Prediction and control of optical wave front distortions and aberrations in a high energy laser beam due to interaction with an unsteady highly non-uniform flow field is of great importance in the development of directed energy weapon systems for an Unmanned Combat Air Vehicle (UCAV). Unsteady shear layer over the weapons bay cavity is the primary cause of this distortion of optical wave front at the time of ejection of laser guided weapon from the cavity. Both passive and active control devices have been proposed in the literature to suppress the cavity oscillations. In this paper, we perform numerical simulations for a L/D=4 cavity (L=width and D=depth of the cavity) with a sharp leading edge and curved leading edges of three different radii using steady and pulsed blowing at the leading edge in a direction normal to the free stream. Computations are compared with the experimental data from University of Notre Dame for root mean square Optical Path Difference (OPDrms).