CFD-Based Approximation Concepts for Aerodynamic Design Optimization with Application to a 2-D Scramjet Vehicle.

摘要

Approximation concepts, which are gaining popularity in structural optimization, offer the potential of providing the accuracy of a high-fidelity 'detailed' analysis model at greatly reduced computational cost. This is because the detailed model is used only to'fine tune' a much cheaper 'approximate' model which is then used by the optimizer. The test problem is the optimization of a 2-D scramjet vehicle flying at Mach 6.0 at 30 km altitude. The objective function is net thrust. The following approximation concepts were used: Taylor series approximation to wall pressures and inlet plane flow properties; and Haftka's Global-Local Approximation (GLA) applied to the same variables. It is shown that a modification must be made to the formulation of the approximation concepts to allow for the changing CFD grids. All correction factors are applied not to the CFD grid points, but to a constant, dense, non-dimensionalized 'correction point' grid system. In flow regions devoid of shocks or other discontinuous phenomena (such as in the scramjet nozzle region), this is the only major modification needed.