Buried target detection using time reversal in inhomogeneous sediment
Pierson, D. M., and Drake, T.G., 2002, Buried target detection using time reversal in inhomogeneous sediment: 143rd Meeting of the Acoustical Society of America, Pittsburgh, Pennsylvania, 3-7 June 2002
Time reversal has been demonstrated to refocus acoustic waves in
homogeneous media with multiple scatters. It has also been shown to work through
a liquid--solid interface when both media are homogeneous. We will show that
time reversal can also work to detect objects in inhomogeneous solids. By
modeling a single transducer in water located 10 m above the water--solid
interface we will show the location of the object can be isolated using an
iterative time reversal method. Simulations are performed with the solid medium
having a mean density of quartz sand varying spatially with horizontal
correlation length 0.5 m and vertical correlation length 0.02 m. A sphere is
buried in the sand having a density of iron in one test and a density closer to
quartz sand in another. The sphere diameter was changed in each simulation
ranging from 9 cm to 19 cm. The initial pulses were sinusoidal with frequencies
of 10 kHz, 100 kHz, and 500 kHz. Results show improved localization of the
sphere. It will also be shown that the iterative time reversal method goes to a
response that is independent of initial pulse frequency as predicted by previous
theories.
Supported by the Office of Naval Research
Comments:Dave Pierson