Observation of resonant interactions among surface gravity waves

TL;DR

This study experimentally investigates resonant interactions among oblique surface gravity waves, confirming theoretical predictions with detailed measurements and extending previous research to more general wave configurations.

Contribution

It provides the first comprehensive experimental validation of four-wave interaction theory for oblique waves crossing at an angle, including off-resonance conditions.

Findings

Resonant wave growth rates match theoretical predictions

Phase locking occurs as predicted by four-wave interaction theory

Off-resonance interactions are accurately described by the theoretical model

Abstract

We experimentally study resonant interactions of oblique surface gravity waves in a large basin. Our results strongly extend previous experimental results performed mainly for perpendicular or collinear wave trains. We generate two oblique waves crossing at an acute angle, while we control their frequency ratio, steepnesses and directions. These mother waves mutually interact and give birth to a resonant wave whose properties (growth rate, resonant response curve and phase locking) are fully characterized. All our experimental results are found in good quantitative agreement with four-wave interaction theory with no fitting parameter. Off-resonance experiments are also reported and the relevant theoretical analysis is conducted and validated.