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