How to measure pointwise error?

[smyrback]

Hi,

I’m using a cut finite element method for solving Stokes equations. I want to investigate the pointwise divergence of the velocity solution. In another library, I do this by iterating over all quadrature points (both on cut elements, noncut elements, and on element faces) and taking the maximum value of the divergence of the solution. Can something like this be done in ngsxfem?

[schruste]

Hi,

Take a look at this answer:

Ngsxfem Sampling Points Along Zero Level Set

Hey Shahan, I think it should be possible by using the interpolation points (provided by the integration function). The code would be something like: IntPoints = [] Integrate(levelset_domain = { "levelset" : lsetp1, "domain_type" : IF}, cf=0, mesh = mesh, ip_container = IntPoints, order=1) Now, the list IntPoints contains all used integration points are located on the zero level. By increasing the order you can increase the number of returned points. Best wishes, Paul

With that “feature” you can at least evaluate the maximum over the set of integration points.

Best,
Christoph