Eigenray sonar simulation in two-layer media
MetadataShow full item record
In this work, an eigenray finding method for simulating refractive multipath phenomena in an unbounded underwater environment is presented. To simplify the problem, the environment consists of a horizontally-homogeneous two-layer medium in which isogradient sound speed profiles are used in each layer. Eigenrays are found through an iterative Newton-Raphson method on the Snell invariant, and the travel time is found from the computed Snell invariant. A derivation for the maximum number of ray paths that need to be considered to account for all refractive multipaths is included. Given a point source/point target pair, the method will output a launch angle and travel time for the eigenray connecting the source and target. The time accuracy of the eigenray finding method is confirmed using a forward ray-trace. From the travel time of eigenrays, time series data is formed for each receive element. Refractive multipath phenomena are shown using the time series data of a target near the layer boundary. An FFT beamformer is used to beamform the simulated time series data which reproduces an image of the acoustic targets, which shows a time resolution sufficient to support the coherent addition of signals in beamforming.