I’m trying to solve the stokes equation with Pure Neumann boundary conditions or Traction boundary conditions at the boundaries.
This problem is singular and similiar to (https://fenicsproject.org/olddocs/dolfin/1.3.0/python/demo/documented/singular-poisson/python/documentation.html#) because the velocity field and the pressure field are not determined up to a constant .
V = VectorFunctionSpace(mesh,‘P’, 1)
element = MixedElement([p_element, v_element])
a = inner(grad(u), grad(v))df.dx + div(v)pdf.dx + qdiv(u)*df.dx
- Can someone help me with how to remove the null space of the Matrix (a), such that i can eliminate constant velocity and pressure solutions ? similiar to (https://fenicsproject.org/qa/4121/help-parallelising-space-method-eliminating-rigid-motion/) .
- For the elasticity problem however there is only one function space. How can one do this procedure for both the pressure and the velocity?