The Effect of Near-Wall Vortices on Wall Shear Stress in Turbulent Boundary Layers

Abstract

The objective of the present study is to explore the relation between the near-wall vortices and the shear stress on the wall in two-dimensional channel flows. A direct numerical simulation of an incompressible two-dimensional turbulent channel flow is performed with spectral method and the results are used to examine the relation between wall shear stress and near-wall vortices. The two-point correlation results indicate that the wall shear stress is associated with the vortices near the wall and the maximum correlation-value location of the near-wall vortices is obtained. The analysis of the instantaneous diagrams of fluctuation velocity vectors provides a further expression for the above conclusions. The results of this research provide a useful supplement for the control of turbulent boundary layers.

Computational Parametric Study of the Axial and Radial Clearances in a Centrifugal Rotary Blood Pump

“…For case Ax 0.5 , the shear stress is far lower because shear stress is inversely proportional to clearance size where flow is laminar35. For case Ax 1.0 , however, large vortices can be observed in Figure 5(c), the flow is no longer laminar and shear stress is high due to the near wall large scale vortices36,37 which inversely affect the efficiency.…”

Two-Point Statistics of Coherent Structure in Turbulent Flow

“…This method is expected to be applied to detecting near-wall streamwise vortices based on wall information in turbulent shear flows with complex boundaries. Guo and Li (2010) performed a two-dimensional DNS of an incompressible two-dimensional turbulent channel with spectral method to examine the relation between wall shear stress and near-wall vortices [37]. Two-point correlation between the spanwise vorticity and the wall shear stress was calculated to explore the relation between these two variables.…”

“…This method is expected to be applied to detecting near-wall streamwise vortices based on wall information in turbulent shear flows with complex boundaries. Guo and Li (2010) performed a two-dimensional DNS of an incompressible two-dimensional turbulent channel with spectral method to examine the relation between wall shear stress and near-wall vortices [37]. Two-point correlation between the spanwise vorticity and the wall shear stress was calculated to explore Journal of Flow Control, Measurement & Visualization 2018) applied POD to two-dimensional PIV, together with a spatio-temporal coherence analysis to illustrate the downstream convection of the large-scale Q2/Q4 events, as the low-order signatures of the hairpin packets [38].…”