基于改进弃单元法的渗流自由面计算

为了将计算渗流自由面的弃单元法应用于ANSYS软件中,对其进行了改进,即根据每次迭代计算结果,将节点全部位于自由面以上的单元均删掉,从而使得总体传导矩阵的阶数不断降低,计算效率得到提高。在计算复合单元等效渗透系数时,对复合单元进行二次细分,以减小单元尺寸对计算结果的影响。计算收敛后,对复合单元上的节点插值求出零压头点坐标,再对零压头点进行曲线拟合或曲面拟合即得自由面。基于该方法,利用ANSYS的APDL语言编制了渗流自由面分析程序,并进行了实例分析。结果表明,提出的改进方法结构简单、精度较高。

Seepage Analysis of Free Surface Based on Improved Abandoned Element Method

In order to generalize the abandoned element method for seepage analysis of free surface in ANSYS, the abandoned element method was improved. In this method, the elements whose nodes are all upon the free surface were deleted according to the results in every iterative computation. So, the computational efficiency was improved because the order of global conductivity matrix was decreased continuously. To reduce the influence of the element size on the computational results, the composite elements were further subdivided in the process of equivalent permeability computation. When the computation converged, zero pressure head points were determined by interpolation of node. And then the free surface was obtained by curve or surface fitting. Based on this method, seepage analysis program was coded with the APDL language of ANSYS and two typical cases were computed. The results show that the improved method is simple and the computation accuracy is satisfactory.