A numerical study of the influence of grid refinement and turbulence modeling on the flow field inside a highly loaded turbine cascade

A thorough numerical study was conducted to simulate the flow field inside a highly tended linear turbine cascade. The numerical investigation was foc used on the secondary flow field as well as on the prediction of the overal l design goals within reasonable accuracy limits. The influence of grid res olution was investigated in order to obtain detailed information about the requirements of a grid-independent solution. Three different two-equation t urbulence models were applied to two numerical grids of different resolutio n. Emphasis was laid on separating the influences of grid resolution and tu rbulence models. The Mach and Reynolds numbers as well as the level of free -stream turbulence were set to values typical of turbomachinery conditions. The computational study was carried out using a three-dimensional state-of -the-art block structured Navier-Stokes solver. The comparison of the numer ical results with experiments clearly revealed the different degree of agre ement between simulation and measurement. This paper describes the applicat ion of a modern pow solver to a rest case that is relevant for practical tu rbomachinery design purposes. The agreement between the experiments and the results of the numerical study is good and in most cases well within the a ccuracy limits proposed by Strazisar and Denton (1995). It was found out th at the main effect on the quality of the computations is the resolution of the numerical grid. The finest grid used reached over one million points ha lfspan, showing clearly superior results compared with a coarser, though st ill fine grid. The influence of different turbulence models on the numerica lly obtained flow field was relatively small in comparison with the grid in fluence.