A Tomographic PIV Study and Comparison of Vortex Identification Methods on NACA 63-215 Hydrofoil Wake Structure

Abstract

The unsteady flow field in the vicinity of a NACA 63-215 hydrofoil in a closed-loop water channel at Reynolds number of Re ≈ 29103 is investigated experimentally. A Tomographic Particle Image Velocimetry (TomoPIV) is used to determine the velocity field in the near-wake region of the studied hydrofoil. The manufactured hydrofoil was mounted on the 3D traverse and installed vertically in the water tunnel test section. The TomoPIV measurement volume was performed in a voxel with the volume of 164 × 168 × 82 mm3 (X, Y, Z). Vortex identification techniques including Q-criterion and λci criterion, together with helicity of flow are evaluated in the wake of the hydrofoil. Vorticity and swirling strength are used to further understand the location and behavior of the dynamic pattern of the vortex shedding in the trailing edge of the hydrofoil. The vorticity magnitudes as they transport downstream is explored to dissipate their energy in the wake. The flow pattern reflects a turbulent behavior required for higher efficiency of the designed hydrofoil. The results are compared with literature. This work obtains a validated model for the wind farm case and will be a basis of the ocean current turbine arrays wake structure analysis.