基于螺旋度改进的DDES-SA模型预测叶尖泄漏流动

Modification of DDES-SA Model Using Helicity for PredictingTip Leakage Flow

基于Spalart-Allmaras(SA)湍流模型的延迟脱体涡模拟(Delayed Detached Eddy Simulation, DDES)方法作为一种经典的混合雷诺平均(RANS)–大涡模拟(LES)方法,已被广泛应用。然而,DDES-SA模型虽结合了RANS及LES方法的优点,但在叶轮机领域的实际应用中仍存在局限性,难以达到期望的预测精度。本研究引入螺旋度对传统的DDES-SA模型进行修正,通过螺旋度精准识别流向涡核,减弱涡核处过高的湍流黏性,从而显著提升DDES-SA模型对叶尖泄漏流动的预测能力。本文采用改进前后DDES-SA对简化的叶轮机转子叶尖泄漏流动进行了数值模拟,以大涡模拟结果为基准,评估了改进前后的DDES-SA方法对泄漏流动的预测性能。结果表明,基于螺旋度改进的DDES-SA方法预测值和LES结果更接近,并能提供更准确的涡核强度及非定常特性,显著提升了其对叶尖泄漏流的预测能力。

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.