Hydrodynamic interaction between 2D square cylinders in oscillatory, large-amplitude flow

We study hydrodynamic interaction effects on the in-line and cross-flow loads on two fixed, square, two-dimensional cylinders in infinite fluid subjected to oscillatory flow at high Keulegan–Carpenter ($\text{KC}$) numbers ($\text{KC}=5-24$). The cylinder cross-sections are quadratic with both sharp and rounded corners. Both experiments and numerical simulations are carried out. The numerical simulations cover side-by-side, tandem and a range of staggered configurations. The experiments cover only tandem configurations, to which the CFD results agree well. The effect of rounding the corners and the two cylinders’ orientation relative to each other (facing each other, or facing the flow) are studied. The relative orientation is shown to matter significantly, while the rounding of the corners more moderately, although the loads are notably reduced. The drag, lift and inertia coefficients are presented and discussed in detail, and there is in general hydrodynamic interaction effects as expected and reported earlier in the literature. More notably, however, there are important $2\omega -$load components due to hydrodynamic interaction, both in-line and cross-flow, but most pronounced in the cross-flow direction ($\omega$ is the frequency of oscillation). The $2\omega$ cross-flow loads are more sensitive to the cylinder orientation relative to the flow than the in-line loads.