基于ANSYS CFX的细沟水流切应力分析

Analysis of Rill Flow Shear Stress Based on ANSYS CFX

摘要:

为探明细沟断面的发育过程，利用流体力学软件ANSYS CFX 15.0.7对细沟的发育变化过程进行数值仿真，研究细沟断面水流流速及切应力分布，结合实测细沟发育，分析了细沟断面水流流速特征和切应力特征，从计算流体力学角度探索了细沟在水流冲刷情况下的断面发育机理。结果表明：利用CFX数值仿真建模的方法，得到了染色法测定细沟水流流速时的修正系数为0.78。宽浅式细沟断面切应力小于窄深式断面，细沟水流切应力主要集中在1.41~2.10Pa之间。水流切应力决定着细沟断面的发育，断面各点的切应力与断面各点发育较为吻合，切应力与断面各点的发育密切相关。

关键词:细沟侵蚀; 水流切应力; 断面发育; CFX

Abstract:

In order to understand the relation between the developing process of rill erosion and flow shear stress, the paper simulated the developing process of rill erosion applying hydrodynamics software ANSYS CFX (version 15.0.7) to explore the distribution of flow velocity and shearing stress in the rill section. Based on flume experiment, 6m long flush tank was used and rill development in 8 sections was measured. The experimental flow rate was 800L/h. The paper anaylized the characteristics of flow velocity and sheer stress combined with the measured value of rill section and it is a supplement in computing hydrodynamics of the fracture mechanism of rills under water flow. The results showed that the rill section average flow velocity was 0.71 times of the surface velocity, the correction coefficient was 0.78 with the dye method to determine the rill flow velocity when using the way of CFX numerical simulate pattern method. Rill section shape affects the magnitude of shear stress. The sheer stress value of broadshallow section was less than the narrowdeep section which is between 1.41~2.10Pa. The shear stress determined the rill development, and the point sheer stress distribution of rill section was normal distribution. The point sheer stress of rill section was consistent with the rill development and sheer stress was tightly correlated with the development of each point in the section.

Key words:rill erosion; flow shear stress; section development; CFX