Co-simulations of a semi-passive oscillating foil turbine using a hydraulic system

Highlights: • The hydraulic system was applied to a semi-passive oscillating foil turbine. • Co-simulations using Fluent and AMESim were conducted to study such system. • The foil stops briefly at the endpoint of the heaving motion for the novel system. • Kinematic parameters have a more obvious impact on the hydrodynamic behavior. • Mechanical parameters affect the power output performance more significantly. Turbines based on oscillating foils possess obvious advantages in shallow waters. In this study, a hydraulic system was designed for the semi-passive oscillating foil, which is more suitable for practical applications than the traditional spring-damper system. Co-simulations using software Fluent® and AMESim™ were carried out to examine the performance of the hydraulic system. Based on the results of the spring-damper system, three typical cases were analyzed for each variable to study the effects of kinematic and mechanical parameters. The results demonstrated that the oscillating foil based on the hydraulic system could achieve a regular heaving response. However, a significant feature of the developed system is that the foil stops briefly at the endpoint of the heaving motion. The kinematic parameter had a significant effect on both the hydrodynamic characteristics and the heaving response. Maximum energy is harvested at reduced frequency f ∗ = 0.10, while the maximum efficiency occurred at f ∗ = 0.125. The mechanical parameters, including the spring, cylinder radius, and rotary load, affected the hydrodynamic characteristics slightly. However, the parameters of the cylinder and the rotary load had a significant impact on the heaving response and the power output performance. The results also indicated that the unstable heaving response should be avoided, as it would decrease the energy harvesting efficiency.