6 research outputs found
Dumbbell diffusion in a spatially periodic potential
We present a numerical investigation of the Brownian motion and diffusion of
a dumbbell in a two-dimensional periodic potential. Its dynamics is described
by a Langevin model including the hydrodynamic interaction. With increasing
values of the amplitude of the potential we find along the modulated spatial
directions a reduction of the diffusion constant and of the impact of the
hydrodynamic interaction. For modulation amplitudes of the potential in the
range of the thermal energy the dumbbell diffusion exhibits a pronounced local
maximum at a wavelength of about 3/2 of the dumbbell extension. This is
especially emphasized for stiff springs connecting the two beads.Comment: 4 pages, 7 figures, published in Phys. Rev. E (2008
The probability distribution of a trapped Brownian particle in plane shear flows
We investigate the statistical properties of an over-damped Brownian particle
that is trapped by a harmonic potential and simultaneously exposed to a linear
shear flow or to a plane Poiseuille flow. Its probability distribution is
determined via the corresponding Smoluchowski equation, which is solved
analytically for a linear shear flow. In the case of a plane Poiseuille flow,
analytical approximations for the distribution are obtained by a perturbation
analysis and they are substantiated by numerical results. There is a good
agreement between the two approaches for a wide range of parameters.Comment: 5 pages, 4 figur
Dynamics of a trapped Brownian particle in shear flows
The Brownian motion of a particle in a harmonic potential, which is
simultaneously exposed either to a linear shear flow or to a plane Poiseuille
flow is investigated. In the shear plane of both flows the probability
distribution of the particle becomes anisotropic and the dynamics is changed in
a characteristic manner compared to a trapped particle in a quiescent fluid.
The particle distribution takes either an elliptical or a parachute shape or a
superposition of both depending on the mean particle position in the shear
plane. Simultaneously, shear-induced cross-correlations between particle
fluctuations along orthogonal directions in the shear plane are found. They are
asymmetric in time. In Poiseuille flow thermal particle fluctuations
perpendicular to the flow direction in the shear plane induce a shift of the
particle's mean position away from the potential minimum. Two complementary
methods are suggested to measure shear-induced cross-correlations between
particle fluctuations along orthogonal directions.Comment: 14 pages, 7 figure