Papers by Charles Griffice
also distributed. The problem addressed by this code is that of a sonic boom passing over a wavy ... more also distributed. The problem addressed by this code is that of a sonic boom passing over a wavy ocean surface. The pressure wave transmitted through the wavy interface is the primary output of this code. The theory upon which this code is based is presented in a USC Report authored by H. K. Cheng and C. J. Lee. The purpose of the current report is to document the code by explaining the calculations performed therein, and placing the numerical routines in correspondence with the equations which appear in the USC Report. Code results from a sample input set are also presented in order to provide a benchmark for future users and against which to compare possible future releases of this code by Cheng and Lee. The emphasis of this report is on code documentation. No assessment nor interpretation of the theory is offered. Although the Cheng and Lee code is not currently in standard use for predicting sonic boom transmission into the ocean, this document may hasten its adoption as a standard tool for this purpose.
Evaluation of patient radiation doses and risks from x-ray transmission computer tomography scanning [microform] /
Typescript. Thesis (M.S.)--University of Missouri-Columbia. Includes bibliographical references (... more Typescript. Thesis (M.S.)--University of Missouri-Columbia. Includes bibliographical references (leaves 111-114). Microfilm. [Columbia, Mo.] : University of Missouri-Columbia,
Sonic Boom and Underwater Sound Pressure Induced by Low-Altitude Ramjet Cruise Missiles
44th AIAA Aerospace Sciences Meeting and Exhibit, 2006
Underwater Overpressure from Hypervelocity Sonic Booms
14th AIAA/CEAS Aeroacoustics Conference (29th AIAA Aeroacoustics Conference), 2008
The propagation of underwater overpressure induced by hypervelocity sonic booms of speed greater ... more The propagation of underwater overpressure induced by hypervelocity sonic booms of speed greater than Mach number (M) 4.5 has been analyzed using semi-similar variables. Unlike the solutions for that induced by a sonic boom of M less than 4.5, the present solution shows that the overpressure amplitude does not diminish in the water and that the waveform of the sonic boom is preserved as it propagates into the water. This result is in agreement with the experimental data obtained by Malcom and Intrieri in a NASA/Ames ballistic range experiment published in 1973.
: This Environmental Assessment (EA) documents the potential environmental impacts of conducting ... more : This Environmental Assessment (EA) documents the potential environmental impacts of conducting beddown, deployment, processing, pre-launch preparations, launch, operations, and disposal for up to six Advanced Extremely High Frequency (AEHF) satellites at Cape Canaveral Air Force Station in Florida. The satellites would be launched from an existing Space Launch Complex using Evolved Expendable Launch Vehicles, which were analyzed in prior environmental documents separate from this EA.
Effect of Rarefied Atmosphere on Blunt Body Stagnation Region Flow and Heat Transfer
AIAA SPACE 2016, 2016
Numerical Evaluation of the Ultrasonic Pressure in the Fields of Continuous-Wave and Pulsed Transducers
ABSTRACT The acoustic pressure fields found in the field of an ultrasonic transducer were investi... more ABSTRACT The acoustic pressure fields found in the field of an ultrasonic transducer were investigated numerically and resulted in a procedure to calculate the ultrasonic pressure magnitude and phase for a continuous-wave or pulsed transducer system. Perturbations to this basic numerical ultrasonic field calculation include focused as well as nonfocused transducers, nonuniform as well as uniform amplitude weighting distributions for the transducer and multiple as well as single ultrasonic field media. The computer algorithms developed for these ultrasonic field analysis calculations are thoroughly verified using existing acoustic field theory. The information provided by these ultrasonic field analysis codes can now be confidently applied to improving present ultrasonic systems and can be used in the improved design of future ultrasonic systems.
The public reporting burden for this collection of information is estimated to average 1 hour per... more The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information.
Numerical Evaluation of the Ultrasonic Pressure in the Fields of Continuous-Wave and Pulsed Transducers
ABSTRACT The acoustic pressure fields found in the field of an ultrasonic transducer were investi... more ABSTRACT The acoustic pressure fields found in the field of an ultrasonic transducer were investigated numerically and resulted in a procedure to calculate the ultrasonic pressure magnitude and phase for a continuous-wave or pulsed transducer system. Perturbations to this basic numerical ultrasonic field calculation include focused as well as nonfocused transducers, nonuniform as well as uniform amplitude weighting distributions for the transducer and multiple as well as single ultrasonic field media. The computer algorithms developed for these ultrasonic field analysis calculations are thoroughly verified using existing acoustic field theory. The information provided by these ultrasonic field analysis codes can now be confidently applied to improving present ultrasonic systems and can be used in the improved design of future ultrasonic systems.
Sonic-boom noise under a wavy air-water interface
Journal of The Acoustical Society of America, 2008
ABSTRACT Recent investigations of the underwater sound field produced by sonic booms show that th... more ABSTRACT Recent investigations of the underwater sound field produced by sonic booms show that the latter's interaction with surface waves can strongly alter the sound level, frequency range, and signal waveform reaching the deeper part of the ocean. Unlike conclusions from studies based on the flat-ocean model of Sawyers [1] which indicate little effects at depth beyond one signature length, the interaction of sonic-boom waves with a surface-wave train can generate nonevanescent, downward propagating waves which, owing to their lower spatial-attenuation rate, overwhelm the otherwise primary (flat-ocean) wave field. Theoretical results [2] substantiate and elucidate the significant differences between flat and wavy surfaces in waveform characteristics and their audibility in deep, and moderately deep water. Here we report on an extensive series of laboratory experiments performed specifically to validate this theoretical model and to ascertain the distinct differences in wave-field characteristics between a wavy and flat interface. The experimental measurements confirm the theoretical findings, showing the predicted differences between the sound fields measured under wavy and flat air-water interfaces stimulated by a passing sonic boom. [1] Sawyers, K. H. J. Acoust. Soc. Am., 44(2), 523 - 524, (1968) [2] Cheng, H. K. and Lee, C. J., J. Fluid Mech. 514, 281-312 (2004).
Journal of Nondestructive Evaluation, 1981
A simple, flexible, accurate, and comprehensive numerical method is presented for theoretically a... more A simple, flexible, accurate, and comprehensive numerical method is presented for theoretically analyzing the diffraction field of a continuous wave transducer of arbitrary size, shape, and frequency. Using the extensively studied circular transducer for comparison, numerical results are shown for an unfocused transducer with uniform velocity excitation as well as for a focused transducer with Gaussian velocity excitation. Data concerning the execution time, program size, and convergence of the method are also presented for its implementation as a design tool on a minicomputer system.
Simulation and exploitation of proposed commercial multispectral remote sensing systems
With the increasing number of planned and operational high resolution commercial remote sensing s... more With the increasing number of planned and operational high resolution commercial remote sensing satellites, there is a need to study the utility of the image exploitation products that will be generated by these systems. This has been done in a two-step process of simulating a multispectral testcase image data cube and then applying standard exploitation tools to different bands of the simulated testcase. The first step in evaluating image utility was to use a new image simulation tool to generate a commercial testcase for comparison with several other commercial sensors and their associated spectral specifications. For this study, the simulation capability that was developed used hyperspectral image cube as input to generate a testcase multispectral simulated image cube that was representative of current and planned commercial remote sensing systems. The second step in the utility evaluation was to apply standard multispectral exploitation tools to the testcase imagery that was generated in the first step. This exploitation study used different Landsat Thematic Mapper spectral band combinations with a spatial resolution that was fixed for the testcase that was simulated. The exploitation products created from this testcase were used to show the utility comparison of remote sensing systems with the following band combinations-Landsat 1-5, 7; Landsat 1-4; Landsat 1-3; and Landsat 2-4-at the spatial resolution of the testcase simulation
Recent progress on the theoretical modeling of underwater acoustics induced by sonic booms
Journal of The Acoustical Society of America, 2008
Recent progress on the theoretical modeling of underwater acoustics induced by sonic booms
Journal of The Acoustical Society of America, 2008
Sonic-boom noise under a wavy air-water interface
Journal of The Acoustical Society of America, 2008
ABSTRACT Recent investigations of the underwater sound field produced by sonic booms show that th... more ABSTRACT Recent investigations of the underwater sound field produced by sonic booms show that the latter's interaction with surface waves can strongly alter the sound level, frequency range, and signal waveform reaching the deeper part of the ocean. Unlike conclusions from studies based on the flat-ocean model of Sawyers [1] which indicate little effects at depth beyond one signature length, the interaction of sonic-boom waves with a surface-wave train can generate nonevanescent, downward propagating waves which, owing to their lower spatial-attenuation rate, overwhelm the otherwise primary (flat-ocean) wave field. Theoretical results [2] substantiate and elucidate the significant differences between flat and wavy surfaces in waveform characteristics and their audibility in deep, and moderately deep water. Here we report on an extensive series of laboratory experiments performed specifically to validate this theoretical model and to ascertain the distinct differences in wave-field characteristics between a wavy and flat interface. The experimental measurements confirm the theoretical findings, showing the predicted differences between the sound fields measured under wavy and flat air-water interfaces stimulated by a passing sonic boom. [1] Sawyers, K. H. J. Acoust. Soc. Am., 44(2), 523 - 524, (1968) [2] Cheng, H. K. and Lee, C. J., J. Fluid Mech. 514, 281-312 (2004).
Journal of Nondestructive Evaluation, 1981
A simple, flexible, accurate, and comprehensive numerical method is presented for theoretically a... more A simple, flexible, accurate, and comprehensive numerical method is presented for theoretically analyzing the diffraction field of a continuous wave transducer of arbitrary size, shape, and frequency. Using the extensively studied circular transducer for comparison, numerical results are shown for an unfocused transducer with uniform velocity excitation as well as for a focused transducer with Gaussian velocity excitation. Data concerning the execution time, program size, and convergence of the method are also presented for its implementation as a design tool on a minicomputer system.
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Papers by Charles Griffice