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| 1 | Flow dynamics and sediment transport in vegetated rivers:A review显示文摘The significance of riparian vegetation on river flow and material transport is not in dispute.Conveyance laws,sediment erosion and deposition,and element cycling must all be adjusted from their canonical rough-wall boundary layer to accommodate the presence of aquatic plants.In turn,the growth and colonization of riparian vegetation are affected by fluvial processes and river morphology on longer time scales.These interactions and feedbacks at multiple time scales are now drawing significant attention within the research community given their relevance to river restoration.For this reason,a review summarizing methods,general laws,qualitative cognition,and quantitative models regarding the interplay between aquatic plants,flow dynamics,and sediment transport in vegetated rivers is in order.Shortcomings,pitfalls,knowledge gaps,and daunting challenges to the current state of knowledge are also covered.As a multidisciplinary research topic,a future research agenda and opportunities pertinent to river management and enhancement of ecosystem services are also highlighted. | Wen-xin Huai Shuolin Li Gabriel G.Katul Meng-yang Liu Zhong-hua Yang | 2021 | Journal of Hydrodynamics2021，33，3： | 20 |
| 2 | Mean flow and turbulence structure of open channel flow with suspended vegetation显示文摘In combination with a channel bed,suspended vegetationin an open channel can alter flow structure and generate vertically asymmetric flow.This study investigated the mean flow and turbulence structure of an open channel with suspended vegetation through theoretical analysis and laboratory experiments.Three patterns of bionic leaves with different roughness were adopted to imitate suspended vegetation,and three-dimensional velocity field was measured by using an acoustic Doppler velocimeter.The measured data showed that the vertical profile of streamwise velocity obeys a two-power law and that the maximum velocity at the middle depth is close to the smooth boundary(i.e.,the channel bed in the experiment)under the combined action of vegetation cover and channel bed.Shear stress is linearly distributed along the vertical axis,and the vertical profile of turbulence intensity obeys an exponential law.Then,a two-power law expression was adopted to predict the vertical profile of streamwise velocity.Theoretical models for the vertical distribution of shear stress and turbulence intensity were also established.The predicted results validated by measurements showed that the different magnitudes of vegetation cover and channel bed boundary roughness exert an obvious impact on flow structure. | Qian Li Yu-hong Zeng Yu Bai | 2020 | Journal of Hydrodynamics2020，32，2： | 6 |
| 3 | Investigation on the relationship between hydraulic loss and vortex evolution in pump mode of a pump-turbine显示文摘Hydraulic loss and vorticity are two most common methods in analyzing the flow characteristics in hydro-machine,i.e.,centrifugal pump,Francis turbine,etc.While the relationship and correlation between hydraulic loss and vortex evolution are not uncovered yet.In this study,hydraulic loss is regarded as the combination of dissipation effect and transportation effect in flow domains.Meanwhile,vorticityωcan be decomposed into two parts,namely the Liutex partω_(R),the shear partωs,of whichω_(R)is regarded as the third-generation vortex identification method for its precise and rigorous definition of local rigid rotation part of fluid.Based on the dimensional analysis,two new physical quantities related to vorticity(ω,ω_(R)andωS),namely enstrophyΩ,vorticity transport intensity T are adopted to express the energy characteristic in vortex evolution process.Finally,operating points at pump mode of an ultra-high head reversible pump-turbine are selected as the research object and the numerical results calculated using SST k-ωturbulence model are consistent well with the experimental data.Pearson correlation coefficient is adopted to evaluate the correlation between hydraulic loss and vortex evolution in main flow regions.Results show that apart from the spiral casing domain,the enstrophy of shear partΩs has very strong correlation with dissipation effect and Liutex transport intensity TR has stronger correlation with transportation effect when compared with other forms of vorticity.The correlation between Liutex transport intensity TR and transportation effect is strong in stay/guide vanes(SGVs)while reduce to medium level in runner and draft tube domains.In spiral casing domain,all forms of vorticity show weak or very weak correlation with transportation effect.Based on the proposed method,we believe that the relationship and correlation between hydraulic loss and vortex evolution in other hydraulic machineries can also be clearly investigated. | Yong-lin Qin De-you Li Hong-jie Wang Zhan-sheng Liu Xian-zhu Wei Xiao-hang Wang | 2022 | Journal of Hydrodynamics2022，34，4： | 3 |
| 4 | Numerical investigation of flow with floating vegetation island显示文摘Floating vegetation island(FVI)provides an effective way to remove excessive nutrition and pollutants in rivers.The Reynolds stress model(RSM)is employed to investigate the hydrodynamic characteristics induced by varied canopy densities of FVI in an open channel.In longitudinal direction,four regions are subdivided according to the flow development process:upstream adjustment region(LUD),diverging flow region(LDF),shear layer growth region(LSD),and flilly developed region.The increasing canopy density accelerates the flow adjustment in the diverging flow region and shear layer growth region,signaling a shorter distance to reach an equilibrium stage,while LUD keeps a constant.The vertical profiles of the normalized velocity are found to be self-similar downstream of the diverging flow region.In the vertical direction,the streamwise velocity profiles in the mixing layer collapse for all densities and obey the hyperbolic tangent law.Normalized penetration depth into the canopy was fitted as a function of dimensionless canopy density given by δc/hc=0.404(CDahc)^-0.316.This finding indicates a large space for rapid water renewal between the canopy region and the underlying water driven by the shear-scale vortices.In the lateral direction,the intensification of secondary current and the increasing number of secondary current cells with increasing canopy density reveal that dense floating canopies contribute to strong momentum exchange.The centers of vortices move as canopy density increases,while the vortices in canopy region do not merge with those in the gap region,as limited by the height and width of the canopy region.The distribution of longitudinal velocity in the transects is significantly influenced by secondary current. | Yi-dan Ai Meng-yang Liu Wen-xin Huai | 2020 | Journal of Hydrodynamics2020，32，1： | 2 |
| 5 | Wake flow and vortex structures behind emergent vegetation patches elongated in the longitudinal direction显示文摘In natural rivers,patches of vegetation generally expand over their steady wake region in the streamwise direction,forming elongated patches with length(L)greater than their width(b).This paper studies how the wake flows and the vortices develop as the emergent patches expand their length in the streamwise direction.The patches are modeled with the same width but different lengths in laboratory experiments.Behind the patches,the steady wake region(L_(w))is not related to the width-related flow blockage(C_(d)ab),where C_(d) is the drag coefficient,a is the vegetation density.Instead,L_(w) is related to the length-related flow blockage(C_(d)aL).On this basis,a model is proposed for predicting L_(w),which is in good agreement with the measurements.As a patch becomes denser and/or longer(as C_(d)aL increases),the steady wake region becomes shorter(L_(w) decreases),and vortices are observed closer to the patch trailing edge,producing a turbulence of a greater magnitude beyond L_(w).When the flow blockage increases to the limit(C_(d)aL>8),the Karman vortices are observed directly behind the porous patches.These results can be used to explain the longitudinal elongation of the vegetation patches in the field. | Zi-jian Yu Yu-qi Shan Chao Liu Xing-nian Liu | 2021 | Journal of Hydrodynamics2021，33，6： | 1 |
| 6 | Purification efficiency of ecological spur dikes for river pollutants in different geometric arrangements:Experiments and numerical modeling显示文摘The traditional ecological spur dike is improved,by using the biological fillers such as the plant materials,combined with microorganisms,to obtain a larger water purification capacity.Most of the researches on spur dikes focused on the hydrodynamic force and the migration and the diffusion of the pollutants,but not so much on the effects of the spur dike materials and the arrangement parameters on the water purification capacity.In this paper the biological zeolite is used to make ecological spur dikes.The laboratory flume experiment shows that compared with the natural zeolite spur dike,the purification effect of the biological zeolite spur dike is significantly improved,and the average removal rate of the NH3-N is kept at 6.8%after 24 h compared with 3.5%of the natural zeolite spur dike.The NH3-N removal rates of a single spur dike,the counterpart spur dikes and the staggered spur dikes decrease with the increase of the inlet flow,and the staggered spur dikes have the best purification effect.Secondly,a numerical model based on the MIKE21 is verified by the experimental results and applied for the Tangjiali Section of the Xutangqiao River in Xinwu District,Wuxi City,Jiangsu Province.The orthogonal test shows that the length of the spur dike has the most important effect on the interception of pollutants and the purification,followed by the angle of the spur dike and the spacing of the spur dikes has the least important effect.The geometric arrangement parameters of the ecological spur dike group with the highest efficiency on the pollutant interception and the purification are:60°(angle),6.7 m(length)and 20 m(spacing). | Yi-tian Chen Xiao-ling Wang Song-min Li Ya-zhi Zheng Guang-yao Dong | 2022 | Journal of Hydrodynamics2022，34，5： | 1 |
| 7 | Dispersion features of pollutants in a compound channel with vegetated floodplains显示文摘The planting of the vegetation on the floodplain helps the ecological restoration,which is the main form of the river’s ecological corridor.Therefore,the current research of the river dynamics focuses on the water movement under a compound channel with the vegetated floodplains.Two simulated vegetation species are selected in this paper for the flume simulation experiments of the floodplain vegetation,and the compound channel is divided into three subregions in the transverse direction.The Navier-Stokes equation and the eddy viscosity theory are applied to obtain the transverse distribution of the depth-averaged velocity and the results agree well with the experimental data.This paper proposes a new method based on the analytical solution of the flow velocity distribution to calculate the average flow velocity in each section.Calculation results can effectively simulate the average flow velocity of the measured sections.The description of the pollutant transport processes in a moving stream requires a refined determination of the dispersion coefficients in the compound channel.The process of the pollutant concentrations in each zone and the reasons for their occurrence are elucidated on the basis of the experimental results.Simultaneously,the measured values of the longitudinal dispersion coefficients are obtained by the“routing procedure,”and a two-zone model of the pollutant dispersion is constructed on the basis of the hydrodynamic study.The prediction method for the longitudinal dispersion coefficients is also presented.Applying the predicted and measured section average flow velocities to the two-zone model to predict the longitudinal dispersion coefficient,and the average relative errors are only 4.17%,7.15%,respectively.This result indicates that the two-zone model can effectively predict the longitudinal dispersion coefficients.The calculation methods for the longitudinal dispersion coefficients from—various studies are compared.The results reveal that the predicted values of these calculation methods are all larger than the measured values,indicating that the vegetation has a considerable influence on the dispersion process.This study comprehensively shows the dispersion features of the pollutants and provides a theoretical basis for the planning and the design of the vegetated ecological corridors. | Yan-fang Zhao Jing-jing Fan Wei-jie Wang Han-qing Zhao Fei Dong Zhen Han Shi-yan Wang | 2022 | Journal of Hydrodynamics2022，34，6： | 1 |
| 8 | 含刚性漂浮植被群河道水流特性试验研究显示文摘水生漂浮植被常见于天然河流中,降低河流的过流能力,改变了水流结构,使得水流形态更为复杂。为了探究漂浮植被群作用下的水流特性,使用直径为0.01m的圆形玻璃棒模拟刚性漂浮植被,利用高速粒子图像测速仪(PIV)和无线超声波水位测量系统分别对流速和水位进行测量,通过水槽试验探究植被根系入水深度、植被布置方式、植被群密度对水流特性的影响。试验结果表明,漂浮植被对水流结构的影响较大。在水槽中布置漂浮植被群后,植被区最大水流流速沿垂向出现在植被群根部与水槽床面中间位置;最大紊流强度出现在植被群根部及床面附近区域,而最小紊动强度出现在植被群根部与水槽床面中间位置;当植被群根系入水深度增大时,植被群上游水面壅高和水面纵比降越大、植被群底部以下水流流速相应增大,但紊动强度变化幅度减小;沿水流方向,植被群同侧布置流速产生“增强效应”,异侧布置流速产生“减弱效应”;最强紊动强度发生在植被区与无植被区交界处;随着植被密度的增加,流速的变化幅度增强,紊动强度变小。植被根部下方自由水流区的流速随植被密度增大而增大,植被根部上方区域流速随植被密度增大而减小,流速沿垂向呈“S”型分布。 | 周弋玲 景何仿 王维红 陈秋同 | 2023 | 中国农村水利水电2023，，8： | 0 |
| 9 | Evaluation of vortex evolution and energy loss within the impeller of a side channel pump显示文摘Side channel pumps can provide a huge pressure boost at very low specific speeds,making them useful in various industrial operations.Due to its very complex flow pattern,the high hydraulic head is often accompanied by lower efficiency and higher flow losses.In addition,the shape of the impeller has a direct influence on the flow pattern of the pump as well as the energy conversion that takes place,and this has a substantial bearing on the overall performance of the pump.Thus,to gain a deeper comprehension of the flow behavior and deep-seated reasons for performance optimization in side channel pumps with different geometry parameters.Extensive research has been conducted on the vortex formations and entropy production that occur inside the flow channels of the impeller.Three alternative impeller configurations were systematically created for in-depth research,each including a different suction angle for the blades.According to the data,the head of the side channel pump rises together with an increase in the suction angle,and this rule is exhibited in the whole working condition,and the most effective blade suction angle isθ=30°,which is the greatest of the available options.The vortex area and intensity have an obvious decrease when the suction angle increases to 30°,which is the main reason for the performance optimization.This paper firstly introduces the wall friction dissipation into the research on the side channel pump.Compared with turbulence dissipation and direct dissipation,the wall friction dissipation is far less than turbulence dissipation but far higher than direct dissipation that should not be neglected,although it also increases with the suction angle elevation.As the primary dissipation,the tendency of turbulence dissipation is upward with the performance increase,which is opposite to the common vane pump.The reason for this phenomenon is probably due to the deviation of the primary and secondary flow pattern in the side channel pump.As a result,this will assist to increase the performance and operational dependability of side channel pumps,which will ultimately lead to an expansion of the applications for these pumps. | Ke Chen Fan Zhang Yu-jian Fang Desmond Appiah Shou-qi Yuan Feng Hong | 2023 | Journal of Hydrodynamics2023，35，2： | 0 |
| 10 | Local hydraulic jump effects on sediment deposition in open-channel flume experiments显示文摘When a river channel is narrow,bifurcated,or intersected,or when extreme weather or geological disasters cause shed rock masses to occupy a river flood channel,local hydraulic jumps may develop in the channel.Natural disasters such as landslides,floods,and debris flows occur upstream,will result in large transport rate of large-sized gravel particles.Those particles may be blocked in hydraulic jump areas,causing river channel water depth to rise.In this study,the effect of local hydraulic jumps on the sediment deposition rate was investigated in flume experiments.The ratio of upstream and downstream Froude numbers,particle size,Sediment supply intensity,and flow discharge all affected the sediment deposition rate.With increases in the ratio of upstream and downstream Froude numbers,particle size,and sediment supply intensity,the sediment deposition rate increased.The sediment deposition rate decreased with an increase in flow discharge.Approach hydraulic conditions and particle properties jointly determined the sediment deposition rate in a hydraulic jump section,and an empirical formula was developed using those parameters to calculate the sediment deposition rate.Thus,to identify risks and prevent disasters in mountain rivers,local changes in hydraulic conditions and particle properties need to be jointly evaluated. | Shi-hao Fu Mao-lin Zhou Wei-lin Xu Wang-ru Wei Guo-guang Wang | 2023 | Journal of Hydrodynamics2023，35，2： | 0 |
| 11 | 刚性植被群对连续弯道水力特性的影响研究显示文摘为了探究植被对天然弯曲河流水力特性的影响,通过连续弯曲水槽试验,设计均匀、簇状两种布设形式分别模拟人工规律种植以及自然丛生的植被群,对比分析不同的布设形式对弯道水流流场、水动力轴线、紊动能分布的影响。结果表明:①连续弯槽中水流流场出现明显的流速分区:高流速区靠近凸岸,低流速区则分布在凹岸附近;底层水流与表层水流相比,高流速区分布范围扩大,低流速区减小;布设植被后高流速区分布范围增加,低流速区则剧减,且簇状布设的影响幅度明显大于均匀布设。②连续弯槽水流的水动力轴线偏离正常位置,其沿程表现出先贴近凸岸后脱离凸岸的动态变化过程;植被布设大大延缓了该进程,且簇状布设的延缓程度大于均匀布设。③连续弯槽水流的紊动能沿程分布呈现出不均匀性,最大值出现在弯顶附近区域;从紊动能数值变化可知,植被布设使得水流的紊动能普遍增加,且簇状布设的影响程度大于均匀布设。 | 孙雪岚 张朝瑜 白玉川 段京京 冀自青 | 2023 | 中国农村水利水电2023，，6： | 0 |
| 12 | Effect of Stokes number on energy modulation of the fluid in turbulent particle-laden channel flows显示文摘The effect of Stokes number on the kinetic energy(KE)budget in particle-laden turbulent channel flows is examined by conducting two-way coupled direct numerical simulations using the Eulerian-Lagrangian approach.The friction Reynolds number of the single phase channel flow is Re_(τ)=180,the particle mass loading and volume fraction areφ_(m)=0.2,φ_(v)≈10−4,and the Stokes numbers range from St^(+)=14–92.The statistics show that due to the presence of solid particles,the mean velocity is reduced in the vicinity of the wall but enhanced in the outer region,and the off-streamwise intensity of fluctuated velocity and the Reynolds stress are reduced in the whole channel.The analysis on the budgets of turbulent kinetic energy(TKE)finds that the presence of particles induces a significant reduction on both the production and dissipation rates.With increasing Stokes number St^(+),both the production and dissipation rates exhibit non-monotonical trends,i.e.,both initially decrease for St^(+)<40 and then transit to growth after St^(+)>40.This suggests that the particle-induced suppression on TKE production and dissipation is the strongest nearly at St^(+)=40.It is also found that particles act as an additional sink/source term in the budgets of both mean-flow kinetic energy(MKE)and TKE.In addition,we investigate the influence of St^(+)on the“zero point”which indicates the balance of exchanging energy between the particle and fluid phases.It is shown that with increasing St^(+),the“zero point”moves toward the wall,suggesting that the position of perfect following between particle and fluid is closer to the wall with larger St^(+).The present results reveal the Stokes number effects on the spatial transport mechanisms of MKE,TKE in turbulent channel flows laden with inertial particles. | Zhi-feng Wu Jian-zhao Wu Bo-fu Wang Zhi-ming Lu | 2022 | Journal of Hydrodynamics2022，34，3： | 0 |
| 13 | The velocity patterns in rigid and mobile channels with vegetation patches显示文摘The hydraulic characteristics in an open channel with vegetation are very important in controlling the environment pollution and restoring the river ecology. This paper studies the influence of the bed form and the vegetation patch density on the spatial velocity pattern. Rigid fiberglass circular cylinders are used to simulate the vegetation and a 3-D acoustic Doppler velocimeter (ADV) is used to measure the local flow velocities. Two types of bed forms and a series of vegetation patch densities are considered. The experimental results show that the bed form significantly influences the vertical distribution of the streamwise velocity. Besides, the velocity is affected by the bed form while the lateral distribution shape of the streamwise velocity as well as the lateral and longitudinal distribution shapes of the depth-averaged velocity is less affected. When all test conditions but the bed condition remain the same, as a result of the water energy consumption by the sediment movement, the velocity in the mobile bed case is smaller than that in the rigid bed case. The vegetation patch density has a significant effect on the flow velocity. The distributions of the flow velocity at different locations show different trends with the increase of the vegetation patch density. The upstream adjustment length is not affected by the vegetation patch density, but the steady wake length is very much affected. | Bao-liang Ren Dan Wang Wen-qi Li Ke-jun Yang | 2020 | Journal of Hydrodynamics2020，32，3： | 0 |
| 14 | 3-D numerical simulation of curved open channel confluence flow with partially non-submerged rigid vegetation显示文摘For the study of the effects of partially non-submerged rigid vegetation on the free-surface confluence flow in a curved open channel,a numerical simulation is carried out by using the Volume of Fluid model combined with the porous media model with the software OpenFOAM.The model is first validated by using available experimental measurement data with a good agreement.Then,the characteristics of the separation zone generated by the centrifugal forces and the confluence flow are analyzed.Due to the resistance created by the vegetation,the velocities in the separation zone are more chaotic and the separation zone becomes smaller and more irregular.The reduction of the separation zone area of the vegetated flow in the convex bank is more significant than that in the concave bank.The velocities in the vegetated region become much smaller and remains so in the downstream flow after the vegetation region.Meanwhile,the vegetation compresses and divides the circulations in the flow area,rebuilding a structure with smaller circulations in the main flow and unclear circulations in the vegetation region.In addition,the bed wall shear stresses are significantly smaller in the vegetation region and the separation zone compared to the non-vegetated flow.This implies that the vegetation can have the effect of protecting the river bed from erosion. | Zheng-rui Shi Cong-fang Ai Sheng Jin | 2021 | Journal of Hydrodynamics2021，33，5： | 0 |
| 15 | Velocity and turbulence characteristics in an open channel with multi-row staggered vegetation patches显示文摘A staggered distribution of vegetation is very common in nature,which might significantly affect the flow structure.To investigate its impact,three rows of staggered vegetation groups are designed under seven different working conditions.The horizontal and vertical distances between the vegetation groups are constant,while the vegetation density is variable.The flow field is measured by the acoustic Doppler velocimeter(ADV).It is indicated that both the patch exit velocity and the steady wake velocity decrease with the increase of the density,which is also related to the vegetation rows.Except for the first patch,the upstream adjustment regions of all patches are diminished to some extent,due to the effect of the contralateral patch.The steady wake region also shows a decreasing trend,with a reduction of 0.5D each time when the water flows through the patch.This means that the flow structure is also affected by the number of vegetation rows.The intensity of the turbulence increases along the channel and has a non-axisymmetric distribution similar to that of the velocity.The Karman vortex street generated by the patches on the same side would merge into a larger vortex street.Depending on its intensity,the vegetation at the back has different effects on the vortex street. | Hong-sheng Fu Dan Wang Wen-qi Li Bao-liang Ren Ke-jun Yang | 2021 | Journal of Hydrodynamics2021，33，5： | 0 |
| 16 | Numerical investigation of shallow wake behind a patch of rigid emergent vegetation显示文摘The shallow water flow through and around a patch of rigid emergent vegetation was investigated numerically. The mean flow field and turbulent structures were studied, especially their dependence on the solid volume fraction (SVF) of the patch and the bed friction. Two streamwise velocity scales, U1s at the starting point of the steady wake and U1e at the downstream end of the steady wake, and the length of the steady wake L1 were used to describe the steady wake behind the patch. U1s was found to be related to SVF only. However, U1e and L1 were influenced by both the SVF and the wake stability parameter S. For a sparse patch, U1e was equal to U1s, and L1 decreased with the increase of S. For a mid-dense patch, U1e was always smaller than U1s, and it increased with S and gradually approached U1s. The increase of U1e reduced the lateral velocity difference between the flows inside and outside the wake, which resulted in the increase of L1. For a highly dense patch, U1e and L1 did not increase unless S was larger than a critical value. A new parameter, r, was proposed to represent the development rate of the steady wake. The numerical results showed that r increased monotonously with S for mid-dense patches. | Jian Wang Jing-xin Zhang Dongfang Liang Lian Gan | 2021 | Journal of Hydrodynamics2021，33，4： | 0 |
| 17 | Study on the flow field uniformity of hydro-floating ship lift combined type hydraulic-driven system based on the residual energy theory显示文摘The hydro-floating ship lift originally invented in China is a major innovation in the field of navigation technology.The shaft water levels synchronization of its unique hydraulic-driven system plays a crucial role in reducing the torque of the synchronous shafts and ensuring the safety and stability operation of the ship lift.This study aims to investigate the muti-shaft water level synchronization and the flow velocity uniformity of the combined type hydraulic-driven system.Based on the theory of residual energy,a new index m2 proposed in this study is more suitable for evaluating the flow velocity uniformity of the combined hydraulic-driven system.Finally,the critical value of m2=75 is calculated via the results of the scaled physical mode test as the threshold of water flow uniformity,and it provides a basis for determining the reasonable height of the pressure stabilizing chamber. | Bo Wu Ya-an Hu Shu Xue | 2022 | Journal of Hydrodynamics2022，34，6： | 0 |
| 18 | Numerical investigation of the dynamics of flexible vegetations in turbulent open-channel flows显示文摘Aquatic vegetations widely exist in natural rivers and play an essential role in the evolution of the water environment and ecosystem by changing the river’s hydrodynamic characteristics and transporting sediments and nutrition.In reality,most aquatic vegetations are highly flexible,which invalidates the“rigid-cylinder”assumption widely adopted in many literatures.To explore the dynamics of submerged flexible vegetation in open-channel flows and its feedback to turbulent flow structures,numerical simulations are carried out using an in-house fluid-structure interaction(FSI)solver.In the simulations,the geometry of vegetation plants is grid-resolved,the turbulent flow is simulated using the large eddy simulation(LES),the dynamics of the flexible plants are solved using the vector form intrinsic finite element(VFIFE)method,and the turbulent flow and the plants are two-way coupled using the immersed boundary(IB)method.The dynamic responses of the flexible vegetation with different plant flexibility,spacing,and submergence are investigated.Simulation results show that flexible plants are subjected to complex flow-induced vibrations(FIVs)rather than static bending.The FIV involves both streamwise and cross-flow motions driven by the small-scale vortex shedding around the plants and the large-scale Kelvin-Helmholtz(K-H)vortices developed in the vegetation canopy layer.The vegetations exhibit pulsive wave motion of different patterns in relatively long and narrow open channels.Compared with the open-channel flows with static plants with equivalent bending deformation,the dynamic responses of flexible plants may increase the turbulent Reynolds stress of the open-channel flow by 70%–100%and increase the invasion depth of the K-H vortices by 30%–50%. | Dong Xu Jia-ning Liu Yun-feng Wu Chun-ning Ji | 2022 | Journal of Hydrodynamics2022，34，4： | 0 |
| 19 | Numerical test of scale relations for modelling coastal sandbar migration and inspiration to physical model design显示文摘Physical model experiments on sandbar migration are widely conducted in the wave flume to reveal its hydro-sediment dynamic mechanisms.Selecting an appropriate scale relation is an important part of designing a laboratory experiment.However,evaluating the scale effect is complicated since it is impractical to design wave flume experiments based on strict geometry scales derived from the prototype beach or other laboratory beaches.Here,a process-based numerical model is used to test the Dean and Shields similitudes by comparing sandbar migration and sediment transport in different undistorted model scales using natural sediments.The numerical model provides excellent predictions for both offshore sandbar migration on a real-world beach and onshore sandbar migration in the wave flume.Consistent with previous studies,sandbar offshore migration and suspended sediment transport are similar when the Dean similitude is fulfilled.Sandbar onshore migration and bedload transport can be well reproduced only if the Shields similitude is achieved.Although previous laboratory experiments of sandbar migration generally used the Dean similitude,it is found that the Shields similitude is effective and indispensable for modelling sandbar onshore migration,which will be underestimated if the Dean similitude is only considered.Each scale relation cannot be used simultaneously for modelling both onshore and offshore sandbar migration in physical models. | Yuan Li Chi Zhang Shan-hang Chi Yun-han Yang Jian Shi Ti-ti Sui | 2022 | Journal of Hydrodynamics2022，34，4： | 0 |
| 20 | Instantaneous sediment transport formula for sheet flow beneath asymmetric wave and current显示文摘An instantaneous formula is obtained for the sheet flow transport beneath the wave and the current by a product integration of the concentration and velocity profiles over the mobile seabed. The formula involves: (1) The product of the erosion depth and the free stream velocity, which can be reduced to the Shields parameter of power 3/2 in accordance with the classical formulae. (2) The ratio of the wave boundary layer thickness to the erosion depth. The formula incorporates the effects of the acceleration and the phase lag on the erosion depth, the asymmetric wave boundary layer and the wave-current interaction. The validation of the formula is made by the data obtained from the oscillatory tunnels covering a wide range of wave-current and sediment conditions. The instantaneous sediment transport rate is compared with the power function of the velocity with different exponents. The formula consists of a wave force part and a current force part and their relative importance depends on the wave shapes. The present formula gives very good results for the net sediment transport as compared to several existing steady and unsteady formulae. The net sediment transport rates are affected by not only the acceleration, the phase lag and the wave-current interaction, but also the asymmetric boundary layer development. | Xin-yu Hu Zhong-hua Weng Xin Chen Hai-fei Liu | 2022 | Journal of Hydrodynamics2022，34，4： | 0 |
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