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Title: Vortex street wakes downstream of truncated and full cylinders in a rotating fluid.
Creator: Leader, Bram., Florida Atlantic University, Marshall, Jeffrey S., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: An experimental study has been conducted to examine the flow field about and the wake behind truncated cylindrical obstacles of varying height, which are towed through a fluid with a free surface in a rotating system. The results show the development of a vortex street-type wake downstream of the obstacle for retrograde (westward) flows, even for very small ratios of obstacle height to water layer depth. For short obstacles, a pronounced backward flowing jet is observed, which impinges on the...
Show moreAn experimental study has been conducted to examine the flow field about and the wake behind truncated cylindrical obstacles of varying height, which are towed through a fluid with a free surface in a rotating system. The results show the development of a vortex street-type wake downstream of the obstacle for retrograde (westward) flows, even for very small ratios of obstacle height to water layer depth. For short obstacles, a pronounced backward flowing jet is observed, which impinges on the Taylor column from downstream. Prograde (eastward) flows are found to have a meandering wake that extends farther than eight obstacle diameters downstream and do not exhibit backjetting or vortex street formation. Upwelling is believed to occur within the side boundary layers of the Taylor column, which could play a significant role in deep water production in the ocean.
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Date Issued: 1992
PURL: http://purl.flvc.org/fcla/dt/14827
Subject Headings: Taylor vortices, Fluid dynamics, Vortex-motion
Format: Document (PDF)

Title: Very high frequency MIMO underwater acoustic communications in ports and shallow waters.
Creator: Real, Gaultier., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis presents the development of a Multiple-Input Multiple-Output (MIMO) capable high bit rate acoustic modem operating at high frequencies. A MIMO channel estimation technique based on Least-Squares (LS) estimation is developed here. Channel deconvolution is completed using a Minimum Mean-Square Error (MMSE) Linear Equalizer (LE). An Interference Cancellation Linear Equalizer (ICLE) is used to provide the theoretical limit of the MIMO deconvolution process. The RMSE of the channel...
Show moreThis thesis presents the development of a Multiple-Input Multiple-Output (MIMO) capable high bit rate acoustic modem operating at high frequencies. A MIMO channel estimation technique based on Least-Squares (LS) estimation is developed here. Channel deconvolution is completed using a Minimum Mean-Square Error (MMSE) Linear Equalizer (LE). An Interference Cancellation Linear Equalizer (ICLE) is used to provide the theoretical limit of the MIMO deconvolution process. The RMSE of the channel estimation process was 1.83 % and 6.1810 %, respectively for simulated and experimental data. Using experimental data, the RMSE before MIMO deconvolution process was 141.3 % and dropped down to 60.224 % and to 4.4545 %, respectively after LE and ICLE. At raw reception, the RMSE was 101.83 % and dropped down to 9.36 % and to 1.86 % using respectively LE and ICLE with simulated data.
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Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3333309
Subject Headings: MIMO systems, Wireless communication systems, Underwater acoustics, Fluid dynamics
Format: Document (PDF)

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)

Title: Transport and dispersion of fire extinguishing agents downstream from clutter elements of aircraft engine nacelles.
Creator: Zbeeb, Khaled., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The combination of highly turbulent airflow, flammable fluids, and numerous ignition sources makes aircraft engine nacelles a difficult fire zone to protect. Better understanding of nacelle air flow and how it influences the spread of fires and fire extinguishing agents is needed to improve the efficiency of fire suppression. The first objective was to establish a CFD model for a flow field test section to analyze the transport and dispersion of fire extinguishing agents in the presence of...
Show moreThe combination of highly turbulent airflow, flammable fluids, and numerous ignition sources makes aircraft engine nacelles a difficult fire zone to protect. Better understanding of nacelle air flow and how it influences the spread of fires and fire extinguishing agents is needed to improve the efficiency of fire suppression. The first objective was to establish a CFD model for a flow field test section to analyze the transport and dispersion of fire extinguishing agents in the presence of various clutter elements. To validate the use of the CFD model, the simulation results of the CFD model were compared to the experimental data and they show an agreement with the experimental data. The second objective was to present parametric studies to show the effects of the coflow speed, turbulence intensity and agent droplet size on the transport and dispersion of the agent particles downstream from the clutter elements.
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Date Issued: 2009
PURL: http://purl.flvc.org/FAU/186687
Subject Headings: Airplanes, Nacelles, Safety measures, Airplanes, Fires and fire prevention, Fire extinguishing agents, Testing, Airplanes, Fluid dynamics, Mathematical models
Format: Document (PDF)

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)

Title: Surface pressure fluctuations due to an impinging underexpanded supersonic jet.
Creator: Pundir, Binu., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The impingement of supersonic jets on surfaces is of interest because of its important application to jet blast deflectors (JBD), and short takeoff and vertical landing aircraft (STOVL) during hover. Typically, on an aircraft carrier deck, the impingement of the jet blast on the deflector generates impingement tones, and structural vibrations, not only on the JBD but also on the ship deck. Therefore, apart from direct transmission of jet noise to the gallery level, there is a component of...
Show moreThe impingement of supersonic jets on surfaces is of interest because of its important application to jet blast deflectors (JBD), and short takeoff and vertical landing aircraft (STOVL) during hover. Typically, on an aircraft carrier deck, the impingement of the jet blast on the deflector generates impingement tones, and structural vibrations, not only on the JBD but also on the ship deck. Therefore, apart from direct transmission of jet noise to the gallery level, there is a component of noise transmitted due to the impingement of the jet on the JBD. The objectives of this work are to study the pressure spectra (i) on a flat plate, and separately on a cone due to axisymmetric impingement of a supersonic underexpanded cold jet issuing from a convergent-divergent nozzle and (ii) on a plane jet impinging on a finite plate and an adjoining ground plane due to the impingement of a planar jet on the plate. The characteristics of the surface pressure fluctuations are numerically investiga ted using WIND-US 2.0. The time-dependent, compressible Euler equations for perfect gas are employed for the present computations. The impingement distance between the jet nozzle and the deflector plate, and the plate inclination with respect to the incident jet are varied. The impingement zone stagnation bubble and a high-speed radial jet with several embedded structures (shocklets) were identified on the perpendicular plate. Flows involving cones reveal the presence of detached cone shocks, enclosing a recirculation zone. The location and magnitude of the peak pressure on the cone surface are a strong function of the cone apex angle. For the two-dimensional jet impingement on angled plate the peak value of pressure occurs at normal jet impingement. The pressure at the intersection point of the plate and the ground plane is sometimes higher than the peak pressure on the plate. Beyond this point there is a sharp decrease in pressure. As the flow accelerates, an oblique shock is, Beyond this point there is a sharp decrease in pressure. As the flow accelerates, an oblique shock is sometimes formed in this grazing flow region. A recirculation region at the lower lip of the nozzle was observed for all the separation distances and plate inclinations.
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Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3333308
Subject Headings: Systems engineering, Jet nozzles, Design and construction, Jets, Fluid dynamics, Heat, Transmission
Format: Document (PDF)

Title: Simulation and modeling of flow field around a horizontal axis wind turbine (HAWT) using RANS method.
Creator: Sargsyan, Armen., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The principal objective of the proposed CFD analysis is to investigate the flow field around a horizontal axis wind turbine rotor and calculate the turbine's power. A full three dimensional computational fluid dynamics method based on Reynolds Averaged Navier Stokes approach was used in this study. The wind turbine has three blades and a rotor diameter of six meters. One third of the wind turbine rotor was modeled by means of 120o periodicity in a moving reference frame system. The power...
Show moreThe principal objective of the proposed CFD analysis is to investigate the flow field around a horizontal axis wind turbine rotor and calculate the turbine's power. A full three dimensional computational fluid dynamics method based on Reynolds Averaged Navier Stokes approach was used in this study. The wind turbine has three blades and a rotor diameter of six meters. One third of the wind turbine rotor was modeled by means of 120o periodicity in a moving reference frame system. The power coefficient curve obtained from the CFD results is compared with experimental data obtained by NREL Phase VI rotor experiment. The numerical result for the power coefficient curve shows close agreement with the experimental data. The simulation results include the velocity distribution, pressure distribution along the flow direction, turbulent wake behind the wind turbine, and the turbine's power. The discussion will also include the effect of wind speed on turbine's power.
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Date Issued: 2010
PURL: http://purl.flvc.org/FAU/2979383
Subject Headings: Wind turbines, Aerodynamics, Computer simulation, Fluid dynamics, Computational methods, Vibration (Aerodynamics)
Format: Document (PDF)

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)

Title: Separation flow around airfoil with upstream disturbance by discrete vortex method.
Creator: Li, Feng., Florida Atlantic University, Su, Tsung-Chow, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The discrete vortex method was applied to the calculation of separation flow past NACA 4412 airfoil: Vortex panel was used to represent the body surface and discrete vortices were used to model the wake. Generally the uniform upstream condition is used in the calculation of separation flow. But actually an airfoil could move in wake of other airfoils or disturbed fluid. In this thesis, discrete vortices were used to model the upstream disturbance to investigate the effect of upstream...
Show moreThe discrete vortex method was applied to the calculation of separation flow past NACA 4412 airfoil: Vortex panel was used to represent the body surface and discrete vortices were used to model the wake. Generally the uniform upstream condition is used in the calculation of separation flow. But actually an airfoil could move in wake of other airfoils or disturbed fluid. In this thesis, discrete vortices were used to model the upstream disturbance to investigate the effect of upstream disturbance to the pressure, lift and drag coefficients around the airfoil. Also the animation of separation flow was made on HP workstation using "Starbase" computer graphic package to study the separation process.
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Date Issued: 1991
PURL: http://purl.flvc.org/fcla/dt/14739
Subject Headings: Vortex-motion, Fluid dynamics
Format: Document (PDF)

Title: Seakeeping response of a Surface Effect Ship in near-shore transforming seas.
Creator: Kindel, Michael., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Scale model tests are conducted of a Surface Effect Ship in a near-shore developing sea. A beach is built and installed in a wave tank, and a wavemaker is built and installed in the same wave tank. This arrangement is used to simulate developing sea conditions and a 1:30 scale model SES is used for a series of experiments. Pitch and heave measurements are used to investigate the seakeaping response of the vessel in developing seas. The air-cushion pressure and the vessel speed are varied, and...
Show moreScale model tests are conducted of a Surface Effect Ship in a near-shore developing sea. A beach is built and installed in a wave tank, and a wavemaker is built and installed in the same wave tank. This arrangement is used to simulate developing sea conditions and a 1:30 scale model SES is used for a series of experiments. Pitch and heave measurements are used to investigate the seakeaping response of the vessel in developing seas. The air-cushion pressure and the vessel speed are varied, and the seakeeping results are compared as functions of these two parameters. The experiment results show a distinct correlation between the air-cushion pressure and the response amplitude of both pitch and heave. The results of these experiments are compared against results of a computer model of a Surface Effect Ship (SES).
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3355563
Subject Headings: Naval architecture, Fluid dynamics, Wave motion, Theory of, Ships, Hydrodynamics
Format: Document (PDF)

Title: Numerical simulation tool for moored marine hydrokinetic turbines.
Creator: Hacker, Basil L., Ananthakrishnan, Palaniswamy, VanZwieten, James H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The research presented in this thesis utilizes Blade Element Momentum (BEM) theory with a dynamic wake model to customize the OrcaFlex numeric simulation platform in order to allow modeling of moored Ocean Current Turbines (OCTs). This work merges the advanced cable modeling tools available within OrcaFlex with well documented BEM rotor modeling approach creating a combined tool that was not previously available for predicting the performance of moored ocean current turbines. This tool allows...
Show moreThe research presented in this thesis utilizes Blade Element Momentum (BEM) theory with a dynamic wake model to customize the OrcaFlex numeric simulation platform in order to allow modeling of moored Ocean Current Turbines (OCTs). This work merges the advanced cable modeling tools available within OrcaFlex with well documented BEM rotor modeling approach creating a combined tool that was not previously available for predicting the performance of moored ocean current turbines. This tool allows ocean current turbine developers to predict and optimize the performance of their devices and mooring systems before deploying these systems at sea. The BEM rotor model was written in C++ to create a back-end tool that is fed continuously updated data on the OCT’s orientation and velocities as the simulation is running. The custom designed code was written specifically so that it could operate within the OrcaFlex environment. An approach for numerically modeling the entire OCT system is presented, which accounts for the additional degree of freedom (rotor rotational velocity) that is not accounted for in the OrcaFlex equations of motion. The properties of the numerically modeled OCT were then set to match those of a previously numerically modeled Southeast National Marine Renewable Energy Center (SNMREC) OCT system and comparisons were made. Evaluated conditions include: uniform axial and off axis currents, as well as axial and off axis wave fields. For comparison purposes these conditions were applied to a geodetically fixed rotor, showing nearly identical results for the steady conditions but varied, in most cases still acceptable accuracy, for the wave environment. Finally, this entire moored OCT system was evaluated in a dynamic environment to help quantify the expected behavioral response of SNMREC’s turbine under uniform current.
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Date Issued: 2013
PURL: http://purl.flvc.org/fau/fd/FA0004024
Subject Headings: Fluid dynamics, Hydrodynamics -- Research, Marine turbines -- Mathematical models, Ocean wave power, Structural dynamics
Format: Document (PDF)

Title: Numerical performance prediction for FAU's first generation ocean current turbine.
Creator: Vanrietvelde, Nicolas., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis presents the analytically predicted position, motion, attitude, power output and forces on Florida Atlantic University's (FAU) first generation ocean current turbine for a wide range of operating conditions. These values are calculated using a 7- DOF dynamics simulation of the turbine and the cable that attaches it to the mooring system. The numerical simulation modifications and upgrades completed in this work include developing a wave model including the effects of waves into...
Show moreThis thesis presents the analytically predicted position, motion, attitude, power output and forces on Florida Atlantic University's (FAU) first generation ocean current turbine for a wide range of operating conditions. These values are calculated using a 7- DOF dynamics simulation of the turbine and the cable that attaches it to the mooring system. The numerical simulation modifications and upgrades completed in this work include developing a wave model including the effects of waves into the simulation, upgrading the rotor model to specify the number of blades and upgrading the cable model to specify the number of cable elements. This enhanced simulation is used to quantify the turbine's performance in a wide range of currents, wave fields and when stopping and starting the rotor. For a uniform steady current this simulation predicts that when the rotor is fixed in 1.5 m/s current the drag on the turbine is 3.0 kN, the torque on the rotor is 384 N-m, the turbine roll and pitch are 2.4º and -1.2º . When the rotor is allowed to spin up to the rotational velocity where the turbine produces maximum power, the turbine drag increases to 7.3 kN, the torque increases to 1482 N-m, the shaft power is 5.8 kW, the turbine roll increases to 9º and the turbine pitch stays constant. Subsequently, a sensitivity analysis is done to evaluate changes in turbine performance caused by changes in turbine design and operation. This analysis show, among other things, that a non-axial flow on the turbine of up to 10º has a minimal effect on net power output and that the vertical stable position of the turbine varies linearly with the weight/buoyancy of the turbine with a maximum variation of 1.77 m for each increase or decrease of 1 kg at a current speed of 0.5 m/s.
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Date Issued: 2009
PURL: http://purl.flvc.org/FAU/2182033
Subject Headings: Marine turbines, Mathematical models, Structural dynamics, Rotors, Design and construction, Testing, Fluid dynamics
Format: Document (PDF)

Title: Numerical models to simulate underwater turbine noise levels.
Creator: Lippert, Renee'., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This work incorporates previous work done by Guerra and the application of fluid dynamics. The structure attached to the turbine will cause unsteady fluctuations in the flow, and ultimately affect the acoustic pressure. The work of Guerra is based on a lot of assumptions and simplifications to the geometry of the turbine and structure. This work takes the geometry of the actual turbine, and uses computational fluid dynamic software to numerically model the flow around the turbine structure....
Show moreThis work incorporates previous work done by Guerra and the application of fluid dynamics. The structure attached to the turbine will cause unsteady fluctuations in the flow, and ultimately affect the acoustic pressure. The work of Guerra is based on a lot of assumptions and simplifications to the geometry of the turbine and structure. This work takes the geometry of the actual turbine, and uses computational fluid dynamic software to numerically model the flow around the turbine structure. Varying the angle of the attack altered the results, and as the angle increased the noise levels along with the sound pulse, and unsteady loading increased. Increasing the number of blades and reducing the chord length both reduced the unsteady loading.
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3355622
Subject Headings: Underwater acoustics, Mathematical models, Turbines, Vibration, Mathematical models, Fluid dynamics
Format: Document (PDF)

Title: Mobility power flow (MPF) approach applied to fluid-loaded shells with ring discontinuities.
Creator: McCain, Thomas Scott., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The vibrational and acoustic characteristics of fluid-loaded, cylindrical shells with single or multiple, aperiodically-spaced ring discontinuities are studied using an approach based on the mobility power flow (MPF) method and a hybrid numerical/analytical method for the evaluation of the velocity Green's function of the shell. The discontinuities are associated with internal structures coupled to the shell via ring junctions. The approach is a framework allowing alternative shell and/or...
Show moreThe vibrational and acoustic characteristics of fluid-loaded, cylindrical shells with single or multiple, aperiodically-spaced ring discontinuities are studied using an approach based on the mobility power flow (MPF) method and a hybrid numerical/analytical method for the evaluation of the velocity Green's function of the shell. The discontinuities are associated with internal structures coupled to the shell via ring junctions. The approach is a framework allowing alternative shell and/or internal structure models to be used. The solution consists of the net vibrational power flow between the shell and internal structure(s) at the junction(s), the shell's velocity Green's function, and the far-field acoustic pressure. Use of the MPF method is advantageous because the net power flow solution can be used as a diagnostic tool in ascertaining the proper coupling between the shell and internal structure(s) at the junction(s). Results are presented for two canonical problems: an infinite, thin cylindrical shell, externally fluid-loaded by a heavy fluid, coupled internally to: (1) a single damped circular plate bulkhead, and (2) a double bulkhead consisting of two identical damped circular plates spaced a shell diameter apart. Two excitation mechanisms are considered for each model: (1) insonification of the shell by an obliquely-incident, acoustic plane wave, and (2) a radial ring load applied to the shell away from the junction(s). The shell's radial velocity Green's function and far-field acoustic pressure results are presented and analyzed to study the behavior of each model. In addition, a comparison of these results accentuates the qualitative difference in the behavior between the single and multiple junction models. When multiple internal structures are present, the results are strongly influenced by inter-junction coupling communicated through the shell and the fluid. Results are presented for circumferential modes n = 0 & 2. The qualitative differences in the results for modes n = 0 and n = 2 (indicative of all modes n > 0ified in the far-field acoustic pressure and velocity Green's function response with the characteristics of the shell and internal plate bulkhead. The results for the single junction model demonstrate the significance of the shell's membrane waves on the reradiation of acoustic energy from the shell; however, when multiple junctions are present, inter-junction coupling results in a significant broad acoustic scattering pattern. Using the results and analysis presented here, a better understanding can be obtained of fluid-loaded shells, which can be used to reduce the strength of the acoustic pressure field produced by the shell.
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Date Issued: 1996
PURL: http://purl.flvc.org/fcla/dt/12490
Subject Headings: Shells (Engineering)--Vibration, Cylinders--Vibration, Fluid dynamics, Sound--Transmission
Format: Document (PDF)

Title: Methodology for fault detection and diagnostics in an ocean turbine using vibration analysis and modeling.
Creator: Mjit, Mustapha., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis describes a methodology for mechanical fault detection and diagnostics in an ocean turbine using vibration analysis and modeling. This methodology relies on the use of advanced methods for machine vibration analysis and health monitoring. Because of some issues encountered with traditional methods such as Fourier analysis for non stationary rotating machines, the use of more advanced methods such as Time-Frequency Analysis is required. The thesis also includes the development of...
Show moreThis thesis describes a methodology for mechanical fault detection and diagnostics in an ocean turbine using vibration analysis and modeling. This methodology relies on the use of advanced methods for machine vibration analysis and health monitoring. Because of some issues encountered with traditional methods such as Fourier analysis for non stationary rotating machines, the use of more advanced methods such as Time-Frequency Analysis is required. The thesis also includes the development of two LabVIEW models. The first model combines the advanced methods for on-line condition monitoring. The second model performs the modal analysis to find the resonance frequencies of the subsystems of the turbine. The dynamic modeling of the turbine using Finite Element Analysis is used to estimate the baseline of vibration signals in sensors locations under normal operating conditions of the turbine. All this information is necessary to perform the vibration condition monitoring of the turbine.
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Date Issued: 2009
PURL: http://purl.flvc.org/FAU/369198
Subject Headings: Marine turbines, Mathematical models, Fluid dynamics, Structural dynamics, Composite materials, Mathematical models, Elastic analysis (Engineering)
Format: Document (PDF)

Title: Investigation of trapped vortex combustion using hydrogen-rich fuels.
Creator: Zbeeb, Khaled., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The combustion process of a fuel is a challenging subject when it comes to analyze its performance and resultant emissions. The main task of this study is to optimize the selection of a hydrogen-rich fuel based on its performance and emissions. Computational Fluid Dynamics analysis is performed to test the combustion performance and emissions from the vortex trapped combustor when natural gas fuel (methane) is replaced with renewable and alternative fuels such as hydrogen and synthesis gas....
Show moreThe combustion process of a fuel is a challenging subject when it comes to analyze its performance and resultant emissions. The main task of this study is to optimize the selection of a hydrogen-rich fuel based on its performance and emissions. Computational Fluid Dynamics analysis is performed to test the combustion performance and emissions from the vortex trapped combustor when natural gas fuel (methane) is replaced with renewable and alternative fuels such as hydrogen and synthesis gas. Correlation graphs for the trapped vortex combustor performance and NOx, CO, and CO2 emissions for various types of fuels with different compositions and heat of combustion values were established. Methane, Hydrogen and 10 different syngas fuels were analyzed in this study using computational fluid dynamics numerical method. The trapped vortex combustor that represents an efficient and compact combustor for flame stability was investigated. The TVC consists of a fore body and two after body disks . These components are all encircled with a Pyrex tube. The purpose of the after body disks is to create the vortex wakes that will enhance the combustion process and minimize the NOx emissions. The TVC CFD model was validated by comparing the CFD model results using propane fuel with existing experimental results that were established in Rome, Italy. The static temperature distribution and NOx, CO emissions, combustor efficiency and total pressure drop results of the three dimensional CFD model were similar to the experimental data. Effects of H2/CO and H2/CH4 ratios and the mass fraction of each constituent of syngas fuels and Hydrogen-Methane fuel mixture on the TVC performance and emissions were investigated., Moreover, the fuel injector Reynolds number and Lower heating values for Methane, Hydrogen and 10 syngas fuels on the TVC performance and emissions were also investigated. Correlation plots for the NOx, CO and CO2 emissions versus the fuel injector Reynolds number and low heating value were established. These correlation curves can be used as a fair design diagram to optimize the fuel selection process for aerospace and electrical power plant applications.
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Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3334096
Subject Headings: Hydrogen as fuel, Research, Combustion chambers, Vortex-motion, Fluid dynamics
Format: Document (PDF)

Title: Investigation of marine waterjet inlets during turning maneuvers.
Creator: Duerr, Phillip S., von Ellenrieder, Karl, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Numerical simulations of waterjet inlets have been conducted in order to understand inlet performance during ship turning maneuvers. During turning maneuvers waterjet systems may experience low efficiency, cavitation, vibration, and noise. This study found that during turns less energy arrived at the waterjet pump relative to operating straight ahead, and that the flow field at the entrance of the waterjet pump exhibited a region of both low pressure and low axial velocity. The primary reason...
Show moreNumerical simulations of waterjet inlets have been conducted in order to understand inlet performance during ship turning maneuvers. During turning maneuvers waterjet systems may experience low efficiency, cavitation, vibration, and noise. This study found that during turns less energy arrived at the waterjet pump relative to operating straight ahead, and that the flow field at the entrance of the waterjet pump exhibited a region of both low pressure and low axial velocity. The primary reason for the change in pump inflow uniformity is due to a streamwise vortex. In oblique inflow the hull boundary layer separates when entering the inlet and wraps up forming the streamwise vortex. These changes in pump inflow during turning maneuvers will result in increased unsteady loading of the pump rotor and early onset of pump rotor cavitation.
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Date Issued: 2015
PURL: http://purl.flvc.org/fau/fd/FA00004364, http://purl.flvc.org/fau/fd/FA00004364
Subject Headings: Fluid dynamics, Ships--Hydrodynamics, Ships--Maneuverability--Simulation methods, Ship handling--Simulation methods, Ship propulsion, Stability of ships, Oceanographic instruments--Evaluation
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.
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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: GALLOPING OF AN ELASTICALLY SUPPORTED BLUFF BODY IN TURBULENT FLOW.
Creator: Li, Qiang, Florida Atlantic University, Lin, Y. K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The phenomenon of flow-induced vibration is found in many engineering systems. The fluid flow generates forces on the structure that cause motion of the structure. In turn, the structural motion changes the angle of attack between the flow and the structure, hence the forces on the structure. Furthermore, turbulence generally exists in a natural fluid flow; namely, the fluid velocity contains a random part. Thus, the problem is formulated as a nonlinear system under random excitations. This...
Show moreThe phenomenon of flow-induced vibration is found in many engineering systems. The fluid flow generates forces on the structure that cause motion of the structure. In turn, the structural motion changes the angle of attack between the flow and the structure, hence the forces on the structure. Furthermore, turbulence generally exists in a natural fluid flow; namely, the fluid velocity contains a random part. Thus, the problem is formulated as a nonlinear system under random excitations. This thesis is focused on one type of motion known as galloping. A mathematical model for the motion of an elastically supported square cylinder in turbulent flow is developed. The physical nonlinear equation is converted to ideal stochastic differential equations of the Ito type using the stochastic averaging method. The probability density for the motion amplitude and the values for the most probable amplitudes are obtained for various mean flow velocities and turbulence levels.
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Date Issued: 1987
PURL: http://purl.flvc.org/fcla/dt/14361
Subject Headings: Random vibration--Mathematical models, Turbulence, Fluid dynamics
Format: Document (PDF)

Title: Finite Element Modeling and Fatigue Analysis of Composite Turbine Blades under Random Ocean Current and Turbulence.
Creator: Canino, Marco M., Mahfuz, Hassan, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Several modifications have been implemented to numerical simulation codes based on blade element momentum theory (BEMT), for application to the design of ocean current turbine (OCT) blades. The modifications were applied in terms of section modulus and include adjustments due to core inclusion, buoyancy, and added mass. Hydrodynamic loads and mode shapes were calculated using the modified BEMT based analysis tools. A 3D model of the blade was developed using SolidWorks. The model was...
Show moreSeveral modifications have been implemented to numerical simulation codes based on blade element momentum theory (BEMT), for application to the design of ocean current turbine (OCT) blades. The modifications were applied in terms of section modulus and include adjustments due to core inclusion, buoyancy, and added mass. Hydrodynamic loads and mode shapes were calculated using the modified BEMT based analysis tools. A 3D model of the blade was developed using SolidWorks. The model was integrated with ANSYS and several loading scenarios, calculated from the modified simulation tools, were applied. A complete stress and failure analysis was then performed. Additionally, the rainflow counting method was used on ocean current velocity data to determine the loading histogram for fatigue analysis. A constant life diagram and cumulative fatigue damage model were used to predict the OCT blade life. Due to a critical area of fatigue failure being found in the blade adhesive joint, a statistical analysis was performed on experimental adhesive joint data.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004727, http://purl.flvc.org/fau/fd/FA00004727
Subject Headings: Composite materials -- Fatigue, Finite element method, Fluid dynamics, Marine turbines -- Mathematical models, Ocean wave power, Structural dynamics
Format: Document (PDF)

Mathematical models (12)	+ -
Structural dynamics (8)	+ -
Marine turbines (7)	+ -
Testing (7)	+ -
Vortex-motion (6)	+ -

Design and construction (5)	+ -
Vibration (4)	+ -
Flow visualization (3)	+ -
Turbines (3)	+ -
Underwater acoustics (3)	+ -
Boundary layer control (2)	+ -
Combustion chambers (2)	+ -
Composite materials (2)	+ -
Concrete (2)	+ -
Corrosion (2)	+ -
Hydrodynamics (2)	+ -
Marine turbines -- Mathematical models (2)	+ -
Ocean wave power (2)	+ -
Reinforced concrete (2)	+ -
Rotors (2)	+ -
Ships (2)	+ -
Acoustic energy (1)	+ -
Aerodynamics (1)	+ -
Airplanes (1)	+ -
Blades (1)	+ -
Chebyshev polynomials (1)	+ -
Chemical resistance (1)	+ -
Chlorides (1)	+ -
Composite materials -- Fatigue (1)	+ -

College of Engineering and Computer Science (35)	+ -
Florida Atlantic University (14)	+ -
Marshall, Jeffrey S. (2)	+ -
Su, Tsung-Chow (2)	+ -
Zbeeb, Khaled. (2)	+ -

Ananthakrishnan, Palaniswamy (1)	+ -
Asseff, Nicholas S. (1)	+ -
Canino, Marco M. (1)	+ -
Cuschieri, Joseph M. (1)	+ -
Dhanak, Manhar (1)	+ -
Dhanak, Manhar R. (1)	+ -
Duerr, Phillip S. (1)	+ -
Echevarria, Victor Anthony. (1)	+ -
Elishakoff, Isaac (1)	+ -
Francke, Kristina (1)	+ -
Guerra, Julian. (1)	+ -
Hacker, Basil L. (1)	+ -
Jagannathan, Arjun. (1)	+ -
KIM, SOO YONG. (1)	+ -
Kaiser, Khaled. (1)	+ -
Khuc, Hiep Hieu. (1)	+ -
Kim, Hung Soo. (1)	+ -
Kindel, Michael. (1)	+ -
Lakitosh, Fnu (1)	+ -
Leader, Bram. (1)	+ -
Li, Ceji. (1)	+ -
Li, Feng. (1)	+ -
Li, Qiang (1)	+ -
Lin, Y. K. (1)	+ -

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