Visualising the effect of surface tension

[ponjavic]

Hello!

I am using the Lattice Boltzmann method to simulate multiphase flow. The details are not important but the main drive behind multiple phases being simulated is interparticle forces. Now I am trying to visualise intuitively how such interparticle forces will cause a fluid to experience surface tension. As known, in 2d, this will ultimately cause the liquid phase to form a circle.

Basically my suggestion is to take a square and then comparing a particle at the edge of the square with a particle at a corner of the square. Not forces are only considered due to neighbouring nodes on the mesh and the forces are attractive and dependent on nearby densities. My argument is that because these two particles will consider different forces the geometry has to change. This change will continue until it forms a circle because this is the only case where the forces are equal for all particles.

Still I am having trouble visualising this myself. Although I can understand the forces experienced are different I am unsure as to how. A look at the figure might help to show what I am trying to accomplish. Any help would be appreciated.https://www.physicsforums.com/attachments/19169
Red circles represent the two nodes under consideration and the yellow dots show the eight neighbouring needs which provide attractive forces based on the density at their positions.

 

[Evalesco]

Hi there! It sounds like you are on the right track. In order to understand how the interparticle forces cause a fluid to experience surface tension, you need to consider the difference in forces experienced by a particle at the edge of the square compared to a particle at a corner of the square. Visualizing this can be difficult, so it might help to look at a diagram of the situation you are describing. The red circles represent the two nodes under consideration and the yellow dots show the eight neighboring nodes which provide attractive forces based on the density at their positions. This should help you understand why the geometry will ultimately form a circle when these forces are considered.

 

[astrokreng]

Hello there,

Thank you for sharing your work on simulating multiphase flow and investigating surface tension using the Lattice Boltzmann method. It is always exciting to see how computational methods can help us understand complex physical phenomena.

From your description, it seems that you are trying to visualize the effect of surface tension on a liquid phase by comparing the forces experienced by two particles at different positions on a square grid. As you mentioned, the forces experienced by these particles will differ due to the neighboring nodes on the mesh and the attractive forces dependent on nearby densities.

To help you visualize this, let's consider the two particles at the edge and corner of the square grid. The particle at the edge only has four neighboring nodes, while the particle at the corner has eight neighboring nodes. This means that the attractive forces acting on the particle at the corner will be stronger than the forces acting on the particle at the edge because there are more neighboring nodes contributing to the force.

Moreover, the forces acting on each particle will also vary depending on the density at their respective positions. For example, if the particle at the edge has a higher density compared to the particle at the corner, the attractive forces acting on it will be stronger. This will cause the particle at the edge to move towards the particle at the corner, reducing the surface area of the liquid and forming a circular shape.

In summary, the varying forces experienced by the particles at different positions on the square grid, combined with the attractive forces dependent on nearby densities, will cause the liquid to form a circular shape due to surface tension. I hope this helps in visualizing the effect of surface tension on the liquid phase in your simulation. Keep up the great work!