Influence of Roughness Trips on Near- and Far-Field Trailing-Edge Noise

Santos, Fernanda L. dos; Botero-Bolívar, Laura; Venner, Cornelis H.; Santana, Leandro D. de

doi:10.2514/1.j061570

Cited by 10 publications

(1 citation statement)

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“…The surface-flow interactions have considerable impacts on boundary-layer transitions and the generated noise in areal structures [346]. To reveal details of these influences, Volkmer et al [347] published computational and experimental results from three different blade modification methods for noise reduction in a small wind turbine.…”

Section: Surface Treatmentsmentioning

confidence: 99%

Recent Advances in Airfoil Self-Noise Passive Reduction

Amirsalari,

Rocha

2023

Aerospace

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Airflow-induced noise prediction and reduction is one of the priorities for both the energy and aviation industries. This review paper provides valuable insights into flow-induced noise computation, prediction, and optimization methods with state-of-the-art efforts in passive noise reduction on airfoils, blades, and wings. This review covers the combination of several approaches in this field, including analytical, numerical, empirical, semi-empirical, artificial intelligence, and optimization methods. Under passive noise reduction techniques, leading and trailing edge treatments, porous materials, controlled diffusion airfoils, morphing wings, surface treatments, and other unique geometries that researchers developed are among the design modification methods discussed here. This work highlights the benefits of incorporating multiple techniques to achieve the best results concerning the desired application and design. In addition, this work provides an overview of the advantages and disadvantages of each tool, with a particular emphasis on the possible challenges when implementing them. The methods and techniques discussed herein will help increase the acoustic efficiency of aerial structures, making them a beneficial resource for researchers, engineers, and other professionals working in aviation noise reduction.

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Section: Surface Treatmentsmentioning

confidence: 99%

Recent Advances in Airfoil Self-Noise Passive Reduction

Amirsalari,

Rocha

2023

Aerospace

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Study of the development of a boundary layer using the remote microphone probe technique

et al. 2023

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The experimental identification of the transition region and the different flow structures inside the boundary layer is still a challenge. For the first time, this research uses the remote microphone probe technique to experimentally evaluate the boundary layer development, the transition process, and the type of flow structures. The remote microphone probe technique is an effective and accurate experimental method to measure wall-pressure fluctuations. The development of the boundary layer was evaluated under natural and forced transition for different inflow velocities and angles of attack. Results of the wall-pressure spectrum, spanwise coherence at different chord positions, and the spanwise correlation length close to the trailing edge are presented. Furthermore, boundary layer and far-field noise measurements at several conditions are also shown. This paper shows the growth of the turbulent structures that contain most of the turbulent energy along the airfoil chord. Further, it is demonstrated that the spanwise correlation length increases with the inflow velocity. Results for the no forced transition cases form a complete database to determine the different transition stages, which were linked with different components of the wall-pressure spectra. The primary and secondary instability mechanisms leading the transition process appear in the wall-pressure spectrum as peaks and a hump, respectively. The two- and three-dimensional nature of the boundary layer structures is also discussed by analyzing the spanwise coherence. Finally, it is shown that when two-dimensional structures reach the airfoil trailing edge, a feedback loop between the acoustic waves at the airfoil trailing edge and a point upstream in the airfoil surface is generated. This feedback loop influences the wall-pressure fluctuations along the entire airfoil chord. Graphical abstract

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