Drag reduction of motor vehicles by active flow control using the Coanda effect

A test facility has been constructed to realistically simulate the flow aro und a two dimensional car shaped body in a wind tunnel. A moving belt simul ator has been employed to generate the relative motion between model and gr ound. In a first step, the aerodynamic coefficients c(L) and c(D) of the mo del are determined using static pressure and force measurements, LDA-measur ements behind the model show the large vortex and turbulence structures of the near and far wake. In a second step, the ambient flow around the model is modified by way of an active flow control which uses the Coanda effect, whereby the base-pressure increases by nearly 50% and the total drag can be reduced by 10%. The recirculating region is completely eliminated. The cur rent work reveals the fundamental physical phenomena of the new method by o bserving the pressure forces on the model surface as well as the time avera ged velocities and turbulence distributions for the near and far wake. A th eory resting on this empirical information is developed and provides inform ation about the effectiveness of the blowing method; For this, momentum and energy equations were applied the flow around the vehicle to enable a vali dation of the theoretical results using experimental values.