Obtain the vector component from the GirdFunction in HDiv space

[Liu0813]

Hi, everyone,
I want to modify the miniapp Joule and solve a 2d axisymmetric model. However, I encountered some problems about the heat conduction equation. In this miniapp, the heat conduction equation is solved using mixed finite element method, i.e. the temperature flux is defined in HDiv space, and the temperature is defined in L2 space. A simple method of solving axisymmetric model is to add a source term Fr/r in 2d heat conduction equation, that is

Thus, I have to obtain the Fr component. But for HDiv space, the function ProjectCoefficient doesn't work. So I hope to know how to project the r-component of temperature flux to a new GridFunction defined in L2 space.

[tzanio]

If I understand correctly, you'd like to compute say the x-component of an H(div) field F in 2D (in your notation r=x).

You can do that by projecting the continuous coefficient (1,0) to the RT space and then performing dots product with F in each degree of freedom.

Does this make sense?
Tzanio

[Liu0813]

Thanks for your reply. The method you provided is helpful.

[tzanio]

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