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Predicting submerged vegetation drag with a machine learning-based method

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Journal of Hydrodynamics 2024年第3期36卷 534-545页

作者： Meng-yang Liu Hong-wu Tang Sai-yu Yuan Jing Yan College of water conservancy and hydropower Engineering Hohai UniversityNanjing210098China Key Laboratory of Hydrologic-Cycle and Hydrodynamic-System of Ministry of water Resources Hohai UniversityNanjing210098China

Accurate estimation of the drag forces generated by vegetation stems is crucial for the comprehensive assessment of the impact of aquatic vegetation on hydrodynamic processes in aquatic *** coupling relationship between vegetation layer flow velocity and vegetation drag makes precise prediction of submerged vegetation drag forces particularly *** present study utilized published data on submerged vegetation drag force measurements and employed a genetic programming(GP)algorithm,a machine learning technique,to establish the connection between submerged vegetation drag forces and flow and vegetation *** using the bulk velocity,U,as the reference velocity scale to define the drag coefficient,C_(d),and stem Reynolds number,the GP runs revealed that the drag coefficient of submerged vegetation is related to submergence ratio(H^(*)),aspect ratio(d^(*)),blockage ratio(ψ^(*)),and vegetation density(λ).The relation between vegetation stem drag forces and flow velocity is implicitly embedded in the definition of C_(d).Comparisons with experimental drag force measurements indicate that using the bulk velocity as the reference velocity,as opposed to using the vegetation layer average velocity,U_(v),eliminates the need for complex iterative processes to estimate U_(v)and avoids introducing additional errors associated with U_(v)*** approach significantly enhances the model’s predictive capabilities and results in a simpler and more user-friendly formula expression.

关键词： Drag coefficient genetic programming algorithm submerged vegetation flow resistance cylinder array

Features and formulae of sediment incipient motion in vegetated flow environment

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Journal of Hydrodynamics 2024年第2期36卷 331-339页

作者： Yu-xuan Xu Wei-jie Wang Shi-bao Zhang Han-qing Zhao Xue-kai Chen Hai-ping Zhang School of water conservancy North China University of Water Resources and Electric PowerZhengzhou450045China State Key Laboratory of Simulation and Regulation of water Cycle in River Basin China Institute of Water Resources and Hydropower ResearchBeijing100038China China Three Gorges Corporation Wuhan430010China

Aquatic vegetation is a vital component of natural river ecosystems,playing a crucial role in maintaining ecological balance,providing habitat and improving water ***,the presence of vegetation results in increased resistance in vegetated channels compared with non-vegetated channels,rendering traditional sediment movement predictions inadequate for the ***,the concept of a vegetation influence factor,denoted by CDah,has been proposed by previous researchers to represent the effect of vegetation on sediment movement in *** this study,we focus on exploring the vegetation resistance coefficient(CD)among the vegetation influence factors,evaluating two different calculation methods for vegetation resistance coefficient,and presenting two expressions through genetic algorithm analysis to predict the incipient flow velocity of sediment in vegetated *** predicted values from the new formulae show excellent agreement with measured data,highlighting the high accuracy of the proposed methods in predicting the incipient flow velocity of *** results provide a solid theoretical basis for understanding the influence of aquatic vegetation on sediment particle movement.

关键词： Vegetation flow vegetation resistance coefficient genetic algorithm sediment initiation

Numerical study of submerged bending vegetation under unidirectional flow

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water Science and Engineering 2024年第1期17卷 92-100页

作者： Pei-pei Zhang Yi-qing Gong Ken Vui Chua Jie Dai Jing-qiao Mao College of water conservancy and hydropower Engineering Hohai UniversityNanjing 210098China institute of water Science and Technology Hohai UniversityNanjing 210098China School of Engineering Cardiff UniversityCardiff CF243AAUK

Submerged vegetation commonly grows and plays a vital role in aquatic ecosystems,but it is also regarded as a barrier to the passing *** simulations of flow through and over submerged vegetation were carried out to investigate the effect of vegetation density on flow *** simulations were computationally set up to replicate flume experiments,in which vegetation was mimicked with flexible plastic *** fluid-structure interaction between flow and flexible vegetation was solved by coupling the two modules of the COMSOL *** cases with different vegetation densities were simulated,and the results were successfully validated against the experimental *** contours of the simulated time-averaged streamwise velocity and Reynolds stress were extracted to highlight the differences in mean and turbulent flow *** turbulence intensity was found to be more sensitive to vegetation density than the time-averaged *** developing length increased with the spacing between *** snapshots of the bending vegetation under instantaneous velocity and vorticity revealed that flexible vegetation responded to the effects of eddies in the shear layer by swaying *** first two rows of vegetation suffered stronger approaching flow and were prone to more streamlined *** addition,the origin of tip vortices was investigated via the distribution of *** results reveal the variation of flow properties with bending submerged vegetation and provide useful reference for optimizationofrestorationprojects.

关键词： Computational fluid dynamics Fluid-structure interaction Turbulence Flexible and submerged vegetation

Regulation effects of water and nitrogen on yield,water,and nitrogen use efficiency of wolfberry

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Journal of Arid Land 2024年第1期16卷 29-45页

作者： GAO Yalin QI Guangping MA Yanlin YIN Minhua WANG Jinghai WANG Chen TIAN Rongrong XIAO Feng LU Qiang WANG Jianjun College of water conservancy and hydropower Engineering Gansu Agricultural UniversityLanzhou 730070China Jingtaichuan Electric Power Irrigation water Resource Utilization Center in Gansu Province Baiyin 730900China

Wolfberry(Lycium barbarum L.)is important for health care and ecological ***,it faces problems of low productivity and resource utilization during *** reasonable models for water and nitrogen management is important for solving these *** on field trials in 2021 and 2022,this study analyzed the effects of controlling soil water and nitrogen application levels on wolfberry height,stem diameter,crown width,yield,and water(WUE)and nitrogen use efficiency(NUE).The upper and lower limits of soil water were controlled by the percentage of soil water content to field water capacity(θ_(f)),and four water levels,i.e.,adequate irrigation(W0,75%-85%θ_(f)),mild water deficit(W1,65%-75%θ_(f)),moderate water deficit(W2,55%-65%θ_(f)),and severe water deficit(W3,45%-55%θ_(f))were used,and three nitrogen application levels,i.e.,no nitrogen(N0,0 kg/hm^(2)),low nitrogen(N1,150 kg/hm^(2)),medium nitrogen(N2,300 kg/hm^(2)),and high nitrogen(N3,450 kg/hm^(2))were *** results showed that irrigation and nitrogen application significantly affected plant height,stem diameter,and crown width of wolfberry at different growth stages(Pwater *** weight per hundred grains and dry weight percentage increased with increasing nitrogen application under W0 ***,under other water treatments,the values first increased and then decreased with increasing nitrogen *** and its component of wolfberry first increased and then decreased as water deficit increased under the same nitrogen *** water use efficiency(IWUE,8.46 kg/(hm^(2)·mm)),WUE(6.83 kg/(hm^(2)·mm)),partial factor productivity of nitrogen(PFPN,2.56 kg/kg),and NUE(14.29 kg/kg)reached their highest values in W2N2,W1N2,W1N2,and W1N1 treatments.R

关键词： water deficit growth characteristics yield water and nitrogen use efficiency principal component analysis

Surface water resource attenuation attribution and patterns in Hai River Basin

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Science China Earth Sciences 2024年第5期67卷 1545-1560页

作者： Qingming WANG Yong ZHAO Hao WANG Jiaqi ZHAI Yue ZHANG Fan HE Rong LIU Mengyang MA State Key Laboratory of Simulation and Regulation of water Cycle in River Basin China Institute of Water Resources and Hydropower Research(IWHR)Beijing 100038China Key Laboratory of water Safety for Beijing-Tianjin-Hebei Region of Ministry of water Resources Beijing 100038China General institute of water Resources and hydropower Planning and Design Ministry of Water ResourcesBeijing 100120China

From 1956 to 2016,Hai River Basin suffered the most severe surface water resource attenuation among the 10 first-class river basins in *** on the surface water circulation process,and evolving characteristics of precipitation and underlying surface in Hai River Basin,this study attributed the causes of surface water resource attenuation to six primary impact factors,analyzed each factor's quantitative contribution,and revealed four patterns of surface water resource attenuation in Hai River *** pattern of the dominant factor:comparing the 1980–2000 period with the 1956–1979period,the variation of precipitation is the dominant factor of which contribution is 7 billion m^(3),accounting for 59%of total11.7 billion m^(3);comparing the 2001–2016 period with the 1956–1979 period,the increasing of vegetation cover in mountainous area is the dominant factor of which contribution is 2.78 billion m3,accounting for 51%of total 4.9 billion m^(3).The pattern of spatial distributions:comparing the 2001–2016 period with the 1956–1979 period,mountainous areas were more affected by increasing vegetation cover which for example contributed 42%in Luan River Basin mountainous;the plains were more impacted by farmland ridge interception which for example contributed 51%in Beisi River Basin *** pattern of attenuation trend:comparing the 2001–2016 period with the 1980–2000 period,surface water resources in mountainous areas continued to decline,owing to the increasing water consumption of large-scale vegetation restoration,while the influence of the underlying surface changes on surface water resources in plains areas tended to remain *** pattern of reversible change:among factors led to surface water resource attenuation,the human activity,including vegetation cover increase,farmland ridge interception,and urbanization expansion,contributed 36%of the attenuation,which resulted in the variation of precipitation-runoff *** study improved the traditiona

关键词： Hai River Basin Surface water resources Contribution decomposition Quantitative contribution Attenuation patterns

Dynamic Characteristics of Functionally Graded Timoshenko Beams by Improved Differential Quadrature Method

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Computer Modeling in Engineering & Sciences 2024年第8期140卷 1647-1668页

作者： Xiaojun Huang Liaojun Zhang Hanbo Cui Gaoxing Hu School of Architecture and Civil Engineering Anhui Polytechnic UniversityWuhu241000China College of water conservancy and hydropower Engineering Hohai UniversityNanjing210098China

This study proposes an effective method to enhance the accuracy of the Differential Quadrature Method(DQM)for calculating the dynamic characteristics of functionally graded beams by improving the form of discrete node ***,based on the first-order shear deformation theory,the governing equation of free vibration of a functionally graded beam is transformed into the eigenvalue problem of ordinary differential equations with respect to beam axial displacement,transverse displacement,and cross-sectional rotation angle by considering the effects of shear deformation and rotational inertia of the beam ***,ignoring the shear deformation of the beam section and only considering the effect of the rotational inertia of the section,the governing equation of the beam is transformed into the eigenvalue problem of ordinary differential equations with respect to beam transverse *** on the differential quadrature method theory,the eigenvalue problem of ordinary differential equations is transformed into the eigenvalue problem of standard generalized algebraic ***,the first several natural frequencies of the beam can be *** feasibility and accuracy of the improved DQM are verified using the finite element method(FEM)and combined with the results of relevant literature.

关键词： Timoshenko beams functionally graded materials dynamic characteristics natural frequency improved differential quadrature method

Hydrodynamic characteristics and particle tracking of 90° lateral intakes at an inclined river slope

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water Science and Engineering 2024年第2期17卷 197-208页

作者： Wei He Si-yuan Feng Jian Zhang Hong-wu Tang Yang Xiao Sheng Chen Chun-sheng Liu College of water conservancy and hydropower Engineering Hohai UniversityNanjing 210098China State Key Laboratory of Hydrology water Resources and Hydraulic Engineering Hohai UniversityNanjing 210098China Collaborative Innovation Center on water Safety and water Science Hohai UniversityNanjing 210098China

Lateral intakes are common in *** pump effciency and sediment deposition are determined by the local hydrodynamic characteristics and mainstream division *** hydraulic characteristics of lateral withdrawal from inclined river slopes at different intake elevations should be ***,the division width exhibits significant vertical non-uniformity at an inclined river slope,which should be ***,a three-dimensional(3-D)hydrodynamic and particle-tracking model was developed with the Open Source Field Operation and Manipulation(Open FOAM),and the model was validated with physical model tests for 90°lateral withdrawal from an inclined side *** flow fields,withdrawal sources,and division widths were investigated with different intake bottom elevations,withdrawal discharges,and main channel *** study showed that under inclined side bank conditions,water entered the intake at an oblique angle,causing significant 3-D spiral flows in the intake rather than two-dimensional closed recirculation.A lower withdrawal discharge,a lower bottom elevation of the intake,or a higher main channel velocity could further strengthen this *** average division width and turbulent kinetic energy were smaller under inclined side bank conditions than under vertical bank *** a low intake bottom elevation,a low withdrawal discharge,or a high main channel velocity,the sources of lateral withdrawal were in similar ranges near the local inclined bank in the vertical *** inclined slope conditions,sediment deposition near the intake entrance could be reduced,compared to that under vertical slope *** results provide hydrodynamic and sediment references for engineering designs for natural rivers with inclined terrains.

关键词： Lateral withdrawal Hydrodynamic characteristics Particle tracking Inclined river slope Bottom elevation of intake OpenFOAM

Assessment of runoff changes in the sub-basin of the upper reaches of the Yangtze River basin, China based on multiple methods

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Journal of Arid Land 2024年第4期16卷 461-482页

作者： WANG Xingbo ZHANG Shuanghu TIAN Yiman Department of water Resources China Institute of Water Resources and Hydropower ResearchBeijing 100038China College of Hydrology and water Resources Hohai UniversityNanjing 210098China

Quantitative assessment of the impact of climate variability and human activities on runoff plays a pivotal role in water resource management and maintaining ecosystem *** study considered six sub-basins in the upper reaches of the Yangtze River basin,China,to reveal the trend of the runoff evolution and clarify the driving factors of the changes during 1956–*** regression,Mann-Kendall test,and sliding t-test were used to study the trend of the hydrometeorological elements,while cumulative distance level and ordered clustering methods were applied to identify mutation *** contributions of climate change and human disturbance to runoff changes were quantitatively assessed using three methods,i.e.,the rainfall-runoff relationship method,slope variation method,and variable infiltration capacity(Budyko)hypothesis ***,the availability and stability of the three methods were *** results showed that the runoff in the upper reaches of the Yangtze River basin exhibited a decreasing trend from 1956 to 2020,with an abrupt change in *** attribution analysis,the runoff series could be divided into two phases,i.e.,1961–1985(baseline period)and 1986–2020(changing period);and it was found that the rainfall-runoff relationship method with precipitation as the representative of climate factors had limited usability compared with the other two methods,while the slope variation and Budyko hypothesis methods had highly consistent *** factors showed different effects in the sub-basins of the upper reaches of the Yangtze River ***,human disturbance was the main factor that contributed to the runoff changes,accounting for 53.0%–82.0%;and the contribution of climate factors to the runoff change was 17.0%–47.0%,making it the secondary factor,in which precipitation was the most representative climate *** results provide insights into how climate and anthropogenic changes synergistically influence the runoff of t

关键词： economic belt runoff change influencing assessment climate human activities

Numerical simulation of transient characteristics in a bulb turbine during the load rejection process

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Journal of Hydrodynamics 2024年第1期36卷 170-183页

作者： Yue Lu Yu-quan Zhang Zhong-wei He Yuan Zheng College of water conservancy and hydropower Engineering Hohai UniversityNanjing210098China College of Energy and Electrical Engineering Hohai UniversityNanjing210098China Huadong Engineering Corporation Ltd. Hangzhou311122China

To evaluate the safety of the bulb tubular turbine,the dynamic hydraulic characteristics of a hydropower station system during the load rejection process are studied through numerical simulations and a prototype *** the developed model,a dynamic grid technology(DGT)controls the closure of the guide vane and the blade,whilst the moment balance equation and the user-defined function(UDF)provide the runner’s rotation *** 3-D transient simulation method can well predict the rotation speed and mass flow curves in the state of load *** simulation outcomes of the system performance are basically consistent with the measurement data of the *** observed,the runner is subjected to the reversely increased torque and axial force,the system is in a braking phase,and the maximum speed peaks at 144.6%of the rated ***,the internal flow of the runner is greatly affected by the closure of the guide vane,and the draft tube forms an eccentric spiral vortex *** breaks downstream,aggravating the instability of the draft ***,the transient characteristics span for the first five seconds,demonstrating the importance of establishing an efficient governing *** obtained results are useful for designing the turbine’s flow channel with a double regulating function and comprehending the turbine’s transient characteristics.

关键词： Bulb tubular turbine load rejection numerical simulation dynamic grid prototype test