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Mathematical Particle tracing - resintence force

Posted Oct 24, 2012, 10:06 a.m. EDT Charged Particle Tracing, Particle Tracing for Fluid Flow 2 Replies

Ciprian Sporea
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Hi!

I'm trying to compute some trajectories using Comsol Math. Particle Tracing in the Newtonian formulation for some force which is of the form:
F=F1+F2
where F1 is proportional with the dielectrophoresis force
and F2 is a drag force proportional with the velocity.

my question is: haw do I introduce a time derivative in Math PT? to simulate a force proportional with velocity or haw do I introduce a velocity term in the force?

I've tried something like F1=2*d(x,t) but seams to not work.

Can anyone please help me?
Thanks :)

Ciprian
2 Replies Last Post Oct 24, 2012, 1:37 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Oct 24, 2012, 1:26 p.m. EDT
Hi

by default, if F1 is a dependent variable, normally COMSOL defines the time derivative as F1t and 2nd as F1tt
Check the equations

--
Good luck
Ivar
Hi by default, if F1 is a dependent variable, normally COMSOL defines the time derivative as F1t and 2nd as F1tt Check the equations -- Good luck Ivar
Daniel Smith COMSOL Employee

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Posted: 1 decade ago Oct 24, 2012, 1:37 p.m. EDT
Hi, in the "Particle Tracing for Fluid Flow" interface, available in the "Fluid Flow" section of the "Add Physics" wizard there are predefined features available for both the dielectrophoretic and drag forces. I recommend you use this interface, instead of the "Mathematical Particle Tracing" interface.
Hi, in the "Particle Tracing for Fluid Flow" interface, available in the "Fluid Flow" section of the "Add Physics" wizard there are predefined features available for both the dielectrophoretic and drag forces. I recommend you use this interface, instead of the "Mathematical Particle Tracing" interface.

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