Abstract
This chapter explores the unsteady and transitional effects typically encountered in axial turbine cascades. This is achieved by focusing on linear and a nonlinear k-ɛ model and v2- f model and the capability of recent eddy-viscosity turbulence models. A comprehensive validation procedure of the numerical scheme is presented for three turbulence models — the linear low-Re k-ɛ model, the nonlinear low-Re k-ɛ model, and the v2- f model. These models demonstrate the necessity to take sufficient spatial and temporal resolutions into account. Next, the numerical simulations of a linear turbine cascade periodically disturbed by impinging cylinder wakes are evaluated. Comparisons with detailed boundary layer measurements exhibit that all models are able to reproduce important features associated with boundary layer transition and flow unsteadiness while general deficiencies can be identified on the blade pressure surface. It is noted that time-accurate effects of transition are best predicted with the v2- f model.
Published Version
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