Direct Numerical Simulation of Turbulent Plane Couette-Poiseuille Flows: Effect of Mean Shear Rate on the Near-Wall Turbulence Structures

Abstract

Direct numerical simulations (DNSs) of the fully developed turbulent flow between two parallel walls driven by a combination of a mean pressure gradient and the streamwise movement of one of the walls, i.e., turbulent Couette-Poiseuille flow, were carried out. The mean velocity gradient on the moving wall was reduced from that of an ordinary Poiseuille-type flow to almost zero. The turbulence statistics including the stress anisotropy and the budgets of the turbulence energy and Reynolds stresses are presented. The instantaneous flow fields visualized reveal that the structure of the near-wall turbulence under a weak mean shear does not exhibit any elongated streaks and is much different from that of the sheared wall layers.

Initial relaxation of spatially evolving turbulent channel flow with blowing and suction

“…Figure 8 shows the logarithmic velocity profiles at several representative downstream locations, together with DNS data. 6,22 As seen in prior experimental and numerical studies, 6,7 an upward shift of the logarithmic velocity profile caused by blowing and a downward shift by suction are clearly displayed.…”

“…Figure 6 plots mean velocities at six streamwise locations. The periodic DNS results of the unperturbed turbulent channel flow 22 and the asymptotic wall blowing and suction 6 are included for comparison. At the inflow region, the streamwise velocity shows good agreement with the periodic DNS.…”

“…At the inflow region, the streamwise velocity shows good agreement with the periodic DNS. 22 After the application of blowing and suction, the core region has a slow response to the wall blowing and suction. However, the time-mean velocity near the wall adjusts quickly to the perturbation (see Fig.…”

Modulation of Near-Wall Turbulence Structure with Wall Blowing and Suction

“…Figure 11 shows the AIM for the Reynolds stress tensor at inflow. The invariant data from a homogeneous channel flow DNS of Kuroda et al 28 are also included for comparison. The present data show all of the characteristics of the near-wall turbulence anisotropy and are in good agreement with the temporal DNS data.…”

“…The present data show all of the characteristics of the near-wall turbulence anisotropy and are in good agreement with the temporal DNS data. 28 Without blowing and suction, turbulence in a plane channel flow varies from a two-component turbulent state near the wall to a nearly isotropic state in the core region. At around the boundary of the viscous sublayer, the anisotropy tensor is closest to the one-component state.…”