def example():
verts = 0,1,3,4,10
domain, geom = mesh.rectilinear( [ verts ] )
basis = BSpline( degree=2, knotvalues=verts, knotmultiplicities=[1,2,3,1,1] ).build(domain)
x, y = domain.elem_eval( [ geom[0], basis ], ischeme='bezier9' )
with plot.PyPlot( '1D' ) as plt:
plt.plot( x, y, '-' )
verts = numpy.arange(10)
domain, geom = mesh.rectilinear( [ verts ] )
basis = Mod( Mod( Spline( degree=2, rmlast=True ), 2 ), -3 ).build(domain)
x, y = domain.elem_eval( [ geom[0], basis ], ischeme='bezier9' )
with plot.PyPlot( '1D' ) as plt:
plt.plot( x, y, '-' )
verts = numpy.arange(10)
domain, geom = mesh.rectilinear( [ verts ] )
basis = Mod( Mod( Spline( degree=2, periodic=True ), 2 ), 4 ).build(domain)
x, y = domain.elem_eval( [ geom[0], basis ], ischeme='bezier9' )
with plot.PyPlot( '1D' ) as plt:
plt.plot( x, y, '-' )
domain, geom = mesh.rectilinear( [ numpy.arange(5) ] * 2 )
basis = ( Spline( degree=1, rmfirst=True ) * Mod( Spline( degree=2, periodic=True ), 2 ) ).build(domain)
x, y = domain.elem_eval( [ geom, basis ], ischeme='bezier5' )
with plot.PyPlot( '2D' ) as plt:
for i, yi in enumerate( y.T ):
plt.subplot( 4, 4, i+1 )
plt.mesh( x, yi )
plt.gca().set_axis_off()
def test_discontinuous(self):
pdomain, pgeom = mesh.rectilinear([3], periodic=[0])
rdomain, rgeom = mesh.rectilinear([3])
pbasis = pdomain.basis('spline', degree=2, knotmultiplicities=[[3,1,2,3]])
rbasis = rdomain.basis('spline', degree=2, knotmultiplicities=[[1,1,2,1]])
psampled = pdomain.sample('gauss', 2).eval(pbasis)
rsampled = rdomain.sample('gauss', 2).eval(rbasis)
self.assertAllAlmostEqual(psampled, rsampled)
def setUp(self):
super().setUp()
if not self.product:
self.domain, self.geom = mesh.rectilinear([2,3])
else:
domain1, geom1 = mesh.rectilinear([2])
domain2, geom2 = mesh.rectilinear([3])
self.domain = domain1 * domain2
self.geom = function.concatenate(function.bifurcate(geom1, geom2), axis=0)
def setUp(self):
super().setUp()
domain, geom = mesh.rectilinear([numpy.linspace(0, 1, 9)] * 2)
ubasis = domain.basis('std', degree=2)
if self.vector:
u = ubasis.vector(2).dot(
function.Argument('dofs', [len(ubasis) * 2]))
else:
u = (ubasis[:, numpy.newaxis] *
function.Argument('dofs', [len(ubasis), 2])).sum(0)
Geom = geom * [1.1, 1] + u
self.cons = solver.optimize('dofs',
domain.boundary['left,right'].integral(
(u**2).sum(0), degree=4),
droptol=1e-15)
self.boolcons = ~numpy.isnan(self.cons)
strain = .5 * (function.outer(Geom.grad(geom), axis=1).sum(0) -
function.eye(2))
self.energy = domain.integral(
((strain**2).sum([0, 1]) + 20 *
(function.determinant(Geom.grad(geom)) - 1)**2) *
function.J(geom),
degree=6)
self.residual = self.energy.derivative('dofs')
self.tol = 1e-10
def setUp(self):
super().setUp()
verts = numpy.linspace(0, 1, self.nelems + 1)
self.domain, self.geom = mesh.rectilinear(
[verts], periodic=(0, ) if self.periodic else ())
self.basis = self.domain.basis(self.btype, degree=self.degree) if self.btype != 'spline' \
else self.domain.basis(self.btype, degree=self.degree, continuity=self.continuity)
def test_sparsity(self):
topo, geom = mesh.rectilinear([6] * self.ndim)
topo = topo.refined_by(
set(
map(
topo.transforms.index,
itertools.chain(topo[1:3].transforms,
topo[-2:].transforms))))
ns = function.Namespace()
ns.x = geom
ns.tbasis = topo.basis('th-spline',
degree=2,
truncation_tolerance=1e-14)
ns.tnotol = topo.basis('th-spline', degree=2, truncation_tolerance=0)
ns.hbasis = topo.basis('h-spline', degree=2)
tA, tA_tol, hA = topo.sample('gauss', 5).integrate_sparse([
ns.eval_ij('tbasis_i,k tbasis_j,k'),
ns.eval_ij('tnotol_i,k tnotol_j,k'),
ns.eval_ij('hbasis_i,k hbasis_j,k')
])
tA_nnz, tA_tol_nnz, hA_nnz = self.vals[self.ndim]
self.assertEqual(len(sparse.prune(sparse.dedup(tA))), tA_nnz)
self.assertEqual(len(sparse.prune(sparse.dedup(tA_tol))), tA_tol_nnz)
self.assertEqual(len(sparse.prune(sparse.dedup(hA))), hA_nnz)
def setUp(self):
super().setUp()
domain, geom = mesh.rectilinear([numpy.linspace(0,1,9)] * 2)
gauss = domain.sample('gauss', 5)
uin = geom[1] * (1-geom[1])
dx = function.J(geom, 2)
ubasis = domain.basis('std', degree=2)
pbasis = domain.basis('std', degree=1)
if self.single:
ubasis, pbasis = function.chain([ubasis.vector(2), pbasis])
dofs = function.Argument('dofs', [len(ubasis)])
u = ubasis.dot(dofs)
p = pbasis.dot(dofs)
dofs = 'dofs'
ures = gauss.integral((self.viscosity * (ubasis.grad(geom) * (u.grad(geom) + u.grad(geom).T)).sum([-1,-2]) - ubasis.div(geom) * p) * dx)
dres = gauss.integral((ubasis * (u.grad(geom) * u).sum(-1)).sum(-1) * dx)
else:
u = (ubasis[:,numpy.newaxis] * function.Argument('dofs', [len(ubasis), 2])).sum(0)
p = (pbasis * function.Argument('pdofs', [len(pbasis)])).sum(0)
dofs = 'dofs', 'pdofs'
ures = gauss.integral((self.viscosity * (ubasis[:,numpy.newaxis].grad(geom) * (u.grad(geom) + u.grad(geom).T)).sum(-1) - ubasis.grad(geom) * p) * dx)
dres = gauss.integral(ubasis[:,numpy.newaxis] * (u.grad(geom) * u).sum(-1) * dx)
pres = gauss.integral((pbasis * u.div(geom)) * dx)
cons = solver.optimize('dofs', domain.boundary['top,bottom'].integral((u**2).sum(), degree=4), droptol=1e-10)
cons = solver.optimize('dofs', domain.boundary['left'].integral((u[0]-uin)**2 + u[1]**2, degree=4), droptol=1e-10, constrain=cons)
self.cons = cons if self.single else {'dofs': cons}
stokes = solver.solve_linear(dofs, residual=ures + pres if self.single else [ures, pres], constrain=self.cons)
self.arguments = dict(dofs=stokes) if self.single else stokes
self.residual = ures + dres + pres if self.single else [ures + dres, pres]
inertia = gauss.integral(.5 * (u**2).sum(-1) * dx).derivative('dofs')
self.inertia = inertia if self.single else [inertia, None]
self.tol = 1e-10
self.dofs = dofs
self.frozen = types.frozenarray if self.single else solver.argdict
def setUp(self):
super().setUp()
self.ns = function.Namespace()
self.domain, self.ns.geom = mesh.rectilinear([2,2])
self.ns.ubasis = self.domain.basis('std', degree=1)
self.ns.u = 'ubasis_n ?dofs_n'
self.optimize = solver.optimize if not self.minimize else lambda *args, newtontol=0, **kwargs: solver.minimize(*args, **kwargs).solve(newtontol)
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 navierstokes():
domain, geom = mesh.rectilinear( [numpy.linspace(0,1,9)] * 2 )
ubasis, pbasis = function.chain([
domain.basis( 'std', degree=2 ).vector(2),
domain.basis( 'std', degree=1 ),
])
dofs = function.DerivativeTarget( [len(ubasis)] )
u = ubasis.dot( dofs )
p = pbasis.dot( dofs )
viscosity = 1
inertia = model.Integral( (ubasis * u).sum(-1), domain=domain, geometry=geom, degree=5 )
stokesres = model.Integral( viscosity * ubasis['ni,j'] * (u['i,j']+u['j,i']) - ubasis['nk,k'] * p + pbasis['n'] * u['k,k'], domain=domain, geometry=geom, degree=5 )
residual = stokesres + model.Integral( ubasis['ni'] * u['i,j'] * u['j'], domain=domain, geometry=geom, degree=5 )
cons = domain.boundary['top,bottom'].project( [0,0], onto=ubasis, geometry=geom, ischeme='gauss2' ) \
| domain.boundary['left'].project( [geom[1]*(1-geom[1]),0], onto=ubasis, geometry=geom, ischeme='gauss2' )
lhs0 = model.solve_linear( dofs, residual=stokesres, constrain=cons )
for name in 'direct', 'newton', 'pseudotime':
@unittest( name=name, raises=name=='direct' and model.ModelError)
def res():
tol = 1e-10
if name == 'direct':
lhs = model.solve_linear( dofs, residual=residual, constrain=cons )
elif name == 'newton':
lhs = model.newton( dofs, residual=residual, lhs0=lhs0, freezedofs=cons.where ).solve( tol=tol, maxiter=2 )
else:
lhs = model.pseudotime( dofs, residual=residual, lhs0=lhs0, freezedofs=cons.where, inertia=inertia, timestep=1 ).solve( tol=tol, maxiter=3 )
res = residual.replace( dofs, lhs ).eval()
resnorm = numpy.linalg.norm( res[~cons.where] )
assert resnorm < tol
def main(viscosity=1.3e-3, density=1e3, pout=223e5, uw=-0.01, nelems=10):
# viscosity = 1.3e-3
# density = 1e3
# pout = 223e5
# nelems = 10
# uw = -0.01
domain, geom = mesh.rectilinear([numpy.linspace(0, 1, nelems), numpy.linspace(1, 2, nelems), [0, 2 * numpy.pi]],
periodic=[2])
domain = domain.withboundary(inner='bottom', outer='top')
ns = function.Namespace()
ns.y, ns.r, ns.θ = geom
ns.x_i = '<r cos(θ), y, r sin(θ)>_i'
ns.uybasis, ns.urbasis, ns.pbasis = function.chain([
domain.basis('std', degree=3, removedofs=((0,-1), None, None)), # remove normal component at y=0 and y=1
domain.basis('std', degree=3, removedofs=((0,-1), None, None)), # remove tangential component at y=0 (no slip)
domain.basis('std', degree=2)])
ns.ubasis_ni = '<urbasis_n cos(θ), uybasis_n, urbasis_n sin(θ)>_i'
ns.viscosity = viscosity
ns.density = density
ns.u_i = 'ubasis_ni ?lhs_n'
ns.p = 'pbasis_n ?lhs_n'
ns.sigma_ij = 'viscosity (u_i,j + u_j,i) - p δ_ij'
ns.pout = pout
ns.uw = uw
ns.uw_i = 'uw <cos(phi), 0, sin(phi)>_i'
ns.tout_i = '-pout n_i'
ns.uw_i = 'uw n_i' # uniform outflow
res = domain.integral('(viscosity ubasis_ni,j u_i,j - p ubasis_ni,i + pbasis_n u_k,k) d:x' @ ns, degree=6)
# res -= domain[1].boundary['inner'].integral('ubasis_ni tout_i d:x' @ ns, degree=6)
sqr = domain.boundary['inner'].integral('(u_i - uw_i) (u_i - uw_i) d:x' @ ns, degree=6)
# sqr = domain.boundary['outer'].integral('(u_i - uin_i) (u_i - uin_i) d:x' @ ns, degree=6)
sqr -= domain.boundary['outer'].integral('(p - pout) (p - pout) d:x' @ ns, degree=6)
cons = solver.optimize('lhs', sqr, droptol=1e-15)
lhs = solver.solve_linear('lhs', res, constrain=cons)
plottopo = domain[:, :, 0:].boundary['back']
bezier = plottopo.sample('bezier', 10)
r, y, p, u = bezier.eval([ns.r, ns.y, ns.p, function.norm2(ns.u)], lhs=lhs)
with export.mplfigure('pressure.png', dpi=800) as fig:
ax = fig.add_subplot(111, title='pressure', aspect=1)
ax.autoscale(enable=True, axis='both', tight=True)
im = ax.tripcolor(r, y, bezier.tri, p, shading='gouraud', cmap='jet')
ax.add_collection(
collections.LineCollection(numpy.array([y, r]).T[bezier.hull], colors='k', linewidths=0.2, alpha=0.2))
fig.colorbar(im)
uniform = plottopo.sample('uniform', 1)
r_, y_, uv = uniform.eval([ns.r, ns.y, ns.u], lhs=lhs)
with export.mplfigure('velocity.png', dpi=800) as fig:
ax = fig.add_subplot(111, title='Velocity', aspect=1)
ax.autoscale(enable=True, axis='both', tight=True)
im = ax.tripcolor(r, y, bezier.tri, u, shading='gouraud', cmap='jet')
ax.quiver(r_, y_, uv[:, 0], uv[:, 1], angles='xy', scale_units='xy')
fig.colorbar(im)
def laplace():
domain, geom = mesh.rectilinear([8, 8])
basis = domain.basis('std', degree=1)
cons = domain.boundary['left'].project(0,
onto=basis,
geometry=geom,
ischeme='gauss2')
dofs = function.DerivativeTarget([len(basis)])
u = basis.dot(dofs)
residual = model.Integral( ( basis.grad(geom) * u.grad(geom) ).sum(-1), domain=domain, geometry=geom, degree=2 ) \
+ model.Integral( basis, domain=domain.boundary['top'], geometry=geom, degree=2 )
for name in 'direct', 'newton':
@unittest(name=name)
def res():
if name == 'direct':
lhs = model.solve_linear(dofs,
residual=residual,
constrain=cons)
else:
lhs = model.newton(dofs,
residual=residual,
lhs0=cons | 0,
freezedofs=cons.where).solve(tol=1e-10,
maxiter=0)
res = residual.replace(dofs, lhs).eval()
resnorm = numpy.linalg.norm(res[~cons.where])
assert resnorm < 1e-13
def test(self):
for knotmultiplicities, ndofs in [([3,1,3], 4), ([3,2,1,3], 6)]:
domain, geom = mesh.rectilinear([len(knotmultiplicities)-1], periodic=[0])
basis = domain.basis('spline', degree=3, knotmultiplicities=[knotmultiplicities])
self.assertEqual(len(basis), ndofs)
self.assertContinuous(topo=domain, geom=geom, basis=basis, continuity=0)
self.assertPartitionOfUnity(topo=domain, basis=basis)
def setUp(self):
super().setUp()
domain, geom = mesh.rectilinear([numpy.linspace(0, 1, 9)] * 2)
ubasis, pbasis = function.chain([
domain.basis('std', degree=2).vector(2),
domain.basis('std', degree=1),
])
dofs = function.Argument('dofs', [len(ubasis)])
u = ubasis.dot(dofs)
p = pbasis.dot(dofs)
viscosity = 1e-3
self.inertia = domain.integral((ubasis * u).sum(-1) * function.J(geom),
degree=5)
stokesres = domain.integral(
(viscosity * (ubasis.grad(geom) *
(u.grad(geom) + u.grad(geom).T)).sum([-1, -2]) -
ubasis.div(geom) * p + pbasis * u.div(geom)) * function.J(geom),
degree=5)
self.residual = stokesres + domain.integral(
(ubasis *
(u.grad(geom) * u).sum(-1) * u).sum(-1) * function.J(geom),
degree=5)
self.cons = domain.boundary['top,bottom'].project([0,0], onto=ubasis, geometry=geom, ischeme='gauss4') \
| domain.boundary['left'].project([geom[1]*(1-geom[1]),0], onto=ubasis, geometry=geom, ischeme='gauss4')
self.lhs0 = solver.solve_linear('dofs',
residual=stokesres,
constrain=self.cons)
self.tol = 1e-10
def setUp(self):
super().setUp()
if self.ndims == 2:
domain, geom = mesh.unitsquare(4, self.variant)
nverts = 25
elif self.variant == 'tensor':
structured, geom = mesh.rectilinear(
[numpy.linspace(0, 1, 5 - i) for i in range(self.ndims)])
domain = topology.ConnectedTopology(structured.references,
structured.transforms,
structured.opposites,
structured.connectivity)
nverts = numpy.product([5 - i for i in range(self.ndims)])
elif self.variant == 'simplex':
numpy.random.seed(0)
nverts = 20
simplices = numeric.overlapping(numpy.arange(nverts),
n=self.ndims + 1)
coords = numpy.random.normal(size=(nverts, self.ndims))
root = transform.Identifier(self.ndims, 'test')
transforms = transformseq.PlainTransforms(
[(root, transform.Square((c[1:] - c[0]).T, c[0]))
for c in coords[simplices]], self.ndims)
domain = topology.SimplexTopology(simplices, transforms,
transforms)
geom = function.rootcoords(self.ndims)
else:
raise NotImplementedError
self.domain = domain
self.basis = domain.basis(
self.btype) if self.btype == 'bubble' else domain.basis(
self.btype, degree=self.degree)
self.geom = geom
self.nverts = nverts
def poisson_patch(bottom, right, top, left):
from nutils import version
if version != '3.0':
raise ImportError('Outdated nutils version detected, only v3.0 supported. Upgrade by \"pip install --upgrade nutils\"')
from nutils import mesh, function as fn
from nutils import _, log
# error test input
if left.rational or right.rational or top.rational or bottom.rational:
raise RuntimeError('poisson_patch not supported for rational splines')
# these are given as a oriented loop, so make all run in positive parametric direction
top.reverse()
left.reverse()
# in order to add spline surfaces, they need identical parametrization
Curve.make_splines_identical(top, bottom)
Curve.make_splines_identical(left, right)
# create computational (nutils) mesh
p1 = bottom.order(0)
p2 = left.order(0)
n1 = len(bottom)
n2 = len(left)
dim= left.dimension
k1 = bottom.knots(0)
k2 = left.knots(0)
m1 = [bottom.order(0) - bottom.continuity(k) - 1 for k in k1]
m2 = [left.order(0) - left.continuity(k) - 1 for k in k2]
domain, geom = mesh.rectilinear([k1, k2])
basis = domain.basis('spline', [p1-1, p2-1], knotmultiplicities=[m1,m2])
# assemble system matrix
grad = basis.grad(geom)
outer = fn.outer(grad,grad)
integrand = outer.sum(-1)
matrix = domain.integrate(integrand, geometry=geom, ischeme='gauss'+str(max(p1,p2)+1))
# initialize variables
controlpoints = np.zeros((n1,n2,dim))
rhs = np.zeros((n1*n2))
constraints = np.array([[np.nan]*n2]*n1)
# treat all dimensions independently
for d in range(dim):
# add boundary conditions
constraints[ 0, :] = left[ :,d]
constraints[-1, :] = right[ :,d]
constraints[ :, 0] = bottom[:,d]
constraints[ :,-1] = top[ :,d]
# solve system
lhs = matrix.solve(rhs, constrain=np.ndarray.flatten(constraints), solver='cg', tol=state.controlpoint_absolute_tolerance)
# wrap results into splipy datastructures
controlpoints[:,:,d] = np.reshape(lhs, (n1,n2), order='C')
return Surface(bottom.bases[0], left.bases[0], controlpoints, bottom.rational, raw=True)
def main(nelems: int, degree: int, reynolds: float):
'''
Driven cavity benchmark problem using compatible spaces.
.. arguments::
nelems [12]
Number of elements along edge.
degree [2]
Polynomial degree for velocity; the pressure space is one degree less.
reynolds [1000]
Reynolds number, taking the domain size as characteristic length.
'''
verts = numpy.linspace(0, 1, nelems + 1)
domain, geom = mesh.rectilinear([verts, verts])
ns = function.Namespace()
ns.x = geom
ns.Re = reynolds
ns.ubasis = function.vectorize([
domain.basis('spline',
degree=(degree, degree - 1),
removedofs=((0, -1), None)),
domain.basis('spline',
degree=(degree - 1, degree),
removedofs=(None, (0, -1)))
])
ns.pbasis = domain.basis('spline', degree=degree - 1)
ns.u_i = 'ubasis_ni ?u_n'
ns.p = 'pbasis_n ?p_n'
ns.stress_ij = '(d(u_i, x_j) + d(u_j, x_i)) / Re - p δ_ij'
ns.uwall = domain.boundary.indicator('top'), 0
ns.N = 5 * degree * nelems # nitsche constant based on element size = 1/nelems
ns.nitsche_ni = '(N ubasis_ni - (d(ubasis_ni, x_j) + d(ubasis_nj, x_i)) n(x_j)) / Re'
ures = domain.integral('d(ubasis_ni, x_j) stress_ij d:x' @ ns,
degree=2 * degree)
ures += domain.boundary.integral(
'(nitsche_ni (u_i - uwall_i) - ubasis_ni stress_ij n(x_j)) d:x' @ ns,
degree=2 * degree)
pres = domain.integral('pbasis_n (d(u_k, x_k) + ?lm) d:x' @ ns,
degree=2 * degree)
lres = domain.integral('p d:x' @ ns, degree=2 * degree)
with treelog.context('stokes'):
state0 = solver.solve_linear(['u', 'p', 'lm'], [ures, pres, lres])
postprocess(domain, ns, **state0)
ures += domain.integral('ubasis_ni d(u_i, x_j) u_j d:x' @ ns,
degree=3 * degree)
with treelog.context('navierstokes'):
state1 = solver.newton(('u', 'p', 'lm'), (ures, pres, lres),
arguments=state0).solve(tol=1e-10)
postprocess(domain, ns, **state1)
return state0, state1
def __init__(self, refine=1, degree=3, nel=None):
if nel is None:
nel = int(10 * refine)
xpts = np.linspace(0, 2, 2 * nel + 1)
ypts = np.linspace(0, 1, nel + 1)
domain, geom = mesh.rectilinear([xpts, ypts])
NutilsCase.__init__(self, 'Channel flow', domain, geom, geom)
bases = [
domain.basis('spline', degree=(degree, degree - 1)), # vx
domain.basis('spline', degree=(degree - 1, degree)), # vy
domain.basis('spline', degree=degree - 1), # pressure
[0] * 2, # stabilization terms
]
basis_lens = [len(b) for b in bases]
vxbasis, vybasis, pbasis, __ = fn.chain(bases)
vbasis = vxbasis[:, _] * (1, 0) + vybasis[:, _] * (0, 1)
self.bases.add('v', vbasis, length=sum(basis_lens[:2]))
self.bases.add('p', pbasis, length=basis_lens[2])
self.extra_dofs = 2
self.constrain('v', 'left', 'top', 'bottom')
x, y = geom
profile = (y * (1 - y))[_] * (1, 0)
self.integrals['lift'] = Affine(1, self.project_lift(profile, 'v'))
self.integrals['geometry'] = Affine(1, geom)
self._exact_solutions = {'v': profile, 'p': 4 - 2 * x}
self.integrals['divergence'] = AffineIntegral(
-1, fn.outer(vbasis.div(geom), pbasis))
self.integrals['laplacian'] = AffineIntegral(
1,
fn.outer(vbasis.grad(geom)).sum((-1, -2)))
self.integrals['v-h1s'] = AffineIntegral(
1,
fn.outer(vbasis.grad(geom)).sum([-1, -2]))
self.integrals['p-l2'] = AffineIntegral(1, fn.outer(pbasis))
self.integrals['convection'] = AffineIntegral(
1,
NutilsDelayedIntegrand('w_ia u_jb v_ka,b',
'ijk',
'wuv',
x=geom,
w=vbasis,
u=vbasis,
v=vbasis))
points = [(0, (0, 0)), (nel - 1, (0, 1))]
eqn = (vbasis.laplace(geom) - pbasis.grad(geom))[:, 0, _]
self.integrals['stab-lhs'] = AffineIntegral(
1,
collocate(domain, eqn, points, self.ndofs - self.extra_dofs,
self.ndofs))
def setUp(self):
super().setUp()
domain, geom = mesh.rectilinear([8,8])
basis = domain.basis('std', degree=1)
self.cons = domain.boundary['left'].project(0, onto=basis, geometry=geom, ischeme='gauss2')
dofs = function.Argument('dofs', [len(basis)])
u = basis.dot(dofs)
self.residual = domain.integral((basis.grad(geom) * u.grad(geom)).sum(-1), geometry=geom, degree=2) \
+ domain.boundary['top'].integral(basis, geometry=geom, degree=2)
def setUp(self):
super().setUp()
self.domain, self.geom = mesh.rectilinear([max(1, self.nelems-n) for n in range(self.ndims)], periodic=[0] if self.periodic else [])
for iref in range(self.nrefine):
self.domain = self.domain.refined_by([len(self.domain)-1])
if self.boundary:
self.domain = self.domain.boundary[self.boundary]
self.basis = self.domain.basis(self.btype, degree=self.degree)
self.gauss = 'gauss{}'.format(2*self.degree)
def main(
nelems: 'number of elements' = 20,
degree: 'polynomial degree' = 1,
timescale: 'time scale (timestep=timescale/nelems)' = .5,
tol: 'solver tolerance' = 1e-5,
ndims: 'spatial dimension' = 1,
endtime: 'end time, 0 for no end time' = 0,
withplots: 'create plots' = True,
):
# construct mesh
domain, geom = mesh.rectilinear([numpy.linspace(0, 1, nelems + 1)] * ndims,
periodic=range(ndims))
basis = domain.basis('discont', degree=degree)
# construct initial condition (centered gaussian)
u = function.exp(-(((geom - .5) * 5)**2).sum(-1))
lhs = domain.project(u, onto=basis, geometry=geom, ischeme='gauss5')
# prepare matrix
timestep = timescale / nelems
At = (1 / timestep) * function.outer(basis)
matrix0 = domain.integrate(At, geometry=geom, ischeme='gauss5')
# prepare plotting
makeplots = MakePlots(domain, geom, video=withplots
== 'video') if withplots else lambda *args: None
# start time stepping
for itime in log.count('timestep'):
makeplots(u)
if endtime and itime * timestep >= endtime:
break
rhs = matrix0.matvec(lhs)
for ipicard in log.count('picard'):
u = basis.dot(lhs)
beta = function.repeat(u[_], ndims, axis=0)
Am = -function.outer((basis[:, _] * beta).div(geom), basis)
dmatrix = domain.integrate(Am, geometry=geom, ischeme='gauss5')
alpha = .5 * function.sign(function.mean(beta).dotnorm(geom))
Ai = function.outer(
function.jump(basis),
(alpha * function.jump(basis[:, _] * beta) -
function.mean(basis[:, _] * beta)).dotnorm(geom))
dmatrix += domain.interfaces.integrate(Ai,
geometry=geom,
ischeme='gauss5')
lhs, info = (matrix0 + dmatrix).solve(rhs,
lhs0=lhs,
tol=tol,
restart=999,
precon='spilu',
info=True)
if info.niter == 0:
break
return rhs, lhs
def setUp(self):
super().setUp()
domain, geom = mesh.rectilinear([8,8])
basis = domain.basis('std', degree=1)
self.cons = domain.boundary['left'].project(0, onto=basis, geometry=geom, ischeme='gauss2')
dofs = function.Argument('dofs', [len(basis)])
u = basis.dot(dofs)
self.residual = domain.integral((basis.grad(geom) * u.grad(geom)).sum(-1)*function.J(geom), degree=2) \
+ domain.boundary['top'].integral(basis*function.J(geom), degree=2)
def splipy_to_nutils(spline):
""" Returns nutils domain and geometry object for spline mapping given by the argument """
from nutils import mesh, function
domain, geom = mesh.rectilinear(spline.knots())
cp = controlpoints(spline)
basis = domain.basis('spline', degree=degree(spline), knotmultiplicities=multiplicities(spline))
geom = function.matmat(basis, cp)
#TODO: add correct behaviour for rational and/or periodic geometries
return domain, geom
def setUp(self):
ns = function.Namespace()
domain, ns.x = mesh.rectilinear([10], periodic=(0,))
ns.basis = domain.basis('discont', degree=1)
ns.u = 'basis_n ?dofs_n'
ns.f = '.5 u^2'
self.residual = domain.integral('-basis_n,0 f d:x' @ ns, degree=2)
self.residual += domain.interfaces.integral('-[basis_n] n_0 ({f} - .5 [u] n_0) d:x' @ ns, degree=4)
self.inertia = domain.integral('basis_n u d:x' @ ns, degree=5)
self.lhs0 = numpy.sin(numpy.arange(len(ns.basis))) # "random" initial vector
def main(alpha=0.01, nelems=64, degree=2, dt=0.01, tend=1):
# construct topology, geometry and basis
verts = numpy.linspace(0, 1, nelems + 1)
domain, geom = mesh.rectilinear([verts, verts])
basis = domain.basis('spline', degree=degree)
ischeme = 'gauss4'
print(basis)
exit()
# construct matrices
A = 1 / dt * basis['i'] * basis['j'] + alpha / 2 * basis['i,k'] * basis[
'j,k']
B = 1 / dt * basis['i'] * basis['j'] - alpha / 2 * basis['i,k'] * basis[
'j,k']
A, B = domain.integrate([A, B], geometry=geom, ischeme=ischeme)
# construct dirichlet boundary constraints
cons = domain.boundary.project(0,
onto=basis,
geometry=geom,
ischeme=ischeme)
# construct initial condition
x0, x1 = geom
l = function.max(
# level set of a square centred at (0.3,0.4)
0.15 - (abs(0.3 - x0) + abs(0.4 - x1)),
# level set of a circle centred at (0.7,0.6)
0.15 - ((0.7 - x0)**2 + (0.6 - x1)**2)**0.5,
)
# smooth heaviside of level set
u0 = 0.5 + 0.5 * function.tanh(nelems / 2 * l)
for n in log.range('timestep', round(tend / dt) + 1):
if n == 0:
# project initial condition on `basis`
w = domain.project(u0, onto=basis, geometry=geom, ischeme=ischeme)
else:
# time step
w = A.solve(B.matvec(w), constrain=cons)
# construct solution
u = basis.dot(w)
# plot
points, colors = domain.elem_eval([geom, u],
ischeme='bezier3',
separate=True)
with plot.PyPlot('temperature') as plt:
plt.title('t={:5.2f}'.format(n * dt))
plt.mesh(points, colors)
plt.colorbar()
plt.clim(0, 1)
def main(nelems: int, degree: int, reynolds: float):
'''
Driven cavity benchmark problem using compatible spaces.
.. arguments::
nelems [12]
Number of elements along edge.
degree [2]
Polynomial degree for velocity; the pressure space is one degree less.
reynolds [1000]
Reynolds number, taking the domain size as characteristic length.
'''
verts = numpy.linspace(0, 1, nelems + 1)
domain, geom = mesh.rectilinear([verts, verts])
ns = function.Namespace()
ns.x = geom
ns.Re = reynolds
ns.uxbasis, ns.uybasis, ns.pbasis, ns.lbasis = function.chain([
domain.basis('spline',
degree=(degree, degree - 1),
removedofs=((0, -1), None)),
domain.basis('spline',
degree=(degree - 1, degree),
removedofs=(None, (0, -1))),
domain.basis('spline', degree=degree - 1),
[1], # lagrange multiplier
])
ns.ubasis_ni = '<uxbasis_n, uybasis_n>_i'
ns.u_i = 'ubasis_ni ?lhs_n'
ns.p = 'pbasis_n ?lhs_n'
ns.l = 'lbasis_n ?lhs_n'
ns.stress_ij = '(u_i,j + u_j,i) / Re - p δ_ij'
ns.uwall = domain.boundary.indicator('top'), 0
ns.N = 5 * degree * nelems # nitsche constant based on element size = 1/nelems
ns.nitsche_ni = '(N ubasis_ni - (ubasis_ni,j + ubasis_nj,i) n_j) / Re'
res = domain.integral(
'(ubasis_ni,j stress_ij + pbasis_n (u_k,k + l) + lbasis_n p) d:x' @ ns,
degree=2 * degree)
res += domain.boundary.integral(
'(nitsche_ni (u_i - uwall_i) - ubasis_ni stress_ij n_j) d:x' @ ns,
degree=2 * degree)
with treelog.context('stokes'):
lhs0 = solver.solve_linear('lhs', res)
postprocess(domain, ns, lhs=lhs0)
res += domain.integral('ubasis_ni u_i,j u_j d:x' @ ns, degree=3 * degree)
with treelog.context('navierstokes'):
lhs1 = solver.newton('lhs', res, lhs0=lhs0).solve(tol=1e-10)
postprocess(domain, ns, lhs=lhs1)
return lhs0, lhs1
def __init__(self, physical, n, p):
""" __init__(self, physical, n, p)
Constructor for finite element object
:param physical : (width, height) of physical domain
:param n : (n1,n2), number of elements in computational domain
:param p : (p1,p2), polynomial degree of compuational discretization
"""
# create splipy object
splinesurf = splines.square() * physical
splinesurf.reparam((0, physical[0]), (0, physical[1]))
splinesurf.raise_order(p[0] - 1, p[1] - 1)
splinesurf.refine(n[0] - 1, n[1] - 1)
# create nutils mesh
domain, geom = mesh.rectilinear(splinesurf.knots())
basis = domain.basis('spline', degree=p)
# pre-compute all system matrices
derivs = function.outer(basis.grad(geom), basis.grad(geom))
laplace = derivs[:, :, 0] + derivs[:, :, 1]
A = domain.integrate(laplace, geometry=geom, ischeme='gauss3')
M = domain.integrate(function.outer(basis, basis),
geometry=geom,
ischeme='gauss3')
# print(M.toarray())
# pre-compute evaluation matrices
self.Nu = splinesurf.bases[0].evaluate(
np.linspace(splinesurf.start('u'), splinesurf.end('u'),
physical[0]))
self.Nv = splinesurf.bases[1].evaluate(
np.linspace(splinesurf.start('v'), splinesurf.end('v'),
physical[1]))
# store all nutils object as class variables
self.splinesurf = splinesurf
self.domain = domain
self.geom = geom
self.basis = basis
self.A = A.toscipy() * 1e2
self.M = M.toscipy()
self.u = np.matrix(np.zeros((A.shape[0], 1)))
self.b = np.matrix(np.zeros((A.shape[0], 1)))
self.n = np.array(n)
self.p = np.array(p)
self.physical = np.array(physical)
self.time = {
'add_smoke': 0,
'get_img': 0,
'stop_smoke': 0,
'diffuse': 0,
'solve': 0
}
def splipy_to_nutils(spline):
""" Returns nutils domain and geometry object for spline mapping given by the argument """
from nutils import mesh, function
domain, geom = mesh.rectilinear(spline.knots())
cp = controlpoints(spline)
basis = domain.basis('spline',
degree=degree(spline),
knotmultiplicities=multiplicities(spline))
geom = function.matmat(basis, cp)
#TODO: add correct behaviour for rational and/or periodic geometries
return domain, geom
def test_nutils_tensor():
domain, geom = mesh.rectilinear([[0, 1], [0, 1]])
basis = domain.basis('spline', degree=1)
itg = basis[:, _, _] * basis[_, :, _] * basis[_, _, :]
a = AffineIntegral(1, itg)
a.prop(domain=domain, geometry=geom, ischeme='gauss9')
a = a.cache_main(force=True)(None, {})
b = domain.integrate(itg * fn.J(geom), ischeme='gauss9')
np.testing.assert_almost_equal(a, b)
def navierstokes():
domain, geom = mesh.rectilinear([numpy.linspace(0, 1, 9)] * 2)
ubasis, pbasis = function.chain([
domain.basis('std', degree=2).vector(2),
domain.basis('std', degree=1),
])
dofs = function.DerivativeTarget([len(ubasis)])
u = ubasis.dot(dofs)
p = pbasis.dot(dofs)
viscosity = 1
inertia = model.Integral((ubasis * u).sum(-1),
domain=domain,
geometry=geom,
degree=5)
stokesres = model.Integral(viscosity * ubasis['ni,j'] *
(u['i,j'] + u['j,i']) - ubasis['nk,k'] * p +
pbasis['n'] * u['k,k'],
domain=domain,
geometry=geom,
degree=5)
residual = stokesres + model.Integral(ubasis['ni'] * u['i,j'] * u['j'],
domain=domain,
geometry=geom,
degree=5)
cons = domain.boundary['top,bottom'].project( [0,0], onto=ubasis, geometry=geom, ischeme='gauss2' ) \
| domain.boundary['left'].project( [geom[1]*(1-geom[1]),0], onto=ubasis, geometry=geom, ischeme='gauss2' )
lhs0 = model.solve_linear(dofs, residual=stokesres, constrain=cons)
for name in 'direct', 'newton', 'pseudotime':
@unittest(name=name, raises=name == 'direct' and model.ModelError)
def res():
tol = 1e-10
if name == 'direct':
lhs = model.solve_linear(dofs,
residual=residual,
constrain=cons)
elif name == 'newton':
lhs = model.newton(dofs,
residual=residual,
lhs0=lhs0,
freezedofs=cons.where).solve(tol=tol,
maxiter=2)
else:
lhs = model.pseudotime(dofs,
residual=residual,
lhs0=lhs0,
freezedofs=cons.where,
inertia=inertia,
timestep=1).solve(tol=tol, maxiter=3)
res = residual.replace(dofs, lhs).eval()
resnorm = numpy.linalg.norm(res[~cons.where])
assert resnorm < tol
def setUp(self):
super().setUp()
domain, geom = mesh.rectilinear([numpy.linspace(0,1,9)] * 2)
ubasis = domain.basis('std', degree=2).vector(2)
u = ubasis.dot(function.Argument('dofs', [len(ubasis)]))
Geom = geom * [1.1, 1] + u
self.cons = solver.minimize('dofs', domain.boundary['left,right'].integral((u**2).sum(0), degree=4), droptol=1e-15).solve()
self.boolcons = ~numpy.isnan(self.cons)
strain = .5 * (function.outer(Geom.grad(geom), axis=1).sum(0) - function.eye(2))
self.energy = domain.integral(((strain**2).sum([0,1]) + 20*(function.determinant(Geom.grad(geom))-1)**2)*function.J(geom), degree=6)
self.residual = self.energy.derivative('dofs')
self.tol = 1e-10
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 main(
nelems: 'number of elements' = 12,
lmbda: 'first lamé constant' = 1.,
mu: 'second lamé constant' = 1.,
degree: 'polynomial degree' = 2,
withplots: 'create plots' = True,
solvetol: 'solver tolerance' = 1e-10,
):
# construct mesh
verts = numpy.linspace(0, 1, nelems + 1)
domain, geom = mesh.rectilinear([verts, verts])
# create namespace
ns = function.Namespace(default_geometry_name='x0')
ns.x0 = geom
ns.basis = domain.basis('spline', degree=degree).vector(2)
ns.u_i = 'basis_ni ?lhs_n'
ns.x_i = 'x0_i + u_i'
ns.lmbda = lmbda
ns.mu = mu
ns.strain_ij = '(u_i,j + u_j,i) / 2'
ns.stress_ij = 'lmbda strain_kk δ_ij + 2 mu strain_ij'
# construct dirichlet boundary constraints
sqr = domain.boundary['left'].integral('u_k u_k' @ ns,
geometry=ns.x0,
degree=2)
sqr += domain.boundary['right'].integral('(u_0 - .5)^2' @ ns,
geometry=ns.x0,
degree=2)
cons = solver.optimize('lhs', sqr, droptol=1e-15)
# construct residual
res = domain.integral('basis_ni,j stress_ij' @ ns,
geometry=ns.x0,
degree=2)
# solve system and substitute the solution in the namespace
lhs = solver.solve_linear('lhs', res, constrain=cons)
ns |= dict(lhs=lhs)
# plot solution
if withplots:
points, colors = domain.elem_eval([ns.x, ns.stress[0, 1]],
ischeme='bezier3',
separate=True)
with plot.PyPlot('stress', ndigits=0) as plt:
plt.mesh(points, colors, tight=False)
plt.colorbar()
return lhs, cons
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 setUp(self):
super().setUp()
domain, geom = mesh.rectilinear([numpy.linspace(0,1,9)] * 2)
ubasis, pbasis = function.chain([
domain.basis('std', degree=2).vector(2),
domain.basis('std', degree=1),
])
dofs = function.Argument('dofs', [len(ubasis)])
u = ubasis.dot(dofs)
p = pbasis.dot(dofs)
viscosity = 1
self.inertia = domain.integral((ubasis * u).sum(-1), geometry=geom, degree=5)
stokesres = domain.integral(viscosity * (ubasis.grad(geom) * (u.grad(geom)+u.grad(geom).T)).sum([-1,-2]) - ubasis.div(geom) * p + pbasis * u.div(geom), geometry=geom, degree=5)
self.residual = stokesres + domain.integral((ubasis * (u.grad(geom) * u).sum(-1) * u).sum(-1), geometry=geom, degree=5)
self.cons = domain.boundary['top,bottom'].project([0,0], onto=ubasis, geometry=geom, ischeme='gauss2') \
| domain.boundary['left'].project([geom[1]*(1-geom[1]),0], onto=ubasis, geometry=geom, ischeme='gauss2')
self.lhs0 = solver.solve_linear('dofs', residual=stokesres, constrain=self.cons)
self.tol = 1e-10
def main(
nelems: 'number of elements' = 12,
lmbda: 'first lamé constant' = 1.,
mu: 'second lamé constant' = 1.,
degree: 'polynomial degree' = 2,
withplots: 'create plots' = True,
solvetol: 'solver tolerance' = 1e-10,
):
# construct mesh
verts = numpy.linspace(0, 1, nelems+1)
domain, geom = mesh.rectilinear([verts,verts])
# create namespace
ns = function.Namespace(default_geometry_name='x0')
ns.x0 = geom
ns.basis = domain.basis('spline', degree=degree).vector(2)
ns.u_i = 'basis_ni ?lhs_n'
ns.x_i = 'x0_i + u_i'
ns.lmbda = lmbda
ns.mu = mu
ns.strain_ij = '(u_i,j + u_j,i) / 2'
ns.stress_ij = 'lmbda strain_kk δ_ij + 2 mu strain_ij'
# construct dirichlet boundary constraints
sqr = domain.boundary['left'].integral('u_k u_k' @ ns, geometry=ns.x0, degree=2)
sqr += domain.boundary['right'].integral('(u_0 - .5)^2' @ ns, geometry=ns.x0, degree=2)
cons = solver.optimize('lhs', sqr, droptol=1e-15)
# construct residual
res = domain.integral('basis_ni,j stress_ij' @ ns, geometry=ns.x0, degree=2)
# solve system and substitute the solution in the namespace
lhs = solver.solve_linear('lhs', res, constrain=cons)
ns |= dict(lhs=lhs)
# plot solution
if withplots:
points, colors = domain.elem_eval([ns.x, ns.stress[0,1]], ischeme='bezier3', separate=True)
with plot.PyPlot('stress', ndigits=0) as plt:
plt.mesh(points, colors, tight=False)
plt.colorbar()
return lhs, cons
def laplace():
domain, geom = mesh.rectilinear( [8,8] )
basis = domain.basis( 'std', degree=1 )
cons = domain.boundary['left'].project( 0, onto=basis, geometry=geom, ischeme='gauss2' )
dofs = function.DerivativeTarget( [len(basis)] )
u = basis.dot( dofs )
residual = model.Integral( ( basis.grad(geom) * u.grad(geom) ).sum(-1), domain=domain, geometry=geom, degree=2 ) \
+ model.Integral( basis, domain=domain.boundary['top'], geometry=geom, degree=2 )
for name in 'direct', 'newton':
@unittest( name=name )
def res():
if name == 'direct':
lhs = model.solve_linear( dofs, residual=residual, constrain=cons )
else:
lhs = model.newton( dofs, residual=residual, lhs0=cons|0, freezedofs=cons.where ).solve( tol=1e-10, maxiter=0 )
res = residual.replace( dofs, lhs ).eval()
resnorm = numpy.linalg.norm( res[~cons.where] )
assert resnorm < 1e-13
def main(
nelems: 'number of elements' = 20,
degree: 'polynomial degree' = 1,
timescale: 'time scale (timestep=timescale/nelems)' = .5,
tol: 'solver tolerance' = 1e-5,
ndims: 'spatial dimension' = 1,
endtime: 'end time, 0 for no end time' = 0,
withplots: 'create plots' = True,
):
# construct mesh, basis
ns = function.Namespace()
domain, ns.x = mesh.rectilinear([numpy.linspace(0,1,nelems+1)]*ndims, periodic=range(ndims))
ns.basis = domain.basis('discont', degree=degree)
ns.u = 'basis_n ?lhs_n'
# construct initial condition (centered gaussian)
lhs0 = domain.project('exp(-?y_i ?y_i) | ?y_i = 5 (x_i - 0.5_i)' @ ns, onto=ns.basis, geometry=ns.x, degree=5)
# prepare residual
ns.f = '.5 u^2'
ns.C = 1
res = domain.integral('-basis_n,0 f' @ ns, geometry=ns.x, degree=5)
res += domain.interfaces.integral('-[basis_n] n_0 ({f} - .5 C [u] n_0)' @ ns, geometry=ns.x, degree=5)
inertia = domain.integral('basis_n u' @ ns, geometry=ns.x, degree=5)
# prepare plotting
makeplots = MakePlots(domain, video=withplots=='video') if withplots else lambda ns: None
# start time stepping
timestep = timescale/nelems
for itime, lhs in log.enumerate('timestep', solver.impliciteuler('lhs', res, inertia, timestep, lhs0, newtontol=tol)):
makeplots(ns | dict(lhs=lhs))
if endtime and itime * timestep >= endtime:
break
return res.eval(arguments=dict(lhs=lhs)), lhs
def main(
nelems: 'number of elements' = 20,
epsilon: 'epsilon, 0 for automatic (based on nelems)' = 0,
timestep: 'time step' = .01,
maxtime: 'end time' = 1.,
theta: 'contact angle (degrees)' = 90,
init: 'initial condition (random/bubbles)' = 'random',
withplots: 'create plots' = True,
):
mineps = 1./nelems
if not epsilon:
log.info('setting epsilon={}'.format(mineps))
epsilon = mineps
elif epsilon < mineps:
log.warning('epsilon under crititical threshold: {} < {}'.format(epsilon, mineps))
# create namespace
ns = function.Namespace()
ns.epsilon = epsilon
ns.ewall = .5 * numpy.cos( theta * numpy.pi / 180 )
# construct mesh
xnodes = ynodes = numpy.linspace(0,1,nelems+1)
domain, ns.x = mesh.rectilinear( [ xnodes, ynodes ] )
# prepare bases
ns.cbasis, ns.mubasis = function.chain([
domain.basis('spline', degree=2),
domain.basis('spline', degree=2)
])
# polulate namespace
ns.c = 'cbasis_n ?lhs_n'
ns.c0 = 'cbasis_n ?lhs0_n'
ns.mu = 'mubasis_n ?lhs_n'
ns.f = '(6 c0 - 2 c0^3 - 4 c) / epsilon^2'
# construct initial condition
if init == 'random':
numpy.random.seed(0)
lhs0 = numpy.random.normal(0, .5, ns.cbasis.shape)
elif init == 'bubbles':
R1 = .25
R2 = numpy.sqrt(.5) * R1 # area2 = .5 * area1
ns.cbubble1 = function.tanh((R1-function.norm2(ns.x-(.5+R2/numpy.sqrt(2)+.8*ns.epsilon)))/ns.epsilon)
ns.cbubble2 = function.tanh((R2-function.norm2(ns.x-(.5-R1/numpy.sqrt(2)-.8*ns.epsilon)))/ns.epsilon)
sqr = domain.integral('(c - cbubble1 - cbubble2 - 1)^2 + mu^2' @ ns, geometry=ns.x, degree=4)
lhs0 = solver.optimize('lhs', sqr)
else:
raise Exception( 'unknown init %r' % init )
# construct residual
res = domain.integral('epsilon^2 cbasis_n,k mu_,k + mubasis_n (mu + f) - mubasis_n,k c_,k' @ ns, geometry=ns.x, degree=4)
res -= domain.boundary.integral('mubasis_n ewall' @ ns, geometry=ns.x, degree=4)
inertia = domain.integral('cbasis_n c' @ ns, geometry=ns.x, degree=4)
# solve time dependent problem
nsteps = numeric.round(maxtime/timestep)
makeplots = MakePlots(domain, nsteps, ns) if withplots else lambda *args: None
for istep, lhs in log.enumerate('timestep', solver.impliciteuler('lhs', target0='lhs0', residual=res, inertia=inertia, timestep=timestep, lhs0=lhs0)):
makeplots(lhs)
if istep == nsteps:
break
return lhs0, lhs
def setUp(self):
super().setUp()
self.ns = function.Namespace()
self.domain, self.ns.geom = mesh.rectilinear([2,2])
self.ns.ubasis = self.domain.basis('std', degree=1)
def main(
nelems: 'number of elements' = 12,
viscosity: 'fluid viscosity' = 1e-2,
density: 'fluid density' = 1,
tol: 'solver tolerance' = 1e-12,
rotation: 'cylinder rotation speed' = 0,
timestep: 'time step' = 1/24,
maxradius: 'approximate domain size' = 25,
tmax: 'end time' = numpy.inf,
degree: 'polynomial degree' = 2,
figures: 'create figures' = True,
):
log.user('reynolds number: {:.1f}'.format(density / viscosity)) # based on unit length and velocity
# create namespace
ns = function.Namespace()
ns.uinf = 1, 0
ns.density = density
ns.viscosity = viscosity
# construct mesh
rscale = numpy.pi / nelems
melems = numpy.ceil(numpy.log(2*maxradius) / rscale).astype(int)
log.info('creating {}x{} mesh, outer radius {:.2f}'.format(melems, 2*nelems, .5*numpy.exp(rscale*melems)))
domain, x0 = mesh.rectilinear([range(melems+1),numpy.linspace(0,2*numpy.pi,2*nelems+1)], periodic=(1,))
rho, phi = x0
phi += 1e-3 # tiny nudge (0.057 deg) to break element symmetry
radius = .5 * function.exp(rscale * rho)
ns.x = radius * function.trigtangent(phi)
domain = domain.withboundary(inner='left', inflow=domain.boundary['right'].select(-ns.uinf.dotnorm(ns.x), ischeme='gauss1'))
# prepare bases (using piola transformation to maintain u/p compatibility)
J = ns.x.grad(x0)
detJ = function.determinant(J)
ns.unbasis, ns.utbasis, ns.pbasis = function.chain([ # compatible spaces using piola transformation
domain.basis('spline', degree=(degree+1,degree), removedofs=((0,),None))[:,_] * J[:,0] / detJ,
domain.basis('spline', degree=(degree,degree+1))[:,_] * J[:,1] / detJ,
domain.basis('spline', degree=degree) / detJ,
])
ns.ubasis_ni = 'unbasis_ni + utbasis_ni'
# populate namespace
ns.u_i = 'ubasis_ni ?lhs_n'
ns.p = 'pbasis_n ?lhs_n'
ns.sigma_ij = 'viscosity (u_i,j + u_j,i) - p δ_ij'
ns.hinner = 2 * numpy.pi / nelems
ns.c = 5 * (degree+1) / ns.hinner
ns.nietzsche_ni = 'viscosity (c ubasis_ni - (ubasis_ni,j + ubasis_nj,i) n_j)'
ns.ucyl = -.5 * rotation * function.trignormal(phi)
# create residual vector components
res = domain.integral('ubasis_ni,j sigma_ij + pbasis_n u_k,k' @ ns, geometry=ns.x, degree=2*(degree+1))
res += domain.boundary['inner'].integral('nietzsche_ni (u_i - ucyl_i)' @ ns, geometry=ns.x, degree=2*(degree+1))
oseen = domain.integral('density ubasis_ni u_i,j uinf_j' @ ns, geometry=ns.x, degree=2*(degree+1))
convec = domain.integral('density ubasis_ni u_i,j u_j' @ ns, geometry=ns.x, degree=3*(degree+1))
inertia = domain.integral('density ubasis_ni u_i' @ ns, geometry=ns.x, degree=2*(degree+1))
# constrain full velocity vector at inflow
sqr = domain.boundary['inflow'].integral('(u_i - uinf_i) (u_i - uinf_i)' @ ns, geometry=ns.x, degree=9)
cons = solver.optimize('lhs', sqr, droptol=1e-15)
# solve unsteady navier-stokes equations, starting from stationary oseen flow
lhs0 = solver.solve_linear('lhs', res+oseen, constrain=cons)
makeplots = MakePlots(domain, ns, timestep=timestep, rotation=rotation) if figures else lambda *args: None
for istep, lhs in log.enumerate('timestep', solver.impliciteuler('lhs', residual=res+convec, inertia=inertia, lhs0=lhs0, timestep=timestep, constrain=cons, newtontol=1e-10)):
makeplots(lhs)
if istep * timestep >= tmax:
break
return lhs0, lhs
def main(
L: 'domain size' = 4.,
R: 'hole radius' = 1.,
E: "young's modulus" = 1e5,
nu: "poisson's ratio" = 0.3,
T: 'far field traction' = 10,
nr: 'number of h-refinements' = 2,
figures: 'create figures' = True,
):
ns = function.Namespace()
ns.lmbda = E*nu/(1-nu**2)
ns.mu = .5*E/(1+nu)
# create the coarsest level parameter domain
domain0, geometry = mesh.rectilinear( [1,2] )
# create the second-order B-spline basis over the coarsest domain
ns.bsplinebasis = domain0.basis('spline', degree=2)
ns.controlweights = 1,.5+.5/2**.5,.5+.5/2**.5,1,1,1,1,1,1,1,1,1
ns.weightfunc = 'bsplinebasis_n controlweights_n'
ns.nurbsbasis = ns.bsplinebasis * ns.controlweights / ns.weightfunc
# create the isogeometric map
ns.controlpoints = [0,R],[R*(1-2**.5),R],[-R,R*(2**.5-1)],[-R,0],[0,.5*(R+L)],[-.15*(R+L),.5*(R+L)],[-.5*(R+L),.15*(R*L)],[-.5*(R+L),0],[0,L],[-L,L],[-L,L],[-L,0]
ns.x_i = 'nurbsbasis_n controlpoints_ni'
# create the computational domain by h-refinement
domain = domain0.refine(nr)
# create the second-order B-spline basis over the refined domain
ns.bsplinebasis = domain.basis('spline', degree=2)
sqr = domain.integral('(bsplinebasis_n ?lhs_n - weightfunc)^2' @ ns, geometry=ns.x, degree=9)
ns.controlweights = solver.optimize('lhs', sqr)
ns.nurbsbasis = ns.bsplinebasis * ns.controlweights / ns.weightfunc
# prepare the displacement field
ns.ubasis = ns.nurbsbasis.vector(2)
ns.u_i = 'ubasis_ni ?lhs_n'
ns.strain_ij = '(u_i,j + u_j,i) / 2'
ns.stress_ij = 'lmbda strain_kk δ_ij + 2 mu strain_ij'
# construct the exact solution
ns.r2 = 'x_k x_k'
ns.R2 = R**2
ns.T = T
ns.k = (3-nu) / (1+nu) # plane stress parameter
ns.uexact_i = '''(T / 4 mu) <x_0 ((k + 1) / 2 + (1 + k) R2 / r2 + (1 - R2 / r2) (x_0^2 - 3 x_1^2) R2 / r2^2),
x_1 ((k - 3) / 2 + (1 - k) R2 / r2 + (1 - R2 / r2) (3 x_0^2 - x_1^2) R2 / r2^2)>_i'''
ns.strainexact_ij = '(uexact_i,j + uexact_j,i) / 2'
ns.stressexact_ij = 'lmbda strainexact_kk δ_ij + 2 mu strainexact_ij'
# define the linear and bilinear forms
res = domain.integral('ubasis_ni,j stress_ij' @ ns, geometry=ns.x, degree=9)
res -= domain.boundary['right'].integral('ubasis_ni stressexact_ij n_j' @ ns, geometry=ns.x, degree=9)
# compute the constraints vector for the symmetry conditions
sqr = domain.boundary['top,bottom'].integral('(u_i n_i)^2' @ ns, degree=9)
cons = solver.optimize('lhs', sqr, droptol=1e-15)
# solve the system of equations
lhs = solver.solve_linear('lhs', res, constrain=cons)
ns = ns(lhs=lhs)
# post-processing
if figures:
geom, stressxx = domain.simplex.elem_eval([ns.x, 'stress_00' @ ns], ischeme='bezier8', separate=True)
with plot.PyPlot( 'solution', index=nr ) as plt:
plt.mesh( geom, stressxx )
plt.colorbar()
# compute the L2-norm of the error in the stress
err = domain.integrate('(?dstress_ij ?dstress_ij)(dstress_ij = stress_ij - stressexact_ij)' @ ns, geometry=ns.x, ischeme='gauss9')**.5
# compute the mesh parameter (maximum physical distance between knots)
hmax = max(numpy.linalg.norm(v[:,numpy.newaxis]-v, axis=2).max() for v in domain.elem_eval(ns.x, ischeme='bezier2', separate=True))
return err, hmax
