Numerical Investigations on the Effects of the Declining Back-Edge of MVG

Abstract

Due to the background in the mixed compression engine inlets, the Shock wave/ Turbulent Boundary Layer Interaction (STBLI) problem has been one of the concerns of the aerodynamic industry. Shock-induced separation and the corresponding interaction make the flow losing its quality and reduce inlet total pressure recovery. Various flow-control methods have been tried and investigated by lots of researchers, such as passive controls like vortex generators and active controls like bleeding. Recently, micro vortex generators (MVGs) are paid upon more and more attention as the remarkable experimental ewsults obtained by Barbinsky [1] . The MVG is different from its conventional counterpart by possessing a height of the 20~60% width of the boundary layer, while the height of the conventional one is the same order of the width. The basic idea of MVG is to generate the counter-rotating streamwise vortices, which bring the high momentum fluid from the outer flow to the inner boundary; meanwhile the weak jets-like streamwise vortices has the ability to push away the unfavorable flow gradient. When MVGs are put before the separation region, it is possible to reduce the size of separation and make the boundary layer more “healthy” by means of parameters like the shape factor. Because MVGs are often used in supersonic flows, MVG can produce series of disturbing waves as well. What’s more, due to the existence of a solid body in the flow, a momentum deficit region was found to be superimposed between the pair of the streamwise vortices. As mentioned by Barbinsky [1] , this implies larger drag, which is unfavorable to the engineers. In order to investigate the influence of the geometry of MVG to the low momentum deficit, MVGs with different back-edge declining angle are investigated numerically in this work. Two declining angle are selected as 70o and 45o. The former is more vertical and similar to the shape used by Barbinsky, the latter declines relatively slowly and smoothly. The sketches of the geometry are shown as following: