Analytical and Computational Fluid Dynamics Models of Wells Turbines for Oscillating Water Column Systems

Abstract

The sea is an important renewable energy resource for its extension and the power conveyed by waves, currents, tides, and thermal gradients. Amongst these physical phenomena, sea waves are the source with the highest energy density and may contribute to fulfilling the global increase of power demand. Despite the potential of sea waves, their harnessing is still a technological challenge. Oscillating water column systems operating with Wells turbines represent one of the most straightforward and reliable solutions for the optimal exploitation of this resource. An analytical model and computational fluid dynamics models were developed to evaluate the functioning of monoplane isolated Wells turbines. For the former modelling, a blade element momentum code relying on the actuator disc theory was applied, considering the rotor as a set of airfoils. For the latter modelling, a three-dimensional multi-block technique was implemented to create the computational domain with a fully mapped mesh composed of hexahedral elements. The employment of circumferential periodic boundary conditions allowed for the reduction of computational power and time. The models use RANS or u-RANS schemes with a multiple reference frame approach or the u-RANS formulation with a sliding mesh approach. The achieved results were compared with analytical and experimental literature data for validation. All the developed models showed good agreement. The analytical approach is suitable for a fast prediction of the turbine operation during the first design stages, while the CFD models are indicated for further analysis of the selected configurations.

The Energy Conversion and Coupling Technologies of Hybrid Wind–Wave Power Generation Systems: A Technological Review

“…Although OBs have been used in several commercial projects, the high damage rate of their mechanical components results in high maintenance costs [102][103][104]. Compared with other wave energy converters, oscillating water column devices (OWCs) are more suitable for integration into hybrid wind-wave systems.…”

“…The number of studies on the hybrid wind-wave systems using OWCs has gradually increased in recent years. Among the various wave energy converters, the energy capture efficiencies of OWCs are relatively high [104,143]. OWCs can be installed on wind turbine towers, platform foundations, or floating platforms, exhibiting strong construction flexibility.…”

Analysis of the Energy Loss Mechanism of Pump-Turbines with Splitter Blades under Different Characteristic Heads

“…In the numerical simulations, Navier-Stokes equations based on Reynolds time averaging were used, and the SST k-ω turbulence model was used [24][25][26][27][28].…”

“…The rotating component moves using the Moving reference frame, and the rotational speed is set to a test value. The SIMPLEC algorithm is used to solve the flow fields, the second order upwind format is used to discretize the convective terms and diffusive terms, the wall condition is set to no-slip wall, and the root mean square of the residuals is set to 10 -5 [28]. During the simulation, the interface between the rotating domain and the static domain is dealt with by means of the frozen rotor.…”

“…mean square of the residuals is set to 10 -5 [28]. During the simulation, the interface between the rotating domain and the static domain is dealt with by means of the frozen rotor.…”