[nazmulislam]

Hi,


I am trying to observe unsteady, laminar and incompressible flow through an axisymmetric periodic tube.


I have initialised the uniform velocity (along the tube axis) inside the tube and imposed periodic boundary conditions (cyclicAMI) at the inlet and outlet.



Now, I would like to create an oscillatory flow. I found a tutorial "pitzDailyPulse" with the solver "pimpleFoam" for laminar, incompressible flow. In this tutorial, the velocities are distributed at the inlet using the trigonometric COSINE function.



However, since I have imposed cyclicAMI boundary conditions at the inlet and outlet, I cant provide velocities at the inlet. It is mentioned that previously I tried to provide velocity at the inlet with cyclicAMI boundary conditions at the inlet and outlet, it did not work. For that reason, I initialised the uniform velocity inside the tube with cyclicAMI boundary conditions at the inlet and outlet and it worked. Please see more details in the following link:
Periodic BC for a Periodic Tube



I appreciate your suggestions in this regard.


Thanks in advance.

[joshwilliams]

If your inlet and outlet should be periodic but you want to have oscillating flow, then I would think the only other option would be a time-varying source term (e.g. meanVelocityForce in fvOptions). I have not seen many examples where this is time-varying though. You may need to create your own library for this based on the meanVelocityForce implementation. Maybe there is already functionality for time-varying source term.

[nazmulislam]

Originally Posted by joshwilliams

If your inlet and outlet should be periodic but you want to have oscillating flow, then I would think the only other option would be a time-varying source term (e.g. meanVelocityForce in fvOptions). I have not seen many examples where this is time-varying though. You may need to create your own library for this based on the meanVelocityForce implementation. Maybe there is already functionality for time-varying source term.

Hello Josh,


Many thanks for your kind suggestion and option to do this.
I am a new user in OpenFoam. So, could you please tell me more about this, preferably with an example?


Cheers,
Nazmul

[nazmulislam]

Originally Posted by joshwilliams

If your inlet and outlet should be periodic but you want to have oscillating flow, then I would think the only other option would be a time-varying source term (e.g. meanVelocityForce in fvOptions). I have not seen many examples where this is time-varying though. You may need to create your own library for this based on the meanVelocityForce implementation. Maybe there is already functionality for time-varying source term.

Hello Josh,


As you suggested I have created an fvOptions file (see in the attacment) consisting sinusoidal temporal function and put it in the system folder. However, it not working. That is, when I run the simulation using solver icoFoam, this file is not reading which is seen from the log file. I appreciate your kind suggestion in this regards. It is mentioned that I am using OpenFoam V10.


Cheers

[joshwilliams]

icoFoam.C does not call fvOptions as far as I am aware. Try pimpleFoam.

[nazmulislam]

Originally Posted by joshwilliams

icoFoam.C does not call fvOptions as far as I am aware. Try pimpleFoam.

Hi Josh,

Thanks again for your suggestion.

However, I have tried with pimpleFoam and received the fatal error message as you can see in the attachment:

It is mentioned that I have only added the fvOptions file as above in the system folder. Do I need to change any codes in any specific file in OpenFoam?

Please provide me your valuable suggestions in this regard.


Cheers

[joshwilliams]

Originally Posted by nazmulislam

Hi Josh,

Thanks again for your suggestion.

However, I have tried with pimpleFoam and received the fatal error message as you can see in the attachment:

It is mentioned that I have only added the fvOptions file as above in the system folder. Do I need to change any codes in any specific file in OpenFoam?

Please provide me your valuable suggestions in this regard.


Cheers

It says you are missing keyword "format". i would check the source code or documentation to see what the keyword represents.

[nazmulislam]

Originally Posted by joshwilliams

It says you are missing keyword "format". i would check the source code or documentation to see what the keyword represents.

Hi Josh,


Thanks for your suggestion. There was a semicolon missing after version 2.
Now, it is working.


Cheers