Numerical and experimental investigation of a finite cylinder wake

Abstract

Following a thorough time-resolved 2-D particle image velocimetry experimental investigation of the wake of a square wall-mounted finite cylinder, at Reynolds Re = 5.4 × 10 4 with aspect ratio H/d = 3, a 3-D DNS numerical investigation was performed under similar flow conditions and comparable Reynolds number (Re = 4.0 × 10 4). In this paper, the simulation results in four 2-D planes are compared to the experimental case using proper orthogonal decomposition (POD), spectral analysis and mean flow. Numerical and experimental POD modes were similar, with a few differences in mean flow values and main vortex emission frequency that can be explained by differences in boundary layer thickness. The investigated horizontal planes were z/H = 0.3, z/H = 0.5 and z/H = 1.0 planes, as well as the vertical x-z symmetry plane. While time-resolved experimental results were acquired independently for each investigated plane, numerical results were acquired concomitantly in all four planes, with full 3-D wake data available. The results in this paper confirm that the simulation is able to reproduce the main dynamic features of the flow, establishing the basis for deeper analysis of the full numerical data set in the future. Keywords Cylinder wakes • Finite cylinders • Computational fluid dynamics • Particle image velocimetry • Low speed flow List of symbols d Square cylinder side dt Time step z Cylinder height coordinate H Total cylinder height Re d Reynolds number based on the cylinder side St Strouhal number δ 99% Boundary layer thickness