Effect of apex angle on near wake vortex dynamics of triangular cylinders at intermediate Reynolds number

Abstract

A study of vortex dynamics is essential in understanding the behaviour of the forces acting in a flow. This is because super positioning of vortex flow on other elementary flows results in generation of finite lift forces. The flow past a triangular cylinder is turbulent. Vortex structures dominate this type of flow. A study of vortex dynamics of this type of flow will reveal the physics involved in the flow. The vortex dynamics of near wake region is responsible for the generation of von Kármán Vortex Street. As a result, the vortex flow structures in the near wake region of 60° and 75° triangular cylinders were studied numerically using LES. The study was performed at Re = 520 in the intermediate range.A system of interdependent vortices was discovered in the near wake region. This vortex system exists behind both cylinders. The primary and secondary vortex strengths have sinusoidal variation. This variation is similar in both cases. However, the time-period and amplitude are directly proportional to apex angle. A mathematical model of the variation was presented. This model is applicable to both cylinders. The study also indicated that the time-period and amplitude of the vortex strengths are mathematically related.