Stellar mixing. II. Double diffusion processes

Details Stellar mixing. II. Double diffusion processes Stellar mixing. II. Double diffusion processes

Apr 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011a%26a...528a..77c&link_type=abstract

Astronomy & Astrophysics, Volume 528, id.A77

Astronomy and Astrophysics

Astrophysics

1

Turbulence, Diffusion, Convection, Hydrodynamics, Methods: Analytical, Stars: Rotation

Scientific paper

In this paper, salt - fingers (also called thermohaline convection) and semi-convection are treated under the name of double - diffusion (DD). We present and discuss the solutions of the RSM (Reynolds stress models) equations that provide the momentum, heat, μ fluxes, and their corresponding diffusivities denoted by Km,h,μ. Such fluxes are given by a set of linear, algebraic equations that depend on the following variables: mean velocity gradient (differential rotation), temperature gradients (for both stable and unstable regimes), and μ-gradients (DD). Some key results are as follows. Salt - fingers. When shear is strong and DD is inefficient, heat and μ diffusivities are identical. Second, when shear is weak Kμ > Kh and the difference can be sizeable O(10) meaning that heat and μ diffusivities must therefore be treated as different. Third, for strong-to-moderate shears and for Rμ less than 0.8, both heat and μ diffusivities are practically independent of Rμ. Fourth, the latter result favors parameterizations of the type Kh, μ ˜ CR_μ^0 suggested by some authors. Our results, however, show that C is not a constant but a linear function of the Reynolds number Re = ɛ(νN2)-1 defined in terms of the kinematic viscosity ν, the Brunt-Väisälä frequency N, and the rate of energy input into the system, ɛ. Fifth, we suggest that ɛ is an essential ingredient that has been missing in all diffusivity models, but which ought to be present because without a source of energy, turbulence dies out and so does the turbulent mixing (for example, the turbulent kinetic energy is proportional to the power 2/3 of ɛ). Moreover, since different stellar environments have different ɛ, its presence is necessary for differentiating mixing regimes in different stars. Semi - convection. In this case the destabilizing effect is the T-gradient, and when shear is weak, Kh > Kμ. Since the model is symmetric under the change Rμ to R_μ -1, most of the results obtained in the previous case can be translated to this case.
This work is dedicated to Aura Sofia Canuto.

Affiliated with

Also associated with

No associations

Rating

Stellar mixing. II. Double diffusion processes does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Stellar mixing. II. Double diffusion processes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stellar mixing. II. Double diffusion processes will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1183467