Noise abatement procedures for propeller driven air vehicles

Abstract

Noise pollution represents a concern in society and therefore requires the development for noise abatement procedures. This work carries out the prerequisites in terms of noise optimization capabilities. The objective of this thesis is to implement a tool chain for noise footprint assessment of a propeller driven air vehicle for a specific flight mission and to optimize its trajectory towards low noise. As an exemplary configuration serves the tilt-wing aircraft VAHANA. For this purpose, a simplified two dimensional flight mechanics model is implemented with the help of Python library Dymos. The acoustics are modelled based on a hybrid approach: In a first step, the aerodynamic solver UPM (Unsteady Panel Method) calculates the aerodynamic propeller blade loads. As a second step, the corresponding noise radiation is simulated based on the Ffowcs-Williams and Hawkings equation with the help of the code APSIM. The results serve as acoustic representation of the investigated flight vehicle, enabling the creation of an acoustic database of a flight mission. This database, based on one propeller of VAHANA to limit the computational effort, is further processed with the Ray-Tracing code RayCer returning the noise signature on ground of a trajectory considering atmospheric effects, ground impedance and reflection. After interconnecting the mentioned tools through an interface, they are embedded into the Python open-source optimization framework OpenMDAO. Optimizing the whole flight mission for each point individually of the flight path and returning the corresponding rotation speed setting with respect to low noise, has been possible. Besides, a multi-objective formulation has been derived and could be applied to one point of the trajectory. The modular implementation of this environment facilitates its further development in the future and denotes the first step towards optimized flight procedure design for noise abatement.