Flow fields around a solar car whose shape has been optimized in wind tunnels are investigated by using Computational Fluid Dynamics. A third-order upwind-difference scheme and a zonal approach are employed in the calculation. On the boundaries of the zones, six sub-grid-systems are overlapping each other but the same grid points are commonly used in overlapping region in order to avoid interplating physical values on the boundaries. The computed drag coefficient including surface friction drag is compared with the experimental value measured in a full-size wind tunnel. The error is only about 4 %. The calculated result also shows that the pressure drag is about 80 % of the total drag force; the rest of the 20 % is caused by the surface friction. It is found from visualized flowfields that the upper flow has small separation but the flow under the body, on the other hand, has large separated regions and strong vortices. In particular, the large wake regions behind the front wheels and a pair of trailing vortices beneath both side edges of the solar panel cause a significant loss. Finally, strakes are attached to the body in order to get a smoother flow around the frontwheels and the body is inclined to weaken the trailing vortices. Those effects are measured in the wind tunnel. The drag coefficient of 0.11 is obtained, which is about 10 % less than that of the experimentally optimized shape.
Aerodynamic drag reduction of a solar car using CFD
Senkung des aerodynamischen Widerstandes eines Solarkraftwagens mit Hilfe der theoretischen Strömungslehre
1994
7 Seiten, 7 Bilder, 2 Tabellen, 12 Quellen
Conference paper
English
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