Dragica Jošt attended ANSYS Conference & 10th Austria Users’ Meeting 2015 in Vienna ACCUSIM group participated with the presentation:
Improvement of efficiency prediction for axial turbines with advanced turbulence models
Authors: D Jošt, A Škerlavaj, P Mežnar, M Morgut and E Nobile
Abstract. Numerical prediction of an efficiency of two axial turbines is presented. At first steady state analysis by different turbulent models of a 6-blade Kaplan turbine for middle head was performed. For small and optimal angles of runner blades the efficiency was quite accurately predicted, but for maximal blade angle the discrepancy between calculated and measured values was quite large. By transient analysis, especially when the Scale Adaptive Simulation Shear Stress Transport (SAS SST) model with zonal Large Eddy Simulation (ZLES) in the draft tube was used, the efficiency was significantly improved. The improvement was at all operating points, but it was the largest for maximal discharge. The reason was better flow simulation in the draft tube. The second case was an extremely low head 3-blade bulb turbine for which steady state analysis entirely failed to predict the efficiency due to incorrect results in the draft tube. Again good agreement with measurements was obtained by SAS SST ZLES model. For both cases details about turbulent structures in the draft tube obtained by SST, SAS SST and SAS SST with ZLES are illustrated in order to explain the reasons for differences in flow energy losses obtained by different turbulence models.