CFD Analysis of an Articulated-Body Wave Energy Converter: Comparison with Experimental Data and Frequency-Domain Modeling Predictions

Sammanfattning

Developing sustainable energy systems requires continued advancement in renewableenergy technologies. Among these, wave energy is considered a particularly promising resource due to its substantial theoretical potential. This thesis investigatesan articulated-body wave energy converter using a computational fluid dynamics(CFD) model developed in STAR-CCM+.To evaluate the predictive capability of the numerical model, previously conductedmodel tests are replicated under regular wave conditions. Wave periods ranging from0.7 to 2.2 seconds are considered, with the hinge-angle amplitude as the primaryresponse quantity. This response is particularly important, as it is directly relatedto the relative motion available for energy extraction.The simulation results are compared with experimental measurements and resultsfrom a previously developed frequency-domain model. The numerical setup includeswave generation, multibody dynamics, and key subsystems such as the mooring andPower Take-Off (PTO) systems. Two PTO formulations are implemented: a linearformulation and a fitted nonlinear formulation based on the measured torque-angularvelocity relationship from the model tests.Overall, the CFD models show close agreement with the experimental data acrossthe complete range of analyzed cases. They capture the experimentally observedpeak hinge-angle response and reduce overprediction near the peak compared withthe previous frequency-domain model. All CFD models predict the peak responseat the same wave period as the experiments and within 10% of the experimentalpeak amplitude, whereas the frequency-domain model overpredicts the peak by morethan 30%. Comparisons between the two PTO representations further indicate thatthis subsystem significantly influences the predicted response across the investigatedcases.Among the investigated approaches, the CFD model with the fitted nonlinear PTOformulation provides the best agreement with experimental measurements, with aglobal error of approximately 10%. However, the comparison also shows that theimproved agreement cannot be attributed solely to the hydrodynamic model, asthe PTO formulation significantly influences the predicted hinge-angle response.These findings indicate that reliable prediction of the WEC response requires notonly accurate hydrodynamic modeling but also representative subsystem input data,particularly for the PTO system.