AERODYNAMIC CHARACTERISTICS OF JETFLAPPED AIRFOILS IN GROUND EFFECT

The favorable aerodynamic characteristics of the jet flap are appreciably affected by the presence of a ground plane. A theory for the two dimensional jet-flapped airfoil in ground effect is presented in the paper. The basic flow equations are derived and it is shown that while the field equation is linear, the boundary conditions are not. By a conformal mapping, the original problem is con verted to one of an extremely simple geometry, and applying the appropriate kinematic and dynamic boundary conditions, the basic equation is derived. The singularities of the equation are identified and discussed; in the transform plane they consist of logarithmic terms at the trailing edge and simple polar terms, O(1/x), at the leading edge. In the case of no ground plane, the integro-differential equation derived by Spence follows directly from the equation developed here. The singularities are 'removed' by the addition of functions exactly satisfying the integrodifferential equation at the singular points. The remaining terms can be approximated and evaluated by a collocation process involving two Fourier Series. A matrix, whose inverse defines these Series, is developed, its elements being generated in a form suitable to digital computer techniques. (Author)