When incident particles impact into a sand bed in wind-blown sand movement, rebound of the incident particles and eject of the sand particles by the incident particles affect directly the development of wind sand flux...When incident particles impact into a sand bed in wind-blown sand movement, rebound of the incident particles and eject of the sand particles by the incident particles affect directly the development of wind sand flux. In order to obtain rebound and eject lift-off probability of the sand particles, we apply the particle-bed stochastic collision model presented in our pervious works to derive analytic solutions of velocities of the incident and impacted particles in the postcollision bed. In order to describe randomness inherent in the real particle-bed collision, we take the incident angle, the impact position and the direction of resultant action of sand particles in sand bed on the impacted sand particle as ran- dom variables, and calculate the rebound and eject velocities, angles and coefficients （ratio of rebound and eject velocity to incident velocity）. Numerical results are found in accordance with current experimental results. The rebound and eject liftoff probabilities versus the incident and creeping velocities are predicted.展开更多
The probability distributions of sand particles＇ lift-off and incident velocities in a wind-blown sand flux play very important roles in the simulation of the wind-blown sand movement. In this paper, the vertical and...The probability distributions of sand particles＇ lift-off and incident velocities in a wind-blown sand flux play very important roles in the simulation of the wind-blown sand movement. In this paper, the vertical and the horizontal speeds of sand particles located at 1.0 mm above a sand-bed in a wind-blown sand flux are observed with the aid of Phase Doppler Anemometry （PDA） in a wind tunnel. Based on the experimental data, the probability distributions of not only the vertical lift-off speed but also the lift-off velocity as well as its horizontal component and the incident velocity as well as its vertical and horizontal components can be obtained by the equal distance histogram method. It is found, according to the results of the X^2-test for these probability distributions, that the probability density functions （pdf＇s） of the sand particles＇ lift-off and incident velocities as well as their vertical com- ponents are described by the Gamma density function with different peak values and shapes and the downwind incident and lift-off horizontal speeds, respectively, can be described by the lognormal and the Gamma density functions, These pdf＇s depend on not only the sand particle diameter but also the wind speed.展开更多
基金The project was supported by the National Natural Science Foundation of China(10532040,10601022)
文摘When incident particles impact into a sand bed in wind-blown sand movement, rebound of the incident particles and eject of the sand particles by the incident particles affect directly the development of wind sand flux. In order to obtain rebound and eject lift-off probability of the sand particles, we apply the particle-bed stochastic collision model presented in our pervious works to derive analytic solutions of velocities of the incident and impacted particles in the postcollision bed. In order to describe randomness inherent in the real particle-bed collision, we take the incident angle, the impact position and the direction of resultant action of sand particles in sand bed on the impacted sand particle as ran- dom variables, and calculate the rebound and eject velocities, angles and coefficients （ratio of rebound and eject velocity to incident velocity）. Numerical results are found in accordance with current experimental results. The rebound and eject liftoff probabilities versus the incident and creeping velocities are predicted.
基金The project supported by the National Natural Science Foundation of China(10532040)the Hundred Talents Project.the Knowledge Innovation Project of Chinese Academy of Sciences(KZCX2-304).
文摘The probability distributions of sand particles＇ lift-off and incident velocities in a wind-blown sand flux play very important roles in the simulation of the wind-blown sand movement. In this paper, the vertical and the horizontal speeds of sand particles located at 1.0 mm above a sand-bed in a wind-blown sand flux are observed with the aid of Phase Doppler Anemometry （PDA） in a wind tunnel. Based on the experimental data, the probability distributions of not only the vertical lift-off speed but also the lift-off velocity as well as its horizontal component and the incident velocity as well as its vertical and horizontal components can be obtained by the equal distance histogram method. It is found, according to the results of the X^2-test for these probability distributions, that the probability density functions （pdf＇s） of the sand particles＇ lift-off and incident velocities as well as their vertical com- ponents are described by the Gamma density function with different peak values and shapes and the downwind incident and lift-off horizontal speeds, respectively, can be described by the lognormal and the Gamma density functions, These pdf＇s depend on not only the sand particle diameter but also the wind speed.
