Wake asymmetry of a heated cylinder in a cross flow

This paper investigates the flow and temperature distribution around a heated cylinder with an aspect ratio of 3.3 using 2D-PIV and thermocouples in a wind tunnel. The asymmetric wake and the influence of the free-stream turbulence intensity on the flow and temperature field were carefully examined under free-stream cross-flow conditions at a Reynolds number Re_D = 2.2 × 10⁴, with the flow being either laminar (Tu = 0.3 %) or turbulent (Tu = 5.9 %) after the artificial transition. Under laminar flow at a Richardson number Ri = 0.01, the heating from the cylinder increases the local air kinematic viscosity by approximately 1.47 times, which in turn, reduces the local Reynolds number to 1.5 × 10⁴. This causes the flow separation to occur earlier compared to the unheated scenario, with the width of the recirculation bubble and the length of vortex formation increasing up 16 % and 13 %, respectively. For heated scenario, geometrically asymmetric wake and surface temperature arise from slight differences in flow separation locations between the upper and lower surfaces, which is driven by local natural convection near the surface. When the free stream is turbulent, the asymmetry wake is weakened, and the surface temperature difference between the upper and lower surfaces decreases by 23 %, which is attributed to the attenuation of the natural convection near the cylinder surface. When comparing the temperature decay after the power to the heated cylinder is turned off, it is evident that temperature decreases more rapidly in the turbulent flow than that in the laminar flow, because of the enhanced forced convection in the turbulent flow.