Flow Around Finite Circular and Square Cylinders in an Open Channel

Abstract

An experimental investigation was performed to study the structure of the flow field around finite circular and square cylinders in a water channel. Detailed velocity measurements using a particle image velocimetry (PIV) system and proper orthogonal decomposition (POD) analysis were conducted to examine the structures in the near-wake region. Iso-contours and profiles of mean velocities and some turbulent quantities at various streamwise locations were reported. The proper orthogonal decomposition was applied to provide insight into the structure of the flow. The results show that the vortex in the square cylinder is bigger and extends to cover part of the free end of the cylinder. There is also an up-wash flow from the base of the cylinders to form saddle points. The saddle point in the square cylinder is closer to the free end than in the circular cylinder. The low order reconstructed turbulent intensities from POD show that the square cylinder has more large scale structures than the circular cylinder.