Assessing and improving trailing-edge noise reduction technologies for industrial wind-turbine applications

Nowadays, large wind turbines are installed and operated close to densely populated areas due to the growing need for renewable energy. Noise constraints are hampering this development. The most relevant wind turbine noise source is the so-called Turbulent Boundary Layer Trailing-Edge (TBL–TE) noise. Many passive TBL–TE noise reduction...

Aero-acoustic response of an acoustic liner

In this thesis, the resistance of a single degree of freedom liner is investigated experimentally. Semi-empirical resistance modelling fails at higher Mach numbers (M₀>0.3) and sound pressure levels (SPL>130dB), and experimental work is missing in these conditions. An experiment combining in-situ impedance measurements and phase...

Role of polymeric coating on metallic foams to control the aeroacoustic noise reduction of airfoils with permeable trailing edges

Studies on porous trailing edges, manufactured with open-cell Ni-Cr-Al foams with sub-millimeter pore sizes, have shown encouraging results for the mitigation of turbulent boundary-layer trailing-edge noise. However, the achieved noise mitigation is typically dependent upon the pore geometry, which is fixed after manufacturing. In this study,...

Evaluation of the Potential Radar Cross-Section & Experimental Aero-Acoustic Noise Merits of the GA-ASI MQ-9 Reaper by Applying Flap Morphing

Defence institutions and military aircraft manufacturers are increasingly exploring the ways to im- prove stealth in new aircraft designs. Design for low observability, more specifically for low Radar Cross-Section is the fundamental design aspect during design of a new military aerial vehicle. Acoustic stealth is also an important...

On the Estimation of Spanwise Pressure Coherence of a Turbulent Boundary Layer over a Flat Plate

A Large Eddy Simulation (LES) with four different closure models are analyzed in OpenFOAM, an open source Computional Fluid Dynamics (CFD) package and validated for the determination of the streamwise and spanwise coherence length of the pressure field below a turbulent boundary layer at low Reynolds numbers. Matching results are found for outer...

Prediction of flow-induced noise using the expansion about incompressible flow approach

In the present paper an Expansion about Incompressible Flow approach, as suggested by Shen and Sørensen1, will be used and discussed for the simulation of flow-induced sound at low Mach numbers. The method consists of two parts: First solving for the incompressible, viscous flow field, and second computing the fluctuating acoustic field. As a...

Evaluation of aerodynamic noise generation: Parameter study of a generic side miror evaluating the aeroacoustic source strength

Based on a simple generic side mirror geometry, well featured with detailed measurements, we examine different combinations of meshing strategies and turbulence model, nameley DES (Detached Eddy Simulation) and SAS (Scale Adaptive Simulation). The best combination of this investigation is applied to some modified mirror geometries, in order to...