Three-dimensional study of flow past blunt headed cylinder at low Reynolds numbers

In this paper, a numerical model is proposed to study the transition to three-dimensionality and the evolution of vortices in the wake of a blunt-headed cylinder considering air as the working fluid in the Reynolds number (Re) range 130-2000. An experimental setup is developed to validate the numerical model on the basis of heat transfer characteristics. Based on symmetry and time dependence characteristics of flow, it is categorized as dynamically steady symmetric flow (50 <= Re <= 200), dynamically steady unsymmetric flow (220 <= Re <= 270) and unsteady flow (Re >= 280). The vortex dislocation phenomenon showing intermittent low frequency pulsa-tions during the transition to three-dimensionality is studied. Aerodynamic characteristics are studied by computing force coefficients and Strouhal number (St). Brief overview of heat transfer characteristics is given. Dynamic mode decomposition (DMD) analysis is carried out to determine quantitatively the critical Re at which secondary instability occurs and hence clear demarcation of the Re regime is obtained for the validity of two-dimensional analysis of blunt headed cylinder.