Hello everybody and thank you in advance for any kind of help you may give,
I am trying to simulate a simple kind of scenario, an air bubble in a water cylinder rising due to buoyancy force.
I made my model axisymmetric and used the level set method (but I want to be able to simulate the same scenario also with the phase field and moving mesh method in the end). I am using v4.2a and I use the stokes flow approximation. I initialize the pressure inside the bubble with young-laplace equation assuming outside pressure is 0.
This example is very similar to the rising bubble model of comsol with an oil droplet in water, but here the second fluid (air) is only in the bubble and not also in the top layer, which is closed by a wetted wall.
What happens is that if I use the incompressible and non conservative form I have a converging solution and the bubble rises, even though the volume fraction seems to decrease in time (mass is not conserved apparently) and if I use the conservative form it inevitably fails to converge.
If I try the compressible Navier Stokes, which is intrinsically conservative, it fails as well.
Since I am not expert with mesh refinement and solver's advanced options, could somebody point some of these things out for me? Or if you find any wrong BC (which I checked over different tutorials and should be fine), could you please highlight me where the errors are?
If I am missing something with the physics, please let me know too, I tried to make it as simple as possible.
I attach the file model if you have the opportunity to check.
Thank you again for your help
Stefano
I am trying to simulate a simple kind of scenario, an air bubble in a water cylinder rising due to buoyancy force.
I made my model axisymmetric and used the level set method (but I want to be able to simulate the same scenario also with the phase field and moving mesh method in the end). I am using v4.2a and I use the stokes flow approximation. I initialize the pressure inside the bubble with young-laplace equation assuming outside pressure is 0.
This example is very similar to the rising bubble model of comsol with an oil droplet in water, but here the second fluid (air) is only in the bubble and not also in the top layer, which is closed by a wetted wall.
What happens is that if I use the incompressible and non conservative form I have a converging solution and the bubble rises, even though the volume fraction seems to decrease in time (mass is not conserved apparently) and if I use the conservative form it inevitably fails to converge.
If I try the compressible Navier Stokes, which is intrinsically conservative, it fails as well.
Since I am not expert with mesh refinement and solver's advanced options, could somebody point some of these things out for me? Or if you find any wrong BC (which I checked over different tutorials and should be fine), could you please highlight me where the errors are?
If I am missing something with the physics, please let me know too, I tried to make it as simple as possible.
I attach the file model if you have the opportunity to check.
Thank you again for your help
Stefano