Applied Mechanics and Materials Vols. 405-408

Abstract: Guanzhong Segment of Wei River was studied in this article. Based on water quality observational data (ammonia-nitrogen) and hydrology observational data (flow of the sections) of Guanzhong Segment of Wei River in the rainy, normal and wet season in 2006, improved one-dimensional steady-state river water quality model was calibrated. River water quality was predicted in the normal season which were compared with the observational data in 2005. The results show that the water quality computed by improved one-dimensional steady-state river water quality model is grossly consistent with the observational water quality data and the model may provide the technical supports for the response relationships of water quality and water quantity of Guanzhong Segment of Wei River.

Abstract: Riverbed structures were developed in many very coarse gravel-bed rivers as a result of fluvial morphology. And the distribution of them was obviously relevant with environment conditions. This paper carried out field investigations in natural rivers, to study the riverbed structures size, distribution in the basin, as well as their connections with local environmental conditions. The results indicated that: The structures can enhance resistance to water erosion and protect riverbed. Given the conditions of little bedload, the structure intensity is in direct ratio to the unit-width stream power which consumed by the structures when rivers are in dynamic equilibrium. If the structures are not able to dissipate the whole power, the river status turns to disequilibrium and the riverbed will be eroded by excess energy. The fluvial morphology of coarse-grained riverbed is controlled by this process.

Abstract: Experimental study on river channels formation and change process with two different constant flows 2.45L/s and 4.9L/s that which come from mountains and into delta depositions surface, based on sediment supply 15.72kg/h at the water inlet. After 964h experiment, research on the study shows as follows: with 2.45L/s flow, on the surface of delta depositions forming process the channel appears as straight, braided, micro-bend and meandering form. The first formation processes of delta deposition are straight and braided river which appeared alternately every 50h on the surface. When time goes on the delta get longer and braided streams branch of the shunt decrease gradually, that made the channel appeared with slightly curved form. Combined with that flexural radius gets bigger because of the outer bank erosion of slightly curved channel backed off, finally the meandering channels presented. With 4.9L/s flow, the formation processes gave priority of braided river, which appeared every 15h cycle, following the aggravate of eroding in floodplain and scouring in main channel, the river pool board-shallow comes with the main-flow swing, the channel existed as slightly curved form, and appears two sides of deposition. Finally analysis and research the channel cross-section morphological and longitudinal slope. In conclusion, the delta depositions surface channel existed as micro-bend of no branch with single strands, under the constantly water and sediment conditions.

Abstract: An experiment was conducted to determine the effect of mulched drip irrigation under water deficit on soil water content (SWC), stored soil water (SSW), daily water consumption (DWC) and ratio of water consumption in total water use (RWC) of potato in an arid area. Five water deficit treatments designed to subject potato to various levels of soil water deficit at different crop growth stages and a full irrigation control were established. The result indicated that the maximum SWC was at 20 cm depth in soil profile and that in 10 to 40 cm increment varied sharply during potato growing season. The SWC, SSW, DWC and RWC were significantly affected by mulched drip irrigation at water deficit regulation stages except at starch accumulation. Therefore, proper levels of soil water deficit regulated with mulched drip irrigation at proper plant growth stages could be used to regulate soil water status, stored soil water and crop water consumption effectively.

Abstract: The turbulent coherent structure of flow in open channel bends is a stochastic process in nature. The coherence structure of the flow or bursting process is very important for the entrainment of sediment particles from the bed. In this study, first-order Markov process combined with three-dimensional quadrant analysis is applied to the measured turbulent data in open channel bends. The turbulent data was measured in an experimental flume using three-dimensional acoustic Doppler velocity meter (ADV). It was found that the stable movements of velocity fluctuations have higher transition probabilities than other movements, and the cross movements have the least transition probability. In addition, the internal group of events occurs more frequently than external group, particularly the internal ejection and internal sweep events and the probabilities decrease from the concave bank to the convex bank periodically, and reach the maximum at the top of the curved concave bank.

Abstract: Based on the definition of the irrigation coefficient, we discussed the main factors which affect the irrigation coefficient as well as the measures to improve the irrigation coefficient in agriculture. According to the variation and the different features of the irrigation coefficient in different regions and conditions, this article not only explores the basic way to improve the irrigation coefficient, but also gives measures including water apportion measures, management and engineering measures. The potential ability of improving the irrigation coefficient is analyzed preliminarily in the real situation of Chinese irrigation methods and techniques.

Abstract: Diffusion theory is the leading one which is used to study the vertical distribution of sediment concentration. And diffusion coefficient is a key parameter to determine the vertical distribution of suspended sediment. First of all, the calculation methods are introduced based on the momentum transfer theory and fluctuating velocity. According to the sediment equation of exchange equilibrium in vertical, the new expression is obtained for sediment diffusion coefficient and the vertical distribution of sediment concentration. By the flume experimental data and field data in natural river, the difference is analyzed among the different expressions.

Abstract: The velocity distribution and bed deformation patterns in a meandering channel with consecutive bends were investigated by using both an experimental study and a 3-D flow and sediment transport model. The simulated results from the 3-D model agree well with the experimental data. The flow structure and bed deformation patterns in channel bends with different flow conditions were analyzed. Modeled results demonstrated that the velocity distribution and bed deformation in the meandering channel depend mostly on the flow regimes. For the case of small flow discharge, the maximum velocity occurs in the vicinity of concave bank. For the case of large discharge, the maximum velocity occurs near the center part of the channel. Consequently, bed deformation patterns in meandering channels will be influenced by the flow conditions.

Abstract: Under the high temperature of fire, the temperature change of the reinforced concrete beam is very important to the structure study. This paper, with heat transfer theory as its theoretical basis, explores the analytical method, the common method for analysis, calculation method of numerical value and finite element analysis by analyzing the temperature field of the concrete component cross sections under high temperature. With the help of MATLAB, it calculates and analyzes the temperature field of the reinforced concrete beam under the high temperature of fire, determines the temperature rise curve of the reinforced concrete beam in case of fire, and calculates the cross section temperature fields of the beam or pillar under the circumstances of different cross section sizes and different timings of fire on three sides.

Abstract: With fire temperature rising, elastic modulus of steel would be reduce, which then would lead to global instability phenomenon of double-layer square pyramid silo-shell structure. In order to analyze its fire resistance performance under high fire temperature, different geometric parameters were set based on the effect factors when it operated normally at room temperature. To analyze its displacement change by conducting nonlinear finite element analysis which was under the two typical temperature rising cases including global non-uniform temperature and localized high temperature. Then, with the temperature rising, the fire resistance performance and the maxium displacement changing rule were obtained.