基于DEM的黄土丘壑区动力学流域水沙数学模型应用研究—以黄河中游两个典型小流域为例

该文以黄土丘陵沟壑区典型小流域-岔巴沟流域为研究对象，首先采用地理信息系统（GIS）对坡度和土地利用方式等侵蚀产沙环境因子提取分析，提出基于网格的超渗产流模型和基于运动波理论的栅格型坡面汇流模型，然后采用Preissmann四点隐式差分进行方程的离散求解。另外根据研究区地形及地貌特点将其分为梁峁坡、沟谷坡和沟槽三种垂直分带侵蚀单元，采用力学分析建立其侵蚀产沙公式和分布式坡面流运动波模型进行耦合求解。本模型在岔巴沟流域1970～2001年17场水沙过程的模拟和验证结果表明：产汇流、产沙计算平均确定性系数分别为0．69、0．58。杏子河流域验证结果也表明该模型对黄丘区水土流失时空过程的模拟计算具有一定精度，模型预测成果可为黄土高原水保规划和生态建设等提供更为精细和科学的决策依据。

空腔回流区水沙特性的计算分析

建立了回流区水深平均平面二维水流泥沙数学模型，提出了平衡输沙模式下回流区泥沙淤积计算方法；采用长江科学院空腔回流泥沙淤积水槽试验数据，验证了回流区泥沙淤积计算方法的可行性和精度；通过数模计算分析，一方面加深了空腔回流区环流结构及含沙量分布的机理认识，另一方面研究了模型变率对回流区水沙特性的影响。

Numerical Analysis of Emergency River Restoration Scheme for Qingping Mega Debris Flow

The mega debris flow occurred on August 13 th 2010 in Qingping town,China(hereafter called '8.13' Debris Flow) have done great damage to the local habitants as well as to the re-construction projects in the quake-hit areas,and the channel-fill deposit problem caused by the debris flow was the most destructive.Moreover,it is of high possibility that an even severe deposit problem would reappear and result in worse consequences.In order to maximize risk reduction of this problem,relevant departments of the government established a series of emergency river restoration schemes,for which the numerical analysis is an important procedure to evaluate and determine the optimized one.This study presents a numerical analysis by applying a twodimensional debris flow model combined with a relevant water-sediment model to simulate the deposit during the progress of the debris flow,and to calculate and analyze the river flow field under both the present condition and different restoration conditions.The results show that the debris flow model,which takes the confluence of the Wenjia Gully to the main river into account,could simulate the deposit process quite well.In the reproduced debris flow from the simulation of the '8.13' Debris Flow,the original river flow path has switched to a relatively lower place just along the right bank with a high speed of near 7m.s-1 after being blocked by the deposit,which is highly hazardous.To prevent this hazard,a recommended scheme is derived through inter-comparison of different restoration conditions.It shows that the recommended scheme is able to reduce the water level and as well to regulate the flow path.Based on the given conditions of the mainstream and the tributary confluence for the simulated '8.13' Debris Flow,when encountering a debris flow with deposit volume less than 0.5 million m3,the river channel can endure a 20-year return flood;however,when the deposit volume increases to 2 million m3,the flood capacity of the river will be greatly impacted and the scheme becomes invalid.The recommended scheme supported by the present study has been applied to the emergency river restoration after this mega-debris flow.

Total Reflux Operation of Multivessel Batch Distillation for Separation of Binary Mixtures

Multivessel batch distillation(MVBD) is mainly used to separate mixtures with more than two components. In this article, a new operation mode with MVBD is proposed for separation of binary mixtures under total reflux. A mathematic model is setup for the simulation. The proposed operation policy and the regular operation with constant reflux are compared theoretically and experimentally. The results show that the new operation mode has great advantages in time saving and operation flexibility. MVBD presents great potential for separation with high efficiency.

Numerical simulation on the process of saltwater intrusion and its impact on the suspended sediment concentration in the Changjiang(Yangtze)estuary

To study the relationship between sediment transportation and saltwater intrusion in the Changjiang (Yangtze) estuary, a three-dimensional numerical model for temperature, salinity, velocity field, and suspended sediment concentration was established based on the ECOMSED model. Using this model, sediment transportation in the flood season of 2005 was simulated for the Changjiang estuary. A comparison between simulated results and observation data for the tidal level, flow velocity and direction, salinity and suspended sediment concentration indicated that they were consistent in overall. Based on model verification, the simulation of saltwater intrusion and its effect on sediment in the Changjiang estuary was analyzed in detail. The saltwater intrusion in the estuary including the formation, evolution, and disappearance of saltwater wedge and the induced vertical circulation were reproduced, and the crucial impact of the wedge on cohesive and non-cohesive suspended sediment distribution and transportation were successfully simulated. The result shows that near the salinity front, the simulated concentrations of both cohesive and non-cohesive suspended sediment at the surface layer had a strong relationship with the simulated velocity, especially when considering a 1-hour lag. However, in the bottom layer, there was no obvious correlation between them, because the saltwater wedge and its inducing vertical circulation may have resuspended loose sediment on the bed, thus forming a high-concentration area near the bottom even if the velocity near the bottom was very low during the transition phase from flood to ebb.

The Fractal Characteristics of Drainage Networks and Erosion Evolution Stages of Ten Kongduis in the Upper Reaches of the Yellow River, China

The fractal characteristics of drainage in the ten kongduis of the upper Yellow River were obtained using the box counting dimension, and the evolution stages of the watershed topography were defined by different ranges of the fractal dimensions of river networks（D_g）. The results show that the fractal scaleless range of the Maobula River is 20–370 m based on a combination of artificial judgment, correlation coefficient test and fitting error. Other kongduis show good fractal characteristics in this fractal scaleless range as well. The box counting dimension can be used as a quantitative index of watershed topography fractal characteristics. The fractal dimension of stream networks is independent of the threshold contributing area used for extracting the drainage networks from the DEM. The values of D_g in the upper ten kongduis are in the range of 1.08-1.14. Both the runoff yield and the sediment yield are positively and linearly related with D_g. The positive relation between the sediment yield and D_g reflects the effect of landform features on sediment yield in the young and/or mature stages of landform evolution of the study area. By revising the critical value of D_g, the value of D_g of the basin in the young evolution stage is less than 1.06, while it is more than 1.06 for the basin in mature or old evolution stage. The upper ten kongduis are in the mature stage of landform evolution.