Developments of low-noise contractive nozzle used in acoustic wind-tunnel

Maruta, Yoshiyuki; Minorikawa, Gaku

doi:10.2514/6.1997-1679

Cited by 5 publications

(4 citation statements)

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“…Both ref. [19] and ref. [20] suggested that it is possible to reduce the noise and improve the energy capture efficiency of a blade by controlling the surrounding airflow.…”

Section: A New Technique For Reducing Blade Noisementioning

confidence: 86%

“…Since the distribution of the surrounding airflow can significantly affect the noise radiation of a blade, attempts have been made by scholars to reduce noise by optimising the geometries of the aerofoil to change the surrounding airflow. For example, Maruta et al [19] developed a low-noise contractive nozzle for performing acoustic tests in a wind tunnel. In their study, semi-cones were installed around the nozzle to break up the vortices, thereby reducing the vortex noise.…”

Section: A New Technique For Reducing Blade Noisementioning

confidence: 99%

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A Feasibility Study to Reduce Infrasound Emissions from Existing Wind Turbine Blades Using a Biomimetic Technique

et al. 2021

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Infrasound, i.e., low-frequency noise in the frequency range of 10–200 Hz, produced by rotating wind turbine blades has become a matter of concern because it is harmful to human health. Today, with the rapid increase of wind turbine size, this kind of noise is more worrying than ever. Although much effort has been made to design quiet wind turbine blades, today there is still a lack of effective techniques to reduce infrasound emissions from existing blades. To fill this gap in technology, a biomimetic technique that can be readily applied to reduce infrasound emissions of existing wind turbine blades is studied in this paper using both numerical simulation and experimental testing approaches. The numerical study of the technique is based on the analysis of the sound field distribution near the blade, which is derived by performing both aerodynamic and acoustic simulations of the blade. The experimental study of the technique is based on laboratory tests of two scale models of the blade. Both numerical and experimental studies have shown that the shedding vortices behind the blade can be successfully suppressed by semi-cylindrical rings wrapped on the blade. Consequently, both infrasound and the overall sound pressure level of the noise produced by the blade are significantly reduced. Although the rings fail to show good performance in reducing high-frequency noise, it is not a problem for human health because high-frequency noise is weak and moreover it attenuates rapidly as distance increases. The research also showed that the proposed technique can, not only reduce the infrasound produced by the blade, but can also improve the power coefficient of wind turbines.

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“…Both ref. [19] and ref. [20] suggested that it is possible to reduce the noise and improve the energy capture efficiency of a blade by controlling the surrounding airflow.…”

Section: A New Technique For Reducing Blade Noisementioning

confidence: 86%

Section: A New Technique For Reducing Blade Noisementioning

confidence: 99%

A Feasibility Study to Reduce Infrasound Emissions from Existing Wind Turbine Blades Using a Biomimetic Technique

et al. 2021

View full text Add to dashboard Cite

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“…Commonly used passive control measures include (i) the incorporation of a vortex generator at the jet nozzle [2][3][4]8,9,16,23,49,[51][52][53][54][55], (ii) optimization of the configuration of the collector, which includes shape optimization [4,6,17,21,23,31,49,56,57] and the addition of a breathing gap [4,6,7,14,15,21,58,59], (iii) the introduction of resonant chambers (Helmholtz resonators) connected to the plenum or the wind tunnel circuits [31,55,60], and (iv) modifying the wind tunnel circuits [9,11,19].…”

Section: Suppression Methods For Low-frequency Pressure Fluctuationmentioning

confidence: 99%

“…The incorporation of various vortex generators at the nozzle of an open-jet wind tunnel is a widely used passive control method for mitigating low-frequency pressure fluctuations [3,16,23,49,[51][52][53]61].…”

Section: Vortex Generatorsmentioning

confidence: 99%

Review of Mechanisms and Suppression Methods for Low-Frequency Pressure Fluctuations in Open-Jet Wind Tunnels

Jin,

Deng,

Wang

et al. 2023

Applied Sciences

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Low-frequency pressure fluctuations are common in open-jet wind tunnels, affecting test accuracy and posing safety risks to the wind tunnels. These oscillations can be caused by different mechanisms in different wind tunnels, and it is often necessary to identify the specific mechanism responsible for the oscillation and develop appropriate control methods. This paper presents a comprehensive review of the current state of research on low-frequency pressure fluctuations in subsonic open-jet wind tunnels, with a particular emphasis on their generation mechanisms and control strategies. The primary source of excitation is attributed to the edgetone feedback formed by the impingement of the jet on the collector. The sound wavelength corresponding to the edgetone frequency is close to that of the plenum scale, facilitating resonance with both plenum-associated vibration modes and specific-order standing wave modes within the circuit loop, resulting in significant low-frequency pulsations. Passive control methods such as nozzle vortex generators and collector breathing gaps have been extensively employed due to their cost-effectiveness and efficiency. The concluding section highlights some unresolved issues that require further investigation in this field.

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Design and characterization of a multifunctional low-speed anechoic wind tunnel at HKUST

Zhou

Fang

et al. 2021

Aerospace Science and Technology

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Developments of low-noise contractive nozzle used in acoustic wind-tunnel

Cited by 5 publications

References 0 publications

A Feasibility Study to Reduce Infrasound Emissions from Existing Wind Turbine Blades Using a Biomimetic Technique

A Feasibility Study to Reduce Infrasound Emissions from Existing Wind Turbine Blades Using a Biomimetic Technique

Review of Mechanisms and Suppression Methods for Low-Frequency Pressure Fluctuations in Open-Jet Wind Tunnels

Design and characterization of a multifunctional low-speed anechoic wind tunnel at HKUST

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