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| 1 | A study on the stability of laminar open-channel flow over a sandy rippled bed显示文摘The bed of a river often features some kinds of bedform, such as sand ripples, dunes, and so on. Even if the bed is smooth initially, disturbances arising from the bed or other external sources will cause the laminar flow in an open channel to become unstable as soon as the flow develops, thereby leading to the formation of sand ripples on the bed. In return, the formation of the sand ripples will modify the instability path of the laminar flow passing over them. The wavy character of the bed will induce further instability of the flow, which is essentially different from that on a smooth bed: the neutral curve will move forward and the critical Reynolds number will decrease. The flow is unstable in response to a wider range of the disturbance wave number, or the laminar flow instability can happen more easily. The propagation speed of the sand ripples also affects the flow instability, since the stability of open channel flow over a movable bed is fundamentally different from that on a rigid bed. These instability effects are discussed in detail in this paper. | BAI Yuchuan XU Haijue | 2005 | Science China(Technological Sciences)2005，48，1： | 8 |
| 2 | Stability and self-adaption character of turbulence coherent structure in narrow-deep river bend显示文摘In a meandering river,a certain scale of turbulent vortex dominates the development of river morphology,making the river bend with s particular curvature.This kind of vortex is denoted as 'bend-forming vortex'.The coordinated relationship of bend-forming vortex and meandering river channel is then known as 'self-adaption feature' of rivers.With these two concepts,this paper investigated the stability and self-adaption character of coherent vortex in the U-shape river bend with a constant curvature.On the basis of fluid mechanics theory and in consideration of turbulent coherent vortex as disturbance,the growth rate and the wave number response range of coherent vortex in meandering rivers with different curvatures were calculated in this paper.Moreover,the responses of different scales of coherent turbulence structure to river bend parameters were analyzed to explain the mechanism of river bend maintenance.These methods could provide a theoretical basis for further investigation on river meandering. | BAI YuChuan JI ZiQing XU HaiJue | 2012 | Science China(Technological Sciences)2012，55，11： | 5 |
| 3 | The nonlinear theory for sediment ripple dynamic process of straight river显示文摘There are various sand ripples in the natural world.The viewpoint of Yalin is that local disturbances result in laminar instability and in sand-ripple formation,namely,local disturbance→ t he instability of the laminar flow →t he formation of sand ripples.Based on this viewpoint,a theoretical model of the resonant triad interaction and its nonlinear interaction with the sediment is established.The purpose of this model is to explain the formation and evolution of the sand-ripple and allow for analysis of the instability of open-channel flow caused by it and sand-ripple hydro-dynamic process.This model will not only pave a road to explore the mechanism of interaction between bed-form and turbulence,but also provide a good base for the study of aeolian sand-ripple formation. | XU HaiJue BAI YuChuan | 2012 | Science China(Technological Sciences)2012，55，3： | 5 |
| 4 | Theoretical analyses on hydrodynamic instability in narrow deep river with variable curvature显示文摘Bending river is the most common river type in nature, and it is also a typical example for river evolution. The transform of the flow pattern can affect the development of the riverbed form. In return, the variation in the riverbed form can affect the hydrodynamic characteristics of the flow, thereby leading to the continuous evolution of the bending river. Based on this, a theoretical model for the bending river is established. The hydrodynamic instability characteristics of the laminar flow in the channel with a variable curvature, a typical model as the meandering river, are studied,and the variations of some parameters such as the curvature, the wave number, and the wave frequency are also discussed. | Haijue XU Yuchuan BAI | 2015 | Applied Mathematics and Mechanics(English Edition)2015，36，9： | 3 |
| 5 | Stability characteristics of the open channel flow above the asymmetrical irregular sand ripples显示文摘Sandy bed cannot keep its original smoothness as the flows pass. With the increase of the flow intensity, the bed forms will appear as sand ripples and dune in turn. Among these morphologies, the sand ripple scale is the smallest, which is generally symmetrical when it just appears, but as time goes on, the asymmetrical form gradually develops. Just because of this sand ripples asymmetry, it manifests the influence of the flow on the bed morphology and also the impact on the laminar flow dynamical process, especially the stability characteristics. The stability features of laminar flow on open channels with the asymmetrical sand ripples are discussed, and also the results on the symmetrical sand ripples are compared in detail. | XU HaiJue & BAI YuChuan* Institute for Sedimentation River and Coastal Engineering, School of Civil Engineering, Tianjin University, Tianjin 300072, China | 2010 | Science China(Physics,Mechanics & Astronomy)2010，53，8： | 3 |
| 6 | Stability characteristics of hyper-concentration flow in open channel显示文摘The flow instability is related to many engineering problems and belongs to a wide-ranging research field. When the problem on the transition from the laminar to the turbulence caused by the instability of the laminar is studied,the 'neutral line' and the critical Reynolds number are always taken as the criterion to judge whether a certain kind of flow is stable,whose corresponding flow medium is the clear water,that is,the single-phase Newtonian fluid. And it is not studied in the traditional in-stability theory that the hyper-concentration flow widely exists in rivers. This shortage can be covered by this research. Study shows that the instability of non-Newtonian fluid such as hyper-concentration fluid,compared with Newtonian fluid such as clear water,is influenced by not only Reynolds number,the ratio of the inertia force and the viscous force,but also many other factors such as the sediment concentration,the concentration distribution,the grain size,the volu-metric weight of the sediment and so on,which make the mechanical principle even more complex. So the results of the research can supply the scientific basis for the explanations of 'slurrying river',the turbulence intensity of the flow carrying sediment and the variance of the turbulence structure. | XU HaiJue BAI YuChuan | 2008 | Science China(Physics,Mechanics & Astronomy)2008，51，9： | 2 |
| 7 | Theoretical analyses on bed topography responses in large depth-to-width ratio river bends with constant curvatures显示文摘Bed morphology is the result of a dynamic response to a complex meandering river system. It is an important factor for the further development of river. Based on the meandering river characterized by a large depth-to-width ratio, a theoretical model is established with the coupling of Navier-Stokes(N-S), sediment transport, and bed deformation equations. The flow characteristics and bed response of river are obtained with the perturbation method. The research results show that, under the effect of twodimensional flow disturbance, the bars and pools present the regular response. For a given sinuousness, the amplitude of the bed response can be used as a criterion to judge the bedform stability. The effects of the Reynolds number, disturbance wavenumber,sinuousness, and bed morphology gradient on the bed response development are described. | Shuxian GAO Haijue XU Yuchuan BAI | 2018 | Applied Mathematics and Mechanics(English Edition)2018，39，5： | 1 |
| 8 | Energy dissipation caused by boundary resistance in a typical reach of the lower Yellow River and the implications for riverbed stability显示文摘The energy dissipation of boundary resistance is presented in this paper based on the flow resistance.Additionally,the river morphology responses to the resistance energy dissipation are explored using the Gaocun-Taochengpu reach in the lower Yellow River as a prototype.Theoretical analysis,measured data analysis and a one-dimensional hydrodynamic model are synthetically used to calculate the energy dissipation rate and riverbed morphological change.The results show that the energy dissipation rate along the channel will increase in both the mean value and the fluctuation intensity with increasing discharge.However,the energy dissipation rate will first decrease and then increase as the flow section or width-depth ratio increases.In addition,the energy dissipation rate has a significant positive correlation with the riverbed stability index.The results imply that the water and sediment transport efficiency of the river channel can be improved by optimizing the cross-sectional configuration to fulfil the minimum energy dissipation rate of the boundary resistance under stable riverbed conditions. | XU Haijue LI Yan HUANG Zhe BAI Yuchuan ZHANG Jinliang | 2022 | Journal of Geographical Sciences2022，32，11： | 0 |
| 9 | Coastline changes and tidal current responses due to the large-scale reclamations in the Bohai Bay显示文摘China’s Bohai Bay has experienced large-scale land reclamation since 2000.These reclamation projects create a nearshore ecological imbalance and shift sediment transport by changing the tidal current.However,these tidal current changes are not comprehensively understood.In this paper,the coastline changes in Bohai Bay due to reclamation are investigated and the responses of the tidal current are calculated through numerical methods.The results show that the coastline length of the bay increases by more than 500 km from 2000 to 2015 with the largest reclamation rate of 150.9 km^(2)/a.Consequently,the current velocity changes with an uneven distribution near the reclamation due to construction masking and dike protrusion.The tidal symmetry also changes in most nearshore areas,with opposite variations in the current velocity at peak flood and ebb tide.In addition,the tide direction deflects to bypass the reclamation and is usually consistent with the coastline.Harmonic analysis of the dominant M2 tidal constituent shows that the range of the reciprocating current is widely extended.The total influence of the reclamation can reach the-8-m isobaths in Bohai Bay.Changes in the tidal current are the main causes of water environment deterioration.Therefore,the arrangement and structural optimization of reclamation projects should be considered in the future. | Zhe HUANG Haijue XU Yuchuan BAI Fengshuo SHI Zhichao WEN | 2023 | Journal of Oceanology and Limnology2023，41，6： | 0 |
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