Pan C.,Zhejiang Institute of Hydraulics and Estuary |
Huang W.,Florida State University |
Huang W.,Tongji University
Journal of Coastal Research | Year: 2010
Study of suspended sediment transport in an estuary affected by tidal bore is important for coastal engineering and management because the tidal bore can cause strong sediment resuspension and scour in shallow waters. Numerical modeling of suspended sediment transport in a natural estuary affected by tidal bore is such a challenging research topic that there are few articles on the subject available in the literature. In this study, a two-dimensional, numerical model was developed to investigate suspended sediment transport induced by a tidal bore. The hydrodynamic component of the model employs the Godunov-type scheme with second-order accuracy in space, which effectively describes the rapid supercritical flow and sharp horizontal pressure gradients of the tidal bore. To preserve balance between the source terms and the internal forces, both the water levelbottom topography formulation (WLTF) method and a special technique for triangular mesh have been applied to solve the source term in the model equations to account for the irregular bottom topography. The wet/dry boundary issue was solved by using the improved exact-Riemann solver on the dry bed. The coupled sediment transport model incorporates more reliable equations from recent publications to characterize the rapid increase of sediment resuspension in the water column. The model test against an analytical solution of convection transport shows that the sharp gradient of scalar transport is satisfactorily estimated in the model simulations. The model in the application has been validated to simulate hydrodynamics and suspended sediment transport affected by a tidal bore in the Qiantang River of China. The results compare well with a time series of observations to characterize the rapid increases of surface elevation, currents, and suspended sediment concentration resulting from the tidal bore. Results of spatial distributions of water levels and currents indicate that the model adequately describes the sharp horizontal gradients of the surface elevation and the tidal currents during the passage of the tidal bore and characterizes the suspended concentrations in the estuary. © 2010 the Coastal Education & Research Foundation (CERF).
Guo Y.,University of Aberdeen |
Wu X.,University of Aberdeen |
Pan C.,Zhejiang Institute of Hydraulics and Estuary |
Zhang J.,University of Aberdeen
Journal of Waterway, Port, Coastal and Ocean Engineering | Year: 2012
Results from a numerical modeling study are presented to investigate the tidal elevations, tidal current velocity, bed deformation, and suspended sediment concentration in the Qiantang Estuary, China. The Qiantang Estuary is well-known for its macrotide, which generates a hydrodynamically complex environment. This presents challenges for numerical modelers to accurately simulate the flow field and sediment transport in the region. This paper presents a mathematical model using finite volume method with unstructured mesh to simulate the tide-induced water elevation, current velocity, bed deformation, and suspended sediment transport in the Qiantang Estuary. The parameters in the model were determined using the long-term observed field data of the Qiantang Estuary. The simulated tidal elevations and current velocities agree well with the field observations. The numerical prediction of the bed deformation in 5 months is reasonably compared with the field measurements carried out in the same period. However, relatively large deviations exist between the simulated and observed suspended sediment concentrations, which are discussed in this paper. © 2012 American Society of Civil Engineers.
Qu L.,Zhejiang Institute of Hydraulics and Estuary |
Qu L.,Tsinghua University
Shuikexue Jinzhan/Advances in Water Science | Year: 2011
In order to resolve the issue concerning the relation of total dissolved gas(TDG) supersaturation and suspended sediment concentration of high-dams, a practical abatement measure for TDG supersaturation is put forward in this study. Based on a series of experiments, the production and release of TDG supersaturation in sediment laden flow are studied. The result shows that the production of TDG supersaturation remains almost the same level in either sediment laden flow or clear water for the same initial conditions. The rate of release of TDG supersaturation in sediment laden flow is significantly faster than that in clear water. The suspended sediment concentration can be increased through the use of bottom intakes, speeding up the release of TDG supersaturation. Such a measure can minimize the effect of TDG supersaturation on fish species in the downstream region of high-dams.
Xu C.,Hohai University |
Xu C.,Zhejiang Water Conservancy and Hydropower College |
Yue D.,Hohai University |
Deng C.,Zhejiang Institute of Hydraulics and Estuary
Engineering Applications of Artificial Intelligence | Year: 2012
Multicollinearity and difficulty of interpreting the coefficients of dam regression models pose two problems: (1) selection of informative variables for analysing dam deformation behaviour, and (2) mitigation of the multicollinearity among the variables. Resolving these two problems necessitates the application of genetic algorithm-based partial least square (GA-PLS) and statistically inspired modification of PLS algorithm (SIMPLS). A SIMPLS regression with the predictor variables selected by GA-PLS (hybrid GA/SIMPLS regression) is put forward to interpret the results obtained from periodic monitoring surveys of hydraulic structures. The hybrid model is employed for analysing the crack behaviour of an earth-rock dam in China. The results show the proposed model is superior to an ordinary SIMPLS and stepwise regression, especially when multicollinearity and influential outliers exist among the variables. Crown Copyright © 2011 Published by Elsevier Ltd. All rights reserved.
Tang H.S.,City University of New York |
Qu K.,City University of New York |
Wu X.G.,City University of New York |
Wu X.G.,Zhejiang Institute of Hydraulics and Estuary
Journal of Computational Physics | Year: 2014
It is now becoming important to develop our capabilities to simulate coastal ocean flows involved with distinct physical phenomena occurring at a vast range of spatial and temporal scales. This paper presents a hybrid modeling system for such simulation. The system consists of a fully three dimensional (3D) fluid dynamics model and a geophysical fluid dynamics model, which couple with each other in two-way and march in time simultaneously. Particularly, in the hybrid system, the solver for incompressible flow on overset meshes (SIFOM) resolves fully 3D small-scale local flow phenomena, while the unstructured grid finite volume coastal ocean model (FVCOM) captures large-scale background flows. The integration of the two models are realized via domain decomposition implemented with an overset grid method. Numerical experiments on performance of the system in resolving flow patterns and solution convergence rate show that the SIFOM-FVCOM system works as intended, and its solutions compare reasonably with data obtained with measurements and other computational approaches. Its unparalleled capabilities to predict multiphysics and multiscale phenomena with high-fidelity are demonstrated by three typical applications that are beyond the reach of other currently existing models. It is anticipated that the SIFOM-FVCOM system will serve as a new platform to study many emerging coastal ocean problems. © 2014 Elsevier Inc.
Xiong L.-H.,Zhejiang Institute of Hydraulics and Estuary |
Lu J.-J.,East China Normal University
Wilson Journal of Ornithology | Year: 2013
We studied exploitation of reedbeds by two specialist passerines, Reed Parrotbill (Paradoxornis heudei, listed as Near Threatened by the IUCN) and Oriental Reed Warbler (Acrocephalus orientalis), nesting in a tidal reedbed in the Changjiang River Estuary. Reed Parrotbills have significantly shorter, wider, and deeper bills than Oriental Reed Warblers. We distinguished >12 nest material categories in four groups (Phragmites, Zizania, artificial, and other) in nests of the two species. Reed Parrotbills used significantly fewer nest material categories, and had lower nest material diversity and a narrower nest material niche than Oriental Reed Warblers. More than 89% of the nest mass of Reed Parrotbills was Phragmites and was obtained from within the nesting habitat. More than 71% of the nest mass of Oriental Reed Warblers was Zizania from outside the nesting habitat. Most Phragmites material used by Reed Parrotbills was living tissue from reed leaf sheathes and stems. The large bill of the Reed Parrotbill facilitates exploitation of tissues from living reed shoots for nest materials, while the relatively long and slender bill of the Oriental Reed Warbler constrains it to use living reed shoots and exploit nest material from outside of nesting habitats. This is similar to their exploitation of food resources in reedbeds: Reed Parrotbills extract concealed insects within reed shoots while Oriental Reed Warblers glean exposed arthropods on a variety of plants. We confirm that food resource exploitation by Reed Parrotbills and Oriental Reed Warblers demonstrates a relationship between bill morphology and feeding as well as nest building. © 2013 by the Wilson Ornithological Society.
Xie D.-F.,Zhejiang Institute of Hydraulics and Estuary |
Pan C.-H.,Zhejiang Institute of Hydraulics and Estuary
Journal of Hydrodynamics | Year: 2013
In this paper, the turbulence characteristics of the tidal flow in the Qiantang River, China, the world-famous Qiantang bore, are studied. A detailed field observation at the Yanguan section of the Qiantang River was carried out during the spring tide in October 2010 with a continuous collection of high frequency turbulence data. The data analysis shows that the hydrodynamic processes are characterized by a strong tidal bore. Statistics of the turbulence such as the probability distributions of the turbulent components, the variance terms and the covariance terms are found consistent with those of previous studies of estuaries without the tidal bore. However, along the vertical profile, the distributions of all variables become more scattered downwards. The horizontal turbulence fluctuations are of a similar magnitude while the vertical turbulence has a fluctuation magnitude about 1/3 of that of the horizontal turbulences. The fluctuation strengths and the Reynolds stresses are much larger than those of other estuaries when the bore arrives. The bottom shear stress varies periodically with the tides, less than 0.44 N/m2 during the ebb but is increased drastically at the bore arrival, with the maximum being 0.92 N/m2. A good linear relationship is found between the bottom shear stress and the bottom suspended sediment concentration. © 2013 Publishing House for Journal of Hydrodynamics.
Jia H.,Zhejiang Institute of Hydraulics and Estuary |
Lu C.,Zhejiang Institute of Hydraulics and Estuary
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2010
The valid irrigation water amount, calculated by traditional method of field water use efficiency (FWUE) based on the theory of sufficient irrigation, can not reflect the water transfer and utilization in field as it includes invalid water. In this paper, the validity of evapotranspiration was analyzed according to the crop-water production function, and a new calculation method of FWUE was built based on the theory of deficit irrigation. Calculated by the new method, the FWUE of rice was 0.768 in flooding-irrigation mode, and 0.915 in Wet Irrigation mode. The result indicate a more accurate picture of water transfer and utilization in field.
Fu L.,Zhejiang Institute of Hydraulics and Estuary |
Jin Y.-C.,University of Regina
Journal of Hydraulic Engineering | Year: 2016
In this study, sediment transport is considered as a typical multiphase flow in numerical simulation using a particle-based method and efforts are focused on reducing interface instability between phases. A new multiphase model, a particle-method based rheology model, and a higher order viscosity smoothening scheme are used in a particle-based method to reproduce the sediment transport. Model applications including open channel flow scouring on sand beds and various water-sediment dam break flows are simulated. This new particle-based multiphase method is able to predict both free surface and sediment profiles. Additionally, the simulated velocity distributions of water-sediment dam break flow also show good agreement with measured data, which has seldom been considered in previous studies using a particle-based method. The successful implementation of the sediment transport simulation confirms the strong capability of this particle-based Lagrangian method for predicting multiphase flow and provides an alternative numerical tool in sediment transport study. © ASCE.
Sun M.-M.,Zhejiang Institute of Hydraulics and Estuary |
Sun M.-M.,Zhejiang Provincial Key Laboratory of Hydraulics Disaster Prevention and Mitigation
Yantu Lixue/Rock and Soil Mechanics | Year: 2014
A theoretical methodology which can calculate multiple scattering of plane SH waves by arbitrarily arranged and configuration of multi-row tubular piles is achieved. It can be considered the commonly so-called single scattering as the first order of multiple scattering. The second order of scattering of certain tubular pile is derived from incident waves which are excited from the first order of scattering by all tubular piles, which are also be regarded as the secondary waves by the first scattering. The rest scattering process of multiple order can be considered in the same manner. Assuming that every scattering order at pile-soil interface and interior of tubular pile are satisfied the elastic boundary conditions, the incident, scattering and transmitted waves are expanded in wave functions with Graf's addition theorem so that the undetermined scattering (transmitted) complex coefficients are obtained. Theoretical solutions of total scattering and transmitted wave fields inside the tubular piles are achieved. The influences of multiple scattering orders, ratios of the pile radius and distance between piles (or pile rows), shear modulus ratios of pile and soil, ratios of internal and external radius of tubular piles, geometric parameters of multi-row tubular piles etc. on screening effectiveness is discussed with numerical examples. The results show that tubular piles can achieve better screening effects than solid piles do. Several valuable reference bases of engineering design with discontinuous barriers made by tubular piles are delivered consequently.