NUMERICAL INVESTIGATIONS OF FLOW FIELD BEHIND SIDE BY SIDE TRIANGULAR PRISMS IN SEQUENCE AT LOW AND HIGH REYNOLDS NUMBER

Abstract

The flow field characteristic across two side by side triangular prisms (cylinders) is numerically investigated at Reynolds number 100. The working fluid is air. The effects of the gap ratio s/d (s is the separation between the cylinders and d is the characteristic dimension) on the flow are studied. The focus is towards understanding the effect of spacing between the cylinders on flow field around the cylinder. The flow field has been characterized in terms of velocity, streamlines, pressure contours, vorticity contours, drag and lift coefficient. The governing Navier-Stokes equation along with appropriate boundary conditions is solved by using a commercial CFD solver FLUENT (6.3). The computational grid is created in a commercial grid generator GAMBIT. The PISO algorithm in a collocated grid system is used for pressure velocity coupling. At smaller gap between the cylinders the flow merges as a jet between the cylinders and wake structure becomes chaotic. The interaction between the jet and vortex shedding is complex and suppression of vortex shedding is seen at a gap ratio of 0.5. At higher gap ratio shedding phenomenon dominates over jet. As a result the wake structure increases. At gap ratio 0.5 and I there is a strong interaction between the wakes of two cylinders whereas at gap ratio 1.5 and 2, distinct vortex shedding of both the cylinders is observed. Interaction of the wakes of the two cylinders occurs at far downstream. The vortex structures are systematically presented for different cases. In addition, the mean and instantaneous drag and lift coefficients are determined and discussed for various separation ratios. Beside this the flow is also simulated at 400 Reynolds number with a gap ratio of 1.5.