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

Abstract

Flow-induced vibration (FIV) on two tandem cylinders with forced convection is numerically investigated 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 (circular cylinder) with two spacing ratio ([Formula: see text]) = 4 and 2 is studied. Transverse oscillations are generated from the cylinder having non-dimensional mass ([Formula: see text]) = 10. The structural damping coefficient is assigned a zero value with varying reduced velocity [Formula: see text]. The two-dimensional incompressible Navier–Stokes and energy equations are solved together with Newton's second law governing the motion of the cylinders. Both cylinders' surfaces are maintained at a higher constant temperature of [Formula: see text], and incoming flow is set to be at [Formula: see text] with Prandtl number (Pr) = 0.7. The effect of r* and [Formula: see text] is observed on the flow structure and FIV parameters. Flow characteristics at [Formula: see text] 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 ([Formula: see text]) experiences a hike in vibration amplitude due to the impingement of vortex shedding from the upstream cylinder ([Formula: see text]). r* = 1 has 18.1% higher vibrational amplitude than r* = 0 at their respective lock-in regimes for [Formula: see text]. For [Formula: see text], 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 [Formula: see text]. r* = 0.75 results in 13.3% higher oscillation amplitude as compared to r* = 0.5 for [Formula: see text]. The average Nusselt number ([Formula: see text]) strongly depends on flow topology, corner radius, and vibrational amplitude [Formula: see text]. At low [Formula: see text], heat transfer from the downstream cylinder is plummeted due to rolling of shear layers over the cylinder. There is a significant change in [Formula: see text] due to higher vibration; for example, increase in 10.71% change is observed from [Formula: see text] to [Formula: see text] for r*=1 and [Formula: see text]. Corner radii also alter the [Formula: see text] as a decrease in 27.39% from r* = 1 to r* = 0 at [Formula: see text] and [Formula: see text] ([Formula: see text]).