Dear all -- I am using fipy to solve a series of fluid dynamics problems. As part of this, I need to compute a stream function Psi from the vorticity of flow omega=V_x-U_y. U and V are calculated from the gradient of the solution to another set of elliptic equations, and are available on the same mesh as Psi will be calculated on.
The equation relating the stream function Psi to the vorticity omega is \Del^2 Psi = omega And the boundary conditions on Psi are that the gradient normal to the boundary is equal to the flow parallel to the boundary. All very standard. I calculate velocities U and V from the gradient of another variable (a pressure like term). My question is this: which of the routines that calculate the gradient of a fipy variable on the faces is most consistent with how the normal derivative is specified on the boundary? Which of .faceGrad() or faceGradAverage() is most consistent with how the gradient is implemented in Psi.faceGrad.constrain()? or some other gradient calculation? I ask because .faceGrad() does not seem to calculate the gradient on the boundary faces... Thanks, Jamie Pringle Director Ocean Process Analysis Laboratory in the Insitute for Earth, Ocean and Space Associate Professor of Earth Sciences University of New Hampshire http://oxbow.sr.unh.edu
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