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Trying to fix the "Inconsistent Units" problem
Posted Jan 10, 2019, 12:50 a.m. EST Low-Frequency Electromagnetics, MEMS & Nanotechnology, MEMS & Piezoelectric Devices Version 5.3a 1 Reply
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Hi, I'm trying to simulate the Fitzhugh-Nagumo model of neurons on COMSOL 5.3a, exactly as it was done in the article "3D-Simulation of Action Potential Propagation in a Squid Giant Axon" by Appali et al. I'm trying to put in the equation for numerical flux for Equation 1 (Equation 4 in the article) as shown below:
In which I assumed the upper triangle operator is the Laplacian, hence I put in the following in the General Form PDE Interface: u1xx+u1yy+u1zz+(alpha-u1)(u1-1)u1-u2+I
& I get Inconsistent Units problem. I set the units for u1 & u2 to be Volts (V).
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Hello Yuen,
Indeed, the formula you give is not consistent: the laplacian of u has dimensions of voltage divided by length squared, the second term has dimensions of voltage cubed (well, kinda: the second part of it substracts a scalar from a voltage) and the remaining terms have dimensions of voltage.
See this other thread for a bit more of a discussion on when you can safely ignore such warnings. Best regards,
Jeff
-------------------Jeff Hiller