Measurement of mean fields in the intermediate wake of a heated cylinder

Abstract

Measurements are made by a newly designed high-precision thermo-anemometer in the wake of a heated cylinder of D=0.013 and 0.030 m. The purpose of this work is to make clear the effects of cylinder heating on the mean field in the wake. Temperature and velocity distributions are obtained for X/D=5 - 40. Reynolds numbers for unheated case are Re_D=3000 - 10000 and temperature difference between the cylinder surface and the ambient air reaches Δθ=0 - 225 ℃. The effects of cylinder heating on the mean field are as follows : Normalized maximum values of θ_mean/θ_r , θ_rms/θ_r, u_rms/U₀ and v_rms/U₀ in each Δθ and U₀ have similar logarithmic decay tendencies occurred by vortex breakdown. When Δθ is same, the mean gradient of each parameter distribution becomes smaller with Re_D decreasing because of Richardson number Ri_D increasing. Values of u_rms/U₀ and v_rms/U₀ are increased, wake structure is made asymmetrical, and vortex collapsing is accelerated by cylinder heating.