Turbulent states in plane Couette flow with rotation

TL;DR

This study investigates how rotation affects turbulence in plane Couette flow, revealing non-monotonic torque behavior with rotation and identifying different flow structures at varying Reynolds numbers.

Contribution

It provides new insights into the impact of rotation on turbulent flow states and distinguishes between 2D and 3D vortex-dominated regimes at different Reynolds numbers.

Findings

Torque varies non-monotonically with rotation number.

Maximum flow response linked to 2D vortices at moderate Re.

Higher Re shows a second maximum with 3D flow structures.

Abstract

Shearing and rotational forces in fluids can significantly alter the transport of momentum.A numerical investigation was undertaken to study the role of these forces using plane Couette flow subject to rotation about an axis perpendicular to both wall-normal and streamwise directions. Using a set of progressively higher Reynolds numbers up to Re = 5200, we find that the torque for a given Re is a non-monotonic function of rotation number, Ro. For low-to-moderate turbulent Reynolds numbers we find a maximum that is associated with flow fields that are dominated by downstream vortices and calculations of 2-d vortices capture the maximum also quantitatively. For higher shear Reynolds numbers a second stronger maximum emerges at smaller rotation numbers, closer to non-rotating plane Couette flow. It is carried by flows with a markedly 3-d structure and cannot be captured by 2-d vortex studies. As the Reynolds number increases, this maximum becomes stronger and eventually overtakes the one associated with the 2-d flow state.