# Steady simulations

![Steady simulation of a NACA4412 wing](/files/-MVX8Rk3goiKqwuYCW53)

For steady simulations, the APM Solver assumes that the wake is a flat surface that extends to infinity. The following options in the **.conf** file are changed:

* `dt`- the timestep size in seconds
* `N_timesteps` - the number of timesteps

The `dt` option must be such as to allow the wake to extend at least 100 chord lengths downstream in direction of the flow. If the airspeed is `norm_V_ref=10` m/s and the `c_ref=1` m, `dt` should be approximately 1000 s. In addition, `N_timesteps` should be set to 1.

{% hint style="info" %}
The values for airspeed and chord are arbitrary and are used for illustrative purposes.
{% endhint %}


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