Bed Load Data Acquisition Method Based On Image Processing And Its Application

The bed load of non-uniform sediment is an important part of sediment transport in river,which directly affects the basic problems such as flow structure,sediment transport and riverbed evolution.Correct understanding of the movement law of non-uniform sediment bed load is the premise of reasonable development and protection of river,which is of great significance to promote the development of river dynamics and meet the needs of practical engineering.In this paper,high speed photography and digital image processing are used to study the movement characteristics of non-uniform sand.The main contents are as follows:(1)This paper proposes a method to obtain the motion parameters of sediment particles by combining digital image processing with moving target detection technology.The advantages and disadvantages of two kinds of moving object detection algorithms,image difference method and optical flow field method,are compared,and the image difference method is improved to obtain the motion parameters of moving sediment particles in complex background;a method to measure the relative sand storm exposure of non-uniform sand by using image processing technology is proposed.(2)The flume experiment on the movement characteristics of non-uniform sediment was carried out,and the transport law of non-uniform sediment was obtained.The results show that the trajectory of the particles oscillates in the horizontal plane and jumps intermittently in the vertical plane;in the jumping stage,the instantaneous longitudinal velocity increases,and the instantaneous vertical velocity first decreases and then increases;after the collision with the bed particles,the instantaneous velocity decreases sharply;the distribution of the longitudinal instantaneous velocity of the particles presents Gama distribution,and the vertical velocity increases The results show that the distribution of instantaneous velocity is normal distribution;the velocity of sediment particles of the same size in the water increases with the increase of flow friction velocity,and the ratio of average velocity of particle longitudinal movement to friction velocity does not change significantly with the increase of ?;the instantaneous transport of sediment particles in the flume is pulsating and periodic.(3)Based on the image processing technology,the random distribution of non-uniform sand particles is obtained.Glass spheres with different sizes were used to simulate nonuniform sand.The relative exposure and relative concealment of different sizes of non-uniform particles were measured,and the distribution law of relative exposure and relative concealment of different sizes of non-uniform particles was analyzed.The test results show that the probability density of relative exposure degree of different particle sizes in non-uniform sand conforms to the normal distribution,and the probability density of relative concealment degree of different particle sizes in non-uniform sand conforms to the negative skew distribution within the value range.(4)Based on the randomness of particle position on the three-dimensional bed surface,the incipient velocity formula of non-uniform sediment is established.According to the stress of particles on the bed surface of three-dimensional non-uniform sand,the variation law of the action point of water drag force with relative exposure and relative particle size is obtained.Combined with the position relationship of non-uniform sand particles in the threedimensional spherical model,the relationship between the drag force arm,lift force arm and gravity force arm and the relative exposure and relative particle size is constructed The dynamic incipient velocity formula of non-uniform sediment is established by considering the factors of flow pulsation,sediment incipient criterion,three-dimensional relative exposure and relative particle size.The calculated results are in good agreement with the experimental data.