Applied Mechanics and Materials Vols. 212-213

Abstract: Through hydraulic model test of Tianqiao hydropower station reinforcement project, the empirical equations of the surface flow pattern critical water depth were proposed and validated. Some factors affecting the change of the surface flow pattern critical water depth were analyzed. The results show that the critical water depth values will decrease gradually when the nose angle change from zero degree to fifteen degrees. Lengthening the protection-apron and flow expansion will result in the ascent of the critical water depth values, which will descend if the bed level is reduced or the nose height is increased.

Abstract: The diversion power system intake excavation of Jinchuan Hydropower Station forms a slope of about 160m height; its stability is one of the main geological problems of the project. By detailed site investigation, the engineering geological characteristics of intake slope (including the lithology, slope structure, the structural surface and its combinations, rock weathering and unloading, hydrology etc) is analyzed in this paper. On the basis of site slope ratio statistics, the problem of how to select a safe and economic excavation slope ratio has been studied. The finite element method and rigid limit equilibrium method were used to calculate and analyze slope stability under various working conditions. The results of analysis evaluation provide a scientific basis for the design and construction.

Abstract: Base on the peak-load adjustment of the upper station and the consideration of downstream flow for shipping requirement, a minimum range of stage model, which is suitable for the day-controlled hydropower station, has been proposed in this paper. Taking certain hydropower station as an example, the minimum range of stage model has been studied in this paper with the dynamic programming method. And the results show that, although there would be a little losing of electric generated energy, the range of stage will be minimum fluctuation and the electric output process smooth through all the time, which means that the minimum range of stage model is suitable for the requirements of day-controlled hydropower station.

Abstract: The boundary layer flow determines the bottom shear stresses, which is key point for sediment transport and thereby the evolution of coastal morphology. The structure of the bottom boundary layer in coastal seas has been of interest to oceanographers for many years. In the paper Acoustic Doppler velocimeter (ADV) technique is applied to measure the bottom boundary layer under cnoidal waves in a laboratory flume with 40-m-long, 0.5-m-wide, and 0.8-m-deep.. Based on the high frequency turbulence signal collected, statistic parameters of cnoidal wave flow are calculated, compared and analyzed. The turbulent structure over plain bed and sand ripples bed are carefully studied. The turbulence intensity of near-bed velocities changes along depth of several phases in a period is analyzed. Turbulent Kinetic Energy Method (TKE Method) is used to estimate near-bed shear stress on flat and slope.

Abstract: As a kind of common port layout forms, excavated harbor basin was widely applied with its many advantages. But the sediment transport processes and water motion in such harbor are complex and of obvious three-dimensional characteristics affected by a lot of factors. To investigate the 3D hydrodynamic characteristics in an excavated harbor basin, experimental research based on PIV technology and numerical study through a 3D code with DES turbulence model has been developed respectively. The 3D hydrodynamic and sediment deposition characteristics in the harbor have been indicated successfully in this paper.

Abstract: The numerical calculation and simulation of gas-liquid two-phase flows with interfacial deformations have nowadays become more and more popular issues in various scientific and industrial fields. In this study, a three-dimensional gas-liquid two-phase flow numerical model is presented for investigating interfacial flows. The finite volume method was used to discretize the governing equations. A High-resolution scheme of VOF method (STACS) is applied to capture the free surface. The paper outlines the methodology of STACS and its validation against three typical test cases used to verify its accuracy. The results show the STACS-VOF gives very satisfactory results for three-dimensional two-phase interfacial flows problem, and this scheme performs more accurate and less diffusive preserving interface sharpness and boundedness.

Abstract: The flow around two vertical cylindrical piles exposed to a steady current is studied numerically by a three-dimensional hydrodynamic model, which is closured with a k-ε turbulence model. This model is firstly validated by experimental data obtained from a labortory experiment for a steady flow through a circular pile. Then this validated model is used to study flow pattern around two cylindrical piles. Finally, four key physical factors of the size of the horseshoe vortex and lee wake vortex, the maximum current velocity and bottom shear stress are analyzed under the different pile spaces. The main conclusions are: i) the size of the horseshoe vortex increases with the increase of the two pile space, while the size of the lee wake vortex changes slightly; ii) the maximum current velocity and the maximum bottom shear stress decrease with the increase of two pile space, and reach steady after the two pile space larger than six times of cylindrical pile diameter.

Abstract: Wave-induced setup increases the mean water level in the surf zone and can be influenced by bottom stress in the presence of ambient current. As the numerical experiment shows, the effects of bottom stress on wave setup are associated with wave conditions. An onshore-directed bottom stress caused by offshore ambient current increase the wave setup and an offshore-directed bottom stress caused by onshore ambient current decrease the wave setup. According to the experiment, it is necessary to calculate wave-induced setup including the bottom stress in the presence of ambient current.

Abstract: This paper presents a numerical procedure to investigate the hydrodynamic performance and flow field of propeller with the aid of dynamic mesh. The purpose of the study is to validate a hybrid mesh generation strategy and dynamic mesh technology. Computations were performed at various advance ratios following experimental conditions. Results for both global and local flow quantities are discussed and compared with experimental data. The predicted thrust and torque are in good agreement with the experimental values. The overall results suggest that the present approach is practicable for actual propeller design procedure.

Abstract: Fishways are hydraulic structures allowing fishes upstream migration through engineering constructions in the rivers. The Denil type has a wide application and the main components are flat baffles. In this paper, we present a new type of baffle (arc-shaped baffle) to ameliorate the hydrodynamic characteristics in the fishway. The main improvement of arc-shaped baffle fishway is the alteration that the flat baffles are replaced by arc-baffles. In order to investigate the influence of water flow on migratory fish in the arc-baffle fishway, model tests were conducted. Based on the experimental results, the conclusion can be reached that hydrodynamic characteristics in arc-shaped baffle fishways are steadier than that in traditional Denil fishways, which makes fishes ascend easily.