2011-05-18
10:15 at HCI J 574

Particle hydrodynamics based on hybrid methods

Rafael Delgado-Buscalioni

Universidad Autonoma de Madrid

This talk presents two types of multiscale methods to solve particle and fluid dynamics which combine different techniques in a concurrent way. Novel generalizations of type-B methods shall be presented.

Type A: Domain decomposition hybrids [1] can be designed to solve a certain domain of interest at fine detail -molecular dynamics (MD)- and connect it with a hydrodynamic description of the surrounding flow field. This approach is particularly suited for non-trivial or complex boundary conditions, which might contain singularities, interfaces or even macromolecules. At the interfase between coarse and fine models, the coupling might be based on fluxes or variable exchange. An unified framework is proposed.

Type B: Particle hydrodynamics involved in colloidal or polymeric suspensions or dispersions of larger particles are frequently solved using hybrid Eulerian-Lagrangian approaches whereby fluid flow is solved in an Eulerian mesh and particle motion is solved in the continuum space [2]. At low Reynolds number (typical of micro-devices) the Stokes drag is a good approximation to the fluid-particle force [2]. However, the Stokes limit is not valid in highly unsteady scenarios such as those encountered when manipulating micron-size particles using ultrasound. We present a generalisation inspired on a modification of the Immersed Boundary method [3] which obtains such force upon the imposition of no-slip at the particle center. The method [4] is simple to implement and it properly describes ultrasound forces, particle inertia and lubrication. Moreover, there is no dissipative channel related to particle friction (thus neither a “particle noise term” [2]); instead particle kinetic temperature is uniquely determined by transfer of fluid momentum fluctuations to the particle.

[1] G. De Fabritiis, R. Delgado-Buscalioni and P. Coveney, Phys. Rev. Lett 97, 134,501 (2006); R .Delgado-Buscalioni and G. De Fabritiis, Phys. Rev. E 76, 036709 (2007); R. Delgado-Buscalioni, K. Kremer and M. Praprotnik, J. Chem. Phys. 131, 244107 (2009)

[2] Tri T. Pham, et al. J. Chem. Phys. 131, 164114 (2009).

[3] Uhlmann, Phys. Fluids 20, 053305 (2008)

[4] F. Balboa Usabiaga and R. Delgado-Buscalioni, in preparation.