Abstract
This paper describes a relationship between aerodynamic drag on vehicle's backward face and the vortices behind the vehicle and a relationship between vehicle shape and vortices behind the vehicle was clarified by a stochastic analysis. The result shows that there is a vortex ring behind the vehicle and the distance between vortex ring and vehicle′s backward face have relation to aerodynamic drag on vehicle′s backward face. The result also shows the vortex tube transforms by vehicle shape and one of the vortex tube types reduces aerodynamic drag on vehicle′s backward face.
