Irreducible flows of active particles

[ronojoy]

@rupertnash, our recent paper provides expressions for the irreducible parts of the force densities due a finite-sized active particle. Subgrid currently only includes the stresslet, which is constructed as a pair of stokeslets. This method of construction becomes increasingly cumbersome as we increase in order. A more robust method is to implement the expressions in our paper directly, replacing the delta function by the Peskin version. Can this be included as a new feature in subgrid ?

[rupertnash]

Hi Rjoy,

This is certainly possible and you're right about higher-order terms (if you recall, we had to include 4 stokeslets to implement the rotlet reasonably accurately). Are you or a member of your group able to actually do the implementation? I'm pretty busy until December.

If you want to be able to share code with your implementation (you were using something other than LB, IIRC?) then we may need to decouple the particles from the fluid part a bit more.

Cheers,
Rupe

On 23 Oct 2014, at 13:39, Ronojoy Adhikari [email protected] wrote:

@rupertnash, our recent paper provides expressions for the irreducible parts of the force densities due a finite-sized active particle. Subgrid currently only includes the stresslet, which is constructed as a pair of stokeslets. This method of construction becomes increasingly cumbersome as we increase in order. A more robust method is to implement the expressions in our paper directly, replacing the delta function by the Peskin version. Can this be included as a new feature in subgrid ?

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[ronojoy]

Hi Rupert

A hand may potentially become available in the next few weeks to do the implementation but she is not really up to speed on Python or Swig, so she'll need help from you to understand the internals. I think the new method will fit without too much change into the structure of the current code.

What we do now is to directly sum the flows, as we have their analytical forms, but then, we are restricted to simple domains like cubes. For other domains, its always nice to have an LB implementation!

Cheers,

Rjoy