Papers by George Benthien
University Microfilms eBooks, 1970
APhy, Sep 1, 1992
... Page 3. B8m2 ]ýlFI EF lIF iiI CA LCI LAlI RN AN II Dl';L AN' OF lDlSl'IALSIOiN... more ... Page 3. B8m2 ]ýlFI EF lIF iiI CA LCI LAlI RN AN II Dl';L AN' OF lDlSl'IALSIOiN' 1A \FS Ffll? A ill[ Yl INIMlICAL. ... THE EFFICIENT CALCULATION AND DISPLAY OF DISPERSION CURVES FOR A THIN CYLINDRICAL SHELL IMMERSED IN A FLUID Harry A. SCHENCK ...
Journal of the Acoustical Society of America, Nov 1, 1995
In this paper some of the analytic and numerical techniques that have been applied to the array i... more In this paper some of the analytic and numerical techniques that have been applied to the array interaction problem will be reviewed. For problems where high accuracy is not required, many modelers have used an approximation for the mutual interactions that has come to be known as the Pritchard approximation. In this paper a new approximation technique will be presented which appears to be more accurate than the Pritchard approximation for the cases that have been examined. Results will be shown that compare this new approximation scheme both with the Pritchard approximation and with more accurate numerical computations. [Work supported by SPAWAR PMW-182.]
Journal of the Acoustical Society of America, Nov 1, 1985
Journal of the Acoustical Society of America, Apr 1, 1974
Tappert and Hardin have developed a technique for computing underwater acoustic propagation loss ... more Tappert and Hardin have developed a technique for computing underwater acoustic propagation loss fields which is known as the parabolic equation method. This is a numerical matching method which leads to a relatively fast computation algorithm and permits sound speed variation in multiple dimensions. For sound speed variation in depth only, we have investigated accuracy, ease of use, and computer time requirements of this method. Reliable natural mode or ray theory computations were used as starting values at a given range and for accuracy checks at longer ranges. The parabolic equation method was found to be stable and accurate for acoustic ducts formed by refraction or surface reflections. Bottom reflections presented many problems and mode results could not be duplicated in general. The method was comparatively easy to use once starting values were available, but no way was found to determine optimum step size without some trial and error. Computer time requirements were always as large as those for mode theory and were often much greater. The primary value of the parabolic method then lies in its application to two-dimensional sound speed profiles where closed-form solutions are difficult.
Springer eBooks, 1991
Numerical methods are frequently used to calculate array interactions. This paper summarizes some... more Numerical methods are frequently used to calculate array interactions. This paper summarizes some of the advantages that numerical methods have over the more classical analytical methods. Many of the numerical methods for calculating array interactions are based on the Helmholtz integral relations. This paper describes one such method and shows how it can be coupled to a finite element model for the individual transducers in the array. A very useful approximation for the array interaction matrices is also presented. To illustrate the validity of this numerical model, a comparison between numerical and experimental results for a three element flextensional array is also presented.
To predict the performance of transducers operating in an array it is necessary to consider the a... more To predict the performance of transducers operating in an array it is necessary to consider the acoustic interaction between transducers. This analysis usually involves solving a system of equations involving certain transducer impedances as well as mutual radiation impedances between transducer elements. This problem can be simplified by taking into account any geometric symmetries that might be involved. Unlike finite element problems where geometric symmetry can be enforced through boundary conditions, it is necessary in these problems to consider the structure of the radiation impedance matrix induced by the geometric symmetries. In this paper I will show how computation time can be reduced considerably by taking advantage of the special symmetry structure of these matrices.
Mathematics Magazine, Jun 1, 2008
Journal of the Acoustical Society of America, Nov 1, 1988
Journal of the Acoustical Society of America, Nov 1, 1985
Most analyses of mutual radiation coupling to-date have assumed that the velocity distribution on... more Most analyses of mutual radiation coupling to-date have assumed that the velocity distribution on each piston is fixed and known. In some problems, however, the velocity distribution on each radiator is made up of several modes and the modes interact acoustically as well as mechanically. For example, the velocity distribution on each piston might consist of a rigid body mode and one or more flexural modes. In this paper a general framework will be presented for the modal acoustic interaction problem, and several numerical techniques for its solution will be examined.
The lack of reproducibility and uniformity of piezoelectric ceramics is a problem that has plague... more The lack of reproducibility and uniformity of piezoelectric ceramics is a problem that has plagued the Navy for over 30 years. As a result, and the need to specify ceramic for competitive procurements, the Navy has developed specifications that accommodate the variability of the ceramic and assure the transducer will meet performance requirements, be electroacoustically interchangeable, and be intermixable with existing units. A Simplified Guidance Xodel ( S G M ) has been developed that provides insight into the relationship between ceramic parameters and transducer design and performance. Experimental data are presented that validate the SGPl. New methods are presented to extract the piezoelectric material parameters from geometry dependent 33 mode ceramic rings. A dynamic tester has been developed to certify the performance of a composite ceramic stack. applications. Figure 1 shows a cut-away of a typical transducer element of interest. To achieve the solution, complicated computerized predictive models had to be augmented by what has been called a Simplified Guidance Model ( S G M ) in order to deduce the kernel of the solution. The heart or kernel of the solution has been referred to as DAS-7. It is a design adjustment method that allows one to match the electroacoustic performance of a proposed transducer to that of a baseline, and assure that the new transducer will duplicate the baseline and be electroacoustically interchangeable and intermixable. A derivation and discussion of the SGM and the relationship of the parameters in DAS-7 is presented in reference [ I ] . Simply stated, DAS-7 requires the rnanuEacturer to match the piezoelectric constant, d33, and free capacitance, CT, of the ceramic, t o that of the baseline. If, however, the manufacturer is unable to match both quantities, then he shall match the d33. The lack of reproducibility and uniformity of piezoelectric ceramics is a problem that has plagued the Navy since the introduction of ceramic sensors into fleet transducers over 30 years azo. After the d33 match has been achieved, then a As a result of this situation and the need to be one-time area adjustment, within prescribed limits, able to specify the piezoelectric ceramic €or a is allowed to either increase o r decrease CT to build-to-print Fabrication Specification Package match the baseline. Once the d,,, and CT, match ( F S P ) , a solution to the problem was developed. The Sonar Transducer Reliability Improvement Program (STRIP), with some assistance from the Transduction Sciences Program, has developed a complete, practical solution to the problem of reproducibility for a certain class of 33 mode transducer <_I has been achieved, the final criterion is that the compliance of the ceramic be such that when a stack is fabricated and placed in a primary subassembly, there must exist an acceptable fiberglass tuning ring to tune the assembly to the required resonznce frequency. Cut-away of Typical 33 Xode Transducer
Journal of the Acoustical Society of America, May 1, 2008
Journal of the Acoustical Society of America, May 1, 1981
SONAR equation. It is shown that in most cases the backscattering strength becomes range-independ... more SONAR equation. It is shown that in most cases the backscattering strength becomes range-independent beyond short distances. The backscattering strength therefore appears to be a useful parameterisation of regional and seasonal reverberation and may possibly be applied to determine the range dependence of transmission loss. 3:00 QQS. Scattering coefficients and Doppler spectra of specularly scatterS! sound from the sea surface. W. I. Roderick and W. G.
A technique is described for solving steady state coupled structure-acoustics problems that has b... more A technique is described for solving steady state coupled structure-acoustics problems that has been implemented by the transducer modeling group at the NOSC. This technique is applicable to both structural radiation problems and structural scattering problems. The structural portion of the problem is modeled using a standard finite element program. The particular program used at NOSC is MARTSAM, but virtually any general finite element code could be used. The acoustical portion of the problem is modeled using the Combined Helmholtz Integral Equation Formulation (CHIEF). This technique was implemented at NOSC in a computer program that is also called CHIEF. A technique is described for solving steady coupled structure-acoustics problems.
Journal of the Acoustical Society of America, May 1, 1981
livered to the listeners via a circumaural earphone at the most comfortable levels. Ten sensorine... more livered to the listeners via a circumaural earphone at the most comfortable levels. Ten sensorineural S's were tested. The mean scores without reverberation, without and with compression were 82.9% and 84.3%, respectively. The reverberation lowered these S97
Archive for Rational Mechanics and Analysis, 1972
The author would like to thank Don Barach and David Gillette for converting the techniques descri... more The author would like to thank Don Barach and David Gillette for converting the techniques described in this report into efficient computer programs and for obtaining the included numerical results. The author would also like to thank H. A. Schenck for his review of this paper and for many useful discussions and suggestions.
Computational Fluid and Solid Mechanics, 2001
The Journal of the Acoustical Society of America, 1974
Tappert and Hardin have developed a technique for computing underwater acoustic propagation loss ... more Tappert and Hardin have developed a technique for computing underwater acoustic propagation loss fields which is known as the parabolic equation method. This is a numerical matching method which leads to a relatively fast computation algorithm and permits sound speed variation in multiple dimensions. For sound speed variation in depth only, we have investigated accuracy, ease of use, and computer time requirements of this method. Reliable natural mode or ray theory computations were used as starting values at a given range and for accuracy checks at longer ranges. The parabolic equation method was found to be stable and accurate for acoustic ducts formed by refraction or surface reflections. Bottom reflections presented many problems and mode results could not be duplicated in general. The method was comparatively easy to use once starting values were available, but no way was found to determine optimum step size without some trial and error. Computer time requirements were always as large as those for mo...
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Papers by George Benthien