In this two-part computational investigation, the effect of yaw angle (f on the drag generated by the presence of a clean sharp-edged rectangular cavity, embedded in a fully developed turbulent boundary layer, generated over a flat plate is studied, referred to hereafter as the long inlet cases; along with a study of the effect of geometric variation of fundamental cavity parameters, namely L/D & L/W ratios, for a cavity embedded in a smaller, non-fully developed turbulent boundary layer, referred to hereafter as the short inlet cases. Majority of research into cavity flows focus on the acoustic signature generated by unsteady pressure variations within the cavity, with some venturing into the search of effective acoustic suppression techniques. However, the drag caused by surface cutouts can be substantial, generating shear layer oscillations, which could alter the performance of vehicles containing said surfaces, and potentially produce damaging structural loading. This justifies the need of a study into the drag characteristics of cavities when subjected to yaw and geometric variation. Past experimental investigations suggest a flow transition within the cavity as the yaw angle is varied. Hence, to develop an improved understanding of the flow phenomena involved and the effect of the effect of f, L, D, and W variations on the drag generated within the cavities, steady state simulations were performed using OpenFOAM, an open-source CFD package [17]. For the long inlet case, a cavity with an effective L/D ratio of 16.25 and L/W ratio of 8.125 at f 900, is studied at f of 00, 300, 450, 600, 750, & 900, with an incoming freestream velocity of 25 m/s. For the short inlet cases, five L/D variations at a fixed L/W, and three L/W variations at a fixed L/D, are studied with changing f of 00, 300, 450, 600, 750, & 900 for each one of L/D and L/W variation. The steady pressure contours on the cavity faces are computed and analyzed along with computed drag coefficient. The pressure profiles and drag data suggest a critical change in cavity behavior when the flow transitions from an open type to closed type. A change in cavity behavior is also observed as the L/D and L/W ratios are varied. To verify validity of the code used, the long inlet cavity drag was compared with published experimental literature by Weighardt [2]. |