In the present paper, three-dimensional Fluid structures and wake characteristics are evaluated for a square cylinder with an upstream splitter plate. The splitter plate divides the incoming flow in two streams, the upper and lower one, existing between them a velocity ratio. Two different Reynolds numbers of 56 and 200 and three different velocity ratios are here considered. The effect of the mixing enhancement using a square cylinder located downstream of the splitter plate is evaluated. A Floquet analysis to compute the spanwise wavelengths of three dimensional disturbances appearing in the square cylinder wake with and without a splitter plate is performed. It is observed that the use of the detached splitter plate has a stabilizing effect at low velocity ratios. However, when the velocity ratio increases, the vortex shedding suffers a linear increase and the wake resembles that of a mixing layer. Vortex dislocations appear at ratios larger than 2, which points out the onset of a bifurcation to a more chaotic wake. The wavelength of this secondary instability has been measured by means of Floquet analysis and two-point correlations being in the order of 3.5D.

Peer Reviewed