The calculation of separation bubbles in interactive turbulent boundary layers

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Abstract
A viscous–inviscid interaction procedure is presented for computing incompressible separation bubbles in two-dimensional flows. The analysis consists of the solution of the inviscid-flow equations with a conformal-mapping method and the solution of the boundary-layer equations with an inverse procedure. The boundary-layer equations employ the Cebeci–Smith algebraic eddy-viscosity formulation. The coupling between the inviscid and boundary-layer equations is established through the Hilbert integral by using Veldman's suggestion. An empirical method is used to calculate the location of transition, which is found to play a key role in predicting the behaviour of separating flows. Numerical solutions are presented for transitional bubbles on an NACA 663-018 airfoil at two angles of attack for a chord Reynolds number of 2 × 106. Comparisons wth experiment show that the flow properties of the separation bubbles can be predicted very well with this procedure provided that an accurate estimate of transition location is made.