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how to get a value of dependent varible with time at boundaries?

Posted 16 gen 2011, 12:00 GMT-5 Parameters, Variables, & Functions Version 3.5a 4 Replies

GaneshM Battery Modelling
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Hi..

I need to get a value of dependent variable w.r.t time at boundaries . How can I write the expression for it?

for example, in 1D phi1 and phi2 are dependent variables and function of both(x,t) in subdomain 1 containing 2 boundaries.

I have to get the values of phi1 at boundary 1 with function of time. Similarly, phi2 at boundary 2 with function of time.

How to define V_cell= phi1( at boundary 1)-phi2(at boundary 2) at each time ?


thanks

regards
Ganesh

4 Replies Last Post 21 gen 2011, 10:54 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 16 gen 2011, 12:28 GMT-5
Hi

check the KB on the main site, ther are a few entries on time derivatives therin, I believe you should get your reply from there ;)

And many things of V4 are still applicable for 3.5a
--
Good luck
Ivar
Hi check the KB on the main site, ther are a few entries on time derivatives therin, I believe you should get your reply from there ;) And many things of V4 are still applicable for 3.5a -- Good luck Ivar
GaneshM Battery Modelling
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Posted: 1 decade ago 21 gen 2011, 03:36 GMT-5
Hi Ivar,

I have tried to get the values of dependent variables wit time at boundaries using boundary integration variables.

I have defined phi100 = phi1 at boundary 1
and phi201 = phi2 at boundary 2 in boundary integration variables


will they give the values of dependent variables at boundaries each time?

is this the correct way to get the values at each time?

thanks

ganesh
Hi Ivar, I have tried to get the values of dependent variables wit time at boundaries using boundary integration variables. I have defined phi100 = phi1 at boundary 1 and phi201 = phi2 at boundary 2 in boundary integration variables will they give the values of dependent variables at boundaries each time? is this the correct way to get the values at each time? thanks ganesh
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 21 gen 2011, 09:12 GMT-5
Hi

If you do an integration over a boundary (typically a 2D surface in 3D mode or a line/edge in 2D mode) then you are getting the integrated (summed) value over each element *dx*dy (2D) or times dx (1D). So a heat Flux Q[W/m^2], in 3D gives you. Note: COMSOL is integrating by "advanced" summation with loca higher order polynomial fitting.

Q_tot [W] = integration_overboundary of ( Q[W/m^2] *dx*dy )

If you have done a parametric saweep or a time series (transient analysis), when you plot this you get the Q_tot versus time or Parameter values

--
Good luck
Ivar
Hi If you do an integration over a boundary (typically a 2D surface in 3D mode or a line/edge in 2D mode) then you are getting the integrated (summed) value over each element *dx*dy (2D) or times dx (1D). So a heat Flux Q[W/m^2], in 3D gives you. Note: COMSOL is integrating by "advanced" summation with loca higher order polynomial fitting. Q_tot [W] = integration_overboundary of ( Q[W/m^2] *dx*dy ) If you have done a parametric saweep or a time series (transient analysis), when you plot this you get the Q_tot versus time or Parameter values -- Good luck Ivar
GaneshM Battery Modelling
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Posted: 1 decade ago 21 gen 2011, 10:54 GMT-5
Hi.. thanks for the reply..

I used this boundary integration in 1D geometry. I think it will consider the value at that point (1D)on boundary.

so, it represents the value of phi1 at that point at each time. isn't it?



thanks
ganesh
Hi.. thanks for the reply.. I used this boundary integration in 1D geometry. I think it will consider the value at that point (1D)on boundary. so, it represents the value of phi1 at that point at each time. isn't it? thanks ganesh

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