Near Field Scattering Through and From 2-D Fluid-Fluid Rough Interface

摘要

General analytical expressions for the time dependent field intensity scatteredfrom or through (penetrating) a 2-D fluid-fluid rough surface due to a narrowband incident plane wave, and a narrowband point source area derived and expressed in terms of the bistatic scattering cross section per unit area of the rough surface. Even though the cross section is defined as a far field entity, this near field result is general and exact for the special case of a continuous wave (CW) source and incident plane wave, Dispersion of a pulse is a function of medium parameters, the incident and scattered directions, as well the bandwidth and center frequency of the source signal. First order perturbation calculations for the case of a Gaussian pulse illustrate intensity pulse dispersion effects due to forward scattering into a lossy sediment. For the case of incidence below the critical grazing angle, first order perturbation computations also show that the field scattered through a rough surface can be much greater than the zero order field transmitted below the corresponding flat surface depending on loss, and receiver depth to source wavelength ratio. These computations for the incoherent intensity penetrating the rough interface are compared to the flat surface result, for both plane wave and point sources.