Dear all,
We are pleased to invite you to the next WISE Webinar on the topic of Near Surface Turbulence on 23/10/2025 at 11:00 AM ET (5 PM Zurich time).
Join us via https://tudelft.zoom.us/my/wisezoominars on 23rd October at 11:00AM -12.00 PM Eastern Time!
First speaker: Daniel J Ruth, ETH Zürich
Title: Turbulence structure beneath laboratory wind-driven waves.
Abstract:
Turbulence develops in the water beneath the ocean surface due to wind-induced shear and interactions between the sub-surface flow and waves. To better understand the structure of such turbulence, particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) measurements are performed in the ETH Zurich Wind-Water-Wave Tank to characterize the flow when wind up to U10 = 16 m/s is blown over ~ 7 m fetch. The measured velocity fields are triple-decomposed into time-averaged, wave-associated, and turbulent components using multiple methods. The wave-associated fields constructed with two data-driven methods, phase-locked averaging (which bins and averages measured velocities according to the phase and amplitude of the overhead wave) and spectral coherence (which infers a linear, scale-dependent relationship between the surface elevation and sub-surface velocity), agree closely with orbital velocity fields calculated from the measured surface profiles with Airy wave theory. A synthetic dataset (in which the wave-associated and turbulent components are prescribed) is employed to assess any artifacts that the various decomposition methods may induce. Finally, we analyze the structure of the experimental turbulent velocity fields, calculating the length scales of the turbulence and uncovering a spatial structure that mimics that found in turbulent flows without waves.
Second speaker: Kianoosh Yousefi, University of Texas
Title: Multi-scale AI modeling of near-surface turbulence over wind waves
Abstract:
About two-thirds of the surface of the Earth is covered by the ocean. The air-sea exchanges of mass, momentum, and energy that take place at the ocean surface over such a huge area play an integral role in determining the sea state, weather patterns, and climate and thus significantly impact many aspects of human life. In particular, surface waves, which most of us are familiar with from going to the beach, are crucial in connecting the atmosphere and ocean by generating turbulence, airflow separation, and breaking events. Although we know that surface waves are critically important, we do not yet fully understand the fundamental physics of ocean waves and their associated processes that couple the turbulent boundary layers above and below the ocean surface. This prevents us from making accurate model predictions of extreme wind events such as tropical storms and hurricanes.
Over the last several years, we have investigated, in detail, the influence of surface waves on the structure of airside turbulence and flux transfers across the air-sea interface using a combination of controlled laboratory experiments and data-driven modeling. In this presentation, I will outline our recent progress in developing supervised machine learning (ML) surrogate models for reconstructing the skin-friction drag and turbulence structure over wind waves that can serve as wall-layer representations in high-fidelity numerical simulations. These ML models were trained on laboratory measurements of airside velocity fields acquired above wind waves using particle image velocimetry (PIV) and laser-induced fluorescence (LIF) techniques.
Please note that WISE Webinars including the Q&A will be recorded and posted on the WISE YouTube Channel afterwards (https://www.youtube.com/@wisezoominars). By participating, you consent to any information you share to be included in the recording and shared.
Best wishes,
Alvise, Bernard**,** Qingxiang**, Tripp, Morteza** and Alberto**.**
(The WISE Webinar organizing committee)