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A numerical study on the effect of tidal flat's slope on tidal dynamics in the Xiangshan Bay, China

Acta Oceanologica Sinica 2018年第9期37卷 29-40页

作者： LI Li YE Taoyan he zhiguo XIA Yuezhang Ocean College Zhejiang University State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyState Oceanic Administration

The Xiangshan Bay is a semi-enclosed and narrow bay, which is characterized by large scale tidal flats and has been historically utilized through coastal construction and aquaculture engineering. The hydrodynamic model using the Finite Volume Coastal Ocean Model（FVCOM） was constructed to examine the changes of tidal dynamics due to the variation of tidal flat slopes. According to the model results, a decreased slope of a tidal flat would amplify the M2 tidal amplitude and delay the M2 tidal phase in the inner harbor, due to an increased tidal prism, and vice versa. The amplitude of the main shallow-water tide M4 would be amplified/dampened in the entire bay due to the changed bottom friction, if the tidal flat＇s slope were reduced/increased at the Tie inlet. The phase was advanced. The change of a tidal flat＇s slope at the Tie inlet had greater impacts on tidal amplitude,phase and duration asymmetry, than that at the Xihu inlet. The impact of changes of the tidal flat slope at the Xihu inlet was small and was constrained locally. Changes in the tidal flats＇ slopes at the Tie and Xihu inlets changed the tidal duration asymmetry, residual current and tidal energy via modulating tides. The ebb dominance decreased when the tidal flat＇s slope at the Tie inlet was changed. Decreased/increased ebb dominance occurred when the tidal flat＇s slope was reduced/increased at the Xihu inlet. The residual current and tidal energy density was amplified/dampened and more/less tidal energy was dissipated, with reduced/increased slope at both of the inlets. The findings in this study are instructive to coastal engineering and estuarine management.

关键词： tidal flat's slope tidal dynamics tidal asymmetry tidal energy Xiangshan Bay

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Numerical modeling of lock-exchange gravity/turbidity currents by a high-order upwinding combined compact difference scheme

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International Journal of Sediment Research 2019年第3期34卷 240-250页

作者： Liang Zhao Ching-Hao Yu zhiguo he Institute of Port Coastal and Offshore Engineering Ocean College Zhejiang University State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University State Key Laboratory of Satellite Ocean Environment Dynamics The Second Institute of Oceanography State Oceanic Administration

This study presents two-dimensional direct numerical simulations for sediment-laden current with higher density propagating forward through a lighter ambient water. The incompressible Navier Stokes equations including the buoyancy force for the density difference between the light and heavy fluids are solved by a finite difference scheme based on a structured mesh. The concentration transport equations are used to explore such rich transport phenomena as gravity and turbidity currents. Within the framework of an Upwinding Combined Compact finite Difference(UCCD) scheme, rigorous determination of weighting coefficients underlies the modified equation analysis and the minimization of the numerical modified wavenumber. This sixth-order UCCD scheme is implemented in a four-point grid stencil to approximate advection and diffusion terms in the concentration transport equations and the first-order derivative terms in the Navier-Stokes equations, which can greatly enhance convective stability and increase dispersive accuracy at the same time. The initial discontinuous concentration field is smoothed by solving a newly proposed heaviside function to prevent numerical instabilities and unreasonable concentration values. A two-step projection method is then applied to obtain the velocity field. The numerical algorithm shows a satisfying ability to capture the generation, development, and dissipation of the Kelvin-helmholz instabilities and turbulent billows at the interface between the current and the ambient fluid. The simulation results also are compared with the data in published literatures and good agreements are found to prove that the present numerical model can well reproduce the propagation,particle deposition, and mixing processes of lock-exchange gravity and turbidity currents.

关键词： Gravity current Turbidity current Depth-resolving mathematical model Incompressible Navier-Stokes equations Upwinding Combined Compact Difference (UCCD) scheme

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Numerical modeling of scour and deposition around permeable cylindrical structures

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International Journal of Sediment Research 2020年第3期35卷 278-286页

作者： Jiajia Pan zhiguo he Wurong Shih Niansheng Cheng Ocean College Zhejiang University Civil and Environmental Engineering.Lehigh University

Flow past wall-mounted cylindrical structures is commonly encountered in natural rivers where piers of bridge crossings or vegetation stalks are common within *** the current study,the influence of cylindrical structures on flow/bathymetric alterations for three different permeabilities is explored via two-dimensional numerical *** model construction processes,the structure permeability is varied with the surface void ratio along the perimeter of the cylinder,*** density of emergent and submerged solid elements is used to delineate the cylinder *** validation of this model is guaranteed through careful comparison with experimental data obtained for similar hydrodynamic conditions and cylinder *** validated model then is applied to investigate flow properties and scour and deposition patterns with structure permeabilities of 0.0,0.38,and *** results show that a permeable structure has less impeding effects on flow than a solid *** wake velocity reduction decreases 38% with a 63% increase in the structure permeability due to increasing intensity of the bleeding flow through surface voids,causing less flow contraction and diversion,lower turbulent kinetic energy,and lower lee-side scour around the permeable structure and less deposition downstream under live-bed conditions.

关键词： Structure permeability Scour and deposition Numerical modeling Flow characteristics

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Implementation of an efficient segregated algorithm-IDEAL on 3D collocated grid system

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Chinese Science Bulletin 2009年第6期54卷 929-942页

作者： SUN DongLiang QU zhiguo he YaLing Tao WenQuan State Key Laboratory of Multiphase Flow in Power Engineering School of Energy & Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The segregated algorithm-IDEAL (inner doubly-iterative efficient algorithm for linked-equations) is an efficient and stable algorithm. In this algorithm, there exist inner doubly-iterative processes for pres-sure equation, which almost completely overcome two approximations in SIMPLE algorithm. Thus the coupling between velocity and pressure is fully guaranteed, greatly enhancing the convergence rate and stability of iteration process. In this paper, implementation of the IDEAL algorithm on a 3D collo-cated grid system is conducted. The interface velocity is calculated by the modified momentum inter-polation method (MMIM), by which the converged result is independent of the under-relaxation factor. Finally, five three-dimensional incompressible fluid flow and heat transfer problems are provided to compare the convergence rate and robustness between the IDEAL and three other most widely-used algorithms (SIMPLER, SIMPLEC and PISO). By the comparison it can be concluded that the IDEAL al-gorithm is more robust and efficient than the three other algorithms.

关键词：隔离算法网格系统理想 SIMPLE算法 3D 压力方程收敛速度迭代过程

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Variations of temperature, salinity and current in the southern tidal passage of the Hangzhou Bay, China

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Acta Oceanologica Sinica 2016年第3期35卷 30-37页

作者： he zhiguo HUANGFU Kailong YUAN Yeping SONG Dan LI Li Ocean College Zhejiang University State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyState Oceanic Administration

Field surveys covering a spring-neap tidal period were conducted to investigate the characteristics of tidal dynamics within a curved channel in the southern Hangzhou Bay, China. The channel has a maximum depth of more than 100 m with an average tidal range of 2.5 m, serving as the main tidal passage in the southern part of the Hangzhou Bay. Water salinity, temperature and velocity data were collected from the ship-based transects and mooring measurements. During flood tide, the tidal current intrudes into the Hangzhou Bay through the northern side of the channel with a maximum velocity of about 2 m/s, while retreats through the southern side during ebb tide with a maximum velocity of 1.8 m/s. Due to the pressure, density gradients, the Coriolis force and centrifugal effect, a lateral exchange flow is generated as the tidal current relaxes from flood to ebb. Salinity and temperature data show that the water in the channel is weakly stratified during both spring and neap tides in summer ***, mixing in the middle region will be enhanced by the lateral circulation. Mooring data indicate that the temperature and salinity are varying at a frequency similar to tidal current but higher than sea level *** results support the hypothesis that the high frequency salinity and temperature variations could be generated by combination of the tidal current and the lateral exchanging flow.

关键词： macro-tidal estuary mooring observations temperature and salinity variations tidal current curved channel

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Study on a Gas Plunger Lift Model for Shale Gas Wells and Its Effective Application

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Fluid Dynamics & Materials Processing 2022年第4期18卷 933-955页

作者： Peng Liu Man Chen zhiguo he Wei Luo Shiyu Miao Sichuan Changning Gas Development Company PetroChina Southwest Oil&Gas Field CompanyChengdu610051China Petroleum Engineering Institute of Yangtze University Wuhan430100China Key Laboratory of Drilling and Production Engineering for Oil and Gas Yangtze UniversityWuhan430100China

The problem of efficient gas lift for gas well annulus packers that rely on their own energy plungers is *** complex related gas-liquid problem is addressed in the frame of model where the gas inflow dynamics and liquid inflow dynamics of the considered shale gas wells are weakly *** this basis,and with the aiding support of indoor simulation experimental data,a new gas plunger lift design taking into account liquid leakage is ***,a dedicated software relying on this approach is developed and used to verify the reliability of the model by means of field examples.

关键词： Packers their own energy plungers shale gas wells weakly coupled liquid leakage

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Numerical simulation of dam-break flow and bed change considering the vegetation effects

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International Journal of Sediment Research 2017年第1期32卷 105-120页

作者： zhiguo he Ting Wu Haoxuan Weng Peng Hu Gangfeng Wu Ocean College Zhejiang University State Key Laboratory of Satellite Ocean Environment Dynamics Zhejiang Guangchuan Engineering Consulting Co.Ltd.

Existing numerical investigations of dam-break flows rarely consider the effects of *** paper presents a depth-averaged two-dimensional model for dam-break flows over mobile and vegetated *** the model,both the consequences of reducing space for storing mass and momentum by the existence of vegetation and dragging the flow are considered:the former is considered by introducing a factor(1-c) to the flow depth,where c is the vegetation density;the later is considered by including an additional sink term in the momentum *** new governing equations are discretized by the finite volume method;and an existing second-order central-upwind scheme embedded with the hydrostatic reconstruction method for water depth,is used to estimate the fluxes;the source terms are estimated by either explicit or semi-explicit methods fulfilling the stability *** experiments of dam-break flows or quasi-steady flows with/without vegetation effects/sediment transport are *** good agreements between the measurements and the numerical simulations demonstrate a satisfactory performance of the model in reproducing the flow depth,velocity and bed deformation *** case studies of six scenarios of dam-break flows over a mobile and vegetated bed are *** is shown that when the area of the vegetation zone,the vegetation density,and the pattern of the vegetation distribution are varied,the resulted bed morphological change differs greatly,suggesting a great influence of vegetation on the dam-break flow ***,the vegetation may divert the direction of the main flow,hindering the flow and thus result in increased deposition upstream of the vegetation.

关键词： Dam-break flow Sediment transport Vegetation effects Numerical modeling

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Surface pollen assemblages of human-disturbed vegetation and their relationship with vegetation and climate in Northeast China

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Chinese Science Bulletin 2012年第5期57卷 535-547页

作者： LI ManYue LI YueCong XU QingHai PANG RuiMing DING Wei ZHANG ShengRui he zhiguo College of Resources and Environment and hebei Key Laboratory of Environmental Change and Ecological Construction Hebei Normal UniversityShijiazhuang 050024China

Pollen assemblages of 53 surface pollen samples from farmlands and wastelands in Northeast China were analyzed. Tree pollen percentages were usually higher than 30%, with Pinus (26.9%), Quercus (0.9%), Betula (0.9%) and Populus (0.7%) as the major types, and herb pollen percentages were usually higher than 50%, with weedy Poaceae (8.7%), Chenopodiaceae (7.1%), Artemisia (1.9%) and Compositae (3.5%) as the major taxa. Thus, the pollen assemblages were consistent with the regional vegetation compositions. However, there were differences in pollen assemblages among regions, especially among different geomorphological units. For example, in the mountains, there were more types of tree pollen and higher total percentages (average 42%) than in other areas, while cereal pollen percentages were lowest (11.2%). In the hills and high plains, herbs made up more than 60% of the pollens, with cereals (average 53.6%) the dominant type. In the low plains, pollen types were similar to those in the hills and high plains, but total pollen concentrations and the proportion of Concentricystes were much higher, while cereal pollen percentages were slightly lower (average 41.6%). Pollen assemblages in different land use types also differed. For example, in farmland, cereal pollen percentages were more than 40% and Chenopodiaceae was usually less than 2.5%, while in wasteland, weedy Poaceae was usually less than 10% and Chenopodiaceae was usually higher than 25%. Total pollen concentrations in farmland (average 3909 grains/g) were much lower than in wasteland (average 15074 grains/g). Redundancy analysis revealed that pollen assemblages were significantly negatively correlated with mean annual temperature (-0.73) and July mean temperature (-0.81) and significantly positively correlated with mean annual precipitation (0.48), indicating that pollen assemblages in the artificial or human-disturbed vegetation reflect regional climate well. Comparison of pollen assemblages in different areas o

关键词：中国东北地区花粉组合植被组成区域气候人为干扰年平均气温禾本科杂草花粉浓度

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Palaeogeothermal response and record of the effusing of Emeishan basalts in the Sichuan basin

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Chinese Science Bulletin 2010年第10期55卷 949-956页

作者： ZHU ChuanQing XU Ming YUAN YuSon ZHAO YongQing SHAN JingNan he zhiguo TIAN YunTao HU ShengBiao Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China The Graduate University of Chinese Academy of Sciences Beijing 100049 China Exploration and Production Research Institute SINOPEC Beijing 100083 China Exploration Department of South Company of Prospecting SINOPEC Chengdu 610041 China Exploration and Development Research Institute of SINOPEC Southwest Branch Chengdu 610081 China

Thermal history of the Sichuan basin is reconstructed based on vitrinite reflectance from boreholes in the basin using a paleo-heat flow *** results show that the Sichuan basin experienced a relatively low heat flow period in the Early Paleozoic,and an elevated paleo-heat flow,ranging 60-80 mW/m2 with a maximum as high as 100 mW/m2 around 259 Ma,from the beginning of the Late Paleozoic to the end of the early Permian,and a decreased paleo-heat flow from the late Permian to the late Triassic,and then maintained nearly stable to the *** Late Paleozoic paleo-heat flow was quite high where there were extensive Emeishan flood basalts or concealed basalts which erupted between the early and the late Permian,such as the southwestern and northeastern areas of the Sichuan *** to the distribution of paleo-heat flow,it can be inferred that,the northeastern Sichuan basin was also influenced by the Emeishan magmatic activity during the Dongwu movement though there was lack of Emeishan flood *** addition,the results of thermal history reconstruction of the Sichuan basin provide paleogeothermal evidence for the existence and onset of the Emaishan mantle plume.

关键词：四川盆地东北部峨眉山玄武岩盆地热史古地温涌出反应镜质组反射率晚古生代

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Hydrodynamics of high-speed robots driven by the combustion-enabled transient driving method

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2022年第10期23卷 820-831页

作者： Yang YANG Yingzhong LOU Guanzheng LIN zhiguo he Pengcheng JIAO Hainan Institute Zhejiang UniversitySanya 572000China Institute of Port Coastal and Offshore EngineeringOcean CollegeZhejiang UniversityZhoushan 316021China Department of Civil and Environmental Engineering University of WashingtonSeatleWA98195USA Engineering Research Center of Oceanic Sensing Technology and Equipment of Ministry of Education Zhejiang UniversityZhoushan316021China Department of Electronic Engineering Faculty of EngineeringThe Chinese University of Hong KongHong Kong 999077China

Underwater vehicles play important roles in underwater observation, ocean resource exploration, and sample *** robots are a unique type of underwater vehicles due to their good environmental adaptability and motion flexibility, although they are weak in terms of actuation and response ability. The transient driving method(TDM) was developed to resolve these shortcomings. However, the interaction between the robots’ swift motions and flow fields has not yet been fully studied. In this study, a computational fluid dynamic model is developed to simulate the fluid fields disturbed by transient high-speed motions generated by the robots. Focusing on the dependence of robot dynamics on thrust force and eccentricity, typical structures of both flow and turbulence fields around the robots are obtained to quantitatively analyze robot kinematic performance, velocity distribution, vortex systems, surface pressure, and turbulence. The results demonstrate the high-speed regions at the robots’ heads and tails and the vortex systems due to sudden expansion, indicating a negative relationship between the maximum fluid velocity and eccentricity. The reported results provide useful information for studying the environmental interaction abilities of robots during operating acceleration and steering tasks.

关键词： Underwater vehicle Computational fluid dynamics(CFD) Robotics Transient driving method(TDM) Combustion actuation Hydrodynamics

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