风速正弦变化下的非平稳跃移风沙流模拟

Numerical Simulation of Unsteady Sand Saltation under Sinusoidal Wind Variations

采用有限体积法模拟了风速正弦变化下的一维非平稳跃移风沙流发展过程。考虑风沙流跃移系统的4个子过程,沙粒的流体起动、沙粒的运动、击溅过程和沙粒对风场的反作用。给出在风速正弦变化时,风速变化频率和振幅对于沙粒输运的影响以及输沙率、风速廓线、床面剪切应力以及起跳沙粒数的变化规律。结果表明,输沙率随着振幅增大而增大,随着周期增大而减小;在初始的overshoot现象之后,床面剪切应力变化很小,但起跳的沙粒数随风速呈现类正弦周期变化。

Numerical simulations of one dimensional unsteady sand saltation process involving aerodynamic entrainment, sand particle motion, splash process and wind-sand coupling interaction present the evolution of wind-blown sand particles under sinusoidal wind variations. Effects of wind frequency/period and amplitude on sand transport rate are discussed. Variations of sand transport rate, wind profile, shear stress and sand number flux from bed with wind variations are shown. The results indicate that sand transport rate increases as wind amplitude increases, whereas decrease as wind frequency increases. The plot of bed shear stress against time shows a rapid decrease before ＂ overshoot＂ and varies very little after that. The sand number flux from bed however varies periodically with wind.