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Numerical simulations of stably stratified turbulent flow

Record Type:	Electronic resources : Monograph/item
Title/Author:	Numerical simulations of stably stratified turbulent flow
Author:	Shih, Lucinda H.
Description:	198 p.
Notes:	Adviser: Jeffrey R. Koseff.
Notes:	Source: Dissertation Abstracts International, Volume: 64-11, Section: B, page: 5707.
Contained By:	Dissertation Abstracts International64-11B.
Subject:	Engineering, Environmental.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3111791
ISBN:	0496593218

Numerical simulations of stably stratified turbulent flow
Shih, Lucinda H.

Numerical simulations of stably stratified turbulent flow [electronic resource] - 198 p.

Adviser: Jeffrey R. Koseff.

Thesis (Ph.D.)--Stanford University, 2004.

A parallel large eddy simulation (LES) code for stratified channel flow is used to study processes significant in the near-coastal ocean. As expected, weakly stratified flows are quickly mixed by bottom-generated turbulence, while stronger thermoclines suppress the growth of turbulent structures. Turbulence in the freestream portion of the channel flow behaves similarly, albeit not identically, to turbulence in homogeneous shear flow. Langmuir circulations are simulated in the stratified channel flow via the Craik-Leibovich vortex forcing mechanism. The added vortex forcing accelerates surface mixed layer deepening, moderated by increased stratification, and is important for realistic modeling of vertical mixing in surface waters.

ISBN: 0496593218Subjects--Topical Terms:

212478
Engineering, Environmental.

Numerical simulations of stably stratified turbulent flow
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245 1 0 $a Numerical simulations of stably stratified turbulent flow $h [electronic resource]
300 $a 198 p.
500 $a Adviser: Jeffrey R. Koseff.
500 $a Source: Dissertation Abstracts International, Volume: 64-11, Section: B, page: 5707.
502 $a Thesis (Ph.D.)--Stanford University, 2004.
520 # $a A parallel large eddy simulation (LES) code for stratified channel flow is used to study processes significant in the near-coastal ocean. As expected, weakly stratified flows are quickly mixed by bottom-generated turbulence, while stronger thermoclines suppress the growth of turbulent structures. Turbulence in the freestream portion of the channel flow behaves similarly, albeit not identically, to turbulence in homogeneous shear flow. Langmuir circulations are simulated in the stratified channel flow via the Craik-Leibovich vortex forcing mechanism. The added vortex forcing accelerates surface mixed layer deepening, moderated by increased stratification, and is important for realistic modeling of vertical mixing in surface waters.
520 # $a Analysis of the homogeneous shear flow data shows that the Osborn (1980) prediction for turbulent diffusivity kapparho as a function of epsilon/(nuN2), a traditional oceanography parameter measuring turbulence intensity, can be modified to extend its validity from the flow regime where turbulence is stationary to a more energetic regime of growing turbulence. This result holds for laboratory data from higher Prandtl number experiments as well. Furthermore, scaling shows that epsilon/(nu N2) is equivalent to a combination of Reynolds and Froude number Re/Fr2, with the latter parameterization rendering more distinct the effects of viscosity and stratification; given the Reynolds number independence of high Reynolds number flows, the turbulent diffusivity can then be expressed as a function of Froude number alone.
520 # $a Direct numerical simulations (DNS) of stratified homogeneous turbulence reveal that final states of turbulence vary with initial shear rate at low but not high Reynolds numbers, indicating the importance of employing instantaneous rather than initial values when parameterizing flow. Also, while it may be more convenient to use a global parameter such as the gradient Richardson number to characterize stratification for modeling purposes, a local, temporally-evolving parameter such as the turbulent Froude number is more illustrative of physical flow processes.
520 # $a Insights from detailed numerical simulations of idealized geophysical flows can be used to inform laboratory or field studies, as well as parameterizations of turbulence closure for more general ocean or atmosphere models. To this end, two basic types of stratified flow are numerically modeled in this study.
590 $a School code: 0212.
650 # 0 $a Engineering, Environmental. $3 212478
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790 1 0 $a Koseff, Jeffrey R., $e advisor
791 $a Ph.D.
792 $a 2004
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