Flow regimes associated with yawed rectangular cavities

The present work is concerned with the aerodynamics of the turbulent bounda ry-layer flow over yawed rectangular cavities with the focus on the steady and unsteady pressures generated by the interaction. Cavities with a pIanfo rm aspect ratio of 4.85 and streamwise length to depth ratios from 1 to 3 w ere studied experimentally in a low-speed wind tunnel. The results indicated three main types of cavity flows. The shear layer bri dges the cavity for small angles between mean flow direction and minor cavi ty axis. The flow field remains almost two-dimensional with little change i n drag coefficient. Strong instabilities, associated with a rise in drag co efficient, are found when the cavity is yawed to greater angles. An aerodyn amic feedback mechanism depending on interactions between the separated she ar layer and the cavity fluid is suggested as the mechanism responsible for the generated oscillations. The influence of the cavity depth is, hereby, found to be fundamental as it determines the degree to which interactions b etween the separated shear layer and the cavity base occur. As a result bot h the magnitude and the frequency of the instabilities are a function of th e cavity depth. When rotating to higher angles a greater portion of the she ar layer reattaches to the cavity base which leads to a loss of flow organi sation and a significant increase in drag.