Re: [ESPResSo-users] Linking to external program

[Ulf Schiller]

Hello,

Regarding code coupling, you may wish to have a look at the tools that
were developed in the MAPPER project http://mapper-project.eu/, in
particular MPWide and MUSCLE. Furthermore, there will be a new project
starting in October, the ComPat project http://www.compat-project.eu/,
which deals with efficient multiscale computing patterns on emerging
exascale architectures. Since the project has not started yet, the web
page has no significant content yet, but it might be worthwhile to check
back in a few months. I am not sure whether anyone has tried to couple
ESPResSo tightly to other codes - there are certainly some loose
couplings around in the context of systematic coarse graining,  e.g.,
with GROMACS.

Regarding hydrodynamic interactions in ESPResSo, there is no universal
recipe, it depends on what you want to do. Note that the Oseen tensor
gives the instantaneous interactions and does not take into account the
finite propagation speed in the fluid. In ESPResSo, you could use either
dissipative particle dynamics (DPD) or the lattice Boltzmann method
(LBM) to calculate hydrodynamic interactions between particles. (I think
there may also be some sort of Stokesian dynamics available). Both DPD
and LBM will recover the retardation effect to some approximation, which
can have an effect on the dynamics of the system. For a comparison of
the LBM with Brownian dynamics, cf. http://dx.doi.org/10.1063/1.3251771
and http://dx.doi.org/10.1103/PhysRevE.82.011802.

Hope this helps,
Ulf

On 23/09/15 22:41, Andrew Jewett wrote:
> I hesitate to post this here.  I am currently a LAMMPS users, I might
> use ESPRESSO/ESPRESSO++ in the future.  So I hope someone else will
> reply with a more useful answer which is specific to ESPRESSO, because
> I'm curious too.
> 
> There is an effort to merge LAMMPS with OpenFOAM.  Here are some links:
> 
> http://lammps.sandia.gov/threads/msg34426.html
> http://www.cfdem.com/
> 
> Lastly, (just in case you weren't aware of this), in the low Reynolds
> number limit, assuming the fluid is at rest, you can include
> hydrodynamic effects efficiently using the Oseen tensor.  (See
> attached equations mostly stolen from Doi and Edwards.)  I am under
> the impression that ESPRESSO has the ability to do something like
> this.  (Hopefully someone else will comment.)
> 
> Forgive the post from someone who is somewhat ignorant of ESPRESSO.
> 
> Andrew
> 
> On Wed, Sep 23, 2015 at 10:58 AM, R C <address@hidden> wrote:
>> I would like to link an external program running in C or Fortran that
>> calculates hydrodynamic interaction forces based on particle positions from
>> ESPRESSO. The exchange would occur every few MD timesteps.
>>
>> I looked through the mail archives but did not see any related discussion.
>>
>> I would appreciate any suggestions in this regard.

-- 
Dr Ulf D Schiller
Centre for Computational Science
University College London
20 Gordon Street
London WC1H 0AJ
United Kingdom