FEM3: A Finite-Element Model for the Simulation of Heavy-Gas Dispersion and Incompressible Flow. User's Manual

摘要

FEM3 is a numerical model developed primarily to simulate heavy gas dispersion in the atmosphere, such as the gravitational spread and vapor dispersion that result from an accidental spill of liquefied natural gas (LNG). The model is based on solving the time-dependent, multidimensional conservation equations of mass, momentum, energy, and species. To accommodate large density changes and yet preclude sound waves, a generalized anelastic approximation is employed (i.e., the fluid is considered to be basically incompressible but to have variable density). A modified Galerkin finite element method (GFEM) with eight-node isoparametric hexahedron elements (four-node quadrilaterals in two dimensions) is used for spatial discretization, and a modified forward Euler method is employed for time integration. The discretized Poisson equation for pressure is solved implicitly by means of a skyline solver. In this report, the theoretical and numerical aspects of the model are described briefly, user's guides for using the model are given, and a numerical example is presented to illustrate the use of the model. (ERA citation 08:035188)