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Using sign and abs on variables

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Hello,

I typed the following into a boundary condition:

-sign(solid.u_tX)*beta*(abs(solid.u_tX))^m

where beta and m are constants that I defined, and solid.u_tX is the x-velocity. However, when I tried to solve, COMSOL could ot find consistent initial values. If I remove the sign and abs functions (and set m = 1), then COMSOL will solve. Is there a way to get this to work with the sign and abs functions?

Thanks,
Henry

1 Reply Last Post 2011年6月1日 GMT-4 00:46
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2011年6月1日 GMT-4 00:46
Hi

sign and abs functions are know to have discontinuities, perhaps if you check that you work inone 1 quadrant, or that you smoothen the transitions it would solve better

--
Good luck
Ivar
Hi sign and abs functions are know to have discontinuities, perhaps if you check that you work inone 1 quadrant, or that you smoothen the transitions it would solve better -- Good luck Ivar

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