Flow around two tandem square cylinders near a plane wall

Abstract

An experimental study has been conducted to investigate the flow around two identical square cylinders in tandem arrangement and placed near a plane wall at a Reynolds number of 6,300. The inter-cylinder spacing ratio was varied from S* = 0.5 to 6, and the cylinder-to-wall gap ratio from G* = 0.25 to 2. Totally, 42 cases were considered to systematically examine the effects of wall proximity and the mutual interference between the two cylinders in the normalized gap–spacing (G*–S*) plane. The flow fields were captured using digital particle image velocimetry, in conjunction with measurements of the fluid forces (drag and lift) acting on the downstream cylinder using a piezoelectric load cell. The results show that the flow is highly dependent on the combined values of G* and S*. Categories relating to G* could be broadly classified as small-gap regime (G* 1) where the wall effects become negligible. Similarly, the flow interference between the two cylinders can be divided into three basic categories as a function of S*, namely, shielding regime at S* 3. Variations of force coefficients, amplitude spectra, Strouhal numbers, and Reynolds shear stress with G* and S* are presented to characterize the different flow regimes.