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TEMPORAL DYNAMICS OF VORTICAL STRUCTURES IN TURBULENT CHANNEL FLOW

Giancarlo Alfonsi
Fluid Dynamics Laboratory, Universita della Calabria, Via P. Bucci 42b, 87036 Rende (Cosenza), Italy

Leonardo Primavera
Fluid Dynamics Laboratory, Universita della Calabria, Via P. Bucci, Cubo 42b, 87036 Rende (Cosenza), Italy

Abstract

The temporal dynamics of vortical structures in the wall region of turbulent channel flow is investigated. The Navier-Stokes equations are integrated numerically at friction Reynolds number Reτ = 180, using a computational code that utilizes a mixed spectral-finite difference technique and following the DNS approach.
A turbulent-flow database representing the turbulent statistically steady state of the velocity field through 10 viscous time units is computed and the method of the "imaginary part of the complex eigenvalue pair of the velocity-gradient tensor" is applied for vortex eduction.
Flow visualizations are provided that support a visual description of the evolutionary process with time of single and multiple hairpin vortical structures in the wall layer.