It is very easy to create from scratch a simple finite element mesh, using the PREFEL pre-processor; this is explained in detail in the User Manual. In this demonstration, we will start from a simple mesh of three rectangular elements which has been already created and saved in the file h0.dat. The contents of the ASCII data file can be seen typed in the MS-DOS window. The file defines the node numbering around each element, and the coordinates of each node (compare this with the mesh shown at the foot of this page).
We will use the "main engine" POISS.FOR to solve the Poisson equation
k_x u_{xx} + k_y u_{yy} = f(x,y)
over our mesh, with the function u(x,y) taking specified values on the Dirichlet part of the boundary. In
this example we set k_x and k_y to 1.0; these are the parameter values in the last two lines of the data file.
We also take f(x,y)=1; this function is defined as a function call in POISS.FOR.
The pre-processor is now run, by typing the run command "prefel" (from an MS-DOS window) or clicking on the PREFEL icon (seen at bottom left of screenshot)
The pre-processor presents a list of all the input data files in the directory, from which "H0.DAT" is selected.
FELIPE opens a graphics window. Here we see the three-element mesh displayed. The user can click on options in the bar down the right-hand side, to add element or node numbering, to find the coordinates of a particular node, to zoom, etc.