If I understand libmesh correctly, if you are solving a system that has a
vector solution (i.e., velocity) then you need to add variables such as
"vx" and "vy" for each component. Then solve the system using submatrices
and vectors etc. Therefore, the libmesh::System add_vector command is only
for storing supplement data. Is this correct libmesh logic?
If I am correct above, then how do a write an initialization function for
such a problem? I attached a sample program below that doesn't work because
the initial_velocity function is called for both and the first value of the
output vector is assigned to both vx and vy. How do I assign different
values for the different directions?
Thanks,
Andrew
// Standard library includes
#include <iostream>
#include <algorithm>
#include <math.h>
#include <stdio.h>
#include <string>
using std::string;
// libMesh includes
#include "libmesh.h"
#include "mesh.h"
#include "mesh_generation.h"
#include "equation_systems.h"
#include "nonlinear_implicit_system.h"
#include "transient_system.h"
#include "explicit_system.h"
#include "analytic_function.h"
#include "exodusII_io.h"
// Bring in everything from the libMesh namespace
using namespace libMesh;
// A function for initializing, this d
void initial_velocity(DenseVector<Number>& output, const Point&, const
Real){
output(0) = 1; // x-dir
// output(1) = 2; // y-dir (this causes an error, but this is what seems
logical)
}
void init_cd (EquationSystems& es, const std::string&){
TransientNonlinearImplicitSystem& system =
es.get_system<TransientNonlinearImplicitSystem>("test");
AnalyticFunction<Number> fobj(initial_velocity);
system.project_solution(&fobj);
}
// The main function
int main (int argc, char** argv){
// Initialize libraries
LibMeshInit init (argc, argv);
// Generate a mesh
Mesh mesh;
MeshTools::Generation::build_square(mesh, 1, 1, -1., 1, -1, 1, QUAD4);
mesh.all_first_order();
// Create an equation system
EquationSystems eq_sys(mesh);
// Create a system and add two variables (x and y velocity components)
eq_sys.add_system<TransientNonlinearImplicitSystem>("test");
eq_sys.get_system("test").add_variable("vx", FIRST);
eq_sys.get_system("test").add_variable("vy", FIRST);
// Attach initilization function
eq_sys.get_system("test").attach_init_function(init_cd);
// Initilize the equation system storing the data
eq_sys.get_system("test").init();
// Export the solution
ExodusII_IO(mesh).write_equation_systems("example3b.ex2", eq_sys);
// Done
return 0;
}
--
Andrew E. Slaughter, PhD
[email protected]
Materials Process Design and Control Laboratory
Sibley School of Mechanical and Aerospace Engineering
169 Frank H. T. Rhodes Hall
Cornell University
Ithaca, NY 14853-3801
(607) 229-1829
http://aeslaughter.github.com/
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