Sectional prediction of lift coefficients on rotating wind turbine blades in stall

Aim of the investigations was to establish improved modelling of stalled flow on rotating blades in a time averaged sense, in order to predict rotor performance in the stall regime. This is achieved through the following steps, all of which are discussed in this report: (a) analysis of the boundary layer (b.l.) equations for a reference system rotating with the blades for attached and for stalled flow; (b) formulation of a quasi 3D system of b.l. equations that include the leading terms due to rotation, both for the stalled case as for the attached case; this set of equations permits strip wise calculations; (c) extension of the NLR (2D) ULTRAN-V viscous inviscid interaction code to accommodate radial flow and the 3D terms in the chord wise momentum equation; (d) implementation of the extended boundary layer equations in ULTRAN-V; (e) analysis of the FFA measurement in the CARDC tunnel in order to obtain c[sub 1]-[alpha] data at different sections on the rotating blade; (f) calculations with the extended code for the FFA configuration and comparison between calculated and measured results; (g) analysis of the differences and determination of a calibration constant; (h) determination of a simple correction formula to obtain rotating c[sub 1]-[alpha] data from measured 2D data, based on curve fitting of calculated results; (i) comparison of data obtained with the method developed with measurements executed on the DUT test rotor. Finally a number of power curves calculated with the synthesized 3D c[sub 1]-[alpha] data are compared with measurements. Results produced with this input are much closer to measurements than calculated power curves with 2D airfoil date. Parts of the results discussed in this report were published in conference proceedings, during the course of the investigations. In the present report comprehensive view of the modelling efforts of the entire project is given. 24 figs., 4 tabs., 2 appendices, 24 refs.