A Numerical Analysis of Water Flow past an Airfoil through 180° Angle of Attack

The oceans and seas represent a considerable source of renewable energies. Tidal energy is one of them and can be harnessed by means of completely submerged turbines.

When in operation, and in the occurrence of strong waves, the blades of a marine turbine rotor can be subject to high angles of attack. The available literature on the aerodynamic characteristics of such high angles is, at the time of writing, limited; most studies focus on small angles, in the range of 0° < α < 40°, and those computed through 180° have been obtained only for a small number of symmetrical sections.

The objective of this study is to elaborate a detailed Computational Fluid Dynamics model analysis of the drag and lift coefficients for two airfoil sections, one symmetrical and one asymmetrical (NACA 0015 and NACA 2415 respectively). The coefficients are essential in the analysis of the marine turbine system and its efficiency in exploiting natural energy.

The work has been performed on a commercial CFD software package, Star-CD. The aerodynamic characteristics for the two airfoils were obtained for angles of attack from 0 to 180 degrees for flows velocities of 0.8 and 10 m/s. In the analysis the effects of a change in magnitude of the Reynolds number, and the use of four different turbulence models, have been considered.

The results obtained for the NACA 0015 were judged satisfactory compared to experimental data. Experimental data for the NACA 2415 is unavailable, nevertheless the simulated model has behaved in line with theoretical expectations.