Linearized Dynamics of Bubbly and Cavitating Flows in Cylindrical Ducts

The present work investigates the dynamics of the three-dimensional, unsteady flow of a bubbly mixture in a cylindrical duct subject to a periodic pressure excitation at one end. The results are then applied to the case of the idealized pressure excitation generated by the rotor stage of a turbomachine with the objective of understanding the dynamics of an inlet or discharge duct filled with bubbly liquid. The flow displays various regimes (subsonic, supersonic and super-resonant), with radiacally different propagation characteristics. Depending on the dispersion of the gaseous phase in the bubbly mixture and the angular speed of the turbomachine, the dynamic effects due to the bubble response can be significant, and the flow no longer behaves as a homogeneous barotropic fluid, as is commonly assumed. Examples are presented to illustrate the influence of various flow parameters.