Flow dynamics inside the rotor of a three straight bladed cross-flow turbine

In this work we study experimentally the flow dynamics inside the rotor of a three straight-bladed Cross-Flow Turbine (CFT). The CFT model used in the experiments is based on symmetric NACA-0015 profiles, with a chord to rotor diameter ratio of 0.16. The turbine model was designed in order to quantify the flow inside and around the rotor using planar Digital Particle Image Velocimetry (DPIV). Tests were made by forcing the rotation of the turbine with a DC motor, which provided precise control of the Tip Speed Ratio (TSR), while being towed in a still-water tank at a constant turbine diameter Reynolds number of 6.1 × 10⁴. The range of TSRs covered in the experiments went from 0.7 to 2.3.The focus is given to the analysis of the blade-wake interactions inside the rotor. The investigation has allowed us to relate the interactions with the performance differences in this type of turbines, as a function of the operational tip speed ratio.