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Investigation of Fluid Transport in Non-Uniform Microchannels and Carbon Nanotubes.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Investigation of Fluid Transport in Non-Uniform Microchannels and Carbon Nanotubes./
作者:	Tao, Ran.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2020,
面頁冊數:	149 p.
附註:	Source: Dissertations Abstracts International, Volume: 83-01, Section: B.
Contained By:	Dissertations Abstracts International83-01B.
標題:	Fluid mechanics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28697786
ISBN:	9798534657630

Investigation of Fluid Transport in Non-Uniform Microchannels and Carbon Nanotubes.
Tao, Ran.

Investigation of Fluid Transport in Non-Uniform Microchannels and Carbon Nanotubes. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 149 p.

Source: Dissertations Abstracts International, Volume: 83-01, Section: B.

Thesis (Ph.D.)--Hong Kong University of Science and Technology (Hong Kong), 2020.

This item must not be sold to any third party vendors.

Flow motion in confinement is highly associated with characteristic dimensions. At the micro- and nanoscale, flows show diverse phenomena that have never been found at the macroscale. These diverse phenomena are owing to the surface force and electrokinetic effects as well as complex molecular interactions at a reduced characteristic length. Despite a great number of new phenomena and applications emerging at the nano/microscale, controversial results have been reported and many mechanisms still remain unclear, such as ionic concentration dependence in carbon nanotubes (CNTs). Therefore, extensive work is required to solve the existing problems and explore new phenomena. The objective of this thesis is to investigate the fluid flow in confined space at the micro- and nanoscale. First, fluid flows in converging-diverging microchannels (CDMCs) are studied. A new dimensionless number Gm is proposed to describe the geometry information of CDMCs. The product of the Gm and Reynolds number (Re) forms another dimensionless number, denoted by ReG (ReG = Re.Gm). ReG contains both the geometric influence and the competition between viscous and inertial effects, which is found to be more suitable for flow characterization in CDMCs. Flows stay laminar when Re 40 G < regardless of the geometry of the CDMCs. For laminar flows, the flow resistance model developed in the literature works well, but for transitional and turbulent flows, a scaling law is proposed in this thesis to estimate the flow resistance, which suggests a polynomial relationship between the pressure drop and flow rate. Second, a microfluidic rectifier for Newtonian fluids is fabricated by employing asymmetric converging-diverging microchannels (ACDMCs). Because of the asymmetric structure of the microchannel, the flow resistance depends on flow directions. The highest diodicity for this rectifier is 1.77, which is superior to previous microfluidic rectifiers for Newtonian fluids. An expression for the diodicity is developed based on two scaling laws for the flow resistances in the forward and backward directions. Third, experiments are conducted to study ion transport in carbon nanotubes. Various nonlinear relationships between the ionic conductance and the ion concentration are observed. Due to their small size and the chemical functionalization in the fabrication process, it is hypothesized that the distinct conductance-concentration (G-C) dependences are caused by the carboxylic acid groups at the CNT entrance, which could affect the energy barrier for ion transport and change the ionic conductance. Molecular dynamics simulations are performed to validate the hypothesis. The diverse G-C relationships are also predicted by the electrokinetic theory when we considered the potential generated by the functional groups at the CNT entrance. Practically, the number of functional groups at the CNT entrance is influenced by several factors, including both intrinsic and external effects, which make it difficult to regulate the ionic conductance. This poses a challenge for CNT-based nanofluidic systems in practical applications.

ISBN: 9798534657630Subjects--Topical Terms:

528155
Fluid mechanics.
Subjects--Index Terms:

Fluid flows

Investigation of Fluid Transport in Non-Uniform Microchannels and Carbon Nanotubes.
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245 1 0 $a Investigation of Fluid Transport in Non-Uniform Microchannels and Carbon Nanotubes.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2020
300 $a 149 p.
500 $a Source: Dissertations Abstracts International, Volume: 83-01, Section: B.
500 $a Advisor: Li, Zhigang.
502 $a Thesis (Ph.D.)--Hong Kong University of Science and Technology (Hong Kong), 2020.
506 $a This item must not be sold to any third party vendors.
520 $a Flow motion in confinement is highly associated with characteristic dimensions. At the micro- and nanoscale, flows show diverse phenomena that have never been found at the macroscale. These diverse phenomena are owing to the surface force and electrokinetic effects as well as complex molecular interactions at a reduced characteristic length. Despite a great number of new phenomena and applications emerging at the nano/microscale, controversial results have been reported and many mechanisms still remain unclear, such as ionic concentration dependence in carbon nanotubes (CNTs). Therefore, extensive work is required to solve the existing problems and explore new phenomena. The objective of this thesis is to investigate the fluid flow in confined space at the micro- and nanoscale. First, fluid flows in converging-diverging microchannels (CDMCs) are studied. A new dimensionless number Gm is proposed to describe the geometry information of CDMCs. The product of the Gm and Reynolds number (Re) forms another dimensionless number, denoted by ReG (ReG = Re.Gm). ReG contains both the geometric influence and the competition between viscous and inertial effects, which is found to be more suitable for flow characterization in CDMCs. Flows stay laminar when Re 40 G < regardless of the geometry of the CDMCs. For laminar flows, the flow resistance model developed in the literature works well, but for transitional and turbulent flows, a scaling law is proposed in this thesis to estimate the flow resistance, which suggests a polynomial relationship between the pressure drop and flow rate. Second, a microfluidic rectifier for Newtonian fluids is fabricated by employing asymmetric converging-diverging microchannels (ACDMCs). Because of the asymmetric structure of the microchannel, the flow resistance depends on flow directions. The highest diodicity for this rectifier is 1.77, which is superior to previous microfluidic rectifiers for Newtonian fluids. An expression for the diodicity is developed based on two scaling laws for the flow resistances in the forward and backward directions. Third, experiments are conducted to study ion transport in carbon nanotubes. Various nonlinear relationships between the ionic conductance and the ion concentration are observed. Due to their small size and the chemical functionalization in the fabrication process, it is hypothesized that the distinct conductance-concentration (G-C) dependences are caused by the carboxylic acid groups at the CNT entrance, which could affect the energy barrier for ion transport and change the ionic conductance. Molecular dynamics simulations are performed to validate the hypothesis. The diverse G-C relationships are also predicted by the electrokinetic theory when we considered the potential generated by the functional groups at the CNT entrance. Practically, the number of functional groups at the CNT entrance is influenced by several factors, including both intrinsic and external effects, which make it difficult to regulate the ionic conductance. This poses a challenge for CNT-based nanofluidic systems in practical applications.
590 $a School code: 1223.
650 4 $a Fluid mechanics. $3 528155
650 4 $a Mechanical engineering. $3 649730
650 4 $a Nanoscience. $3 587832
650 4 $a Simulation. $3 644748
650 4 $a Electrolytes. $3 656992
650 4 $a Flow velocity. $3 3564851
650 4 $a Experiments. $3 525909
650 4 $a Carbon. $3 604057
650 4 $a Electric fields. $3 880423
650 4 $a Equilibrium. $3 668417
650 4 $a Contact angle. $3 3320098
650 4 $a Reynolds number. $3 3681436
650 4 $a Boundary conditions. $3 3560411
650 4 $a Scanning electron microscopy. $3 551366
650 4 $a Micromachining. $3 1569477
653 $a Fluid flows
653 $a Carbon nanotubes
690 $a 0548
690 $a 0204
690 $a 0565
710 2 $a Hong Kong University of Science and Technology (Hong Kong). $3 1022235
773 0 $t Dissertations Abstracts International $g 83-01B.
790 $a 1223
791 $a Ph.D.
792 $a 2020
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28697786