Abstract:The distribution characteristics of pollutant dispersion coefficient in the confluence of a curved river with tributary are studied. The mathematical model of air-water two-phase flow in the U-shaped confluent channel is established and verified by the data of previous laboratory experiments. Based on the simulation results, the influence of different discharge ratio on the flow structure and dispersion characteristics of confluent curved river is analyzed, in which the dispersion coefficient is calculated by the two-dimensional tensor method. The results show that the dispersion coefficient reaches the peak value in the vicinity of convergence, and the peak value increases with the increase of discharge ratio. Moreover, the longitudinal dispersion coefficient shows a single peak distribution along the river, while the transversal dispersion coefficient presents a double-peak structure.

Abstract:This study used the soil moisture product of ESA CCI(the Climate Change Initiative)and combined land surface parameters, brightness temperature, soil texture, terrain, rainfall and other auxiliary data, to establish a downscaling model for the soil moisture. Based on the moving window method, this model combined linear and nonlinear techniques. It was applied to downscaling the CCI data of soil moisture over China from 2003 Jan. to 2013 Dec. , in order to improve its spatial resolution. The downscaled data will be more suitable for the agriculture, hydrological simulation and other disciplines. Because ESA CCI product is not available over the whole China in winter, we further conducted a merge of ESA CCI product and the ERA-Interim product of soil surface moisture. Finally, we obtained the monthly soil moisture product over China with 1 km spatial resolution from 2003 to 2013. We further used in-situ observations to validate the product and found that this method improved not only the spatial resolution and the coverage, but also the precision.

Abstract:In order to predicate the immersion range and degree of the Xingan Navigation and Power Junction on the Xingan section of Ganjiang River, taking the right bank of reservoir as an example, a numerical model of three-dimensional transient flow based on the finite element method was established for the predication and assessment of immersion range and degree of the right bank of Xingan reservoir. Furthermore, based on the simulation model, a comparison was made for the effectiveness of immersion control with two operation conditions including the impervious wall and relief well combined with the impervious wall. When there is no operating conditions, the results indicate that the leakage immersion occurred at the downstream of dam site, the backwater immersion occurred at the upstream, and the immersed transition zone is formed at the dam site. Although the impervious wall can retard the immersion process, serious phenomenon of groundwater immersion will emerge after 275 days. The assessment results showed that the measure combining impervious wall and relief well can effectively control the immersion range, and the impervious wall can greatly reduce the displacement of the relief well. The findings can provide scientific basis for the immersion evaluation and controlling of the Xingan Navigation and Power Junction.

Abstract:The effective seismic load is expanded into the initial elastic modal vector of the structure as a combination of modal loads. Taking the Koyna dam as an example, a plastic damage concrete model and nonlinear time-history analysis method are used to calculate the nonlinear response of the dam caused by various modal loads. Subjected to the Koyna, El Centro and artificial ground motion with apeak value of earthquake acceleration 0. 5g respectively, the displacement responses of dam crest caused by the first 5 modal loads are provided. The results show that the nonlinear displacement response is still dominant by the same mode as modal load, and the weak coupling of modal response can be ignored for the calculation of nonlinear seismic response of gravity dams.

Abstract:In this study, combined with the measured data and theoretical analysis, the physical model experiment is setup for the Wudingmen sluice in Nanjing. After that, the problems of sediment deposition is formed and studied. The bend upstream induced by the sluice changes the flow pattern that can be improved by setting a diversion wall. The results also show that the river bend infect the flow pattern. Meanwhile, there are obvious recirculation zone on the both sides of river and the size of left zone is larger than the right, which results in the heavier deposition of left riverbed than the right side. In addition, the weak river flow dynamics makes the sediment deposition heavier. By setting the diversion wall upstream the sluice, the size of the recirculation zone is reduced and the flow pattern is improved. This study can provide reference for improving the upstream flow pattern and reducing sediment deposition.

Abstract:Two kinds of geotextiles were used to do the Gradient Ratio(GR)tests of a clay-geotextile system, and the Scanning Electron Microscope(SEM)technique was adopted in this study to observe the microstructure of clay after K tests. The objective of this study focuses on the clay filtering mechanism of geotextile from the microscopic point of view. Research results show that: (1)During the clay filtering process of geotextile, the gradient ratio rises rapidly at the initial stage, while after reaching the peak, the gradient ratio drops and tends to be stable with the gradual improvement of the permeability of geotextile-soil system; (2)Some fine clay particles close to the geotextile pass through and escape from the textile during the filtration, which should be the intrinsic mechanism of the permeability improvement of geotextile-soil system; (3)The filtered clay is mainly in the form of poly grain texture with loose structure and larger pores in the clay appear near the geotextile; (4)Geotextiles with different pore sizes and technologies have the same mechanism of clay filtering, while the extents of clogging are different.

Abstract:In order to apply the biogeography-based optimization ( BBO) algorithm to the structural damage detection, the algorithm is improved with the cosine migration model, the adaptive immigration function and the elitist mechanism. With the example of a simply supported beam under different damage situations, BBO algorithm is applied to detect not only the damage position but also the damage degree. The result indicates that compared with previous BBO algorithm, the improved one has the advantage of easier calculation, faster convergence speed, higher identification precision, and better stability, thus it can be effectively applied to the structural damage detection.

Abstract:The hydrodynamic model is established in the sea area of the Zhoushan Tidal Stream Energy Demonstration Project. The proposed model is based on the open source code OpenTidalFarm and verified by the observed data. In this model, the effect of tidal stream turbine is approximated by a locally-increased bottom friction and the turbines layout is optimized by the iterative algorithm and adjoint method. The result shows that the tidal current energy extracted by the optimized array is 15. 2% higher than that of initial regular array, which can be a reference for the development and utilization of tidal current energy in the Demonstration Project of Zhoushan Tidal Stream Energy.

Abstract:In order to study the characteristics of unsteady seepage in the filling and emptying process of lock chamber with a non-homogeneous layered ground, according to the theory of basis seepage flow, this study divides the seepage into the consolidation seepage and the instantaneous steady seepage. Based on the finite element software ABAQUS, the two-dimensional seepage model has been built according to a project example, in order to simulate the filling/emptying process of lock chamber considering fluid-solid coupling and analyze the characteristics and effect of unsteady seepage. The result shows that, with the cyclical variations of filling and emptying, the piezometric level has three characteristics: cyclicity, decay and hysteresis. In the filling and emptying process, zero velocity points exist. In addition, in the end of emptying process, the infiltration stress of unsteady seepage is greater than that of steady seepage with a low water level, the stability coefficient decreases and the possibility of seepage failure grows. Therefore, the influence of unsteady seepage field should be taken into account in the anti-seepage design of ship lock.

Abstract:In this study, the slope of coral reef has a steep reef-face(V∶H=1∶1). Utilizing the Smoothed Particle Hydrodynamics(SPH)method, the wave propagation and the fluid field around the reef crest were analyzed. After that, the results have been compared to the experiment results. The simulations show that the wave deformation and breaking occur in the process of wave propagation due to the shoaling. As a result of the nonlinear influence, the flow withsame direction as the wave propagation will be observed around the reef crest. This paper compares the results of numerical simulation and laboratory observations, and proved that there is a greet agreement between them.

Abstract:A 3D-FEM model involving the dynamic interaction of large diameter monopile and soil was established with the Abaqus software based on the elastic half-spacetheory. Then, the coupled horizontal-rocking vibration of monopilehas been analyzed. The influence of the dimensionless frequency, pile length-radius ratio, pile thickness-radius ratio, pile-soil elastic modulus ratio, scour depths around the pile to the dynamic impedance of the pile are discussed and the results are nondimensionalized to improve its applicability, which show that the influence of dimensionless frequency on the dynamic characteristics is closely related to other factors. Meanwhile, the pile length-radius ratio, pile-soil elastic modulus ratio, pile thickness-radius ratio, and scour depths around pile have a great influence on the dynamic characteristic of monopile. The study also found that the stiffness increases with the increase of length-radius ratio and there is a certain critical pile length. Damping has the same trend in a low dimensionless frequency. When the scour depth around the foundation reaches two times the diameter, the stiffness of the foundation will drop to about 1/3 of original value and the decrease of damping is also very significant.

Abstract:For the islanded microgrid based on wind and wave energy, a coordinated frequency control strategy with Battery Energy Storage System(BESS)and controllable load is proposed to improve the frequency stability. A novel droop controller is implemented in BESS to achieve primary frequency regulation. In the proposed droop strategy, the stable running point and droop gain are dynamically adjusted according to thestate of charge(SOC), to prevent the over-limitation of frequency, over charge and discharge of BESS. Moreover, controllable loads such as seawater desalination is served as a secondary frequency regulator. And then, frequency error is sent into PI controller to acquire the power reference of controllable loads so that the stable frequency error can be eliminated. Finally, the simulating model of islanded microgrid is built with Matlab/Simulinkand simulation verification is performed underdifferent operating scenarios. The results show that the coordinated frequency control strategy can effectively maintain the power balance and frequency stability of the islanded microgrid.

Abstract:According to the nonlinear characteristics of the daily grid electricity data of hydropower stations, the statedependent autoregressive (SDAR) model is used to describe this data. In this study, the Gaussian radial basis function (RBF) networks are used to approximate the functional coefficients of SDAR model, and the parameters of the RBFAR model is estimated by anoffline structured nonlinear parameter optimization method (SNPOM). After that, this model is applied to predict the data. Through the train and test for the real data of daily grid electricity of hydropower stationsin the left bank and right bank of Three Gorges as well as comparison with other classical algorithms, the forecasting accuracy and feasibility of RBFAR model are verified.