Hornbostel - Sachs
Stopped flutes with internal duct, without fingerholes
The air itself is the vibrator in the primary sense. The standing waves are significantly confined within the instrument itself. A narrow duct directs the air stream against the sharp edge of a lateral orifice. The duct is inside the tube. The lower end of the tube has an adjustable stopper. The instrument has no fingerholes. Piston pipes [swannee whistle].
Stopped flutes with internal duct, without fingerholes with adjustable stopped lower end