Refraction of Wave Packets by Currents.
FLORIDA INST OF TECH MELBOURNE DEPT OF OCEANOGRAPHY AND OCEAN ENGINEERING
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The refraction of wave packets by ocean, surface currents is investigated using a refraction method based on Snells law with geometric group velocity. This refraction method requires curvature equations for the directions of the wavelets and wave packets, and an advection equation for the direction of the ray. Three equations are necessary, since after refraction the wavelet and packet directions differ, and a ray is not generally orthogonal to the wave fronts in a current. These equations are derived and applied to idealized current models. The current models are patterned after the Gulf Stream and the Circumpolar Current. Both parallel and curved current contours are considered. From this study, it was found that wave packets can be totally reflected or deflected from their original path by a current with the short period waves being affected to a greater extent than the long period waves. The curvature of a ray was found to have the same sign as the vorticity of the current and to increase as the vorticity increased. Rays were found to bend away from the current and to increase normal in a following current and toward the current normal in an opposing current becoming perpendicular to the current speed contours if sufficient refraction occurred. It was found that there was very good agreement in the results of all the methods for small initial angles and small current speeds. However, differences between the results obtained by the different methods increased greatly for mid-range angles 30-75 and for large current speeds.
- Physical and Dynamic Oceanography