Characteristics of Fine Scale Eddy Clusters in Turbulent Channel Flows
Abstract
Direct numerical simulations of turbulent channel flows up to Re_τ=1270 have been conducted to investigate characteristics of vortex clusters in the logarithmic region. Vortex clusters are organized by coherent fine scale eddies (hereafter CFSEs). These structures contribute streamwise velocity deficit and involve relatively high dissipation rate of turbulent kinetic energy in the outer region, especially in the logarithmic region. Temporal development of spatial distribution of CFSEs reveals that clusters of the CFSEs are sequentially observed in the outer region. The CFSEs in the large-scale motion have relatively strong swirling motion compared with those in the whole flow field. Strain rate acting on CFSEs in the low-momentum regions is investigated by evaluating the strain rate tensor at the centers of the CFSEs, which shows that stronger stretching and compression act on the CFSEs in the low-momentum regions. Therefore, the cluster of CFSEs generates the high dissipation rate of turbulent kinetic energy and large Reynolds shear stress in the logarithmic region.
- Publication:
-
APS Division of Fluid Dynamics Meeting Abstracts
- Pub Date:
- November 2004
- Bibcode:
- 2004APS..DFD.EA005K