Mechanism of heat transportation in the intermediate wake of a heated cylinder

Abstract

The paper clarifies the effects of buoyancy on the mechanism of heat transfer in the wake of heated cylinder for X/D=5-40. Measurements are made by a thermo-anemometer. Reynolds numbers Re_D=U₀D/ν in non-heated condition are varied from 3000 to 10000 for the temperature differences Δθ from 0 to 225 ℃ (corresponding Richardson numbers Ri_D=0-0.0568). The dimensionless conservation for heat is valid in the heat transport equations in this flow field. In the equations, heat transportation are almost carried out with turbulent diffusion terms and production terms of mean temperature gradient. As for the momentum transportation, velocity fluctuation at vortex shedding frequency f_c contributes mainly to transport heat in the upstream sections. But in the downstream sections, fluctuations at frequencies around f_c play important role with breakdown of the Karman vortex street. Heat-transport mechanism in the heated cylinder wake is affected by both the non-symmetry construction and the vortex breakdown.