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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

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. Source

Xiong L.-H.,Zhejiang Institute of Hydraulics and Estuary | Lu J.-J.,East China Normal University
Wilson Journal of Ornithology

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. Source

Fu L.,Zhejiang Institute of Hydraulics and Estuary | Jin Y.-C.,University of Regina
Journal of Hydraulic Engineering

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. Source

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

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. Source

Qu L.,Zhejiang Institute of Hydraulics and Estuary | Qu L.,Tsinghua University
Shuikexue Jinzhan/Advances in Water Science

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. Source

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