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#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Python GetFEM interface
#
# Copyright (C) 2015-2020 FABRE Mathieu, SECK Mamadou, DALLERIT Valentin,
# Yves Renard, Tetsuo Koyama.
#
# This file is a part of GetFEM
#
# GetFEM is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
# License for more details.
# You should have received a copy of the GNU Lesser General Public License
# along with this program; if not, write to the Free Software Foundation,
# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
#
############################################################################
""" Simple demo of a wave equation solved with a Newmark scheme with the
Getfem tool for time integration schemes
This program is used to check that python-getfem is working. This is
also a good example of use of GetFEM.
"""
import os
import numpy as np
import getfem as gf
NX = 10
m = gf.Mesh('cartesian', np.arange(0., 1.+1./NX,1./NX),
np.arange(0., 1.+1./NX,1./NX));
## create a mesh_fem of for a field of dimension 1 (i.e. a scalar field)
mf = gf.MeshFem(m,1)
mf.set_classical_fem(2)
## Integration which will be used
mim = gf.MeshIm(m, 4)
## Detect the border of the mesh
border = m.outer_faces()
m.set_region(1, border)
## Interpolate the initial data
U0 = mf.eval('y*(y-1.)*x*(x-1.)*x*x')
V0 = 0.*U0
md=gf.Model('real');
md.add_fem_variable('u', mf);
md.add_fem_variable('u1', mf);
md.add_fem_variable('u2', mf);
md.add_Laplacian_brick(mim, 'u');
md.add_Laplacian_brick(mim, 'u1');
md.add_Laplacian_brick(mim, 'u2');
md.add_Dirichlet_condition_with_multipliers(mim, 'u', mf, 1);
md.add_Dirichlet_condition_with_multipliers(mim, 'u1', mf, 1);
md.add_Dirichlet_condition_with_multipliers(mim, 'u2', mf, 1);
# md.add_Dirichlet_condition_with_penalization(mim, 'u', 1E9, 1);
# md.add_Dirichlet_condition_with_simplification('u', 1);
## Transient part.
T = 5.0;
# Set dt smaller to fix Newmark and Houbolt method.
# dt = 0.001;
dt = 0.025;
beta = 0.25;
gamma = 0.5;
md.add_Newmark_scheme('u', beta, gamma)
md.add_Houbolt_scheme('u1')
md.add_Newmark_scheme('u2', beta, gamma)
md.add_mass_brick(mim, 'Dot2_u')
md.add_mass_brick(mim, 'Dot2_u1')
md.add_lumped_mass_for_first_order_brick(mim, 'Dot2_u2')
md.set_time_step(dt)
## Initial data.
md.set_variable('Previous_u', U0)
md.set_variable('Previous_Dot_u', V0)
md.set_variable('Previous_u1', U0)
md.set_variable('Previous2_u1', U0)
md.set_variable('Previous3_u1', U0)
md.set_variable('Previous_u2', U0)
md.set_variable('Previous_Dot_u2', V0)
## Initialisation of the acceleration 'Previous_Dot2_u'
md.perform_init_time_derivative(dt/2.)
md.solve()
A0 = md.variable('Previous_Dot2_u')
os.system('mkdir results');
mf.export_to_vtk('results/displacement_0.vtk', U0)
mf.export_to_vtk('results/velocity_0.vtk', V0)
mf.export_to_vtk('results/acceleration_0.vtk', A0)
A0 = 0.*U0
## Iterations
n = 1;
for t in np.arange(0.,T,dt):
print ('Time step %g' % t)
md.solve();
U = md.variable('u')
V = md.variable('Dot_u')
A = md.variable('Dot2_u')
mf.export_to_vtk('results/displacement_%d.vtk' % n, U)
mf.export_to_vtk('results/velocity_%d.vtk' % n, V)
mf.export_to_vtk('results/acceleration_%d.vtk' % n, A)
U = md.variable('u1')
V = md.variable('Dot_u1')
A = md.variable('Dot2_u1')
U = md.variable('u2')
V = md.variable('Dot_u2')
A = md.variable('Dot2_u2')
n += 1
md.shift_variables_for_time_integration()
print ('You can view solutions with for instance:\nmayavi2 -d results/displacement_0.vtk -f WarpScalar -m Surface')
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