Convergence issues in time dependent moving mesh simulation

Topics: Mesh, Solving, Geometry, 4.2a, 4.3a

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Alexander Sinkevich

Alexander Sinkevich

January 28, 2013 11:18pm UTC

Convergence issues in time dependent moving mesh simulation

Hi all,

I'm simulating the evaporation of a sessile droplet (2D-axisymmetric model). The droplet is very hydrophilic and has a very small contact angle (picture attached). The coupled physics are:

1. Transport of Diluted Species (evaporation flux normal to the curved surface, no flux on bottom, symmetry on side)
2. Deformed Geometry (to simulate the evaporation; droplet is shrinking normal to its curved surface and is allowed to move in the r-direction, not the z-direction)

The model does not converge in time-dependent simulations due to the poor mesh quality in the sharp angled region.

I've tried refining the mesh at the point, refining the mesh in a boxed region around and near the point, played with mesh size & distribution settings along the curve/near the point, and even experimented with boundary layer meshes (something I still don't fully understand).

Strangely, the addition of boundary layers allowed the model to run for at least 60 seconds (goal: 500 seconds) until inverted mesh elements become damaging and stop the simulation.

I am aware that creating a fillet at the tip and/or changing the geometry to increase the contact angle may alleviate these mesh issues but what if that is not possible? If I want to simulate this very hydrophilic scenario, what is the best route to take? Perhaps I am still not too familiar with mesh size settings. I am also wondering why a boundary layer mesh setting along the curved surface slightly improved my model.

Any help will be very much appreciated.

Many thanks in advance,

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