def test_nonlinear_diagonalshift(self):
nelems = 10
domain, geom = mesh.rectilinear([nelems, 1])
geom *= [2 * numpy.pi / nelems, 1]
ubasis = domain.basis('spline', degree=2).vector(2)
u = ubasis.dot(function.Argument('dofs', [len(ubasis)]))
Geom = [.5 * geom[0], geom[1] + function.cos(geom[0])
] + u # compress by 50% and buckle
cons = solver.minimize('dofs',
domain.boundary['left,right'].integral(
(u**2).sum(0), degree=4),
droptol=1e-15).solve()
strain = .5 * (function.outer(Geom.grad(geom), axis=1).sum(0) -
function.eye(2))
energy = domain.integral(
((strain**2).sum([0, 1]) + 150 *
(function.determinant(Geom.grad(geom)) - 1)**2) *
function.J(geom),
degree=6)
nshift = 0
for iiter, (lhs, info) in enumerate(
solver.minimize('dofs', energy, constrain=cons)):
self.assertLess(iiter, 38)
if info.shift:
nshift += 1
if info.resnorm < self.tol:
break
self.assertEqual(nshift, 9)
def mk_case(override):
pspace = np.linspace(0, 2*np.pi, 4)
rspace = np.linspace(0, 1, 3)
domain, refgeom = mesh.rectilinear([rspace, pspace], periodic=(1,))
r, ang = refgeom
geom = fn.asarray((
(1 + 10 * r) * fn.cos(ang),
(1 + 10 * r) * fn.sin(ang),
))
case = cases.airfoil(mesh=(domain, refgeom, geom), lift=False, amax=10, rmax=10, piola=True)
case.precompute(force=override)
return case
def mk_mesh(nang, nrad, rmin, rmax):
aspace = np.linspace(0, 2 * np.pi, nang + 1)
rspace = np.linspace(0, 1, nrad + 1)
domain, refgeom = mesh.rectilinear([rspace, aspace], periodic=(1, ))
rad, theta = refgeom
K = 5
rad = (fn.exp(K * rad) - 1) / (np.exp(K) - 1)
x = (rad * (rmax - rmin) + rmin) * fn.cos(theta)
y = (rad * (rmax - rmin) + rmin) * fn.sin(theta)
geom = fn.asarray([x, y])
return domain, refgeom, geom
def test_nonlinear_diagonalshift(self):
nelems = 10
domain, geom = mesh.rectilinear([nelems,1])
geom *= [2*numpy.pi/nelems, 1]
ubasis = domain.basis('spline', degree=2).vector(2)
u = ubasis.dot(function.Argument('dofs', [len(ubasis)]))
Geom = [.5 * geom[0], geom[1] + function.cos(geom[0])] + u # compress by 50% and buckle
cons = solver.minimize('dofs', domain.boundary['left,right'].integral((u**2).sum(0), degree=4), droptol=1e-15).solve()
strain = .5 * (function.outer(Geom.grad(geom), axis=1).sum(0) - function.eye(2))
energy = domain.integral(((strain**2).sum([0,1]) + 150*(function.determinant(Geom.grad(geom))-1)**2)*function.J(geom), degree=6)
nshift = 0
for iiter, (lhs, info) in enumerate(solver.minimize('dofs', energy, constrain=cons)):
self.assertLess(iiter, 90)
if info.shift:
nshift += 1
if info.resnorm < self.tol:
break
self.assertEqual(nshift, 60)
def rotmat(angle):
return fn.asarray([
[fn.cos(angle), -fn.sin(angle)],
[fn.sin(angle), fn.cos(angle)],
])
def main(etype: str, btype: str, degree: int, nrefine: int):
'''
Adaptively refined Laplace problem on an L-shaped domain.
.. arguments::
etype [square]
Type of elements (square/triangle/mixed).
btype [h-std]
Type of basis function (h/th-std/spline), with availability depending on
the configured element type.
degree [2]
Polynomial degree
nrefine [5]
Number of refinement steps to perform.
'''
domain, geom = mesh.unitsquare(2, etype)
x, y = geom - .5
exact = (x**2 + y**2)**(1 / 3) * function.cos(
function.arctan2(y + x, y - x) * (2 / 3))
domain = domain.trim(exact - 1e-15, maxrefine=0)
linreg = util.linear_regressor()
with treelog.iter.fraction('level', range(nrefine + 1)) as lrange:
for irefine in lrange:
if irefine:
refdom = domain.refined
ns.refbasis = refdom.basis(btype, degree=degree)
indicator = refdom.integral(
'd(refbasis_n, x_k) d(u, x_k) J(x)' @ ns,
degree=degree * 2).eval(lhs=lhs)
indicator -= refdom.boundary.integral(
'refbasis_n d(u, x_k) n(x_k) J(x)' @ ns,
degree=degree * 2).eval(lhs=lhs)
supp = ns.refbasis.get_support(
indicator**2 > numpy.mean(indicator**2))
domain = domain.refined_by(refdom.transforms[supp])
ns = function.Namespace()
ns.x = geom
ns.basis = domain.basis(btype, degree=degree)
ns.u = 'basis_n ?lhs_n'
ns.du = ns.u - exact
sqr = domain.boundary['trimmed'].integral('u^2 J(x)' @ ns,
degree=degree * 2)
cons = solver.optimize('lhs', sqr, droptol=1e-15)
sqr = domain.boundary.integral('du^2 J(x)' @ ns, degree=7)
cons = solver.optimize('lhs', sqr, droptol=1e-15, constrain=cons)
res = domain.integral('d(basis_n, x_k) d(u, x_k) J(x)' @ ns,
degree=degree * 2)
lhs = solver.solve_linear('lhs', res, constrain=cons)
ndofs = len(ns.basis)
error = domain.integral('<du^2, sum:k(d(du, x_k)^2)>_i J(x)' @ ns,
degree=7).eval(lhs=lhs)**.5
rate, offset = linreg.add(numpy.log(len(ns.basis)),
numpy.log(error))
treelog.user(
'ndofs: {ndofs}, L2 error: {error[0]:.2e} ({rate[0]:.2f}), H1 error: {error[1]:.2e} ({rate[1]:.2f})'
.format(ndofs=len(ns.basis), error=error, rate=rate))
bezier = domain.sample('bezier', 9)
x, u, du = bezier.eval(['x', 'u', 'du'] @ ns, lhs=lhs)
export.triplot('sol.png', x, u, tri=bezier.tri, hull=bezier.hull)
export.triplot('err.png', x, du, tri=bezier.tri, hull=bezier.hull)
return ndofs, error, lhs
def main(nelems: int, etype: str, btype: str, degree: int,
epsilon: typing.Optional[float], contactangle: float, timestep: float,
mtol: float, seed: int, circle: bool, stab: stab):
'''
Cahn-Hilliard equation on a unit square/circle.
.. arguments::
nelems [20]
Number of elements along domain edge.
etype [square]
Type of elements (square/triangle/mixed).
btype [std]
Type of basis function (std/spline), with availability depending on the
configured element type.
degree [2]
Polynomial degree.
epsilon []
Interface thickness; defaults to an automatic value based on the
configured mesh density if left unspecified.
contactangle [90]
Wall contact angle in degrees.
timestep [.01]
Time step.
mtol [.01]
Threshold value for chemical potential peak to peak difference, used as
a stop criterion.
seed [0]
Random seed for the initial condition.
circle [no]
Select circular domain as opposed to a unit square.
stab [linear]
Stabilization method (linear/optimal/none).
'''
mineps = 1. / nelems
if epsilon is None:
treelog.info('setting epsilon={}'.format(mineps))
epsilon = mineps
elif epsilon < mineps:
treelog.warning('epsilon under crititical threshold: {} < {}'.format(
epsilon, mineps))
domain, geom = mesh.unitsquare(nelems, etype)
bezier = domain.sample('bezier', 5) # sample for plotting
ns = function.Namespace()
if not circle:
ns.x = geom
else:
angle = (geom - .5) * (numpy.pi / 2)
ns.x = function.sin(angle) * function.cos(angle)[[1, 0
]] / numpy.sqrt(2)
ns.epsilon = epsilon
ns.ewall = .5 * numpy.cos(contactangle * numpy.pi / 180)
ns.cbasis = ns.mbasis = domain.basis('std', degree=degree)
ns.c = 'cbasis_n ?c_n'
ns.dc = 'cbasis_n (?c_n - ?c0_n)'
ns.m = 'mbasis_n ?m_n'
ns.F = '.5 (c^2 - 1)^2 / epsilon^2'
ns.dF = stab.value
ns.dt = timestep
nrg_mix = domain.integral('F J(x)' @ ns, degree=7)
nrg_iface = domain.integral('.5 sum:k(d(c, x_k)^2) J(x)' @ ns, degree=7)
nrg_wall = domain.boundary.integral('(abs(ewall) + c ewall) J(x)' @ ns,
degree=7)
nrg = nrg_mix + nrg_iface + nrg_wall + domain.integral(
'(dF - m dc - .5 dt epsilon^2 sum:k(d(m, x_k)^2)) J(x)' @ ns, degree=7)
numpy.random.seed(seed)
state = dict(c=numpy.random.normal(0, .5, ns.cbasis.shape),
m=numpy.random.normal(0, .5,
ns.mbasis.shape)) # initial condition
with treelog.iter.plain('timestep', itertools.count()) as steps:
for istep in steps:
E = sample.eval_integrals(nrg_mix, nrg_iface, nrg_wall, **state)
treelog.user(
'energy: {0:.3f} ({1[0]:.0f}% mixture, {1[1]:.0f}% interface, {1[2]:.0f}% wall)'
.format(sum(E), 100 * numpy.array(E) / sum(E)))
x, c, m = bezier.eval(['x', 'c', 'm'] @ ns, **state)
export.triplot('phase.png', x, c, tri=bezier.tri, clim=(-1, 1))
export.triplot('chempot.png', x, m, tri=bezier.tri)
if numpy.ptp(m) < mtol:
break
state['c0'] = state['c']
state = solver.optimize(['c', 'm'],
nrg,
arguments=state,
tol=1e-10)
return state
