台阶式溢洪道数值模拟计算精度评价方法

Evaluation Method of Numerical Simulation Calculation Accuracy of Stepped Spillway

随着CFD领域和计算机技术的发展,许多学者开始采用数值模拟的方法对台阶式溢洪道的水力特性进行细致研究,但学界并没有评价其计算精度的一致方法。采用从致密至粗糙3种网格尺寸,利用Flow 3D^(®)软件对台阶式溢洪道上的水汽二相流进行数值模拟,提供评价其计算精度的一般方法。首先通过计算网格收敛指数法(GCI)以优选网格尺寸,在保证计算精度的同时缩短计算时长;再以物模试验测量结果作为参照,评价在推荐网格尺寸下数值模拟计算结果的精确性。结果表明:使用相同的网格加密因子可以大幅简化GCI的计算过程,推荐采用全局GCI小于5%的网格尺寸;Flow 3D^(®)软件对台阶式溢洪道上关键水力学参数的计算精度较高,且对纯水流的计算精度优于对水汽二相流的计算精度。

With the development of CFD and computer technology,many scholars have begun to use numerical simulation methods to conduct a lot of detailed research on the hydraulic characteristics of stepped spillways,but there is no consistent method for evaluating the accuracy of their calculations.In this paper,three grid sizes ranging from dense to coarse are used to numerically simulate the air-water twophase flow on a stepped spillway by using Flow 3D^(®)software,to provide a general method to evaluate its calculation accuracy.Firstly,the grid size is optimized by calculating the grid convergence index(GCI),which can shorten the calculation time while ensuring the calculation accuracy.Then,by using the physical model test measurement results as a reference,the accuracy of the numerical simulation calculation results under the recommended mesh size is evaluated.The results show that using the same mesh refinement factor can greatly simplify the calculation process of GCI.It is recommended using a grid size with a global GCI less than 5%.Although slightly lower than the calculation accuracy for pure water flow,Flow 3D^(®)software still has high calculation accuracy for the key hydraulic parameters of the air-water two-phase flow on the stepped spillway.