ASA 126th Meeting Denver 1993 October 4-8

5aSA6. The influence of internal structures on bistatic scatter from finite cylindrical shells near axial incidence.

Matthew Conti Ira Dyer

Dept. of Ocean Eng., MIT, Cambridge, MA 02139

Previous results have examined the scatter for an empty shell at axial incidence illustrating the primary role of the endcap. Building on this, important differences in the bistatic scatter due to the presence of internal structures are presented. In addition, differences due to source incidence away from axial are investigated. Discussion is based upon bistatic measurements on an empty shell with endcaps, a duplicate shell with internal ring stiffeners and a duplicate ring stiffened shell with resiliently mounted wave-bearing internal structures. Integrated target strengths shown as a function of observation angle reveal spatial regions where the internal structures cause significant change. Of particular interest is enhancement of target strength near backscatter. In conjunction with conventional beamforming techniques, these analyses reveal the distribution of energy along the shell length. This distribution is modified by rotation of incidence away from axial. Relative decay rates and frequency-dependent effects are also discussed. The bistatic measurements were conducted over a frequency range of 2.5