Effect of Geometric Parameters on the Aerodynamic Characteristics of Grid-Fin Cells at Supersonic Speeds

Abstract

*† Grid fins are an efficient means of aerodynamic control surfaces, where hinge moment requirement is low and marginal increase in drag is acceptable. Many theoretical, computational and experimental studies have been carried out on specific configurations. In the present study, the flow field inside individual grid fin cells has been studied. Effect of some geometrical design parameters like depth-to-height ratio, thickness-to-height ratio, web leading edge angle and cell width-to-height ratio has been investigated for cubical cells. The results indicate that above certain depth-to-height ratio, called critical depth-to-height ratio, the local normal force becomes negative. The critical depth-to-height ratio a) increase with increase in Mach number b) reduces with increase in angle of attack and c) reduces with increase in thickness. Different width-toheight ratio has been studied keeping the cross sectional area same. Increase in widthto-height ratio increases the normal force for a given depth due to higher area facing the flow, but the maximum normal force remains same due to reduction in critical depth.