In this paper, numerical simulations are conducted of flow past a circular cylinder confined symmetrically in a channel. The effects of upstream turbulence on wake properties are studied with upstream conditions assumed to be a canonical turbulent channel flow. Simulations have been conducted at blockages of $\beta =0.3$, 0.5, and 0.7, where blockage is defined as the ratio of cylinder diameter to channel height. It is found for the lowest blockage, $\beta =0.3$, turbulence trips the shear layers separating off the cylinder, forming Kelvin-Helmholtz vortices which rapidly roll-up and form Kármán vortices further downstream. This mechanism prevents merging of Kelvin-Helmholtz vortices, evidenced by a lack of a subharmonic peak in spectra of probes placed in the shear layer. For $\beta =0.5$, acceleration of fluid through the gap between the cylinder and channel wall partially relaminarizes the flow, reducing turbulence. Despite this, the surviving turbulence still trips the cylinder shear layer, causing it to break down. Finally, for $\beta =0.7$, a large change in wake dynamics is found to occur. Relaminarization again occurs through the gap, but is insufficient to suppress all turbulence. Hence, tripping the cylinder shear layer and breaking it down before wake bias could occur. This therefore results in the time- and spanwise-averaged flow being symmetric, unlike its laminar upstream counterpart. Spectral analysis also finds a strong subharmonic peak, indicating merging of Kelvin-Helmholtz vortices for $\beta =0.5$ and 0.7.

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• Turbulence
• Vortex shedding
• Wakes & jets