Airbome Laser Bathymetry (ALB) is a technique primarily aimed at augmenting nautical chart production and bathymetric mapping capability in relatively shallow coastal waters. The potential of waterpenetrating airborne laser radar to provide cost effective characterization of underwater topography to depths as great as 50 meters, depending on water clarity, has triggered a number of research and...

Large scale laboratory experiments concerning breaking wave propagation over a fixed-bed, barred beach were performed. The primary observations of interest were video intensity time series obtained from a set of high-resolution video cameras in order to study the onset of wave breaking in shallow water and wave roller transformation in the surf zone. The approach is new in the sense that the an...

LONG-TERM GOALS Goals for this project include: 1) the characterization of ocean acoustic impulse response (OAIR) in shallow water under various environmental conditions, 2) the development of predictive and synoptic methodologies/models linking acoustic communications system (modem) performance to environmental factors. Ultimately this information can be used to develop a robust acoustic modem...

The ability to predict the sound field in shallow water envirnments depends to a large degree on having adequate knowledge of the geoacoustic properties of the bottom. The long term objectives of this research project are related to the investigation of experimental methods and inversion techniques for estimating parameters of geoacoustic models of the ocean bottom and the associated uncertaint...

The primary long-term goal is to measure and model high-frequency acoustic propagation in the presence of surface gravity waves and breaking waves to better understand the effects of surface reverberation on shallow water, underwater acoustic communications (ACOMS). Secondary long-term goals are to exploit measurements of breaking wave noise to infer bubble cloud populations at the sea surface ...

Conservation of potential vorticity in Eulerian uids re ects particle interchange symmetry in the Lagrangian uid version of the same theory. The algebra associated with this symmetry in the shallow water equations is studied here, and we give a method for truncating the degrees of freedom of the theory which preserves a maximal number of invariants associated with this algebra. The nite dimensi...

A commodity-type graphics card (GPU) is used to simulate nonlinear water waves described by a system of balance laws called the shallow-water system. To solve this hyperbolic system we use explicit high-resolution central-upwind schemes, which are particularly well suited for exploiting the parallel processing power of the GPU. In fact, simulations on the GPU are found to run 15–30 times faster...

A submarine on patrol needs to know how far it can be detected by active sonar. In order for such sonar performance calculations to be useful the target strength (TS) of the submarine must be known. Measurements done in deep water indicate that TS can vary as much as 20 dB as a function of aspect angle. This corresponds to a doubling of the detection distance in a noise limited environment, and...

Mud volcanoes are solid objects that form on the seafloor due to the emission of gas and fluidized sediment from the earth’s interior [1]. They vary widely in size, can be exposed, proud, or buried, and are of interest to the Navy as sources of active sonar clutter [2]. The long-term goal of this work is to accurately model mud volcano scattering. The final product will make predicting and simu...