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Problems with STEP FUNCTION
Posted May 18, 2016, 5:06 p.m. EDT Fluid & Heat, Computational Fluid Dynamics (CFD), Materials, Studies & Solvers Version 5.2 2 Replies
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Hi everybody,
I have an inlet in a water reactor working in the following way: 10 s on, 80 s off, 10 s on, 80 s off....
-Fist of all, I have built a PIECEWISE (pw1) function (0<t<10 = 1, 10<t<90 = 0)
-Then, using this piecewise function I have built an ANALYTIC function (an1) with a periodic extension 0-90, and plot parameters 0-900. When I plot it, everything is OK.
- Finally I have created a variable for the inlet velocity: 0.265[m/s]*an1(t[1/s])
When I compute my model, the inlet works only in the first 10 seconds, but after 90 seconds it doesn´t start working agains as an inlet, there is no velocity.
Why????
Thank you so much
I have an inlet in a water reactor working in the following way: 10 s on, 80 s off, 10 s on, 80 s off....
-Fist of all, I have built a PIECEWISE (pw1) function (0<t<10 = 1, 10<t<90 = 0)
-Then, using this piecewise function I have built an ANALYTIC function (an1) with a periodic extension 0-90, and plot parameters 0-900. When I plot it, everything is OK.
- Finally I have created a variable for the inlet velocity: 0.265[m/s]*an1(t[1/s])
When I compute my model, the inlet works only in the first 10 seconds, but after 90 seconds it doesn´t start working agains as an inlet, there is no velocity.
Why????
Thank you so much
2 Replies Last Post May 20, 2016, 11:00 a.m. EDT
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Posted:
8 years ago
Hi
are you sure you have set the time stepping to "intermediate" such that the solver is not "jumping" over the repetitive peaks ?
By default the solver settings for time series is in "diffusion problem modus" expecting an exponential convergence.
When you define periodic input flux excitations you need to change that setting. There are several threads about that around too. Its far down in the solver tree
--
Good luck
Ivar
are you sure you have set the time stepping to "intermediate" such that the solver is not "jumping" over the repetitive peaks ?
By default the solver settings for time series is in "diffusion problem modus" expecting an exponential convergence.
When you define periodic input flux excitations you need to change that setting. There are several threads about that around too. Its far down in the solver tree
--
Good luck
Ivar
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Posted:
8 years ago
Dear Ricardo,
To ensure that solver captures such changes in the boundary conditions, it would be appropriate to use the Events interface. See, for example:
www.comsol.com/blogs/modeling-a-periodic-heat-load/
Best Regards,
To ensure that solver captures such changes in the boundary conditions, it would be appropriate to use the Events interface. See, for example:
www.comsol.com/blogs/modeling-a-periodic-heat-load/
Best Regards,