Effect of confinement on flow around a rotating elliptic cylinder in laminar flow regime

TL;DR

This study numerically investigates how confinement, rotation, and Reynolds number influence vortex shedding, lift, drag, and moments around a rotating elliptic cylinder in laminar flow, revealing that vortex suppression is not achieved within the studied parameters.

Contribution

It provides a detailed parametric analysis of flow around a rotating elliptic cylinder under confinement, highlighting the effects on vortex patterns and force coefficients in laminar regimes.

Findings

Vortex shedding persists despite confinement and rotation.

Autorotation becomes prominent at lower rotation rates and higher confinement.

Force coefficients vary significantly with Reynolds number, confinement, and rotation.

Abstract

The flow phenomena around a rotating elliptic cylinder in a channel is studied numerically. The value of the confinement parameter \beta is varied as \frac{1}{k}, where k = 2, 4, 6, and 8 respectively, to demonstrate the vortex-shedding patterns around the cylinder in the downstream wake. The non-dimensional rotation rate \alpha takes up 0.5, 1, and 2 as its value. Additionally, the Reynolds number (\textit{Re}) based on the cylinder diameter is taken to be 50, 100, and 150 respectively. A parametric study is performed to explain the changes in drag coefficient \textit{(C_{D})}, lift coefficient \textit{(C_{L})}, and moment coefficient \textit{(C_{M})} with variations of \beta, \alpha, and \textit{Re}. The Fast-Fourier transform (FFT) of the time-periodic lift signals is presented to understand the shedding frequency characteristics, and the \textit{C_{M}} values are analyzed for cases of autorotation. Despite the introduction of significant confinement and cylinder rotation, complete suppression of vortex shedding is not observed for the considered parameter space. Autorotation is observed and becomes prominent with decrease in non-dimensional rotation rate and increase in confinement and Reynolds number.