Sound generated in the vicinity of the trailing edge of an upper surface blown flap

Tam, Christopher K. W.; Reddy, N. M.

doi:10.1016/0022-460x(77)90641-1

Cited by 7 publications

(5 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ref. [15]) and give equivalent predictions of trailing edge noise. The effect of trailing edge thickness and rounding was theoretically explored in a more modern review by Howe, 16 where the influence of "upwash" was found to be important.…”

Section: Introductionmentioning

confidence: 95%

A Review of Airfoil Trailing Edge Noise with Some Implications for Wind Turbines

Doolan

Moreau

2015

International Journal of Aeroacoustics

View full text Add to dashboard Cite

As trailing edge noise is the major aerodynamic noise source on a wind turbine, it is timely and relevant to review previous work in this area. This paper presents a review of previous experimental trailing edge noise studies and compares available experimental noise data for the NACA 0012 profile with data from two numerical studies. The literature review and comparison reveal the extent of the data available, the scatter in the results and some of the ideas about the cause of the scatter. Noise data compare well at laboratory scale Reynolds numbers; however, at higher Reynolds numbers that are comparable to large wind turbines, there is not much agreement and the published data are limited. Resolution of the peak radiating frequency and level must be improved in order to improve the accuracy of wind turbine noise predictions. To do so requires new experimental and computational research to understand the noise generating physics in better detail. * 812 A review of airfoil trailing edge noise with some implications for wind turbines

show abstract

Section: Introductionmentioning

confidence: 95%

A Review of Airfoil Trailing Edge Noise with Some Implications for Wind Turbines

Doolan

Moreau

2015

International Journal of Aeroacoustics

View full text Add to dashboard Cite

show abstract

“…Several aerofoil tonal noise studies have previously evidenced the existence of a feedback loop (see Arcondoulis et al (2013), Pröbsting (2015), Arcondoulis, Liu & Xu (2019) and Yakhina (2017), for instance). Tam & Reddy (1977) were the first to pitch the idea of a feedback loop between acoustic sources in the wake and upstream boundary-layer disturbances. In contrast, Arbey & Bataille (1983) reasoned that the acoustic disturbance generated at the trailing edge instead is responsible for the feedback loop.…”

Section: Introductionmentioning

confidence: 99%

“…The type of boundary-layer instability that generates aerofoil tones has been a source of controversy in the past. Tam & Reddy (1977), for example, had conjectured a Tollmien-Schlichting (TS) flow instability to be responsible for the emission of aerofoil tones. The TS waves are the first stages of flow transition from the laminar to the turbulent boundary layer.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of aerofoil tonal noise at low Mach number

et al. 2021

View full text Add to dashboard Cite

This paper presents an experimental investigation of aerofoil tones emitted by a controlled-diffusion aerofoil at low Mach number ( $0.05$ ), moderate Reynolds number based on the chord length ( $1.4 \times 10^{5}$ ) and moderate incidence ( $5^{\circ }$ angle of attack). Wall-pressure measurements have been performed along the suction side of the aerofoil to reveal the acoustic source mechanisms. In particular, a feedback loop is found to extend from the aerofoil trailing edge to the regions near the leading edge where the flow encounters a mean favourable pressure gradient, and consists of acoustic disturbances travelling upstream. Simultaneous wall-pressure, velocity and far-field acoustic measurements have been performed to identify the boundary-layer instability responsible for tonal noise generation. Causality correlation between far-field acoustic pressure and wall-normal velocity fluctuations has been performed, which reveals the presence of a Kelvin–Helmholtz-type modal shape within the velocity disturbance field. Tomographic particle image velocimetry measurements have been performed to understand the three-dimensional aspects of this flow instability. These measurements confirm the presence of large two-dimensional rollers that undergo three-dimensional breakdown just upstream of the trailing edge. Finally, modal decomposition of the flow has been carried out using proper orthogonal decomposition, which demonstrates that the normal modes are responsible for aerofoil tonal noise. The higher normal modes are found to undergo regular modulations in the spanwise direction. Based on the observed modal shape, an explanation of aerofoil tonal noise amplitude reduction is given, which has been previously reported in modular or serrated trailing-edge aerofoils.

show abstract

“…Starting in the early 1970s, Chris started making pioneering advances in the field of aeroacoustics. Before we broach jet noise, it is worthwhile to highlight his research on several other problems: the generation of discrete tones by an airfoil, 8 boundary layer noise, 9 trailing edge noise, 10,11 cavity noise, 12 laminar wakes, excitation of instability waves by sound, 13 excitation of Tollmien-Schlichting waves by sound, 14 helicopter impulsive noise, 15 propellor noise, 16,17 and other topics. As seen, his earliest research and publications were mostly carried out by himself, and covered diverse topics.…”

Section: Aeroacoustics Researchmentioning

confidence: 99%

Christopher Tam: Brief history and accomplishments

Viswanathan,

2024

International Journal of Aeroacoustics

View full text Add to dashboard Cite

This introduction provides a brief personal background and highlights the scientific accomplishments of Professor Christopher Tam. He has maintained extremely high standards of research and an enviable track record for productivity, spanning more than five decades. The depth and breadth of his technical output are truly breathtaking, and he has inspired scores of researchers and graduate students. When the first author was an Acoustics Engineer at Lockheed, Georgia, he started collaborating with Chris in the early 1990s. There were several joint projects when the author moved to Boeing, which encompassed both fundamental research and applications. The second author has an even longer association with Chris, initially as a PhD advisee in the late 1980s and then as a co-researcher. In this special volume we pay tribute to Chris’s many achievements, an endeavor that provides us with great satisfaction and which is long overdue.

show abstract

Sound generated in the vicinity of the trailing edge of an upper surface blown flap

Cited by 7 publications

References 23 publications

A Review of Airfoil Trailing Edge Noise with Some Implications for Wind Turbines

A Review of Airfoil Trailing Edge Noise with Some Implications for Wind Turbines

Experimental investigation of aerofoil tonal noise at low Mach number

Christopher Tam: Brief history and accomplishments

Contact Info

Product

Resources

About