since I’m pretty new to Fenics I’m trying to figure out subdomains and Neumann Conditions.
Doing so I came across a strange effect in my Plot of a pretty basic Laplace equation.
The above plot results from the following example code
from dolfin import * from fenics import * from mshr import * import matplotlib.pyplot as plt g = Constant(5000320.0) space = Rectangle(Point(0,0), Point(1,1)) cylinder = Circle(Point(0.5, 0.5), 0.01) domain = space - cylinder mesh = generate_mesh(domain, 100 ) Q = FunctionSpace(mesh, 'Lagrange', 1) u = TrialFunction(Q) v = TestFunction(Q) aL = inner(grad(u), grad(v))*dx LL = g * v *ds u = Function(Q) solve(aL == LL, u) plot(mesh, title='the mesh') plt.show() Laplace=plot(u, title='show laplace') plt.colorbar(Laplace) plt.show()
As you can see there are these white spots in the plot and I have no idea what they are from as the mesh covers these areas and there are no error messages.
So what are they and from what do they result?
Addtionally the Neumann condition doesnt seem to be applied right since the results seem to be uneven even with them applied to all edges.
As a note
g is intentionally so large, both to show the effect and for the program this all stems from.
Thank you for your help!