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Flow rate at inlet
Posted Feb 15, 2015, 11:23 a.m. EST Fluid & Heat Version 5.0 4 Replies
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Hi,
Could someone help me to understand how the boundary conditions presented in page 5 of the following paper could be implemented in COMSOL?
www.comsol.com/paper/download/43839/Smith_pres.pdf
Best regards.
Could someone help me to understand how the boundary conditions presented in page 5 of the following paper could be implemented in COMSOL?
www.comsol.com/paper/download/43839/Smith_pres.pdf
Best regards.
4 Replies Last Post Feb 16, 2015, 10:25 a.m. EST
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Posted:
10 years ago
Hi
I understand that as defining:
1) A "Global - Definitions - Parameter" Q_set = xxx [(kg/m^3)*(m/s)*(m^2)] whatever mass flux rate you desire
2) Define a Coupling Variable Surface Integration over the inlet Boundary (intop1)
3) Define a Variable Q_in = intop1(rho*(nx*u+ny*v+nz*w))
4) Add on your main "Physics node" - "Global - Global Equation" of variable name "P_in" such as "Q_in-Q_set" (implicit =0)
5) Add an inlet normal flow BC on your "inlet" boundary, and set it to the global pressure value "P_in"
6) solve the problem
If not already done, you will need to turn on the "File - Parameters - Model Builder - Advanced Physics" Options
However, if you have V5 (perhaps it was there already in V4, I cannot remember now) you can select under the "Inlet" node "mass flow" and just give the value of Q_set, the rest is already set up in COMSOL for you
--
Good luck
Ivar
I understand that as defining:
1) A "Global - Definitions - Parameter" Q_set = xxx [(kg/m^3)*(m/s)*(m^2)] whatever mass flux rate you desire
2) Define a Coupling Variable Surface Integration over the inlet Boundary (intop1)
3) Define a Variable Q_in = intop1(rho*(nx*u+ny*v+nz*w))
4) Add on your main "Physics node" - "Global - Global Equation" of variable name "P_in" such as "Q_in-Q_set" (implicit =0)
5) Add an inlet normal flow BC on your "inlet" boundary, and set it to the global pressure value "P_in"
6) solve the problem
If not already done, you will need to turn on the "File - Parameters - Model Builder - Advanced Physics" Options
However, if you have V5 (perhaps it was there already in V4, I cannot remember now) you can select under the "Inlet" node "mass flow" and just give the value of Q_set, the rest is already set up in COMSOL for you
--
Good luck
Ivar
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Posted:
10 years ago
Ivar,
It seems consistent, except for the fact that P_in cannot be equal to Q_in-Q_set, which should be 0 and, thus, the pressure at the inlet would be 0. I am aware of the mass flow inlet in v4.3a, but it applies for the Laminar Flow interface and not for the High Mach Number Flow interface, which I intend to use.
Best regards.
It seems consistent, except for the fact that P_in cannot be equal to Q_in-Q_set, which should be 0 and, thus, the pressure at the inlet would be 0. I am aware of the mass flow inlet in v4.3a, but it applies for the Laminar Flow interface and not for the High Mach Number Flow interface, which I intend to use.
Best regards.
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Posted:
10 years ago
Hi,
I have found the way to solve the problem. Thank you.
Best regards.
I have found the way to solve the problem. Thank you.
Best regards.
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Posted:
10 years ago
Hi
Be careful how you read the Global equation:
P_in is NOT SET to the difference,
P_in is a new dependent variables adjusted such that Q_in-Q_set is equal to 0
That is quite different ;)
There are a fiew Blogs and Knowledge Base article about this way of adding your own equations
--
Good luck
Ivar
Be careful how you read the Global equation:
P_in is NOT SET to the difference,
P_in is a new dependent variables adjusted such that Q_in-Q_set is equal to 0
That is quite different ;)
There are a fiew Blogs and Knowledge Base article about this way of adding your own equations
--
Good luck
Ivar