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Statistics and turbulent structures of passive scalar transport in free surface flows.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Statistics and turbulent structures of passive scalar transport in free surface flows./
作者:	Khakpour, Hamid Reza.
面頁冊數:	1 online resource (159 pages)
附註:	Source: Dissertations Abstracts International, Volume: 75-11, Section: B.
Contained By:	Dissertations Abstracts International75-11B.
標題:	Geophysical. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3579512click for full text (PQDT)
ISBN:	9781303769962

Statistics and turbulent structures of passive scalar transport in free surface flows.
Khakpour, Hamid Reza.

Statistics and turbulent structures of passive scalar transport in free surface flows. - 1 online resource (159 pages)

Source: Dissertations Abstracts International, Volume: 75-11, Section: B.

Thesis (Ph.D.)--The Johns Hopkins University, 2012.

Includes bibliographical references

Direct numerical simulation (DNS) is performed to study the transport of passive scalars in free surface turbulent flows. First, coherent vortical structures responsible for strong scalar flux at the free surface are identified using conventional conditional averaging of events with strong scalar surface flux or large vorticity components. I characterize the correlation of surface flux with a variety of subsurface vortical structures. I present a recently proposed clustering method based on the expectation-maximization (EM) algorithm which has been shown to be effective in identifying dominant turbulence structure patterns associated with strong scalar surface flux. Using this method, clustering modes are obtained in terms of the instantaneous surface fields of scalar flux together with vorticity distributions on two perpendicular vertical planes. These clustering results for flow patterns corresponding to different characteristic vortical structures are consistent with the instantaneous and conditionally-averaged flow fields, and are further supported by spatial cross-correlation and probability analysis. I also investigate the relationships between the vortical structures obtained by clustering analysis and the enstrophy-containing eigenvectors obtained by proper orthogonal decomposition (POD). It is noted that, compared with the POD eigenvectors, the clustering modes have a more direct correspondence to the turbulence structures in physical space. Using the proposed clustering method, we analyse three canonical flows of free-surface turbulence. For open-channel flow, ring-like and asymmetric cane vortices are shown to be the dominant vortical structures related to strong scalar surface flux; for freely-evolving shear flow, upward and downward hairpin vortices are the main structures; and for flow driven by a surface stress, the main structures are in the form of a staggered array of quasi-streamwise vortices. The clustering method is general and can also be used for applications beyond interfacial scalar transport. Second, I employ Hybrid Lagrangian Tracing and Temperature (HLTT) method to quantify the surface age of surface fluid particles, i.e. the time elapsed since the last surface renewal they experienced. Using information obtained by subsurface turbulent structures and surface age distribution, I characterize the surface renewal time scale, which is a key parameter in predicting turbulent scalar surface flux.

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

Mode of access: World Wide Web

ISBN: 9781303769962Subjects--Topical Terms:

3558641
Geophysical.
Subjects--Index Terms:

DNSIndex Terms--Genre/Form:

542853
Electronic books.

Statistics and turbulent structures of passive scalar transport in free surface flows.
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