[Lorenzo210]

Hi everyone,


I am using COMSOL 6.1 to simulate a droplet evaporation.


Geometry:
- 2D axis symmetric domain, 90degrees circle domain with R= 60*R_droplet
- Droplet initialized with its R_droplet and theta0 contact angle.


Physics:
- Laminar two phase flow with moving mesh;

- Heat tranfer in fluids;
- Transport of concentrated species;
- Transport of diluited species;

- Mathematical ODE for various calculations.


Multiphysics:
- Nonisothermal flow
- Marangoni effect
-Reacting flow


Problem: I tried to apply the Marangoni effect to the liquid-gas interface, but I cannot select the interface, only wall boundaries can be selected.


I am a bit confused because I took an identical model written in COMSOL 5.6 (not sure about the version), and the Marangoni effect can be applied to the interface.


The 5.6 Marangoni effect gives a warning that "This feature is obsolete and will be removed in future versions." so for that reason I am trying to use the new Marangoni effect version.


Has anyone any clue why the newest version cannot select the liquid-gas interface? The tutorial and the COMSOL documentation (user guide and similar) have not helped.


I was able to run successfully the older model enabling and disabling the Marangoni Effect, so the only issue is with the newest version.


Many thanks.


Regards,
Lorenzo

[Feeric]

You should be able to select your interface thanks to the Free Surface boundary condition that appears in the laminar flow physics, provided that you have selected a deforming domain in the moving mesh interface (or I guess 2 in tour case, since I understand you have a small droplet inside a bigger volume, in such case you need to use the Fluid/Fluid Interface).

You should not be using the Marangoni multiphysics though, which is not meant to be used with moving mesh. Just having a surface tension that depends analitically on the temperature should be enough. You may add the dependance on the concentration for the surface tension if you know the dependance and if that makes sense in your case.

Originally Posted by Lorenzo210

Hi everyone,


I am using COMSOL 6.1 to simulate a droplet evaporation.


Geometry:
- 2D axis symmetric domain, 90degrees circle domain with R= 60*R_droplet
- Droplet initialized with its R_droplet and theta0 contact angle.


Physics:
- Laminar two phase flow with moving mesh;

- Heat tranfer in fluids;
- Transport of concentrated species;
- Transport of diluited species;

- Mathematical ODE for various calculations.


Multiphysics:
- Nonisothermal flow
- Marangoni effect
-Reacting flow


Problem: I tried to apply the Marangoni effect to the liquid-gas interface, but I cannot select the interface, only wall boundaries can be selected.


I am a bit confused because I took an identical model written in COMSOL 5.6 (not sure about the version), and the Marangoni effect can be applied to the interface.


The 5.6 Marangoni effect gives a warning that "This feature is obsolete and will be removed in future versions." so for that reason I am trying to use the new Marangoni effect version.


Has anyone any clue why the newest version cannot select the liquid-gas interface? The tutorial and the COMSOL documentation (user guide and similar) have not helped.


I was able to run successfully the older model enabling and disabling the Marangoni Effect, so the only issue is with the newest version.


Many thanks.


Regards,
Lorenzo

[Lorenzo210]

Originally Posted by Feeric

You should be able to select your interface thanks to the Free Surface boundary condition that appears in the laminar flow physics, provided that you have selected a deforming domain in the moving mesh interface (or I guess 2 in tour case, since I understand you have a small droplet inside a bigger volume, in such case you need to use the Fluid/Fluid Interface).

You should not be using the Marangoni multiphysics though, which is not meant to be used with moving mesh. Just having a surface tension that depends analitically on the temperature should be enough. You may add the dependance on the concentration for the surface tension if you know the dependance and if that makes sense in your case.

Hello Feeric,


Thank you very much for the suggestion!
I didn't know that the Marangoni multiphysics is not meant to be used with moving mesh, may you kindly tell me where I can find (or understand) that type of information?



Yes, I have a droplet inside a domain and I'm using a moving mesh, so the analytical implementation you suggested seems to work.


I was confused because I tried implementing the multiphysics in many versions (available from the COMSOL's test case tutorial for Marangoni effect), and the 5.6 version allows me to use the multiphysics on the liquid-liquid interface.


Best regards,
Lorenzo