Investigation of the rotational effect on the separate flow over sections of wind turbines: coherent structures and rotational augmentation

• Grant number: 24/13249-1
• Support Opportunities: Regular Research Grants
• Start date: December 01, 2024
• End date: November 30, 2027
• Field of knowledge: Engineering - Aerospace Engineering - Aerodynamics
• Principal Investigator: Daniel Sampaio Souza
• Grantee: Daniel Sampaio Souza
• Host Institution: Faculdade de Engenharia. Universidade Estadual Paulista (UNESP). Campus Experimental São João da Boa Vista. São João da Boa Vista , SP, Brazil
• Associated researchers: Daniel Rodríguez Álvarez

Abstract

The aerodynamic response of inboard sections of rotating wings often diverges from the one expected for the corresponding airfoil in two-dimensional motion with the same angle of attack and Reynolds number. The effects of the apparent forces, centrifugal and Coriolis', and the radial pressure gradient increase the lift generation capability of the section. This increase, frequently referred to as rotational augmentation, is particularly relevant at angles of attack close or beyond stall. Although the centrifugal pumping commonly appears as the responsible mechanism, the underlying physics is still not fully understood. For geometries and flow conditions of horizontal-axis wind turbines (HAWT), the effect ofthe apparent forces on the dynamics of the separate flow over the upper surface of inboard blade sections had limited attention. The proposed research aims at investigating the dynamics of the large turbulence structures in the vicinity of the suction surface of an airfoil operating at conditions representative of such blade section. For this, Reynolds-averaged Navier-Stokes (RANS) and delayed detached-eddy simulations (DDES) will be performed to compute the flow over an airfoil designed for HAWTs. The rotational effect on the time-averaged aerodynamics will be analyzed, as well as the evolution of the large scale structures in the region of separate flow. The computations will assume periodicity in the spanwise direction and thus will not be able to capture the centrifugal pumping. However, they will be used to study the relevance of other mechanisms potentially contributing to the rotational augmentation. The research should contribute for a better understanding of the underlying physics of the rotational augmentation, and thus for better aerodynamic models and efficient flow control strategies. (AU)