Guidance Request on Using the 'constantCurvature' Surface Tension Model to Fix the Curvature of a Rising Microbubble Under Gravity

[MontelukastNa]

Dear Henning and the TwoPhaseFlow Development Team,

First of all, I would like to express my gratitude for your excellent work on the TwoPhaseFlow library. It has been incredibly helpful for understanding bubble dynamics, and I truly appreciate your contributions.

To provide some context, I am currently working in the following environment:
OpenFOAM version: v2112
TwoPhaseFlow version: branch:of2112, interFlow

From the source code, I noticed that the constantCurvature model in the surfaceTensionForceModel appears to be designed to address issues related to spurious currents. I am interested in using the VOF method to simulate microbubbles (with a diameter less than 150 μm) rising in water. Typically, the flow field of microbubbles is computed by wrapping the flow around a fixed bubble, but my supervisor has asked me not to use this approach.

After numerous attempts, I have found that surface tension models such as RDF, fitPara, and HeightFunction are capable of simulating bubbles lager than 300μm with a mesh resolution of D/64, but none of these models provide satisfactory results for bubbles smaller than 300μm.

As a potential solution, I tried using the constantCurvature model to fix the curvature, which I hoped would resolve the issue of rising microbubbles (less than 150 μm in diameter). Below is the relevant section from my constant/transportProperties file:

surfaceForces
{
  sigma 0.0717;
  surfaceTensionForceModel constantCurvature;
  curv            6666.66667;
  accelerationModel gravity;
  gravity (0 0 -9.81);
  deltaFunctionModel alphaCSF;
}

Unfortunately, I did not obtain the expected results. It seems that the constantCurvature model does not perform as expected when gravity is applied. The results shows that microbubble get deformed as follow:

⏩In brief, could you kindly provide guidance on how to use the constantCurvature model to fix the curvature of a rising microbubble under gravity? Any insights into how the model should be configured when gravity is present would be greatly appreciated.

Thank you for your time and any assistance.
Best regards,
Na