Investigating the Fluctuating Nature of Flow in the Hartmann-Sprenger Tube

At the outlet of a converging nozzle connected to a high-pressure gas source, based on its input pressure, an under-expanded and ultrasonic flow is created, accompanied by a shock wave. A simple design of the Hartmann-Sprenger resonance tube device is made by placing a closed-end tube in front of this converging nozzle. The impact of the shock wave and nozzle outflow jet on the tube causes intense heating in the trapped gas inside the tube. This research investigated the functional cycle of the resonance tube and the fluctuating nature of the flow inside it. The main parameters of the problem in the form of the inlet pressure to the nozzle and the distance between the tube and the nozzle, the determination and the effect of changing their value on the fluctuating performance of the flow inside the tube, and the fluctuations of the pressure at the end of the tube were shown. The dominant frequencies of these oscillations were determined and shown that in the range of input pressure from one to ten bar, the range of dominant frequencies is between 600 and 933 Hz, which are slightly different from the resonant frequency of the tube. The intensification of oscillations and dominant frequencies can only be seen in a certain number of values of the main parameters, and the intended heating is created only in these conditions.