Experimental investigation of 2D and 3D internal wave fields

Abstract

The generation of 2D and 3D internal wave fields is extensively studied via planarand stereo- Particle Image Velocimetry (PIV) flow field measurement techniques. A benchmark was provided by an experiment involving tidal flow over a 2D Gaussian ridge; this study providing a counterpart with which studies of a 3D incised Gaussian ridge could be compared with. To further benchmark the 3D wave field studies an experiment involving the canonical setup of a vertically oscillating sphere was performed and the results compared with the latest theory; the excellent agreement obtained provided confidence in the stereo-PIV method for studying fully three-dimensional internal waves. The 3D incised Gaussian ridge generates a wave field characterized by noticeable, though weak, out-of-plane forcing that evolves from a relatively strong to a weakly localized quantity as the wave field transitions from super- to subcritical, while the in-plane velocity field appears nearly identical to its 2D counterpart.