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- Title
- Characterization of the acoustic signature of an Ocean Explorer class AUV.
- Creator
- Lambe, Frederic Lionel., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The radiated noise from Autonomous Underwater Vehicles (AUV's) can interfere with on-board sensors and with certain type of missions. It is thus important to understand the parameters controlling the AUV self noise. In this thesis, measurement techniques and analyses are developed to investigate the mechanisms contributing to the acoustic noise of an Ocean Explorer class AUV. Measurements of the AUV acoustic signature are performed in a reverberant tank, after the tank is qualified to...
Show moreThe radiated noise from Autonomous Underwater Vehicles (AUV's) can interfere with on-board sensors and with certain type of missions. It is thus important to understand the parameters controlling the AUV self noise. In this thesis, measurement techniques and analyses are developed to investigate the mechanisms contributing to the acoustic noise of an Ocean Explorer class AUV. Measurements of the AUV acoustic signature are performed in a reverberant tank, after the tank is qualified to establish a reliable procedure to measure the AUV source levels. The measurement results are compared that obtained in an anechoic tank and in open-water. Acoustic measurements are correlated with vibration measurements performed on various components of the AUV, in order to identify the dominant components. From the results, some preliminary mitigation procedures to reduce the AUV acoustic signature are developed.
Show less - Date Issued
- 1999
- PURL
- http://purl.flvc.org/fcla/dt/15618
- Subject Headings
- Oceanographic submersibles, Underwater acoustics
- Format
- Document (PDF)
- Title
- Effects of an internal flow on the vibration of thin cylindrical shells.
- Creator
- Leyrat, Gilles F., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The response and the dynamic stability of thin cylindrical shells excited by a point force with an internal heavy medium (water) moving with a constant mean flow velocity are investigated. Two sets of analysis are discussed, one for infinitely long shells and one for shells of finite length. The infinite condition applies to shells which are sufficiently long to be considered infinite. In this case, the solution is obtained by means of a spatial Fourier transform in the axial direction and a...
Show moreThe response and the dynamic stability of thin cylindrical shells excited by a point force with an internal heavy medium (water) moving with a constant mean flow velocity are investigated. Two sets of analysis are discussed, one for infinitely long shells and one for shells of finite length. The infinite condition applies to shells which are sufficiently long to be considered infinite. In this case, the solution is obtained by means of a spatial Fourier transform in the axial direction and a modal decomposition in the circumferential direction. Using this solution, input and transfer accelerances are determined. The results of this part of this analysis show that input accelerances are globally preserved as the mean flow velocity changes. For the transfer accelerances, broadband peaks appear which are caused by the phase matching between propagating waves of different mode numbers. These broadband peaks are shifted and modified by the mean flow velocity. For shells of finite length, simply supported boundary conditions are assumed. In this case, the response is obtained by using a normal mode expansion of the in vacuo shell and the Kirchhof-Helmholtz equation derived for a fluid moving at constant flow velocity and bounded by a perfectly rigid cylinder. For finite shells, the main effect of the flow on the response is to decrease the natural frequencies of the shell. The extent of the change in frequency depends on the circumferential and axial mode numbers. Experimental results are also presented for a pipe shell of radius 0.025m and wall thickness 1.5mm. These results are compared with the analytical results for similar shell and flow condition and the agreement is very good. Using the analysis developed for the response, results are presented on the instabilities that can be induced by the flow. It is found that these instabilities are not restricted to finite pipes, but can also exist for cylindrical shells of infinite extent.
Show less - Date Issued
- 1990
- PURL
- http://purl.flvc.org/fcla/dt/12249
- Subject Headings
- Shells (Engineering)--Vibration
- Format
- Document (PDF)
- Title
- Digital signal processing for a high-resolution three-dimensional sonar imaging system for autonomous underwater vehicles.
- Creator
- Cao, Ping., Florida Atlantic University, Cuschieri, Joseph M., Sudhakar, Raghavan, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
In this dissertation, the digital signal processing techniques required for a 3-D sonar imaging system are examined. The achievable performance of the generated images is investigated by using a combination of theoretical analysis, computer simulation and field experiments. The system consists of a forward looking sonar, with separate projector and receiver. The projector is a line source with an 80 degrees by 1.2 degree beam pattern, which is electronically scanned within a 150 degree sector...
Show moreIn this dissertation, the digital signal processing techniques required for a 3-D sonar imaging system are examined. The achievable performance of the generated images is investigated by using a combination of theoretical analysis, computer simulation and field experiments. The system consists of a forward looking sonar, with separate projector and receiver. The projector is a line source with an 80 degrees by 1.2 degree beam pattern, which is electronically scanned within a 150 degree sector. The receiver is a multi element line array, where each transducer element has a directivity pattern that covers the full sector of view, that is 150 degrees by 80 degrees. The purpose of this sonar system is to produce three dimensional (3-D) images which display the underwater topography within the sector of view up to a range of 200 meters. The principle of operation of the proposed 3-D imaging system differs from other commonly used systems in that it is not based on the intensity of backscatter. The geometries of the targets are obtained from the delay and direction information that can be extracted from the signal backscatter. The acquired data is further processed using an approach based on sequential Fourier transforms to build the 3-D images. With careful selection of the system parameters, the generated images have sufficient quality to be used for AUV tasks such as obstacle avoidance, navigation and object classification. An approach based on a sophisticated two dimensional (2-D) autoregressive (AR) model is explored to further improve the resolution and generate images with higher quality. The real time processing requirements for image generation are evaluated, with the use of dedicated Digital Signal Processing (DSP) chips. A pipeline processing model is analyzed and developed on a selected system.
Show less - Date Issued
- 1992
- PURL
- http://purl.flvc.org/fcla/dt/12317
- Subject Headings
- Sonar, Signal processing--Digital techniques, Three-dimensional display systems, Submersibles
- Format
- Document (PDF)
- Title
- Noise radiation from an open grid bridge.
- Creator
- Tournour, Michel Andre., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
When a vehicle crosses the grid section of an open grid or bascule bridge, a tonal noise is generated. The tonal character of the noise is a consequence of the periodic excitation of both the tire and the grid, that comes from the interaction between the vehicle tire and the periodic grid members. In this thesis, the parameters that control the level and frequency of the generated noise are investigated, with emphasis on understanding the contribution to the overall noise level from the...
Show moreWhen a vehicle crosses the grid section of an open grid or bascule bridge, a tonal noise is generated. The tonal character of the noise is a consequence of the periodic excitation of both the tire and the grid, that comes from the interaction between the vehicle tire and the periodic grid members. In this thesis, the parameters that control the level and frequency of the generated noise are investigated, with emphasis on understanding the contribution to the overall noise level from the vibrations of the grid. Field and laboratory measurements have been performed, together with analytical analysis, on sample grid designs. By determining the acoustic radiation efficiency of the grid, the noise contribution from the grid vibrations is estimated by combing the radiation efficiency with the field measured vibration levels. The results of this study show that the contribution from the grid is small compared to that which may be coming from the vibration of the tire. Without first reducing tire noise, structural modifications to the grid in the form of damping or acoustic baffles will not produce any significant noise reduction.
Show less - Date Issued
- 1994
- PURL
- http://purl.flvc.org/fcla/dt/15046
- Subject Headings
- Bridges--Design and construction, Bridges, Steel plate deck, Bridges--Noise, Noise control, Bridges--Vibration
- Format
- Document (PDF)
- Title
- AN INVESTIGATION OF ENERGY FLOW AND ACOUSTIC RADIATION OF FLUID-LOADED PANELS USING THE ENERGY ACCOUNTANCY CONCEPT.
- Creator
- MAILLET, PHILIPPE LOUIS., Florida Atlantic University, Dunn, Stanley E., Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The energy flow and the acoustic radiation of fluid-loaded panels are investigated using the Energy Accountancy Concept. The various energy components of the systems are defined and studied. Each component is a function of the excitation, the structure, the medium and their coupling. An energy balance equation is written for the system. This method is applied to study the acoustic radiation from a point-excited clamped plate placed on the free surface of a water tank. The radiation efficiency...
Show moreThe energy flow and the acoustic radiation of fluid-loaded panels are investigated using the Energy Accountancy Concept. The various energy components of the systems are defined and studied. Each component is a function of the excitation, the structure, the medium and their coupling. An energy balance equation is written for the system. This method is applied to study the acoustic radiation from a point-excited clamped plate placed on the free surface of a water tank. The radiation efficiency of the plate is measured and compared to previous works. The energy balance equation gives very good results at frequencies between 50 Hz and 12 kHz. An undefined source of energy dissipation is observed in one experiment. The results of this study have shown that the Energy Accountancy Concept can be used to describe the energy flow in a vibrating structure under water-loading.
Show less - Date Issued
- 1986
- PURL
- http://purl.flvc.org/fcla/dt/14289
- Subject Headings
- Acoustic radiation pressure, Vibration--Measurement
- Format
- Document (PDF)
- Title
- Power flow analysis of simple structures.
- Creator
- Rassineux, Jean-Louis Maurice., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A Power Flow approach, where the vibrational Power Flow is expressed in terms of mobility functions is analytically investigated for simple connected structures. Using a Power Flow approach the global structure is divided into a series of substructures and the vibrational Power Flow between the substructures expressed in terms of input and transfer mobilities. Depending on the type and shape of the junction, line or point mobilities may be used. While in the case of point joints, the mobility...
Show moreA Power Flow approach, where the vibrational Power Flow is expressed in terms of mobility functions is analytically investigated for simple connected structures. Using a Power Flow approach the global structure is divided into a series of substructures and the vibrational Power Flow between the substructures expressed in terms of input and transfer mobilities. Depending on the type and shape of the junction, line or point mobilities may be used. While in the case of point joints, the mobility functions are only functions of frequency, for line joints the mobility functions are variables of not just the frequency but also of space. In this thesis the application of the Power Flow method is first demonstrated for an L-shaped beam and the method is then extended to the application of a line junction between two plates forming an L-shaped plate. The results obtained in the two cases are compared to results obtained using Finite Element Analysis or Statistical Energy Analysis.
Show less - Date Issued
- 1988
- PURL
- http://purl.flvc.org/fcla/dt/14439
- Subject Headings
- Structural dynamics
- Format
- Document (PDF)
- Title
- Scattering and response Green's function modeling of a fluid-loaded coated cylindrical shell.
- Creator
- Treffot, Carole., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
An acoustic compliant coating is applied on a fluid-loaded structure to control the radiated pressure, by decoupling the fluid medium from the vibrating surface. In this thesis the problem of an infinite cylindrical shell immersed in a fluid and entirely covered with an acoustic compliant layer, excited either by a ring force or an incident acoustic plane wave is considered. To model this problem two different approaches are used. The first one, which is available in the literature, is based...
Show moreAn acoustic compliant coating is applied on a fluid-loaded structure to control the radiated pressure, by decoupling the fluid medium from the vibrating surface. In this thesis the problem of an infinite cylindrical shell immersed in a fluid and entirely covered with an acoustic compliant layer, excited either by a ring force or an incident acoustic plane wave is considered. To model this problem two different approaches are used. The first one, which is available in the literature, is based on multi-layer shell theory. In this approach the scalar and the vector potential formulation are used to solve for the response and the scattering from the cylinder. The second approach is based on modeling the compliant layer by a normally reacting impedance layer on the surface of the shell. The velocity response Green's function of the shell is found using the hybrid numerical/analytical method. Results for the radiated and scattered pressure from the shell are also presented. The advantage of this second approach is that it can be used to model complex coating geometries. The results obtained with both approaches are compared.
Show less - Date Issued
- 2001
- PURL
- http://purl.flvc.org/fcla/dt/12775
- Subject Headings
- Green's functions, Elastic plates and shells
- Format
- Document (PDF)
- Title
- Scattering of sound from a fluid-loaded cylindrical shell with a finite length mass inhomogeneity.
- Creator
- Lefevre, Thierry Alain., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The problem investigated in this thesis is that of an infinite, fluid-loaded, elastic cylindrical shell with an inhomogeneity of finite length excited by an acoustic plane wave. Seven inhomogeneities are considered to examine the parameters that influence the scattering. A full numerical approach and an iterative approach are developed to solve the shell and acoustic equations of motion expressed in the wavenumber domain. The response Green's function in the spatial domain is obtained using...
Show moreThe problem investigated in this thesis is that of an infinite, fluid-loaded, elastic cylindrical shell with an inhomogeneity of finite length excited by an acoustic plane wave. Seven inhomogeneities are considered to examine the parameters that influence the scattering. A full numerical approach and an iterative approach are developed to solve the shell and acoustic equations of motion expressed in the wavenumber domain. The response Green's function in the spatial domain is obtained using the hybrid analytical numerical technique, while the far-field scattered pressure is obtained by applying the Stationary Phase approximation. An analytical approach for the special case of a concentrated ring is developed, and the results compared to those from the full numerical solution. The range of applicability of the iterative approach is also investigated. The results show that the scattering pattern is a function of the spectral contents of the inhomogeneity distribution, and that the inhomogeneity mass influenced both the scattering pattern, and the scattering level. From the results it was also noted that an oblique angle of incidence steered the main lobe of the scattering pattern in the direction of the incoming acoustic wave. It is also demonstrated that the concentrated ring is usually a poor model to represent inhomogeneity of finite length.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15385
- Subject Headings
- Elastic plates and shells, Sound
- Format
- Document (PDF)
- Title
- Vibrational power flow in thick connected plates.
- Creator
- McCollum, Michele D., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The total vibrational power flow in connected plate structures is investigated using an analytical "Power Flow" approach. The effects of shear and rotary inertia on the flexural wave transmission and the influence of in-plane wave generation at structural discontinuities are included in the analytical model. In formulating a Power Flow model, the structure is divided into substructures whose responses may be determined analytically to obtain expressions for the input and transfer mobilities...
Show moreThe total vibrational power flow in connected plate structures is investigated using an analytical "Power Flow" approach. The effects of shear and rotary inertia on the flexural wave transmission and the influence of in-plane wave generation at structural discontinuities are included in the analytical model. In formulating a Power Flow model, the structure is divided into substructures whose responses may be determined analytically to obtain expressions for the input and transfer mobilities of the substructures. For the case of plate-type structures joined along a line, the mobilities are functions of both frequency and space. The power transmission between the individual plate substructures is then written as a function of these mobility expressions. The structure of concern in this dissertation consists of two plates connected in an L-configuration. In obtaining the expressions for the mobilities, the vibrational response of the individual plates is determined by solving the appropriate equations of motion. In this study the antisymmetric (flexural) motion is described using Mindlin's (1951) thick plate approximation to the three-dimensional equations of motion. The applicability of this thick plate formulation is limited to frequencies below the frequency of the first antisymmetric mode of thickness-shear vibration of the plate. The symmetric (in-plane) motion of the plates is described using the generalized theory of plane stress which neglects the direct coupling of the in-plane motion with the thickness vibration modes, and is therefore valid only for frequencies which are lower than the frequency of the first mode of pure thickness vibration of the plate. The results for the power transmission in the L-plate obtained using the Power Flow formulation are verified at high frequencies by comparison with the results obtained using the Statistical Energy Analysis (SEA) technique. The SEA formulation for the L-plate is based on Mindlin's equations for flexural motion and the theory of generalized plane stress for in-plane vibration. The results of the Power Flow formulation are verified at low frequencies by the results obtained using a Finite Element model of the L-shaped plate.
Show less - Date Issued
- 1988
- PURL
- http://purl.flvc.org/fcla/dt/11929
- Subject Headings
- Plates (Engineering)--Vibration
- Format
- Document (PDF)
- Title
- Interaction of acoustic waves generated by coupled finite fluid-loaded plates.
- Creator
- Kaina, Rachid., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The response of fluid-loaded plates has been extensively studied in the past. However, most of the work deals with either infinite plates or finite plates with particular boundary conditions and the results are generally presented only in the limit of small wavelengths compared with the dimensions of the plates. Furthermore, the problem of coupled finite plates where both the acoustic interaction and structural interaction are included in the solution has not been considered. In this...
Show moreThe response of fluid-loaded plates has been extensively studied in the past. However, most of the work deals with either infinite plates or finite plates with particular boundary conditions and the results are generally presented only in the limit of small wavelengths compared with the dimensions of the plates. Furthermore, the problem of coupled finite plates where both the acoustic interaction and structural interaction are included in the solution has not been considered. In this dissertation the response of two coupled finite plates set in two alternative configurations is considered. The plates are simply supported on two edges, with arbitrary boundary conditions on the remaining two edges. The solutions obtained for the response of the plates include both the structural interaction at the common junction and the acoustic interaction due to the scattered pressure from each of the two plates. The results are presented in terms of the vibrational power flow into and out of each plate component. The solution is based on a formulation developed in the wavenumber domain combined with the Mobility Power Flow method. Using this approach, different substructural elements coupled under different boundary conditions to form a complex global structure can be considered. The detailed spatial and temporal scales of the structure response are not lost when using this method. In obtaining the solution for the scattering from the fluid-loaded plates, a modal decomposition in the direction normal to the simply supported edge is used. A spatial Fourier-transform decomposition is used in the other direction. Due to the finiteness of the plate, eight unknowns parameters are obtained in the transformed result. The solution for these eight unknown parameters is obtained from the boundary conditions and the condition that the response must remain finite. Two analytical approaches are used to solve the final plate integral equation. The first approach consists of an approximation method which obtains a solution based on the solution of the corresponding infinite plate problem. The second approach is a more accurate solution based on the Projection Method for the solution of integral equations. Both of the approaches used in the solution provide accurate predictions at high frequencies. At low frequencies especially for low structural damping or for heavy fluid loading, only the Projection Method gives reliable results. This is attributed to the fact that at low frequencies, the influence of the edges of the plates on the scattering is significant. The overall results obtained from this analysis indicate that the fluid loading and the plate characteristics have a significant influence on the acoustic scattering properties, especially in the case of heavy fluid loading. The application of the method to coupled fluid-loaded plates indicates that the junction enhances the scattering properties. The acoustical interaction between the coupled plates increases the contribution to scattering from subsonic wavenumber components. In the absence of the interaction, only supersonic wavenumbers contribute to the scattering. Inclusion of acousticlal interaction requires both supersonic and subsonic components. The significance of the contribution from the subsonic wavenumber components is dependent on the type of the fluid loading.
Show less - Date Issued
- 1993
- PURL
- http://purl.flvc.org/fcla/dt/12341
- Subject Headings
- Finite element method, Plates (Engineering), Acoustic emission, Sound--Transmission
- 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.
Show less - 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
- Estimation of cross range dimensions from a single beam forward look SONAR.
- Creator
- Park, Joseph C., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A computer algorithm is developed to provide real-time cross range spatial quantization for a single beam forward look SONAR similar in operation to a typical sidescan SONAR. This involves the computer simulation of return time signals generated by scanning a surface profile. The time signals are normalized with respect to the scanning altitude to simulate the application of a time varying gain, and then are used as input to the surface estimation algorithm. The algorithm requires two time...
Show moreA computer algorithm is developed to provide real-time cross range spatial quantization for a single beam forward look SONAR similar in operation to a typical sidescan SONAR. This involves the computer simulation of return time signals generated by scanning a surface profile. The time signals are normalized with respect to the scanning altitude to simulate the application of a time varying gain, and then are used as input to the surface estimation algorithm. The algorithm requires two time signals acquired from adjacent scanning positions and solves a stereoscopic geometry in arriving at the surface estimate. Final estimates have an error of less than 1% in target height determination within a set range of operation.
Show less - Date Issued
- 1989
- PURL
- http://purl.flvc.org/fcla/dt/14501
- Subject Headings
- Sonar--Computer simulation, Signal processing--Computer simulation, Underwater acoustics--Computer simulation
- Format
- Document (PDF)
- Title
- THE APPLICATION OF THE ENERGY ACCOUNTANCY EQUATION IN THE INVESTIGATION OF ENERGY TRANSFER IN A THIN WALLED SHELL STRUCTURE.
- Creator
- SCHAPLEY, RAMON FRANK, II., Florida Atlantic University, Dunn, Stanley E., Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The Energy Accountancy method is used to describe the response of a system by accounting for the various energy components in a system, that is components describing the input energy, the energy dissipated, and the energy transfered by the system. These components are functions of quantities that can be determined either through measurement or finite element analysis of the system. This concept is used in this study to determine the response of a small diameter pipe containing two different...
Show moreThe Energy Accountancy method is used to describe the response of a system by accounting for the various energy components in a system, that is components describing the input energy, the energy dissipated, and the energy transfered by the system. These components are functions of quantities that can be determined either through measurement or finite element analysis of the system. This concept is used in this study to determine the response of a small diameter pipe containing two different fluids, air and water. The results of this study have shown that the Snergy Accountancy method can be used to describe the response of a thin walled shell structure with good results. It has also been shown in this study that in small diameter pipes the fluid contained by the system can be considered to act as a reactive medium in the response of the structure.
Show less - Date Issued
- 1985
- PURL
- http://purl.flvc.org/fcla/dt/14277
- Subject Headings
- Force and energy--Analysis, Force and energy--Measurement
- Format
- Document (PDF)
- Title
- The measurement of structural power flow in thin plate structures.
- Creator
- Padiyar, Satish., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
An analytical and experimental investigation of the flow of vibrational power in a thin, L-shaped, finite plate structure subjected to mechanical and acoustic excitation is presented. In the analytical approach, mobility functions are used to determine the structural intensity vectors at various locations on the plate structure. Simulation results of intensity vectors estimated using three different measurement schemes are compared. The experimentally measured intensity vectors, for the case...
Show moreAn analytical and experimental investigation of the flow of vibrational power in a thin, L-shaped, finite plate structure subjected to mechanical and acoustic excitation is presented. In the analytical approach, mobility functions are used to determine the structural intensity vectors at various locations on the plate structure. Simulation results of intensity vectors estimated using three different measurement schemes are compared. The experimentally measured intensity vectors, for the case of mechanical excitation, using a four accelerometer array, are presented. They are found to match well with the results from the corresponding simulation. Similar results are obtained for the case of acoustic excitation of the L-shaped plate. The general pattern of the structural intensity vectors is found to be in agreement with the expected results.
Show less - Date Issued
- 1990
- PURL
- http://purl.flvc.org/fcla/dt/14678
- Subject Headings
- Plates (Engineering)--Vibration
- Format
- Document (PDF)
- Title
- Structural intensity measurements in thick structures.
- Creator
- Vallory, Joelle., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Structural intensity is propagated through a thick structure by both in-plane and out-of-plane (transverse) waves. These waves propagate at different phase speeds and therefore it is important to distinguish the components of the structural intensity associated with each wave type. To show the presence of these different wave components, experimental results are performed on a thick beam. Using a frequency-wavenumber analysis, the different waves and contributions to the structural intensity...
Show moreStructural intensity is propagated through a thick structure by both in-plane and out-of-plane (transverse) waves. These waves propagate at different phase speeds and therefore it is important to distinguish the components of the structural intensity associated with each wave type. To show the presence of these different wave components, experimental results are performed on a thick beam. Using a frequency-wavenumber analysis, the different waves and contributions to the structural intensity are identified. The significance of the contributions to the structural intensity are a function of both frequency and thickness of the structure. Using simulated measurements on a thick L-shaped plate, the relative importance between the in-plane and out-of-plane contributions to structural intensity as a function of frequency and thickness is demonstrated. It is shown that in-plane wave contributions increase in importance as frequency or thickness increases.
Show less - Date Issued
- 1991
- PURL
- http://purl.flvc.org/fcla/dt/14697
- Subject Headings
- Structural dynamics, Noise, Vibration
- Format
- Document (PDF)