Evaluation of XY-SAS model for separated flows
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摘要: XY-SAS(Xu-Yan-Scale Adaptive Simulation)模型是一种新的基于平均涡量的一方程SAS类模型,不但解决了分离涡模拟DES(Detached Eddy Simulation)的雷诺平均N-S方程RANS(Reynolds Averaged Navier-Stokes)-大涡模拟LES(Large Eddy Simulation)交界面问题,而且计算量远小于早期SAS.通过对XY-SAS模型的机理分析,认为该模型克服了早期SAS模型预测的湍流能谱在高波数衰减不足的缺陷,并在分析的基础上对该模型进行了改进,取消了其限制器.选用平板边界层和方柱绕流作为算例,进一步研究了该模型对于稳态流动和大分离流动的性能,数值模拟结果同实验值符合良好,证明XY-SAS模型自身完备,是预测稳态流动和大尺度分离流动的有效方法,实现了涡粘性系数根据当地流动状态动态地自适应调整和光滑过渡.Abstract: Xu-Yan-scale adaptive simulation (XY-SAS)is a new one-equation scale-adaptive simulation model proposed on the basis of average vorticity. It resolves the reynolds average navier-stokes(RANS)-large eddy simulation(LES) interface problem in detached eddy simulation (DES) with much smaller computation cost compared with pioneer SAS model. It was analyzed that XY-SAS model can provide proper damping of resolved turbulence at high wave number end of the spectrum compared with pioneer one. The limiter was removed based on mechanics analysis and this model was improved. Flat plate boundary layer and square cylinder were chosen as test cases for further evaluation of XY-SAS. The numerical results agree well with the experimental data, which proves that XY-SAS is an effective method for large scale separation flow and the model itself is complete. The model viscosity is determined adaptively according to the local flow behavior .A smooth transition is achieved from RANS to LES region.
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