The wake and thrust by four side-by-side cylinders at a low Re

The flow around four identical side-by-side circular cylinders placed normal to the oncoming flow is numerically simulated using the finite volume method (FVM) at a low Reynolds number of 100 based on cylinder diameter D and freestream velocity. How the wake structure, forces, and vortex shedding patterns are contingent on the spacing ratio g* (=g/D, where g is the gap spacing between the cylinders) is studied systemically when g* varies from 0.0 to 2.0. Based on the intrinsic features of the flow, four distinct flow regimes are identified in the range of g* examined. The total time-averaged drag force acting on the four cylinders escalates exponentially with a decrease in g*, as does the lift force, repulsive, on the outer cylinders. The lift forces of the inner cylinders are also repulsive but very weakly sensitive to g*. The Strouhal number is identical for each of the four cylinders in single body flow, different for the outer and inner cylinders in flip-flopping and quasi-interlocked flows, and again identical for interlocked flow.