Researcher in Experimental Aeroacoustics Daniele Ragni (AWEP), co-applicants Mirjam Snellen and Sybrand van der Zwaag and postdoc Francesco Avallone were awarded an NWO-OTP subsidy worth € 624.888 for the IPER-MAN project:  Innovative PERmeable Materials for Airfoil Noise reduction.  The funding allows Ragni to appoint two PhD students and a postdoc researcher to do research on the abatement of airfoil self noise, using a new flow porous material constituted by “open foams with directional cavities”.  The IPER-MAN project started as a multidisciplinary faculty X-FRIS project put together by Daniele Ragni (Assistant Professor, Wind Energy),  Mirjam Snellen (Associate Professor, ANCE), Sybrand van der Zwaag (Full Professor, NOVAM) and Francesco Avallone.  


The IPER-MAN project aims to decrease the airfoil self noise of aircraft wings and wind turbine blades with a new flow porous material constituted by “open foams with directional cavities”. This revolutionary concept allows shaping the macro characteristics (edge geometry, angles) of conventional passive noise reduction techniques, into the micro ones of the porous structure (porosity, cavity orientation), towards the creation of a material able to mitigate noise by both dampening flow fluctuations and reducing acoustic scattering. Addressing both hydrodynamic and acoustic aspects of noise is extremely challenging due to the different flow scales and physical mechanisms involved. The proposed research aims at studying, designing and prototyping inserts for wind tunnel wings with open foams able to work at a multi scale level. Flow features will be studied to shape within the material the optimal flow path for noise mitigation. The study will focus on relevant noise sources in aeroacoustics: abatement of turbulent boundary layer trailing edge noise in wind turbine blades and abatement of flap side and leading edge noise in aircraft wings.

The project will be supported by several institutions and companies leading in aeroacoustic and structural vibration studies: KU Leuven, LM Wind Power, VKI and DNW. The main activities will be conducted in the laboratories of the TU Delft Faculty of Aerospace Engineering.


The IPER-MAN project started as an X-FRIS project. The Aerospace Engineering Cross Fertilization Research Incentive Scheme (X-FRIS) is a scheme that was set up by the faculty of Aerospace Engineering to increase research activities that encompass two or more departments. IPER-MAN was a joint proposal by Daniele Ragni and Francesco Avallone (Wind Energy), Mirjam Snellen (ANCE) and Sybrand van der Zwaag (NOVAM). X-FRIS is intended to catalyse the interaction among tenure trackers and permanent scientific staff in different areas and form teams with a bigger critical mass and broader expertise base to start a challenging research project with a long lasting potential.

Read more:

On IPER-MAN on the NWO-website
On X-FRIS on the
TU Delft intranet

Are you interested in meeting these researchers in person? They will present their research on 6, 7 and 8 June during the TU Delft Research Exhibition. More information and registration. 

Picture by Daniele Ragni