关于植被中湍流的研究

本文从实验和模式理论两个方面介绍了近年来在植被湍流研究方面的进展.实验研究表明,植被内湍流是高度间歇性的,大尺度涡在湍流输运中起主导作用.植物枝、干、叶打碎了大尺度涡,产生的迹湍流中的小尺度涡更容易耗散成热。因此,植被内能量不按一般的能量级串理论预示的方式进行,而要发生所谓“短路”现象,使得功率谱曲线的斜率在惯性区比-2/3律更负.现有的高阶封闭模式虽然取得了很大成功,但在模拟湍流强度上高估了其大小,还需根据实验加以改进.

STUDIES ON TURBULENCE IN VEGETATION

The present paper surveys advances in experimental and theoretical studies on turbulence in vegetation in recent years.The experimental results show that the turbulence in vegetation is high skewed,kurtotic and intermittent,and that turbulence transport processes in vegetation are dominated by large intermittent eddies. The plant elements, such as leaves, stems and branches generate turbulent wake with length scales smaller than those produced by meanwind shear. The smaller-sized, wake-generated turbulence dissipates rapidly into internal energy. Consequently, it is believed that the plant elements act to short-circuit the normal eddy cascade process. The spectral slopes in the inertial subrange are more negative than those predicted with Kolmogorov's - 2/3 theory. Although high order closure models of turbulence have been us,ed to study turbulence in plant canopies, the modeled u'2 and v'2 profiles are generally overstimated, some improvements are needed according to experimental results.