Nanoparticle stochastic motion in the inertial regime and hydrodynamic interactions close to a cylindrical wall.
We have carried out direct numerical simulations (DNS) of the fluctuating Navier-Stokes equation together with the particle equations governing the motion of a nanosized particle or nanoparticle (NP) in a cylindrical tube. The effects of the confining boundary, its curvature, particle size, and particle density variations have all been investigated. To reveal how the nature of the temporal correlations (hydrodynamic memory) in the inertial regime is altered by the full hydrodynamic interaction due to the confining boundaries, we have employed the Arbitrary Lagrangian-Eulerian (ALE) method to determine the dynamical relaxation of a spherical NP located at various positions in the medium over a wide span of time scales compared to the fluid viscous relaxation timeτv=a2/v, whereais the spherical particle radius andvis the kinematic viscosity. The results show that, as compared to the behavior of a particle in regions away from the confining boundary, the velocity autocorrelation function (VACF) for a particle in the lubrication layer initially decays exponentially with a Stokes drag enhanced by a factor that is proportional to the ratio of the particle radius to the gap thickness between the particle and the wall. Independent of the particle location, beyond time scales greater thana2/v, the decay is always algebraic followed by a second exponential decay (attributed to the wall curvature) that is associated with a second time scaleD2/v, whereDis the vessel diameter.
Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA, USA.
Helena
H
Vitoshkin
Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA, USA.
Hsiu-Yu
HY
Yu
Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA; Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, PA, USA.
David M
DM
Eckmann
Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA, USA.
Portonovo S
PS
Ayyaswamy
Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA, USA; Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA.
Ravi
R
Radhakrishnan
cylindrical vessel; hydrodynamic interaction; nanoparticle motion; wall effect