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Compressible flow modeling in Fluent

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Old   August 8, 2011, 12:35
Default Compressible flow modeling in Fluent
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Nik
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Hello,

I have few questions on compressible flow modeling in Fluent

1. Can i use velocity inlet and pressure outlet BCs while modeling compressible flow?

2. Can i use pressure based solver to model the compressible flow?

3. I am using velocity inlet, pressure outlet in one of my cases and pressure based solver. However, when i initialize the solution, i am getting this error message

Error:
FLUENT received fatal signal (ACCESS_VIOLATION)
1. Note exact events leading to error.
2. Save case/data under new name.
3. Exit program and restart to continue.
4. Report error to your distributor.
Error Object: #f


can anyone please explain why am i getting such error message and how to overcome it?

Thanks,
Nikhil
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Old   August 8, 2011, 12:55
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Pavel Staša
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For questions one and two my answer is YES.
For last one, my oppinion is that mesh might be wrong or type of other BC are wrong.

If I´m wrong, correct me.
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Old   August 8, 2011, 13:16
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Mesh is pretty much simple and without any error.
Its a 2D domain. Therefore apart from inlet and outlet; other two boundaries are walls which are fine from my consideration.
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Old   August 8, 2011, 15:55
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Vijay
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You cannot have velocity and pressure boundary condiitons in a single domain...I guess
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Old   August 9, 2011, 04:24
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Pavel Staša
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My apology. I really thought that velocity inlet can be used for compressible flow but there is a explanation in Fluent manual.

Velocity inlet BC:
"This boundary condition is intended for incompressible flows, and its use in compressible flows will lead to a nonphysical result because it allows stagnation conditions to float to any level. You should also be careful not to place a velocity inlet too close to a solid obstruction, since this could cause the inflow stagnation properties to become highly non-uniform."
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Old   August 9, 2011, 04:30
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Pavel Staša
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Quote:
Originally Posted by Vijay View Post
You cannot have velocity and pressure boundary condiitons in a single domain...I guess
You can easily use velocity and pressure BC in a single domain. There is no problem.


You can use three combinations of BC at the inlet and outlet.
1. Velocity inlet - Outflow
2. Velocity inlet - Pressure outlet
3. Pressure inlet - Pressure outlet


Instead of velocity inlet you can use mass flow inlet too, of course.
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Old   August 9, 2011, 07:07
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Karl Kargl
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For compressible flows only two combinations are valid:

1. Mass Flow Inlet + Pressure Outlet
2. Pressure Inlet + Pressure Outlet

Velocity Inlet and Outflow are incorrect BC's for modeling compressible flows with FLUENT.

Best Regards
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Old   August 9, 2011, 08:57
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Pavel Staša
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Quote:
Originally Posted by Karl View Post
For compressible flows only two combinations are valid:

1. Mass Flow Inlet + Pressure Outlet
2. Pressure Inlet + Pressure Outlet

Velocity Inlet and Outflow are incorrect BC's for modeling compressible flows with FLUENT.

Best Regards

Of course, I mean generally you can use velocity inlet and Outflow, not for case of combressible flows.

Velocity Inlet is incorrect and Outflow is incorrect too for compressible flows.
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Old   August 9, 2011, 14:18
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Thanks all...

With mass flow inlet and pressure outlet my case is running smoothly.
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