He Xiaozhou, Tong Penger, Xia Ke-Qing
Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Phys Rev Lett. 2007 Apr 6;98(14):144501. doi: 10.1103/PhysRevLett.98.144501. Epub 2007 Apr 2.
The time-averaged local thermal dissipation rate epsilonN(r) in turbulent convection is obtained from direct measurements of the temperature gradient vector in a cylindrical cell filled with water. It is found that epsilonN(r) contains two contributions. One is generated by thermal plumes, present mainly in the plume-dominated bulk region, and decreases with increasing Rayleigh number Ra. The other contribution comes from the mean temperature gradient, being concentrated in the thermal boundary layers, and increases with Ra. The experiment thus provides a new physical picture about the thermal dissipation field in turbulent convection.
通过对充满水的圆柱形容器中温度梯度矢量的直接测量，获得了湍流对流中时间平均局部热耗散率εN(r)。结果发现，εN(r)包含两个部分。一部分由热羽流产生，主要存在于羽流主导的主体区域，并随瑞利数Ra的增加而减小。另一部分来自平均温度梯度，集中在热边界层，并随Ra的增加而增加。该实验因此提供了关于湍流对流中热耗散场的新物理图像。
