Suppression of vortex shedding using a slit through the circular cylinder at low Reynolds number

TL;DR

This study investigates how introducing a slit in a circular cylinder can passively suppress vortex shedding at low Reynolds numbers, with flow behavior depending on slit width and Reynolds number, using experimental and reduced order modeling techniques.

Contribution

It demonstrates that a slit in the cylinder effectively suppresses vortex shedding in laminar flow regimes and analyzes flow bifurcations and vortex structures using POD and DMD.

Findings

Vortex shedding is suppressed with increasing slit width ratio S/D.

Flow remains periodic for all S/D, with reduced lift coefficient rms values.

Flow bifurcations occur at specific Reynolds numbers for certain slit widths.

Abstract

The present article aims to study the suppression of vortex shedding using a passive flow control technique (slit through a circular cylinder) in the laminar regime (Re=100-500). The slit width ratio S/D (slit width/diameter) on the modified cylinder plays an essential role to control the vortex shedding. The additional flow through the slit leads to the suppression of the global instability and vortex shedding, whereas a large amount of flow through the slit drastically alters the behavior of vortex shedding. The nature of vortex shedding remains periodic for all S/D, and the root mean square (rms) value of the lift coefficient decreases (in turn, vortex shedding suppression) with S/D up to Re = 300. For the range Re > 300, the root mean square (rms) value of the lift coefficient decreases up to S/D < 0.15, and the flow exhibits periodic vortex shedding, while the root mean square (rms) increases beyond S/D > 0.15 due to irregular vortex shedding downstream of cylinder. The variation of the Re for the S/D=0.20 shows bifurcation points where the flow changes its behavior from symmetric to asymmetric solution at Re=232 and again becomes symmetric at Re=304. The unsteady flow analysis over the modified cylinder also indicates the suppression in the vortex shedding; however, the analysis provides the qualitative property of suppression. The reduced order modeling, i.e. Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD), is utilized to quantify suppression and investigate the dominant vortical structure for slit through the cylinder.