Effect of corner radius on flow topology and heat transfer from free oscillating tandem cylinders at low Reynold Number

Flow-induced vibration (FIV) on two tandem cylinders with forced convection is investigated numerically at a constant Re=150. Elastically mounted cylinder with four different values of corner radii ( r*=r/R:r=radius of fillet ;R=Radius of circle) =0 (square cylinder), 0.25, 0.75 and 1.0 (circular cylinder) with two spacing ratio ( L/D)=4 and 2 are studied. Transverse oscillations are generated from the cylinder having non-dimensional mass ( m*)=10. The structural damping coefficient is assigned a zero value with varying reduced velocity. Both cylinder's surfaces are maintained at a higher constant temperature of T*=1, and incoming flow is set to be at T*=0 with Prandtl Number (Pr)=0.7. The effect of r* and L/D is observed on the flow structure and FIV parameters. Flow characteristics at such as steady flow, reattachment and unsteady flow are examined. A "shift" in vibrational amplitude is noted from r*= 1 and 0.75 to r*=0 and 0.5, respectively. The downstream cylinder ( Dc) experiences a hike in vibration amplitude due impingement of vortex shedding from the upstream cylinder (U c). r*=1 has 18.1% higher vibrational amplitude than r*=0 at their respective lock-in regimes for Dc. For L/D=2, vortices from upstream and downstream cylinders interact to form C(2S) and 2S types of vortex shedding. Different regimes such as single body, reattachment, and co-shedding have been observed while changing L/D . r*=0.75 results in 13.3% higher oscillation amplitude as compared to r*=0.5 for Dc. Average Nusselt number strongly depends on flow topology, corner radius, and vibrational amplitude.