An Investigation on Suppression of Vortex Instabilities for Flow Past a Bluff Body Using a Passive Device

Abstract

The present paper aims at investigating the effectiveness of using a passive device on the suppression of vortex instabilities during a fluid flow past a bluff body. A study of fluid flow parameters for the flow past a bluff body fitted with straight fins and helical strakes is presented. A three dimensional numerical investigation is performed on the bluff body for different designs of the fins and helical strakes. A circular cylinder of a diameter of 4cm is used as bluff body. The simulation is carried out for a water flow past a stationary cylinder with Reynolds number 28000. A numerical simulation was performed in a three dimensional computational domain using RANS equations and SST k-ω turbulence model. To reduce the frequency of the vortex shedding, the bluff body is attached with a passive device. The investigation observed that the attachments of straight fins and helical strakes on the surface are found to be highly effective in diminishing the vortex instabilities formed around the structure.The changes in the flow field are analyzed by observing the changes in flow parameters like Drag force and Strouhal number. The results were found to be in reasonable agreement with the available data in the literature. The use of helical strakes largely reduces Vortex induced vibrations (VIV) so that they can be used for the protection of underwater cables used in offshore structures.