Transition from laminar to turbulent flow under action of acoustic vibrations

An experimental study was made of the transition from laminar to turbulent flow, with the formation of two conical jets, under the action of acoustic vibrations. The experiment was performed with air discharge through a capillary nozzle, using a smoke generator for visualization, a sound generator for acoustic action, a piezoelectric crystal for measurements, and a camera for recording the flow pattern. A laminar jet was found to be most sensitive to acoustic vibrations at a frequency of 9 kHz and, therefore, the sound generator was operated at that frequency. Slight frequency deviations were found to change the positions of both cones relative to the sound generator. The effect of smoke particles and air preheating on the test results was determined by separately aiming the jet at a water surface and recording the velocity distribution in this configuration. The study revealed the existence of diverse acoustic segments in a laminar stream and a substantial difference between laminar-to-turbulent transitions with or without acoustic action respectively.