An Investigation into pressure variation of fluid over a car surface

Abstract

The early attempts to streamline cars were made according to aeronautical practice and by adapting shapes from naval architecture.These failed due to two reasons.First, the benefits of aerodynamics were simply not needed. Bad roads and low engine power only permitted moderate driving speeds. Second,the approach of directly transplanting (with almost no change) shapes which had been developed for aeronautical and marine purposes was not appropriate[1]. The shape of cars changed in an evolutionary manner over the years in order to improve the efficiency. The two oil crises of 1970’s generated great pressure for improving fuel economy drastically, and provided a breakthrough for vehicle aerodynamics. Since then, drag coefficient have come down dramatically. This has been a major contributor to the large improvements in fuel economy that have been realised.The motivation for allowing aerodynamics to influence the shape of vehicles, if not their style, is the market situation, and their changes with time. Fuel economy and increasingly global warming are the current key arguments for low drag worldwide. In Europe particularly Germany, a top speed is still considered an important sales feature despite the rapidly increasing traffic density which largely prohibits fast driving even in the absence of speed limits. The influence of aerodynamics on this demand supply relationship is through the drag force, which affects the propulsive part of the demand side. Commercial aircraft, trains, ships and highway trucks typically operate at a relatively constant cruising speed. In typical automobile driving, however vehicle speed varies with time or distance.