Aeroprediction code for angles of attack above 30 degree

Abstract

The U.S. Naval Surface Warfare Center Dahlgren Division aeroprediction code has been extended to angles of attack greater than 30 deg. To accomplish this, several databases were used to approximate the nonlinearities in individual missile component aerodynamics. Theoretical aerodynamic methods were used at small angles of attack. The new semiempirical model was then applied to several configurations and the empirical constants fine tuned so as to minimize some of the errors associated with wind-tunnel measurements of component aerodynamics at high angles of attack. New and improved technology developed includes 1) extension of the wing-body and body-wing interference factor methodology above angle of attack of 30 deg for both zero and nonzero control deflections and 2) refinements in body-alone normal force and center-of-pressure prediction to account for Reynolds number, and transonic and asymmetrically shed body vortices. All methodology is developed for the * = 0-deg (or fins in plus) roll orientation. Comparison of the new methodology to several cases outside the databases on which the methodology was developed appears to indicate the average accuracy goals of ±10% on normal force and ±4% of body length on center of pressure were maintained for the higher angles of attack. NomenclatureA P = planform area of the body or wing in the crossflow plane, ft 2 A re f = reference area (maximum cross-sectional area of body, if a body is present, or planform area of wing, if wing alone), ft 2 A w , S w = planform area of wing in crossflow plane, ft 2 A wetted = area of body or wing that flow touches 0o, 0i, 02,03,04 = constants used in nonlinear wing-alone model b = wing span (not including body), ft CA = axial force coefficient CA B , CA F , CA W = base, skin-friction, and wave components, respectively, of axial force coefficient CD C = crossflow drag coefficient C F£ , CF T -laminar and turbulent skin friction coefficients, respectively CM = pitching moment coefficient (based on reference area and body diameter, if body present, or mean aerodynamic chord, if wing alone) C N = normal force coefficient C Ns -normal force coefficient of body alone Cff L = linear component of normal force coefficient CN NL = nonlinear component of normal force coefficient CN T(V) = negative normal force coefficient component on tail due to wing or canard-shed vortex C Nw = normal force coefficient of wing alone C Na = normal force coefficient derivative d = body diameter, ft = rate at which K W ( B ) or K B ( W ) decreases = dimensionless empirical factors used in nonlinear models of k W ( B ) and C# r(v) to approximate effects resulting from high angle of attack or control deflection fw, fr = lateral location of wing or tail vortex (measured in feet from body centerline) : = tail interference factor