Aerodynamic Performance of a NREL S809 Airfoil in an Air-Sand Particle Two-Phase Flow

Abstract

This paper opens up a new perspective on the aerodynamic performance of a wind turbine airfoil. More specifically, the paper deals with a steady, incompressible two-phase flow, consisting of air and two different concentrations of sand particles, over an airfoil from the National Renewable Energy Laboratory, NREL S809. The numerical simulations were performed on turbulence models for aerodynamic operations using commercial computational fluid dynamics (CFD) code. The computational results obtained for the aerodynamic performance of an S809 airfoil at various angles of attack operating at Reynolds numbers of Re = 1 × 10 6 and Re = 2 × 10 6 in a dry, dusty environment were compared with existing experimental data on air flow over an S809 airfoil from reliable sources. Notably, a structured mesh consisting of 80,000 cells had already been identified as the most appropriate for numerical simulations. Finally, it was concluded that sand concentration significantly affected the aerodynamic performance of the airfoil; there was an increase in the values of the predicted drag coefficients, as well as a decrease in the values of the predicted lift coefficients caused by increasing concentrations of sand particles. The region around the airfoil was studied by using contours of static pressure and discrete phase model (DPM) concentration.

Aerodynamic Sensitivity Analysis for a Wind Turbine Airfoil in an Air-Particle Two-Phase Flow

“…In Ref. [18], the same numerical method was applied to the S809 airfoil, and a similar difference in drag between computation and experiment was obtained. In the rest of the paper, only the increments of lift and drag coefficients due to particles are discussed, but for the lift-to-drag ratio.…”

“…where λ denotes the tip speed ratio, R and ω are the rotor radius and angular velocity, respectively, and V ∞ is the wind speed. The one-phase air flows over the S809 airfoil are computed at four Re numbers of 0.75 × 10 6 , 1 × 10 6 , 1.25 × 10 6 and 1.5 × 10 6 , which respectively correspond to the velocities: 10.955 m/s, 14.607 m/s, 18.259 m/s and 21.911 m/s. The velocity inlet and pressure outlet conditions are respectively implemented at the inlet and outlet boundaries shown in Figure 1a, and the no-slip condition is imposed on the solid wall.…”

“…In Ref. [18], the same numerical method was applied to the S809 airfoil, and a similar difference in drag between…”

“…However, if the rainfall rate is high enough to immerse most of the airfoil surface under water, a further increase in the rainfall rate does not have a substantial effect. Douvi et al [18] computed the air-sand particle two-phase flow over the S809 airfoil by combining the N-S equations with a Lagrangian DPM via FLUENT and found that there was an increase in drag as well as a decrease in lift caused by increasing particle concentrations.…”

Turbulence-Model Comparison for Aerodynamic-Performance Prediction of a Typical Vertical-Axis Wind-Turbine Airfoil

“…CFD simulations have been useful for studying unsteady effects, such as dynamic stall produced by airfoil pitching or oscillations in incoming velocity [11][12][13]. In addition, flow particularities, such as modifications of fluid viscosity [14] or the influence of suspended sand in the aerodynamic performance of airfoils [15], are difficult to model with simpler codes. Regarding airfoil geometry, CFD simulations allow the study of different modifications just by modifying the geometry in the domain.…”