Nonlinear focusing of ultrasonic waves by an axisymmetric diffraction grating embedded in water

Nonlinear Diffraction of Water Waves by Offshore Structures

in cylindrical polar coordinates is derived. This is followed by a review of the current knowledge on analytical theories and numerical treatments of nonlinear diffraction of water waves by offshore cylindrical structures. A brief discussion is made on water waves incident on a circular harbor with a narrow gap. Special emphasis is given to the resonance phenomenon associated with this problem....

Nonlinear refraction-diffraction of waves in shallow water

The parabolic approximation is developed to study the combined refraction/diffraction of weakly nonlinear shallow-water waves. Two methods of approach are used. In the first method Boussinesq equations are used to derive evolution equations for spectral-wave components in a slowly varying two-dimensional domain. The second method modifies the K-P equation (Kadomtsev & Petviashvili 1970) to incl...

Picosecond Holographic Grating Generation of Ultrasonic Waves

The picosecond holographic grating generation and detection of ultrasonic waves are described. Two mechanisms, a heating mechanism and a stimulated Brillouin scattering mechanism, are described. These permit the generation of tunable ultrasonic waves in the MHz to GHz range. It is demonstrated that the two mechanisms can be distinguished by the distinct time dependences of the diffraction of a ...

Diffraction of Ultrasonic Waves by Elliptical Cracks in Metals

Ultrasonic spectrum analysis is used to study the frequency and angular behavior of diffracted longitudinal waves from elliptical cracks with arbitrary orientation in diffusion bonded titanium alloy. The aspect ratio of the cracks (ratio of major to minor axis) ranged from l to 8 and the bandwidth of the input signal was such that the scattering diameter was ka > l. The experimental data are an...

On Nonlinear Water Waves in a Channel