On a Coupled Aerodynamic and Aeroacoustic Shape Optimization Framework for a 2D Airfoil

Abstract

In recent years, aircraft noise has emerged as a pressing concern within aeronautics, due to its adverse health impacts and the increasing annoyance experienced by affected populations. Factors such as rapid urbanization, urban encroachment resulting in closer proximity of residential areas to airports, and the continuous growth of air traffic have exacerbated this issue. Current approaches to mitigate aircraft noise primarily focus on integrating additional components rather than optimizing the airfoil profile a priori.

This thesis aims to actively address this challenge by developing a coupled aerodynamic and aeroacoustic shape optimization framework tailored for a 2D airfoil. The primary objective is to minimize trailing edge noise, identified as one of the dominant noise generating mechanisms during approach and landing, while simultaneously maximizing aerodynamic performance. The solving strategy combines an aerodynamic solver with a state-of-the-art wall pressure spectrum model and Amiet’s trailing edge noise (TEN) model, whose inputs are boundary layer parameters extracted from the aerodynamic evaluation.

The efficacy of both lower fidelity (XFOIL) and higher fidelity (Reynolds-Averaged Navier Stokes (RANS)) aerodynamic solvers is evaluated. The airfoil is optimized at different points of the flight envelope: for maximum lift-to-drag ratio during cruise and for minimum trailing edge noise during landing.

Results demonstrate that the genetic algorithm (NSGA-II) optimization framework yields promising airfoil shapes and reliable outcomes at a computationally feasible cost. Many optimizations with varying generations and population sizes are ran: remarkably, the results consistently showcase well-defined Pareto fronts, with superior definition observed particularly at a population size of 200.

The lower fidelity solver proves particularly effective in the landing scenario, while it shows limitations for higher Mach numbers. In this view, the RANS code is necessary for capturing flow phenomena at cruise speeds, and notably, it also provides convincing results in terms of aeroacoustic prediction during landing phase.

In general, this research highlights the potential for significant advancements in designing optimal airfoils for aerodynamic performance and TEN.