Channel-confined flow-induced rotation of an asymmetrically confined square cylinder in a two-dimensional laminar flow regime

Abstract

This study focuses on the flow-induced rotational characteristics of an asymmetrically confined square cylinder in a channel for various engineering applications. We consider the classical, fully developed channel flow problem to numerically study the flow-induced rotation (FIR) of a square cylinder in a two-dimensional laminar flow regime. We employ our in-house computational fluid dynamics solver, based on the hybrid Lagrangian–Eulerian method, for the present study. For the very first time, we identify seven distinct rotational modes by investigating FIR for a wide range of Reynolds number Re(1−150) and eccentricity ε (0, 1/3, 2/3). This paper reports the combined effects of Re and ε on the FIR characteristics in terms of rotational modes, accompanying flow structures, and pertinent engineering parameters. At low Re, the shear-induced torque dominates over the pressure-induced torque, whereas with an increase in Re, the pressure-induced torque gradually outweighs the shear-induced torque. Thus, we observe a smooth transition in the direction of rotation from clockwise to counterclockwise with increasing Re. This study involves a detailed discussion of the flow physics and moment-generating mechanisms for four intriguing rotational modes, including Autorotation, Mono-harmonic Oscillation, Bi-harmonic Oscillation, and Reversal Autorotation. The current study has applications in micro energy-harvesting, vortex generation, and microfluidic mixing.