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The wake topology developing behind a wall-mounted square cylinder in aturbulent boundary layer has been investigated using a high-resolutionlarge-eddy simulation (LES). The boundary-layer thickness at the obstaclelocation is fixed, the Reynolds number based on the cylinder h and the incomingfree-stream velocity $u_\infty$ is 10,000 while the aspect ratio (AR), definedas obstacle height divided by its width, ranges from 1 to 4. The Reynoldsstresses, anisotropy-invariant maps (AIM) and the turbulent kinetic energy(TKE) budget are analyzed to investigate the influence of AR on the wakestructures and on the turbulence production and transport. In particular, thetransition from a dipole configuration for low AR to a quadrupole wake isextensively discussed and examined. The necessity of more data to express thiscritical AR as a function of the momentum-thickness-based Reynolds number$Re_{\theta}$ is thus highlighted. As an effect of the AR, the wake is deformedin both streamwise and spanwise directions. This contraction of the wake,attributed to the occurrence of the base vortices for the cases AR = 3 and 4,impacts the size of the positive production region that stretches from the roofand the flank of the obstacle to the wake core. The AIMs confirm the wakethree-dimensionality and are used to describe the redistribution of theturbulent kinetic energy (TKE) along the three normal directions, in agreementwith the literature [A. J. Simonsen and P. Krogstad, Phys. Fluids 17, 088103,(2005)]. The present analysis on the TKE budget displays a stronger turbulenceproduction for the cases AR = 3 and 4, demonstrating the strong influence ofthe tip and base vortices in generating turbulence at the wall location behindthe cylinder.

Aspect-ratio effect on the wake of a wall-mounted square cylinder immersed in a turbulent boundary layer