Study On The High Resolution Sediment Transport Rate In The Steady Flow Field

This thesis focused on some basic physical quantities in windblown sand movement, such as, for the theoretical analysis, numerical simulation of sediment transport rate and the change of average sediment transport rate in the relative time. However, the change of the high resolution instantaneous sediment transport intensity in the constant flow field is seldom. Therefore, in order to reveal the essence of sand transport rate mechanism, in wind tunnel experiments, we use high-speed camera to capture the instantaneous motion of wind sand flow, analysis of the relationship between the instantaneous air dynamics and the instantaneous sediment transport intensity, through sand saltation trajectory changes to reveal the instantaneous sediment transport rate of mutation theory. The main conclusions are presented as following,1) Basis of a principle of variation in gray level difference between two frame consecutive images, the statistics of the instantaneous sediment transport intensity changes, at the same time, the change trend of instantaneous critical friction is measured by using the hot wire, it is found that time interval of instantaneous sediment strength is greater than measurement range of 0.0015 s, with the increase of the height range and the time interval increases then decreases, in the same time, the height of the bed surface is different from that of the bed height, and the mutation intensity increases with increase of distance from bed. Such as under the bed pad surface 0~1 mm and 1~2 mm, the instantaneous transmission intensity of sand mutation values more is between 1000 to 2000, probability were 63.9 % and 56.1 %, with distance from bed height measurement range increased to 0~10 mm,instantaneous sediment transport strength increases much more than 4000, probability distribution for 84.2 %.2) Using MATLAB image processing software and artificial interpretation method to record the particle size of sand particles moving track coordinates the probability distribution of the horizontal velocity, vertical velocity, speed and angle of jump is determined. The horizontal velocity is the normal distribution.3) In the case of the sudden loss of sand, the sand grains in the process of the jump in specified range of bed height of memory in a similar "jump relay" phenomenon, this phenomenon exists randomness and diversity, which is related to the bed surface roughness and the momentum of movement of sand particles. Under the joint action of these factors, the sand particle trajectories are always in process of dynamic evolution.