Abstract
In this paper, the Navier-Stokes equations coupled with a Lagrangian discrete phase model are described to simulate the air-particle flows over the S809 airfoil of the Phase VI blade, the NH6MW25 airfoil of a 6 MW wind turbine blade and the NACA0012 airfoil. The simulation results demonstrate that, in an attached flow, the slight performance degradation is caused by the boundary layer momentum loss. After flow separation, the performance degradation becomes significant and is dominated by a more extensive separation due to particles, since the aerodynamic coefficient increments and the moving distance of separation point present similar variation trends with increasing angle of attack. Unlike the NACA0012 airfoil, a most particle-sensitive angle of attack is found in the light stall region for a wind turbine airfoil, at which the lift decrement and the drag increment reach their peak values. For the S809 airfoil, the most sensitive angle of attack is about 3° higher than that for the maximum lift-to-drag ratio. Hence, the aerodynamic performance of a wind turbine is very susceptible to particles. Based on the most sensitive angles of attack, the more sensitive scope of angles of attack of a blade airfoil and the more sensitive range of rotor tip speed ratios are predicted sequentially. The present study clarifies the principles for the performance degradation of a wind turbine airfoil due to particles and the conclusions are useful for the wind turbine design reducing the particle influences.
Highlights
Wind energy is one of the most important renewable energy resources
Cohan and Arastoopour [17] developed a multiphase computational fluid dynamics (CFD) model to estimate the effect of rain by simulating the water-film formation using the Lagrangian discrete phase model (DPM) and the Eulerian Volume of Fluid (VOF) model, and observed that the S809 airfoil performance is highly sensitive to the rainfall rate at low rainfall rates
+ ν∇2 ui + ρ1 FP,i where xi stands for a coordinate direction, ui denotes a component of fluid velocity vector, ρ, p and ν are the fluid density, pressure and kinematic viscosity coefficient, respectively, ∇2 represents the Laplace operator, and FP,i refers to the momentum source/sink “body force” term accounting for the particle effect on the fluid phase
Summary
Wind energy is one of the most important renewable energy resources. the performance of a wind turbine is greatly affected by the extremely complex operating environments, such as common sandstorm and rain. Wu and Cao [13] simulated the flow over the NACA0012 airfoil in heavy rain by a two-way momentum coupled Eulerian-Lagrangian approach. Their results showed significant aerodynamic penalties at low angles of attack due to rain effects and an about 3◦ rain-induced increase in stall angle of attack. Cohan and Arastoopour [17] developed a multiphase CFD model to estimate the effect of rain by simulating the water-film formation using the Lagrangian DPM and the Eulerian Volume of Fluid (VOF) model, and observed that the S809 airfoil performance is highly sensitive to the rainfall rate at low rainfall rates. The angle of attack of a wind turbine blade airfoil will be related to the rotor tip speed ratio in order to predict the more sensitive region of tip speed ratios
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