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Dynamics and Transport of Filaments and Elongated Particles in Fluid Flows.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Dynamics and Transport of Filaments and Elongated Particles in Fluid Flows./
作者:	Hu, Shi-Yuan.
面頁冊數:	1 online resource (153 pages)
附註:	Source: Dissertations Abstracts International, Volume: 83-10, Section: B.
Contained By:	Dissertations Abstracts International83-10B.
標題:	Fluid mechanics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28862370click for full text (PQDT)
ISBN:	9798426805293

Dynamics and Transport of Filaments and Elongated Particles in Fluid Flows.
Hu, Shi-Yuan.

Dynamics and Transport of Filaments and Elongated Particles in Fluid Flows. - 1 online resource (153 pages)

Source: Dissertations Abstracts International, Volume: 83-10, Section: B.

Thesis (Ph.D.)--New York University, 2022.

Includes bibliographical references

The dynamics and transport of finite-size particles or filaments in fluid flows is omnipresent in nature and is important in many industrial applications across a wide range of Reynolds numbers (Re), such as pumping and mixing fluid at low Re, sorting particles and filaments, modifying fluid mechanical or thermal transport properties with particles or filaments suspensions. For the transport of passive particles in fluid flows, a direct consequence of finite size is that the velocity of the particle is no longer determined locally by the flow velocity at a single point, but a result of the nonlocal sampling of the flow field surrounding the particle, leading to complex and chaotic particle dynamics, even in regular flows at low Re. On the other hand, the dynamics of suspended particles and filaments can modify the fluid flows and the related properties, in contrast to tracer particles.In Chapter 2 and Chapter 3, we first study the dynamics of passive filaments in Stokesian cellular vortical flows combining experiments and numerical simulations. The filaments are long enough to broadly sample the flow field. Using simulation, we find a surprising variety of long-time transport behavior in time-independent cellular flows-random walks, ballistic transport, and trapping-depending upon the filament's relative length and effective flexibility. Moreover, we find that filaments execute Levy walks whose diffusion exponents generally decrease with increasing filament length, until transitioning to Brownian walks. Lyapunov exponents likewise increase with length. Even completely rigid filaments, whose dynamics is finite dimensional, show a surprising variety of transport states and chaos. Fast filament dispersal is related to an underlying geometry of "conveyor belts". Evidence for these various transport states is found in experiments using arrays of counterrotating rollers, immersed in a fluid and transporting a flexible ribbon. In non-uniform chaotic flows, we find the rigid filaments are subdiffusive, also arising from the interplay between the filament's finite-extend geometry and the underlying flow structures. Our results may open up new possibilities for efficient dynamical sorting of elongated particles and semi-flexible biopolymers.In Chapter 4, we study the dynamics of actuated filaments in quiescent Stokesian fluid as a simple strategy for pumping fluid and building swimmers at low Re. More specifically, we model an elastic clamshell swimmer consisted of two flexible filaments with intrinsic curvature and the corresponding reduced-order models consisted of rigid filaments jointed by torsional springs and "torque limiting joint". The simplicity of the system allows us to fully explore the effect of various parameters on the swimming performance. Optimal included angles and elastoviscous numbers have been identified. The reduced-order models successively capture the characteristic dynamics of the elastic clamshell. We further demonstrate how the swimming performance can be significantly enhanced by the torque limiting joint. Our results may be useful for the development of efficient fluid pumping and artificial swimmers at low Re.In Chapter 5, we experimentally study the effect of suspended rod-like particles on the thermal transport properties of fluid in a turbulent Rayleigh-Benard convection, which is a simplified paradigm for thermal turbulent flows. The particles are centimeter-scale and made of polydimethylsiloxane. The particles are inertial due to their finite sizes and large thermal expansion coefficient, which is three times larger than that of the background fluid. This contrast makes the suspended particles lighter than the local fluid in hot regions and heavier in cold regions. The effect of particles' motion on fluid flows can be examined by comparing the measured Nusselt number and thermal fluctuations with and without particles. Both quantities can be estimated from the measured temperature time series by calibrated thermistors. We found that the heat transport is enhanced at relatively large Rayleigh number (Ra) but reduced at small Ra. The thermal fluctuations are found to decrease in the boundary layers and increase in the bulk. We demonstrate that the increase of Nu arises from the particle-boundary layer interactions: the particles act as "active" mixers of the flow and temperature fields across the boundary layers. Our results may shed light on a new approach to control the heat transport in thermal convection with suspensions of inertial particles without modification to the classical convection system.Chapter 2 is adapted from Phys. Rev. Lett. 127, 074503 (2021) by Shi-Yuan Hu, Jun-Jun Chu, Michael J. Shelley, and Jun Zhang; Chapter 4 is adapted from a preprint version prepared for the submission to Soft Matter (2021) by Shi-Yuan Hu, Jun Zhang, and Michael J. Shelley; Chapter 5 is adapted from J. Fluid Mech. 928, R1 (2021) by Shi-Yuan Hu, Kai-Zhe Wang, Lai-Bing Jia, Jin-Qiang Zhong, and Jun Zhang.

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

Mode of access: World Wide Web

ISBN: 9798426805293Subjects--Topical Terms:

528155
Fluid mechanics.
Subjects--Index Terms:

FilamentsIndex Terms--Genre/Form:

542853
Electronic books.

Dynamics and Transport of Filaments and Elongated Particles in Fluid Flows.
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500 $a Source: Dissertations Abstracts International, Volume: 83-10, Section: B.
500 $a Advisor: Zhang, Jun; Shelley, Michael J.
502 $a Thesis (Ph.D.)--New York University, 2022.
504 $a Includes bibliographical references
520 $a The dynamics and transport of finite-size particles or filaments in fluid flows is omnipresent in nature and is important in many industrial applications across a wide range of Reynolds numbers (Re), such as pumping and mixing fluid at low Re, sorting particles and filaments, modifying fluid mechanical or thermal transport properties with particles or filaments suspensions. For the transport of passive particles in fluid flows, a direct consequence of finite size is that the velocity of the particle is no longer determined locally by the flow velocity at a single point, but a result of the nonlocal sampling of the flow field surrounding the particle, leading to complex and chaotic particle dynamics, even in regular flows at low Re. On the other hand, the dynamics of suspended particles and filaments can modify the fluid flows and the related properties, in contrast to tracer particles.In Chapter 2 and Chapter 3, we first study the dynamics of passive filaments in Stokesian cellular vortical flows combining experiments and numerical simulations. The filaments are long enough to broadly sample the flow field. Using simulation, we find a surprising variety of long-time transport behavior in time-independent cellular flows-random walks, ballistic transport, and trapping-depending upon the filament's relative length and effective flexibility. Moreover, we find that filaments execute Levy walks whose diffusion exponents generally decrease with increasing filament length, until transitioning to Brownian walks. Lyapunov exponents likewise increase with length. Even completely rigid filaments, whose dynamics is finite dimensional, show a surprising variety of transport states and chaos. Fast filament dispersal is related to an underlying geometry of "conveyor belts". Evidence for these various transport states is found in experiments using arrays of counterrotating rollers, immersed in a fluid and transporting a flexible ribbon. In non-uniform chaotic flows, we find the rigid filaments are subdiffusive, also arising from the interplay between the filament's finite-extend geometry and the underlying flow structures. Our results may open up new possibilities for efficient dynamical sorting of elongated particles and semi-flexible biopolymers.In Chapter 4, we study the dynamics of actuated filaments in quiescent Stokesian fluid as a simple strategy for pumping fluid and building swimmers at low Re. More specifically, we model an elastic clamshell swimmer consisted of two flexible filaments with intrinsic curvature and the corresponding reduced-order models consisted of rigid filaments jointed by torsional springs and "torque limiting joint". The simplicity of the system allows us to fully explore the effect of various parameters on the swimming performance. Optimal included angles and elastoviscous numbers have been identified. The reduced-order models successively capture the characteristic dynamics of the elastic clamshell. We further demonstrate how the swimming performance can be significantly enhanced by the torque limiting joint. Our results may be useful for the development of efficient fluid pumping and artificial swimmers at low Re.In Chapter 5, we experimentally study the effect of suspended rod-like particles on the thermal transport properties of fluid in a turbulent Rayleigh-Benard convection, which is a simplified paradigm for thermal turbulent flows. The particles are centimeter-scale and made of polydimethylsiloxane. The particles are inertial due to their finite sizes and large thermal expansion coefficient, which is three times larger than that of the background fluid. This contrast makes the suspended particles lighter than the local fluid in hot regions and heavier in cold regions. The effect of particles' motion on fluid flows can be examined by comparing the measured Nusselt number and thermal fluctuations with and without particles. Both quantities can be estimated from the measured temperature time series by calibrated thermistors. We found that the heat transport is enhanced at relatively large Rayleigh number (Ra) but reduced at small Ra. The thermal fluctuations are found to decrease in the boundary layers and increase in the bulk. We demonstrate that the increase of Nu arises from the particle-boundary layer interactions: the particles act as "active" mixers of the flow and temperature fields across the boundary layers. Our results may shed light on a new approach to control the heat transport in thermal convection with suspensions of inertial particles without modification to the classical convection system.Chapter 2 is adapted from Phys. Rev. Lett. 127, 074503 (2021) by Shi-Yuan Hu, Jun-Jun Chu, Michael J. Shelley, and Jun Zhang; Chapter 4 is adapted from a preprint version prepared for the submission to Soft Matter (2021) by Shi-Yuan Hu, Jun Zhang, and Michael J. Shelley; Chapter 5 is adapted from J. Fluid Mech. 928, R1 (2021) by Shi-Yuan Hu, Kai-Zhe Wang, Lai-Bing Jia, Jin-Qiang Zhong, and Jun Zhang.
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650 4 $a Applied mathematics. $3 2122814
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653 $a Elongated particles
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