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Setting pressure
Posted 29 lug 2015, 05:22 GMT-4 Fluid & Heat, Computational Fluid Dynamics (CFD), Studies & Solvers Version 5.2 3 Replies
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I want to study flow in pipe
I want to set v = 0.05 m/s AND p = 5 atmat the inlet
How to set them both? I mean, under laminar flow -> inlet -> boundary conditions I can choose one or the other, right?
I want to set v = 0.05 m/s AND p = 5 atmat the inlet
How to set them both? I mean, under laminar flow -> inlet -> boundary conditions I can choose one or the other, right?
3 Replies Last Post 28 nov 2016, 07:20 GMT-5
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Posted:
9 years ago
upgrade:
I've set the velocity under laminar flow -> inlet
then i've added pressure point constraint (under lamina flow, as well), and choosen the two vertex of the inlet. this allows me to have 5atm in that two points. Is there a way to have 5 atm on the whole line?
I could add many many points under geometry where the inlet line is, but I'm quite sure there has to be a better way to solve this problem.
help me... SOS
I've set the velocity under laminar flow -> inlet
then i've added pressure point constraint (under lamina flow, as well), and choosen the two vertex of the inlet. this allows me to have 5atm in that two points. Is there a way to have 5 atm on the whole line?
I could add many many points under geometry where the inlet line is, but I'm quite sure there has to be a better way to solve this problem.
help me... SOS
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Posted:
9 years ago
Hi
First of all, are you aware that the flow equations solve for a gauge pressure nominally set to "0" on the outlet. And you add an Gauge offset value of by default 1[atm] to get p_absolute=p+p_ref, the one used to map the material properties of your fluid if these are pressure dependent ?
So you need to define the inlet/outlet "p's" as the pressure drop along your pipe, and not "absolute" pressure, or reset the default p_ref value to "0" ...
then normally the fluid velocity and pressure drop are related via the fluid flow equations, so you cannot set all => what our your outlet BC conditions?
I usually define an initial pressure drop along my pipe based on the Poiseuille formula so the solver converges far quicker, and an inlet velocity of a parabolic profile to respect the no-slip boundary conditions. And my defaults are velocity in, pressure out.
Wht you might want to do is to add an equation on the outlet pressure to adjust the inlet pressure to i.e. 5(-1?)[atm]
--
Good luck
Ivar
First of all, are you aware that the flow equations solve for a gauge pressure nominally set to "0" on the outlet. And you add an Gauge offset value of by default 1[atm] to get p_absolute=p+p_ref, the one used to map the material properties of your fluid if these are pressure dependent ?
So you need to define the inlet/outlet "p's" as the pressure drop along your pipe, and not "absolute" pressure, or reset the default p_ref value to "0" ...
then normally the fluid velocity and pressure drop are related via the fluid flow equations, so you cannot set all => what our your outlet BC conditions?
I usually define an initial pressure drop along my pipe based on the Poiseuille formula so the solver converges far quicker, and an inlet velocity of a parabolic profile to respect the no-slip boundary conditions. And my defaults are velocity in, pressure out.
Wht you might want to do is to add an equation on the outlet pressure to adjust the inlet pressure to i.e. 5(-1?)[atm]
--
Good luck
Ivar
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Posted:
8 years ago
Dear Ivar,
is it possible to set a specific pressure drop along the tube or only inlet vel+ inlet pressure + outlet pressure? My problem is, that right after the inlet my pressure drops really fast! So the high inlet pressure remains only over let´s say 5% of the total tube length.
Regards, Kristina
is it possible to set a specific pressure drop along the tube or only inlet vel+ inlet pressure + outlet pressure? My problem is, that right after the inlet my pressure drops really fast! So the high inlet pressure remains only over let´s say 5% of the total tube length.
Regards, Kristina