[nikhil]

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

[Pavlos]

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.

[nikhil]

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.

[Vijay]

You cannot have velocity and pressure boundary condiitons in a single domain...I guess

[Pavlos]

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."

[Pavlos]

Originally Posted by Vijay

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.

[Karl]

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

[Pavlos]

Originally Posted by Karl

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.

[nikhil]

Thanks all...

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