Effect of incoming boundary layer thickness on the flow dynamics of a square finite wall-mounted cylinder

Abstract

This paper investigates the flow dynamics around a square finite wall-mounted square cylinder of two different aspect ratios (A R = H / D = 6 and 10, H and D are the height and width, respectively) under six boundary layer thickness (δ / D = 0.5 - 4.0, δ is the boundary layer thickness) using the improved delayed detached eddy simulation turbulence model. The Reynolds number based on the square cylinder width and incoming velocity is Re = 1.4 × 10 4. The aerodynamic force, surface mean and fluctuating pressure, wake closure length, Reynolds stresses, turbulence production, and the anisotropy of turbulence are analyzed in detail to investigate the effect of A R and δ / D combinations. The Q-criterion vortex identification method is adopted to identify and classify the vortex structures of different A R and δ / D combinations. The parametric diagram based on A R and δ / D to predict the dipole/quadrupole wake structure proposed in Yauwenas et al. ["The effect of aspect ratio on the wake structure of finite wall-mounted square cylinders,"J. Fluid Mech. 875, 929-960 (2019)] is refined based on results of the present study (quadrupole wake for A R = 6 with δ / D ≥ 1.5 and A R = 10 with δ / D ≥ 1.0). The instantaneous space-time pressure distribution along the whole span proves the existence of cellular shedding (A R = 10 for δ / D = 0.5 - 2.0), and the spectral proper orthogonal decomposition technique is adopted to investigate the cellular shedding phenomenon and its distribution. With the increase in δ / D from 2.0 to 4.0, the cellular shedding process is absent, implying the inhibitory effect of increasing boundary layer thickness on the cellular shedding.