**Variation of the incidence with the NACA 12 profil**

*I ntroduction*

The simulations are done in the following conditions:

-The Mach number is 1.2

-We used the coarse mesh

-The incidence goes from 0 to 35 degres

We did 6 simulations between these two values and will only present a few ones.

Thanks to a fortran code, we manage to calculate the lift coefficient on the profil.

Then our study led to the lift coefficient graph depending
on the incidence.

__Simulations__

We simulate the flow around the airfoil thanks to AVBP that reads the
run.dat giving the main commentaries about the case, such as the mach,
the number of simulation and the name of the files for the grid and the
results.

__Incidence of 0 degres:__

As the Mach is 1.2 we can see as presumed , a chok in front of the airfoil
with a subsonic domain in green before the obstacle, and then a decrease
of the mach at the end of the profil.

The higher the Mach number gets, the closer of the profil the chok
will be qnd the smaller the subsonic domain will get.

__Incidence of 5 degres:__

__Incidence of 15 degres:__

As the incidence increases, the speed get higher on the extrados and
slower on the intrados.

This explains the existence of a chok beneath the airfoil for 5 degres
of incidence that desappears for 15 degres incidence.

Still we can observe the subsonique domain before the profil but it
gets very small for 15 degres.

__Lift coefficient__

The fortran code calculates the lift on the profil for each simulation,
the coefficient is higher on the extrados than on the intrados

The following graph on XMGR represents the lift coefficient on the
profil , the abscisse is the lenght of the airfoil divided by the rope
for an incidence of 15 degres. The value decreases as we go from the extrdos
to the intrados.

As the incidence increases, the surface increases what leads to the
growth of the drift coefficiemt for the all airfoil .

After a few simulations for different incidences, we can draw the following
graphe:

Theoricaly, The NACA12 profil should drop after 16 degres,here, we can
notice that the lift coefficient increases slower after 20 degres but does
decreases even for an incidence of 35 degres.

A good explaination of this is that the simulation are done in Euler
and not Navier Stockes so that the lift doesn`t decrease.

We tried to solve this problem on the profil A in the following part.