The two-dimensional incompressible Navier-Stokes equations and the SST k-ω turbulence model are used to investigate the aerodynamic performance of a wind turbine airfoil under clean and rough surface conditions.The DU 95-W-180 airfoil is analysized, which is widely used in wind turbines.The numerical simulation of the airfoil under clean surface condition is performed,and the numerical results have a good consistency with the experimental data.The studies in the effects of surface roughness on performance of the airfoil are mainly as follows:computation of the lift coefficient and the drag coefficient of the airfoil under different roughness heights on full surface and different roughness locations;the trends of the lift coefficient and the drag coefficient changing with the roughness heights and roughness locations;the critical value of roughness height and roughness location;the trends of the lift coefficient and the drag coefficient changing with the roughness heights at the critical locations.Furthermore, the unsteady flow field analysis of vortex shedding induced by the surface roughness is performed.

High wind speeds associated with Low-Level Jet (LLJ) make wind resources more favorable for wind energy production. However, the aerodynamic loads of large-scale horizontal axis wind turbine (HAWT) rotor under different LLJ inflow conditions have not been thoroughly studied. To gain insight into the aerodynamic loads of rotor under LLJ inflow conditions with different LLJ intensities, a method to establish an engineering LLJ inflow model was proposed according to the plane wall jet theory and Von Karman spectra model with user-defined scaling. The parameters in the engineering LLJ inflow model were determined by comparing the wind speed distribution obtained from the GP_LLJ spectral model, which was summarized from field measurements in the real atmosphere. The LLJ fluctuating wind fields with different intensities generated by the engineering LLJ inflow model were used as the inflow conditions of Fatigue, Aerodynamics, Structures, and Turbulence (FAST) open source code to calculate and analyze the aerodynamic loads of the HAWT. It was found that the engineering LLJ inflow model can be used to establish the LLJ inflow condition of HAWT. When the LLJ height is located at the hub height and LLJ intensity increases from 8 to 16 m/s, the RMS rotor unbalanced aerodynamic load coefficients, including ones of lateral force, longitudinal force, tilt moment and yaw moment are increased by 2.2, 2.13, 1.02 and 0.95 times, respectively. ARTICLE HISTORY

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