Berkeley Fluids Seminar

December 3, 2014

Samuel Kanner (Mechanical Engineering, UC Berkeley)

Validation of Implicit LES Simulation Using NACA0012 Airfoil and Low-Re Vertical-Axis Wind Turbine

A high order ILES method in 2D and 3D is used to simulate the aerodynamics of a NACA0012 airfoil over large angles of attack at low chord Reynolds numbers (5e3 ≤ Re ≤ 50e3). The 2D code is found to have good agreement with lift and drag experimental data for pre-stall angles of attack, while the 3D code is found to have good agreement over all angles of attack. The method is able to accurately predict the magnitude and frequency content of the lift and drag forces on the airfoil throughout the range of Re considered in this study. Further comparisons to experimental data are made, including PIV vorticity data as well as dye-injection data. As an extension of this application, a section of a constant spinning straight- bladed vertical-axis wind turbine with two blades at a similar Re is subject to various inflow velocities in 2D and 3D. The pitch angle of the blades was also varied in order to take into account the uncertainities in the mounting angle of the blade in the experimental studies. As found previously, a small toe-out angle can increase the power absorption of the turbine on the order of 10%. The computed tangential forces as a function of the azimuthal angle agree much better to the experimental data at high tip-speed ratios as compared to other, lower-fidelity analytical turbine codes.

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Acknowledgments

Prof. Graham Fleming (Vice Chancellor for Research, UC Berkeley)

Prof. Eliot Quataert on behalf of The Theoretical Astrophysics Center and the Astronomy Department (UC Berkeley)

Prof. Philip S. Marcus on behalf of the Mechanical Engineering Department (UC Berkeley)

Prof. Michael Manga (Earth and Planetary Science, UC Berkeley)

Prof. Evan Variano (Civil and Environmental Engineering, UC Berkeley)