[Mattt]

Hello everyone!

I am currently working on the simulation of a fluidic oscillator, and my simulation leads backflows to appear on the boundaries of my outflow.

After trying different kinds of Boundary Conditions (zeroGradient for U and p=0, advective for U and p=0, pressureInletOutletVelocity for U and totalPressure for p...), they all have led to the apparition of backflows from the top or the bottom of the space after the oscillator (where I want to observe the behaviour of the flow after the nozzle), which pushes the flow to the top or the bottom: I don't have a symmetric flow...

Would you have any idea about what I could change to avoid this kind of issue?

In particular, I thought about implementing a sponge layer on few cells next to my boundaries to avoid this phenomenon, but I am new with OpenFoam (I use OpenFoam8). Yet, after searching for quite a long time, I haven't been able to find a clear explanation of a way to implement it: the main idea I considered was to add a new field spongeNu (example of a name) which would multiply the physical viscosity. It would be 1 in the middle of the studying space and would increase next to the boundaries.

Could you tell me if it is the best way to create sponge layers, and would there be a detailed tutorial on the way to implement it?

Thanks a lot for considering my issue and have a good day!

Best regards,

Matthias

[alligngr8]

Originally Posted by Mattt

Hello everyone!

I am currently working on the simulation of a fluidic oscillator, and my simulation leads backflows to appear on the boundaries of my outflow.

After trying different kinds of Boundary Conditions (zeroGradient for U and p=0, advective for U and p=0, pressureInletOutletVelocity for U and totalPressure for p...), they all have led to the apparition of backflows from the top or the bottom of the space after the oscillator (where I want to observe the behaviour of the flow after the nozzle), which pushes the flow to the top or the bottom: I don't have a symmetric flow...

Would you have any idea about what I could change to avoid this kind of issue?

In particular, I thought about implementing a sponge layer on few cells next to my boundaries to avoid this phenomenon, but I am new with OpenFoam (I use OpenFoam8). Yet, after searching for quite a long time, I haven't been able to find a clear explanation of a way to implement it: the main idea I considered was to add a new field spongeNu (example of a name) which would multiply the physical viscosity. It would be 1 in the middle of the studying space and would increase next to the boundaries.

Could you tell me if it is the best way to create sponge layers, and would there be a detailed tutorial on the way to implement it?

Thanks a lot for considering my issue and have a good day!

Best regards,

Matthias

If I am not wrong, sponge layers are used as an alternative to NSCBC to avoid reflection of waves. right?
In any case were you able to arrive in doing so?

Thanks