Time filter

Source Type

Wuhan, China

Lu X.,Wuhan University | Dong B.,Hydrology Bureau | Mao B.,Yangtze River Scientific Research Institute | Zhang X.,Wuhan University
Comptes Rendus - Mecanique | Year: 2015

A robust and well-balanced numerical model is developed for solving the two-layer shallow water equations based on the approximate Riemann solver in the framework of finite-volume methods. The HLL (Harten, Lax, and van Leer) solver is employed to calculate the numerical fluxes. The numerical balance between the flux gradient and the source terms is achieved by using a balance-reformulation method. To obtain exactly the lake-at-rest solutions as the water depth is chosen as the conserved variable for the continuity equations, a modified HLL flux formulation is proposed for mass flux calculations. Several numerical tests used to validate the performance of the developed numerical model. The results show that the developed model is accurate, well balanced, and that it predicts no oscillations around large gradients. © 2015 Académie des sciences.

Lu X.,Wuhan University | Zhang X.,Wuhan University | Mao B.,Yangtze River Scientific Research Institute | Dong B.,Hydrology Bureau
Comptes Rendus - Mecanique | Year: 2016

In this study, a phase-resolved and depth-averaged non-hydrostatic numerical model (SNH model) is developed. The non-incremental pressure-correction method is employed to solve the equation system in two successive steps. Firstly, an approximate Riemann solver in the framework of finite volume methods is employed to solve the hydrostatic shallow-water equations (SWE) on a collocated grid to obtain provisional solutions. Then, the intermediate solutions is updated by considering the non-hydrostatic pressure effect; a semi-staggered grid is used in this step to avoid predicting checkboard pressure field. A series of benchmark tests are used to validate the numerical model, showing that the developed model is well-balanced and describes the wetting and drying processes accurately. By employing a shock-capturing numerical scheme, the wave-breaking phenomenon is reasonably simulated without using any ad-hoc techniques. Compared with the SWE model, the wave shape can be well-preserved and the numerical predictions are much improved by using the SNH model. © 2015 Académie des sciences.

Yang T.,Hohai University | Yang T.,The Institute of Hydraulic Engineering of Yellow River | Yang T.,Wuhan University | Xu C.-Y.,University of Oslo | And 6 more authors.
River Research and Applications | Year: 2010

The Range of Variability Approach (RVA) is employed to investigate the variability and spatial patterns of hydrological and sediment changes (1953-2000) induced by intensified human activities, i.e. the implementation of water and soil conservation measures, in nine major catchments of the Loess Plateau, China. Results indicate that: (1) streamflow and sediment load regimes were greatly changed by the implementation of conservation measures; (2) similar spatial patterns of high hydrological and sediment changes resulting from the intensive implementation of conservation measures are observed in most catchments of the middle Yellow River. However, slightly different behaviours of changes exist due to the unique complexity of hydrological and sediment processes in this region and (3) the impacts of various conservation measures on hydrological and sediment processes are closely associated with the extent and types of these measures. Engineering works have a quite immediate impact on streamflow and sediment regimes. Considerable vegetation controls are recognized as additional important driving forces for high hydrological and sediment alterations among various soil conservation measures. Invegetation controls, afforestation is the major factor causing the changes of runoff and sediment processes in these nine catchments. The results of the current study will be greatly beneficial to the regional water resources management and restoration of eco-environmental system in the middle Yellow River basin characterized by intensified soil-conservation measures under the changing environment. © 2009 John Wiley & Sons, Ltd.

Ge H.,Changjiang River Scientific Research Institute | Zhu L.L.,Hydrology Bureau | Huang R.Y.,Changjiang River Scientific Research Institute
Applied Mechanics and Materials | Year: 2014

The non-uniform sediment input has played a significant role in the bed evolution in the middle and lower Yangtze River, which indirectly influences the amount of the sediment transported into the East China Sea every year. However, it has been dramatically changed by the climate change, especially the human activities in the upper Yangtze River, not only the amount, but also the grading. The average annual sediment load has reached to 402.6 million tons since 1960s, while showing a decreasing and refining trend mostly influenced by the human activities, such as soil and water conservation, and large hydropower projects. The most direct consequence of these changes was to cause severe erosion in the middle and lower Yangtze River, further to bring about fluvial regime adjustment. In this article, a series of daily and annual averaged sediment transport data since 1960’ were collected and analyzed to find the impacts of the significant human activities on the non-sediment input of the middle Yangtze River, and then its variation tendency was predicted, affected by the existed large hydropower projects and to be build ones in the upper Yangtze river. The result shows that the non-uniform sediment input of the middle Yangtze River was slightly reduced by the operation of Gezhouba Project and the up and middle Yangtze River water and soil conservation prevention and control projects, and further less after the impoundment of Three Gorges Reservoir, meanwhile its grading has been getting finer and finer. In future, along with the normal operation of the Three Gorges Reservoir and the built of the cascade reservoirs in the upper main stream and tributaries of the Yangtze River, it will be continuously reduced and refined. © (2014) Trans Tech Publications, Switzerland.

Liu X.-Y.,Yellow River Conservancy Commission | Yang S.-T.,Beijing Normal University | Jin S.-Y.,Hydrology Bureau | Luo Y.,Beijing Normal University | And 2 more authors.
Shuili Xuebao/Journal of Hydraulic Engineering | Year: 2014

According to the satellite images, hydrological and meteorological data in the past six decades and the achievements in the runoff/sediment variation study, the concepts of sediment yielding coefficient and vegetation coverage ratio based on remote sensing images are introduced to set up a method, which can evaluate the effects of sediment reduction from forest and grass land over large area in the loess hilly area. The effect of sediment reduction is obvious in improving the coverage of vegetation when the coverage ratio is less than 35%-40%. The effect of sediment reduction tends to be stable and the weight of rainfall intensity is little when vegetation coverage is about 60%.

Discover hidden collaborations