Hey there!

I am writing to ask for some help/advice.

I am trying to implement the 2D lid-driven cavity problem in the stream-function formulation.

Follows a minimal working example of what I coded until now:

```
from fenics import *
##############################################################################
## PDE Parameters Definition
n = 32
Re= 100
nu = 1.0/Re
# Load mesh
mesh = UnitSquareMesh(n,n)
V = FunctionSpace(mesh,'CG',2)
## Boundary Conditions
def boundary(x, on_boundary):
return on_boundary
## Homogeneus Boundary Conditions
bc0 = DirichletBC(V, Constant(0.0), boundary)
## Defining PDE
psi = TrialFunction(V)
phi = TestFunction(V)
FunLhs = nu*div(grad(psi))*div(grad(phi))*dx+\
div(grad(psi))*(grad(psi)[1]*grad(phi)[0]-grad(psi)[0]*grad(phi)[1])*dx
'''
```