Mixed Convective Transport Around Staggered Rows of Square Cylinders

The unsteady mixed convective transport around multiple bluff objects placed in a staggered configuration with respect to a uniform free stream flow is analyzed through two-dimensional numerical computation. The bluff objects are identical in shape and size with square cross-section and arranged in two different rows within an unconfined domain. A small temperature difference between the objects and the free stream results in the free convection in addition to the forced flow. Simulation is carried out using a finite volume based method considering a uniform cross flow of air (Prandtl number = 0.71) at a moderate Reynolds number (= 100). The transverse spacing between the cylinders may anticipated to influence significantly the wake dynamics, which in turn affects the thermal transport. Simultaneously, the mixed convective strength also influences the wake dynamics and vortex structure formation. An interplay between these two effects aptly dictates the resulting flow dynamics and associated thermal transport. Accordingly, the dimensionless transverse spacing is varied (= 1, 3 and 5) along with the mixed convective strength (Richardson number = 0-2). It is observed that the flow and thermal fields show chaotic nature at smaller transverse spacing. However, at larger spacing, the usual unsteady vortex dynamics persists. Very interestingly it is observed that the chaotic flow at smaller transverse spacing reduces its instability to become unsteady periodic at larger strength of the thermal buoyancy. The average heat transfer from the cylinders is found more at smaller transverse spacings and it increases with increasing mixed convective strength