Flow three-dimensionality of wavy elliptic cylinder: vortex shedding bifurcation

Abstract

The three-dimensional flow of a wavy elliptic cylinder and its wake are investigated for wavelength (λ) to hydraulic diameter (Dm) ratio λ/Dm = 3.43, 4.58, and 6.01. The study aims to gain insights into flow separation, flow dynamics, and three-dimensional flow topologies for the selected wavelengths. Three-dimensional flow structures are visualized through time-averaged streamlines with critical point theory. The results for λ/Dm = 3.43 show spiral flow directed from the node to the saddle, counter-rotating vortices, and a wavy vortex structure. On the contrary, the flows for λ/Dm = 4.58 and 6.01 respectively undergo bifurcation in stable recirculation and vortex shedding on a half-span of the cylinder wavelength. The bifurcation results in a spiral flow toward the saddle and the other spiral flow toward the node. The bifurcations of recirculation and vortex shedding are revealed for the first time. The findings contribute to an improved understanding of the insight into intricate flow physics around wavy elliptic cylinders.