Large-Eddy Simulation of Flow Past Two Close Square Cylinders at Various Incidences

Abstract:

Large-eddy simulation was applied in the investigation of uniform flow past two square cylinders at a spacing ratio of P/B = 1.5 （P is the center distance of two cylinders and B is the side length of the cylinder） and an incidence angle of α = 0°to 90°. The aerodynamic forces， flow patterns， surface pressures， and flow fields were analyzed. The flow interference is significant for two square cylinders at a small spacing ratio. The variation of mean aerodynamic forces on the downstream cylinder is quite different from that on the upstream cylinder or a single square cylinder. In addition， a larger absolute value of lift force might occur at the downstream cylinder. The leading-edge separation mode （α = 0° to 10°）， separation-bubble mode （α = 20° to 30°）， attached-flow mode （α = 40° to 60°）， and gap-side separation-bubble mode （α = 70° to 90°） are summarized from the flow around two close square cylinders. A strong negative pressure is observed at the gap region for the attached-flow mode and gap-side separation-bubble mode. The strength of negative pressure in the near weak rises with incidence， reaches the maximum around α = 50°， and declines afterward. A single recirculation zone is observed in the weak of two cylinders at the lead-edge separation mode. However， two recirculation zones are recognized for the other three modes.

Key words:two square cylinders;small spacing ratio;large-eddy simulation;flow interference;flow mechanism