Assessing rotation/curvature corrections to eddy-viscosity models in the calculations of centrifugal-compressor flows

Abstract

Rotation and curvature (RC) effects on turbulence are expected to impact losses and flow structure in turbomachines. This paper examines two recent eddy-viscosity-model corrections devised to account for these effects: the Spalart and Shur (1997, "On the Sensitization of Turbulence Models to Rotation and Curvature," Aerosp. Sci. Technol., 1(5), pp. 297–302) correction to the model of Spalart and Allmaras (1994, "A One-Equation Turbulence Model for Aerodynamic Flows," Rech. Aerosp., 1, pp. 5–21) and the correction of Cazalbou et al. (2005, "Two-Equation Modeling of Turbulent Rotating Flows," Phys. Fluids., 17, p. 055110) to the (k,epsilon) model. The method of verification and validation is applied to assess the impact of these corrections on the computation of a centrifugal-compressor test case. First, a review of RC effects on turbulence as they apply to centrifugal compressors is made. The two corrected models are then presented. Second,the Radiver open test case (Ziegler K. U., Gallus, H. E., and Niehuis R., 2003, "A Study on Impeller Diffuser Interaction Part 1: Influence on the Performance," ASME J. Turbomach, 125, pp. 173–182) is used as a basis for the assessment of the two corrections. After a physical-consistency analysis, the Richardson extrapolation is applied to quantify the numerical errors involved in all the calculations. Finally, experimental data are used to perform validation for both global and local predictions. The consistency analysis shows that both corrections lead to significant changes in the turbulent field, in perfect agreement with the underlying theoretical considerations. The uncertainty analysis shows that the predictions of the global performances are more sensitive to grid refinement than they are to RC turbulence modeling. However, the opposite conclusion is drawn with regard to the prediction of some local flow properties: Improvements are obtained with the RC corrections, the best results being observed for the RC-corrected (k,epsilon) model.