Parametric Study on Aerodynamic Force Characteristics and Flow Patterns of Two Tandem or Staggered Rectangular Cylinders

The aerodynamic force characteristics and flow field interference effects of two tandem or staggered rectangular cylinders at Reynolds number Re = 22 000 are investigated systematically. Two-dimensional numerical simulations are performed to examine the effects of the cylinders' width-to-height ratio (B/D of 1 to 10), streamwise spacing (S/D of 1 to 6), and transverse spacing (V/D of 0 to 4) on the aerodynamic forces and flow patterns. The key findings reveal that the mean and fluctuating aerodynamic forces, as well as the Strouhal number, exhibit complex dependencies on these parameters. Seven flow patterns are identified: single bluff body, shear layer reattachment, periodic gap, vortex impingement, chaotic, modulated periodic, and synchronized vortex shedding flow patterns. These patterns are systematically classified based on the influences of the B/D, S/D, and V/D. The relative positions of the cylinders and their aspect ratios significantly influence the flow patterns and aerodynamic forces. The maximum percentage changes of time averaged drag coefficient, for instance, is 26.92% and 57.96% for the upstream and downstream cylinders at different B/D, respectively. The results provide valuable insights into the flow mechanisms and a theoretical foundation for engineering designs of tandem and staggered rectangular cylinders.