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"""This demo demonstrates how to compute functionals (or forms in
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general) over subsets of the mesh. The two functionals lift and
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drag are computed for the pressure field around a dolphin. Here, we
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use the pressure field obtained from solving the Stokes equations
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(see demo program in the sub directory
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src/demo/pde/stokes/taylor-hood).
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The calculation only includes the pressure contribution (not shear
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# Copyright (C) 2007 Kristian B. Oelgaard
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# This file is part of DOLFIN.
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# DOLFIN is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Lesser General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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# DOLFIN is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Lesser General Public License for more details.
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# You should have received a copy of the GNU Lesser General Public License
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# along with DOLFIN. If not, see <http://www.gnu.org/licenses/>.
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# Modified by Anders Logg, 2008.
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# Modified by Garth N. Wells, 2009.
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# First added: 2007-11-14
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# Last changed: 2008-12-27
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# Read the mesh from file
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mesh = Mesh("../mesh.xml.gz")
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# Create FunctionSpace for pressure field
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Vp = FunctionSpace(mesh, "CG", 1)
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p = Function(Vp, "../pressure.xml.gz")
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# Define sub domain for the dolphin
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class Fish(SubDomain):
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def inside(self, x, on_boundary):
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return x[0] > DOLFIN_EPS and x[0] < (1.0 - DOLFIN_EPS) and \
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x[1] > DOLFIN_EPS and x[1] < (1.0 - DOLFIN_EPS)
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# Define functionals for drag and lift
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# Assemble functionals over sub domain
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drag = assemble(D, mesh=mesh, exterior_facet_domains=fish)
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lift = assemble(L, mesh=mesh, exterior_facet_domains=fish)
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print "Lift: %f" %lift
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print "Drag: %f" %drag
added
removed
demo/undocumented/lift-drag2/python/demo_lift-drag.py
