On stability of MHD flows located on the surface of axisymmetric torus

The erosion process of a cohesive sediment after consolidation was studied experimentally in a closed conduit system.The test samples investigated in this study are mixtures of sand and clay with variable compositions and different consolidation times.The main concern of this study is the effects of the dry density of the consolidated sediment on scour rate.A scour rate formula is derived and further interpreted based on the experimental results.     

PREDICTION OF MAXIMUM SCOUR DEPTH AROUND LARGE-DIAMETER CYLINDER UNDER THE EFFECTS OF BOTH WAVE AND CURRENT

1.　INTRODUCTIONDue to the effects of both wave and current a round the isolated offshore large dimensional struc ture(D/L ≥ 0.20), the serious partial scour willresult in the destruction of its foundation. As apractical engineering problem, local scour aroundthe large sized structure has already drawn muchattention, but most of the researches concentrateto scour problem only with wave or only with cur rent[1 3]. There have been very few researches onthe partial…     

EFFECTS OF SUBMERGED MACROPHYTES ON SEDIMENT SUSPENSION AND NH4-N RELEASE UNDER HYDRODYNAMIC CONDITIONS

Aquatic vegetation affects sediment suspension and nutrient release by changing the flow structure. Experiments on the influence of submerged vegetation on flow structure, sediment suspension, and NH₄-N release were carried in a flume with natural submerged vegetation. Turbulence characteristics in the vegetation section were measured using a three-dimensional acoustic Doppler velocimeter. The effects of submerged vegetation on bed shear stress (τ_b), sediment suspension, and NH₄-N release were analyzed. Results show that with vegetation, bed shear stress is reduced by about 20% – 80%, which, in turn, reduces sediment suspension. The impact of submerged vegetation on sediment suspension and NH₄-N release should be considered along with flow intensity. When the flow Reynolds number is relatively small, the submerged vegetation is quite capable of inhibiting sediment suspension and reducing NH₄-N release, but when the Reynolds number reaches a certain value, the presence of aquatic plants exacerbates sediment suspension and promotes NH₄-N release. Results also reveal that a highly significant positive correlation exists between NH₄-N concentration and water turbidity in both vegetated and non-vegetated channels.     

EFFECT OF SUSPENDED SEDIMENT ON THE TRANSPORT AND TRANSFORMATION OF 4-NITROCHLOROBENZENE IN THE YELLOW RIVER

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PROMOTING SILTATION EFFECTS AND IMPACTS OF HENGSHA EAST SHOAL ON THE YANGTZE RIVER ESTUARY

For the Hengsha East Shoal Promoting Siltation Project in the Yangtze River Estuary,this work developed a formula for calculating sediment carrying capacity based on variable coefficients and a mathematical model for suspended sedimentation using variable saturation recovery coefficients.Not only does the model yield good verification,preferably give the hydrodynamics and the sediment concentration,but also reach a good agreement between the simulation results and the measured topographical changes in the promoting siltation zone of the Hengsha East Shoal.Moreover,this article proposes a method for examing the net sediment transportation flux by tide for studying the effects of the project of promoting siltation and comparatively analyzes the current siltation of the Hengsha East Shoal and siltation mouth layouts,entrance widths,entrance bottom elevations,and the impact of the South Main Dike on promoting siltation through calculating the net sediment transportation flux by tide over the fixed bed and the direct movable bed numerical simulations.The results are in good agreement with each other,indicating that the method for calculating the net sediment transportation flux by the tide is also useful for assessing the project in promoting siltation.Finally,we use the modeling results to analyze the water and sediment diversion ratios and the changes in silting and scouring in riverbeds and draw the conclusion that the completion of the Hengsha East Shoal Promoting Siltation Project would not adversely affect the Yangtze River Estuary Deepwater Channel Project.     

水稻薄露灌溉技术示范推广

水稻薄露灌溉技术改变了传统的长期淹灌习惯，有效地改善了水稻的生态条件，其突出优点是广法简单易行，农民易于掌握，农户只花很少的钱，可获得增产节水的显著效益。     

ASSESSMENT OF CONSEQUENCES OF SEDIMENT DEFICIT ON A GRAVEL RIVER BED DOWNSTREAM OF DAMS IN RESTORATION PERSPECTIVES: APPLICATION OF A MULTICRITERIA,HIERARCHICAL AND SPATIALLY EXPLICIT DIAGNOSIS

As regards river restoration, it is fundamental to better link human pressures and environmental responses and to take into consideration not only target species or habitat but diverse ecological elements. This permits to assess sustainable restoration plan, especially concerning sediment augmentation below dams. The use of a hierarchical multicriteria approach on the Ain River permits us to assess a diagnosis of sediment deficit impact integrating several morphological (channel shifting, river bed degradation and river bed coarsening) and ecological components (Riparian and floodplain lake and fish communities). Our diagnosis also integrates a temporal and spatial approach better to link human pressures and environmental responses and to identify the dam effects amongst other drivers (e.g. grazing decline and channel regulation). The results confirm causality links between sediment deficit and slight channel bed degradation (0.01 m.year^?1) or channel bed paving and thus highlight the impact of the dam on the drying of the riparian forest and on former channel community. However, the relationship between incision and reduction in active channel lateral mobility is more difficult to establish. The role of sediment deficit in the current variability of the riparian regeneration capacity and, thereby, landscape diversity along the lower valley remains unclear. This study also confirms the relevance of using different ecological indicators, notably because all components present different adjustment time scales, whereas some of them are more sensitive to other impacts. Copyright © 2013 John Wiley & Sons, Ltd.     

SIMULATION OF TANK SLOSHING BASED ON OPENFOAM AND COUPLING WITH SHIP MOTIONS IN TIME DOMAIN

Tank sloshing in ship cargo is excited by ship motions, which induces impact load on tank wall and then affects the ship motion. Wave forces acting on ship hull and the retardation function are solved by using three-dimensional frequency domain theory and an impulse response function method based on the potential flow theory, and global ship motion is examined coupling with nonlinear tank sloshing which is simulated by viscous flow theory. Based on the open source Computational Fluid Dynamics (CFD) development platform Open Field Operation and Manipulation (OpenFOAM), numerical calculation of ship motion coupled with tank sloshing is achieved and the corresponding numerical simulation and validation are carried out. With this method, the interactions of wave, ship body and tank sloshing are completely taken into consideration. This method has quite high efficiency for it takes advantage of potential flow theory for outer flow field and viscous flow theory for inside tank sloshing respectively. The numerical and experimental results of the ship motion agree well with each other.     

水稻薄露灌溉技术在我省大面积推广应用

水稻薄露灌溉技术充分发挥了水的综合功能，将土、肥、光、热和田间小气候有机地结合起来，克服了过去水稻长期淹灌的种种弊端１９９７年全省水稻薄露灌溉技术推广面积约３５１３万ｈｍ２（５２７万亩），共增产稻谷２．１８×１０８ｋｇ，累计全年农户增收约３亿元，取得了显著的经济效益和社会效益