Measurements of unsteady turbulence over wind-driven surface water waves using time-resolved PIV in an atmospheric boundary layer wind-wave tunnel

Wind generated surface waves mediate the transfer of momentum, energy, and scalars across the air-water interface. Models of the atmospheric boundary layer (ABL) and the surface mixing layers of lakes and oceans rely on parameterizations for surface fluxes which are typically based on rough-wall boundary layer theory. Waves are often out of equilibrium with the ABL flow and energy is commonly transferred back to the ABL. There is limited information about the details of the coupled boundary layers which are needed to better understand the role of turbulence in these interactions. We employ time-resolved PIV to measure the detailed structure of air and water boundary layer turbulence under varying wind and wave conditions in the new IIHR Boundary-Layer Wind-Wave Tunnel. The facility combines a 30-m long recirculating water channel with an open-return boundary layer wind tunnel. A thick turbulent boundary layer is developed in the 1 m high air channel, over the water surface, allowing for the study of large-scale boundary layer turbulence interacting with a wind-driven wave field. The first time-resolved turbulence measurements are presented for varying wind speeds over breaking waves and details of the time-evolution of boundary layer fluxes are reported.