Partial surge was kind of axisymmetric

low-frequency

hub region initiated disturbance by experimental investigations in a transonic compressor. In term of physical mechanisms

partial surge was much similar to an oscillation in a Helmholtz system. By Duct-Compressor-Plenum model

the Helmholtz frequency of the system was estimated

which was very close to the frequency of partial surge. To further verify this link between the frequency of partial surge and the Helmholtz frequency

experimental investigations were carried out with variation of specific parameters of the Helmholtz system. The results present that the frequency of partial surge varies with the Helmholtz frequency of the system. And the values of both frequency are very close. Therefore

the frequency of partial surge is determined by the Helmholtz frequency of the system.