Fig.J-20 (Above) Aerodynamic drag of pick-up cars.
The test section floor in Fig.J-18 cannot fully simulate the influence of the road surface, which moves relative to the real car riding on road. Substantial improvement is achievable by the moving belt, Fig.J-19 (this figure lists also other alternatives and the improvement they achieve). Practical importance of low aerodynamic drag even for utility cars, not indended to be driven fast, is shown in Fig.J-20, where there is
Fig.J-21
a comparison for two values - those typical for periods before and after WWII. Passenger cars may be built to higher aerodynamic standard (Fig.J-22) than pick-ups.
Fig.J-22












The following Fig.J-23 shows the overall general trend of development and the theoretical minimum - while Fig.J-24 shows what is probably the minimum achievable in a practical car. It is not only the frontal drag which is of importance for aerodynamic design of a car. Since the forwards speed of a car is vector added to side wind, cars or car models in a wind tunnel must
Fig.J-23







be measured at different angles of yaw. Apart from drag, also the vertical force is of interest - usual requirement is for the lift to be negative, i.e. acting towards the road surface.
Fig.J-24








Fig.J-25


Going to another page: click
This is page Nr. J09 from textbook Vaclav TESAR : "BASIC FLUID MECHANICS"
Any comments and suggestions concerning this text may be mailed to the author to his address tesar@fsid.cvut.cz

WWW server administrators: Jiri Kvarda, Zdenek Maruna ...... Contact: webmaster@vc.cvut.cz
Last change : 25.03.1997