factor 1/nu in K_p

[nschloe]

The documentation says that the operator is approximated by It's not immediately obvious why there should be a factor 1 / nu in K_p. Is this correct? If yes, it probably warrants a little more explanation.

[blechta]

Well,

X^{-1} = ( -\nu \Delta + \mathbf{v} \cdot \nabla ) ( - \Delta )^{-1}
       = \nu ( I + \nu^{-1} \mathbf{v} \cdot \nabla ( -\Delta )^{-1} )

When you add at the appropriate place the mass matrix solve, which is the Riesz map from (L^2)^* to L^2 and is customarily not written explicitly in infinite-dimensional formulas, you get the matrix formula.

I agree that the documentation could be more clear about that.