Wavemaker theories for acoustic-gravity waves over a finite depth

TL;DR

This paper develops two wavemaker theories for acoustic-gravity waves in weakly compressible fluids, analyzing wave generation by different plates, with implications for tsunami detection, remote sensing, and wave energy harnessing.

Contribution

It introduces modified porous wavemaker theory that accounts for plate geometry and derives analytical solutions for various wave parameters in compressible fluids.

Findings

Both theories reduce to classical results in incompressible limit

Analytical expressions for wave amplitudes and surface elevation are provided

Numerical examples demonstrate wave generation in flume and deep ocean environments

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.