Flow Characteristics of Elastically Mounted Slit Cylinder at Sub-critical Reynolds Number

TL;DR

This study numerically investigates how different slit shapes and configurations on a cylinder influence vortex-induced vibrations and flow characteristics at sub-critical Reynolds number, revealing flow stabilization and VIV suppression mechanisms.

Contribution

It introduces the effects of various slit geometries and angles on VIV suppression and flow dynamics, providing new insights into flow control using slit modifications.

Findings

Slits help suppress VIV by stabilizing the wake.

Parallel slit significantly alters flow energy distribution.

Optimal slit angle enhances VIV suppression, beyond which effectiveness declines.

Abstract

The present work numerically investigates vortex-induced vibrations (VIV) of a two-dimensional circular cylinder with an axisymmetric slit at Reynolds number 500. The study examines the effects of slit shape (i.e., converging, diverging, and parallel slits), the effect of slit-area ratios, slit-width, and its angle with the freestream velocity on aerodynamic forces, vibration response, and associated flow characteristics. The results demonstrate that the addition of the slit assists the VIV suppression by adding an extra amount of flow to the main flow. It results in the stabilized wake with the pressure recovery downstream of the cylinder and causes a reduction in the lift force over the cylinder. Also, there exist different shedding patterns associated with different slit shapes. Proper Orthogonal Decomposition (POD) of the flow field suggests that among all the three slits, the parallel slit heavily modifies the flow behind the cylinder by distributing the amount of energy to a large number of modes as compared to other slits (converging slit and diverging slit), where the most of the energy is contained in a couple of modes. Further, increasing the slit angle (for parallel slit) with respect to the freestream increases the slit effectiveness up to a specific value of slit-angle and beyond that starts to affect the VIV suppression adversely. Observations for the effect of slit-width are also reported from the perspective of suppression of VIV.