Abstract:

ESDU 89014 provides a simple empirical means of estimating the normal force and pitching moment of axisymmetric forebody-cylinder combinations for angles of attack up to 90 degrees and Mach numbers up to 5. Although derived using wind-tunnel test data for cylinders with tangent-ogive and cone forebodies (with and without blunting) and secant-ogive and ellipsoid forebodies, the method is expected to give reasonable estimates for any axisymmetric forebody-cylinder combination with a smooth forebody shape. The method requires as inputs the normal-force-curve and pitching moment-curve slopes at zero angle of attack, which may be taken either from test data or calculated using ESDU 89008, and simple geometrical parameters which may be obtained from ESDU 77028. The use of the method is illustrated by a worked example. The effects of boat-tailing may be estimating using ESDU 87033. The calculation procedure is programmed in ESDUpac A9034, see ESDU 90034. At high angles of attack at subsonic and transonic Mach numbers, asymmetric vortex flow may occur on the leeward side of the body. This phenomenon, which is known to depend on such minor factors as small imperfections at the nose, has the effect of producing an out-of-plane force distribution that can result in large side forces and yawing moments. The Item considers this subject by providing a description of asymmetric vortex flow and the resulting forces, including effects of Reynolds number and forebody blunting. A discussion of Mach number effects is also given, together with an envelope of maximum side force.