Effects of chamfering and spacing on aerodynamics of two tandem cylinders

The flow over two tandem cylinders is investigated with five different spacing ratios L/D = 1.25, 2.0, 3.5, 4.0, and 6.0 and four chamfered-corner ratios ξ = B/D = 0%, 5%, 10%, and 15% at a Reynolds number Re = 5300, where L, B, and D are the distance between cylinders, chamfered corner dimension, and cylinder width, respectively. This work aims to assimilate the effects of ξ and L/D on flow structures, vortex shedding, aerodynamic forces, Strouhal number, and their relationships. We identified three different flow patterns depending on ξ and L/D: overshoot flow (L/D = 1.25, ξ = 0%), reattachment flow (1.25-2.0 ≤ L/D ≤ 2.0-3.5, ξ = 0%-15%), and coshedding flow (L/D ≤ 2.0-3.5, ξ = 0%-15%). The ξ and L/D play a similar role in the qualitative change of the flow structures, albeit with different degrees. As such, when L/D or ξ is increased, an overshoot/reattachment flow may change to a reattachment/coshedding flow. With the same flow pattern, ξ has a greater influence on the aerodynamic facets than L/D. This study establishes a framework for understanding how ξ and L/D influence flow topology and aerodynamic parameters.