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Track Moving Drop Outline in 3D simulation

Posted 2025/05/07 11:51 GMT-4 General, Equation-Based Modeling Version 6.2 0 Replies

Mark JoFa

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I have a model that solves a Stokes flow problem with a nonconservative external body force acting on the drop. The external force is dependent on the position of the drop due to attenuation occurring only under the bulk fluid.

For the 2D case, this meant I had to track the rear and front of the drop which I did by coupling a Domain ODEs and DAEs to my Coefficient Form PDE where the Stokes Flow was solved. The Domain ODEs and DAEs used the Max and Min Nonlinear Couplings to keep track of the location of the maximum height (xpeak), the rear contact line (xr) and the front contact line (xf). This was fine enough and worked as intended.

I now want to just extend my model to 3D, however, the tracking is much more complicated because now rather than having to solve for 3 points, what I actually need to solve is the entire boundary of the drop and update the acoustic force accordingly. What would be the easiest way of doing this?

Note that I still have the Stokes Flow problem, which when reduced to a generalized thin-film equation, can be modeled using Coefficient Form PDE. All I need to figure out is how to solve for the boundary of the drop, say xybound. Once I have this, I can then just have the acoustic force in the Coefficient Form PDE equations call xybound at each time step to update the force so that attenuation begins at the correct locations. Also, my simulations use a precursor film of thickness .01 so I was thinking the easiest way to track the outline of the drop would be to just track the levelset where the fluid thickness h=h=.017 (where I would experiment with different values of h).

I tried attaching the 2D code I have working and my attempt in 3D but it says the files are too large. If this is needed, can someone let me know how to do this with the size constraint.

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