Effect of gap width on flow structure and reattaching characteristic of two tandem 5:1 rectangular cylinders: Experimental and numerical studies

The flow structure and reattaching characteristic of two tandem rectangular cylinders with aspect ratio being 5:1 have been investigated through wind tunnel experiments and three-dimensional large eddy simulation (LES) methods. The gap width G between the two cylinders varies from 2 times of D to 20 times of D, where D represents the depth of the two cylinders. The surface pressure distribution and aerodynamic forces of each cylinder are obtained via wind tunnel experiments. Two distinct flow patterns are identified with the increasing G through three-dimensional LES methods, and the aerodynamic results are presented in good agreement with the experiments as well. The experimental and numerical results indicate that the flow structure is highly sensitive to the variation in G, leading to alterations in the aerodynamics and vortex-shedding characteristic of two cylinders. Furthermore, the simulation results also capture the shift in the reattaching points as G increases. Additionally, following the simulation findings, a proposed criterion based on the wind tunnel experimental data is presented for predicting the boundary layer reattachment points on two tandem 5:1 rectangular cylinders.