Shear-layer dynamics at the interface of parallel Couette flows

TL;DR

This study provides a detailed analysis of shear-layer dynamics at the interface of parallel Couette flows, highlighting how turbulence and flow structures vary across the interface and differ from standard Couette flow.

Contribution

It offers new insights into the flow quantities, turbulence transport, and flow structure topology at the interface of co-flowing plane Couette flows, comparing them with standard flows.

Findings

Enstrophy exhibits a sharp jump at the interface.

Co-flowing system shows greater vorticity and kinetic energy than standard Couette flow.

Flow structures analyzed using flow invariants reveal detailed topology differences.

Abstract

This article aims to make a detailed analysis of co-flowing plane Couette flows. Particularly, the variation of flow quantities from the turbulent to non-turbulent region is studied. While the enstrophy exhibits a sharp jump, the other quantities (e.g., mean velocity, Reynolds normal stress, and kinetic energy) show a continuous variation across the interface. The budget analysis of Reynolds normal stresses reveals that the terms playing a key role in turbulence transportation vary depending on the Reynolds normal stress under study. The terms production, diffusion, and redistribution play an important role in streamwise Reynolds stress {\dh}u0u0 {\TH}. In the spanwise Reynolds stress {\dh}v0v0 {\TH}, the diffusion terms play a significant role. In the wall-normal Reynolds stress {\dh}w0w0 {\TH}, only the redistribution term is significant. The influence of one flow over another in the co-flow state was observed through the additional mean velocity and Reynolds normal stress found in the system compared to a standard plane Couette flow (pCf). Comparing the co-flow system with a conventional pCf system, the former exhibits greater vorticity, vortex stretching, and kinetic energy. A detailed analysis on the geometry and topology of flow structures was studied using flow invariants.