风沙二相流运动特点的分析

本文以平坦沙漠上定常，充分发展的风沙二相流为例分析了颗粒的跃移运动，在这种运动中颗粒吸收气流的机械能和水平动量向下输送，并在落地时传递给床面。本文还用拟流体观点分析了固相运动的特点：在床面上有较大的滑移速度，有较大的垂向速度脉动，例题垂向的平均速度却为零，等等。

AN ANALYSIS OF THE CHARACTERS OF BLOWN SANDS

In this paper, the saltation of sand grains was studied in the case of the steady and fully developed blown sands.It was found that moving sand grains always gain horizontal momentum and mechanical energy from the wind and transfer them down to the bed surface.The features of saltation was analysed in a continuum viewpoint:the particle phase has relatively fast slip velocity on the bed surface,and it has rather strong vertical velocity fluctuation while the average vertical velocity is exactly zero. The vertical velocity fluctuation of particle phase is neither(molecular)thermal motion nor turbulent fluctuation,so it is a new sort of fluctuation which is called PL fluctuation by the authors[6,7]. It was pointed out that this velocity fluctuation is the reflection of particle saltation in the continuum viewpoint, and it plays a rather important role in determining the structure of the blown sand field and maintaining the microscopical balance in this field.In the end,the shear stress corresponding to this fluctuation was discussed:the constitutive relation was given and an important character of this shear stress was discoverd that it is almost independent of the local velocity gradient of the particle phase.