Doctoral Dissertations

Keywords and Phrases

3D lattice geometries; Laser Doppler Velocimetry; turbulence generation

Abstract

"The relation between flow stream turbulence and heat transfer has been known for a long time, that the heat transfer rate is increased if the turbulence or fluctuation level of the flow increases. Open cell foams and compact heat exchangers are two of the most common models applied for heat transfer augmentation. However, the small ligaments of open cell foams limit the heat conducted and smooth passages in compact heat exchangers cannot cause flow unsteadiness. Accordingly, new geometric models are needed to improve the heat transfer enhancement. Three-dimensional (3D) lattice geometries with a range of features and sizes can be created using additive manufacturing (AM) techniques. The main objective of the study is to advance our understanding on the effect of geometric parameters on turbulence development in the perturbed flow field and with the aim of heat transfer enhancement.

To this end, we have studied the unsteady flow behaviors in the intermittent region of a turbulent jet without any perturbation, which gave us a better understanding of the flow development in the region of mixed turbulent/nonturbulent fluid. During the process, we modified the intermittency calculation method that was only suitable for hot wire anemometry (HWA) data so that it can be used with laser Doppler velocimetry (LDV) data. Then, we investigated the unsteady flow behaviors in the channel obstructed by different types of 3D lattice geometries. Distinct behaviors of the pressure distribution and the turbulence development were observed, which demonstrated that the turbulence development is strongly dependent on geometric properties. To reveal the effects of specific geometric features on flow behaviors, we presented an extensive study of the near-field turbulence development behind 3D lattice geometries by controlling the important geometric parameters. Our findings explain the unique flow behaviors observed in the second work and give improved insight into how geometric features of 3D lattice geometries influence unsteady flow behaviors in a turbulent channel"-- Abstract, p. iv

Advisor(s)

Homan, Kelly

Committee Member(s)

Bayless, David J.
Crosbie, A. L. (Alfred L.)
Drallmeier, J. A.
Mendoza, Cesar

Department(s)

Mechanical and Aerospace Engineering

Degree Name

Ph. D. in Mechanical Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2023

Pagination

xii, 99 pages

Note about bibliography

Includes_bibliographical_references_(pages 93-98)

Rights

© 2023 Yi Qiao, All Rights Reserved

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12297

Electronic OCLC #

1426307309

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