FEM_IO
Read or Write a Finite Element Model

FEM_IO is a FORTRAN90 library which reads or writes the data that defines a finite element model.

The finite element model is assumed to include three items:

• Node coordinates;
• Elements defined by a sequence of node indices;
• Node data;

Licensing:

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Related Data and Programs:

FEM is a data directory which contains a description of the data files that can be used to describe a finite element model.

FEM_50 is a MATLAB program which implements the finite element method in just 50 lines of code.

FEM_50_HEAT is a MATLAB program which implements a finite element calculation specifically for the heat equation.

FEM_BASIS_T3_DISPLAY is a MATLAB program which displays a basis function associated with a linear triangle ("T3") mesh.

FEM_BASIS_T6_DISPLAY is a MATLAB program which reads a quadratic triangle mesh and displays any associated basis function.

FEM_IO is available in a C++ version and a FORTRAN90 version and a MATLAB version.

FEM_TO_TEC is a MATLAB program which converts an FEM model into a TEC graphics file.

FEM1D, is a FORTRAN90 program which applies the finite element method, with piecewise linear basis functions, to a linear two point boundary value problem;

FEM1D_ADAPTIVE is a FORTRAN90 program which applies the finite element method to a linear two point boundary value problem in a 1D region, using adaptive refinement to improve the solution.

FEM1D_NONLINEAR is a FORTRAN90 program which applies the finite element method to a nonlinear two point boundary value problem in a 1D region.

FEM1D_PMETHOD is a FORTRAN90 program which applies the p-method version of the finite element method to a linear two point boundary value problem in a 1D region.

FEM1D_SAMPLE, a FORTRAN90 program which samples a scalar or vector finite element function of one variable, defined by FEM files, returning interpolated values at the sample points.

FEM2D_HEAT is a FORTRAN90 program which solves the time dependent heat equation in the unit square.

FEM2D_PACK is a FORTRAN90 library which contains utilities for 2D finite element calculations.

FEM2D_POISSON is a FORTRAN90 program which solves Poisson's equation on a square, using the finite element method.

FEM2D_SAMPLE is a FORTRAN90 library which evaluates a finite element function defined on an order 3 or order 6 triangulation.

FREE_FEM_HEAT is a FORTRAN90 program which uses the finite element method and the backward Euler method to solve the time-dependent heat equation on an arbitrary triangulated region in 2D. (The user supplies some information in some problem-dependent subroutines.)

FREE_FEM_NAVIER_STOKES is a FORTRAN90 program which solves Navier Stokes equations on a triangulated region, using the finite element method.

FREE_FEM_POISSON is a FORTRAN90 program which solves Poisson's equation on a triangulated region, using the finite element method.

FREE_FEM_STOKES is a FORTRAN90 program which solves the Stokes equations on a triangulated region, using the finite element method.

HOT_PIPE is a MATLAB program which can be run with FEM_50_HEAT.

HOT_POINT is a MATLAB program which can be run with FEM_50_HEAT.

PLTMG is a FORTRAN77 library which can solve elliptic partial differential equations using the finite element method with piecewise linear triangles and the multigrid approach.

TABLE is a file format which can be used to store real or integer arrays.

TABLE_IO is a FORTRAN90 library which reads and writes TABLE files.

Reference:

1. Hans Rudolf Schwarz,
   Finite Element Methods,
   Academic Press, 1988,
   ISBN: 0126330107,
   LC: TA347.F5.S3313..
2. Gilbert Strang, George Fix,
   An Analysis of the Finite Element Method,
   Cambridge, 1973,
   ISBN: 096140888X,
   LC: TA335.S77.
3. Olgierd Zienkiewicz,
   The Finite Element Method,
   Sixth Edition,
   Butterworth-Heinemann, 2005,
   ISBN: 0750663200,
   LC: TA640.2.Z54
4. Daniel Zwillinger, editor,
   CRC Standard Mathematical Tables and Formulae,
   30th Edition,
   CRC Press, 1996,
   ISBN: 0-8493-2479-3.

Source Code:

• fem_io.f90, the source code.
• fem_io.csh, commands to compile the source code.

Examples and Tests:

FEM_IO_PRB is a test program which tests the routines that read and write finite element data.

• fem_io_prb.f90 is the source code of the tests.
• fem_io_prb.csh runs all the tests.
• fem_io_prb_output.txt the output file.

ELL is an example of a 2D finite element model in which a scalar value is stored. This data was computed by the FREE_FEM_POISSON program and is read by FEM_READ.

• ell_node_coord.txt
• ell_element.txt
• ell_node_data.txt

TINY is a "tiny" example of a 2D finite element model in which a vector value is stored. This data was written by the FEM_WRITE routine.

• tiny_coord.txt
• tiny_element.txt
• tiny_node_data.txt

List of Routines:

• CH_CAP capitalizes a single character.
• CH_EQI is a case insensitive comparison of two characters for equality.
• CH_TO_DIGIT returns the integer value of a base 10 digit.
• DTABLE_DATA_READ reads data from a DTABLE file.
• DTABLE_DATA_WRITE writes data to a DTABLE file.
• DTABLE_HEADER_READ reads the header from a DTABLE file.
• DTABLE_HEADER_WRITE writes the header to a DTABLE file.
• FEM_DATA_READ reads data from a set of FEM files.
• FEM_HEADER_PRINT prints the header to set of FEM files.
• FEM_HEADER_READ reads the sizes of arrays in a set of FEM files.
• FEM_WRITE writes data files associated with a finite element solution.
• FILE_COLUMN_COUNT counts the number of columns in the first line of a file.
• FILE_NAME_SPECIFICATION determines the names of the input files.
• FILE_ROW_COUNT counts the number of rows in a file.
• GET_UNIT returns a free FORTRAN unit number.
• I4MAT_TRANSPOSE_PRINT prints an I4MAT, transposed.
• I4MAT_TRANSPOSE_PRINT_SOME prints some of the transpose of an I4MAT.
• ITABLE_DATA_READ reads data from an integer table file.
• ITABLE_DATA_WRITE writes data to an integer table file.
• ITABLE_HEADER_READ reads the header from an integer table file.
• ITABLE_HEADER_WRITE writes the header to an integer table file.
• R8MAT_TRANSPOSE_PRINT prints an R8MAT, transposed.
• R8MAT_TRANSPOSE_PRINT_SOME prints some of an R8MAT, transposed.
• S_BLANK_DELETE removes blanks from a string, left justifying the remainder.
• S_TO_I4 reads an I4 from a string.
• S_TO_I4VEC reads an I4VEC from a string.
• S_TO_R8 reads a R8 number from a string.
• S_TO_R8VEC reads a R8VEC from a string.
• S_WORD_COUNT counts the number of "words" in a string.
• TIMESTAMP prints the current YMDHMS date as a time stamp.
• TIMESTRING writes the current YMDHMS date into a string.

You can go up one level to the FORTRAN90 source codes.