Applied Mechanics and Materials Vols. 212-213

Abstract: Keywords: river flow; two-dimensional CFD model; velocity profile; submerged vegetation leave Abstract. River flow with submerged foliage vegetation in straight and rectangular cross-sectional channel is numerically simulated through a vertical two-dimensional CFD model. Tilt thin strips are assigned in river flow to mimic the configuration of vegetation leave. The free surface line and the vertical profiles of longitudinal velocity are presented. The vertical velocity profile differs from the well acknowledged logarithmic or semi-logarithmic law. The submerged leave canopy resist the flow through it and pilots the flow upward over it, resulting in a decreased velocity within the canopy and an increased velocity above the canopy. The velocity profiles within the leave canopy are impacted by the configurations of the leave.

Abstract: The 2D laboratory experiments were performed to investigate tsunami wave runup on the combined sand beach. The N-wave was generated in three different water depths. The water surface elevations, maximum elevation of runup and snapshots of wave uprush and back wash were measured. The theoretical analysis of runup was presented. The results showed that uprush water wave had a decelerate process. The maximum elevation of runup R depends on incident wave height H and R is linear relationship with H plus water depth h.

Abstract: The Four Major Rivers Restoration Project (4MRRP), one of the largest river rehabilitation projects in Korea, has being carried out during the last three years. 0.57 billion m3 of sediment was dredged to widen and deepen the channel along four major rivers, the Han, Nakdong, Geum, and Youngsan rivers. As a result of reshaping the natural channel to a trapezoidal channel, and the construction of 16 weirs, the change of longitudinal slope of the river was inevitable. The distribution of bed materials was also changed, due to dredging. Therefore, the rivers were totally disturbed, and the stability of the rivers could not be assured. In particular, the Nakdong river, the second largest river in Korea, has the characteristics of an alluvial channel. Degradation of the main channel bed caused bank erosion, and head-cut phenomena in many tributaries. Deformations of the main channels could be observed all along the river. Long-term simulation of the channel evolution and prediction of the stability of the Nakdong river have to be examined, to cope with the instability of the river, which could lead to unexpected river disasters. This study deals with the methodology of uncertainty improvement, in analysis of the simulation and confirmation with field survey data. Methodology of uncertainty improvement in description of weir, whose discharge coefficient is unknown, in a river was suggested.

Abstract: During the construction of hydraulic engineering, it usually needs high-resolution and integrated investigation of underwater topography and geomorphology, and shape and position of underwater construction or obstacle. Based on the multibeam interferometric echo sounder, this paper analyzes high-resolution bathymetric topography method of multibeam interferometric principle, and applies the time of arrival (TOA) and direction of arrival (DOA) estimated by interferometric technology to achieve bottom backscatter geomorphology imaging. This method obtains high-resolution bottom backscatter imagery, and its space position realizes the one-to-one with bathymetric data, which makes bathymetric and backscatter imaging data merged accurately in integrated detection of topography and geomorphology. Moreover, the processing results of experiment data from Qingjiang River, in Hubei province of China, show the validity of the method.

Abstract: The multi-object application of the Xiaolangdi Reservoir and water and sediment regulation have greatly changed flow and sediment conditions emptying into the Yellow River Estuary. By use of flow and sediment field data at the Lijin Hydrological Station and river cross-section elevation data during 2001~2010, the paper has analyzed characteristics of the Yellow River Estuary in terms of incoming flow and sediment conditions, main flume area, average river longitudinal section and river length. The results show that annual total water volume emptying into the Estuary since 2003 has maintained about 200×10⁸ m³, annual total sediment 1.77×10⁸ t, whole annual average sediment concentration 9.3kg/m³, which are stable and beneficial for dynamic equilibrium of sediment transport. Interannual stability of main flume area, average river bed elevation and river length since the Lijin Section during 2007-2010 indicate that current Qingshuigou Course of the Yellow River has achieved dynamic equilibrium of sediment transport.

Abstract: This paper aims at analyzing the status of water resources in central and northern part of Ningxia, and tries to design a series of water-saving measures based on the principle of water conservation, combined with local situation and the content of land consolidation construction project. This study also includes an analysis on the water-saving potential after carrying out those measures. The results of the study show that the channels assemble care and field transformation can reduce the water loss of 259,810,700 m3, and the potential amount of water saved after the implementation of engineering measures is 157,199,500 m3.

Abstract: Major ion concentrations of twenty groundwater samples from two deep seated aquifers (coal bearing-GC and limestone-LC) are analyzed for identify the differences between them and the source of ions. The results suggest that they are moderate to highly mineralized water with their average TDS values are 2444 (GC) and 1178 (LC) mg/L. LCs show lower Na but much higher Ca and Mg concentrations relative to GCs. Saturation indexes and principle component analysis, as well as mole ratios between Na and Cl, Ca and SO4, Ca and HCO3 indicate that they have multi sources with incorporation of halite and albite for Na, calcite, dolomite and gypsum for Ca, pyrite and gypsum for SO4.

Abstract: Abstract. In this study, the effect of sediment concentration on submerged hydraulic jump (SHJ) characteristics such as jump length, submerged depth on the gate and the energy dissipation is investigated. Experiments were carried out in a flume of 46 cm depth, 12 m length. The width of the flume changes from 10 cm (at the entrance) to 60 cm (at the exit). Sediment load and flow concentration have an influence on submerged hydraulic jump characteristics including submerged depth on the gate, jump length and relative energy dissipation. It is shown that at high Froude numbers increasing the suspended sediment concentration to 28.7 gr/l leads to a reduction in the submerged depth on the gate up to 6% and jump length up to 10%. Also, the energy dissipation of the submerged hydraulic jump increases by 4% and turbulence resulting from the jump leads to upright distribution of concentration at the end of the jump. Also in concentrations higher than 30 gr/l, flow is not able to carry the whole sediments and subsequently leads to their deposition in subcritical area and behind the sluice gate.

Abstract: In this paper, a 2-D tidal river flow-sediment mathematical model is established by irregular triangular element calculation mesh and finite element numerical method. And verification is done through the comparison of measured value and the calculated. The result shows good agreement is obtained.

Abstract: A conceptual laboratory model for studying unsaturated flow in a single fracture-matrix system is developed in this paper. The model is capable of simulating the fracture and matrix with different samples, and three groups of contrastive experiments are conducted under a constant rainfall. The results show that fracture-matrix interactions have a great effect on the hydraulic properties of the fracture and matrix. The more distinctive the sample used to simulate the fracture and matrix is, the greater the influence is. Furthermore, the wetting front along the matrix runs ahead of that along the fracture, resulting in an extra water source for the fracture. It could be concluded fracture-matrix interactions and unsaturated hydraulic conductivity of the matrix cannot be ignored when the fracture is surrounded by a permeable matrix.