Improvement of aerodynamic properties of ground vehicles using flow control is emerging technology and there is a febrile activity in both academia and industry in this field. Focus today is on development of passive and active flow control devices capable of decreasing the aerodynamic drag of vehicles with focus on trucks and passenger cars. However, the potential of such devices is large even for buses and trains and for improvement of other aerodynamic properties such as lateral stability.
Time-dependent simulations are powerful tools for studying and improving flow control devices. Although CFD simulations of flow control around ground vehicles is rather new research field, our academic work in the field is at the forefront and we have performed some of the first LES and hybrid RANS-LES simulations of these flows. Flows around vehicles with passive flow control devices can be much more accurately predicted with time-dependent techniques than using RANS. The active flow control devices using periodic blowing and suction can be studied using time-dependent techniques only, because of their unsteady character.
One example of our simulations of flow control devices is that of drag reduction of simplified truck using periodic blowing and suction shown in the following animation:
Another example of flow control is that of the flow around A-pillar of generic passenger car shown in following figures:
Figure 1. Flow control around A pillar of a simplified passenger vehicle.