The lower is a constant obstacle psi =-0.03

I have the plot using freefem++ 

On Thu, Jul 17, 2025 at 4:02 PM Matthew Knepley <knepley@gmail.com> wrote:

On Thu, Jul 17, 2025 at 10:49 AM Smail Merabet <merabetsmail@gmail.com> wrote:

Dear Matthew,

thanks for reply, I tried this:

psi = Constant(-0.03)

# Create the full function in mixed space

obs = Function(Vh, name="Obstacle")

upp = Function(Vh, name="Upper")

obs_sub1 = obs.sub(1)

upp_sub1 = upp.sub(1)

# Interpolate into the subfunctions

obs_sub1.interpolate(conditional(lt(psi, 0), 0, psi))

I do not understand the Firedrake side, but did you plot your lower bound? I have no idea what conditional gives back.

  Thanks,

     Matt

 

upp_sub1.interpolate(Constant(1e10))

But the result doesn't satisfy the constraint $w \geq  \psi$

Many Thanks

On Thu, Jul 17, 2025 at 1:22 PM Matthew Knepley <knepley@gmail.com> wrote:

On Thu, Jul 17, 2025 at 7:52 AM Smail Merabet <merabetsmail@gmail.com> wrote:

Dear firedrake users, I try to solve a variational inequality using snes-firedrake.

I have two unknown functions say (theta,w)

so the functionspace is Vh = MixedFunctionSpace([Th,Wh]) 

 where

Th = FunctionSpace(mesh, "Lagrange", 1)
Wh = FunctionSpace(mesh, "Lagrange", 2)

the inequality constraint concerns only $w$

I set : 

obstacle = Function(Vh.sub(1)).interpolate((Constant(-0.03)))

upper = Function(Vh.sub(1)).interpolate(Constant(1e10))

The SNES is operating on the full space, but you have interpolated constraints on the subspace. You have to inject those to full space vectors before setting the bounds.

 Thanks,

    Matt

 

solver.solve(bounds=(obstacle, upper)) 

but this line causes the following error:

File "/Users/maths/Desktop/Firedrake/VI/Timoshenko-obs.py", line 64, in <module>
    solver.solve(bounds=(obstacle, upper))
  File "petsc4py/PETSc/Log.pyx", line 188, in petsc4py.PETSc.Log.EventDecorator.decorator.wrapped_func
  File "petsc4py/PETSc/Log.pyx", line 189, in petsc4py.PETSc.Log.EventDecorator.decorator.wrapped_func
  File "/Users/maths/firedrake/src/firedrake/firedrake/adjoint_utils/variational_solver.py", line 89, in wrapper
    out = solve(self, **kwargs)
  File "/Users/maths/firedrake/src/firedrake/firedrake/variational_solver.py", line 312, in solve
    self.snes.setVariableBounds(lb, ub)
  File "petsc4py/PETSc/SNES.pyx", line 1978, in petsc4py.PETSc.SNES.setVariableBounds
petsc4py.PETSc.Error: error code 75
[0] SNESVISetVariableBounds() at /Users/maths/firedrake/src/petsc/src/snes/impls/vi/vi.c:424
[0] SNESVISetVariableBounds_VI() at /Users/maths/firedrake/src/petsc/src/snes/impls/vi/vi.c:443
[0] Arguments are incompatible

[0] Incompatible vector lengths lower bound = 201 solution vector = 302 

Hope that one can help me ...

Best regards.

Smail. 

On Fri, Apr 11, 2025 at 9:11 AM Smail Merabet <merabetsmail@gmail.com> wrote:

Dear firedrake users, 

I try to solve a fourth-order 1d nonlinear problem using the Hermite element in firedrake.

The functional space for the weak solution is:

$$\mathcal{H}\times \mathcal{H}/times H^{2}_{0} $$ 

where,

$$
\mathcal{H} = \left\lbrace f\in H^2([0,\ell]), \; f(0)=0, \; f'(0)=0 \right\rbrace.
$$ 

I can't impose the boundary conditions correctly. When I compile the code, I get the following error: 

 FiniteElement('Hermite', interval, 3), name=None, index=1, component=None), IndexedProxyFunctionSpace(<firedrake.mesh.MeshTopology object at 0x125a2ce80>, FiniteElement('Hermite', interval, 3), name=None, index=2, component=None), name='None_None_None'), Mesh(VectorElement(FiniteElement('Lagrange', interval, 1), dim=1), 0)), 9) defined on incompatible FunctionSpace!

Note the same problem was implemented using FEniCS with C0-interior penalty method, in the reference (sec. 3 eq 3.12-3.13): 

Enhanced models for the nonlinear bending of planar rods: localization phenomena and multistability
by:
Matteo Brunetti , Antonino Favata  and Stefano Vidoli.

I attached the codes to this email.

Thanks in advance

Smail MERABET

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--

What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/

--

What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/