An Investigation of Wall and Back Pressure Effects in Transonic Interference.

摘要

An approximate method for the determination of tunnel wall interference on two-dimensional non-lifting supercritical airfoils is presented. The method assumes classical linearized subsonic interference theory applied to an airfoil whose thickness is increased so as to match the far field transonic velocity potential. The interference potential at the wing trailing edge is taken as the parameter controlling the shock location on the airfoil. Sample computations of circular arc airfoils in tunnels with solid, porous and slotted walls are shown to adequately predict the shock displacement produced by the wall constraints. Also presented is a numerical analysis, based on a shock fitting technique, for the determination of exact shape and location of imbedded shocks. With the analysis and accompanying numerical code some results are provided to show the sensitivity of back pressure perturbations on shock location. (Author)