The research focuses on the identification of noise sources and, understanding and modelling of the noise reduction mechanisms, with the purpose of developing innovative physics-based noise reduction technologies. Several engineering applications are tackled such as noise generated by rotating blades (such as fans and propellers) both isolated and installed, acoustic liners for turbofan, and noise reduction for internal comfort (i.e., HVAC systems). Research is carried out using and developing both experimental and computational methods with several levels of fidelity.
Examples of available and running projects are:
- Flow-acoustic interaction over an acoustic liners and development of novel liner technologies
The research project is supported by the ERC Starting Grant Project LINING (grant agreement 101075903).
The lack of fundamental knowledge of the interaction between an acoustic wave and a turbulent boundary layer grazing an acoustically treated surface, such as an acoustic liner, is the cause of unexpected and unphysical results found when performing the acoustic characterization of the sound absorbing surface with inverse eduction methods. This is because, in this field, acoustic and aerodynamic have never been fully coupled.
To fill this knowledge gap, the acoustic and hydrodynamic velocities near an acoustically treated surface must be measured. Since it cannot be done only with state-of-the-art experiments, because of hardware and field-of-view limitations, I propose to complement experiments with scale-resolved high-fidelity numerical simulations based on the lattice-Boltzmann very-large-eddy simulation method.
Numerical results will be used to explain the physics of acoustic-flow interaction. Advanced data analysis methodologies will be developed and applied to separate the acoustic-induced velocity near the wall from the hydrodynamic one. At the same time, the numerical database will be used to compare inverse methods, employed to acoustically characterize the sound absorbing surfaces, to explain the physical reasons behind the unexpected results, and propose physics-based corrections. Furthermore, by describing the flow-acoustic interaction, it will be possible to model and predict the drag increase caused by the coupling between the acoustic-induced velocity and the free-stream one.
The description of the flow-acoustic interaction will solve the scientific debate about the unexpected results and pave the way towards future broadband low-noise low-drag acoustic meta-surfaces to increase propulsion efficiency and reduce noise of future, more sustainable, aircraft engines.
PhD candidates working on this project will have the opportunity to work together with colleagues from many other research institutes and academia.
- Aerodynamic Noise Generated by Propellers in Turbulent Inflow
Propeller noise is today a hot topic in aeroacoustics because of the emerging UAV and UAM. These systems are characterized by many propellers, with a strong aerodynamics interaction between them, and will operate in urban environments, where the presence of gusts is dominant. Till today most of the studies on propeller noise have been carried out assuming clean inflow; therefore, little is known about how the noise footprint will change depending on the unsteady inflow of a conventional urban settings.
The research, carried out in collaboration with Delft University of Technology, aims at developing numerical approaches, suitable for computational aeroacoustics simulations, and investigate how the physical mechanisms responsible for noise reduction will change in presence of turbulent inflow and strong interactions between wakes of nearby propellers. The computed far-field noise, once validated against experimental measurements, will be auralized and used to assess people annoyance.
At the same time, once the dominant noise generation mechanisms are well characterized, we will develop low and mid-fidelity tools, to be used in the design phase, to predict both aerodynamics and aeroacoustics performances when propellers operate under these conditions.
- Noise Generation and Reduction in Installed Fan and complex HVAC systems
The development of electric vehicles together with the continuously increase demand in comfort requirements require the development of novel and more silent fan and HVAC systems.
In this framework, the research team is working on investigated the relevant noise sources, with a particular focus on the ones that appear in realistic working conditions, and it is going to develop novel noise reduction technologies using advanced concepts such as meta-materials.
This research line is carried out in collaboration with relevant industrial players with the clear goal of adopting the solutions discovered.
- Noise generation and Reduction in Distributed Electric Propulsion (DEP) Configurations
Short and mid-range aircraft will likely adopt distributed electric propulsion systems. For this configuration, many researchers have investigated the possibility to lock the phase angle between adjacent propellers to reduce noise. However, it has been noted that, even if there is no physical interaction between the blades, the aerodynamic interaction in the near wake causes a small increase of the unsteady loading on each propeller blade but with a large increase in noise along the axis of rotation. Furthermore, the effect of the wing on the wake development and, therefore, on the overall aerodynamics and aeroacoustics performances have not yet fully understood and modelled.
Within this field, research focuses on developing low and mid-fidelity methods to model the interaction between propellers and assess the effect of the time-varying loading on both aerodynamics and aeroacoustics performances.
After all these aspects are clarified we will develop noise reduction technologies that could be integrated also in the wing.