Measurements Of The Heat Transport And Thermal Dissipation Rate In Rayleigh-Bénard Convection With Rough Plates

Rayleigh-Bérnard convection(RBC)is a classical hydrodynamic model,which is abstractly established from sophisticated natural phenomena.The study of RBC with rough plates can simulate some natural convection phenomenon and solve heat transport problems in engineering.We present an experimental study of heat transport properties and dissipation rate,including global heat transport,temperature profile,temperature statistical properties,thermal dissipation rate.All of these provide a complete physical picture about the thermal dissipation field and its statistical properties in turbulent convection.The measurements are conducted over a range of Rayleigh numbers Ra(1.6×109 ? Ra ? 1.2×1010)and a constant Prandtl number Pr(Pr = 5.4)in convection cell with rough plates.The measured global heat transport in rough cell is found to be increased in terms of that in smooth cell.And the dependence of Nu with Ra for the rough plates is Nu = 0.0418 Ra0.36±0.01.By measuring temperature profile,the experiment shows that the dependence of ? with Ra is ? = 2907×Ra-0.36.We divided the region of this system into three parts(thermal boundary layers,mixing region,bulk region).The study of local heat transport includes measurements of the normalized thermal dissipation rateN(r)e in mixing region and bulk region of rough cell.It is found that ?f(r)coming from fluctuations is dominant contribution to N_?(r)in these two regions,and N_?(r)decreases with increasing z.This suggests that the heat transport in outer boundary layers depends on the plume,whose density and strength also decrease with increasing z.It is also found that ?_f(r)and ?_m(r)decrease with increasing Ra,?f(r)and ?_m(r)have an power function with Ra.In the center and near the boundary layer(z/?>1)of the rough cell,the scaling law of ?f(r)increases 2/3 than in the smooth cell.This suggests that the density,strength and dissipation of plume in the rough cell is also larger in the smooth cell.It also discuss the series data of local temperature fluctuation ?T(t),temperature derivative d T/dz(t),the dissipation date ?_f(r,t),which is further found that the plume is dominant contribution to heat transport in outer boundary layer.