Side-Force Alleviation on Slender, Pointed Forebodies at High Angles of Attack

A new concept for alleviating the high angle-of-attack asymmetry on slender, pointed forebodies has been proposed and tested. A pair of helical trips are used to force nonuniform crossflow separation from the forebody to disrupt the formation of concentrated leeside vortices. Subsonic wind-tunnel measurements on bodies with circular and noncircular cross sections and an aircraft-type configuration at up to 55 deg angle of attack showed that the device was highly effective in suppressing the side force. Water-tunnel flow visualizations confirmed that the helical trips rapidly diffused the forebody vortices and prevented wake asymmetry. Nomenclature! CD = drag coefficient CL = lift coefficient CY = side-force coefficient C, = rolling moment coefficient (body axis) Cm = pitching moment coefficient Cn = yawing moment coefficient (body axis) C, = rolling moment due to sideslip, per deg Cn = yawing moment due to sideslip, per deg a. = angle of attack, deg |8 = angle of sideslip, deg