In this part, we will simulate the wake of the nacelle

We already know that the sensor will be placed on the upper part of the nacelle, so we will focus our study on this upper domaine.

Sketch

First we create a sketch of the fluid domain.

Right click 3D-CAD Models $\rightarrow$ New

Then we creat a new sketch on the XY plane,

Then we use the entities shown above to creat our sketch.

Then we create a domain with the following dimensions :

$L_H \simeq$ 8 x hight of the nacelle

$L_{upstream} \simeq$ lenght of nacelle

$L_{downstream} \simeq$ 2 x lenght of the nacelle

Then we make an extrude of this sketch, in order to be able to make the simulation :

The domain looks like this:

Then we rename each boundary by right clicking on the surface $\rightarrow$ rename.

The region

Then we create the region:

In **Parts** node ,right click on **Domain** $\rightarrow$ **Assign part to regions**

Physics continuum

It is now important to define each kind of Boundary Condition:

Then we have to create a physics continuum by right clicking on **Continua $\rightarrow$ New $\rightarrow$ Physics Continuum** and select the physic models required by the simulation, here we shose:

**Mesh**

Now we have to create the mesh,

right click **continua** $\rightarrow$ New $\rightarrow$ Mesh Continuum, to choose models right click on Models $\rightarrow$ Select Models

The mesh consists of predominantly non-uniform rectangular cells with fine resolution near the nacellein order to capture the boundary around the nacelle. This will allow us to optimize the computing time.

a zoom on the nacelle region shows the refined mesh in this part:

We can also make the mesh finer on a selected block, as the following figure shows:

Finally the mesh is generated by successively clicking on the the following buttons

**Results**

we follows similar steps to the first part in order to get the results,

We can create a line probe to get the velocity values on this line,

**Derived** $\rightarrow$ **Parts** $\rightarrow$ **New** **Part** $\rightarrow$ **Probe** $\rightarrow$ **Line... **

We plot the streamlines afterwards,

**Derived** $\rightarrow$ **Parts** $\rightarrow$ **New** **Part** $\rightarrow$ **Streamline...**

Velocity field is represented in the following figure for an upstream velocity of $10m/s$

A zoom on the nacelle:

We plot here the velocity measured by the sensor $s_1$ as a function of the velocity upstream the rotor:

- Position of sensor $s_1$: $0,5\ m$ above the pod and $0,5\ m$ from the end,
- calibration equation: $y=-0,176+1,044 x$
- the residual norme for this method: $1,6\ .10^{-4}$.

One can notice that the residual is very tiny, because we didn't simulate the rotor which is the most important source of turbulence.

Once we simulate the rotor, one can plot the calibration equation for different points above the nacelle, and find the point with the less residual norme**.**