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Laminar flow between two parallel plate with a rectangle step
Posted Oct 5, 2013, 1:39 p.m. EDT Fluid & Heat, Computational Fluid Dynamics (CFD), Geometry 2 Replies
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Hi,
I am new to comsol. I am trying to simulate laminar flow between two plates. In my model upper plate is moving with a constant velocity and lower plate is stationary and also it has a rectangle step in middle. Inlet and outlet boundary conditions are of zero ambient pressure. I have drawn the pressure plots, in the plot pressure has developed symmetrically i.e. half of the length pressure is positive and half of the length pressure is negative.
But, I want only positive pressure half of the length and negative pressure should be zero.
So, how do I make negative pressure zero over the other half of the length?
Which boundary condition shell I use for this purpose?
Thank you.
I am new to comsol. I am trying to simulate laminar flow between two plates. In my model upper plate is moving with a constant velocity and lower plate is stationary and also it has a rectangle step in middle. Inlet and outlet boundary conditions are of zero ambient pressure. I have drawn the pressure plots, in the plot pressure has developed symmetrically i.e. half of the length pressure is positive and half of the length pressure is negative.
But, I want only positive pressure half of the length and negative pressure should be zero.
So, how do I make negative pressure zero over the other half of the length?
Which boundary condition shell I use for this purpose?
Thank you.
2 Replies Last Post Feb 13, 2017, 5:31 a.m. EST
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Posted:
1 decade ago
I think having p=0 at inlet AND outlet is you problem. Try setting p=0 only for the outlet. You
need a pressure drop over the device.
Regards
Jens
need a pressure drop over the device.
Regards
Jens
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Posted:
8 years ago
Hello community!
I do model 2D laminar air flow within compliant (flexible) tube with a constriction by introducing gauge pressure (relative pressure) boundaries (inlet pressure = 400[Pa] and outlet pressure pressure = 0[Pa]). I do so because velocity boundary condition at the inlet would not reflect the physics appropriately (it would prescribe mass flow eintering the tube what is not the case). The simulation runs stable. I do observe altering pressure values (with zero crossing) in the middle of the channel. A pressure drop within the constriction is plausible but what do negative pressure values mean? What does COMSOL relate the pressure to? Is it always the zero pressure boundary or outlet?
Many Thanks in advance!
With kind regards
Alexander
I do model 2D laminar air flow within compliant (flexible) tube with a constriction by introducing gauge pressure (relative pressure) boundaries (inlet pressure = 400[Pa] and outlet pressure pressure = 0[Pa]). I do so because velocity boundary condition at the inlet would not reflect the physics appropriately (it would prescribe mass flow eintering the tube what is not the case). The simulation runs stable. I do observe altering pressure values (with zero crossing) in the middle of the channel. A pressure drop within the constriction is plausible but what do negative pressure values mean? What does COMSOL relate the pressure to? Is it always the zero pressure boundary or outlet?
Many Thanks in advance!
With kind regards
Alexander