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 Title
 Hydrodynamic analysis of ocean current turbines using vortex lattice method.
 Creator
 Goly, Aneesh, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The main objective of the thesis is to carry out a rigorous hydrodynamic analysis of ocean current turbines and determine power for a range of flow and geometric parameters. For the purpose, a computational tool based on the vortex lattice method (VLM) is developed. Velocity of the flow on the turbine blades, in relation to the freestream velocity, is determined through induction factors. The geometry of trailing vortices is taken to be helicoidal. The VLM code is validated by comparing its...
Show moreThe main objective of the thesis is to carry out a rigorous hydrodynamic analysis of ocean current turbines and determine power for a range of flow and geometric parameters. For the purpose, a computational tool based on the vortex lattice method (VLM) is developed. Velocity of the flow on the turbine blades, in relation to the freestream velocity, is determined through induction factors. The geometry of trailing vortices is taken to be helicoidal. The VLM code is validated by comparing its results with other theoretical and experimental data corresponding to flows about finiteaspect ratio foils, swept wings and a marine current turbine. The validated code is then used to study the performance of the prototype gulfstream turbine for a range of parameters. Power and thrust coefficients are calculated for a range of tip speed ratios and pitch angles. Of all the cases studied, the one corresponding to tip speed ratio of 8 and uniform pitch angle 20 produced the maximum power of 41.3 [kW] in a current of 1.73 [m/s]. The corresponding power coefficient is 0.45 which is slightly less than the Betz limit power coefficient of 0.5926. The VLM computational tool developed for the research is found to be quite efficient in that it takes only a fraction of a minute on a regular laptop PC to complete a run. The tool can therefore be efficiently used or integrated into software for design optimization.
Show less  Date Issued
 2010
 PURL
 http://purl.flvc.org/FAU/2683131
 Subject Headings
 Marine turbines, Mathematical models, Water currents, Forecasting, Mathematical models, Aerodynamics, Mathematics, Finite element method
 Format
 Document (PDF)
 Title
 NOISE PREDICTION METHODS.
 Creator
 Perry, Nicole Kent, Glegg, Stewart, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
 Abstract/Description

Noise prediction methods are necessary in aspects of aerodynamic and hydrodynamic engineering. Predictive models of noise from rotating machinery ingesting turbulence is of much interest and relatively recently studied. This thesis presents a numerical method processed in a series of three codes that was written and edited to receive input for geometrical features of rotating machinery, as well as, adjustments to turbulent operating conditions. One objective of this thesis was to create a...
Show moreNoise prediction methods are necessary in aspects of aerodynamic and hydrodynamic engineering. Predictive models of noise from rotating machinery ingesting turbulence is of much interest and relatively recently studied. This thesis presents a numerical method processed in a series of three codes that was written and edited to receive input for geometrical features of rotating machinery, as well as, adjustments to turbulent operating conditions. One objective of this thesis was to create a platform of analysis for any rotor design to obtain five parameters necessary for noise prediction; 1) the hydrodynamic inflow angle to each blade section, 2) chord length as a function of radius, 3) the cylindrical radius of each blade section, 4) & 5) the leading edge as a function of span in both the rotorplane and as a function of axial distance downstream. Another objective of this thesis was to use computational fluid dynamics (CFD), specifically by using a Reynold’sAveraged NavierStokes (RANS) Shear Stress Transport (SST) 𝑘 − 𝜔 model simulation in ANSYS Fluent, to obtain the turbulent kinetic energy distribution, also necessary in the noise prediction method presented. The purpose of collecting the rotor geometry data and turbulent kinetic energy data was to input the values into the first of the series of codes and run the calculation so that the output spectra could be compared to experimental noise measurements conducted at the Stability Wind Tunnel at Virginia Tech. The comparison shows that the prediction method results in data that can be reliable if careful attention is payed to the input parameters and the length scale used for analysis. The significance of this research is the noise prediction method presented and used simplifies the model of turbulence by using a correlation function that can be determined by a onedimensional function while also simplifying the iterations completed on rotor blade to calculate the unsteady forces.
Show less  Date Issued
 2020
 PURL
 http://purl.flvc.org/fau/fd/FA00013487
 Subject Headings
 Noise, Aerodynamic noise, Hydrodynamics, Noise controlMathematical models
 Format
 Document (PDF)
 Title
 On the Low Order Model of Turbulence in the Wake of a Cylinder and Airfoil – URANS Approach.
 Creator
 Whelchel, Jeremiah Mark, Glegg, Stewart A. L., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This thesis has described a Reynolds Averaged Navier Stokes approach to modeling turbulence in the wake of a cylinder and airfoil. The mean flow, cross stresses, and twopoint space time correlation structure was analyzed for an untripped cylinder with a Reynolds number based on the cylinder diameter and freestream velocity of 60,000. The same features were also analyzed using this approach for an untripped NACA 0012 airfoil with a Reynolds number based on the airfoil chord and freestream...
Show moreThis thesis has described a Reynolds Averaged Navier Stokes approach to modeling turbulence in the wake of a cylinder and airfoil. The mean flow, cross stresses, and twopoint space time correlation structure was analyzed for an untripped cylinder with a Reynolds number based on the cylinder diameter and freestream velocity of 60,000. The same features were also analyzed using this approach for an untripped NACA 0012 airfoil with a Reynolds number based on the airfoil chord and freestream velocity of 328,000. These simulation results were compared to experimental and newly developed models for validation. The ultimate goal of this present study was to create the twopoint space time correlation function of a cylinder and airfoil wake using RANS calculations which contributes to a larger study where the sound radiated by an open rotor due to ingestion of turbulence.
Show less  Date Issued
 2018
 PURL
 http://purl.flvc.org/fau/fd/FA00013105
 Subject Headings
 TurbulenceNoiseMathematical models., Aerodynamic noise., Wakes (Aerodynamics)., Reynolds number.
 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
 Noise Radiation From A Cylindrical Embossment Immersed In Turbulent Boundary Layer Flow.
 Creator
 Bryan, Benjamin Skyler, Glegg, Stewart A. L., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This dissertation will consider the sound radiation from forwardfacing steps and a three dimensional cylindrical embossment of very low aspect ratio mounted on a plate. Glegg et al (2014) outlined a theory for predicting the sound radiation from separated flows and applied the method to predicting the sound from forwardfacing steps. In order to validate this theory it has been applied to the results of Catlett et al (2014) and Ji and Wang (2010). This validation study revealed that the...
Show moreThis dissertation will consider the sound radiation from forwardfacing steps and a three dimensional cylindrical embossment of very low aspect ratio mounted on a plate. Glegg et al (2014) outlined a theory for predicting the sound radiation from separated flows and applied the method to predicting the sound from forwardfacing steps. In order to validate this theory it has been applied to the results of Catlett et al (2014) and Ji and Wang (2010). This validation study revealed that the original theory could be adjusted to include a mixed scaling which gives a better prediction. RANS simulations have been performed and used to support the similarities between the forwardfacing step and the cylindrical embossment. The simulations revealed that the cylindrical embossment exhibits a separation zone similar to that of the forwardfacing step. This separation zone has been shown to be the dominant source of noise on the forwardfacing step in previous works and therefore was expected to be the major source of sound from the cylindrical embossment. The sensitivity of this separation zone to the different parameters of the flow has been investigated by performing several simulations with different conditions and geometries. The separation zone was seen to be independent of Reynolds number based on boundary layer thickness but was directly dependent on the height of the cylinder. The theory outlined in Glegg et al (2014) was then reformulated for use with a cylindrical embossment and the predictions have been compared with wind tunnel measurements. The final predictions show good agreement with the wind tunnel measurements and the farfield sound shows a clearly defined directionality that is similar to an axial dipole at low frequencies.
Show less  Date Issued
 2015
 PURL
 http://purl.flvc.org/fau/fd/FA00004484, http://purl.flvc.org/fau/fd/FA00004484
 Subject Headings
 Acoustic models, Aerodynamic noise, Computational fluid dynamcs, Fluid structure interaction, Structural dynamics, Turbulence  Mathematical models
 Format
 Document (PDF)
 Title
 Noise radiation from small steps and cubic roughness elements in turbulent boundary layer flow.
 Creator
 Bryan, Benjamin Skyler, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Ji and Wang (2010) propose that the dominant source of sound from a forward facing step is the stream wise dipole on the face of the step and that sources acting normal to the flow are negligible. Sound radiation normal to flow of forward facing steps has been measured in wind tunnel experiments previously by Farabee and Casarella (1986, 1991) and Catlett (2010). A method for evaluating sound radiation from surface roughness proposed in Glegg and Devenport (2009) has been adapted and applied...
Show moreJi and Wang (2010) propose that the dominant source of sound from a forward facing step is the stream wise dipole on the face of the step and that sources acting normal to the flow are negligible. Sound radiation normal to flow of forward facing steps has been measured in wind tunnel experiments previously by Farabee and Casarella (1986, 1991) and Catlett (2010). A method for evaluating sound radiation from surface roughness proposed in Glegg and Devenport (2009) has been adapted and applied to flow over a forward facing step which addresses the sound normal to the flow that was previously unaccounted for. Farfield radiation predictions based on this method have been compared with wind tunnel measurements and show good agreement. A second method which evaluates the forcing from a vortex convected past surface roughness using RANS calculations and potential flow information is also evaluated.
Show less  Date Issued
 2012
 PURL
 http://purl.flvc.org/FAU/3358330
 Subject Headings
 Turbulence, Mathematical models, Aerodynamic noise, Fluidstructure interaction, Structural dynamics, Acoustic models, Computational fluid dynamcs
 Format
 Document (PDF)
 Title
 Numerical Simulation of an Ocean Current Turbine Operating in a Wake Field.
 Creator
 Pyakurel, Parakram, VanZwieten, James H., Dhanak, Manhar R., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

An Ocean Current Turbine (OCT) numerical simulation for creating, testing and tuning flight and power takeoff controllers, as well as for farm layout optimization is presented. This simulation utilizes a novel approach for analytically describing oceanic turbulence. This approach has been integrated into a previously developed turbine simulation that uses unsteady Blade Element Momentum theory. Using this, the dynamical response and power production of a single OCT operating in ambient...
Show moreAn Ocean Current Turbine (OCT) numerical simulation for creating, testing and tuning flight and power takeoff controllers, as well as for farm layout optimization is presented. This simulation utilizes a novel approach for analytically describing oceanic turbulence. This approach has been integrated into a previously developed turbine simulation that uses unsteady Blade Element Momentum theory. Using this, the dynamical response and power production of a single OCT operating in ambient turbulence is quantified. An approach for integrating wake effects into this single device numerical simulation is presented for predicting OCT performance within a farm. To accomplish this, far wake characteristics behind a turbine are numerically described using analytic expressions derived from wind turbine wake models. These expressions are tuned to match OCT wake characteristics calculated from CFD analyses and experimental data. Turbine wake is characterized in terms of increased turbulence intensities and decreased mean wake velocities. These parameters are calculated based on the performance of the upstream OCT and integrated into the environmental models used by downstream OCT. Simulation results are presented that quantify the effects of wakes on downstream turbine performance over a wide range of relative downstream and cross stream locations for both moored and bottom mounted turbine systems. This is done to enable the development and testing of flight and power takeoff controllers designed for maximizing energy production and reduce turbine loadings.
Show less  Date Issued
 2016
 PURL
 http://purl.flvc.org/fau/fd/FA00004737, http://purl.flvc.org/fau/fd/FA00004737
 Subject Headings
 TurbulenceMathematical models., Marine turbinesMathematical models., Wind turbinesAerodynamicsMathematical models., Structural dynamics., Computational fluid dynamics., Fluid dynamic measurements., Atmospheric circulation.
 Format
 Document (PDF)
 Title
 Dissipation and eddy mixing associated with flow past an underwater turbine.
 Creator
 Reza, Zaqie, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The objective of this thesis is to analyze the flow past an ocean current turbine using a finite volume NavierStokes CFD solver. A full 3D RANS approach in a moving reference frame is used to model the flow. By employing periodic boundary conditions, onethird of the flowfield is analyzed and the output is replicated to other sectors. Following validation of the computation with an experimental study, the flow fields and particle paths for the case of uniform and sheared incoming flows...
Show moreThe objective of this thesis is to analyze the flow past an ocean current turbine using a finite volume NavierStokes CFD solver. A full 3D RANS approach in a moving reference frame is used to model the flow. By employing periodic boundary conditions, onethird of the flowfield is analyzed and the output is replicated to other sectors. Following validation of the computation with an experimental study, the flow fields and particle paths for the case of uniform and sheared incoming flows past a generic turbine with various blade pitch angles are evaluated and analyzed. Flow field and wake expansion are visualized. Eddy viscosity effects and its dependence on flow field conditions are investigated.
Show less  Date Issued
 2010
 PURL
 http://purl.flvc.org/FAU/2683537
 Subject Headings
 Vibration (Aerodynamics), Fine element method, Marine turbines, Mathematical models, Water currents, Forecasting, Computational fluid dynamics
 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
 Numerical Simulation of a Flowfield Around a Hypersonic Missile with Lateral Jets.
 Creator
 Rodriguez, Daniel, Moslemian, Davood, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This work uses computational fluid dynamics to study the flowfield around a hypersonic missile with two lateral jets to provide control in place of control surfaces. The jets exhaust an H2O2 mixture at Mach number of 2.9 with a jet pressure ratio of roughly 10,500. The jets are staggered axially and circumferentially in such a way to produce pitch and yaw. The flowfield of such a jet configuration is characterized at several angles of attack and the corresponding force coefficients and...
Show moreThis work uses computational fluid dynamics to study the flowfield around a hypersonic missile with two lateral jets to provide control in place of control surfaces. The jets exhaust an H2O2 mixture at Mach number of 2.9 with a jet pressure ratio of roughly 10,500. The jets are staggered axially and circumferentially in such a way to produce pitch and yaw. The flowfield of such a jet configuration is characterized at several angles of attack and the corresponding force coefficients and amplification factors are provided. The freestream air and H2O2 plume is treated as inert for the majority of the calculations. Special cases are treated with finite rate chemical kinetics and compared to the inert flowfield to ascertain the effects that chemical reactions have on the force coefficients. It was found that the flowfield was only slightly altered from the familiar one jet flowfield when the second jet is active. The flow topology and vortex structures tend to shift towards the second jet but the overall structure remains the same. The normal force amplification factors are close to unity over the range of angle of attack due to the thrust being so high with the two jet configuration having a lower amplification factor compared to firing a single jet. Treating the flowfield as chemically reacting did not affect the force values much: the difference being 0.3% for an angle of attack of 0°.
Show less  Date Issued
 2017
 PURL
 http://purl.flvc.org/fau/fd/FA00004893, http://purl.flvc.org/fau/fd/FA00004893
 Subject Headings
 Aerodynamics, Hypersonic., Nonequilibrium thermodynamics., AerothermodynamicsMathematica., Hypersonic planesDesign and constructionMathematical models., VortexmotionMathematical models.
 Format
 Document (PDF)
 Title
 Rainwindinduced cable vibrations in cablestayed bridges.
 Creator
 Calle, Oscar F., Reddy, Dronnadula V., Florida Atlantic University, College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
 Abstract/Description

This research is aimed at investigating and analyzing the rainwindinduced cable vibration phenomena experienced in cables of cablestayed bridges and also the countermeasures employed by engineers to mitigate the largeamplitude vibration problem reported by various researchers around the world. In order to investigate the problem of the water rivulet creation at the top of the cable surface, a singledegreeoffreedom (SDOF) analytical model was developed and analyzed. This thesis studies...
Show moreThis research is aimed at investigating and analyzing the rainwindinduced cable vibration phenomena experienced in cables of cablestayed bridges and also the countermeasures employed by engineers to mitigate the largeamplitude vibration problem reported by various researchers around the world. In order to investigate the problem of the water rivulet creation at the top of the cable surface, a singledegreeoffreedom (SDOF) analytical model was developed and analyzed. This thesis studies the aerodynamic instability of cables in cablestayed bridges by doing literature review of a typical insitu test, developing a single degreeoffreedom (SDOF) analytical model, and an ANSYS finite element model. Furthermore, a linear viscous damper that acts as a countermeasure to the large amplitudes of vibration is reported and analyzed. The suppression characteristics and damper effectiveness of such countermeasure are summarized.
Show less  Date Issued
 2014
 PURL
 http://purl.flvc.org/fau/fd/FA00004271, http://purl.flvc.org/fau/fd/FA00004271
 Subject Headings
 Bridges  Aerodynamics, Bridges  Vibration  Prevention, Cable stayed bridges  Maintenance and repair, Damping (Mechanics), Structural dynamics, Vibration  Mathematical models, Wind resistant design
 Format
 Document (PDF)