Dear Allison,
I agree on your comment about giving a better definition to 'small
scale'. The turbulence closure models are derived from the primitive
equations via Reynolds decomposition, separating mean flow and random
fluctuations. Therefore I think that defining an upper length scale for
the turbulent fluctuations is not very straightforward. I guess in
practice the turbulent mixing length is used as a descriptive length scale.
Perhaps one solution could be to drop the "small scale" and stress the
random nature of turbulence instead:
"Turbulent kinetic energy" is the kinetic energy of chaotic turbulent
fluctuations of the flow ?
Tuomas Karna
Post-Doctoral Fellow
Center for Coastal Margin Observation and Prediction (CMOP)
Oregon Health and Science University
[email protected]
On 03/19/2013 05:32 AM, [email protected] wrote:
Dear Tuomas,
Thank you for working on the definitions. I take your point that 'turbulent'
does not necessarily mean 'subgrid scale'. I think your suggested text is
basically fine but it would be helpful if we could also include an upper limit
on what you mean by 'small'.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
NCAS/British Atmospheric Data Centre Email: [email protected]
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
-----Original Message-----
From: CF-metadata [mailto:[email protected]] On Behalf
Of Tuomas Karna
Sent: 15 March 2013 16:50
To: [email protected]
Subject: Re: [CF-metadata] standard names for ocean model turbulent
quantities
Dear Allison,
Thank you for your comments. I'd propose some further changes to the
definitions:
1. "specific_turbulent_kinetic_energy_of_sea_water (m2 s-2)"
As turbulent kinetic energy is not necessary equivalent to model's
subgrid scale eddy kinetic energy, I'd formulate the definition as:
' "Specific" means per unit mass. "Turbulent kinetic energy" is the
kinetic energy of small scale turbulent fluctuations of the flow. '
2. "specific_turbulent_kinetic_energy_dissipation_in_sea_water (W kg-1)"
The definition would then become:
' "Specific" means per unit mass. "Turbulent kinetic energy" is the
kinetic energy of small scale turbulent fluctuations of the flow. The
dissipation of kinetic energy arises in ocean models as a result of the
viscosity of sea water.'
3. "turbulent_mixing_length_of_sea_water (m)"
' "Turbulent mixing length" is used in models to describe the macro
length scale of energy-containing eddies in a turbulent flow. '
If these definitions seems too vague, I can try to elaborate them futher.
Best regards,
Tuomas Karna
Post-Doctoral Fellow
Center for Coastal Margin Observation and Prediction (CMOP)
Oregon Health and Science University
[email protected]
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