A3-D Unsteady Aerodynamic Performance Investigation For A Wind Turbine With Rotational Effects

Wind turbine rotor blade aerodynamic performance calculation could be one of the most critical challenges in wind turbine R&D field. A wind turbine is always running in the unsteady flow environment, and consequently it is necessary to study the rotor blade unsteady aerodynamic load calculation problems.In this paper, the whole structure space coordinate system for a wind turbine is established to extend the steady BEM theory into unsteady application conditions. Then the Beddoes-Leishman dynamic stall model is introduced to model the unsteady flow characteristics under attached flow, separated flow and dynamic vortex shedding situations. The computational formulas for tangential force coefficient and pitch moment coefficient have been modified. An oscillating case for S809airfoil is carried out and the result agrees well with the experiment data from OSU.To consider rotational effects during a wind turbine’s operation process, the Du-Selig stall delay model is recommended and has been validated for the UAE steady wind turbine test. It is found that the stall delay model takes on good predictions in the inner part of the blade while it shows large discrepancies in the outer region.Finally a methodology to calculate unsteady aerodynamic performance is given for a horizontal axis wind turbine rotor blade, in which the Du-Selig stall delay model coupled within the unsteady Beddoes-Leishman dynamic stall model based on the inputs provided by the unsteady BEM theory. The given integrated model is applied to a NREL/UAE two-bladed upwind stall wind turbine in yawed conditions and a comparison between the predictions and experiment results is also conducted. It can be concluded that the proposed model generally captures the unsteady aerodynamic characteristics well, but in some cases large divergences could be observed, which may note that the model need to be further amended or be limited with some application scope.The research work done in this paper may provide some theoretical references for the R&D domain and aerodynamic performance assessment for the wind turbine and be with instructive significance in the engineering calculations.