Laboratory measurements of wave-induced turbulence using thermal marking velocimetry

Some theoretical considerations suggest an existence of wave-turbulence energy flux without wave breaking, but scarce empirical results struggle to establish the existence of such process. This study utilizes infrared imaging to investigate the effect of wave motion on near-surface turbulence. An active thermography technique called Thermal Marking Velocimetry (TMV) technique was used in a laboratory wave tank. TMV consisted a CO₂ 10W laser and rotating mirror to create thermal markers on the water surface, and mid-wave infrared camera to trace their motion. The results confirm the turbulence production due to wave motion. The turbulent kinetic energy was found to be a function of time, wave steepness, wave phase, and initial turbulent conditions. Additionally, turbulent motion near the surface was found to be horizontally anisotropic due to the formation of near-surface eddies, elongated in the direction of wave propagation.