Applied Mechanics and Materials Vols. 212-213

Abstract: Based on the wave flume experiments, the response of excess pore water pressure was studied under the regular breaking wave action on a 1:30 slope sandy seabed. The topographic change was observed in the wave broken zone and its causes were analyzed. The results show that the variation gradient of excess pore water pressure are larger in the surface layer and the changing amplitude of variation gradient of excess pore water pressure is bigger in the wave broken zone. The water depth is the most influential factor of excess pore water pressure and the wave height and period has little influence on excess pore water pressure in the same wave steepness range in the wave broken zone. The topographic change is greatly in the wave breaking zone. Excess pore water pressures changing amplitude at the top are significantly higher than it at the bottom. When the seabed scours, the amplitude of the excess pore water pressure increases; and when the sand seabed accumulates, the amplitude of the excess pore water pressure decreases.

Abstract: Data assimilation is a method which integrates model and observation. In hydrology, ensemble Kalman filter (EnKF) as a sequential data assimilation method is often used to correct model parameters, thus improve the simulated accuracy. In this study, we conduct one numerical experiment to predict soil moisture using the one-dimensional soil moisture system based on ensemble Kalman filter and Simple Biosphere (SiB2) Model at Meilin study area, China. The simulated period is divided into two parts: 0-60h and 60-240h. The results show that EnKF is an efficient method in assimilating the soil moisture, especially in soil surface layer and deep soil layer; in addition, the efficiency of EnKF depends on the selection of initial soil moisture profile. With different initial soil moisture profiles, the performance of EnKF is different at the first few assimilated time, but with time grows, it can improve the simulated accuracy significantly.

Abstract: A generalized model is established and theoretical basis of model design and the model layout are illustrated. Simulation study on the phenomenon of tidal wave transformation with different length of irrigation channel through generalized physical model is carried out, and several conclusions are obtained. The length of irrigation channel influences tidal wave transformation obviously, including the difference of tidal process under various conditions, different trends of tidal range along the irrigation channel and the change of velocity ratio of flood and ebb tide with the length changing.

Abstract: The effect of land use and cover change (LUCC) aroused heated topic in the field of hydrogen. Change of LUCC and its effect on the stream structure in the study area are analyzed in paper. The land use transfer matrix from 1979 to 2006 was built through GIS and RS technique to perform an analysis on the characteristic of the LUCC, and its effect on river system is discussed using river structure indices. Result shows that (1) the loss of the forest, paddy field and dry land has contributed most to the increase of the urban area (16.76%, 7.11% and 10.75% respectively). (2) Length and density of river are decreasing by 41% and stability of river (SR) is shortening, especially in the moderately urbanised area, whose SR reach to 0.67. The low-grade river disappears more and the stream structure is not as complex as before.

Abstract: The paper examined the spectral characteristics of shallow water waves, which was based on the wave data collected along the south coast of Jiangsu. It proposes a tentative spectra model which can work better than Joint North Sea Wave Project (JONSWAP)spectra. Both of the value of tentative spectral parameters (α and γ) increase with significant wave height and spectral peak frequency. According to a regression analysis, empirical equations are achieved, which is related to the parameters with significant wave height and spectral peak frequency. The study shows that the measured wave spectra can be represented by tentative spectra, and the fitting results in high-frequency tail of tentative spectra are better than that of JONSWAP spectrum with modified parameters.

Abstract: The flow field of constructed wetland plays an important role in wetland stabilization and efficient operation. TengZhou Quanshang constructed wetland was taken as the research object. The RNG k-ε two-equation turbulence model equations coupling with the volume of fluid (VOF) model are introduced to simulation the vegetation cover flow. And the flow velocities of 37 measured points in wetland were measured by using the ADV instrument. Then the simulation velocity was compared with the field measured velocity. The results are shown to be satisfactory, and basically meet the large-scale flow analysis requirements. The problems of flow field distribution on the initial state was analyzed and optimized. The uniformity of velocity in wetland increased, and water mobility improved after optimization. Our results provide guidance for the 2D water quality simulation, pollutants migration and combination of plant purification effect in natural and constructed wetland.

Abstract: Sediment environment forms nature of the coast, and determines siltation characteristics of port and waterway. Based on definition for existing coast type, sediment environment of Panjin Port is studied by deposit characteristics, sediment concentration distribution, deposit from the tested pit and other aspects. The results show that, the Panjin Port is silty-sand coast. The beach had been stable and shallow beach is the main source of sediments. Although there has the possibility of sudden sedimentation from Geligangzi beach to 10m bathymetric line, siltation materials in the waterway is diggable.

Abstract: On the basis of analyzing and evaluating the determining methods of dominant discharge, a drawback is pointed about four common methods. A new method to determine the dominant discharge is presented in this paper, which is appropriate to the Lower Yellow River. According to comparison, the coefficient frequency of discharge and sediment is more applicability and rationality, which provides the reasonable technique parameters for the river management of the Lower Yellow River.

Abstract: A 2D hydrodynamics and salinity numerical model for the Changjiang River Estuary was set up by using Delft3D-Flow. The calculation results agree well with the real measured data, which indicates the model can be used to analyze the salinity in the Changjiang River Estuary. The calculated results of saltwater intrusion in the dry season of dry year shows that the main influence style of the salinity on the water intake of the Qingcaosha reservoir is the saltwater spilling over it from the North Branch during the neap tide and the saltwater intrusion from the open sea through the South Branch during the spring tide. The saltwater spilling over from the North Branch forms a saline water mass near the Xinjian sluice during the late period of a spring tide, which takes 5 days to reach the water intake of the Qingcaosha Reservoir.

Abstract: Based on the data of water depth in Nanshatou Passage, and the flow spilt ratio of the North Channel and the South Channel, the reasons for the sediment deposition in the Deepwater Navigation Channel of the Changjiang Estuary are explored. The sediment deposition in the Deepwater Navigation Channel of the Changjiang Estuary is affected by multi-factors, among these factors; the influences of the development of the Nanshatou Passage are significant. The development of the Nanshatou Passage leads to the increase of the ebb flow discharge and the southern bank of the South Channel scoured, the scoured sediment is carried by the ebb flow to the northern bank of the South Channel, and is silted in the entrance reach of the North Passage, which decreases the ebb flow volume entering into the Deepwater Navigation Channel. On the other hand, the Coriolis force and V-shaped diversion dike at the head of the Deepwater Navigation Channel are also key factors on effect of the Deepwater Navigation Channel.