# Wake

The APM Solver has several options for controlling the wake. The wake_alignement option in the .conf file controls the alignment of the wake with respect to the trailing edge.
• By default the wake_alignement option is set to 0. The wake will be aligned with the freestream velocity vector at the trailing edge.
• If the wake_alignement option is set to 1 the wake will be aligned with the average trailing edge bisector. The average trailing edge bisector is calculated from the normal vectors of the trailing edge elements.
• If the wake_alignement option is set to 2 the wake will be positioned at a specific angle with respect to the
$x-y$
plane. The wake_angle option in the .conf file can be used to specify the angle. If you do not specify an angle a default value of 0 deg will be assumed.
Use the average trailing angle bisector option for best results.
The images below show the wake of a NACA4412 wing aligned with the freestream velocity vector and with the average trailing edge bisector.
Wake aligned with the freestream flow
Wake aligned with the average trailing edge bisector