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 Title
 A numerical study of bluff body aerodynamics by vortex method.
 Creator
 He, Fusen., Florida Atlantic University, Su, TsungChow, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Vortex methods are gridfree; therefore, their use avoids a number of shortcomings of Eulerian, gridbased numerical methods for solving high Reynolds number flow problems. These include such problems as poor resolution and numerical diffusion. In vortex methods, the continuous vorticity field is discretized into a collection of Lagrangian elements, known as vortex elements. Vortex elements are free to move in the flow field which they create. The velocity field induced by these vortex...
Show moreVortex methods are gridfree; therefore, their use avoids a number of shortcomings of Eulerian, gridbased numerical methods for solving high Reynolds number flow problems. These include such problems as poor resolution and numerical diffusion. In vortex methods, the continuous vorticity field is discretized into a collection of Lagrangian elements, known as vortex elements. Vortex elements are free to move in the flow field which they create. The velocity field induced by these vortex elements is a solution to the NavierStokes equation, and in principle the method is suitable for high Reynolds number flows. In this dissertation, viscous vortex element methods are studied. Some modifications are developed. Discrete vortex element methods have been used to solve the NavierStokes equations in high Reynolds number flows. Globally satisfactory results have been obtained. However, computed pressure fields are often inaccurate due to the significant errors in the surface vorticity distribution. In addition, different ad hoc assumptions are often used in different proposed algorithms. In the present study, improvements are made to better represent the nearwall vorticity when obtaining numerical solutions for the NavierStokes equations. In particular, we split the boundary vortex sheet into two parts at each time step. One part remains a vortex sheet lying on the boundary of the solid body, and the other enters into the flow field as a free vortex element with a uniformly distributed vorticity. A set of kinematic relationships are used to determine the two appropriate portions of the split, and the position of the vortex element to be freed at the time of release. Another improvement is to include the nonlinear acceleration terms in the governing equations near the solid boundary when evaluating the surface pressure distribution. The aerodynamic force coefficients can then be obtained by summing up the pressure forces. By comparing the computed surface vorticities, surface pressures and aerodynamics force coefficients with existing numerical/experimental data in the cases of viscous flow around a circular cylinder, an aerofoil, and a bridge deck section, it is shown that the present approach is more accurate in modelling the flow features and force coefficients without making different ad hoc assumptions for different geometries. The computation is efficient. It can be useful in the study of the unsteady fluid flow phenomenon in practical engineering problems.
Show less  Date Issued
 1998
 PURL
 http://purl.flvc.org/fcla/dt/12574
 Subject Headings
 Vortexmotion, Fluid mechanics, Viscous flow
 Format
 Document (PDF)
 Title
 Rapid distortion theory for rotor inflows.
 Creator
 Kawashima, Emilia, Glegg, Stewart A. L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

For aerospace and naval applications where low radiated noise levels are a requirement, rotor noise generated by inflow turbulence is of great interest. Inflow turbulence is stretched and distorted as it is ingested into a thrusting rotor which can have a significant impact on the noise source levels. This thesis studies the distortion of subsonic, high Reynolds number turbulent flow, with viscous effects ignored, that occur when a rotor is embedded in a turbulent boundary layer. The analysis...
Show moreFor aerospace and naval applications where low radiated noise levels are a requirement, rotor noise generated by inflow turbulence is of great interest. Inflow turbulence is stretched and distorted as it is ingested into a thrusting rotor which can have a significant impact on the noise source levels. This thesis studies the distortion of subsonic, high Reynolds number turbulent flow, with viscous effects ignored, that occur when a rotor is embedded in a turbulent boundary layer. The analysis is based on Rapid Distortion Theory (RDT), which describes the linear evolution of turbulent eddies as they are stretched by a mean flow distortion. Providing that the gust does not distort the mean flow streamlines the solution for a mean flow with shear is found to be the same as the solution for a mean potential flow with the addition of a potential flow gust. By investigating the inflow distortion of smallscale turbulence for various simple flows and rotor inflows with weak shear, it is shown that RDT can be applied to incompressible shear flows to determine the flow distortion. It is also shown that RDT can be applied to more complex flows modeled by the Reynolds Averaged Navier Stokes (RANS) equations.
Show less  Date Issued
 2013
 PURL
 http://purl.flvc.org/fau/fd/FA0004030
 Subject Headings
 Computational fluid dynamics, Fluid dynamic measurements, Fluid mechanics  Mathematical models, Turbulence  Computer simulation, Turbulence  Mathematical models
 Format
 Document (PDF)
 Title
 FarField Noise From a Rotor in a Wind Tunnel.
 Creator
 Grant, Justin Alexander, Glegg, Stewart A. L., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This project is intended to demonstrate the current state of knowledge in the prediction of the tonal and broadband noise radiation from a Sevik rotor. The rotor measurements were made at the Virginia Tech Stability Wind Tunnel. Details of the rotor noise and flow measurements were presented by Wisda et al(2014) and Murray et al(2015) respectively. This study presents predictions based on an approach detailed by Glegg et al(2015) for the broadband noise generated by a rotor in an...
Show moreThis project is intended to demonstrate the current state of knowledge in the prediction of the tonal and broadband noise radiation from a Sevik rotor. The rotor measurements were made at the Virginia Tech Stability Wind Tunnel. Details of the rotor noise and flow measurements were presented by Wisda et al(2014) and Murray et al(2015) respectively. This study presents predictions based on an approach detailed by Glegg et al(2015) for the broadband noise generated by a rotor in an inhomogeneous flow, and compares them to measured noise radiated from the rotor at prescribed observer locations. Discrepancies between the measurements and predictions led to comprehensive study of the flow in the wind tunnel and the discovery of a vortex upstream of the rotor at low advance ratios. The study presents results of RANS simulations. The static pressure and velocity profile in the domain near the rotor's tip gap region were compared to measurements obtained from a pressure port array and a PIV visualization of the rotor in the wind tunnel.
Show less  Date Issued
 2015
 PURL
 http://purl.flvc.org/fau/fd/FA00004501, http://purl.flvc.org/fau/fd/FA00004501
 Subject Headings
 Aerodynamic noise, Computational fluid dynamics, Fluid dynamic measurement, Fluid mechanics  Mathematical models, Fluid structure interactioin, Turbomachines  Fluid dynamics, Turbulence  Mathematical models, Unsteady flow (Fluid dynamics)
 Format
 Document (PDF)
 Title
 Predicting the flow & noise of a rotor in a turbulent boundary layer using an actuator disk – Rans approach.
 Creator
 Buono, Armand C., Glegg, Stewart A. L., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The numerical method presented in this study attempts to predict the mean, nonuniform flow field upstream of a propeller partially immersed in a thick turbulent boundary layer with an actuator disk using CFD based on RANS in ANSYS FLUENT. Three different configurations, involving an infinitely thin actuator disk in the freestream (Configuration 1), an actuator disk near a wall with a turbulent boundary layer (Configuration 2), and an actuator disk with a hub near a wall with a turbulent...
Show moreThe numerical method presented in this study attempts to predict the mean, nonuniform flow field upstream of a propeller partially immersed in a thick turbulent boundary layer with an actuator disk using CFD based on RANS in ANSYS FLUENT. Three different configurations, involving an infinitely thin actuator disk in the freestream (Configuration 1), an actuator disk near a wall with a turbulent boundary layer (Configuration 2), and an actuator disk with a hub near a wall with a turbulent boundary layer (Configuration 3), were analyzed for a variety of advance ratios ranging from J = 0.48 to J =1.44. CFD results are shown to be in agreement with previous works and validated with experimental data of reverse flow occurring within the boundary layer above the flat plate upstream of a rotor in the Virginia Tech’s Stability Wind Tunnel facility. Results from Configuration 3 will be used in future aeroacoustic computations.
Show less  Date Issued
 2014
 PURL
 http://purl.flvc.org/fau/fd/FA00004269, http://purl.flvc.org/fau/fd/FA00004269
 Subject Headings
 Aeroelasticity, Computational fluid dynamics, Fluid dynamic measurements, Fluid mechanics  Mathematical models, Turbomachines  Fluid dynamics, Turbulence  Mathematical models
 Format
 Document (PDF)
 Title
 Evaluation of motion compensated ADV measurements for quantifying velocity fluctuations.
 Creator
 Lovenbury, James William., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This study assesses the viability of using a towfish mounted ADV for quantifying water velocity fluctuations in the Florida Current relevant to ocean current turbine performance. For this study a motion compensated ADV is operated in a test flume. Water velocity fluctuations are generated by a 1.3 cm pipe suspended in front of the ADV at relative current speeds of 0.9 m/s and 0.15 m/s, giving Reynolds numbers on the order of 1000. ADV pitching motion of +/ 2.5 [degree] at 0.3 Hz and a heave...
Show moreThis study assesses the viability of using a towfish mounted ADV for quantifying water velocity fluctuations in the Florida Current relevant to ocean current turbine performance. For this study a motion compensated ADV is operated in a test flume. Water velocity fluctuations are generated by a 1.3 cm pipe suspended in front of the ADV at relative current speeds of 0.9 m/s and 0.15 m/s, giving Reynolds numbers on the order of 1000. ADV pitching motion of +/ 2.5 [degree] at 0.3 Hz and a heave motion of 0.3 m amplitude at 0.2 Hz are utilized to evaluate the motion compensation approach. The results show correction for motion provides up to an order of magnitude reduction in turbulent kinetic energy at frequencies of motion while the IMU is found to generate 2% error at 1/30 Hz and 9% error at 1/60 Hz in turbulence intensity.
Show less  Date Issued
 2013
 PURL
 http://purl.flvc.org/fcla/dt/3362482
 Subject Headings
 Motion control systems, Fluid dynamic measurements, Fluid mechanics, Mathematical models, Analysis of covariance
 Format
 Document (PDF)
 Title
 The acoustic far field of a turbulent boundary layer flow calculated from RANS simulations of the flow.
 Creator
 Blanc, JeanBaptiste., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Boundary layers are regions where turbulence develops easily. In the case where the flow occurs on a surface showing a certain degree of roughness, turbulence eddies will interact with the roughness elements and will produce an acoustic field. This thesis aims at predicting this type of noise with the help of the Computational Fluid Dynamics (CFD) simulation of a wall jet using the Reynolds Average NavierStokes (RANS) equations. A frequency spectrum is reconstructed using a representation of...
Show moreBoundary layers are regions where turbulence develops easily. In the case where the flow occurs on a surface showing a certain degree of roughness, turbulence eddies will interact with the roughness elements and will produce an acoustic field. This thesis aims at predicting this type of noise with the help of the Computational Fluid Dynamics (CFD) simulation of a wall jet using the Reynolds Average NavierStokes (RANS) equations. A frequency spectrum is reconstructed using a representation of the turbulence with uncorrelated sheets of vorticity. Both aerodynamic and acoustic results are compared to experimental measurements of the flow. The CFD simulation of the flow returns consistent results but would benefit from a refinement of the grid. The surface pressure spectrum presents a slope in the high frequencies close to the experimental spectrum. The far field noise spectrum has a 5dB difference to the experiments.
Show less  Date Issued
 2009
 PURL
 http://purl.flvc.org/FAU/368611
 Subject Headings
 Computational fluid dynamics, Turbulence, Mathematical models, Fluid mechanics, Mathematical models, Acoustical engineering
 Format
 Document (PDF)
 Title
 Electrochemical aspects of magnetohydrodynamic thrusters.
 Creator
 Moreno, Juan E., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The concept of using Magnetohydrodynamics to provide thrust has been around for decades. However little work has been carried out in one of the fundamental aspects that allows for these systems to operate in seawater. Therefore a series of tests were carried out to determine how the electrochemical reactions occurring at the electrodes affect the seawater system. These tests were used to determine the effects magnetic fields have on seawater conductivity, the pH changes around the electrodes,...
Show moreThe concept of using Magnetohydrodynamics to provide thrust has been around for decades. However little work has been carried out in one of the fundamental aspects that allows for these systems to operate in seawater. Therefore a series of tests were carried out to determine how the electrochemical reactions occurring at the electrodes affect the seawater system. These tests were used to determine the effects magnetic fields have on seawater conductivity, the pH changes around the electrodes, and consider the double layer capacitance model as a means to decrease the amount of gas bubbles created at the electrodes. As a result significant increases in resistivity in seawater were observed when the magnetic field was introduced, pH changes were seen on both the cathode and anode, and pulsing of the applied potential may stimulate further work to be considered.
Show less  Date Issued
 2011
 PURL
 http://purl.flvc.org/FAU/3171720
 Subject Headings
 Electric power production, Metrohydrodynamic generation, Fluid mechanics, Magnetohydrodynamics
 Format
 Document (PDF)
 Title
 Experimental Investigation of Skin Friction Drag Reduction on a Flat Plate using Microbubbles.
 Creator
 Grabe, Zachary A., Dhanak, Manhar R., Florida Atlantic University
 Abstract/Description

A microbubble generation system has been designed, constructed, and tested in a circulating water tunnel. A 1.0 m long flat plate was subjected to a flow where the Reynolds number ranged from ReL = 7.23x 10^5  1.04 x 10^6. Bubble diameters and skin friction measurements were studied at various airflow rates and water velocities. Bubbles were produced by forcing air through porous plates that were mounted flush with the bottom of the test plate. Once emitted through the plates, the bubbles...
Show moreA microbubble generation system has been designed, constructed, and tested in a circulating water tunnel. A 1.0 m long flat plate was subjected to a flow where the Reynolds number ranged from ReL = 7.23x 10^5  1.04 x 10^6. Bubble diameters and skin friction measurements were studied at various airflow rates and water velocities. Bubbles were produced by forcing air through porous plates that were mounted flush with the bottom of the test plate. Once emitted through the plates, the bubbles traveled downstream in the boundary layer. The airflow rate and water velocity were found to have the most significant impact on the size of the bubbles created. Skin friction drag measurements were recorded in detail in the velocity and airflow rate ranges. The coefficient of skin friction was determined and relationships were then established between this coefficient and the void ratio.
Show less  Date Issued
 2007
 PURL
 http://purl.flvc.org/fau/fd/FA00012523
 Subject Headings
 Frictional resistance (Hydrodynamics), Drag (Aerodynamics), Skin friction (Aerodynamics), Fluid mechanics
 Format
 Document (PDF)
 Title
 Aerodynamic analysis of a propeller in a turbulent boundary layer flow.
 Creator
 Lachowski, Felipe Ferreira., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Simulating the exact chaotic turbulent flow field about any geometry is a dilemma between accuracy and computational resources, which has been continuously studied for just over a hundred years. This thesis is a complete walkthrough of the entire process utilized to approximate the flow ingested by a Seviktype rotor based on solutions to the Reynolds Averaged NavierStokes equations (RANS). The Multiple Reference Frame fluid model is utilized by the code of ANSYSFLUENT and results are...
Show moreSimulating the exact chaotic turbulent flow field about any geometry is a dilemma between accuracy and computational resources, which has been continuously studied for just over a hundred years. This thesis is a complete walkthrough of the entire process utilized to approximate the flow ingested by a Seviktype rotor based on solutions to the Reynolds Averaged NavierStokes equations (RANS). The Multiple Reference Frame fluid model is utilized by the code of ANSYSFLUENT and results are validated by experimental wake data. Three open rotor configurations are studied including a uniform inflow and the rotor near a plate with and without a thick boundary layer. Furthermore, observations are made to determine the variation in velocity profiles of the ingested turbulent flow due to varying flow conditions.
Show less  Date Issued
 2013
 PURL
 http://purl.flvc.org/fcla/dt/3360798
 Subject Headings
 Acoustical engineering, Boundary layer control, Multiphase flow, Mathematical models, Fluid mechanics, Mathematical models, Turbulence, Mathematical models, Computatioinal fluid dynamics
 Format
 Document (PDF)
 Title
 Spectral evaluation of motion compensated adv systems for ocean turbulence measurements.
 Creator
 Egeland, Matthew Nicklas, von Ellenrieder, Karl, VanZwieten, James H., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

A motion compensated ADV system was evaluated to determine its ability to make measurements necessary for characterizing the variability of the ambient current in the Gulf Stream. The impact of IMU error relative to predicted turbulence spectra was quantified, as well as and the ability of the motion compensation approach to remove sensor motion from the ADV measurements. The presented data processing techniques are shown to allow the evaluated ADV to be effectively utilized for quantifying...
Show moreA motion compensated ADV system was evaluated to determine its ability to make measurements necessary for characterizing the variability of the ambient current in the Gulf Stream. The impact of IMU error relative to predicted turbulence spectra was quantified, as well as and the ability of the motion compensation approach to remove sensor motion from the ADV measurements. The presented data processing techniques are shown to allow the evaluated ADV to be effectively utilized for quantifying ambient current fluctuations from 0.02 to 1 Hz (50 to 1 seconds) for dissipation rates as low as 3x107. This measurement range is limited on the low frequency end by IMU error, primarily by the calculated transformation matrix, and on the high end by Doppler noise. Inshore testing has revealed a 0.37 Hz oscillation inherent in the towfish designed and manufactured as part of this project, which can nearly be removed using the IMU.
Show less  Date Issued
 2014
 PURL
 http://purl.flvc.org/fau/fd/FA00004191, http://purl.flvc.org/fau/fd/FA00004191
 Subject Headings
 Fluid dynamic measurements, Fluid mechanics  Mathematical models, Motion control systems, Ocean atmosphere interaction, Ocean circulation, Turbulence, Wave motion, Theory of
 Format
 Document (PDF)
 Title
 Barometric distillation and the problem of noncondensable gases.
 Creator
 Martinson, Eiki., College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
 Abstract/Description

Barometric distillation is an alternative method of producing fresh water by desalination. This proposed process evaporates saline water at low pressure and consequently low temperature; low pressure conditions are achieved by use of barometric columns and condensation is by direct contact with a supply of fresh water that will be augmented by the distillate. Lowtemperature sources of heat, such as the cooling water rejected by electrical power generating facilities, can supply this system...
Show moreBarometric distillation is an alternative method of producing fresh water by desalination. This proposed process evaporates saline water at low pressure and consequently low temperature; low pressure conditions are achieved by use of barometric columns and condensation is by direct contact with a supply of fresh water that will be augmented by the distillate. Lowtemperature sources of heat, such as the cooling water rejected by electrical power generating facilities, can supply this system with the latent heat of evaporation. Experiments are presented that show successful distillation with a temperature difference between evaporator and condenser smaller than 10ê C. Accumulation of dissolved gases coming out of solution, a classic problem in lowpressure distillation, is indirectly measured using a gastension sensor. The results of these experiments are used in an analysis of the specific energy required by a production process capable of producing 15 liters per hour. With a 20ê C difference, and neglecting latent heat, this analysis yields a specific energy of 1.85 kilowatthour per cubic meter, consumed by water pumping and by removal of noncondensable gases.
Show less  Date Issued
 2010
 PURL
 http://purl.flvc.org/FAU/2978949
 Subject Headings
 Chemistry, Physical and theoretical, Fluid mechanics, Saline water conversion, Renewable energy sources, Groundwater, Purification
 Format
 Document (PDF)
 Title
 Experimental analysis of the effect of waves on a floating wind turbine.
 Creator
 Isaza, Francisco, Ghenai, Chaouki, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The goal of this Thesis is to demonstrate, through experimentation, that ocean waves have a positive effect on the performance of an offshore wind turbine. A scale model wind turbine was placed into a wave tank that was completely covered and fitted with a variable speed fan to create different wind and wave conditions for testing. Through testing, different power coefficient vs. tip speed ratio graphs were created and a change in power coefficient was observed between steady operating...
Show moreThe goal of this Thesis is to demonstrate, through experimentation, that ocean waves have a positive effect on the performance of an offshore wind turbine. A scale model wind turbine was placed into a wave tank that was completely covered and fitted with a variable speed fan to create different wind and wave conditions for testing. Through testing, different power coefficient vs. tip speed ratio graphs were created and a change in power coefficient was observed between steady operating conditions and operating conditions with waves. The results show a promising increase in power production for offshore wind turbines when allowed to operate with the induced motion caused by the amplitude and frequency of water waves created.
Show less  Date Issued
 2013
 PURL
 http://purl.flvc.org/fau/fd/FA0004026
 Subject Headings
 Fluid mechanics, Offshore wind power plants, Renewable energy sources, Wind turbines  Design and construction
 Format
 Document (PDF)
 Title
 caHydrodynamic analysis of flapping foils for the propulsion of near surface under water vehicles using the panel method.
 Creator
 Bustos, Julia, Ananthakrishnan, Palaniswamy, Dhanak, Manhar R., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This thesis presents twodimensional hydrodynamic analysis of flapping foils for the propulsion of underwater vehicles using a sourcevortex panel. Using a simulation program developed in MatLab, the hydrodynamic forces (such as the lift and the drag) as well as the propulsion thrust and efficiency are computed with this method. The assumptions made in the analysis are that the flow around a hydrofoil is twodimensional, incompressible and inviscid. The analysis is first considered for the...
Show moreThis thesis presents twodimensional hydrodynamic analysis of flapping foils for the propulsion of underwater vehicles using a sourcevortex panel. Using a simulation program developed in MatLab, the hydrodynamic forces (such as the lift and the drag) as well as the propulsion thrust and efficiency are computed with this method. The assumptions made in the analysis are that the flow around a hydrofoil is twodimensional, incompressible and inviscid. The analysis is first considered for the case of a deeply submerged hydrofoil followed by the case where it is located in shallow water depth or near the free surface. In the second case, the presence of the free surface and wave effects are taken into account, specifically at high and low frequencies and small and large amplitudes of flapping. The objective is to determine the thrust and efficiency of the flapping –foils under the influence of added effects of the free surface. Results show that the freesurface can significantly affect the foil performance by increasing the efficiency particularly at high Frequencies.
Show less  Date Issued
 2015
 PURL
 http://purl.flvc.org/fau/fd/FA00004351, http://purl.flvc.org/fau/fd/FA00004351
 Subject Headings
 Aerodynamics  Mathematical models, Fluid mechanics, Naval architecture, Ships  Aerodynamics, Steering gear
 Format
 Document (PDF)
 Title
 Internal waves on a continental shelf.
 Creator
 Jagannathan, Arjun., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

In this thesis, a 2D CHebyshev spectral domain decomposition method is developed for simulating the generation and propagation of internal waves over a topography. While the problem of stratified flow over topography is by no means a new one, many aspects of internal wave generation and breaking are still poorly understood. This thesis aims to reproduce certain observed features of internal waves by using a Chebyshev collation method in both spatial directions. The numerical model solves the...
Show moreIn this thesis, a 2D CHebyshev spectral domain decomposition method is developed for simulating the generation and propagation of internal waves over a topography. While the problem of stratified flow over topography is by no means a new one, many aspects of internal wave generation and breaking are still poorly understood. This thesis aims to reproduce certain observed features of internal waves by using a Chebyshev collation method in both spatial directions. The numerical model solves the inviscid, incomprehensible, fully nonlinear, nonhydrostatic Boussinesq equations in the vorticitystreamfunction formulation. A number of important features of internal waves over topography are captured with the present model, including the onset of wavebreaking at subcritical Froude numbers, up to the point of overturning of the pycnoclines. Density contours and wave spectra are presented for different combinations of Froude numbers, stratifications and topographic slope.
Show less  Date Issued
 2012
 PURL
 http://purl.flvc.org/FAU/3358549
 Subject Headings
 Engineering geology, Mathematical models, Chebyshev polynomials, Fluid dynamics, Continuum mechanics, Spectral theory (Mathematics)
 Format
 Document (PDF)
 Title
 Hydrodynamics of mangrove roottype models.
 Creator
 Kazemi, Amirkhosro, Curet, Oscar M., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Mangrove trees play a prominent role in coastal tropic and subtropical regions, providing habitat for many organisms and protecting shorelines against storm surges, high winds, erosion, and tsunamis. The motivation of this proposal is to understand the complex interaction of mangrove roots during tidal flow conditions using simplified physical models. In this dissertation, the mangrove roots were modeled with a circular array of cylinders with different porosities and spacing ratios. In...
Show moreMangrove trees play a prominent role in coastal tropic and subtropical regions, providing habitat for many organisms and protecting shorelines against storm surges, high winds, erosion, and tsunamis. The motivation of this proposal is to understand the complex interaction of mangrove roots during tidal flow conditions using simplified physical models. In this dissertation, the mangrove roots were modeled with a circular array of cylinders with different porosities and spacing ratios. In addition, we modeled the flexibility of the roots by attaching rigid cylinders to hinge connectors. The models were tested in a water tunnel for a range of Reynolds number from 2200 to 11000. Additionally, we performed 2D flow visualization for different root models in a flowing soap film setup. We measured drag force and the instantanous streamwise velocity downstream of the models. Furthermore, we investigated the fluid dynamics downstream of the models using a 2D timeresolved particle image velocimetry (PIV), and flow visualization. The result was analyzed to present timeaveraged and timeresolved flow parameters including the velocity distribution, vorticity, streamline, Reynolds shear stress and turbulent kinetic energy. We found that the frequency of the vortex shedding increases as the diameter of the small cylinders decreases while the patch diameter is constant, therefore increasing the Strouhal number, St=fD/U By comparing the change of Strouhal numbers with a single solid cylinder, we introduced a new length scale, the “effective diameter”. In addition, the effective diameter of the patch decreases as the porosity increases. In addition, patch drag decreases linearly as the spacing ratio increases. For flexible cylinders, we found that a decrease in stiffness increases both patch drag and the wake deficit behind the patch in a similar fashion as increasing the blockage of the patch. The average drag coefficient decreased with increasing Reynolds number and with increasing porosity. We found that the Reynolds stress (−u′v′) peak is not only shifted in the vortex structure because of shear layer interference, but also the intensity was weakened by increasing the porosity, which causes a weakening of the buckling of vorticity layers leading to a decline in vortex strength as well as increase in wake elongation.
Show less  Date Issued
 2017
 PURL
 http://purl.flvc.org/fau/fd/FA00004948, http://purl.flvc.org/fau/fd/FA00004948
 Subject Headings
 Fluid mechanics., Atmospheric models., Ocean currentsMathematical models., Sediment transport., Estuarine oceanography.
 Format
 Document (PDF)
 Title
 UNDERSTANDING GRAVITY DRIVEN PARTICLE SETTLING AND DISTRIBUITION IN FRACTURES.
 Creator
 Hafez, Mazen, Kim, Myeongsub, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
 Abstract/Description

The elevated energy demand and high dependency on fossil fuels have directed researchers’ attention to promoting and advancing hydraulic fracturing (HF) operations for a sustainable energy future. Previous studies have demonstrated that the particle suspension and positioning in slick water play a vital role during the injection and shutin stages of the HF operations. A significant challenge to HF is the premature particle settling and uneven particle distribution in a formation. Even though...
Show moreThe elevated energy demand and high dependency on fossil fuels have directed researchers’ attention to promoting and advancing hydraulic fracturing (HF) operations for a sustainable energy future. Previous studies have demonstrated that the particle suspension and positioning in slick water play a vital role during the injection and shutin stages of the HF operations. A significant challenge to HF is the premature particle settling and uneven particle distribution in a formation. Even though various research was conducted on the topic of particle transport, there still exist gaps in the fundamental particleparticle interaction mechanisms. This dissertation utilizes both experimental and numerical approaches to advance the state of the art in particleparticle interactions in various test conditions. Experimentally, the study utilizes highspeed imaging coupled with particle tracking velocimetry (PTV) and particle image velocimetry (PIV) to provide a space and timeresolved investigation of both twoparticle and multiparticle interactions during gravitational settling, respectively.
Show less  Date Issued
 2022
 PURL
 http://purl.flvc.org/fau/fd/FA00014095
 Subject Headings
 Hydraulic fracturing, Particle image velocimetry, Particle tracking velocimetry, Fluid mechanics research
 Format
 Document (PDF)
 Title
 Developing interpretive turbulence models from a database with applications to wind farms and shipboard operations.
 Creator
 Schau, Kyle A., Gaonkar, Gopal H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This thesis presents a complete method of modeling the autospectra of turbulence in closed form via an expansion series using the von Kármán model as a basis function. It is capable of modeling turbulence in all three directions of fluid flow: longitudinal, lateral, and vertical, separately, thus eliminating the assumption of homogeneous, isotropic flow. A thorough investigation into the expansion series is presented, with the strengths and weaknesses highlighted. Furthermore, numerical...
Show moreThis thesis presents a complete method of modeling the autospectra of turbulence in closed form via an expansion series using the von Kármán model as a basis function. It is capable of modeling turbulence in all three directions of fluid flow: longitudinal, lateral, and vertical, separately, thus eliminating the assumption of homogeneous, isotropic flow. A thorough investigation into the expansion series is presented, with the strengths and weaknesses highlighted. Furthermore, numerical aspects and theoretical derivations are provided. This method is then tested against three highly complex flow fields: wake turbulence inside wind farms, helicopter downwash, and helicopter downwash coupled with turbulence shed from a ship superstructure. These applications demonstrate that this method is remarkably robust, that the developed autospectral models are virtually tailored to the design of white noise driven shaping filters, and that these models in closed form facilitate a greater understanding of complex flow fields in wind engineering.
Show less  Date Issued
 2013
 PURL
 http://purl.flvc.org/fau/fd/FA0004058
 Subject Headings
 Fluid mechanics, Renewable energy sources, Von Kármán, Theodore  18811963, Wind energy conservation systems, Wind power, Wind turbines  Aerodynamics
 Format
 Document (PDF)
 Title
 Some corrosion problems associated with underwater turbines.
 Creator
 Miglis, Yohann., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This thesis deals with corrosion problems of underwater turbines in marine environment. The effect of a tensile stress on the uniform corrosion rate of a metal bar is studied, and an analytical model predicting the time of service of a bar under a tensile load in a corrosive environment is proposed. Stress corrosion relationships are provided for different type of alloys, and different types of relationships. Dolinskii's and Gutman's models are studied and extended to a general order...
Show moreThis thesis deals with corrosion problems of underwater turbines in marine environment. The effect of a tensile stress on the uniform corrosion rate of a metal bar is studied, and an analytical model predicting the time of service of a bar under a tensile load in a corrosive environment is proposed. Stress corrosion relationships are provided for different type of alloys, and different types of relationships. Dolinskii's and Gutman's models are studied and extended to a general order polynomial, along with a Least Square and Spline Interpolation of the experimental data. In a second part, the effect of the passive film, delaying the initiation of the corrosion process, is studied. Finally, an algorithm predicting the time of service of a cracked bar is provided, using the stress corrosion assumption, along with a validation using experimental data.
Show less  Date Issued
 2012
 PURL
 http://purl.flvc.org/FAU/3342238
 Subject Headings
 Turbines, Stress corrosion, Testing, Computational fluid dynamics, Stress corrosion, Fracture mechanics, Measurement, Alloys, Stress corrosion, Testing, Alloys, Corrosion fatigue, Testing
 Format
 Document (PDF)
 Title
 Design and Deployment Analysis of Morphing Ocean Structure.
 Creator
 Li, Yanjun, Su, TsungChow, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

As humans explore greater depths of Earth’s oceans, there is a growing need for the installation of subsea structures. 71% of the earth’s surface is ocean but there are limitations inherent in current detection instruments for marine applications leading to the need for the development of underwater platforms that allow research of deeper subsea areas. Several underwater platforms including Autonomous Underwater Vehicles (AUVs), Remote Operated Vehicles (ROVs), and wave gliders enable more...
Show moreAs humans explore greater depths of Earth’s oceans, there is a growing need for the installation of subsea structures. 71% of the earth’s surface is ocean but there are limitations inherent in current detection instruments for marine applications leading to the need for the development of underwater platforms that allow research of deeper subsea areas. Several underwater platforms including Autonomous Underwater Vehicles (AUVs), Remote Operated Vehicles (ROVs), and wave gliders enable more efficient deployment of marine structures. Deployable structures are able to be compacted and transported via AUV to their destination then morph into their final form upon arrival. They are a lightweight, compact solution. The wrapped package includes the deployable structure, underwater pump, and other necessary instruments, and the entire package is able to meet the payload capability requirements. Upon inflation, these structures can morph into final shapes that are a hundred times larger than their original volume, which extends the detection range and also provides longterm observation capabilities. This dissertation reviews underwater platforms, underwater acoustics, imaging sensors, and inflatable structure applications then proposes potential applications for the inflatable structures. Based on the proposed applications, a conceptual design of an underwater tubular structure is developed and initial prototypes are built for the study of the mechanics of inflatable tubes. Numerical approaches for the inflation process and bending loading are developed to predict the inflatable tubular behavior during the structure’s morphing process and under different loading conditions. The material properties are defined based on tensile tests. The numerical results are compared with and verified by experimental data. The methods used in this research provide a solution for underwater inflatable structure design and analysis. Several ocean morphing structures are proposed based on the inflatable tube analysis.
Show less  Date Issued
 2016
 PURL
 http://purl.flvc.org/fau/fd/FA00004752, http://purl.flvc.org/fau/fd/FA00004752
 Subject Headings
 Airsupported structuresDesign and construction., Remote submersiblesDesign and construction., Tensile architecture., Fluid mechanics., Structural dynamics., Ocean engineering., Adaptive control systems.
 Format
 Document (PDF)
 Title
 Subjecting the CHIMERA supernova code to two hydrodynamic test problems, (i) Riemann problem and (ii) Point blast explosion.
 Creator
 Ahsan, Abu Salah M., Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

A Shock wave as represented by the Riemann problem and a Pointblast explosion are two key phenomena involved in a supernova explosion. Any hydrocode used to simulate supernovae should be subjected to tests consisting of the Riemann problem and the Pointblast explosion. L. I. Sedov's solution of Pointblast explosion and Gary A. Sod's solution of a Riemann problem have been rederived here from one dimensional fluid dynamics equations . Both these problems have been solved by using the idea...
Show moreA Shock wave as represented by the Riemann problem and a Pointblast explosion are two key phenomena involved in a supernova explosion. Any hydrocode used to simulate supernovae should be subjected to tests consisting of the Riemann problem and the Pointblast explosion. L. I. Sedov's solution of Pointblast explosion and Gary A. Sod's solution of a Riemann problem have been rederived here from one dimensional fluid dynamics equations . Both these problems have been solved by using the idea of Selfsimilarity and Dimensional analysis. The main focus of my research was to subject the CHIMERA supernova code to these two hydrodynamic tests. Results of CHIMERA code for both the blast wave and Riemann problem have then been tested by comparing with the results of the analytic solution.
Show less  Date Issued
 2008
 PURL
 http://purl.flvc.org/FAU/172665
 Subject Headings
 Mathematical physics, Continuum mechanics, Number theory, Supernovae, Data processing, Shock waves, Fluid dynamics
 Format
 Document (PDF)