Experimental Study And Numerical Simulation On Powder Sand Movement Characteristics

Estuary and coast are not only the areas where atmosphere, hydrosphere, lithosphere and biosphere carry out the most frequented exchange of material, energy and information,but also the areas affected the most by human activities. Sediment transport process usually links these interactions.Sediment is categorized into sand, powder sand and clay. The movement of powder sand is characterized as easily scattered and suspended when encountered power. Easy settlement occurs when power is weak. A lot of powder sandy beaches are dotted on Chinese coastline. The sediment motion characteristics and laws on powder sandy beach are obviously distinguished from that on muddy beach and sandy beach. Study on powder sand motion is of great significance for developing Chinese coastal economy, accelerating the harbor construction and improving the scientific level of coastal sediment study.This paper first uses mixed sediment deposition method to carry out hydrostatic sediment settlement experiment. We observed muddy surface height over time in 1000ml graduated cylinder, used turbidity measurement to test sediment concentration, and shot the muddy surface's falling process. Later we drew the settlement curve and calculated the slope of the constant velocity section of the settlement curve. The slope is settling velocity of sediment. And the paper obtains that settling velocity gradually decreases with the increase of the sediment concentration.Then we carried out the sediment incipient experiment under the current, wave and combined wave and current actions in the variable slope's wave and current flume to study on powder sand incipient laws, and obtained the critical incipient velocity and critical incipient stress.Finally, the paper uses Flow3D to simulate hydrostatic sediment settlement and sediment incipient. During the numerical simulation of hydrostatic sediment settlement, through the use of sediment scour model, we set the suspended sediment in numerical graduated cylinder and have got better results that are similar to the experimental results. During the numerical simulation of sediment incipient, through the use of sediment scour model and turbulence model, we set up a numerical flume, velocity sensors and wave height sensors. When the fine sand simulation is completed, don't change the grid parameters and calculate the critical shields parameter, the critical sediment fraction and cohesive sediment fraction by the same formulas, and then simulated the coarse sediment incipient. Lastly we have got better simulated velocity, wave height and sediment concentration that are similar to the experimental results.