Aeroacoustic Response of Turbine Blades to Rotational Speed and Angle of Attack Variations in Unsteady Flow Conditions

The noise generated by a blade is assumed as one of the most central acoustic generation sources in a turbine. The sound induced by the movement of turbulent fluid over the turbine blade and its interaction with the surrounding environment causes the presence of vortices of different sizes in the turbulent flow. These vortices are considered as the major sources of acoustic waves in a wide range of frequencies. In the present study, the acoustic field induced by turbine blades is simulated by the aid of numerical simulation. In this respect, the flow_field around the blades is solved by using the flow governing equations and then the acoustic solution of flow is modeled by using the Ffowcs Williams-Hawkings acoustic model. The main objectives of the present study include investigations of sound propagation at different distances of turbine axis, the extent of sound propagation along the blade direction, and the effect of the cavity implemented over the blade on acoustic results. The obtained results reveal that the sound pressure level generally decreases as the observer’s distance increases. Furthermore, based on the obtained results, one can infer that the reduction in the sound pressure level is triggered by the presence of larger vortices with higher energy close to the blade (a larger sound pressure level) and smaller vortices at a further distance from the blade (a lower sound pressure level). Numerical simulations indicate that adding a cavity to the turbine blade does not reduce noise but instead increases the acoustic generation level.

کلیدواژه ها:

Turbine Aeroacoustics ، Numerical Simulation ، Sound Pressure Level - SPL ، Turbulent Flow Vortices ، Ffowcs Williams-Hawkings Model - FW-H