Flow past a circular cylinder has been extensively studied under non-cavitating conditions at Reynolds number lying either in the lower subcritical regime (ReD 3x105). However, relatively less attention is given to study the flow in the upper subcritical regime (20k ReD 300k), especially under cavitating conditions. Also, the effect of blockage (known as the blockage factor, BF) and spacing in the transverse direction between walls (Gap factor, GF) has not been properly dealt with. Thus the motivation for the present work is to address this gap by studying the dynamics of the shear layer in the wake of a cylindrical pin.



Numerical simulations are carried out using OpenFOAM for a 3-D planar venturimeter with a small cylindrical pin (AR=2.67, BF=20%, GF=2.5) at the centre of the throat of the venturi and oriented perpendicular to the flow. Kunz cavitation model is used to formulate the source term and turbulence closure is achieved by the k-ω SST turbulence model. Three Reynolds number (ReD=14k, 70k, 350k) spanning the subcritical flow regime and 11 cavitation numbers (σ) for each ReD was used in this study. The effects of cavitation on drag, cylinder surface pressure coefficient, static pressure, void fraction, turbulent kinetic energy (T.K.E.), and vorticity is presented. The interplay between flow turbulence and the cavitating structure is better brought out by the Fast Fourier Transform (FFT) of the forces, pressure, void fraction, and T.K.E. data.