Academic literature on the topic 'Vortex mixer'

Achieving rapid mixing of different liquids in a short distance is important in various biochemical applications. Herein, a novel planar mixer with staggered Z-shaped baffles is proposed. Numerical investigations are carried out to evaluate its mixing ability based on mixing quality and pressure drop when the Reynolds number (Re) varies from 0.1 to 50. The Lyapunov exponent, the Poincaré map, and the vortex visualization are conducted to comprehensively analyze the chaotic state and the mixing mechanism. Results show that the proposed mixer exceeds 0.9 mixing efficiency when 0.1 ≤ Re and Re ≥ 8. As Re ≥ 8, different vortex patterns appear by changing the inlet configuration. The disturbance for fluids induced by a vortex on the mass transfer surface is not only dependent on its intensity but also related to the position of the vortex/vortex leg. The proposed planar mixer, inducing a single vortex or vortex pair with different directions, presents different mixing performance when the Re varies from 8 to 50, from which the approach of the rotating vortex that can mainly improve the mixing quality is found. This well explains the chaotic mixing behavior observed in the planar mixer with Z-shaped baffles, which to date has not been studied before. Furthermore, the micromixer is fabricated, tested, and applied for luminol–peroxide chemiluminescence detection to characterize its performance.

A new cross-channel split-and-recombine (CC-SAR) micro-mixer was proposed, and its performance was demonstrated numerically. A numerical study was carried out over a wide range of volume flow rates from 3.1 μL/min to 826.8 μL/min. The corresponding Reynolds number ranges from 0.3 to 80. The present micro-mixer consists of four mixing units. Each mixing unit is constructed by combining one split-and-recombine (SAR) unit with a mixing cell. The mixing performance was analyzed in terms of the degree of mixing and relative mixing cost. All numerical results show that the present micro-mixer performs better than other micro-mixers based on SARs over a wide range of volume flow rate. The mixing enhancement is realized by a particular motion of vortex flow: the Dean vortex in the circular sub-channel and another vortex inside the mixing cell. The two vortex flows are generated on the different planes perpendicular to each other. They cause the two fluids to change their relative position as the fluids flow into the circular sub-channel of the SAR, eventually promoting violent mixing. High vorticity in the mixing cell elongates the flow interface between two fluids, and promotes mixing in the flow regime of molecular diffusion dominance.

Abstract. This paper presents a new type of adjustable mixing equipment, and the internal flow field of the adjustable mixer have been studied by using the model of LES(Large eddy simulation),and the pressure loss, the speed change and vortex scale have been studied. In conclusion, along with blades angle and number increases, the flow resistance increases violently, so the range of blade rotating angle should be controlled within 30 degrees. As the depth of the pipeline velocity is increasingly large, large velocity gradient is contributed to the collisions between the colloidal particles. In pre-mixed, the vortex effect of the pipeline highly enhances the vortex diffusion, and improves the mixing efficiency. The vortex strength will be reinforced and dimension will be reduced, with the vanes cutting the flow, which can help flocculation.

An experimental study was conducted to investigate the mixing processes downstream of a forced mixer. A forced mixer generates large-scale, axial (stirring) vorticity, which causes the primary and secondary flow to mix rapidly with low loss. These devices have been successfully used in the past where enhanced mixing of two streams was a requirement. Unfortunately, details of the mixing process associated with these lobed forced mixers are not well understood. Performance sensitivity to design variables has not been documented. An experiment was set up to investigate the mixing processes downstream of a mixer. Air flow was independently supplied to each side of the forced mixer by separate centrifugal blowers. Pressures were measured at the entrance to the lobes with a pitot-static probe to document the characteristics of the approaching boundary layer. Interior mean and fluctuating velocities were nonintrusively measured using a two-component laser-Doppler velocimetry (LDV) system for velocity ratios of 1:1 and 2:1. The wake structure is shown to display a three-step process where initially secondary flow was generated by the mixer lobes, the secondary flow created counterrotating vortices with a diameter on the order of the convolute width, and then the vortices broke down resulting in a significant increase in turbulent mixing. The results show that the mean secondary motion induced by the lobes effectively circulated the flow passing through the lobes. This motion, however, did not homogeneously mix the two streams. Turbulent mixing in the third step of the mixing process appears to be an important element in the enhanced mixing that has been observed with forced mixers. The length required for the flow to reach this third step is a function of the velocity ratio across the mixer. The results of this investigation indicate that both the mean secondary motion and the turbulent mixing occurring after vortex breakdown need to be considered for prediction of forced mixer performance.

The impinging streams mixer is a new type micromixer. The cavitation phenomenon occurring in the mixers with T-shaped impinging streams (TS), conical impinging streams (CIS), vortex streams(VS) were investigated, respectively. The distribution of flow field in the mixer was simulated and calculated by commercial software Fluent 6.2.1. The results showed that under the same working conditions, a more obvious hydrodynamic cavitation may occur in the CIS type impinging stream than that in the CIS type or the VS type, and the vortex flow lead to an extension of the material residence time in the mixer. The distribution of turbulent kinetic energy and gas holdup were obtained by numerical simulating hydrodynamic cavitation under different entrance pressure conditions. It is showed that when the outlet pressure keeps a constant value, hydrodynamic cavitation can be enhanced by increasing the entrance pressure. The above research can be contributed to the producing of biodiesel and the solving of the key technical problem of oil and alcohol heterogeneous mixing.

This paper proposes a mixer with an elastic vortex generator consisting of a branched elastic flag connected to the rear of a cylinder in the mixing channel and studies the effects of the branching angle of the branching elastic flag and Reynolds number based on the cylinder diameter Red on the mixing modes of the fluid flow in the mixer. One free diffusion-induced mixing mode and two different vortex-induced mixing modes are found, and a phase diagram regarding the mixing modes of the fluid flow behind the elastic vortex generator is established. It is found that the elastic vortex generator is helpful for the transition of the mixing mode from free diffusion-induced mixing to vortex-induced mixing with the increasing branching angle. Furthermore, the rising Reynolds number results in the transition of mixing mode from free diffusion-induced mixing to vortex-induced mixing. In addition, the present work quantitatively studies the effects of the branching angle of the branched elastic flag and Reynolds number on the pressure loss and the outlet mixing efficiency of the mixer. It is found that the increase in pressure loss and the outlet mixing efficiency are 141.41% and 613.70% as the branching angle increases from 0° to 180° when Red = 90. In addition, the pressure loss and outlet mixing efficiency of the mixer with the branched elastic flag of branching angle θ = 180° can be 227.66% and 601.36% higher than those of the fluid flow around the cylinder without the elastic flag in the mixing channel when Red = 50.

Superparamagnetic nanoparticles have potential applications in targeted drug delivery and as magnetic resonance imaging contrast agents. Magnetite clusters are of particular interest for these applications because they provide higher magnetic flux (under a magnetic field) than individual magnetite nanoparticles, are biocompatible, and their size and compositions can be controlled. This thesis involves the controlled synthesis and characterization of clusters composed of magnetite nanoparticles stabilized with an amphiphilic block copolymer. It outlines a method to design and form well-defined and colloidally stable magnetite clusters. A Multi Inlet Vortex mixer (MIVM) was used because it is a continuous process that yields particles with relatively narrow and controlled size distributions. In the MIVM, four liquid streams collide under turbulent conditions in the mixing chamber where clusters form within milliseconds. The formation of magnetite clusters was studied in the presence of amphiphilic block copolymers containing poly (ethylene oxide) to provide steric stabilization and control of size distributions using flash nanoprecipitation. First, the mixer was tested using β-carotene as a model compound to form nanoparticles stabilized with an amphiphilic triblock copolymer poly(propylene oxide)-b-poly(ethylene oxide) (F127) at different Reynolds numbers and supersaturation values. Size analysis was done using dynamic light scattering and nanoparticle tracking analysis techniques. The cluster structure was studied using electron microscopy and magnetite compositions were measured using thermogravimetric analysis. Finally, the stability of magnetite clusters was studied over time and the effect of an applied magnetite field on the colloidal stability was investigated.
Master of Science

Ce travail de these consiste a etudier de facon detaillee et quantitative, la reponse d'un supraconducteur soumis a un champ hyperfrequence, en presence d'un champ magnetique statique module a basse frequence. Celle-ci est etudiee avec un spectrometre de r. P. E. Et nous montrons qu'elle est due aux vortex ayant penetre dans le materiau. Les observations effectuees sur des couches minces de supraconducteurs classiques de plomb et de nitrure de niobium, ainsi que sur des couches minces de supraconducteur a haute temperature critique de 9ba#2cu#3o#7#x revelent que l'impedance de surface complexe de l'echantillon devient tres non lineaire avec le champ magnetique, au voisinage de la temperature critique tc. La resistance de surface est modulee aux frequences multiples paires de la frequence du champ magnetique modulant. Une etude systematique du contenu harmonique de cette reponse non lineaire en fonction de la temperature, du champ magnetique statique, de l'amplitude de la modulation, de la puissance microonde incidente, de l'orientation de l'echantillon par rapport au champ magnetique est presentee. L'interpretation de ces resultats est basee sur le modele de bean de l'etat critique

Nous avons mis au point une cellule de décoration, permettant de décorer les vortex à basse température (jusqu'à 1.6K) sous faible champ magnétique (jusqu'à 0.2mT). La méthode est basée sur l'interaction des gradients de champs dus aux vortex avec des particules ferromagnétiques fabriquées in-situ dans un gaz résiduel. Après réchauffement, l'observation des amas de nickel se fait sous le microscope électronique à balayage. Les échantillons étudiés sont des réseaux 2D submicroniques de fils en niobium (pas du réseau 1-2 µm, largeur des fils 0.3 µm, épaisseur 0.2 µm) avec d'excellentes propriétés supraconductrices (température de transition 9.0K, RRR d'environ 30). Notre calcul de profil de champ magnétique au-dessus d'un réseau montre que le contraste entre cellules avec ou sans vortex est extrêmement faible. Suivant la hauteur au dessus du réseau, nous décorons soit les courants soit les milieux de cellules. La décoration se fait donc sur des réseaux planarisés, à des températures T<

Les effets de quantification du flux magnetique sur des reseaux supraconducteurs bidimensionnels sont etudies dans ce memoire. Du point de vue theorique, la temperature de transition supraconductrice en fonction du champ magnetique applique est determinee en resolvant les equations d'alexander pour divers reseaux : periodiques, quasiperiodiques et fractals. Quelques un de ces reseaux submicroniques ont ete realises par lithographie electronique. Leurs temperatures critiques sont mesurees et l'accord entre la theorie et l'experience est discute. A l'interieur de la phase supraconductrice, les vortex entrent dans le reseau et induisent des supercourants diamagnetiques. L'etat d'equilibre est traite d'une maniere analogue au traitement de l'etat mixte d'un supraconducteur massif d'abrikosov : on determine l'amplitude du parametre d'ordre en tenant compte du terme non-lineaire de l'equation de ginzburg-landau par une methode de perturbation. On en deduit les quantites thermodynamiques, en particulier l'energie libre et l'aimantation du reseau, qui sont des fonctions de la difference entre la temperature et la temperature critique t - t::(c), ainsi que du parametre d'abrikosov beta ::(a). Ce formalisme a ete applique au reseau carre pour lequel les configurations du parametre d'ordre et les distributions du courant diamagnetique ont ete determinees pour quelques valeurs simples du champ magnetique. D'autre part, la derivee de la ligne critique par rapport au champ magnetique, qui s'identifie a la derivee du bord du spectre d'hofstadter a ete calculee a l'aide d'une approximation continue. Cette derivee contient un terme anormal que l'on peut relier a la phase de berry. Elle donne directement la derivee de l'aimantation par rapport a la temperature d rond m/d rond t. Nous donnons egalement quelques resultats preliminaires sur l'etat mixte du reseau supraconducteur en presence d'un courant exterieur. Le courant critique au-dessus duquel cet etat n'existe plus est obtenu pour quelques cas simples (boucles, reseau carre). Quelques mesures preliminaires de ce courant ont ete effectuees sur un reseau carre

碩士
國立臺北科技大學
能源與冷凍空調工程系碩士班
100
Effective mixing is vitally important to many microfluidic devices in the areas of biotechnical industries, analytic chemistry and medical industries. However, most micro-mixers require complicated fabrication procedures, maybe improper for practical microfluidic utilization. These mixers generally operate under low Reynolds-number conditions, causing a relatively long reaction time in various biochemical processes. This study presents a novel hemisphere-shaped vortex mixer to rapidly mix two liquids with simple geometric structure. To simulate mixing behavior, computational analysis is based on the transient three-dimensional conservation equations of mass, momentum and species concentration. The liquids are treated as laminar, incompressible, miscible, uniform-property flows with insignificant gravity and temperature variation effects over the calculation domain. Considering the proposed mixer concurrently actuated by two finger-pressed pumps without electrical power, both experimental and simulation results show an intense swirling eddy formed in the core region of mixing chamber, achieving a mixing index up to 93% in a one-shot mixing event.

研究目的：本論文之研究主要旨在採用兩種非甾體抗炎藥--布洛芬（IBP）及氟比洛芬（FBP）來考察一項新型的納米粒子製備技術--瞬時納米沉澱技術（FNP）。IBP和FBP具有不同理化性質，但其親油性屬大部分藥物所具的典型親油性 （log P = 2-5）。研究證實IBP和FBP有治療阿爾茨海默氏病的潛在藥效，但在血液中廣泛與血漿蛋白結合，導致其腦血管通透性很低。因此，本研究的另一目的為考察FNP製備的納米處方是否能改善此類藥物的大腦遞送。
方法：應用FNP，用多入口渦旋混合器（MIVM）將藥物載入聚乙二醇-聚乳酸（PEG-PLA）的納米粒中。通過改變關鍵工藝流程變量考察了變量對納米粒物理性質及穩定性的影響。使用動態光散射儀測定了納米粒粒徑和粒徑分佈，使用zeta 電位分析測定了粒子表面電荷，使用原子力顯微鏡（AFM）確定了納米粒形態，使用x射線光電子能譜（XPS）分析了粒子表面化學成分，使用高效液相色譜測定了的處方載藥量和包封率。使用MDCK和Caco-2細胞株評估了優化後納米處方的細胞通透性，使用健康小鼠進行了優化后纳米處方的体内腦攝取實驗。
結果：IBP和FBP納米粒的粒徑均在30-100 nm的範圍內，粒徑分佈均低於或接近0.2。AFM結果顯示，納米粒具有近球狀形態。由多次線性回歸分析各工藝流程變量對IBP納米粒粒徑的影響所得相對重要性的結果為：PLA對PEG之分子量比 > 過飽和比 > 藥物對聚合物比 > 雷諾數。用相同統計方法分析FBP樣品所得結果顯示，PLA對PEG之分子量比亦為影響粒子粒徑的最重要變量。最穩定的IBP納米處方可以在懸浮液狀態下穩定超過1個月，而FBP納米處方為2天。IBP和FBP納米粒的載藥量和包封率均分別超過25%和70%。XPS，AFM和zeta電位測定結果共同表明納米粒中的PEG均偏重位於粒子表面，而相比之下，IBP納米粒中的PEG較FBP納米粒更加偏向於分佈於粒子表面。優化後的IBP納米粒由聚山梨醇酯80包裹後，與IBP溶液相比，顯著增加了IBP的健康小鼠腦攝取量。
結論：應用FNP及MIVM製備的聚合物IBP和FNP納米粒，粒徑小，粒徑分佈窄，重現性高，且有較高的載藥量和包封率。納米粒的粒徑主要取決於所採用的共聚物。IBP 納米粒子明顯優越的物理穩定性可歸功於粒子表面較高的PEG濃度。用聚山梨醇酯80包裹納米粒子對於提高IBP的大腦遞送有決定性作用。
Objectives: The present thesis work was primarily aimed at assessing a relatively novel nanoparticle (NP) production technology termed flash nanoprecipitation (FNP) using two non-steroidal anti-inflammatory drugs, ibuprofen (IBP) and flurbiprofen (FBP), with different physiochemical properties and lipophilicity typical of most drugs (log P = 2-5). Both model drugs were proven to be of potential benefits to the treatment of Alzheimer’s disease, but exhibited poor brain delivery in vivo which could be ascribed to their extensive binding with plasma proteins in the blood. Therefore another aim of the present thesis was to determine whether FNP-produced NP formulations could enhance the delivery of these drugs into the brain.
Methods: Drugs were loaded into NPs of polyethylene glycol (PEG)-polylactic acid (PLA) copolymers of different molecular weights (MWs) by FNP using a four-stream multi-inlet vortex mixer (MIVM). The influence of several key processing variables on the physical properties and stability of the NPs was investigated. The NP preparations were characterized for particle size and size distribution by dynamic light scattering (DLS) sizing analysis; surface charges by zeta potential measurement; particle morphology by atomic force microscopy (AFM); surface composition by x-ray photoelectron spectroscopy (XPS); and drug loading (DL) and encapsulation efficiency (EE) by high performance liquid chromatography. Optimal IBP NP samples were assessed in vitro for cellular permeability using Caco-2 and MDCK cell lines and in vitro for brain uptake in normal mice.
Results: Both IBP and FBP NPs exhibited mean particle size in the range of 30-100nm and polydispersity below or around 0.2. The particles were nearly spherical in shape, as examined by AFM. Multiple linear regression analysis revealed that the relative impact of the processing variables on the particle size of IBP NPs followed the order: PLA-to-PEG MW ratio > supersaturation ratio > drug-to-copolymer ratio > Reynolds number. Similar statistical analysis for FBP NPs also indicated PLA-to-PEG MW ratio being the most significant determinant of particle size. The most stable IBP and FBP NPs in suspension form could last for over 1 month and 2 days respectively. NPs with DLs > 25% and EEs > 70% could be obtained by FNP. XPS in conjunction with AFM and zeta potential analysis revealed that PEG was located more on the surfaces of both IBP and FBP NPs than in the core, but the surface PEG density was higher for the IBP NPs. Coating of optimal IBP NPs with polysorbate 80 significantly improved the brain uptake of IBP in normal mice, compared to IBP solution.
Conclusion: Polymer-stabilized IBP and FBP NPs with particle size below 100 nm and narrow size distribution can be consistently generated by FNP using the MIVM. The copolymer used is the most important determinant of particle size. The superior physical stability of the IBP NPs can be ascribed to their relatively high surface PEG density. High DLs and EEs are achievable with the FNP process. Nanoparticle coating with polysorbate 80 is critical to enhancing the delivery of IBP to the brain in normal mice.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Zhang, Xinran.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2013.
Includes bibliographical references (leaves 205-245).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts also in Chinese.
Table of Contents --- p.I
Acknowledgements --- p.VI
Abstract --- p.VIII
摘要 --- p.X
List of Figures --- p.XII
List of Tables --- p.XVII
List of Abbreviations --- p.XIX
Chapter Chapter One --- Introduction
Chapter 1.1 --- Rationale of the study --- p.1
Chapter 1.2 --- General review of nanoparticulate drug carrier systems --- p.4
Chapter 1.2.1 --- Background of nanoscience --- p.4
Chapter 1.2.2 --- Applications of nanoparticulate drug delivery systems --- p.4
Chapter 1.2.2.1 --- Improved delivery of poorly water soluble drugs --- p.5
Chapter 1.2.2.2 --- Targeted drug delivery --- p.6
Chapter 1.2.2.3 --- Drug delivery across the blood brain barrier --- p.8
Chapter 1.2.2.4 --- Other drug delivery applications --- p.10
Chapter 1.2.3 --- Types of nanoparticulate drug delivery systems --- p.10
Chapter 1.2.3.1 --- Nanocrystals --- p.10
Chapter 1.2.3.2 --- Solid lipid nanoparticles --- p.11
Chapter 1.2.3.2.1 --- Preparation methods --- p.12
Chapter 1.2.3.2.2 --- Drug delivery --- p.12
Chapter 1.2.3.3 --- Polymeric nanoparticles --- p.14
Chapter 1.2.3.3.1 --- Preparation methods --- p.15
Chapter 1.2.3.3.2 --- Drug delivery --- p.17
Chapter 1.2.4 --- Characterization of nanoparticulate drug delivery systems --- p.20
Chapter 1.2.4.1 --- Particle size and size distribution --- p.21
Chapter 1.2.4.2 --- Morphology --- p.21
Chapter 1.2.4.3 --- Zeta potential --- p.23
Chapter 1.2.4.4 --- Surface chemical composition --- p.23
Chapter 1.2.4.5 --- Crystallinity --- p.24
Chapter 1.3 --- Flash Nanoprecipitation technique --- p.25
Chapter 1.3.1 --- Mechanism and evolution --- p.25
Chapter 1.3.2 --- Applications --- p.30
Chapter 1.4 --- Ibuprofen and flurbiprofen --- p.32
Chapter 1.4.1 --- General characteristics --- p.32
Chapter 1.4.2 --- Physicochemical properties --- p.33
Chapter 1.4.3 --- New therapeutic indications --- p.34
Chapter 1.5 --- Scope of the thesis --- p.36
Chapter Chapter Two --- Influence of Processing Variables on the Physical Properties and Stability of Ibuprofen and Flurbiprofen Nanosuspensions
Chapter 2.1 --- Introduction --- p.38
Chapter 2.2 --- Materials and Methods --- p.39
Chapter 2.2.1 --- Materials --- p.39
Chapter 2.2.2 --- Solubility of ibuprofen and flurbiprofen in water and acetone mixtures --- p.39
Chapter 2.2.3 --- Nanoparticle formulation preparation --- p.40
Chapter 2.2.3.1 --- Determination of the minimum Reynolds number (Re) for homogenous mixing --- p.40
Chapter 2.2.3.2 --- Effects of processing parameters on particle size and size distribution of ADCP-protected IBP and FBP nanoparticles. --- p.41
Chapter 2.2.4 --- Particle size and size distribution measurement --- p.42
Chapter 2.2.5 --- Statistics --- p.42
Chapter 2.2.6 --- Assessment of nanosuspension stability --- p.42
Chapter 2.3 --- Results and discussion --- p.43
Chapter 2.3.1 --- Solubilities of ibuprofen and flurbiprofen in water and acetone mixtures --- p.43
Chapter 2.3.2 --- Determination of the minimum Re for homogenous mixing --- p.44
Chapter 2.3.3 --- Effects of processing parameters on particle size and size distribution of the ADCP-protected IBP and FBP nanoparticles. --- p.47
Chapter 2.3.3.1 --- Effect of solvent type --- p.47
Chapter 2.3.3.2 --- Effect of PLA-to-PEG MW ratio --- p.64
Chapter 2.3.3.3 --- Effect of supersaturation --- p.64
Chapter 2.3.3.4 --- Effect of Re --- p.70
Chapter 2.3.3.5 --- Effect of drug-to-ADCP ratio --- p.71
Chapter 2.3.4 --- Effects of processing parameters on the stability of ADCP-stabilized IBP and FBP nanoparticles --- p.72
Chapter 2.3.4.1 --- Three-day stability --- p.72
Chapter 2.3.4.2 --- Long-term stability --- p.83
Chapter 2.4 --- Summary --- p.85
Chapter Chapter Three --- Drying of Ibuprofen Nanoparticle Suspensions
Chapter 3.1 --- Introduction --- p.86
Chapter 3.2 --- Materials and Methods --- p.88
Chapter 3.2.1 --- Materials --- p.88
Chapter 3.2.2 --- Preparation of IBP nanoparticle formulations with hydrophilic stabilizers or at refrigerated temperature --- p.89
Chapter 3.2.3 --- Dialysis of nanoparticle formulations --- p.89
Chapter 3.2.4 --- Freeze-thawing of selected nanoparticle preparations --- p.89
Chapter 3.2.5 --- Freeze-drying of nanoparticle formulations --- p.90
Chapter 3.2.6 --- Reconstitution --- p.90
Chapter 3.2.7 --- Hydrogen bonding coacervate precipitation --- p.91
Chapter 3.3 --- Results and discussion --- p.91
Chapter 3.3.1 --- Preparation and dialysis of IBP nanoparticle formulations with hydrophilic stabilizers --- p.92
Chapter 3.3.2 --- Freeze-drying using cryoprotectants and lyoprotectants --- p.94
Chapter 3.3.3 --- Freeze-drying with different concentrations of glucose, sucrose and PVA --- p.101
Chapter 3.3.4 --- Freeze-drying of nanoparticles prepared under other processing conditions --- p.105
Chapter 3.3.5 --- Hydrogen bonding coacervate precipitation --- p.108
Chapter 3.4 --- Summary --- p.110
Chapter Chapter Four --- Physicochemical Characterization of Ibuprofen and Flurbiprofen Nanoparticles
Chapter 4.1 --- Introduction --- p.111
Chapter 4.2 --- Materials and Methods --- p.112
Chapter 4.2.1 --- Materials --- p.112
Chapter 4.2.2 --- Encapsulation efficiency (EE) and drug loading (DL) of IBP nanoparticles --- p.112
Chapter 4.2.3 --- HPLC analysis of IBP and FBP --- p.113
Chapter 4.2.4 --- Nanoparticle morphology --- p.114
Chapter 4.2.4.1 --- SEM --- p.114
Chapter 4.2.4.2 --- AFM --- p.114
Chapter 4.2.5 --- Zeta potential measurement --- p.115
Chapter 4.2.6 --- Surface composition analysis --- p.115
Chapter 4.3 --- Results and discussion --- p.116
Chapter 4.3.1 --- Encapsulation efficiency (EE) and drug loading (DL) of IBP nanoparticles --- p.116
Chapter 4.3.2 --- Nanoparticle morphology --- p.121
Chapter 4.3.3 --- Surface charges of the nanoparticles --- p.126
Chapter 4.3.4 --- Surface composition of nanoparticles --- p.128
Chapter 4.4 --- Summary --- p.145
Chapter Chapter Five --- Cellular Permeability and In Vivo Brain Uptake of Ibuprofen Nanoparticles
Chapter 5.1 --- Introduction --- p.146
Chapter 5.2 --- Materials and methods --- p.148
Chapter 5.2.1 --- Materials --- p.148
Chapter 5.2.2 --- Methods --- p.148
Chapter 5.2.2.1 --- Cellular permeability study --- p.148
Chapter 5.2.2.1.1 --- Cell culture --- p.148
Chapter 5.2.2.1.2 --- Cell viability study --- p.149
Chapter 5.2.2.1.3 --- MDCK and Caco-2 cell monolayer permeability assay --- p.150
Chapter 5.2.2.2 --- In vivo brain uptake study --- p.151
Chapter 5.2.2.2.1 --- HPLC-UV analysis --- p.151
Chapter 5.2.2.2.2 --- Preparation of calibration samples --- p.151
Chapter 5.2.2.2.3 --- Sample preparation --- p.152
Chapter 5.2.2.2.4 --- Validation of assay methods --- p.153
Chapter 5.2.2.2.5 --- Animal experiments --- p.154
Chapter 5.2.2.2.6 --- Data Analysis --- p.155
Chapter 5.3 --- Results and discussion --- p.155
Chapter 5.3.1 --- Cellular permeability study --- p.155
Chapter 5.3.1.1 --- Cell viability study --- p.155
Chapter 5.3.1.2 --- MDCK and Caco-2 cell monolayer permeability assay --- p.157
Chapter 5.3.2 --- In vivo brain uptake study --- p.158
Chapter 5.3.2.1 --- Method validation --- p.158
Chapter 5.3.2.2 --- Brain uptake of IBP nanoparticles --- p.159
Chapter 5.4 --- Summary --- p.166
Chapter Chapter Six --- Conclusions and Future Studies
Chapter 6.1. --- Conclusions --- p.167
Chapter 6.2. --- Future studies --- p.172
Appendices --- p.174
References --- p.205

This thesis conducts numerical and experimental studies of the nonlinear electrokinetic motion of heterogeneous particles in microfluidic systems and their corresponding applications in laboratory-on-a-chip (LOC) systems. Induced-charge electrokinetic (ICEK) phenomena flow is generated by applying an external electric field to a conducting particle immersed in an aqueous solution. As a result of this field, micro-vortices form around the conducting particle. Using this phenomenon, many shortcomings of classical electrokinetics (e.g. poor mixing, leakage, back flow problem) can be improved. This thesis proposes and investigates a complete 3-D numerical multi-physics method to calculate the induced zeta potential on the conducting surface of a heterogeneous object. To model the ICEK motion of a heterogeneous particle in a DC electric field, the moving grid technique is used to conduct the particle-fluid simulation. It was numerically shown that the vortices form near the conducting surface of a particle. Both transitional and rotational motions of heterogeneous particles are investigated. A set of novel experiments are designed and conducted to investigate several aspecs of ICEK. It is demonstrated for the first time that four vortices form around a conducting sphere in contact with an aqueous solution while the DC electric field is applied. The motions of heterogeneous particles are experimentally studied. The speed of a heterogeneous particle is compared with the same size non-conducting particle under the same experimental conditions and it is shown that the heterogeneous particle moves significantly faster than the non-conducting particle. It is also shown that the micro-vortices on the conducting section of the heterogeneous particle act like an engine and push the particle to move faster. These experiments verify the results of our simulation studies. We introduce three applications for induced-charge electrokinetic phenomena in ths thesis: ICEK micro-valve, ICEK micro-mixer, and ICEK micro-motor, which can be used in microfluidics and lab-on-a-chip devises. This ICEK micro-valve significantly improves many shortcomings of other micro-valves reported in the literature (such as leakage, considerable dead volume and complicated fabrication processes). Our ICEK micro-mixers take the advantages of induced micro-vortices and boost the mixing process in a micro-channel. As a result well mixed homogeneous (100%) mixture could be obtained at the downstream of the mixer. Our proposed no-contact ICEK micro-motor rotates as long as the DC electric field is being applied. This thesis develops a new understanding of several ICEK phenomena and applications related to heterogeneous particles. The 3D numerical model developed in this thesis along with the experimental studies are capable of describing the ICEK motion of a heterogeneous particle and is a considerable step to calculate the ICEK phenomena for real-world applications. This thesis, for the first time, experimentally visualized and verified the induced micro-vortices around conducting particles under applied DC electric field. The proposed ICEK micro-mixers, valve and motor can be used in various LOC devices and applications.

This article examines the vortex matter of mesoscopic superconductors with numerous vortex states that do not exist in bulk superconductors. Using scanning tunneling microscopy/spectroscopy, it investigates the organization of vortex cores at different levels of confinement. The article begins with a discussion of the basic properties of quantum vortices in superconductors and experimental requirements for studying vortex confinement phenomena. It then considers the effect of sample size and shape on vortex distribution and pinning, along with the resulting ultra-dense configurations that cannot be achieved in bulk superconductors. It also describes the peculiar features of vortices in atomically thin superconductors having mixed Abrikosov–Josephson vortices.

AbstractTheintegrationof a gas turbine engine into a functioning jet propulsion engine for an airplane requires more components: inlets and nozzles. For the inlet, the special care exercised to avoid ingestion of boundary layers air is described. The design features of nozzles are described and extended to include discussion of more extreme configurations such as those found on rocket engines.

Mixed flow pumps have got a wide range of application such as that in irrigation, flood control, dewatering and power station cooling systems. A number of design templates have been in use to design the mixed flow pump impeller blades including free vortex theory and mean stream line theory. Here blade of the impeller of the mixed flow pump has been designed using Mean stream line theory and the free vortex theory and stresses arising due to static loading conditions has been obtained for both the cases. Comparison analysis for the equivalent stresses developed due to structural loading using various materials for the blade was undertaken. It was found that the stress for the blade designed using mean stream line theory is always on the higher side in comparison to that designed using free vortex theory. Further, out of the four materials of construction, titanium and copper were found to be suitable for blade designed using free vortex theory and the mean stream line theory respectively.

An experimental study was conducted to investigate the mixing processes downstream of a forced mixer. A forced mixer generates large scale, axial (stirring) vorticity which causes the primary and secondary flow to mix rapidly with low loss. These devices have been successfully used in the past where enhanced mixing of two streams was a requirement. Unfortunately, details of the mixing process associated with these lobed forced mixers are not well understood. Performance sensitivity to design variables has not been documented. An experiment was set up to investigate the mixing processes downstream of a mixer. Air flow was independently supplied to each side of the forced mixer by separate centrifugal blowers. Pressures were measured at the entrance to the lobes with a pitot-static probe to document the characteristics of the approaching boundary layer. Interior mean and fluctuating velocities were nonintrusively measured using a two-component Laser Doppler Velocimetry (LDV) system for velocity ratios of 1:1 and 2:1. The wake structure is shown to display a three step process where initially secondary flow was generated by the mixer lobes, the secondary flow created counter-rotating vortices with a diameter on the order of the convolute width, and then the vortices broke down resulting in a significant increase in turbulent mixing. The results show that the mean secondary motion induced by the lobes effectively circulated the flow passing through the lobes. This motion, however, did not homogeneously mix the two streams. Turbulent mixing in the third step of the mixing process appears to be an important element in the enhanced mixing that has been observed with forced mixers. The length required for the flow to reach this third step is a function of the velocity ratio across the mixer. The results of this investigation indicate that both the mean secondary motion and the turbulent mixing occurring after vortex breakdown need to be considered for prediction of forced mixer performance.

This work concerns the characterization of turbulent flow underlying the mixing phenomenon in a static mixer-reactor HEV (high-efficiency vortex). An experimental test section made of a cylindrical tube equipped with seven rows of vortex generators was designed and constructed for this purpose. Each row has four vortex generators fixed symmetrically on the tube wall. This new type of mixer generates coherent structures in the form of longitudinal counter-rotative vortices. The resulting flow enhances radial mass transfer and thus facilitates the dispersion and mixing of the particles. The energy cost of this mixer is 1000 times less than that of other mixers for a given interface area [1, 2]. The aim of this work is to study numerically and experimentally the turbulence structure of the flow generated by the mixer, in particular the more energetic structures present in the base flow. Numerical simulations of the velocity distribution and turbulence levels inside the static mixer were conducted for various turbulence models by using the commercial mesh-generator code Gambit coupled with the CFD package Fluent. Attention was focused on the evolution and distribution of the rate of turbulent kinetic energy dissipation as the underlying mechanism for turbulent mixing. Experiments were carried out on the test section in a flow loop by using LDA. Mean and turbulent quantities were measured and numerical results were compared with experimental results. This study provides a basis for understanding the physical mechanisms in the mixing and homogenising of the flow and therefore the efficiency of the mixer.

Passive vortex generators are widely used for heat and mass transfer enhancement in static mixers and heat exchangers. Trapezoidal vortex generators are used in the high efficiency vortex static mixer (HEV) because they generate a complex flow structure enhancing the transport phenomena. Moreover, vortex generators are used on airfoils and cars to delay or suppress flow separation. The flow past triangular and rectangular winglets was studied in the open literature showing good performance in enhancing the lift and drag coefficients. In the present study, a non-conventional vortex generator is proposed consisting on an inclined trapezoidal tab similar to that used in the HEV static mixer. In addition, the tab is perforated at its center (circular perforation). Inline array of several vortex generators are fixed on an airfoil and the drag and lift coefficients are analyzed for different geometries using computational fluid dynamics. Different cases are analyzed where the inclination angles of the vortex generators are changed and their effect is investigated. Furthermore, the effect of changing the size of the vortex generator is also assessed. The results are then compared to conventional vortex generators, mainly triangular winglets. The present results are validated against experimental and numerical data from the literature. The results show that the drag coefficient can be reduced with such vortex generators. They also show good agreement with experimental results for the lift coefficient.

This paper presents a detailed experimental and computational investigation of the effects of scalloping on the mixing mechanisms of a scaled 12-lobe turbofan mixer. Scalloping was achieved by eliminating approximately 70% of the lobe sidewall area. Measurements were made downstream of the mixer in a co-annular wind tunnel and the simulations were carried out using an unstructured RANS solver, Numeca FINE/Hexa, with k-ω SST model. In the core flow, the swirl angle was varied from 0° to 30°. At high swirl angles, a three-dimensional separation bubble was formed on the lobe’s suction surface penetration region and resulted in the generation of a vortex at the lobe valley. The valley vortex quickly dissipated downstream. Most of the swirl was removed by the lobes, but scalloping allowed residual swirl to persist downstream of the mixer. The interaction of the swirling flow and the vortices resulted in improved mixing rates for the scalloped mixer. Inlet swirl up to 10° provided improved mixing rates, reduced pressure loss and thrust loss for both mixers. High inlet swirl resulted in improved mixing but produced higher pressure and thrust losses as compared to the zero swirl case. At high swirl, the scalloped mixer resulted in better mixing and lower pressure losses than the unscalloped mixer, but at the expense of reduced thrust.

Flow characterization of an electrostatically activated resonant-plate micropump-mixer was investigated. Detailed visualization of the mixing process at the tip of the resonant plate, which is almost impossible due to the high actuation frequency (10–30 kHz) and small scale of the resonant plate (250 micron) under normal conditions, was realized with a macro scale flow visualization experiment within the range of common visualization equipment such as a SLR camera. Flow phenomena such as distinct circulative regions, observed at the micro scale by Linderman et. al [1,2], were observed in this study. In addition, the transition between two different flow regimes was observed, corresponding to vortex shearing and vortex shedding respectively. This transition took place in a gradual manner over a range of Reynolds numbers between 20 and 98. Below this regime the resonant plate will only generate limited deformation of the interface between the two fluids. However, for larger Reynolds numbers, equivalent to higher plate frequencies, organized vortex roll-up is observed. Vortex roll-up indicates significant fluid entrainment, and consequently mixing. The visualization of the flow, generated by the resonating fan shed new light on the detailed flow phenomena involved, and may help guide future design and optimization of micro scale fans/mixers based on this principle.

Abstract The availability of aerodynamic performance and vorticity production data from mixers under swirl was a challenge for future full-scale design and CFD validation. This paper presents an experimental comparison of drag and mixing performance of a circular trialing edge, lobed nozzle and scalloped nozzle under high swirl conditions as produced by a ducted fan in a subsonic wind tunnel. The design methodology is shared in detail allowing for geometry reproduction. Swirl angles produced by the fan naturally varied between 12° up to 45° according to a free-vortex profile. Performance is compared in terms of net thrust, uniformity factor and vorticity production as measured by 6-component loadcells and a seven-hole pressure probe traverse. The goal of this work was threefold: to study the axial and normal vorticity production from mixers produced by the design methodology, a preliminary investigation into lobed mixers potential in engine plume cooling and to provide a data set for RANS-CFD validation. A better understanding of lobed mixer mixing mechanisms relative to performance is offered. It is shown that the change in minimum throttle to achieve forward thrust varied between devices as did the twist load due to angular forces. A 4% reduction in required fan power to achieve forward thrust was achieved with the lobed mixer. Furthermore, maximum net thrust increased up to 20% with the mixing nozzles compared to the standard round nozzle suggesting flow straightening can lead to thrust gain in high swirling jet flows to a level that counters increases in drag. Axial and normal vorticity were clearly identified. Co-rotating vortex pairs were produced by the mixers of physical size proportional to the lobe height and wavelength. Axial vorticity levels integrated up to 110% of the round nozzle and occupied 5 times the area. Similarly, integrated normal vorticity increased up to 80% over an area 120% larger. Uniformity factor was best for the scalloped mixer due to enhanced mass flow entrainment through the notch and not the vortex production itself.