3. Average steady-state hydroacoustic coupling

When a machine is used in a system under permanent, stable operating conditions, fluctuations in thermomechanical quantities (pressures, flow rates, flow velocities, torques, etc.) are bound to occur. These fluctuations are characterized by :

• small amplitudes compared with average sizes (ratios of less than 10%);

• frequencies that are usually harmonic with the rotation frequency of the machines, associated in particular with interactions between their fixed and moving parts;

• various frequencies that can be associated with the appearance of specific local phenomena such as cavitation or rotating detachments.

Under these conditions, another type of coupling between machine and system exists, linked to the propagation of disturbances throughout...