A natural coastal blowhole as a novel wave energy extraction mechanism; experimental, cfd, and probabilistic evaluation.

Natural coastal blowholes are rare geomorphological features in which incident waves induce oscillatory motion within coastal cavities, compressing and venting air through a surface outlet and forming a naturally integrated analogue of an oscillating water column. This study evaluates natural blowholes as a nature-based solution for low-impact wave-energy extraction using a combined experimental-numerical-probabilistic framework, with Chabahar Bay in the Oman Sea as a case study. A laboratory flume model was constructed to reproduce blowhole airflow dynamics, and outlet air velocity measurements were used to compute mass flow rate and validate a CFD model under consistent boundary conditions. The validated CFD framework was then extended to the field geometry to estimate pneumatic kinetic power, yielding a peak outlet velocity of approximately 21.6 m s⁻¹, a mass flow rate of approximately 13.0 kg s⁻¹, and an associated kinetic power of about 3 kW per vent. To represent variability in ocean forcing, a Monte Carlo framework comprising 5,000 realizations was parameterized using regional wave-climate statistics and propagated through the deep-water wave-power formulation to quantify uncertainty in wave-power flux. The mean wave-power flux is 8.7 kW m⁻¹ with a 95% confidence interval of 1.6-22.5 kW m⁻¹, and pronounced seasonal variability is observed, with mean flux ranging from approximately 4.5 kW m⁻¹ in winter to 13.2 kW m⁻¹ in summer. These results demonstrate that natural blowholes can provide measurable, site-specific energy yield while minimizing additional coastal infrastructure, and that probabilistic assessment is essential for quantifying uncertainty and seasonality governing long-term reliability.