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Numerical models to simulate underwater turbine noise levels
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)
Estimation of the scattering function of fading channels for acoustic communications in shallow waters
Title
Estimation of the scattering function of fading channels for acoustic communications in shallow waters.
Creator
Allemand, Vincent., Florida Atlantic University, Beaujean, Pierre-Philippe
Abstract/Description
The measurement of the Scattering function of time-variant fading channels is of strong interest in the field of underwater acoustic communications, as it indicates the limitations of the channel capacity. It also helps reducing the development time of acoustic communication systems and the need for on-site tests using so-called "fading simulators". The Scattering function is interpreted as the expected power received at a given time-delay and frequency shift for a given signal transmitted...
Show moreThe measurement of the Scattering function of time-variant fading channels is of strong interest in the field of underwater acoustic communications, as it indicates the limitations of the channel capacity. It also helps reducing the development time of acoustic communication systems and the need for on-site tests using so-called "fading simulators". The Scattering function is interpreted as the expected power received at a given time-delay and frequency shift for a given signal transmitted through the acoustic channel. It has been estimated using a fourth-moment method developed by Kailath from 18 to 30 kHz, 8-ms broad-band chirps and 20--28 kHz, 28-ms pseudo noise sequences. These signals were transmitted periodically in the shallow coastal waters of South Florida from a static source, and recorded from a 64-channel receiver array located at a distance of 1000 meters. Spatial beamforming has been applied to study the spatial sensitivity of the scattering function.
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Date Issued
2005
PURL
http://purl.flvc.org/fcla/dt/13230
Subject Headings
Underwater acoustic telemetry, Signal processing--Digital techniques, Underwater acoustics--Mathematical models, Adaptive signal processing
Format
Document (PDF)
Development and implementation of integrated acoustic and oceanographic numerical modeling in coastal regions
Title
Development and implementation of integrated acoustic and oceanographic numerical modeling in coastal regions.
Creator
Walker, Natasha Maria., Florida Atlantic University, Glegg, Stewart A. L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
An integrated coastal ocean and acoustic propagation model has been implemented to determine the effects of the ocean variations on the acoustic propagation field applied specifically to SFOMC. The ocean dynamics were modeled using the sigma coordinate, orthogonal curvilinear grid, Princeton Ocean Model. By using forcing conditions of tide, river runoff, wind and realistic bottom topography, the resulting time variant regional sound velocity outputs from the model were used as inputs to the...
Show moreAn integrated coastal ocean and acoustic propagation model has been implemented to determine the effects of the ocean variations on the acoustic propagation field applied specifically to SFOMC. The ocean dynamics were modeled using the sigma coordinate, orthogonal curvilinear grid, Princeton Ocean Model. By using forcing conditions of tide, river runoff, wind and realistic bottom topography, the resulting time variant regional sound velocity outputs from the model were used as inputs to the range dependent, parabolic equation, acoustic propagation model, RAM. The results show that the fluctuations in the ocean result in scintillation in the acoustic propagation field, and for higher frequencies this variability is uniformly distributed and at times as much as +/-3 dB. High resolution in the POM grid and the range and depth sizes for RAM were important for obtaining reliable simulation results.
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Date Issued
2002
PURL
http://purl.flvc.org/fcla/dt/12901
Subject Headings
Oceanography--Mathematical models, Underwater acoustics--Mathematical models, Coastal engineering
Format
Document (PDF)
Time-dependent multipath modeling for underwater acoustic wave propagation in shallow water
Title
Time-dependent multipath modeling for underwater acoustic wave propagation in shallow water.
Creator
Boulanger, Florent Jacques., Florida Atlantic University, Beaujean, Pierre-Philippe
Abstract/Description
A novel acoustic wave propagation model has been developed to determine the effects of the ocean variations on the acoustic propagation field, and to determine the signal measured by a receiver at any distance from an omnidirectional source. The model accounts for environmental conditions. First, a stationary estimate of the complex sound attenuation is computed as a function of frequency and location, using the parabolic equation numerical technique. For a given range, the vertical profile...
Show moreA novel acoustic wave propagation model has been developed to determine the effects of the ocean variations on the acoustic propagation field, and to determine the signal measured by a receiver at any distance from an omnidirectional source. The model accounts for environmental conditions. First, a stationary estimate of the complex sound attenuation is computed as a function of frequency and location, using the parabolic equation numerical technique. For a given range, the vertical profile of the attenuation frequency spectrum is decomposed in the wave number domain. A specific Doppler shift is associated with each wave number. The space-frequency attenuation filter obtained is applied to the transmitted signal to create time-frequency selective fading. This model has been used to simulate the performance of the General Purpose Acoustic Modem, which transmits MFSK modulated sequences between 15.6 kHz to 32.1 kHz. The range of operation varies from 1 to 5 km, in 15 meters of water. Experimental data have been collected under sea-state 2 conditions. The model has been successfully validated when compared to experimental data and to the Crepeau model.
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Date Issued
2003
PURL
http://purl.flvc.org/fcla/dt/12978
Subject Headings
Underwater acoustics--Mathematical models, Sound--Transmission, Ocean waves--Mathematical models
Format
Document (PDF)
Source speed estimation using a pilot tone in a high-frequency acoustic modem
Title
Source speed estimation using a pilot tone in a high-frequency acoustic modem.
Creator
Kathiroli, Poorani., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
This thesis proposes to estimate the speed of a moving acoustic source by either linear or non linear processing of the resulting Doppler shift present in a high-frequency pilot tone. The source is an acoustic modem (Hermes) which currently uses moving average to estimate and compensate for Doppler shift. A new auto regressive approach to Doppler estimation (labeled IIR method in the text) promises to give a better estimate. The results for a simulated peak velocity of 2 m/s in the presence...
Show moreThis thesis proposes to estimate the speed of a moving acoustic source by either linear or non linear processing of the resulting Doppler shift present in a high-frequency pilot tone. The source is an acoustic modem (Hermes) which currently uses moving average to estimate and compensate for Doppler shift. A new auto regressive approach to Doppler estimation (labeled IIR method in the text) promises to give a better estimate. The results for a simulated peak velocity of 2 m/s in the presence of additive noise showed an RMSE of 0.23 m/s using moving average vs. 0.00018 m/s for the auto regressive approach. The SNR was 75 dB. The next objective was to compare the estimated Doppler velocity obtained using the two algorithms with the experimental values recorded in real time. The setup consisted of a receiver hydrophone attached to a towing carriage that moved with a known velocity with respect to a stationary acoustic source. The source transmitted 375 kHz pilot tone. The received pilot tone data were preprocessed using the two algorithms to estimate both Doppler shift and Doppler velocity. The accuracy of the algorithms was compared against the true velocity values of the carriage. The RMSE for a message from experiments conducted indoor for constant velocity of 0.4 m/s was 0.6055 m/s using moving average, 0.0780 m/s using auto regressive approach. The SNIR was 6.3 dB.
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Date Issued
2011
PURL
http://purl.flvc.org/FAU/3171396
Subject Headings
Underwater acoustics, Measurement, SIgnal processing, Digital techniques, Digital filters (Mathematics), Radio frequency, Mathematical models
Format
Document (PDF)
Characterizing magnetic noise of AUV for use in towed magnetometer study of internal waves
Title
Characterizing magnetic noise of AUV for use in towed magnetometer study of internal waves.
Creator
Tilley, Dylan., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
As part of a project to study internal waves, FAU plans to utilize an AUV to tow a magnetometer to study electromagnetic signatures from internal waves. This research is focused on the electromagnetic noise issues related to using an AUV to tow the magnetic sensor package. There are active sources of electromagnetic noise caused by an AUV that are present in addition to those induced by the Earth's magnetic field and permanent magnets. To characterize the magnetic noise associated with the...
Show moreAs part of a project to study internal waves, FAU plans to utilize an AUV to tow a magnetometer to study electromagnetic signatures from internal waves. This research is focused on the electromagnetic noise issues related to using an AUV to tow the magnetic sensor package. There are active sources of electromagnetic noise caused by an AUV that are present in addition to those induced by the Earth's magnetic field and permanent magnets. To characterize the magnetic noise associated with the AUV magnetometer tow system, the various active source elements were identified, the orientation sensitivity of the sensors being used was determined, and the magnetic anomaly of a similar AUV which may be eventually be used in a magnetic sensing arrangement was measured. The results are used to show the proposed sensing arrangement will likely not achieve the necessary sensitivity to measure subtle internal wave signals.
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Date Issued
2012
PURL
http://purl.flvc.org/FAU/3352881
Subject Headings
Automatic control, Mathematical models, Electromagnetic measurements, Fluctuations (Physics), Oceanographic submersibles, Underwater acoustics
Format
Document (PDF)
A Study of the Underwater Acoustic Propagation in a Turning Basin Modeled as a Three-Dimensional Duct Closed at One End Using the Method of Images
Title
A Study of the Underwater Acoustic Propagation in a Turning Basin Modeled as a Three-Dimensional Duct Closed at One End Using the Method of Images.
Creator
Staska, Matthew D., Beaujean, Pierre-Philippe, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
A computer-efficient model of the underwater acoustic propagation m a shallow, three-dimensional duct closed at one end has been developed using the method of images. Presented in this research is the development of this three-dimensional method of images analysis for a rectangular duct. Using this analysis, a model of the impulse response of the acoustic channel is constructed. Also presented in this work is the actual impulse response collected during field experimentation in the south...
Show moreA computer-efficient model of the underwater acoustic propagation m a shallow, three-dimensional duct closed at one end has been developed using the method of images. Presented in this research is the development of this three-dimensional method of images analysis for a rectangular duct. Using this analysis, a model of the impulse response of the acoustic channel is constructed. Also presented in this work is the actual impulse response collected during field experimentation in the south turning basin of Port Everglades in Fort Lauderdale, Florida. The results demonstrate that the impulse response is modeled with a relative echo magnitude error of 1.62 dB at worst, and a relative echo location error varying between 0% and 4% when averaged across multiple measurements and sensor locations.
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Date Issued
2007
PURL
http://purl.flvc.org/fau/fd/FA00012557
Subject Headings
Underwater acoustics--Measurement, Wave motion, Theory of, Wave equation--Numerical solutions, Sound-waves--Transmission--Mathematical models
Format
Document (PDF)