The Experimental Research Of Water-sediment Movement Characteristics At Sand Wave Surface And Sand Wave Evolution Law

The movement of sand waves is a dynamic form of bed load motion,it plays an essential impact on the water structure of river,as soon as the erosion and deposition of the river bed.At present,the study of sand wave motion law is not enough because of the complexity of sand wave movement and the lack of efficient sand wave movement measuring equipment.Therefore,to explore and develop a high precision sand wave motion detection technology,and studying the sand wave motion law based on the technology has an important significance for improving the basic theory of sediment movement system.In the research,inhomogeneous lightweight plastic sand is considered as experimental subject,and the test precision on the sink indoors.Develop a particle grading detection system based on image recognition technology and verify its reliability,the composition of sand samples at different positions of the tank section is analyzed based on the detection system;The water turbulent fluctuation information near typical sand wave is precisely acquired by using ADV and liquid tracer;The process of sand wave formation,evolution and sand particle movement on different water level is recorded with a high-speed video camera;Mass sand wave shape parameters are collected on the different water condition.The study of the flow structure of typical sand wave shows that the water over sand wave has obvious instability secondary flow structure,the different proportion of main flow and minor flow has different effects on downstream of sand waves;The time average velocity and fluctuating intensity has certain complementary on the same measuring point water;The scope of influence of sand wave effects on flow structure is about 5cm depth;The strongest fluctuating area is 80 cm downstream crest point and with the same height of it.The wavelet analysis to conveniently flow sequence indicates the turbulent flow with different scales and frequency of vortex structure characteristics;The analysis of velocity spectral density indicates that low frequency and large scale vortexes holds main energy of flow,large and small vortexes exist energy cascade phenomenon,the dissipation rate of high frequency band vortexes is 7/4.The bed load movement phenomenon of sand wave is analyzed in detail in this paper,contacting with water turbulent characteristics of the sand wave surface,different starting modes are established on the meeting area of sand wave,and the machine rational analysis the sediment motion in different location of the sand wave;The paper also describes the nonlinear process of sand grain formation and divides sand wave cycle period;the correlation among intensity of water flow,wave height,wave speed is analyzed on different sand wave evolution period under steady and unsteady flow condition;Through the statistical analysis of wave shape parameters on different water condition,the nonlinear relationship between sand wave shape parameters and water flow intensity is described;The fineness modulus(Mx)describes accurately the composition of bed load under the selection of them by flow;The formula of sand wave transport velocity with statistics and dynamics character and per unit width lightweight plastic sediment transport rate are established,which follow the dimensional harmony and has clear physical meanings.