Internal Solitary Wave Generation Using A Jet-Array Wavemaker

TL;DR

This study experimentally generates and analyzes internal solitary waves using a jet-array wavemaker, comparing results with theoretical predictions and observing stability limits related to flow instabilities.

Contribution

It introduces a novel jet-array wavemaker method for generating internal solitary waves and systematically compares experimental data with extended Korteweg-de Vries theory.

Findings

Small- and intermediate-amplitude waves match eKdV predictions with errors below 10%.

Large waves show profile distortions possibly due to Kelvin-Helmholtz instabilities.

Wave generation efficiency depends on the local Richardson number at the inlet.

Abstract

This paper evaluates the experimental generation of internal solitary waves (ISWs) in a miscible two-layer system with a free surface using a jet-array wavemaker (JAW). Unlike traditional gate-release experiments, the JAW system generates ISWs by forcing a prescribed vertical distribution of mass flux. Experiments examine three different layer-depth ratios, with ISW amplitudes up to the maximum allowed by the extended Korteweg-de Vries (eKdV) solution. Phase speeds and wave profiles are captured via planar laser-induced fluorescence and the velocity field is measured synchronously using particle imaging velocimetry. Measured properties are directly compared with the eKdV predictions. As expected, small- and intermediate-amplitude waves match well with the corresponding eKdV solutions, with errors in amplitude and phase speed below 10%. For large waves with amplitudes approaching the maximum allowed by the eKdV solution, the phase speed and the velocity profiles resemble the eKdV solution while the wave profiles are distorted following the trough. This can potentially be attributed to Kelvin-Helmholtz instabilities forming at the pycnocline. Larger errors are generally observed when the local Richardson number at the JAW inlet exceeds the threshold for instability.