A numerical study of the side-wall effects on turbulent bands in channel flow at transitional Reynolds numbers

TL;DR

This study uses direct numerical simulations to examine how side-wall effects influence the behavior and decay of turbulent bands in channel flow at transitional Reynolds numbers, providing insights relevant for experimental turbulence research.

Contribution

It presents the first detailed numerical analysis of side-wall effects on turbulent bands at transitional Reynolds numbers, identifying critical Re thresholds and mechanisms for band decay.

Findings

Turbulent bands survive collisions with side walls above Re ~1000.

Bands decay below Re ~975, indicating a critical Reynolds number between these values.

Results inform experimental studies of turbulence in channel flows.

Abstract

We investigated the side-wall effects on turbulent bands in channel flow at transitional Reynolds numbers by direct numerical simulations using the open source spectral-element code Nektar++. The width-to-height aspect ratio of 50:1 is considered for this study. Our study shows that turbulent bands can survive the collision with the side wall above bulk Reynolds number of Re around 1000 but decay below Re around 975, i.e. the critical Reynolds number should be approximately between the two Reynolds numbers. We also discussed about the underlying mechanism for the decay of the band at low Reynolds numbers and potential effects of larger spanwise channel widths than that considered in our study. The results are informative for experimental studies of channel flow turbulence at transitional Reynolds numbers.