An actuator disc analysis is used to calculate the pressure
fluctuations produced by the convection of temperature
fluctuations (entropy waves) into one or more rows of blades.
The perturbations in pressure and temperature must be small,
but the mean flow deflection and acceleration are generally
large. The calculations indicate that the small temperature
fluctuations produced by combustion chambers are sufficient
to produce large amounts of acoustic power.
Although designed primarily to calculate the effect of
entropy waves, the method is more general and is able to
predict the pressure and vorticity waves generated by
upstream or downstream going pressure waves or by vorticity
waves impinging on blade rows
