using surface tension as volume force along the interface

[annier]

In the LevelSetSolver coupled with NavierStokes solver, where do we need to assign the value of surface tension coefficient in the Solver Input File?
thanking you in advance.
yours
annier

[annier]

or do we need a separate User Defined Subroutine (Solver ) for surface tension.
thanking you in advance
yours
annier

[annier]

I have found a relevant discussion in this post:
viewtopic.php?f=3&t=808&p=2739&hilit=su ... sion#p2739

[annier]

Is the surface tension force modeled as a Continuum Surface Force (CSF)?

[raback]

I'm not familiar what CSF stands for. However, I can confirm that with levelset the boundary integral is transformed into a volume integral that should be smeared over few elements. -Peter

[annier]

dear Peter,
Thank you very much for your kind reply.
yours
annier

[annier]

In the LevelSetSolver coupled with NavierStokes solver, where do we need to assign the value of surface tension coefficient in the Solver Input File?
thanking you in advance.
yours
annier

I got the answer to this question as

Code: Select all

Solver n
Equation = String " Curvature"
Procedure = File "LevelSet" "LevelSetCurvature"
...
Curvature Coefficient = 7.2e-2  !Surface tension coefficient between air and water is 0.072 N/m (assumed constant)
...
End

That is the "surface tension coefficient" has the name "curvature coefficient " in levelsetcurvature solver.
The curvature coefficient, along with dirac delta function is utilized by the LevelSetCurvature subroutine/solver to yield the field variable curvature therein.

After this the curvature field is recognized as a potential coefficient for body force in Navier-Stokes solver. Similarly, the level set surface (named as field variable "surface") is recognized as a potential field for the body force in the Navier-Stokes solver.This can be done with the following code in the body force n section of the SIF.

Code: Select all

Body Force 1
  Potential Force = Logical True
  Potential Field = Equals Surface   !field
  Potential Coefficient = Equals Curvature    !coefficient
...
 !Other body force for body 1
...
End

As the surface tension at the interface is included as body force part in the Navier-stokes solver, the surface tension is now solved as the volume force.In Navier-Stokes solver, it is solved as an external force i.e. in the similar way as of the case of a fluid with charges being coupled to external electric fields.
In both cases
external force = potential coefficient times grad (potential field)
1. In context of LevelSet Solver and LevelSetCurvature Solver coupled with Navier-Stokes Solver,
external force = curvature {grad(surface)}
2. In context of Poisson-Boltzmann Solver coupled with Navier-Stokes Solver,
external force = charge density {grad(electrostatic field)}

yours
annier