الفهرس 
Literature Review
Numerical StudiesOnly 14 pages are availabe for public view
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Abstract
When a wind turbine operates in a Saharan environment under dusty flow conditions for a long time, the surface roughness of the blade will increase due to dust accumulation. Increased roughness may lead to severe DROP in performance parameters (CL, CD), which in turn may lead to significant DROP in turbine power. This work is done to provide the details of dust accumulation process over the wind turbine blades and to record the subsequent effects on performance parameters. A numerical model is created in addition to a deposition model for particles deposition using computational fluid dynamics (CFD) package FLUENT to record the degradation of performance for wind turbines which operates in dusty environments. The deposition model was created to simulate the dust build up over the blade surface. This deposition model was developed in C-language using FLUENT’s user defined functions (UDF) capability as a wall boundary condition for the blade surface upon particle impact. First the deposited mass in each cell over the blade surface after a certain operational time was obtained and stored using the deposition model along with the FLUENT’s user defined memory location (UDML) functions. This mass was then converted into an equivalent roughness height to estimate the new surface profile of the blade, and then the deterioration in performance parameters is explored for the new profiles after each study interval over one year.
The performance of a NACA 63-215 airfoil section under different operational conditions over a time period of one year has been studied. For the case study at hand and also for the purpose of validation, operating conditions similar to those of the experimental study of Khalfallaha and Koliub [1] were used. Khalfallaha and Koliub [1] conducted an on-site investigation for dust accumulation over the blades of a stall controlled wind turbine (Nordtank 300 kW). According to the technical specification and site characteristics, an average Reynolds number of 1106 can be assumed over the blade length with an angle of attack of 4.
The flow field around the two-dimensional clean and fouled airfoil section (NACA 63-215) was solved by numerical solution of the two-dimensional incompressible Navier-Stokes equations coupled with a turbulence model which is chosen to be SST k- . For validation purposes, the model results are compared with the experimental results of Khalfallaha and Koliub [1] and the numerical
results of Ren [2]. The developed model is used to assess the effect of roughness height increasing on both the lift and drag coefficients.
Key words: wind turbines, dusty flow, performance deterioration.