الفهرس 
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Abstract
Leading edge slat is one of the most implemented devices for passive stall control
of flow over airfoils. The present study considers the use of a slat near the leading edge
of an airfoil to delay or suppress separation and thus improves the performance of small
wind turbines.
Flow around the S809 main airfoil with a leading edge slat is numerically simulated
using ANSYS Fluent 2019 R1 (CFD) program. The S809 is a common section usually
used for small wind turbine and low values of Reynolds number. The geometrical
parameters of slat seem to have strong effects on the slat performance. The present
work concentrates on three geometrical parameters namely the location of the slat
relative to the base airfoil, the chord size of the slat and the slat angle on installation.
A slat with a chord length of 10% of the total chord Ct is located at range of
distances +3.6% to +10.8% of the total cord length in y-axis, slat located at 9% of the
chord shows the best lift coefficient. Relative to the case with no slat it increases Cl by
68.7% at AoA=19.2⁰ and moves the point of flow separation all the way forward to the
trailing edge up to AoA=20.2⁰. To study the effect of the size of the slat, slat sizes range
from 5% to 12.5% of the total chord length of the main airfoil are numerically
investigated, slat size 7.5% of the total chord shows the best lift coefficient. It increases
Cl by 81.5% at AoA=19.2⁰. It shows a good behavior of flow over the airfoil up to
AoA=20⁰. Leading edge slat angles range from -10⁰ to +10⁰ are investigated to study
the effect of slat angle on the aerodynamic performance of the combined airfoil. Slat
angle has a positive effect on the performance of the airfoil. Installing the slat at +5⁰
shows the largest increase in lift with an increase in lift coefficient by 40% at
AoA=17.2⁰ compared with no slat condition. The slat angle Sα=0° showed an extended
range of angle of attach with high values of Cl.he improvement achieved due to keeping the total chord length constant is
presented in the increase of the maximum lift coefficient by 34.8% relative to the no
slat condition with 12.8% saving of the material of the blade which corresponds to 6%
of total cost of turbine.