Numerical simulation of unsteady and transitional flows pertaining to turbine cascades

Focusing on a linear and a non-linear k-epsilon model as well as on the nu(2)-f model, the capability of recent eddy-viscosity turbulence models to capture unsteady and transitional effects typically encountered in axial turbine cascades is investigated in this paper. First, a comprehensive validation procedure of the numerical scheme is presented for three challenging test cases, demonstrating the necessity to take sufficient spatial and temporal resolutions into account. Numerical simulations of a linear turbine cascade periodically disturbed by impinging cylinder wakes are evaluated next, As comparisons with detailed boundary layer measurements show, 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. For this test case, time-accurate effects of transition are best predicted with the nu(2)-f model.