Acoustic Scattering from an Aluminum Cylinder in Contact with a Sand Sediment: Measurements, Modeling, and Interpretation

摘要

Understanding acoustic scattering from objects placed on the interface between two media requires incorporation of scattering off the interface to the object as well as the reciprocal scattering process. In addition, the contact of the target with the interface may change the dynamics of the target. This class of problems is studied in the particular context of an aluminum cylinder placed on a flattened sand interface. Experimental results are presented for the monostatic scattering from this cylinder for azimuthal scattering angles from 0 to 90 degrees and frequencies from 1 to 30 kHz. Next, details seen within these experimental results are explained using physical acoustics derived insight. Subsequently, target strength results are compared to finite element calculations that incorporate the geometry and interface/target interactions at various levels of sophistication. The simplest calculation assumes that source and receiver are at infinity and uses the finite element result for the cylinder in free space along with image cylinders for approximating the target/interface interaction. Then the effect of moving the receiver to a finite distance and inclusion of a more complete Green's function for the target/interface interaction is examined. The result is a three-dimensional prediction for scattering derived using multiple two dimensional calculations.