Past Seminars Seminrios J Decorridos 2012

Particle hydrodynamics: beyond the Stokes force

By: Rafael Delgado-Buscalioni
From: Universidad Autnoma de Madrid
At: Instituto de Investigao Interdisciplinar, Anfiteatro
[2012-03-27] 11:30

I will  present "FLUAM", a new  algorithm designed  to  solve  the hydrodynamics of particles immersed  in a Newtonian solvent.  Although the scheme  is quite  general and can  be easily generalized  to solve dispersions  of   large  particles  (dust)   or  even  fluid-structure interactions, we  envisage applications at the  micron scale involving solutions of macromolecules (colloids  or polymeric chains).  At these scales  hydrodynamic fluctuations become  important and have to be consistently included in the fluid  solver. In particular, the Navier-Stokes-Landau-Lifshitz  equations  (for either    compressible   or    incompresible   liquids) are solved using a finite volume method [1].  Concering the solute description, at   this coarsed-grained level  I will focus on the  so called "point-particle" representation,  where each particle  (macromolecule) is  described by translational (also if required  rotational) degrees of freedom and of course might feel inter-molecular (effective potential) forces as well.

In these  kind of schemes, the  force between particle  and fluid have been usually assumed to be frictional, based on the Stokes drag.  This assumption   is  limitted   to   "slow"  fluid-particle   interactions developing at times much larger than the friction time (inverse of the friction coefficient).  By contrast, our approach is based on imposing a "no-slip"  constraint to the  fluid velocity at the  particle domain  which ensures that  particle and fluid momentum is instantaneously exchanged over their interaction [2,3].  In this way  we can tackle  phenomena occurring  at high  frequencies (such as  inertial effects). In  particular we  are interested  in applications  involving acoustic  forces [3]  (ultrasound) on colloidal  particles (and soft  matter, in  general).
Finally, I'd also like to briefly discuss some  of the applications we have in mind; such  as the  effect of  hydrodynamics  on the gelation process or in the self-assembly of patchy colloids.

[1] F. Balboa and J. Bell and R. Delgado-Buscalioniand A. Donev and T. Fai and B.  Griffit and C.  S. Peskin. Staggered Schemes  for Fluctuating Hydrodynamics, arXiv:1108.5188v1, (submitted, 2011)

[2] F.  Balboa  and R.  Delgado-Buscalioni,  Particle Hydrodynamics  using Hybrid Models:  from Molecular  to Colloidal Fluids,   Particles 2011 (to appear)

[3] F.  Balboa,  I.  Pagonabarraga  and  R.  Delgado-Buscalioni,  Inertial coupling  for point  particle  fluctuating hydrodynamics,  (submitted, J. Comp. Physics, 2011)