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Impose a pressure
Posted 13 nov 2015, 04:35 GMT-5 Fluid & Heat, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 5.0, Version 5.1 3 Replies
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Hi,
I have a big problem ! Fisrt of all, i use two physics : laminar flow and heat transfer.
Then, my problem is about laminar flow physic. I put "0" values for v initial et p initial, i use inlet and outlet with pressure condition 250 bar pressure inlet and 0 outlet. Then i want to impose a pressure in the middle of my geometry to have 3 point of pressure but i don't know how ...
Someone can help ?
Thanks
I have a big problem ! Fisrt of all, i use two physics : laminar flow and heat transfer.
Then, my problem is about laminar flow physic. I put "0" values for v initial et p initial, i use inlet and outlet with pressure condition 250 bar pressure inlet and 0 outlet. Then i want to impose a pressure in the middle of my geometry to have 3 point of pressure but i don't know how ...
Someone can help ?
Thanks
3 Replies Last Post 17 nov 2015, 08:40 GMT-5
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Posted:
9 years ago
Hi
Normally imposing two pressures already makes the solver suffer, and three is probably over-constraining the model solution. I mostly use input velocity + output pressure, this gives you the pressure drop per input velocity and solves mostly straight away.
If you want a given pressure at a given location you can add a "global equation" with a variable for the input velocity and have COMSOL adapt this to impose a given pressure at your metrology point/boundary (ideally average pressure value over a boundary)
--
Good luck
Ivar
Normally imposing two pressures already makes the solver suffer, and three is probably over-constraining the model solution. I mostly use input velocity + output pressure, this gives you the pressure drop per input velocity and solves mostly straight away.
If you want a given pressure at a given location you can add a "global equation" with a variable for the input velocity and have COMSOL adapt this to impose a given pressure at your metrology point/boundary (ideally average pressure value over a boundary)
--
Good luck
Ivar
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Posted:
9 years ago
But to corelate with the expermiental part, i have just the input pressure, the output pressure and one between them. I know nothing about the input velocity and his form ?
And second, How to find create this "global equation" ?
Thanks !
And second, How to find create this "global equation" ?
Thanks !
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Posted:
9 years ago
Hi
but you should be mode specific on the true variables here, without more details on your model it's difficult to answer well. Normally if you fix the pressure at input, output and somewhere in-between, does it mean that your pressures are really constant over the Boundaries? further what is then changing T and U for the SPF physics the viscosity, perhaps also the density, that could dictate a velocity for this particular pressure drop.
Check the equations and find which are the dependent parameter taking the lead and which is controlled, you might need to adapt the segregated solver variables and their order
--
Good luck
Ivar
but you should be mode specific on the true variables here, without more details on your model it's difficult to answer well. Normally if you fix the pressure at input, output and somewhere in-between, does it mean that your pressures are really constant over the Boundaries? further what is then changing T and U for the SPF physics the viscosity, perhaps also the density, that could dictate a velocity for this particular pressure drop.
Check the equations and find which are the dependent parameter taking the lead and which is controlled, you might need to adapt the segregated solver variables and their order
--
Good luck
Ivar