尾流的双尺度简化模型及其大涡模拟建模  

Two-Scale Simplified Model of Wake and Its Large Eddy Simulation Modeling

作　　者：赵宏凯 方乐[2,3] ZHAO Hong-Kai;FANG Le(School of Energy and Power Engineering,Beihang University,Beijing 100191,China;Ecole Centrale de Pekin,Beihang University,Beijing 100191,China;International School of Aero-Engine,Research Institute of Aero-Engine,Beihang University,Beijing 100191,China)

机构地区：[1]北京航空航天大学能源与动力工程学院,北京100191 [2]北京航空航天大学中法工程师学院,北京100191 [3]北京航空航天大学航空发动机国际学院,北京100191

出　　处：《工程热物理学报》2021年第6期1446-1454,共9页Journal of Engineering Thermophysics

基　　金：国家自然科学基金资助项目(No.11772032,No.11572025)。

摘　　要：叶轮机中存在着复杂的湍流流动结构,如何准确地模拟湍流流动一直是工程界关注的核心问题。由于湍流在大部分区域都处于强非均衡态,根据均衡能量传输假设建立起来的RANS湍流模型和大涡模拟亚格子模型都不再适用。非均衡湍流的一个经典的模型流动是尾流,但通常意义上的尾流往往是无数不同尺度相互作用的结果,难以进行简化分析。本文构造了一个极度简化的双尺度尾流模型进行了直接数值模拟(DNS),结果显示在转捩前期就存在反向的非均衡能量传输。分别采用各种传统的RANS湍流模型和大涡模拟亚格子模型进行了数值模拟,发现各种模型都无法准确预测尾流转捩。在考虑非均衡能量传输机制后,通过流向速度梯度扭率构造的理性亚格子应力模型可以使大涡模拟模拟的转捩位置相对于标准Smagorinsky模型有所改善;不采用涡粘假设的改进速度增量(IVI)模型可以得到更加接近DNS的结果。这些结果为湍流模型进一步的改进提供了思路。There are complex turbulent flow structures in turbomachines.How to accurately simulate turbulent flow has always been the core issue of the engineering community.Since turbulence is under a strong non-equilibrium state in most areas,the RANS turbulence model and the large eddy simulation sub-grid model based on the assumption of equilibrium energy transfer are no longer applicable.A classic model of non-equilibrium turbulence is the wake,but the wake in the usual sense is often the result of the interaction of countless different scales,which is difficult to simplify analysis.We constructed an extremely simplified two-scale wake model for direct numerical simulation(DNS),and the results showed that there was a reverse and unbalanced energy transmission in the early stage of transition.Numerical simulations were carried out using various traditional RANS turbulence models and large eddy simulation subgrid models,and it was found that all the models could not accurately predict the wake transition.After considering the non-equilibrium energy transmission mechanism,the rational subgrid stress model constructed by the skewness of longitudinal velocity gradient can improve the prediction of transition position of the large eddy simulation results compared with the standard Smagorinsky model.The improved velocity increment(IVI)model,without using the vortex viscosity assumption,can get results closer to DNS.These results provide ideas for further turbulence modeling.

关 键 词：尾流 大涡模拟 非均衡湍流 

分 类 号：O357.5[理学—流体力学]