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Settling of fine particles
Title
Settling of fine particles.
Creator
Kim, Hung Soo., Florida Atlantic University, Scarlatos, Panagiotis (Pete) D., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
This study pertaining to the settling of fine particles is developed using various models and formulas. The model considers two layers, i.e, the suspension zone dominated by perikinetic flocculation and the settling zone governed by gravitational force. In the suspension zone, floc formation of fine particles is simulated by the maximum chain model in which floc parameters and fractal dimension are compared with existing data. In addition, fractal dimension is compared with that of the...
Show moreThis study pertaining to the settling of fine particles is developed using various models and formulas. The model considers two layers, i.e, the suspension zone dominated by perikinetic flocculation and the settling zone governed by gravitational force. In the suspension zone, floc formation of fine particles is simulated by the maximum chain model in which floc parameters and fractal dimension are compared with existing data. In addition, fractal dimension is compared with that of the hierarchical model. The main assumption of the model is that any floc having sixteen particles outweighs Brownian force, and thus the floc starts falling down into the settling zone. The flocs moving from the suspension zone are considered as nonspherical particles in the settling zone. The study uses a dimensionless settling velocity, omega*, for estimation of the sedimentation of flocs. Settling causes aggregation of the depositing flocs. The form of these aggregates is analyzed by the fractal relationship P ~ L delta.
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Date Issued
1992
PURL
http://purl.flvc.org/fcla/dt/14872
Subject Headings
Fluid dynamics, Flow visualization
Format
Document (PDF)
TWO DIMENSIONAL FLOW WITHIN A TRIANGULAR OSCILLATING CRACK (TURBULENCE, VORTEX STREET, TRANSITION FLOW, MIXING)
Title
TWO DIMENSIONAL FLOW WITHIN A TRIANGULAR OSCILLATING CRACK (TURBULENCE, VORTEX STREET, TRANSITION FLOW, MIXING).
Creator
KIM, SOO YONG., Florida Atlantic University, Tennant, Jeffrey S., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
The transition of two dimensional flow within a crack with oscillating wall is studied experimentally to establish the role of the parameters involved. Multiple instabilities in the fluid are produced by the motion of the oscillating wall. For a better understanding of the flow structure and displaying in the whole flow field at a time, flow visualization was used. Frequency, amplitude, and crack width were systematically varied. The present study shows that, in general, the frequency and...
Show moreThe transition of two dimensional flow within a crack with oscillating wall is studied experimentally to establish the role of the parameters involved. Multiple instabilities in the fluid are produced by the motion of the oscillating wall. For a better understanding of the flow structure and displaying in the whole flow field at a time, flow visualization was used. Frequency, amplitude, and crack width were systematically varied. The present study shows that, in general, the frequency and crack width play a role in the transition process at low frequencies of oscillations. However, amplitude becomes progressively important at its higher range. Results also show that the flow changes its character approximately after a Reynolds number 11420. After that the transition process continues until the Reynolds number 34322 which is the upper limit of variation of frequency (Reynolds number) in the present study.
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Date Issued
1986
PURL
http://purl.flvc.org/fcla/dt/14312
Subject Headings
Fluid dynamics, Flow visualization
Format
Document (PDF)
Design of micromixer and microfludic control system
Title
Design of micromixer and microfludic control system.
Creator
Li, Lin, Tsai, Chi-Tay, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
Micromixer is one of the most significant components of microfluidic systems, which manifest essential applications in the field of chemistry and biochemistry. Achieving complete mixing performance at the shortest micro channel length is essential for a successful micromixer design. We have developed five novel micromixers which have advantages of high efficiency, simple fabrication, easy integration and ease for mass production. The design principle is based on the concept of splitting...
Show moreMicromixer is one of the most significant components of microfluidic systems, which manifest essential applications in the field of chemistry and biochemistry. Achieving complete mixing performance at the shortest micro channel length is essential for a successful micromixer design. We have developed five novel micromixers which have advantages of high efficiency, simple fabrication, easy integration and ease for mass production. The design principle is based on the concept of splitting-recombination and chaotic advection. Numerical models of these micromixers are developed to characterize the mixing performance. Experiments are also carried out to fabricate the micromixers and evaluate the mixing performance. Numerical simulation for different parameters such as fluids properties, inlet velocities and microchannel cross sectional sizes are also conducted to investigate their effects on the mixing performance. The results show that critical inlet velocities can be predicted for normal fluid flow in the micromixers. When the inlet velocity is smaller than the critical value, the fluids mixing is dominated by mechanism of splitting-recombination, otherwise, it is dominated by chaotic advection. If the micromixer can tolerate higher inlet velocity, the complete mixing length can be further reduced. Our simulation results will provide valuable information for engineers to design a micromixer by choosing appropriate geometry to boost mixing performance and broaden implicational range to fit their specific needs. Accurate and complicated fluidic control, such as flow mixing or reaction, solution preparation, large scale combination of different reagents is also important for bio-application of microfluidics. A proposal microfluidic system is capable of creating 1024 kinds of combination mixtures. The system is composed of a high density integrated microfluidic chip and control system. The high density microfluidic chip, which is simply fabricated through soft lithography technique, contains a pair of 32 flow channels that can be specifically addressed by each 10 actuation channels based on principle of multiplexor in electronic circuits. The corresponding hardware and software compose the control system, which can be easy fabricated and modified, especially for prototype machine developing. Moreover, the control system has general application. Experiments are conducted to verify the feasibility of this microfluidic system for multi-optional solution combination.
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Date Issued
2013
PURL
http://purl.flvc.org/fau/fd/FA0004033
Subject Headings
Flow visualization, Fluidic devices -- Design, Microelectromagnetical systems, Microfluidics -- Design
Format
Document (PDF)
Tearing of an aligned vortex by a current difference in two-layer quasi-geostrophic flow
Title
Tearing of an aligned vortex by a current difference in two-layer quasi-geostrophic flow.
Creator
Parthasarathy, Balaji., Florida Atlantic University, Marshall, Jeffrey S., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
A study of two-layer quasi-geostrophic vortex flow is performed to determine the effect of a current difference between the layers on a vortex initially extending through both the layers. In particular, the conditions under which the current difference can 'tear' the vortex are examined. In the first set of flows studied, the current difference is generated by a (stronger) third vortex in the upper layer located at a large distance from the (weaker) vortex under study. A set of flows are also...
Show moreA study of two-layer quasi-geostrophic vortex flow is performed to determine the effect of a current difference between the layers on a vortex initially extending through both the layers. In particular, the conditions under which the current difference can 'tear' the vortex are examined. In the first set of flows studied, the current difference is generated by a (stronger) third vortex in the upper layer located at a large distance from the (weaker) vortex under study. A set of flows are also considered in which an ambient geostrophic current difference is produced by a non-uniform background potential vorticity field. The results of the study will be useful in determining the conditions under which large geophysical vortex structures, such as cyclones and ocean rings, can extend to large depths even though the mean currents in the ambient flow change significantly along the vortex length.
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Date Issued
1993
PURL
http://purl.flvc.org/fcla/dt/14909
Subject Headings
Vortex-motion, Fluid dynamics, Boundary layer control, Flow visualization
Format
Document (PDF)
Experimental study of the wake-modes for propulsion of two-dimensional heaving airfoils
Title
Experimental study of the wake-modes for propulsion of two-dimensional heaving airfoils.
Creator
Buzard, Alan Joe., Florida Atlantic University, von Ellenrieder, Karl
Abstract/Description
Particle image velocimetry and flow visualization are used to characterize the wake of a heaving airfoil in a set of two experiments. In the first experiment a tandem airfoil configuration is used, with a stationary airfoil downstream of a heaving airfoil (modified Schmidt wave-propeller). Several vortex structures are identified for a forced Strouhal number (St)---based on airfoil chord-length, forcing frequency, and free-steam velocity---for 0.1
Show moreParticle image velocimetry and flow visualization are used to characterize the wake of a heaving airfoil in a set of two experiments. In the first experiment a tandem airfoil configuration is used, with a stationary airfoil downstream of a heaving airfoil (modified Schmidt wave-propeller). Several vortex structures are identified for a forced Strouhal number (St)---based on airfoil chord-length, forcing frequency, and free-steam velocity---for 0.1 < St < 0.7. An asymmetric average velocity profile is measured in the upper St range. In the second experiment, the wake behind a single heaving airfoil is further inspected, with the purpose of highlighting the asymmetric wake, for 0.1 < St < 1.0. A maximum wake excursion of 18 degrees is measured at St = 0.6, and a minimum excursion of 5.7 degrees occurs at St = 0.9. Using averaged velocity profiles, a virtual origin of the wake excursion is also calculated.
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Date Issued
2005
PURL
http://purl.flvc.org/fcla/dt/13216
Subject Headings
Particle accelerators--Research, Aerofoils, Aerodynamics, Wakes (Aerodynamics), Flow visualization
Format
Document (PDF)
model of the horseshoe vortex in juncture flows
Title
A model of the horseshoe vortex in juncture flows.
Creator
Monnier, Elie Bertrand., Florida Atlantic University, Dhanak, Manhar R., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
When a boundary-layer flow, either laminar or turbulent, encounters a hemispherical body extending from a surface, a horseshoe-shaped vortex forms at the juncture. In this thesis, we study the evolution of this vortex using a numerical inviscid model and laboratory experiments. The numerical model is based on determining the evolution of the filament using the cut-off method. The assumption is that although the generation of the vortex depends on viscous effects, the dynamic evolution is well...
Show moreWhen a boundary-layer flow, either laminar or turbulent, encounters a hemispherical body extending from a surface, a horseshoe-shaped vortex forms at the juncture. In this thesis, we study the evolution of this vortex using a numerical inviscid model and laboratory experiments. The numerical model is based on determining the evolution of the filament using the cut-off method. The assumption is that although the generation of the vortex depends on viscous effects, the dynamic evolution is well described by inviscid equations of motion. It is found that the vortex filament is fairly steady on the upstream side but on the downstream side, travelling waves appear on it which cannot be suppressed through evolution. For a range of Reynolds number, steady horseshoe-shaped vortex was obtained in the experiments, revealing the shape past the hemisphere. This is compared with the numerical results.
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Date Issued
1996
PURL
http://purl.flvc.org/fcla/dt/15326
Subject Headings
Boundary layer, Cascades (Fluid dynamics), Flow visualization, Vortex generators
Format
Document (PDF)