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Sign convention for gradients in axisymmetric models

Posted Jul 18, 2011, 8:14 p.m. EDT Low-Frequency Electromagnetics Version 4.2 0 Replies

William Woodruff
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I am modeling electrical currents in boreholes using the electrical currents AC/DC module in Comsol 4.2. I have built two similar axisymmetric models differing only in the placement of the axis of symmetry (i.e., the domains correspond r<=0 for model A, and r>=0 for model B). The external current density is defined as a function of a radial pressure differential, Je( grad[p(r)] ), such that the respective pressure gradient in model A is opposite in sign to that of model B.

The result is that the respective electrical fields are equal in magnitude, but opposite in sign. This must be related to the geometry of the problem; however, if the axisymmetric solver is integrating over theta, there should be no discrepancy as the problems are mirror images of one another. What is the source of this error, and how do I properly account for the sign of the gradients?

--Bill
0 Replies Last Post Jul 18, 2011, 8:14 p.m. EDT
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