How to check if a Function/TrialFunction/TestFunction is a 2D or 3D vector field


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4 months ago by
I am interested in computing vorticity (i.e. the curl of a velocity field). Because the cross product is not defined in 2D, you cannot use

omega = curl(u)​

for 2D problems. Instead you could do

omega = u[1].dx(0) - u[0].dx(1)​

Is there a simple way to check if u is a 2D or 3D vector field? I want to define a function like this

def vorticity(u):
    d = ???
    if d == 2:
        return u[1].dx(0) - u[0].dx(1)
    elif d == 3:
        return curl(u)​
Community: FEniCS Project
curl seems to be already implemented correctly for 2d also. You dont need to check the dimension. See the Fenics book, Chapter 17.
written 4 months ago by Praveen C  

1 Answer


4
4 months ago by
Hi, you may query u.ufl_shape[0] to get the required value for d.
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