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Failed to Evaluate Variable Jacobian

Posted Jan 13, 2012, 12:04 p.m. EST Fluid & Heat, Microfluidics, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.2a 1 Reply

COMSOL user2

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Hello,

I'm using "Laminar Flow" and "Transport of Diluted Species".

After I successfully simulated a few times, I just added "Rectangle" variable to inlet. I typed in the inlet as "10*rect1(t[1/s])".

After that I get the same message like this.

Failed to evaluate variable Jacobian.
- Variable: t
- Geometry: 1
- Boundary: 1 7 13 19 25

Please let me know if anyone knows how to solve it.

Thanks.

1 Reply Last Post Jan 13, 2012, 5:06 p.m. EST

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago

Hi

probably the rise time of your rectangle is too rapid, compared to the time stepping, and perhaps mesh density, particularly if you have diffusion with a rapid step.

Time stepping, mesh size and diffusivity must match to a certain degree, check your doc, or classical PDE textbooks on diffusion

--
Good luck
Ivar

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Failed to Evaluate Variable Jacobian

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