A Navier Stokes Computer Code for Theoretical Investigations on the Applicability of Various Turbulence Models for Flow Prediction Along Turbine Blades

Abstract

The quality of theoretical flow prediction in turbomachines is strongly influenced by the modeling of the turbulent fluctuations. These fluctuations are generated by various secondary flow mechanisms, the swirl of the flow occuring in blade channels and the curvature of the streamlines. Furthermore, the character of turbulence can become highly anisotropic indicating that the well known algebraic and two-equation k-ε type models might become unserviceable. The present paper deals with the validation of a fully implicit 2-D steady-state Navier-Stokes algorithm and the comparison of the applicability of various turbulence models for predicting the flow along the blades of a turbine nozzle. In the first section a short review is given on the basic numerical assumptions of the used computer code and on the employed two layer algebraic, one- and two-equation turbulence models. The influence of the fully implicitly formulated transport equations for the turbulent quantities, especially the influence of the discretization of the production and dissipation terms on the stability of the numerical scheme is pointed out. The validation of the numerical algorithm is done for an inviscid flow through the Hobson 2 impulse cascade, for the turbulent flow over a flat plate and for the flow through a turbine stator channel. In a last section results obtained from calculations for a subsonic turbine stator flow inside and downstream of the blade passage with several turbulence models are presented. The apparent differences, especially in the distribution of the total pressure loss downstream of the trailing edge are discussed.