ASA 127th Meeting M.I.T. 1994 June 6-10

5pUW14. Time domain visualizations of the acoustic scattering from two-dimensional (2-D) rough surfaces.

Richard S. Keiffer

NRL Code 7181, Stennis Space Center, MS 39529-6000

Jorge C. Novarini

Planning Systems, Inc., Slidell, LA 70458

Guy V. Norton

NRL, Stennis Space Center, MS 39529-6000

The impulse response of a 2-D rough surface to a point source is calculated via the wedge assemblage (WA) method. Periodic, doubly periodic, and randomly rough 2-D surfaces having both Dirichlet and Neumann boundary conditions are considered. The WA method is used to generate time-evolving visualizations of the scattering process by mapping onto all parts of the scattering surface a color that represents a surface elements contribution to the instantaneous scattered field as measured at the receiver. Successive snapshots of this color-coded spatial mapping of the individual impulse responses are generated and displayed sequentially to form a movie. In addition to the movie, a new tool for the analysis of the scattering process is introduced. This new tool uses the fact that, for the particular surface discretization employed, only four distinct types (directions) of wedge can occur. Because the contributions of the different wedge types to the overall impulse response are readily separated via the WA model, one can study the role of surface curvature in different directions for various scattering geometries. In particular, this unique capability is exploited to gain further insight into the role of out-of-plane scatterers for various geometries. [Work supported by ONR.]