Application of the Adaptive Wall Concept in Three Dimensions

Abstract

The adaptive wall concept requires that to obtain unconfined flow conditions in a wind tunnel in the presence of any model it is necessary and sufficient to match independent measured flow variables on a surface near the tunnel boundary with flow variables which satisfy the unconfined, undisturbed boundary condition at infinity. The technique was employed at a limited number of test conditions to adjust individually the variable porosity walls of the AEDC Aerodynamic Wind Tunnel (4T) in order to minimize wall interference effects on a generalized transonic model configuration. Data improvement was demonstrated for each set of conditions. A procedural description and results of the experiment are presented. Nomenclature CD = drag coefficient CL = lift coefficient Cm = pitching moment coefficient CP = pressure coefficient CTS = captive trajectory system h = tunnel width k = relaxation factor MO, = Mach number P = pressure S = control surface s = model wing span v — perturbation velocity normal to top and bottom walls w = perturbation velocity normal to side walls x = longitudinal dimension y = lateral dimension, see Fig. 3 z = vertical dimension, see Fig. 3 a = angle of attack r = wall porosity, % = perturbation velocity potential (nondimensionalized)