Applied Mechanics and Materials Vols. 256-259

Abstract: Based on the strong interaction method that combines FEM with acoustic theory, the finite element dynamic equations of spiral casing structure are built, which provides the basis for analyzing self-olsillatin characteristics of spiral casing structure. The self-olsillatin characteristics of structure are calculated with the method. The natural vibration frequencies, and mode shapes are obtained.

Abstract: We designed and constructed a model of Ecuador's Coca Codo Sinclair Hydropower Station, observed its intake discharge, flow pattern, flow velocity distribution and desilting effect and the desilting effect of the desilting facilities. Through model experiment and comparison among a variety of body types based on the experiment result of the original design scheme, we recommended a modified body type that is favourable for the settling basin to desilt.

Abstract: For a flow chute with complex boundary conditions, such as with an anti-arc section, the flow behaviors and characteristics of aeration after the aerator are more complex than that in the straight chute. Based on the k~ε turbulence flow model together with VOF method, flow velocity fields over the aerator on the chute with anti-arc section were numerical simulated. Model experiments were investigated to verify the simulation results. Comparison shows that the calculation results agree well with the observed experimental data. Some factors including radius of the anti arc, aerator’s height and takeoff angel which influence aerated flow are discussed.

Abstract: To ensure the secure buried depth of the subway tunnel which was routed underneath the Fenghuahe River, a two-dimensional tidal current and sediment transportation model was established to simulate the maximum scour depth of the riverbed. The conclusions were shown as follows: the most disadvantageous hydrologic condition was a combination of the 200-year return period flood in the Fenghuahe River and the 5-year highest tide in the Yonghe River. The maximum scour depth of the riverbed above the subway tunnel was 1.19 m and the lowest elevation of the riverbed cross-section was -8.56m. The results could provide technical support for the safety of subway design.

Abstract: In order to guarantee the security of flood discharge and energy dissipation of reservoir spillway, in this paper, visual simulation of flood discharge is studied combining closely with a reservoir extension project. Based on the data sources collected by traditional data acquisition methods and modern information capture means, key techniques such as modeling of spillway, dynamic simulation of the flow and texture mapping and other corresponding methods are put forward. Then visual simulation of flood discharge for reservoir spillway is realized. This study provides an analysis platform, which is safe, economic, intuitive, easy to operate and repeatable, for simulation of spillway flood discharge in reservoir projects. It also provides a scientific and effective theoretical foundation and technical support for the engineering design, management and decision-making.

Abstract: Evapotranspiration (ET) is an important component of the water cycle at field, regional and global scales. This study used measured data from a 40-year (1970–2009) in the East China plain on Rape and Rice to analyze the impacts of climatic factors on actual crop water use and crop yield. The results showed that grass reference evapotranspiration (ET0, calculated by FAO Penmen Monteith method) was relatively constant from 1970 to 2009. Average seasonal crop water use was 250 mm and 154 mm for Rice and Rape, respectively, over the four decades. The seasonal decrease in crop water use was around 1.4 mm per season for Rice, and 0.08 mm per season for Rape. Average seasonal effective rain was 456 mm and 120 mm for Rice and Rape, respectively, over the four decades. The seasonal increase in effective rain was around 0.7 mm per season for Rice, and 0.03 mm per season for Rape. The result showed that over the four decades actual crop water use decrease much greater than the increase in effective rainfall. The results also showed that with new cultivars and improved management practices it was possible to further increase grain production without much increase in water use.

Abstract: Due to no design guidelines available for the hubless propeller，based on the relative inflow velocities together with blade root strength considerations, the Ka –series propeller’s blade geometry was re-designed with an inversion of the thickness distribution of the sections. Accordingly，the blade geometry model for hubless rim-driven propulsors was designed，then three types of hubless rim-driven propulsors’ models were established and calculated numerically. The results show that thrust coefficients and torque coefficients for hubless rim-driven propulsors are similar to the ducted Propeller’s. Due to no hub, with the new thruster the hub-vortex is avoided and the cavitation minimized.

Abstract: The unsteady flow RNG k ~ ε turbulence model and VOF Method are employed to numerically simulate 3-D flow field of diversion tunnel outlet stilling pool in Xinjiang dina river wuyi reservoir. The computational and experimental water surface elevation, pressure on the bottom and cross-sectional mean velocity of the suspended grid stilling pool are compared in well agreement. Suspended grid is used in stilling pool, the number of vortex and range are increased in the pool, and the size of the vortex is decreased along with the flow increase. The suspended grid position is determined at end of the vortex. In the suspended grid stilling pool water stability, flow regime is good.

Abstract: For the construction of water conservancy project in the upstream of the Yangtze River and the human activities, the runoff and sediment discharge from the upstream to East China Sea have changed greatly. To explore the distribution characteristics of suspended sediment in Yangtze Estuary under the new upstream boundary condition, a 2-D flow-sediment numerical model including the Yangtze Estuary and the Hangzhou Bay was established. Four different runoffs, which are 4,620m³/s, 11,000m³/s, 75,900m³/s and 90,000m³/s respectively, and the correspond sediment discharges were considered. The result indicates that, with the increase of upstream runoff, the sediment intrusion from the top of the North Branch into the North Branch decreases and the suspended sediment concentration field in the South Branch changes is greater than that in the North Branch. In the same region, the sediment concentration decreases during rising tide while it increases at low tide. The change of the core position for suspended sediment field is insignificant.

Abstract: Groundwater reservoirs aim at saving grounding water from aquifers by means of interception and adjustment. This study adopts numerical model simulation to evaluate the benefit of developing subsurface reservoirs and provides the case of the groundwater reservoir development at Daping region in Dongju Island. Since 2008, this study has been conducting surface geological surveys, geological drilling, surface infiltration experiments, physical experiments on bore specimens, and continuous observation of groundwater level while simultaneously conducting water pumping and slug tests in the field in order to estimate the hydro geological parameters of the site. The development benefit assessment of the groundwater reservoir will also include catchment area, surface land use, calendar year rainfall records and other information. Meanwhile, the FEMWATER numerical model of groundwater will be used to conduct hydrodynamic simulations of the development area. According to the simulation results of pre and post construction of the cut-off wall of the groundwater reservoir, this study could estimate the stable pre and post water volume and the development benefit of the groundwater reservoir can be assessed. According the 3-year unsteady numerical simulation, the results show that the groundwater reservoir can provide approximately 36 m3/day of stable water supply during dry seasons. If a cut-off wall is implemented and the stable water supply could increase 11% to 40 m3/day and raise the average upstream groundwater level of the cut-off wall by 1m, it clearly displays the benefit of the cut-off wall.