Experimental and Numerical Evaluation of the Effect of Boundary Layers Interaction on Drag Reduction

Numerical and experimental evaluation of total drag of a quad cylinder in the vicinity of a flat plate is investigated. A quad of rectangular shape and later a quad with optimal drag are placed near and the inside of a turbulent boundary layer of a flat plate. The drag on the flat plate and the quad are measured separately and compared to the case when they are in similar flow field lonely. The experiment is performed by employing a low speed wind tunnel. The measuring device was a one Dyne accurate load cell. Conclusion is reaveled that when the obstacle closes to the flat plate, the total drag is reduced to a minimum and then increases again at very close to the plate. For the case of square cylinder the minimum distance is about 2.5 millimeter. The same conclusion is arrived to by reforming a numerical evaluation of the same flow fields and results are reported.