In this part,
we are going to talk about the behaviour of airflow wing NACA_12
with an incoming transonic flow(Mach=0.85).We used an unstructured
grid for this simulation.This study show the differents caracteristics
for the flow with differents attack angles.In the second time we
present the effect of this evolution in the pressure-coefficient
(Kp) and the coefficient lift .
1) THE UNSTRUCTUCTURED GRIDS:
In AVBP, we can use for meshing,stuctured and unstructured grids.For this
simulation we used the second one
who can take different polygons.The
unstructured grids give a lot of flexibilities for complex configurations
but require
to add storage for the list of
element to vertex pointers and an overhead for first looking up the number
of the forming nodes in the table before loading the corresponding
solution values(indirect addressing).The mesh generation algorithms for
triangular and tetrahedral meshes for Euler are robust and mostly automated.
2)THE NACA_12 SIMULATIONS:Grid for NACA_12 simulation
We present and analyse the isopressure simulations because the distribution of pressure create the lift force.
Attack Angle_0:
Criterion convergence for all simulation is around 10^{-7}
INTERTPRETATION:
In general
analysis we can say and see we have a shock wave for each incidence angle
and this wave move on the extrados wall.For the Angle_0 we have two shock
waves and they are antisymmetric,it is the fact we are an attack and a
wing symmetric.For the other angle until the take down we have the shock
in antisymmetric with attack angle.
After the "take down "(Attack Angle_25)we have a distribution
of the pressure very differente,in the attack edge a great pressure
density and near the leak edge a great loss pressure.This importance difference
occurs "the take down".
DISCUSSION:
We can say in the first time we obtained goods
results for the incoming transonic NACA_12 simulation .We have a shock
for a transonic flow like the theory and the differents experiences.But
we obtain a take down point at 25 degrees whereas we should have around
17degrees.This fact is that we do not worry about the layout boundary.
In did our simulation resolve the Euler equation.In
perfect fluide,there is a solution for Euler equation
drawing the flow around an obstacle.This solution is
an approximation of the Navier-Stokes equations available
almost everywhere in stead of near the wall.And too AVBP
code treate the Euler equation with a good precision,that why we
can represent the behaviour of the wing in differente flow.