Validation Study of Multi-Rotor Systems Using Two Shrouded Wind Turbines

Multi rotor systems (MRS) have shown a great potential as a future application of wind energy. In this study, the aim is simulating the aerodynamic performance of a an MRS using fully-resolved shrouded wind turbine blades then validating with experimental data. MRS for wind turbine configurations have been studied using both numerical and experimental approaches. Different case studies have been studied and the power output comparison have been reported. The wind lens turbine (WLT) obviously shows a large increase in power output compared to the bare rotor case. Besides, the twin side-by-side (SBS) WLTs shows even larger power increase compared to the case of single WLT by around 20% for computational fluid dynamics (CFD) calculations at the optimum tip speed ratio s/D of around 0.2. The increase in power coefficient in close proximity can be explained by flow interference and gap flow behaviors. Previously, we used simplified models for blade modeling like actuator line method (ALM) and actuator disk method (ADM). However, currently we are improving the accuracy using CFD with full-scale blades with higher grid resolutions. As the number of units for an MRS is increased, the increase in power output becomes larger and larger. This is because that the gap flows between brimmed diffuser-augmented wind turbines (B-DAWT) in a MRS are accelerated and cause lowered pressure regions due to vortex interaction behind the brimmed diffusers. Thus, an MRS with more B-DAWTs can draw more wind into turbines showing higher power output.