The structure of the vorticity field in turbulent channel flow. Part 2: Study of ensemble-averaged fields
Abstract
Several conditional sampling techniques are applied to a data base generated by large-eddy simulation of turbulent channel flow. It is shown that the bursting process is associated with well-organized horseshoe vortices inclined at about 45 deg. to the wall. These vortical structures are identified by examining the vortex lines of three-dimensional, ensemble averaged vorticity fields. Two distinct horseshoe-shaped vortices corresponding to the sweep and ejection events are detected. These vortices are associated with high Reynolds shear stress and hence make a significant contribution to turbulent energy production. The dependency of the ensemble averaged vortical structures on the detection criteria, and the question of whether this ensemble-averaged structure is an artifact of the ensemble averaging process are examined. The ensemble-averaged pattern of these vortical structures that emerge from the analysis could provide the basis for a hypothetical model of the organized structures of wall-bounded shear flows.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- October 1984
- Bibcode:
- 1984STIN...8512317K
- Keywords:
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- Channel Flow;
- Separated Flow;
- Shear Stress;
- Simulation;
- Turbulent Flow;
- Vortices;
- Boundary Value Problems;
- Data Bases;
- Flow Velocity;
- Perturbation;
- Sampling;
- Space-Time Functions;
- Statistical Analysis;
- Fluid Mechanics and Heat Transfer