A Study of Noise Generation on the E387, S823, NACA 0012, and NACA 4412 Airfoils for Use on Small-Scale Wind Turbines in the Urban Environment

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Kenneth W. Van Treuren ◽  
Andrew W. Hays
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Reynolds Numbers ◽  
Pressure Level ◽  
Small Scale ◽  
Noise Prediction ◽  
Noise Generation ◽  
Naca 0012

Four airfoils typical to small-scale wind turbines were studied for noise generation: Eppler 387, NREL S823, NACA 0012, and NACA 4412. Wind tunnel sound pressure level (SPL) data were collected directly downstream of the airfoil for angles of attack from −10 deg to 25 deg and for Reynolds numbers from 50,000 to 200,000. Vertical and horizontal wake traverses define the extent of the noise generated. The data were analyzed by frequency and compared with a noise prediction from NREL AirFoil Noise (NAFNoise). The noise trends found can be applied to improve other airfoil selection when designing small-scale wind turbines.

Numerical investigation of aerodynamic and acoustic characteristics of bionic airfoils inspired by bird wing

2018 ◽  
Vol 233 (11) ◽  
pp. 4004-4016 ◽  
Author(s):  
Menghao Wang ◽  
Xiaomin Liu
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Leading Edge ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Small Scale ◽  
Airfoil Surface ◽  
Acoustic Characteristics ◽  
Bionic Coupling ◽  
Bionic Airfoil

Airfoil is the basic element of fluid machinery and aircraft, and the noise generated from that is an important research aspect. Aiming to reduce the aerodynamic noise around the airfoil, this study proposes an airfoil inspired by the long-eared owl wing and another airfoil coupled with the bionic airfoil profile, leading edge waves, and trailing edge serrations. Numerical simulations dependent on the large eddy simulation method coupled with the wall-adapting local eddy-viscosity model and the Ffowcs Williams and Hawkings equation are conducted to compare the aerodynamic and acoustic characteristics of two types of bionic airfoils at low Reynolds number condition. The simulations reveal the dipole characteristic of acoustic source and sound pressure level distribution at various frequencies. Two types of bionic airfoils show lower noise compared with the conventional NACA 0012 airfoil with a similar relative thickness of 12%. Compared with the bionic airfoil, the average value of sound pressure level at the monitoring points around the bionic coupling airfoil is decreased by 9.94 dB, meanwhile the lift-to-drag ratio also keep higher. The bionic coupling airfoil exerts a suppression of sound pressure fluctuation on the airfoil surfaces, which result from that the range and size of separation vortices are reduced and the distance between vortices and airfoil surface are increased. The tube-shaped vortices in the wake of airfoil are effectively restrained and split into small scale vortices, which are important to cause less aerodynamic noise around the bionic coupling airfoil. Consequently, a novel bionic coupling airfoil is developed with the excellent aerodynamic and acoustic performance.

scholarly journals Supersonic Windtunnel Noise Attenuation

2021 ◽  
Author(s):  
William Wai Lim Wong
Keyword(s):  
Wind Tunnel ◽  
Sound Pressure Level ◽  
Noise Level ◽  
Sound Pressure ◽  
Power Level ◽  
Mesh Size ◽  
Acoustic Power ◽  
Pressure Level ◽  
Supersonic Wind Tunnel ◽  
Acoustic Treatment

The aerodynamic generated noise in the supersonic wind tunnel during operation at Ryerson University has exceeded the threshold of hearing damage. An acoustic silencer was to be designed and added to the wind tunnel to reduce the noise level. The main sources of noise generated from the wind tunnel with the silencer were identified to be located at the convergent divergent nozzle and the turbulent region downstream of the shock wave at the diffuser with the maximum acoustic power level of the entire wind tunnel at 161.09 dB. The designed silencer provided an overall sound pressure level reduction of 21.41 db which was considered as acceptable. Refinement to the mesh size and changes to the geometry of the mixing chamber was suggested for a more accurate result in noise output as well as flow conditions would match up to the physical flow. Additional acoustic treatment should be applied to the wind tunnel to further reduce sound pressure level since the noise level still exceeded the threshold of hearing loss.

scholarly journals Validity of Reference Time Intervals in Noise Indicators for Aircraft Noise Policy in Vietnam

Urban Science ◽  
2020 ◽  
Vol 4 (2) ◽  
pp. 19
Author(s):  
Thu Lan Nguyen ◽  
Ichiro Yamada ◽  
Takashi Yano ◽  
Koichi Makino ◽  
Masaharu Ohya
Keyword(s):  
Sound Pressure Level ◽  
Traffic Congestion ◽  
Sound Pressure ◽  
Leisure Activities ◽  
Pressure Level ◽  
Aircraft Noise ◽  
Small Scale ◽  
Time Interval ◽  
Time Intervals ◽  
Reference Time

Many decibel-based noise indicators are used in noise policy to evaluate aircraft sound in the environment. Among those, day–evening–night-weighted sound pressure level ( L den ), day–night-weighted sound pressure level ( L dn ), and nighttime average sound pressure level ( L night ) are the most widely used. However, the designation of reference time intervals (e.g., day, evening, and night) differs depending on the country’s lifestyle and culture. A dataset—extracted from socio-acoustic surveys conducted in Vietnam (2005–2019)—was analyzed to investigate temporal patterns of the Vietnamese lifestyle and changes in L den , L dn , and L night when temporal interval segmentations in these indicators were adjusted. Traffic congestion hours, go-to-bed time, and wake-up time in southern Vietnam were approximately one hour later than those in northern and central Vietnam. Further, a small-scale and Internet-based questionnaire survey on Vietnamese life rhythms was conducted to examine Vietnamese people’s daily behaviors. These data were compared with the relevant data of Japanese individuals, extracted from the Survey on Time Use and Leisure Activities of Japan. Differences in sleeping times and mealtimes were found between Japanese and Vietnamese data. We suggest an appropriate reference time interval for aircraft noise policy in Vietnam, referring to the current national and international noise standards and regulations.

Single-Stream Jet Noise Prediction Using Empirical Methodology for a Newly Designed Turbojet Engine

2013 ◽  
Author(s):  
João Roberto Barbosa ◽  
Daniel Jonas Dezan
Keyword(s):  
Sound Pressure Level ◽  
Performance Prediction ◽  
Gas Turbines ◽  
Sound Pressure ◽  
Jet Noise ◽  
Pressure Level ◽  
High Fidelity ◽  
Noise Prediction ◽  
Single Stream ◽  
Turbojet Engine

The Center for Reference on Gas Turbines (CRTG), at the Technological Institute of Aeronautics, carries out research in relevant areas of gas turbines, to provide the support for teaching and the ability to design high performance gas turbines. Noise prediction, by means of theoretical and empirical methods, is among such areas. Emphasis is given to the prediction of noise from new engines, to anticipate problems at very early design stage and to take the necessary actions to guarantee that the engine noise is below the recommended limits. Noise prediction is part of a high fidelity gas turbine performance prediction computer program, which provides the designer, at any time during the design phases, with information on the noise levels generated by each component and by the engine. This paper presents results obtained with such methodology incorporated to the high fidelity engine performance prediction computer code, and in the format usually used in the literature. The SPL — far-field one-third octave band sound pressure level — and the OASPL — overall sound pressure level — for single-stream jet were calculated for several engine rotational speeds and observer positions. Two methods have been for the single-stream jet noise prediction, namely: ESDU item 98019 and SAE ARP 876D. Nozzle details were taken from a 5 kN turbojet engine, designed at the CRTG, and which is being installed in the test rig for the preliminary evaluation. In this paper the influence of the observer position on the calculated SPL is presented, and the corresponding OASPL for steady engine operation, combined with the effect of the engine rotational speeds on exhaust jet noise. It is shown that they are in agreement with the noise of similar operating conditions. Ground reflection and atmospheric attenuation were not considered in this work. The results indicate that the noise prediction is adequate for use during the design phase and that the model derived in the SAE ARP 876D paper provides better single-stream jet noise prediction than ones predicted using the ESDU Item 98019.

Amplitude modulations increase annoyance due to wind turbine noise immission

2021 ◽  
Vol 263 (2) ◽  
pp. 4048-4057
Author(s):  
Christoph Pörschmann ◽  
Stephan Großarth ◽  
Johannes M. Arend ◽  
Sebastian Schmitter ◽  
Dirk Schreckenberg ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Current Literature ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Pressure Level ◽  
Wind Turbine Noise ◽  
Control Location ◽  
Noise Characteristics ◽  
Study Sites

Current literature suggests that annoyance of wind turbine noise is strongly affected by amplitude modulations (AM). A survey was carried out at five German residential study sites near wind turbines with a total of about 500 residents to study the effects of AM in more detail. Annoyance, disturbances, and the perception of wind turbine noise characteristics, including AM, were assessed. For each participant, address-related exposure to rating levels of wind turbines was estimated. Further, we carried out headphone-based listening experiments with participants from three of the five study areas and with non-exposed participants from another 'control' location. In the listening experiments, perceived annoyance was rated for varying AM and for different A-weighted sound pressure levels for a total number of 79 subjects. As expected, the results show an increase in annoyance with sound pressure level. Furthermore, annoyance increased significantly with the extent of amplitude modulations. Interestingly, annoyance showed a strong rise as soon as amplitude modulations became audible in the signal and this rise was hardly affected by the sound pressure level. In our contribution, we present comparisons of the results of the survey and the listening experiments.

scholarly journals Supersonic Windtunnel Noise Attenuation

2021 ◽  
Author(s):  
William Wai Lim Wong
Keyword(s):  
Wind Tunnel ◽  
Sound Pressure Level ◽  
Noise Level ◽  
Sound Pressure ◽  
Power Level ◽  
Mesh Size ◽  
Acoustic Power ◽  
Pressure Level ◽  
Supersonic Wind Tunnel ◽  
Acoustic Treatment

The aerodynamic generated noise in the supersonic wind tunnel during operation at Ryerson University has exceeded the threshold of hearing damage. An acoustic silencer was to be designed and added to the wind tunnel to reduce the noise level. The main sources of noise generated from the wind tunnel with the silencer were identified to be located at the convergent divergent nozzle and the turbulent region downstream of the shock wave at the diffuser with the maximum acoustic power level of the entire wind tunnel at 161.09 dB. The designed silencer provided an overall sound pressure level reduction of 21.41 db which was considered as acceptable. Refinement to the mesh size and changes to the geometry of the mixing chamber was suggested for a more accurate result in noise output as well as flow conditions would match up to the physical flow. Additional acoustic treatment should be applied to the wind tunnel to further reduce sound pressure level since the noise level still exceeded the threshold of hearing loss.

Scaling Small-Scale Wind Turbines for Wind Tunnel Testing

2012 ◽  
Author(s):  
Timothy A. Burdett ◽  
Kenneth W. Van Treuren
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Wind Turbines ◽  
Reynolds Numbers ◽  
Speed Ratio ◽  
Small Scale ◽  
Wind Tunnel Testing ◽  
Tip Speed Ratio ◽  
Multiple Challenges ◽  
Tunnel Testing

Wind tunnel testing of wind turbines can provide valuable insights into wind turbine performance and provides a simple process to test and improve existing designs. However, the scale of most wind turbines is significantly larger than most existing wind tunnels, thus, the scaling required for testing in a typical wind tunnel presents multiple challenges. When wind turbines are scaled, often only geometric similarity and tip speed ratio matching are employed. Scaling in this manner can result in impractical rotational velocities. For wind tunnel tests that involve Reynolds numbers less than approximately 500,000, Reynolds number matching is necessary. When including Reynolds number matching in the scaling process, keeping rotational velocities realistic becomes even more challenging and preventing impractical freestream velocities becomes difficult. Turbine models of 0.5, 0.4, and 0.3 m diameter, resulting in wind tunnel blockages up to 52.8%, were tested in order to demonstrate scaling using Reynolds number matching and to validate blockage corrections found in the literature. Reynolds numbers over the blades ranged from 20,000 to 150,000 and the tip speed ratio ranged from 3 to 4 at the maximum power point for each wind speed tested.

Acoustically Testing Stock and Modified UAS Propellers in Both the Near and Far Field

2020 ◽  
Author(s):  
Kenneth Van Treuren ◽  
Ricardo Sanchez ◽  
Charles Wisniewski ◽  
Paul Leitch
Keyword(s):  
Wind Tunnel ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Sound Level ◽  
Pressure Level ◽  
Decay Rates ◽  
Urban Setting ◽  
Far Field ◽  
Field Noise ◽  
Noise Signature

Abstract In an urban setting, the sound level of a drone must be acceptable. This paper compares a stock DJI Phantom 2 propeller to a stock propeller modified with a Trailing Edge (TE) notch. The purpose was to determine the extent of the near and far field noise signature of the propellers. Measurements were taken in an anechoic chamber at measurement distances of 1 ft to 24 ft. Upstream of propeller, the sound decay follows the standard decay rate (6 dB decrease for a doubling of the distance) from a location of approximately 4 ft. Downstream the sound decay does not follow standard decay rates until 22 ft. A comparison of the two propellers shows that the TE notch and stock propellers have similar Sound Pressure Level (SPL) values at all distances measured. Traverse measurements downstream of the two propellers in the wind tunnel confirms that the magnitudes of the SPL values are similar after a distance of one foot, however, there does seem to be an influence of the TE notch on the frequency spectrum, shifting frequencies slightly higher. In addition to the single propeller tests, a DJI F550 Flame Wheel hexacopter was used to compare the stock and TE notch propellers. While the hexacopter was overall 20 dBA nosier, no discernable difference in SPL between the two propellers was measured.

Multi-objective design optimization of a high efficiency and low noise blower unit of a car air-conditioner

2019 ◽  
Vol 233 (13) ◽  
pp. 3493-3503 ◽  
Author(s):  
Masaru Kamada ◽  
Koji Shimoyama ◽  
Fumito Sato ◽  
Junya Washiashi ◽  
Yasufumi Konishi
Keyword(s):  
Genetic Algorithm ◽  
Design Optimization ◽  
Sound Pressure Level ◽  
Total Pressure ◽  
Sound Pressure ◽  
Low Noise ◽  
Pressure Level ◽  
Dynamics Simulation ◽  
Noise Prediction ◽  
Air Conditioners

Car air-conditioners consist of a blower unit and a heater unit. A blower unit sends wind to a heater unit, and a heater unit adjusts the temperature inside the vehicle. Blower units of car air-conditioners are required to be smaller, lighter, noiseless, and power-saving. However, it is difficult and expensive to predict the noise directly by computational fluid dynamics simulation. Hereupon, this study employs an indirect noise prediction method based on a noise prediction theory to evaluate noise for blower units inexpensively. This method is investigated through a comparison with actual sound pressure level measurement. Then, using this method, this study moves to design optimization of a blower unit of car air-conditioners. The optimization aims to improve total pressure efficiency and sound pressure level from the current design that has been employed for a real commercial vehicle. This study employs a genetic algorithm to explore global optima in a two-objective problem. The present genetic algorithm is assisted by the Kriging surrogate model to reduce computational cost required for evaluating objective functions. The optimization results indicate that the optimized blower unit involves a multi-blade fan with the high chord-pitch ratio to decrease the loss of total pressure efficiency, which is often induced by the flow separation on the blade and the swirling flow on the meridional plane. In addition, the sound pressure level of blower unit can be reduced by decreasing the local flow velocity on the meridian plane due to a blockage factor. A blower unit, which has a scroll with a large tongue angle, shows high total pressure efficiency because the increase in eddy loss is suppressed at the tongue. They suggest the importance of the matching of multi-blade fan and scroll to achieve the good overall performance of a blower unit.

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