Temporal Evolution of Dominant Flow Structures in Turbulent Channel Flow

Summary

The flow of a viscous incompressible fluid in a plane channel is simulated numerically with the use of a computational code for the numerical integration of the unsteady three-dimensional Navier-Stokes equations. The numerical method is based on a mixed spectral-finite difference algorithm. The calculations in the two homogeneous directions (the streamwise and the spanwise) are performed in Fourier space and second-order finite differences are used in the direction orthogonal to the solid walls. A turbulent-flow database representing the turbulent statistically steady state of the velocity field through 10 viscous time units is assembled at a nominal friction Reynolds number ${\it Re}_{\tau}=180$ and the coherent structures of turbulence are extracted from the fluctuating portion of the velocity field with the use of the Proper Orthogonal Decomposition technique (POD). The temporal evolution of a number of the most energetic POD modes is visualized, unveiling the mechanisms of interaction between dominant flow structures in wall-bounded turbulent flows.