Stability analysis of the flow around a cylinder fitted with helical strakes

Abstract

Helical strakes are the most employed devices to mitigate or suppress vortex shedding behind circular cylinders. Although several investigations have been performed in order to predict the performance of these devices, proving its efficiency in specific configurations, little is understood regarding the physical mechanisms leading to the efficiency of these devices. The present work addresses this question from a global linear instability analysis point of view. Direct Numerical Simulation, three-dimensional global (TriGlobal) and Floquet stability analysis of the flow around a cylinder fitted with helical strakes is performed at low and moderate Reynolds number in order to understand more deeply the flow instabilities and physical mechanisms that mitigate and suppress the vortex-shedding.