Abstract
This paper reports the fundamental performance in three-dimensional (3D) seepage problems of finite element methods (FEM) using the Raviart-Thomas mixed interpolant (RT), which is capable of independent interpolation of hydraulic head and velocity. In the conventional FEM that uses only hydraulic head as an unknown variable, velocity is independently calculated for each element. There are cases, therefore, where a continuous velocity field cannot be computed with high accuracy. In the RT, fluxes can be made continuous along inter-element boundaries because velocity shape functions employ the fluxes at the element faces as degrees of freedom. Although almost all of the previous studies have shown validity in 2D problems, this paper identifies the fundamental performance, including drawbacks, of the 3D elements with RT. The validity and significant notice of the FEM with RT in the engineering simulation is presented by getting its characteristic in order.
