents in the HVAC system. Airflow direction and distribution could be implied from the thermal camera images, which makes it a suitable tool for fine tuning duct and vent designs at the final stages of the design programme.

MIRA and Rover Group Ltd have undertaken a systematic study of the ability of CFD methods to predict the aerodynamic characteristics of simplified car-like shapes. This paper reports the latest stage of this investigation, which examines the use of a commercial Reynolds-averaged Navier-Stokes code (STAR-CD) to predict the aerodynamic characteristics of a series of simplified car shapes. Comparable experimental data were obtained by testing in the MIRA Full Scale Wind Tunnel (FSWT). This paper shows that CFD techniques are improving in their ability to predict flow separation from curved surfaces accurately. Further, encouraging results for vehicle drag (coefficients to within 2% of experiment) and the effect of limited geometric modifications on drag (within 7% of full-scale experiment) were obtained. However these latter results should be viewed with some caution as the results for lift were considerably poorer.