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How to start and stop injection?

Posted Jan 31, 2011, 3:36 a.m. EST Fluid & Heat, Materials, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 3.5a 1 Reply

Johanna Smaczny
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Hi. I am using PDE general mode to simulate multiphase flow. My water injection is controlled by a boundary condition with a specified rate [m/s]. Now my injection starts from time step 0. How can I change the beginning and end of my injection time? inject *(t<100)???

Thanks and regards,
Johanna
1 Reply Last Post Jan 31, 2011, 8:21 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 31, 2011, 8:21 a.m. EST
Hi

A bolean operator is OK, but it gives a step, that has no derivative, so it's better (and the convergence is improved, if not made only possible, when you use a Heaviside function to smoothen the start and stop edges.
This has been discussed several times, and is included by default in v4 on the built in step, ramp, and pulse functions

--
Good luck
Ivar
Hi A bolean operator is OK, but it gives a step, that has no derivative, so it's better (and the convergence is improved, if not made only possible, when you use a Heaviside function to smoothen the start and stop edges. This has been discussed several times, and is included by default in v4 on the built in step, ramp, and pulse functions -- Good luck Ivar

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