Effects of the roll angle on cruciform wing-body configurations at high incidences

Abstract

Three cruciform wings were tested on a body at five roll angles and up to three longitudinal positions in a lowspeed wind tunnel, up to an angle of attack of a = 90 deg. The roll angle affects significantly the fin normal force coefficient. The normal force on the upper fins decreases to zero, at a > 40 deg, possibly because the vortex breakdown on the lower fins induces separated flow over the upper fins. As a consequence, a strong rolling moment is induced at these incidences at asymmetric roll angles. This rolling moment is independent of the wing axial position but proportional to the wing planform area, similarly to the fin normal force coefficient. This rolling moment is much larger than the rolling moment induced on symmetrical configurations by the asymmetric body vortices. The wing contribution to the side force is small compared with the body contribution at asymmetric roll angles. As a result, the maximum side force is not higher than that obtained at symmetric + and X attitudes. Nomenclature= normal force coefficient, based on area S TQf = fin normal force coefficient, based on area ,S ref = fin normal force coefficient, based on area S* = yawing moment coefficient, based on area S ref and diameter d = rolling moment coefficient, based on area 5 ref and diameter d = rolling moment coefficient, based on area S* and diameter d ?= side force coefficient, based on area S Kf = body diameter; reference length for moment coefficients, m = Reynolds number, based on diameter d =body maximal cross section; reference area for force and moment coefficients, unless otherwise defined, m 2 = planform area of one pair of joined wings, m 2 = one fin planform area; reference area for CN* and C*. ,m 2 = fin longitudinal center of pressure, measured from the fin root chord apex, m = main normal force center of pressure, measured backward from the moment reference center, at 4.5d from the body nose, m =fin lateral center of pressure, measured from the root chord, m =model angle of attack, deg = azimuthal angle, measured clockwise from the windward edge of the body when looking forward, cf. Fig. 1, deg <| ) = model roll angle, positive clockwise when looking forward, zero at + attitude, cf. Fig. 1, deg Subscripts B=value of a coefficient for the body alone B(W) =body contribution to a coefficient W(B) = wing contribution to a coefficient

Prediction of Nonlinear Rolling and Magnus Coefficients of Cruciform-Finned Missiles

“…Reference [5] offers experimental wing on body-normal-force coefficients of a cruciform configuration (a=b 0:25 and AR 1:5) in the and attitudes, at Mach number 0.1, that can be compared with the predictions provided by the present method. Figure 3 depicts the experimental wing on the body-normal-force coefficient in the position, together with the least-squares fitting of the experimental values, up to an angle of attack above the wing vortex breakdown.…”