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RROMPy/rrompy/hfengines/linear_problem/helmholtz_square_bubble_problem_engine.py
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helmholtz_square_bubble_problem_engine.py
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# Copyright (C) 2018 by the RROMPy authors
#
# This file is part of RROMPy.
#
# RROMPy 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 3 of the License, or
# (at your option) any later version.
#
# RROMPy 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 RROMPy. If not, see <http://www.gnu.org/licenses/>.
#
import numpy as np
import fenics as fen
from .helmholtz_problem_engine import HelmholtzProblemEngine
__all__ = ['HelmholtzSquareBubbleProblemEngine']
class HelmholtzSquareBubbleProblemEngine(HelmholtzProblemEngine):
"""
Solver for square bubble Helmholtz problems with parametric wavenumber.
- \Delta u - omega^2 * u = f in \Omega
u = 0 on \Gamma_D
with exact solution square bubble times plane wave.
"""
def __init__(self, kappa:float, theta:float, n:int,
degree_threshold : int = np.inf, verbosity : int = 10):
super().__init__(degree_threshold = degree_threshold,
verbosity = verbosity)
self.omega = kappa
pi = np.pi
mesh = fen.RectangleMesh(fen.Point(0, 0), fen.Point(pi, pi), n, n)
self.V = fen.FunctionSpace(mesh, "P", 3)
c, s = np.cos(theta), np.sin(theta)
x, y = fen.SpatialCoordinate(mesh)[:]
C = 16. / pi ** 4.
bR = C * 2 * (x * (pi - x) + y * (pi - y))
bI = C * 2 * kappa * (c * (pi - 2 * x) * y * (pi - y)
+ s * x * (pi - x) * (pi - 2 * y))
wR = fen.cos(kappa * (c * x + s * y))
wI = fen.sin(kappa * (c * x + s * y))
self.forcingTerm = [bR * wR + bI * wI, bI * wR - bR * wI]
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