均匀各向同性湍流亚格子流场统计性质

Statistics characteristics of turbulence in homogeneous isotropic subgrid-scale turbulent flow

采用平顶帽与高斯这2种物理空间过滤器,对各向同性DNS湍流场进行了过滤处理,得到了各向同性湍流的亚格子流场(SGS)以及对应的可求解尺度流场,并对它们的基本性质进行了研究.结果表明:随着过滤宽度增大,SGS流场的湍动能逐渐增加,通过与谱截断过滤器所得的SGS流场能量结果对比,发现其与物理过滤器存在明显的差别.同时,SGS与F-DNS场的自相关以及积分时间尺度也都增加;不同于全尺度场的关系,SGS场的拉氏积分时间尺度大于欧拉的时间尺度,时间尺度之比也随着过滤宽度增加而逐渐减小至全尺度流场的比值.

talactical characteristics of subrgrid-scale（SGS）fluid was investigated by using two kinds of filters in physical spaces.The simulation results show that with increased filter width,the SGS kinetic energy increases,and as compared with the results of the Fourier sharp cutoff filter,quantitative difference was obviously observed between these corresponding SGS fields.Meanwhile,the autocorrelations and integral timescales of SGS and F-DNS both increases as filter width increases.Contrary to the relation in the full velocity field,in SGS turbulent field,Lagrangian integral time scale is larger than Eulerian integral time scale.The ratio of Lagrangian integral time scale to Eulerian integral time scale decreases as filter width increases and it approaches to the limit of full velocity field′s value when filter width reach the maximum.