# 2. Simulation

With the geometries generated, we can create the simulation itself and attach them to it
with their boundary conditions.

## Creating the simulation

Now we go to the **Simulations** tab and hit create a new simulation, which we will call
`ABL Cat2`. With this we will start setting up the configurations.

## Geometries and their boundary conditions

After creating the simulation we need to add the geometries to it. We will add both the
plane and the roughness elements.

When adding a geometry, we need to set its boundary condition. By default it is no-slip.
For the roughness elements, we keep the no-slip BC. For the plane, because this is an ABL
case, we set its BC to **ABL Wall Model** and the roughness length to the one of the
category we are interested in, which for CAT 2 is {pv}`0.05 m`.

```{eval-rst}
.. figure:: /_static/img/workshops/first-abl-simulation/02-sim-geometries.png
    :align: center

    Plane and roughness elements added to the simulation, each with its boundary condition.
```

## Next steps

With the simulation created and the geometries attached, we can move on to the
[mesh setup](03-mesh.md).