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Divergence of gradient of a variable calculation
Posted 10.05.2012, 07:04 GMT-4 Chemical Reaction Engineering, Modeling Tools & Definitions, Parameters, Variables, & Functions, Results & Visualization, Studies & Solvers Version 4.0a 2 Replies
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I need to calculate, in the post-processing stage, the divergence of the gradient (it is the laplacian) of a known variable, in a specified volume.
May you help me, please?
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pls do not call us "support" we are here on the user forum, we are all users, we can give tips and tricks and our ideas, true "support" is via the official COMSOL channel ;)
this said, some ideas yes: what about studying the internal COMSOl variables (turn ibn the equation view in the preferences) and locate the variables and their derivatives, so if you solve to T the temperature, then mostly you will find Tx Ty Tz and Txx first and second derivatives. You have also the d(,) operator.
One thing you need to have high order discretization function to get higher order derivatives, and sometimes your values are already the derivatives of the true dependet variables (e.g. often in ACDC). COMSOL provides most 1st and 2nd derivatives of the dependent variables, but the 2nd derivatives might be vera rough and have steps, then its worth to higher the order of the discretization, but you need then more time and RAM to solve
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Good luck
Ivar
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