基于水土耦合的沟床起动型流体运动过程模拟研究

Simulation Study on the Starting-type Fluid Movement Process of Gully Bed Based on Water and Soil Coupling

建立考虑沟床侵蚀、坡面汇流以及上空降雨共同作用下沟道流体运动的水土耦合模型,可以为流域风险评估、防灾减灾和潜在性泥石流沟判识等提供理论依据。通过分析沟道流体对沟床可移动固体物源的侵蚀过程,并将其与具有时空变异性的坡面汇流及上空降雨进行合理耦合,建立了小流域沟道流体运动的水土耦合模型;采用有限差分法对流体运动水土耦合模型进行时空离散,得到了沟道流体运动数值离散模型;在此基础上,基于MATLAB语言编写了流体运动数值离散模型的求解程序;同时,以来流流量及沟槽坡度为控制变量开展了室内模型实验,观测不同工况条件下沟槽控制点处流体流深、流速以及流体容重的变化情况。通过对所得到的12组水槽实验的实验结果进行数据分析,发现在沟槽坡度保持不变的条件下,沟槽控制点处流体流深及流体流速与来流流量之间呈正相关关系,流体容重与来流流量之间呈负相关关系;同时,将沟槽控制点处流体流深、流速以及流体容重的数值求解结果与实验测量结果进行对比分析,发现流体流速和流体容重的模拟精度均高于90%,流体流深的模拟精度高于80%。表明所建立的小流域沟道流体运动的水土耦合模型基本合理,所采用的数值离散方法及所编写的模型求解程序较为可行。

A water–soil coupling model of channel fluid movement is established considering the interaction of gully bed erosion,slope confluence,and rainfall,which can provide theoretical basis for watershed risk assessment,disaster prevention and mitigation,and identification of potential debris flow gully.By analyzing the erosion process of the channel fluid on the movable solid source of the gully bed,and coupling it with the slope confluence and the rainfall over the channel with temporal and spatial variability,the water–soil coupling model of the channel fluid movement in the small watershed can be established.The finite difference method was used to discretize the water–soil coupling model of fluid movement in time and space.A computer code for the coupling model of fluid motion was written in MATLAB.Meanwhile,laboratory experiments were carried out with varying flow rates and groove slopes to observe the evolution of fluid flow depth,flow velocity and fluid bulk density under different working conditions.By analyzing the results of the 12 sets of experiments,it was found that under the condition that the slope of the groove remains unchanged,the fluid flow depth and the fluid velocity were positively correlated with the flow and the bulk density was negatively correlated with the flow.At the same time,the numerical simulation results of the fluid flow depth,flow velocity and fluid bulk dens-ity at the control point of the groove were compared to and analyzed with the experimental results.It was found that the simulation accuracy of the fluid flow velocity and fluid bulk density were higher than 90%,and the simulation accuracy of the fluid flow depth was higher than 80%.The results revealed that the established water-soil coupling model of the channel fluid movement in the small watershed is accurate.