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Author: Neeraj Nitin Sinai Borker
Publisher:
ISBN:
Category :
Languages : en
Pages : 198
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Book Description
This thesis concerns with the ability to change the properties of particle suspensions in a low Reynolds number simple shear flow over two orders of magnitude by designing shapes of the individual particles. The motion of particles such as rings with sharper outer edges, fibers with non-circular cross-sections or ramified particles can display unusual dynamics by small changes in their respective particle geometries. This work specifically focuses on particles that attain an equilibrium orientation without application of external forces or torques. Rheological properties of a suspension of such self-aligning particles (SAPs), such as intrinsic viscosity, hydrodynamic diffusivity and orientational dispersion, as a function of the particle aspect ratio display a phase transition-like behavior where the value of each of the rheological property drops by an order of magnitude near a critical aspect ratio A*. Using suspension of SAPs, rheological properties such as viscosity can be controlled by small changes in the particle aspect ratio; by adding a small number of tumbling particles to the suspension; or by varying the absolute particle, shear rate and/or the underlying fluid viscosity. This tunability of macroscopic properties of particle suspensions via passive control of the motion of its individual constituent particles opens new opportunities to fabricate functional materials with tunable properties using current processing flow technology such as injection molding or spin casting. A computationally inexpensive boundary element method for axisymmetric particles and a slender body theory accounting for cross-sectional effects on the force distribution of slender filaments, both in any linear flow fields, were developed as part of this thesis. These tools were used to obtain the motion of individual particles with exotic shapes. The suspension rheology was obtained through Brownian dynamics simulations and numerical calculations accounting for pairwise far-field hydrodynamic interactions and along with collisions. The shear rheology of rotating rings was also investigated to demonstrate its differences from the rheology of rotating fibers and discs. With the advancement in manufacturing techniques, self-aligning particle geometries can be accessed using fabrication methods such as 3D printing or lithography thereby allowing for experimental verification of our results and fabrication of functional materials.
Author: Neeraj Nitin Sinai Borker
Publisher:
ISBN:
Category :
Languages : en
Pages : 198
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Book Description
This thesis concerns with the ability to change the properties of particle suspensions in a low Reynolds number simple shear flow over two orders of magnitude by designing shapes of the individual particles. The motion of particles such as rings with sharper outer edges, fibers with non-circular cross-sections or ramified particles can display unusual dynamics by small changes in their respective particle geometries. This work specifically focuses on particles that attain an equilibrium orientation without application of external forces or torques. Rheological properties of a suspension of such self-aligning particles (SAPs), such as intrinsic viscosity, hydrodynamic diffusivity and orientational dispersion, as a function of the particle aspect ratio display a phase transition-like behavior where the value of each of the rheological property drops by an order of magnitude near a critical aspect ratio A*. Using suspension of SAPs, rheological properties such as viscosity can be controlled by small changes in the particle aspect ratio; by adding a small number of tumbling particles to the suspension; or by varying the absolute particle, shear rate and/or the underlying fluid viscosity. This tunability of macroscopic properties of particle suspensions via passive control of the motion of its individual constituent particles opens new opportunities to fabricate functional materials with tunable properties using current processing flow technology such as injection molding or spin casting. A computationally inexpensive boundary element method for axisymmetric particles and a slender body theory accounting for cross-sectional effects on the force distribution of slender filaments, both in any linear flow fields, were developed as part of this thesis. These tools were used to obtain the motion of individual particles with exotic shapes. The suspension rheology was obtained through Brownian dynamics simulations and numerical calculations accounting for pairwise far-field hydrodynamic interactions and along with collisions. The shear rheology of rotating rings was also investigated to demonstrate its differences from the rheology of rotating fibers and discs. With the advancement in manufacturing techniques, self-aligning particle geometries can be accessed using fabrication methods such as 3D printing or lithography thereby allowing for experimental verification of our results and fabrication of functional materials.
Author: Rajesh Kumar Mallavajula
Publisher:
ISBN:
Category :
Languages : en
Pages : 138
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Book Description
It is well known that the shape of particles is an important factor that determines the fluid flow behavior of suspensions. Interactions of cubic particles with one another and with the flow medium are unique because of their sharp edges, corners and flat surfaces. Using theory, simulations and experiments, the structure and flow properties of cube-shaped particles in suspension over a range of volume fractions is studied to understand the effect of shape on fluid structure and rheology. At very low volume fractions, the sharp edges and corners of cubes are found to profoundly alter the velocity field around the cube. The stresslet-strain relationship for a cube is anisotropic and depends on the orientation of the cube with respect to the velocity flow field. The effective viscosity of the suspension in a simple shear flow is obtained by computing the orientationaly averaged stresslet acting on cubes. These calculations yield a universal intrinsic viscosity, [[eta]] = 3.1 for sharp cubes, which is higher than the corresponding value for spheres [[eta]] = 5/2. Using the 2D velocity flow profile around sharp corners we further find that the pressure becomes singular near the edges of the cube, which results in the increased value of stress and hence the higher viscosity when compared with spherical particles. In the presence of an external torque acting on each cube, the orientation distribution is no longer isotropic. This can be achieved by using magnetic cubes in magnetic field. The general expression for the stress in a suspension of mag- netic cubes subjected to linear velocity field in presence of an external magnetic field is calculated. We find that the intrinsic viscosity for the weakly Brownian suspension in a simple shear flow can be varied between [[eta]] = 3.25 to [[eta]] = 5.5 by changing the strength and the direction of the applied magnetic field. At low to moderate volume fractions, Brownian dynamics simulations were carried out to study the structure and flow behavior of suspensions. Simulations were performed over a wide range of volume fractions and Pe to study its rheological properties. Our equilibrium results show that cubic particles behave like spheres interacting with a soft repulsion potential function for volume fractions less than 0.25. This soft repulsion potential captures the orientationally averaged excluded volume of the cubes and produces identical probability distributions as that of for cubes at very low volume fractions. For higher volume fractions, cubic particles starts to lose their orientational freedom resulting in the deviation of equilibrium properties from that of soft spheres. We also found that suspension of cubic particles when subjected to simple shear will produce higher viscosity when compared with spherical particles in suspensions with equivalent volume. We show that the suspension rheology in this regime can be discussed in terms of ordering and collisions among hard cubic particles. In order to gain insights from experiments, cubic particles of varying sizes (10nm to 5 micron sized cubes) and chemistries (PbT e, Fe3 O4 and MnCO3) were synthesized. Polymer brushes were also attached on the surfaces of PbT e and Fe3 O4 nanocubes to characterize the effect of particle surface chemistry on flow behavior. MnCO3 spherical particles of similar sizes as that of MnCO3 cubes were also synthesized and their suspension behavior studied to empirically characterize the effects of shape. A key result from this study is that irrespective of the cube size, size distribution, and surface chemistry, the intrinsic viscosity([[eta]]) for cube-shaped particles is [[eta]] = 3.1 ± 0.2 which agrees well with the value estimated from theory.
Author: Francisco Chinesta
Publisher: ISTE Press - Elsevier
ISBN: 9781785480362
Category : Science
Languages : en
Pages : 0
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Book Description
This book provides a review of the current understanding of the behavior of non-spherical particle suspensions providing experimental results, rheological models and numerical modeling. In recent years, new models have been developed for suspension rheology and as a result applications for nanocomposites have increased. The authors tackle issues within experimental, model and numerical simulations of the behavior of particle suspensions. Applications of non-spherical particle suspension rheology are widespread and can be found in organic matrix composites, nanocomposites, biocomposites, fiber-filled fresh concrete flow, blood and biologic fluids.
Author:
Publisher:
ISBN: 9780542458071
Category : Anisotropy
Languages : en
Pages :
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Book Description
Though suspensions comprised of anisotropic particles are ubiquitous in industry, little has been done to elucidate the effects of particle anisotropy on concentrated suspension rheology, or the mechanism responsible for the reversible shear thickening observed in these systems. This dissertation explores the rheology and shear-induced microstructure of anisotropic particle suspensions through the shear thickening transition, and provides the first account of anisotropic particle alignment during shear thickening. For this investigation, Poly(ethylene glycol) (PEG)-based suspensions of acicular precipitated calcium carbonate (PCC) particles of varying particle aspect ratio (nominal L/D & sim; 2, 4, 7) are generated that demonstrate both continuous and discontinuous reversible shear thickening with increasing applied shear rate or stress. The critical volume fraction for the onset of discontinuous shear thickening decreases as the average particle aspect ratio is increased. However, the critical stress for shear thickening is found to be independent of particle anisotropy and volume fraction, and can be predicted based on the minor axis dimension of the particles in agreement with the critical stress scaling for hard-sphere suspensions. Small angle neutron scattering during shear flow (Rheo-SANS) demonstrates that long-axis particle alignment with the flow direction is maintained throughout the range of shear stresses investigated, including the shear thickening regimes for both continuous and discontinuous shear thickening PCC/PEG suspensions. Investigations of particle flow alignment following flow cessation provide evidence that the critical volume fraction for shear thickening may be associated with an isotropic-nematic transition within the anisotropic particle suspensions. Rheo-SANS investigations of concentrated kaolin clay suspensions demonstrate that disk-shaped particles exhibit particle alignment with the face surfaces orthogonal to the gradient direction during both continuous and discontinuous shear thickening. The critical stress at the onset of shear thickening for discontinuous shear thickening clay suspensions is observed to scale with the particle thickness dimension. The rheology and Rheo-SANS observations for both the acicular PCC and disk-like kaolin clay suspensions invalidate earlier hypothesis suggesting that shear thickening behavior in anisotropic particle dispersions results from increased particle rotations out of flow alignment potentially leading to particle jamming. Rather, the observations suggest that shear thickening in anisotropic particle suspensions is a consequence of short range hydrodynamic lubrication forces resulting in the formation of hydroclusters at higher shear rates, analogous to the behavior established for spherical particle suspensions. Lastly, anisotropic particle suspensions are used to successfully develop of shear thickening fluid (STF)/ballistic fabric composites. Shape anisotropy imparts the advantage of lower solids loading required to achieve energy dissipative improvements compared to spherical particle STFs. The observed improvements in ballistic and stab resistance response of these composites over that of ballistic fabrics alone suggests that they could potentially be used in the development of personal body armors with improved, multi-threat protective capabilities.
Author: Jan Mewis
Publisher: Cambridge University Press
ISBN: 0521515998
Category : Science
Languages : en
Pages : 417
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Book Description
Presented in an accessible and introductory manner, this is the first book devoted to the comprehensive study of colloidal suspensions.
Author: Norman J. Wagner
Publisher: Cambridge University Press
ISBN: 1108423035
Category : Science
Languages : en
Pages : 437
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Book Description
Essential text on the practical application and theory of colloidal suspension rheology, written by an international coalition of experts.
Author: Christopher W. Macosko
Publisher: VCH Publishers
ISBN:
Category : Science
Languages : en
Pages : 576
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Book Description
Rheology: Principles, Measurements, and Applications will be of greatest interest to chemical engineers, chemists, polymer scientists, and mechanical engineers, as well as students in these and related fields.
Author: Yuji Matsuzaki
Publisher: SPIE-International Society for Optical Engineering
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 728
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Book Description
Proceedings of SPIE present the original research papers presented at SPIE conferences and other high-quality conferences in the broad-ranging fields of optics and photonics. These books provide prompt access to the latest innovations in research and technology in their respective fields. Proceedings of SPIE are among the most cited references in patent literature.
Author: Michael E. Aulton
Publisher: Elsevier Health Sciences
ISBN: 0702042900
Category : Medical
Languages : en
Pages : 909
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Book Description
"Pharmaceutics is the art of pharmaceutical preparations. It encompasses design of drugs, their manufacture and the elimination of micro-organisms from the products. This book encompasses all of these areas."--Provided by publisher.
Author: Jaap MJ den Toonder
Publisher: Royal Society of Chemistry
ISBN: 1849737096
Category : Technology & Engineering
Languages : en
Pages : 279
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Book Description
Cilia are tiny hairs covering biological cells to generate and sense fluid flow. Millions of years of evolution have inspired a novel technology which is barely a decade old. Artificial cilia have been developed to control and sense fluid flow in microscopic systems, presenting new and interesting options for flow control in lab-on-a-chip devices. This appealing link between nature and technology has seen rapid development in the last few years, and this book presents a review of the state-of-the-art in the form of a professional reference book. The editors have pioneered the field, having initiated a major European project on this topic soon after its inception. Active researchers in academia and industry will benefit from the comprehensive nature of this book, while postgraduates and those new to the field will gain a clear understanding of the theory, techniques and applications of artificial cilia.
