Session: 06-16-01 Wave Mechanics, Modeling and Wave Effects - I

Submission Number: 177500

Full Spectrum Downscaling of Multi-Directional Irregular Waves From Metocean to Near-Field Scales 

Marine structures are subjected to the forces and impacts of ocean waves, making a thorough understanding of sea states and wave conditions essential for safe and efficient design. In coastal regions, complex bathymetry and irregular shorelines induce a wide range of wave transformations, such as refraction, diffraction, shoaling, and breaking, resulting in highly nonlinear, spatially-variable, and complex wave fields. This complexity poses significant challenges when defining design wave conditions, as conventional deep-water spectral formulations cannot be directly applied to nearshore environments.

To accurately characterize coastal design sea states, it is necessary to derive boundary conditions from reliable meteorological and oceanographic (metocean) datasets and simulate wave propagation and transformation across the relevant topographic and bathymetric features. The NORA–SARAH procedure provides a robust framework for such metocean downscaling, linking large-scale datasets to near-field wave–structure interactions through a combination of phase-averaging and phase-resolving numerical models.

Currently, this downscaling process often follows a parametric approach, in which key wave parameters, such as significant wave height, peak period, principal direction, and directional spreading, are fitted at each interface between modeling stages. While effective, this approach can introduce uncertainties and distortions in the spectral shape of the waves.

To address these limitations, this study introduces a directional spectrum-based approach that maintains the full spectral information across all downscaling interfaces. By directly transferring the directional spectrum rather than fitted parameters, the method minimizes uncertainty and preserves the integrity of the wave energy distribution. Each interface in the downscaling chain is verified to ensure spectral consistency and physical fidelity.

The enhanced NORA–SARAH framework is then applied to a representative engineering case to demonstrate its workflow, accuracy, and performance. The results confirm that the proposed method enables a more realistic, efficient, and streamlined derivation of coastal design wave conditions. Through this advancement, the growing metocean hindcast data and recent progress in numerical modeling can be more effectively harnessed to support coastal and ocean engineering design, risk assessment, and long-term resilience planning.

Presenting Author: Widar Weizhi Wang Norwegian University of Science and Technology

Presenting Author Biography: Widar Weizhi Wang is a researcher in the development team of the open-source hydrodynamics suite REEF3D at the Norwegian University of Science and Technology, where he is dedicated to the research on numerical wave modelling at different scales for a wide variety of topics on ocean engineering, coastal engineering, coastal protection, adaptations and marine renewable energy. He has also been working with data-driven wave prediction and metocean downscale methodology.

Authors:

Widar Weizhi Wang Norwegian University of Science and Technology
Hans Bihs Norwegian University of Science and Technology