Mixing and transport processes in environmental fluid systems: Gerhard Jirka’s scientific achievements

2012 ◽  
pp. 15-50
Keyword(s):  
Transport Processes ◽  
Fluid Systems ◽  
Environmental Fluid ◽  
Scientific Achievements ◽  
Mixing And Transport

A micromechanical investigation of interfacial transport processes. I. Interfacial conservation equations

1993 ◽  
Vol 345 (1675) ◽  
pp. 165-207 ◽  
Keyword(s):  
Mass Transfer ◽  
Asymptotic Expansion ◽  
Control Volume ◽  
Transport Processes ◽  
Matched Asymptotic Expansion ◽  
Immiscible Fluid ◽  
Conservation Equations ◽  
Interfacial Transport ◽  
Fluid Systems ◽  
Expansion Scheme

Macroscale interfacial conservation equations are derived for transport processes occurring in immiscible fluid—fluid systems possessing moving and deforming interfaces via a rigorous matched asymptotic expansion scheme from the more exact, continuous (‘diffuse’) microscale equations underlying them . A surface-fixed coordinate system is developed for the parameterization of the interface, alleviating approximations which result when either a material or a space-fixed control volume is used to investigate systems undergoing interphase mass transfer.

A micromechanical investigation of interfacial transport processes. II. Interfacial constitutive equations

1993 ◽  
Vol 345 (1675) ◽  
pp. 209-228 ◽  
Keyword(s):  
Constitutive Equations ◽  
Three Dimensional ◽  
Transversely Isotropic ◽  
Transport Processes ◽  
Interfacial Stress ◽  
Matched Asymptotic Expansion ◽  
Immiscible Fluid ◽  
Interfacial Transport ◽  
Fluid Systems ◽  
Phenomenological Coefficients

Macroscale interfacial constitutive equations, as well as expressions for the phenomenological functions appearing therein, are derived via a rigorous matched asymptotic expansion scheme for transport processes occurring in immiscible fluid—fluid systems possessing moving and deforming interfaces. The usefulness of an asymptotic approach is demonstrated by examining a model in which the three-dim ensional microscale fluid continuum is assumed to obey an incompressible, transversely-isotropic, linear, newtonian-type constitutive equation possessing position-dependent phenomenological coefficients which depend strongly upon distance normal to the interface. In such circumstances, them acroscale interfacial stress tensor reduces to the familiar isotropic Boussinesq-Scriven form . Similarly, a two-dimensional, isotropic, macroscale interfacial Fick’s law relation is derived from a comparable, three-dimensional, transversely-isotropic, microscale fickian form for the case of a diffusion-controlled surfactant transport exchange between the bulk phases and the interface.

Saturn's E, G and F rings: modulated by the plasma sheet

1984 ◽  
Vol 75 ◽  
pp. 597
Author(s):  
E. Grün ◽  
G.E. Morfill ◽  
T.V. Johnson ◽  
G.H. Schwehm
Keyword(s):  
Solar Wind ◽  
Direct Contact ◽  
Transport Processes ◽  
Time Variable ◽  
Dust Particles ◽  
Spatial Diffusion ◽  
Drag Forces ◽  
Orbit Perturbation ◽  
Time Variations ◽  
F Ring

ABSTRACTSaturn's broad E ring, the narrow G ring and the structured and apparently time variable F ring(s), contain many micron and sub-micron sized particles, which make up the “visible” component. These rings (or ring systems) are in direct contact with magnetospheric plasma. Fluctuations in the plasma density and/or mean energy, due to magnetospheric and solar wind processes, may induce stochastic charge variations on the dust particles, which in turn lead to an orbit perturbation and spatial diffusion. It is suggested that the extent of the E ring and the braided, kinky structure of certain portions of the F rings as well as possible time variations are a result of plasma induced electromagnetic perturbations and drag forces. The G ring, in this scenario, requires some form of shepherding and should be akin to the F ring in structure. Sputtering of micron-sized dust particles in the E ring by magnetospheric ions yields lifetimes of 102to 104years. This effect as well as the plasma induced transport processes require an active source for the E ring, probably Enceladus.

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