A source wake model for cascades of axial flow turbomachines

This work presents a computational model for the viscous flow through rectilinear cascades of axial turbomachinery. The model is based on modifications of the classical Hess & Smith panel method. The viscous effect of the attached flow portion is introduced by means of normal transpiration velocities obtained from the boundary layer calculations on the airfoil contour. At the separated flow portion, fictitious velocities semi-empirical normal velocities are introduced assuming a constant pressure in the wake. When the separation is not detected, it is possible to simulate the effect of the small wake near the trailing edge by using an injected flow on a distance based on the Gostelow (1974) fairing-in procedure. The numerical model presents two iteration cycles: the first one to find the separation point, and the second one to accomplish the viscous-inviscid interaction, in which the transpiration velocities and the flow injection are submitted to a relaxation process in order to guarantee the convergence of the method. Results for the pressure distributions, flow turning angles and lift coefficients are compared with experimental data for the model validation.

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