论文摘要 英文范本

In the lotus root-shape channels, the flow takes on an obviously 3-D turbulent characteristics, as the river has changed suddenly and the shoreline has inflected. So, the turbulence intensity in the lotus root-shape channels is much greater, compared with the straight channels. As the flow characteristics, including flow resistance, stage-discharge relationship, waterline, transverse slope of water surface, flow velocity distribution and turbulence characteristics etc, is bound up with the environmental protection, the general navigation, the flood protection and the power systems, so it is one of the most fundamental problems in hydraulics and river dynamics. Many researches have been carried out on the flow characteristics about the straight channels or the meandering river channels. Yet the flow movement disciplines of the lotus root-shape channels have got little achievement.

Nowadays, turbulent models have been widely adopted in fluid computation, with the ε-k model being the most popular for its high efficiency and precision. However, the independent similar turbulent assumption makes it limited in the adoption of complex flow, which makes the distinct Reynolds stress model competitive.

Under the foundation of systematically conclusion of the research result of the lotus root-shape channels flow characteristics at home and abroad, this dissertation will source, arrange and analyze the present test material to take mock calculation of the continuous curve flow and compare with the measured value to testify the advantage and disadvantage of all the models using the three ε-k models and Reynolds stress model supplied by software Fluent. Through the contrast of 3D flow numerical simulation in the straight channels and the lotus root-shape channels, the paper reveals the methodology of turbulent fluctuation, energy loss and flow resistance influenced by the lotus root-shape channels. The main research content and result are as follows:

1） The paper makes detailed introduction about the variance and solving of curve flow model theory and equation, the calculation of Fluent software.

2） The paper in chapter three uses the three-dimensional standard ε-k model, RNG ε-k model, Realizable ε-k model and Reynolds stress model, disperses the turbulent flow with the finite volume method and brings in the VOF method to trace

free surface, PISO method to calculate the pressure and velocity pattern, to statistically simulate the consecutive-bend flow and get the pattern of water surface curve, flow velocity, circulation structure and turbulent characteristics, compare with the practical test to analyze the accuracy of different models to get the characteristic of curve flow movement effect better with the Reynolds stress model than the other three ε

k model.

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3）The paper in chapter four uses the Reynolds stress model to give further calculation of straight channel which has the equal length and same cross section in geometry with the lotus root-shape channels, then analyzes the related characteristic. Compared with the straight channels, the flow in the lotus root-shape channels is much more complex. In the lotus root-shape channels, the flow circulation and the turbulent fluctuation are stronger, namely more energy is transparent from water and dissipates through the viscosity force, and then the flow resistance increases.

4）Based on the portioning method, the basic concept of the cross-sectional form resistance is proposed. The additional resistance to flow caused by cross-sectional shape variation along the riser is called cross-sectional form resistance. Its value can be regarded as the difference between natural river resistance and the straight channel resistance whose length and cross-section are as same as the natural river. According to the numerical simulation results, the cross-sectional form resistance formula is obtained.

This paper presents a possible method to study the flow characteristics. Hope the related analysis and research in the paper can bring some light in the future study of the flow fluctuation and energy loss in hydraulics and river dynamics.

Key words: lotus root-shape channel flow, turbulent flow model, numerical simulation, cross-sectional form resistance