Development of the Akandu Wave Spectrum for the Brazilian Ocean Region Using N Spectral Moment Theory

Abstract

Accurate characterization of offshore wave environments remains fundamental to the design and operation of floating production systems, offshore platforms, subsea infrastructure and marine renewable-energy devices. Classical spectral formulations such as the Pierson–Moskowitz (PM), ISSC, ITTC and JONSWAP spectra have achieved widespread application in offshore engineering; however, they do not explicitly represent regional oceanographic characteristics. This study presents the development of a dedicated wave spectrum for the Brazilian Ocean Region using Akandu’s Nth Spectral Moment Theory. The theory provides analytical closed-form expressions for spectral moments, significant wave height, characteristic periods and spectral bandwidth through Gamma-function transformations. Regional metocean conditions corresponding to a 100-year return-period storm were employed to calibrate the spectral-shape parameters. The resulting spectrum was validated against empirical peak-period relationships and offshore metocean design criteria reported by Petrobras, DNV-RP-C205, NORSOK N-003 and API RP 2MET. Results indicate that the Brazilian Ocean Region exhibits relatively high spectral energy density and moderate spectral bandwidth compared with West African seas. A direct proportionality between spectral bandwidth and the spectral parametric quotient p/q was observed. The proposed spectrum provides an effective tool for FPSO motion prediction, fatigue assessment, mooring design and environmental load estimation in Brazilian deepwater developments.

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