Efficient flow reconstruction between dual tidal turbines: Large eddy simulation and reduced order modeling approach

The present investigation seeks to analyze the fluid dynamics associated with tidal turbines in the context of the EU (European Union) project NEMMO (The Next Evolution in Materials and Models for Ocean Energy, nemmo.eu). A pair of counter-rotating tidal turbines is employed for propelling a ship. The separation between these turbines is approximately one rotor diameter. Consequently, the power output of the downstream turbine is adversely affected by the heightened turbulence generated by the rotation of the upstream turbine. This power imbalance poses a substantial challenge in terms of power management. Therefore, this study concentrates on conducting a flow analysis of these counter-rotating turbines. Large Eddy Simulation (LES) of a dual tidal turbine rotating in opposite directions is conducted using the actuator line method. The flow is scrutinized by employing proper orthogonal decomposition (POD). The flow field is then reconstructed using the reduced order method. It is observed that a reduced number of modes is sufficient to reconstruct the flow between the tidal turbines. However, more modes are necessary to replicate the flow beyond the downstream turbine. The utilization of fewer modes proves effective in comprehending the flow at the inlet of the downstream turbine, ultimately resulting in reduced computational power requirements through faster matrix operations and lower memory usage for the POD decomposition.