| Popis: |
Turbulence is ubiquitous in the topmost skin of the ocean, where it interacts with surface waves. Rapid distortion theory predicts that wave motion will increase turbulent energy, leading to a dissipation of waves [1]. Waves are believed to contribute significantly to the turbulence in the ocean mixed layer, yet field measurements are unable to validate or distinguish between models and theories [2].In this work we study the modification of turbulence by surface waves using experimental measurements of turbulent flows in the presence of waves, in a laboratory set-up acting as a small-scale model of the water side of the ocean surface layer. Turbulent Langmuir numbers comparable to those in the ocean are achieved, ensuring scalability. Particle image velocimetry (PIV) measurements were performed in a large water channel wherein mechanically generated waves may propagate on a current. An active grid at the inlet allowed the turbulence intensity and mean flow to be tailored independently. The flow field was measured in the streamwise-vertical plane for various flow cases and waves of varying steepness and frequency. The turbulence characteristics are compared to cases without waves to study the impact of the waves on the turbulence and the results are discussed considering predictions from rapid distortion theory. [1] Teixeira M. and S. Belcher 2002 “On the distortion of turbulence by a progressive surface wave” Journal of Fluid Mechanics 458 229-267.[2] D’Asaro E.A. 2014 “Turbulence in the upper-ocean mixed layer” Annual Reivew of Marine Sciences 6 101-115. |
