Viscous damping while submerged

Asked by George Lesica on 2013-03-29

I'm playing around with buoyant forces. I've run into a problem and I'm looking for some advice on how to proceed. I don't necessarily expect a simple solution here...

Basically, I want to be able to apply a viscous damping force to particles while they are fully or partially submerged (using a buoyant force). The implementation of `BuoyancyForceGroup` supports a fluid height, but none of the damping forces appear to support such a parameter, damping applies to the entire domain.

I am considering two ways forward. The first would be to implement a viscous damping force that allows for a height parameter, the same way the buoyancy force does. Alternately, I could just edit the viscous damping force to accept such a parameter. The other option I am considering is to add a viscosity parameter to the buoyant force and apply it when the buoyant force itself is calculated.

I figured I would ask about this before I started changing code to see if there are any reasons to prefer one method over the other, and to make sure I haven't missed something that already exists (which would be super!). Thoughts?

Thank you all, in advance.

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George Lesica
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Dion Weatherley (d-weatherley) said :
#1

Hi George,

Any of your three options would be ok, although probably the best would be to implement a new viscous damping interaction group. Here are thoughts on each option:

1) modify existing viscous damping IG
* this is the easiest from a coding perspective but will render your version of the code incompatible with the ESyS-Particle trunk. If you want to upgrade to a later version you will need to re-implement your changes with each upgrade

2) add viscous damping to existing buoyancy IG
* this is also very easy from a coding perspective and I would be willing to merge this change into the trunk if the damping can be easily toggled on/off. Merging your changes with the trunk will mean no problems with upgrading to later versions.

3) new 'submerged viscous damping' IG
* this requires quite a bit of coding but can copy the existing viscous damping implementation. I would be very happy to see this merged with the trunk for future versions of ESyS-Particle. It is the best option IMO, because it allows use of the IG independantly of buoyancy should certain applications require it.

Cheers,

Dion

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George Lesica (oldmanstan) said :
#2

Sorry for the delayed response, thank you for the reply!