NONLINEAR AERODYNAMICS OF CONICAL DELTA WINGS.

Abstract

Steady, inviscid, supersonic flow past conical wings is studied within the context of irrotational, nonlinear theory. An efficient numerical method is developed to calculate cones of arbitrary section at incidence. The method is fully conservative and implements a body conforming mesh generator. The conical potential is assumed to have its best linear variation inside each cell; a secondary interlocking cell system is used to establish the flux balance required to conserve mass. In regions of supersonic cross flow, the discretization scheme is desymmetrized by adding the appropriate artificial viscosity in conservation form. The algorithm is nearly an order of magnitude faster than present Euler methods. It predicts known results as long as the flow Mach numbers normal to the shock waves are near 1; qualitative features, such as nodal point lift-off, are also predicted correctly. Results for circular and thin elliptic cones are shown to compare very well with calculations using Euler equations. This algorithm is then implemented in the design of conical wings to be free from shock waves terminating embedded supersonic zones adjacent to the body. This is accomplished by generating a smooth cross-flow sonic surface by using a fictitious gas law that makes the governing equation elliptic inside the cross-flow sonic surface. The shape of the wing required to provide this shock-free flow, if such a flow is consistent with the sonic surface data, is found by solving the Cauchy problem inside the sonic surface using the data on this surface and, of course, the correct gas law. This design procedure is then demonstrated using the simple case of a circular cone at angle of attack.