Modification of DDES-SA Model Using Helicity for Predicting Tip Leakage Flow
Delayed Detached Eddy Simulation(DDES)method based on the Spalart-Allmaras(SA)turbulence model,as a classical hybrid Reynolds-Averaged Navier-Stokes(RANS)and Large Eddy Simulation(LES)approach,has been widely applied in practical engineering.However,the DDES-SA model,while combining the advantages of RANS and LES methods,still exhibits certain limitations in achieving the desired prediction accuracy in the field of turbomachinery.In this study,helicity is introduced to modify the traditional DDES-SA model.By accurately identifying the streamwise vortex core using helicity,the excessive turbulent viscosity in the vortex core is reduced,leading to a significant improvement in the predictive capability of the DDES-SA model for tip leakage flow.Numerical simulations of simplified rotor tip leakage flow are performed using the original and helicity-based modified DDES-SA methods,with LES results serving as a benchmark,to assess the predictive performance of the modified DDES-SA method for leakage flow.The results demonstrate that the modified DDES-SA method provides predictions closer to the LES results,and it offers more accurate vortex core strength and unsteady characteristics,significantly enhancing its predictive capability for rotor tip leakage flow.
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