Development and Validation of the Akandu Wave Spectrum for the Gulf of Guinea Using Nth Spectral Moment Theory

Accurate characterization of ocean-wave energy distribution is fundamental to the design and operation of offshore structures. Although classical wave spectra such as the Pierson–Moskowitz (PM), ISSC, ITTC and JONSWAP spectra have achieved widespread application in offshore engineering, they do not explicitly account for regional hydrodynamic peculiarities of emerging offshore provinces such as the Gulf of Guinea. This study presents the development and validation of the Akandu Wave Spectrum for the Gulf of Guinea using Akandu’s Nth Spectral Moment Theory. The theory provides a generalized analytical framework for evaluating spectral moments, characteristic wave periods and spectral bandwidth through closed-form Gamma-function solutions. Regional metocean conditions corresponding to a 100-year return-period storm was used to calibrate the proposed spectrum. The resulting model was validated against empirical peak-period relationships and published offshore design criteria from DNV-RP-C205, NORSOK N-003, API RP 2MET and Petrobras deepwater studies. Results indicate that the Gulf of Guinea possesses relatively narrow-banded spectral characteristics compared with the Gulf of Mexico, Timor Sea and North Sea. The proposed Akandu Spectrum reproduces observed peak-period behaviour while preserving physically realistic spectral bandwidth characteristics. The model provides a practical and computationally efficient tool for FPSO motion analysis, fatigue assessment, mooring-system design, environmental load estimation and offshore structural reliability studies.