Zhou Quan, Sun Chao, Xia Ke-Qing
Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
Phys Rev Lett. 2007 Feb 16;98(7):074501. doi: 10.1103/PhysRevLett.98.074501. Epub 2007 Feb 12.
An experimental study of the morphological evolution of thermal plumes in turbulent thermal convection is presented. Individual sheetlike plumes are extracted and their area, circumference, and "heat content" are found to all exhibit log-normal distributions. As the sheetlike plumes move across the plate they collide and convolute into spiraling swirls. These swirls then spiral away from the plates to become mushroomlike plumes which are accompanied by strong vertical vorticity. The measured profiles of plume numbers and of vertical vorticity quantify the morphological transition of sheetlike plumes to mushroomlike ones and the mixing and merging or clustering of mushroomlike plumes. The fluctuating vorticity is found to have the same exponential distribution and scaling behavior as the fluctuating temperature.
本文呈现了对湍流热对流中热羽流形态演变的实验研究。提取了单个片状羽流，发现其面积、周长和“热含量”均呈现对数正态分布。当片状羽流在平板上移动时，它们相互碰撞并卷绕成螺旋状漩涡。然后这些漩涡从平板螺旋状散开，变成蘑菇状羽流，并伴有强烈的垂直涡度。测量得到的羽流数量和垂直涡度剖面量化了片状羽流到蘑菇状羽流的形态转变以及蘑菇状羽流的混合、合并或聚集。发现脉动涡度与脉动温度具有相同的指数分布和标度行为。
