Computational investigations of blunt trailing-edge and twist modifications to the inboard region of the NREL 5 MW rotor

The effects of twist and section shape modifications in the inboard region on the aerodynamic characteristics of the NREL 5 MW rotor have been examined using a Reynolds-averaged Navier–Stokes method OVERFLOW2. The baseline rotor blade was modified by increasing the trailing-edge thickness over the inboard region by modifying the sections’ thickness distribution aft of the maximum thickness location. Results when compared with the baseline rotor show that a modest increase of trailing-edge thickness to 10–20%c increased power capture by 1%. Further increases in trailing-edge thickness decrease in effectiveness to the point of reducing power capture when thicknesses reach 40%c. Increasing trailing-edge thicknesses also leads to an increase in thrust, but this load is concentrated in the inboard region, resulting in a small increase in root bending moments. The blunt trailing-edge concept greatly reduces the spanwise extent of inboard flow separation evident in the baseline NREL 5 MW rotor. The low-pressure region aft of the trailing edge, created by the geometry, acts to reduce the spanwise spreading of the inboard separation. Rotors with modified twist distributions over the inboard 35%R of span are also compared. Inboard twist angles are varied from + 6° to − 6° from the baseline twist schedule. Increasing inboard blade twist reduces overall rotor power capture but reduces thrust at a faster rate. Power capture remains constant with decreasing inboard geometry twist, whereas thrust increases approximately linearly by 0.75% for a decrease in thrust of 6°. Copyright © 2012 John Wiley & Sons, Ltd.