On the development of a turbulent boundary layer over staggered three dimensional cavities

Abstract

Studies by Gowree et al. have suggested that staggered three dimensional circular cavities can potentially reduce the skin friction drag of a turbulent boundary layer developing over a flat plate. This is true up to a certain Reynolds number, after which the drag rapidly increases. The detailed mechanism behind the drag increase and the possible skin friction drag reduction was not discussed, due to the limitations in the measurement technique. In the current experimental campaign the results found by Gowree et al. have been confirmed, in addition, to more detailed insight of the turbulent boundary layer over the first rows of cavities. Through numerical simulations we aim to give a heuristic explanation of the two distinct behaviours. Here we report some quantitative evidence of the mechanism that may govern the drag increase, which is the main focus of the current study. The modification of the flow field in the presence of the cavities provides a qualitative explanation of the drag reduction benefit which is subjected for further investigation.