Flow around square, rounded, and round-convex cylinders at Reynolds numbers 20 to 22,000

Abstract

Flow around a square-like cylinder with round corners at a radius R = B/7 (B: nominal side length) and round sides at a radius K = B were numerically investigated at Reynolds numbers Re = 20 to 22,000. The Re-dependence of flow-induced loading and flow features of this “round-convex” cylinder was compared with square and rounded cylinders. Compared with the square and rounded cylinders, the round-convex cross-section has a smaller and declining drag, lower fluctuating loads, and a weaker vortex shedding from Re = 1000 to 22,000, showing distinct Reynolds number effects. A steady regime at Re = 20 and 45, a 2D regime at Re = 100 and 200, a 3D regime at Re = 300, 500, and 1000, and a turbulent regime at Re = 3900, 10,000, and 22,000 are identified for the round-convex and rounded cylinders, while a 3D flow is observed at Re = 300 for the square cylinder. The flow separation shifts from the rear corner to the front corner at Re = 200 and 300 for the square and rounded cylinders, respectively, while the separation point gradually moves to the middle of lateral sides for round-convex cylinders, which is similar to a circular cylinder.