A different method to cause transition is the so called pneumatic turbulator, which may even be controlled - either automatically or by a remote control system. Such devices are well known for years and have been used in man carrying aircraft as well as in model aircraft.
Pneumatic turbulator for free flight models, 1957, from [9].
A pneumatic turbulator consists of an array of holes in the wing surface, which are used to eject a small amount of air into the boundary layer. If the amount of air is sufficient, the resulting turbulent wedges cause transition downstream of the holes. The flow through the holes can be driven by pitot tubes or by the pressure difference between upper and lower wing surface. By a clever selection of the chord position for the holes in the lower surface, the quantity of the airflow can be controlled automatically, depending on the angle of attack. A drawback of pneumatic turbulators is their sensitivity to dust and dirt, which may fill the small holes, and the amount of work to install such a device.
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