Multiple slender structures subjected to a fluid flow are widely seen in engineering. Flow interference between the structures leads to a very high fluctuation of forces on the structures, structural vibrations, acoustic noise, or resonance, which in some cases can trigger failure, jeopardizing the residents lives. In engineering, fluid-induced forces, flow structures and vortex shedding frequencies are the major factors to consider in the design of structures. The knowledge of flow around two fluid-dynamically interfering cylinders is insightful for understanding the flow around more...