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solute injection-advection dispersion equation

Posted May 14, 2011, 8:24 a.m. EDT Porous Media Flow, Studies & Solvers Version 4.0a 2 Replies

Ben Aballah Ismail
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Hi everyone, i am solving the 1d advection dispersion equation, i am asking how to insert a boundary condition at the top of a soil column: it is an injection of a solute flux (NaCl) every 30min. i tried to introduce a periodic function but in vain. Please help.
2 Replies Last Post May 15, 2011, 11:49 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago May 14, 2011, 1:20 p.m. EDT
Hi

not easy to understand like that what is the true issue you have, is it how to make a periodic function (I would propose to use the rectangular pulse, as it has continuous smooth transitions, and modulate it with a "modulo" mod(t[1/s],Periode)

But then you might also have an issue with the solver settings, as the default "automatic" solver is not tailored fo repetitive changes in the BC, you should give the time steps, and impose a "strict" or an "intermediate" time stepping to ensure that the solver is not skipping over some of your NaCl injection pulses

--
Good luck
Ivar
Hi not easy to understand like that what is the true issue you have, is it how to make a periodic function (I would propose to use the rectangular pulse, as it has continuous smooth transitions, and modulate it with a "modulo" mod(t[1/s],Periode) But then you might also have an issue with the solver settings, as the default "automatic" solver is not tailored fo repetitive changes in the BC, you should give the time steps, and impose a "strict" or an "intermediate" time stepping to ensure that the solver is not skipping over some of your NaCl injection pulses -- Good luck Ivar
Ben Aballah Ismail
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Posted: 1 decade ago May 15, 2011, 11:49 a.m. EDT
Thank you for the answer,

the boudary condition that I want to introduce is a crenel function.
I tried to do that but only one pulse is detected, i am not sure that I used the "mod" properly please would you like to tell me how to use it exactally.

Thanks
Thank you for the answer, the boudary condition that I want to introduce is a crenel function. I tried to do that but only one pulse is detected, i am not sure that I used the "mod" properly please would you like to tell me how to use it exactally. Thanks

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