Collaborative Research: Modeling wave breaking onset and dissipation in energy-conserving models for surface waves

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Wave breaking is a crucial process affecting a variety of ocean and coastal science and engineering problems both offshore and in the nearshore of great societal importance. This study will develop algorithms for the detection of wave breaking initiation, breaking conditions, and energy dissipation due to wave breaking, for use in phase-resolving ocean wave propagations models. Extensive validation and sensitivity analysis will be performed against recent high-fidelity numerical simulations and laboratory and field data. The robustness of the developed formulations will also be compared with existing breaking models. In addition to developing the parametrizations, this study will quantify uncertainties associated with various parametrizations of wave breaking in operational phase-resolving wave models. The model-field data comparison during storm conditions will benefit the coastal engineering community by better identifying model skill and uncertainty during storms and extreme events. The work will improve predictions of the occurrence and severity of breaking waves in phase-resolving wave models leading to: (i) a more accurate representation of wave-forcing (on currents, sediment processes, air-sea interactions, etc.) over a range of water depths, including the inner shelf, the surf zone, and river mouths; (ii) improved design analyses and safety for coastal and ocean structures and ship design. A better prediction of breaking processes and impacts during energetic/storm events will also benefit the public through improved strategies for coastal resilience. A junior scientist at the University of Washington (UW), the lead PI, will be mentored by the more senior co-PIs, which will help him transition to a permanent appointment. The project will support a female graduate student at the University of Delaware, who will be co-advised by the PIs. Outreach will be conducted at the annual "Discovery Days" event at the University of Washington.A new, unified, and robust closure model for parameterization of the onset and progression of wave breaking in phase-resolving, energy-conserving surface wave models is proposed, applicable to Boussinesq (commonly used in shallow water) and High-Order Spectral (HOS, commonly used in deep water) models. The proposed work is motivated by and builds on recent results obtained using high-fidelity numerical simulations, which establish that the onset and strength of breaking of an individual wave crest can be determined solely from local properties of the evolving crest as it approaches breaking in arbitrary depth. The new closure model will improve on existing methods by providing a formulation that is adaptive to individual wave crests, as opposed to being calibrated based on the general features of the wave train. Extensive validation and sensitivity analysis of the proposed breaking closure model will be performed against recent high-fidelity numerical simulations, available laboratory experiments, and recent and ongoing field observations during storm conditions. Both the latter data and its use in numerical modeling are quite novel and will establish a unique model-field data comparison procedure as it requires initialization of the phase-resolving model using a wave field reconstruction algorithm. The robustness of the proposed breaking closure model will also be compared with existing breaking models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.