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Equilibrium shape of a water droplet
Posted Jun 20, 2023, 1:47 a.m. EDT Fluid & Heat, Computational Fluid Dynamics (CFD), Microfluidics Version 6.1 2 Replies
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Hello everyone!
Could anyone suggest the most efficient strategy to compute the stationary equilibrium shape of a water droplet? I know it is a sphere if only surface tension is present, but it can be something else under additional forces such as from an external electric field.
Now I know how to compute the transient deformations of the droplet under e.g. surface tension - with moving mesh, freely deforming domain and single phase laminar flow. So in principle I can get the stationary solution by waiting long enough till the transient ceases and the stationay state is reached, but I am wondering if there is a more direct way to get the final shape of the droplet starting with a reasonable guess?
Can the moving mesh deform at once into the correct shape in a stationary study? Or do I have to use other methods instead, such as phase field/level set?
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I had the same problem and had to wait a long time for the droplet to reach its equilibrium shape... The trick I played to it was that I defined a large viscosity (e.g. 0.1 Pa.s) and ran the simulation to get the droplet shape. The viscosity does not contribute to the stationary shape of the droplet, and because a high viscosity liquid doesn't jiggle easily, the oscillations were dampened significantly and the convergence was fast.
Then used the defromed geometry in my main study with the real liquid.
Hope it helps.
Amin
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Thanks for the suggested shortcut! Indeed, modeling transient behaviour is probably the only viable strategy to get the equilibrium shape of the droplet, since a stationary study does not seem to allow for a geometry change. But such a chage is inevitable since I am solving for the unknown final shape and I have to start with some guess (i.e. draw some geometry in the first place).