低雷诺数翼型层流分离现象大涡模拟方法

Large eddy simulation method for the laminar separation phenomenon on low Reynolds number airfoils

为准确预测翼型低雷诺数条件下出现的层流分离流动现象,发展了基于结构化拼接网格的大涡模拟方法。控制方程为Favre滤波Naver-Stokes方程,并选用多种亚格子模型。空间离散采用AUSM格式以及高阶WENO格式,时间推进采用显式方法和隐式方法。以SD7003翼型在雷诺数60000及4°迎角下的层流分离流动为研究对象,对比分析了数值格式、亚格子模型、网格尺度对流场预测结果的影响。数值结果表明:划分的计算网格能够有效解析小尺度流动结构,基于隐式亚格子模型、采用AUSM格式和双时间步推进的大涡模拟方法能够准确预测流动分离、转捩、再附等复杂流动现象,计算得到的平均压强系数与雷诺应力分布与文献数据吻合较好。与转捩模式计算结果对比进一步表明:发展的大涡模拟方法能够准确预测翼型低雷诺数层流分离流动非定常演化过程,为下一步的研究工作建立了有效的数值模拟手段。

The large eddy simulation method based on structured patched mesh was developed to accurately predict the laminar separation phenomena under low Reynolds number conditions.The Favre averaged Navier-Stokes equations are solved,and various sub-grid scale models are utilized.The AUSM and high order WENO scheme are adopted for spatial discretization,and explicit and implicit methods are used for time integration.Through the simulation of the laminar separation flow around the SD7003 airfoil at Reynolds number 60000 and angle of attack 4°,the influence of numerical schemes,sub-grid models,and mesh resolution on the computed results were compared and analyzed.The computational results show that,the computational meshes are effective for resolving the small scale flow structures,and the implicit large eddy methodology which utilizes the AUSM scheme and the dual time method can predict the complex flow phenomena of separation,transition,and reattachment accurately.The computed averaged pressure coefficients and Reynolds stress agree well with the computational and experimental data in literatures.The comparison with the results of transition model further reveals that,the developed large eddy simulation method can accurately predict the unsteady evolution of laminar separated flow on low Reynolds number airfoils.The present study establishes an effective numerical simulation method for the future research.