The principle behind the sensor [ItMightBeWorse] is working ... the change in time-of-flight of an ultrasonic pulse across a moving stream of air in a duct. It’s another one of those “Why ...

Not so, if you use a pair of specialised ultrasonic transducer arrays to move the air instead! (Video, embedded below) Three banks of thrusters provide a 180 degree steerable net force Details are ...