Enhancement of passive diffusion and suppression of heat flux in a fluid with time-varying shear
Diffusion and heat conductivity within stars are shown to be substantially affected by fluid shear motions, even when these motions do not mix fluid elements (i.e., even when no fluid element wanders far from its equilibrium position). Internal gravity waves (g-modes) are one example of such a nonmixing flow. A formalism, based on Lagrangian flow coordinates, is developed to describe the effect in Boussinesq approximation. The diffusion of passive contaminants and of specific entropy is found to be generally enhanced, while the conduction of heat in stably stratified layers is suppressed (the fluid motions power a thermodynamic refrigerator). explicit formulae are derived for flows which can be approximated as having spatially constant velocity gradients, and also for interval gravity waves. In the latter case the mechanical dissipation and thermodynamic efficiencies are calculated.
- Research Organization:
- Harvard-Smithsonian Center for Astrophysics
- OSTI ID:
- 5884522
- Journal Information:
- Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 248:2; ISSN ASJOA
- Country of Publication:
- United States
- Language:
- English
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640104 -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DIFFERENTIAL EQUATIONS
DIFFUSION
ENTROPY
EQUATIONS
FLUID FLOW
FLUID MECHANICS
GRAVITY WAVES
HEAT FLUX
HYDRODYNAMICS
LAGRANGE EQUATIONS
MAIN SEQUENCE STARS
MECHANICS
PARTIAL DIFFERENTIAL EQUATIONS
PHYSICAL PROPERTIES
RADIATION TRANSPORT
SHEAR
STARS
SUN
THERMAL CONDUCTIVITY
THERMODYNAMIC PROPERTIES