Amplification of the forcing and tonal noise in transonic high-pressure turbines

The present paper studies the dominant blade-row interaction in a transonic high-pressure turbine rotor by analyzing the radiated tonal noise and force harmonics. The turbine outlet pressure was measured with fast-response Pitot probes. The frequency spectra of the pressure fluctuations were split into deterministic (periodic or time-resolved) and random (timeunresolved). Emphasis is devoted to analyze the mitigation or amplification of the perturbations along the rotor blade. The evolution of the first and second harmonics along the front part of the blade highlights the main drivers of the unsteadiness. A time domain postprocessing integration of Lighthill's acoustic analogy is solved in the Fourier space, leading to the radiated tonal noise up to an observer position in the free field. The quadrupole sources are addressed with a modified Farassat solution of the Ffowcs Williams Hawkings equation.