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Underlying Physics of Mixing Efficiency of Stably Stratified Turbulence.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Underlying Physics of Mixing Efficiency of Stably Stratified Turbulence./
Author:	Yi, Young Ro.
Description:	1 online resource (210 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
Contained By:	Dissertations Abstracts International84-12B.
Subject:	Motivation. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30462679click for full text (PQDT)
ISBN:	9798379653828

Underlying Physics of Mixing Efficiency of Stably Stratified Turbulence.
Yi, Young Ro.

Underlying Physics of Mixing Efficiency of Stably Stratified Turbulence. - 1 online resource (210 pages)

Source: Dissertations Abstracts International, Volume: 84-12, Section: B.

Thesis (Ph.D.)--Stanford University, 2023.

Includes bibliographical references

Global and regional ocean simulations rely on eddy viscosities and diffusivities to represent the unresolved turbulent mixing of momentum and scalars. The simulated flow and the transport of quantities such as heat and carbon are quite sensitive to how the turbulence is modeled. Particularly, the eddy diffusivity model of Osborn (1980) is widely used to represent the vertical buoyancy flux, which requires accurate knowledge of the mixing coefficient-defined as the ratio of the dissipation rates of available turbulent potential energy (TPE) and turbulent kinetic energy (TKE). While a constant value of 0.2 is often prescribed for the mixing coefficient, there is significant evidence for parameterizing it as a function of dimensionless numbers that characterize the state of the turbulence.Using direct numerical simulations, we studied stably stratified turbulence under three different sets of forcing: (i) linear axisymmetric forcing; (ii) three types of shear forcing; and (iii) combined momentum and buoyancy forcing. By analyzing the budgets of the normal Reynolds stresses and the vertical buoyancy flux, we observed that terms involving the pressure field (i.e., pressure-strain correlations and pressure scrambling) exhibited significant changes as the turbulent mixing became more efficient. Each of these three sets of flows exhibited quantitative physical differences in their mixing characteristics. Our findings suggested the need for improved models of the turbulent mixing in stratified flows, which we achieved by revising existing scaling relationships for the mixing coefficient and exploring anisotropic model forms for the turbulent momentum and scalar fluxes.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798379653828Subjects--Topical Terms:

532704
Motivation.
Index Terms--Genre/Form:

542853
Electronic books.

Underlying Physics of Mixing Efficiency of Stably Stratified Turbulence.
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100 1 $a Yi, Young Ro. $3 3704289
245 1 0 $a Underlying Physics of Mixing Efficiency of Stably Stratified Turbulence.
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300 $a 1 online resource (210 pages)
336 $a text $b txt $2 rdacontent
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500 $a Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
500 $a Advisor: Mani, Ali;Monismith, Stephen;Ouellette, Nicholas;Koseff, Jeffrey.
502 $a Thesis (Ph.D.)--Stanford University, 2023.
504 $a Includes bibliographical references
520 $a Global and regional ocean simulations rely on eddy viscosities and diffusivities to represent the unresolved turbulent mixing of momentum and scalars. The simulated flow and the transport of quantities such as heat and carbon are quite sensitive to how the turbulence is modeled. Particularly, the eddy diffusivity model of Osborn (1980) is widely used to represent the vertical buoyancy flux, which requires accurate knowledge of the mixing coefficient-defined as the ratio of the dissipation rates of available turbulent potential energy (TPE) and turbulent kinetic energy (TKE). While a constant value of 0.2 is often prescribed for the mixing coefficient, there is significant evidence for parameterizing it as a function of dimensionless numbers that characterize the state of the turbulence.Using direct numerical simulations, we studied stably stratified turbulence under three different sets of forcing: (i) linear axisymmetric forcing; (ii) three types of shear forcing; and (iii) combined momentum and buoyancy forcing. By analyzing the budgets of the normal Reynolds stresses and the vertical buoyancy flux, we observed that terms involving the pressure field (i.e., pressure-strain correlations and pressure scrambling) exhibited significant changes as the turbulent mixing became more efficient. Each of these three sets of flows exhibited quantitative physical differences in their mixing characteristics. Our findings suggested the need for improved models of the turbulent mixing in stratified flows, which we achieved by revising existing scaling relationships for the mixing coefficient and exploring anisotropic model forms for the turbulent momentum and scalar fluxes.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2023
538 $a Mode of access: World Wide Web
650 4 $a Motivation. $3 532704
650 4 $a Anisotropy. $3 596747
650 4 $a Viscosity. $3 1050706
650 4 $a Reynolds number. $3 3681436
650 4 $a Fluid mechanics. $3 528155
650 4 $a Mechanics. $3 525881
655 7 $a Electronic books. $2 lcsh $3 542853
690 $a 0204
690 $a 0346
710 2 $a ProQuest Information and Learning Co. $3 783688
710 2 $a Stanford University. $3 754827
773 0 $t Dissertations Abstracts International $g 84-12B.
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30462679 $z click for full text (PQDT)