• propeller noise reduction airfoil unsteady loading

Along with several other projects also involved in DINNO-CROR (Design of innovative Counter-Rotating Open Rotor), the main objective of the Research Master Project to which this thesis has contributed is the improvement of adverse noise characteristics of Counter-Rotating Open Rotors. In particular, this Research Master Project intends to evaluate the effect of porosity in front-rear rotor interaction, by studying a low speed, simplistic arrangement where rotor wake impinges on a steady 2D airfoil, featuring porous and non-porous surfaces.
The project is twofold: a core experimental approach is combined with a simplistic theoretical model which, in the end, has to be able to correlate and predict noise levels for a certain configuration.
The main contribute of this work has been developing the model and the code to predict the response of a porous airfoil to an incoming gust.
Acoustic measurements have been carried over different sets of solid/porous flat plates and airfoils downstream a rotor, at VKI anechoic wind tunnel facility. Noise reduction could not be confirmed tough; experimental errors were found to be of the same order as the expected reduction.
The model, despite being conceptually simple, reproduces acceptably enough most of the physical phenomena involved. And, at a certain degree, model is able to predict steady lift loss due to porosity; this is not the case for drag increase.