Session: 09-05-05 Wave Energy: Oscillating Water Columns

Submission Number: 181115

Multi-Fidelity Hydrodynamic Modeling of Oscillating Water Column WECS with Pneumatic PTO Integration 

Oscillating Water Column (OWC) devices are among the most studied wave energy converters, partly due to their inherent simple working principle. Their structure comprises a partially submerged caisson (fixed if installed on-shore, floating otherwise) interacting with incoming waves, creating a water column oscillating in their internal chamber.  On top of the water column, an air pocket is compressed and decompressed by the oscillating water, determining an airflow through the chamber outlet, which activates a turbine connected to a generator able to convert wave energy (stored in the air pressure differential) into electricity. OWCs working principle and energy extraction process — the latter is referred to as pneumatic power take-off (PTO) — heavily rely on the interaction between water and air inside the chamber; therefore, an accurate and efficient modeling incorporating the pneumatic effects is crucial to properly assess the WEC performance. Within this scope, a high-fidelity method, developed in a single-phase SPH (Smoothed Particle Hydrodynamics) framework coupled with an analytical chamber model, has been implemented in DualSPHysics software [1]. This method has been validated for fixed and floating OWC devices [2, 3] showing reliability in accurately modeling their pneumatic PTO. However, CFD-based (hi-fi) simulations, such as the ones mentioned in [2, 3] and performed in DualSPHysics, can be quite computationally expensive when optimization studies are intended to be conducted over a broad scenario involving many wave conditions and device configurations. On the other hand, it is well known that low-fidelity methods exhibit a higher computational efficiency, albeit at the expense of reducing the accuracy, especially when relevant non-linearities are involved, as it is likely to occur when a strong coupling between hydrodynamic and pneumatic systems — like the one that develops inside an OWC chamber — is expected.

 

Herein, we propose a multi-fidelity approach relying on a BEM solver coupled with WEC-Sim tool to handle lo-fi predictions and DualSPHysics as a hi-fi simulator. The hybrid approach consists in tuning the parameters involved in the low-fidelity scheme according to the results obtained from high-fidelity simulations for a certain device configuration (fixed or floating) and sea state. Then, a set of low-fidelity simulations with adjusted parameters is employed to expand the analysis, swiping over a wider set of sea states and considering different device features, as, for instance, the relative dimensions between the significant geometric characteristics of the OWC, to find optimal performance ranges. Once such ideal configurations are identified, high-fidelity (CFD) simulations are carried out for a set of parameters in the vicinity of the low-fidelity predicted optimal ones, both to substantiate lo-fi predictions and provide a more informative and accurate analysis concerning forces, pressures, and power estimations.

 

Overall, high-fidelity simulations serve as ground-truth for low-fidelity ones, in turn, the latter speed up the search for optimal characteristics. Such solutions will be further fine tuned through CFD simulations. The novelty for this work lies both in the synergy among the (hi-fi) CFD software DualSPHysics and the (lo-fi) BEM solver combined with WEC-Sim simulator, and in the possibility of performing an optimization study for OWCs in a high fidelity framework.

 

[1] Domínguez et al., (2022). DualSPHysics: from fluid dynamics to multiphysics problems. Computational Particle Mechanics 9, 867–89. doi:10.1007/658s40571-021-00404-2.

[2] Mina et al., (2026). Numerical validation of a pneumatic power take-off model for fixed and floating OWC devices within DualSPHysics. Ocean Engineering (Under Review).

[3] Mina et al., (2024). Hydrodynamic modeling of OWC and U-OWC wave energy converters using the SPH method. Proceedings of 6th RENEW Conference. doi:10.1201/9781003558859-29.

Presenting Author: Beatrice Mina University School for Advanced Studies (IUSS) Pavia

Presenting Author Biography: The author is a PhD student enrolled in the Sustainable Development and Climate Change program at IUSS Pavia. Her expertise is in high- and low- fidelity modeling of Oscillating Water Column wave energy converters and their pneumatic power take-off.

Authors:

Beatrice Mina University School for Advanced Studies (IUSS) Pavia
Malin Göteman Uppsala University
Bonaventura Tagliafierro Uppsala University
Iván Martínez-Estévez Universidade de Vigo
Alejandro j.c. Crespo Universidade de Vigo
Moncho Gómez-Gesteira Universidade de Vigo
Giovanni Malara Università "Mediterranea" di Reggio Calabria
Vincenzo Nava Politecnico di Torino
Felice Arena Università "Mediterranea" di Reggio Calabria