Brownian motion in a fluid in elongational flow
Brownian motion of a spherical particle in stationary elongational flow is studied. We derive the Langevin equation together with the fluctuation-dissipation theorem for the particle from nonequilibrium fluctuating hydrodynamics to linear order in the elongation-rate-dependent inverse penetration depths. We then analyze how the velocity autocorrelation function as well as the mean square displacement are modified by the elongational flow. We find that for times small compared to the inverse elongation rate the behavior is similar to that found in the absence of the elongational flow. Upon approaching times comparable to the inverse elongation rate the behavior changes and one passes into a time domain where it becomes fundamentally different. In particular, we discuss the modification of the t/sup -3/2/ long-time tail of the velocity autocorrelation function and comment on the resulting contribution to the mean square displacement. The possibility of defining a diffusion coefficient in both time domains is discussed.
- Research Organization:
- Universidad Autonoma de Barcelona, Bellaterra (Spain)
- OSTI ID:
- 6245709
- Journal Information:
- J. Stat. Phys.; (United States), Journal Name: J. Stat. Phys.; (United States) Vol. 53:1-2; ISSN JSTPB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BROWNIAN MOVEMENT
COLLOIDS
CONVECTION
CORRELATION FUNCTIONS
DIFFUSION
DISPERSIONS
ELONGATION
ENERGY TRANSFER
EQUATIONS
FLOW MODELS
FLUCTUATIONS
FLUID FLOW
FLUID MECHANICS
FRICTION FACTOR
FUNCTIONS
HEAT TRANSFER
HYDRODYNAMICS
LANGEVIN EQUATION
LOSSES
MASS TRANSFER
MATHEMATICAL MODELS
MECHANICS
PARTICLE MODELS
RELAXATION TIME
STATISTICAL MECHANICS
STOCHASTIC PROCESSES
VARIATIONS