A new model of blowing or suction based on mathematic roughness function*

Blowing or suction is a very efficient drag reduction technique. In this paper, a new model of blowing or suction is introduced by using the new concept of mathematic roughness function. The boundary condition of blowing or suction is modified from velocity form to vorticity form. The numerical method which does not require grids is used to simulate the blowing or suction process. In the simulation, the strength and position of blowing or suction is changed to investigate their influence to drag reduction. Some useful conclusions are drawn through the simulation.