View All Items

Title: A numerical study of bluff body aerodynamics by vortex method.
Creator: He, Fusen., Florida Atlantic University, Su, Tsung-Chow, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Vortex methods are grid-free; therefore, their use avoids a number of shortcomings of Eulerian, grid-based 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 grid-free; therefore, their use avoids a number of shortcomings of Eulerian, grid-based 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 Navier-Stokes 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 Navier-Stokes 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 near-wall vorticity when obtaining numerical solutions for the Navier-Stokes 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: Vortex-motion, 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 small-scale 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: Far-Field 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, non-uniform 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, non-uniform 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 aero-acoustic 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, Jean-Baptiste., 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 Navier-Stokes (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 Navier-Stokes (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 walk-through of the entire process utilized to approximate the flow ingested by a Sevik-type rotor based on solutions to the Reynolds Averaged Navier-Stokes equations (RANS). The Multiple Reference Frame fluid model is utilized by the code of ANSYS-FLUENT 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 walk-through of the entire process utilized to approximate the flow ingested by a Sevik-type rotor based on solutions to the Reynolds Averaged Navier-Stokes equations (RANS). The Multiple Reference Frame fluid model is utilized by the code of ANSYS-FLUENT 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 3x10-7. 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 non-condensable 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. Low-temperature 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. Low-temperature 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 gas-tension 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 kilowatt-hour per cubic meter, consumed by water pumping and by removal of non-condensable 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 two-dimensional hydrodynamic analysis of flapping foils for the propulsion of underwater vehicles using a source-vortex 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 two-dimensional, incompressible and inviscid. The analysis is first considered for the...
Show moreThis thesis presents two-dimensional hydrodynamic analysis of flapping foils for the propulsion of underwater vehicles using a source-vortex 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 two-dimensional, 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 free-surface 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 non-linear, non-hydrostatic Boussinesq equations in the vorticity-streamfunction formulation. A number of important features of internal waves over topography are captured with the present model, including the onset of wave-breaking at sub-critical 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 root-type 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 2-D time-resolved particle image velocimetry (PIV), and flow visualization. The result was analyzed to present time-averaged and time-resolved 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 currents--Mathematical 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 shut-in 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 shut-in 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 particle-particle interaction mechanisms. This dissertation utilizes both experimental and numerical approaches to advance the state of the art in particle-particle interactions in various test conditions. Experimentally, the study utilizes high-speed imaging coupled with particle tracking velocimetry (PTV) and particle image velocimetry (PIV) to provide a space and time-resolved investigation of both two-particle and multi-particle 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 -- 1881-1963, 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, Tsung-Chow, 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 long-term 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: Air-supported structures--Design and construction., Remote submersibles--Design 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 Point-blast 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 Point-blast explosion. L. I. Sedov's solution of Point-blast explosion and Gary A. Sod's solution of a Riemann problem have been re-derived 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 Point-blast 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 Point-blast explosion. L. I. Sedov's solution of Point-blast explosion and Gary A. Sod's solution of a Riemann problem have been re-derived here from one dimensional fluid dynamics equations . Both these problems have been solved by using the idea of Self-similarity 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)

Fluid mechanics (10)	+ -
Computational fluid dynamics (5)	+ -
Fluid dynamic measurements (4)	+ -
Fluid mechanics -- Mathematical models (4)	+ -
Mathematical models (4)	+ -

Renewable energy sources (3)	+ -
Turbulence (3)	+ -
Turbulence -- Mathematical models (3)	+ -
Acoustical engineering (2)	+ -
Continuum mechanics (2)	+ -
Fluid dynamics (2)	+ -
Fluid mechanics. (2)	+ -
Motion control systems (2)	+ -
Turbomachines -- Fluid dynamics (2)	+ -
Adaptive control systems. (1)	+ -
Aerodynamic noise (1)	+ -
Aerodynamics -- Mathematical models (1)	+ -
Aeroelasticity (1)	+ -
Air-supported structures--Design and construction. (1)	+ -
Alloys (1)	+ -
Analysis of covariance (1)	+ -
Atmospheric models. (1)	+ -
Boundary layer control (1)	+ -
Chebyshev polynomials (1)	+ -
Chemistry, Physical and theoretical (1)	+ -
Computatioinal fluid dynamics (1)	+ -
Corrosion fatigue (1)	+ -
Data processing (1)	+ -
Drag (Aerodynamics) (1)	+ -
Electric power production (1)	+ -

College of Engineering and Computer Science (18)	+ -
Department of Ocean and Mechanical Engineering (17)	+ -
Florida Atlantic University (9)	+ -
Glegg, Stewart A. L. (3)	+ -
Dhanak, Manhar R. (2)	+ -

Su, Tsung-Chow (2)	+ -
Ahsan, Abu Salah M. (1)	+ -
Ananthakrishnan, Palaniswamy (1)	+ -
Blanc, Jean-Baptiste. (1)	+ -
Buono, Armand C. (1)	+ -
Bustos, Julia (1)	+ -
Charles E. Schmidt College of Science (1)	+ -
Curet, Oscar M. (1)	+ -
Department of Computer and Electrical Engineering and Computer Science (1)	+ -
Department of Physics (1)	+ -
Egeland, Matthew Nicklas (1)	+ -
Gaonkar, Gopal H. (1)	+ -
Ghenai, Chaouki (1)	+ -
Grabe, Zachary A. (1)	+ -
Grant, Justin Alexander (1)	+ -
Hafez, Mazen (1)	+ -
He, Fusen. (1)	+ -
Isaza, Francisco (1)	+ -
Jagannathan, Arjun. (1)	+ -
Kawashima, Emilia (1)	+ -
Kazemi, Amirkhosro (1)	+ -
Kim, Myeongsub (1)	+ -
Lachowski, Felipe Ferreira. (1)	+ -
Li, Yanjun (1)	+ -
Lovenbury, James William. (1)	+ -

Search In

Sort Results By:

Narrow results by:

Collection

Topical Subject

Genre

Type of Resource

Language

Creator

Format

Owner