22nd Congress of International Council of the Aeronautical Sciences, Harrogate, UK, 28 August - 1st September, 2000
Paper ICAS 2000-2.6.2

NUMERICAL INVESTIGATION OF THREE-DIMENSIONAL TRANSONIC FLOW WITH LARGE SEPARATION

M. A. Leschziner (1), H. Loyau (2)
(1) Queen Mary and Westfield College, University of London, UK; (2) Aircelle, Harfleur, France

Keywords: numerical investigation, three-dimensional transonic flow, separation

Shock-induced separation is an extreme manifestation of strong shock/boundary-layer interaction. It is of substantial engineering interest in the context of transonic wings and turbomachine blades, because it alters significantly the operational characteristics of the component in question. Predicting this interaction is challenging, both from a numerical and turbulence-modelling point of view, especially when the flow is highly threedimensional. This paper reports a computational study in which the performance of non-linear eddy-viscosity models is investigated when applied to a physically highly complex case of shock-induced separation in a duct flow over a swept bump inclined at 60o to the duct axis, followed by a shock-controlling second throat. The bump generates a skewed shock which interacts sensitively with the boundary layers on all four walls and causes extensive separation, strong transverse motion and highly complex topological flow features at the walls. The computations show that non-linear models yield a significantly more sensitive response of the boundary layers to the shock. This results in a better representation of the primary interaction processes, but also in excessively large transverse motion and hence insufficient rate of post-shock flow recovery. This is qualitatively consistent with observation in nominally 2D conditions, though the effect is much more pronounced in the present 3D case.

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