1997-10-01

Aerothermodynamic Design of Supersonic Channel Airfoils for Drag Reduction 975572

A supersonic channel airfoil (SCA) concept that can be applied to the leading edges of wings, tails, fins, struts, and other appendages of aircraft, atmospheric entry vehicles and missiles in supersonic flight for drag reduction is described. It is designed to be beneficial at conditions in which the leading edge is significantly blunted and the Mach number normal to the leading edge is supersonic. The concept is found to result in significantly reduced wave drag and total drag (including skin friction drag) and significantly increased L/D. While this reduction over varying flight conditions has been quantified, some leading edge geometries result in adverse increases in peak heat transfer rates.To evaluate the effectiveness of SCAs in reducing drag without paying any penalties in other areas like lifting capacity, heating rates or enclosed volume, the design space was studied in greater detail using MDO methods. A Design of Experiments (DoE) technique is used to search the design space efficiently for SCAs designed to operate at Mach 4 and 12 km altitude. The results from these numerical experiments, i.e. Navier-Stokes simulations assuming turbulent flow, are used to formulate analytical (polynomial) models for force coefficients and heat transfer rates using a Response Surface Methodology. These nonlinear models are then incorporated into a calculus-based optimization procedure to generate an optimal aerothermodynamic design for a 2 D supersonic channel airfoil. The improvements in aerothermodynamic performance for the optimized channel airfoil relative to a chosen baseline no-channel airfoil are determined and verified by a Navier-Stokes solution.

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