Influence of control cylinder placement on vortex shedding from a circular cylinder

Modifications to the vortex-shedding dynamics from a circular cylinder of diameter D are investigated experimentally in a free-surface water channel at $R{e}_D$=9500. The vortex shedding is modified via the placement of a control cylinder of diameter D/8 in the vicinity of the main cylinder. A methodology is presented to link changes in the wake dynamics and loading on the main cylinder. The analysis combines fourier model decomposition, proper orthogonal decomposition, and phase averaging. Based on differences in the wake dynamics, the influence of the control cylinder can be classified according to its placement: (1) in the free stream outside the main cylinder shear layer; (2) within the main cylinder shear layer; (3) in the recirculation region. While fluctuating lift is significantly reduced in all the cases, the mean and fluctuating drag are affected differently.