低阶格式在大涡模拟计算中的适用性

采用三维Taylor-Green涡作为研究对象,利用工程中常用的低阶数值格式,研究格式本身的数值误差对大涡模拟计算的影响.结果表明:三种数值格式的数值耗散行为都与亚格子模型行为类似,即在小雷诺数下,流场比较光滑时,耗散很小,当雷诺数增加,流动转捩为湍流,流场梯度增大,耗散显著增大.对于MUSCL格式和二阶有界中心格式,在高雷诺数下,亚格子尺度模型没有明显改善计算结果,但也没有使计算结果恶化.中心格式相比其它两种格式,数值耗散最小,但是在高雷诺数湍流情况下,中心格式的数值耗散仍然主导了能量的耗散,再添加亚格子模型,计算结果反而变得稍差.对于工程中的低阶格式而言,采用中心格式计算大涡模拟是比较好的选择,而且在计算不存在稳定性问题时,采用不添加亚格子模型的隐式大涡模拟效果更好.

Suitability of Low-order Numerical Schemes in Large Eddy Simulations

Several low-order numerical schemes were evaluated for their suitability in large-eddy simulations based on 3D Taylor-Green vortex, with and without a subgrid-scale model. It shows that dissipation characteristics of three numerical schemes used are similar to a subgrid-scale model. At lower Reynolds numbers, flow fields are relatively smooth, numerical dissipation is lower; As Reynolds number increasing, transition to turbulence occurs and numerical dissipation grows greatly. For MUSCL and bounded centered schemes, subgrid-scale model has a little influence on results at high Reynolds numbers. The second-order central scheme exhibits lower dissipation, but at higher Reynolds numbers numerical dissipation still dominates total energy dissipation of flow. With an explicit subgrid-scale model the results even become worse. Therefore, for large eddy simulations in engineering, the second order central scheme is suitable, particularly without an explicit subgrid-scale model.