Viscous Effects and Truncation Effects in Axisymmetric Busemann Scramjet Intakes

Abstract

During Busemann intake design, two constraints have to be considered. First, caused by the displacement of the boundary layer, the pressure levels in a Busemann intake were higher (≈40%) than the values predicted analytically; these effects were labeled viscous effects. Second, truncating the flowfield also changed the properties of the classical Busemann flow; these effects were labeled truncation effects, and it can be distinguished between truncating the intake at the leading edge and at the rear side. To take into account viscous effects, the boundary-layer displacement thickness was calculated with an integral method and added to the inviscid Busemann contour. To quantify leadingedge truncation effects, an oblique shock at the leading edge was assumed, and the pressure at the intake exit was corrected with the continuity equation. The change in flow properties during the rear-side truncation was calculated with a stream-thrust analysis. The effects were separately investigated with Reynolds-averaged Navier-Stokes and Euler simulations, respectively. After the viscous correction, the deviation between numerically and analytically calculated pressure level was below 10%. When truncating the intake, the numerically calculated average pressure and temperature levels were within 1% of the analytical values.