Fluctuating hydrodynamics

  • Fluctuating hydrodynamics for realistic liquid models

    • A good representation of mesoscopic fluids is required to complement molecular simulations at larger scales. However, computational models providing accurate and efficient description of hydrodynamics at the nanoscale are scarce, possibly because of the stochastic character of the underlaying flucutating hydrodynamics (FH) equations. Here, we derive a simple finite volume discretization over a regular grid of the compressible isothermal fluctuating hydrodynamics equations in the Eulerian reference system. We describe realistic fluids, such as argon at arbitrary densities and water (TIP3P model) at ambient conditions (T=300 K). To that end, molecular dynamics simulations are used to derive the required fluid properties: transport coefficients and pressure equation of state. The equilibrium state of the model is shown to be thermodynamically consistent and shown to correctly reproduce linear hydrodynamics (relaxation of sound and shear modes). We also consider non-equilibrium states involving diffusion and convection, in cavities with either slip or no-slip boundary conditions.

  • G. De Fabritiis, M. Serrano, R. Delgado-Buscalioni and P. V. Coveney , Fluctuating hydrodynamic modeling of fluids at the nanoscale, Phys. Rev. E, 75, 026307 (2007)

    • Coworkers: Gianni De Fabritiis

  • Fluctuating hydrodynamics in staggered grids

    • In collaboration with Aleks Donev and the group of Charles Peskin we have recently developed a third order Runge Kutta algorithm in a staggered grid to solve fluctuating hydrodynamics of ideal mixtures. Implementations for both compressible and incompressible fluids are now available.

    GPU solvers
    The algorithms have been written in CUDA to work in Graphical Processors Units. The computational efficiency has been sppeded up a factor 100 over single CPU processors.

  • Staggered Schemes for Fluctuating Hydrodynamics , F. Balboa, J. Bell, R. Delgado-Buscalioni, A. Donev, T. Fai, B. Griffith, C. S. Peskin (2011)
    • Coworkers:
    Florencio Balboa Usabiaga (UAM)
    Aleks Donev (Courant Institute of New York) ,

  • Open boundary conditions for fluctuating hydrodynamics


    • Non-reflecting boundary conditions (NRBC) are designed to evacuate sound waves out of the computational domain, thus allowing to deal with open systems and to avoid finite size effects associated with periodic boundaries . Thermodynamic consistency for the fluctuation of the total mass and momentum of the open system is ensured by a fluctuation-dissipation balance which controls the amplitude of the sound waves generated by stress fluctuations near the boundary. We consider equilibrium and out-of-equilibrium situations (forced sound) in liquid water at ambient conditions and argon ranging from gas to liquid densities. Non-reflecting boundaries for fluctuating hydrodynamics makes feasible simulations of ultrasound in microfluidic devices. The figure shows the power spectra of density waves in a simulation box with an oscillatory forcing at one point. Periodic boundaries (PBC) arecontaminated by spurious (eigen) modes of the box, while using NRBC, only the exicted wave appears. Coworer:
    Anne Dejoan (CIEMAT)

    Some papers
  • R. Delgado-Buscalioni, A. Dejoan, Non-reflecting boundaries for ultrasound in fluctuating hydrodynamics of open systems, Phys. Rev. E 78, 046708 (2008)