Wavemaker theories for acoustic–gravity waves over a finite depth

Abstract

Acoustic-gravity waves (hereafter AGWs) in ocean have received much interest recently, mainly with respect to early detection of tsunamis as they travel at near the speed of sound in water which makes them ideal candidates for early detection of tsunamis. While the generation mechanisms of AGWs have been studied from the perspective of vertical oscillations of seafloor and triad wave-wave interaction, in the current study we are interested in their generation by wave-structure interaction with possible implication to the energy sector. Here, we develop two wavemaker theories to analyze different wave modes generated by impermeable (the classic Havelock's theory) and porous (porous wavemaker theory) plates in weakly compressible fluids. Slight modification has been made to the porous theory so that, unlike the previous theory, the new solution depends on the geometry of the plate. The expressions for three different types of plates (piston, flap, delta-function) are introduced. Analytical solutions are also derived for the potential amplitude of the gravity, acoustic-gravity, evanescent waves, as well as the surface elevation, velocity distribution, and pressure for AGWs. Both theories reduce to previous results for incompressible flow when the compressibility is neglected. We also show numerical examples for AGWs generated in a wave flume as well as in deep ocean. Our current study sets the theoretical background towards remote sensing by AGWs, for optimized deep ocean wave-power harnessing, among others.

Surface Wave Modeling in Coastal Waters

“…Tsunami waves, in spite of its non-periodic wave form, appear to be much longer with an effective duration of 15 minutes to 1 hour; and can be induced by earthquakes or landslides in the ocean [8]. There are other types of coastal wave motion, e.g., boat wakes induced by ship motions [9,10], acoustic-gravity waves [11], storm surges due to hurricanes, capillary waves associated with surface tension, continental coastal shelfwaves produced by earth Coriolis force, (for details see [12]). In this review, we confine ourselves to surface waves in the near shore.…”