Experimental and modeling analysis of near-field scattering from complex targets
Name
302414737-MIT.pdf
Description
Full printable version
Size
15.5 MB
Format
Adobe PDF
Checksum (MD5)
d236fbc0e75b3f09449cd4e03b643464
Author(s)
Ghosh, Deep
Advisor(s)
Henrik Schmidt.
Date Issued
2008
Publisher
Massachusetts Institute of Technology
Abstract
Classification and detection of targets based on the analysis of structural resonances has been of prime interest to ocean acousticians for a long time. To further the understanding on scattering from complex targets, the EVA'06 experiment was conducted by a group of teams that included NURC, NRL and MIT, o the island of Elba in Italy. The experiment involved controlled monostatic and bistatic, near field and far field measurements of scattering from proud and half buried targets, which are representative of real world mines. This thesis focuses on the analysis of near-field bistatic data set obtained by supercritically insonifying proud composite targets and subcritically insonifying an empty spherical shell. Specifically, the arrival times of different waves known to be generated by scattering from cylindrical and spherical shells have been computed at different azimuths and vertical angles. These traces have been obtained by analyzing the experimental data and from simulations using OASES/SCATT. The arrival times, additionally, have been computed using geometry for the 'in-plane' i.e, precise forward and back scattering configurations. This enables accurate identification of different waves for these two azimuths which are then followed with the cage rotation. Also, the average intensity recorded at each receiver as a function of frequency and cage rotation is illustrated in the dome plots. Finally, in the experimental plots some unidentified arrivals have been noted, which could be the waves supported by the filler material contained inside. This work, thus, presents a comprehensive treatment of near-field scattering from complicated targets and provides a framework to do future work on deciphering the arrival times of more complicated waves from targets of arbitrary geometry.
Description
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 497-502).
Subjects
Mechanical Engineering.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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