Vertical Distribution Of Silt Suspension Concentration With Stratification Effect Due To Combined Waves And Currents And Its Application

With the rapid development of China’s economy in recent decades,more and more ports have been built on the silty coast.Compared with the muddy and sandy coast,the sediment movement mechanism of the silt coast,especially the sediment stratification phenomenon and its role under the action of strong waves,needs further investigation.Therefore,based on the diffusion theory,analyzing previous suspended sediment concentration experimental data under waves,we put forward a vertical suspended sediment concentration model considering the stratification and multi-component influence due to waves and combined waves and current.Experiments of silt suspension under combined waves and current was carried out and the measured data were used to verify the model..The model is further embedded into the threedimensional wave-current-sediment coupling model to simulate the suspended sediment motion and siltation of channel in the sea area of Huanghua Port.The main work and conclusions of this paper are as follows.(1)Based on many previous experimental data of suspended silt concentration under waves,using the wave diffusion coefficient based on the finite mixing theory,the stratification correction coefficient with concentration gradient and sediment particle size as parameters is obtained through fitting.The vertical distribution model of suspended silt concentration under waves considering stratification effect is established by comparing various reference concentration formulas.(2)The vertical distribution model of suspended silt concentration under combined waves and current is established.Furthermore,considering the influence of sediment particle components,the vertical distribution model of suspended silt concentration suitable for multi-component sediment is established.(3)The experiments of suspended silt concentration under irregular waves,combined waves and currents are carried out.It is found that under the action of irregular waves,the sediment suspension lags behind the water particle motion,and the high concentration layer near bottom forms only when there is an action of continuous large waves.Under the combined action of waves and currents,the wave height is the key factor affecting the near bottom concentration,and the increase of current velocity enhances the turbulence of water body,and then increase the sediment concentration in the upper water.(4)The suspended silt concentration model considering the stratification effect due to combined waves and current is embedded into the wave-current-sediment coupling model based on FVCOM-SWAN coupling,and the sediment transport in normal weather and strong wind weather around Huanghua Port is numerically simulated.The results show that the model can well describe the suspended sediment transport and channel siltation in the actual sea conditions.