CONFIGURATIONS WITH SPECIFIED SHOCK WAVES

H. Sobitczky

DLR German Aerospace Research Establishment, Gottingen. Germany

8.1 Introduction

Supersonic flow elements arc valuable components for the development of new aerodynamic de­sign concepts for efficient high speed flight vehicles Among these elements, flows with oblique shocks may be used to shape socalled waveriders, which are almost classical cases where the component may already form a high lift-over-drag (UD) configuration (96). (97). In the past dec­ades. the mathematical models of plane or «asymmetric supersonic flow fields with shocks have been used to create a number of simple lest cases for experimental investigation, long before nu­merical flow analysis methods and large computers were available

Today wc have various invisetd and viscous CFD analysis methods operational to investigate the aerodynamic performance of airfoils, wings and 3D configurations in design and off-design conditions. Waveriders arc ideal test cases for numerical methods simulating inviscid compressible flow: Special known shock patterns occur on relatively simple geometries at design conditions. In this situation we may flunk about creating more general and perhaps more efficient waveriders by new design methods, mature CFD analysis will verify the predicted inviscid flows and help to analyze design and off-design conditions performance, allowing for substantial reductions in systematic wmdtunnel testing.

Inverse aerodynamic design is an approach to obtain configuration elements compati­ble with certain desired performance characteristics In supersonic and hypersonic flow, the shock wave formed by the lifting body at the leading edge is carrying much of the information about lift wave drag and noise, which are key issues in applied supersonic aerodynamics. It seems a challenging task therefore to invert the design problem by controlling the bow shock

wave and find compatible body surfaces. Since the 1960’s wavender configurations arc con­structed from simple known plane or axisymmetric flow fields with oblique shocks, suitably cut by stream surfaces to provide special delta wings with sharp leading edges.

In this chapter wavender flows arc generated from given shock wave geometries. In the past years since Nonwetlcr’s first caret wing wavchders (98), plane 2D and axisymmetric conical flows have been used for the generation of lifting wings in supersonic flow, with the detailed іnviscid flow structure coming as a result with the geometric shape. In the recent years a revived interest (99) in these wavender* has emerged, to use them as baseline configurations with known aerodynamic performance at idealized design conditions, for further development and optimization using CFD as well as refined experimental techniques. Two new concepts (100] were presented for this purpose: ‘Osculating Cones* and ‘Inverse Euler Marching’ tech­niques, to obtain more general wavender geometnes than derived previously from plane or con­ical generating flows These concepts and applied work based on them are reported here in the following.

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