EXPERIMENTAL INVESTIGATION OF TURBULENCE EFFECTS ON AERODYNAMICS NOISE OF CHANNELED NACA 0012 AIRFOIL

2021 ◽  
pp. 1-6
Author(s):  
Hussein Mohammad ◽  
Latif Ibraheem ◽  
Viktor Kilchyk ◽  
S. O. Bade Shrestha
Keyword(s):  
Wind Turbines ◽  
Low Frequency ◽  
Clean Energy ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Continuous Exposure ◽  
Residential Housing ◽  
Technology Advancement ◽  
Turbulence Effects ◽  
Noise Measurements

Abstract Wind power is rapidly growing worldwide as a renewable and clean energy of choice due to its competitiveness in cost and technology advancement. However, as the wind turbines grow, the aerodynamic noise generated from the rotating blades is becoming a major concern that limits the use of wind turbines, especially near residential housing areas. A significant low sleep quality has been reported within 2km of wind turbines locations that is becoming a problem for wider use of wind energy. [1]. Generally, continuous exposure to 85-90 dBA noise causes permanent hearing loss to human [2]. To reduce the aerodynamic noise, channeled blades were implemented in this work to damp the airflow turbulence that causes the aerodynamic noise. Samples of different diameter sizes and angle of inclinations with respect to the cord have been tested and compared to a regular unchanneled blade. Noise measurements have been carried out using low-frequency microphones with frequencies ranging between 0-10000 Hz. While turbulence measurements were performed using a hot-wire anemometer. The measured noise around the blades ranged between 20-70 dB up to 600 Hz has proven to be directly related to turbulence intensity. The best low noise blade design was recommended based on noise measurement.

Optimized Small Vertical Axis Wind Turbine (VAWT), Phase I

2021 ◽  
Author(s):  
Moshe Zilberman ◽  
Abdelaziz Abu Sbaih ◽  
Ibrahim Hadad
Keyword(s):  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Cost Effective ◽  
Clean Energy ◽  
Vertical Axis ◽  
Low Noise ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Different Types

Abstract Wind energy has become an important resource for the growing demand for clean energy. In 2020 wind energy provided more than 6% of the global electricity demand. It is expected to reach 7% at the end of 2021. The installation growth rate of small wind turbines, though, is relatively slow. The reasons we are interested in the small vertical axis wind turbines are their low noise, environmentally friendly, low installation cost, and capable of being rooftop-mounted. The main goal of the present study is an optimization process towards achieving the optimal cost-effective vertical wind turbine. Thirty wind turbine models were tested under the same conditions in an Azrieli 30 × 30 × 90 cm low-speed wind tunnel at 107,000 Reynolds number. The different types of models were obtained by parametric variations of five basic models, maintaining the same aspect ratio but varying the number of bucket phases, the orientation angles, and the gaps between the vanes. The best performing turbine model was made of one phase with two vanes of non-symmetric bipolynomial profiles that exhibited 0.2 power coefficient, relative to 0.16 and 0.13 that were obtained for symmetrical polynomial and the original Savonius type turbines, respectively. Free rotation, static forces and moments, and dynamic moments and power were measured for the sake of comparison and explanation for the variations in performances of different types of turbines. CFD calculations were used to understand the forces and moment behaviors of the optimized turbine.

scholarly journals A Low-Noise and Quasi-Ideal DC Current Source Dedicated to Four-Probe Low-Frequency Noise Measurements

2020 ◽  
Vol 69 (1) ◽  
pp. 194-200 ◽  
Author(s):  
Jean-Marc Routoure ◽  
Sheng Wu ◽  
Carlo Barone ◽  
Laurence Mechin ◽  
Bruno Guillet
Keyword(s):  
Current Source ◽  
Low Frequency ◽  
Low Noise ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Noise Measurements ◽  
Dc Current

Prediction of Aerodynamic Noise Radiated From a Vertical-Axis Wind Turbine

2003 ◽  
Author(s):  
Akiyoshi Iida ◽  
Akisato Mizuno ◽  
Kyoji Kamemoto
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Sound Source ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine

Unsteady flow field and flow induced noise of vertical axis wind turbine are numerically investigated. The flow field is numerically calculated by the vortex method with core-spreading model. This simulation obtains aerodynamic performance and aerodynamic forces. Aerodynamic noise is also simulated by using Ffowcs Williams-Hawkings equation with compact body and low-Mach number assumptions. Tip speed of rotor blades are not so high, then the contribution of the moving sound source is smaller than that of the dipole sound source. Since the maximum power coefficient of VAWT can be obtained at lower tip-speed ratio compared to the conventional, horizontal axis wind turbines, the aerodynamic noise from vertical axis wind turbine is smaller than that of the conventional wind turbines at the same aerodynamic performance. This result indicates that the vertical axis wind turbines are useful to develop low-noise wind turbines.

scholarly journals Single JFET Front-End Amplifier for Low Frequency Noise Measurements with Cross Correlation-Based Gain Calibration

Electronics ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1197
Author(s):  
Graziella Scandurra ◽  
Gino Giusi ◽  
Carmine Ciofi
Keyword(s):  
Background Noise ◽  
Cross Correlation ◽  
Low Frequency ◽  
Open Loop ◽  
Low Noise ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Front End ◽  
Voltage Amplifier ◽  
Noise Measurements

We propose an open loop voltage amplifier topology based on a single JFET front-end for the realization of very low noise voltage amplifiers to be used in the field of low frequency noise measurements. With respect to amplifiers based on differential input stages, a single transistor stage has, among others, the advantage of a lower background noise. Unfortunately, an open loop approach, while simplifying the realization, has the disadvantage that because of the dispersions in the characteristics of the active device, it cannot ensure that a well-defined gain be obtained by design. To address this issue, we propose to add two simple operational amplifier-based auxiliary amplifiers with known gain as part of the measurement chain and employ cross correlation for the calibration of the gain of the main amplifier. With proper data elaboration, gain calibration and actual measurements can be carried out at the same time. By using the approach we propose, we have been able to design a low noise amplifier relying on a simplified hardware and with background noise as low as 6 nV/√Hz at 200 mHz, 1.7 nV/√Hz at 1 Hz, 0.7 nV/√Hz at 10 Hz, and less than 0.6 nV/√Hz at frequencies above 100 Hz.

Effects of low-frequency noise from wind turbines on heart rate variability in healthy individuals

2021 ◽  
Author(s):  
Chun-Hsiang Chiu ◽  
Shih-Chun Candice Lung ◽  
Nathan Chen ◽  
Jing-Shiang Hwang
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Wind Turbines ◽  
Mixed Model ◽  
Low Frequency ◽  
Clean Energy ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Residential Areas ◽  
Worst Case

Abstract Background: Wind power has been applied around the world as a source of clean energy. However, wind turbines generate low-frequency noise (LFN, 20-200 Hz), which poses health risks to nearby residents. This study aimed to assess heart rate variability (HRV) response to LFN exposure and to evaluate the LFN exposure (dB, LAeq) inside households located near wind turbines. Methods: Thirty subjects living within a 500 m radius of wind turbines were recruited. The field campaigns for LFN (LAeq) and HRV monitoring were carried out in July and December 2018. A generalized additive mixed model was employed to evaluate the relationship between HRV changes and LFN. Results: The results suggested that the standard deviations of all normal to normal R-R intervals reduced significantly by 3.39% with a 95% CI = (0.15%, 6.52%) per 7.86 dB (LAeq) of LFN in the exposure range of 38.2-57.1 dB (LAeq)—i.e., a 0.43% reduction per 1 dB (LAeq). The results of household monitoring showed that the indoor LFN exposure (LAeq) ranged between 30.7 and 43.4 dB (LAeq) at a distance of 124-330 m from wind turbines. The worst case had 99.6%, 89.1%, and 96.8% at daytime, evening, and nighttime, respectively, exceeding the LFN standards of the Taiwan Environmental Protection Administration. Moreover, households built with concrete and equipped with airtight windows showed the highest LFN difference of 13.7 dB between indoors and outdoors. Conclusion: This work is the first study assessing the HRV impacts from turbine LFN in Asia, where wind turbines installed within short distances from residential areas. In view of the adverse health impacts of LFN exposure, there should be regulations on the requisite distances of wind turbines from residential communities for health protection.

DEDICATED INSTRUMENTATION FOR HIGH SENSITIVITY, LOW FREQUENCY NOISE MEASUREMENT SYSTEMS

2004 ◽  
Vol 04 (02) ◽  
pp. L385-L402 ◽  
Author(s):  
C. CIOFI ◽  
G. GIUSI ◽  
G. SCANDURRA ◽  
B. NERI
Keyword(s):  
Background Noise ◽  
Flicker Noise ◽  
Low Frequency ◽  
High Sensitivity ◽  
Design Guidelines ◽  
Low Noise ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Low Frequencies ◽  
Noise Measurements

Low Frequency Noise Measurements (LFNM) can be used as very sensitive tool for the characterization of the quality and the reliability of electron devices. However, especially in those cases in which the frequency range of interest extends below 1 Hz, instrumentation with an acceptable low level of background noise is not easily found on the market. In fact, at very low frequencies, the flicker noise introduced by the electronic components which make up the instrumentation becomes predominant and several interesting phenomena which could be detected by means of LFNM may result completely hidden in the background noise. This consideration is not limited to the case of input preamplifiers but does extend to any piece of instrumentation that contributes to the LFNM systems, and in particular to the power supplies used for biasing the Device Under Test. During the last few years, our research groups have been strongly involved in the design of very low noise instrumentation for application in the field of LFNM. In this work we report the main results which we have obtained together with a discussion of the design guidelines that have allowed us, in a few cases, to reach noise levels not to be equalled by any instrumentation available on the market.

scholarly journals Differential ultra low noise amplifier for low frequency noise measurements

AIP Advances ◽  
2011 ◽  
Vol 1 (2) ◽  
pp. 022144 ◽  
Author(s):  
Graziella Scandurra ◽  
Gianluca Cannatà ◽  
Carmine Ciofi
Keyword(s):  
Low Frequency ◽  
Low Noise ◽  
Low Noise Amplifier ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Noise Measurements ◽  
Noise Amplifier ◽  
Ultra Low Noise
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