An LES Wall Treatment with a Self-Sustaining Model

Li, J. An LES Wall Treatment With a Self-Sustaining Model. University of Wisconsin-Madison, 2023.

A wall model has been developed for coarse meshed wall-bounded LES flows, to provide fluctuating wall shear stress by modeling a significant rolling phenomenon in a turbulent boundary layer. The rolls massively exist in the near-wall region to facilitate mass and momentum exchange. By analyzing the DNS near-wall flow field, relationships of rolls to fluctuating wall shear stress are extracted and used to convert dynamic rolling information, which is traced by updating the self-sustaining processing equations, into fluctuating wall shear stress. The above relationships and effectiveness of conversion have been verified and shown to match the statistics of the DNS near-wall flow.

This wall model is applied to every wall-adjacent cell, providing the desired wall shear stress to the LES solver in each iteration step. To evaluate the model’s performance, a channel flow case is used, which includes verifying the force balance and checking the mean velocity profile. A comparison with a control group demonstrates improvements in near-wall fluctuations, TKE, and Reynolds stress. The velocity and total pressure contours confirm that this model provides more detailed fluctuations on walls. The test results on further mesh convergence and stretched grid indicate that the model performs reasonably well.