Hartmann effect. Region of existence and oscillation frequencies

Data of experiments on determining the region of existence for auto-oscillations (Hartmann effect) with a frequency of approximately 450 Hz with variation in the distance from the nozzle to the resonator. Results of these experiments differ from the well-known results of Hartmann and his followers obtained for shallow resonators. It is shown that the region of auto-oscillations exists for large distances between the nozzle and the resonator. The results obtained are explained using the modern knowledge of the gas-dynamic structure of a supersonic underexpanded jet. It is shown that in determining the frequency of low-frequency oscillations, it suffices to allow for the resonator length and its “added” mass.