scholarly journals BVI-noise generation by wing-shaped helicopter blade

2020 ◽  
Keyword(s):  
Calculated Data ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Noise Generation ◽  
High Frequency Region ◽  
Helicopter Blade ◽  
Sound Fields ◽  
Helicopter Flight ◽  
Natural Forms ◽  
Mach Numbers

Aerodynamic noise includes a number of noise components, among which rotational noise and vortex noise (BVI-noise) make the largest contribution to the overall noise generated. Rotation noise depends on the magnitude of the velocity of the incoming blade and prevails over other noise components at significant Mach Mach numbers. Unlike rotation noise, vortex noise is evident at low helicopter flight speeds, moderate Mach numbers. In the formation of this type of noise,an important role is played by the longitudinal geometry. Therefore, recently the shape of the helicopter blade is chosen close to existing natural forms, which are as balanced as possible. One of these may be a wing-shaped blade. In this work, the problem of generating BVI noise by the wing shaped blade of a helicopter is posed and solved. The mathematical model of the problem is constructed on the previously proposed by the author and successfully tested system of aeroacoustic equations for the general case. Estimated features in this system are pulsations of sound pressure and sound potential. The calculated data of these quantities, as well as their derivatives, were used to study near and far sound fields. In particular, the dependence of the density ripple distribution is revealed from the blade geometry, the angle of attack and the blade angle to the oncoming flow. Increasing flow velocity contributes to the emergence of transverse ripples on the surface blades that dominate the longitudinal ripples by level. An interesting feature noticed in the calculations is that there are calculations for moderate Mach numbers M=0.2,0.3 situations, at certain angles of blade placement to the stream and angles of attack where rotation noise dominates eddy noise. For values Mach numbers M>0.4 rotation noise plays a major role in blade noise generation. The noise level generated is in the range 50dB≤L≤60dB, which is lower by 5-6dB for the Blue Edge blade, as well as the rounded blade. In addition, activation of the high-frequency region in the frequency spectrum of noise was observed f≈840Hz. The results of the calculations show that the blade of the wing-shaped is low-noise in the mode of maneuvers at small flight speeds.

Advanced Numerical Methods for the Prediction of Tonal Noise in Turbomachinery—Part I: Implicit Runge–Kutta Schemes

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Graham Ashcroft ◽  
Christian Frey ◽  
Kathrin Heitkamp ◽  
Christian Weckmüller
Keyword(s):  
Stokes Equations ◽  
Temporal Integration ◽  
Aerodynamic Noise ◽  
Navier Stokes ◽  
Noise Generation ◽  
Academic Problems ◽  
Tonal Noise ◽  
Navier Stokes Equations ◽  
Runge Kutta ◽  
The Stability

This is the first part of a series of two papers on unsteady computational fluid dynamics (CFD) methods for the numerical simulation of aerodynamic noise generation and propagation. In this part, the stability, accuracy, and efficiency of implicit Runge–Kutta schemes for the temporal integration of the compressible Navier–Stokes equations are investigated in the context of a CFD code for turbomachinery applications. Using two model academic problems, the properties of two explicit first stage, singly diagonally implicit Runge–Kutta (ESDIRK) schemes of second- and third-order accuracy are quantified and compared with more conventional second-order multistep methods. Finally, to assess the ESDIRK schemes in the context of an industrially relevant configuration, the schemes are applied to predict the tonal noise generation and transmission in a modern high bypass ratio fan stage and comparisons with the corresponding experimental data are provided.

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.

scholarly journals Aeroacoustics of Silent Owl Flight

2020 ◽  
Vol 52 (1) ◽  
pp. 395-420 ◽  
Author(s):  
Justin W. Jaworski ◽  
N. Peake
Keyword(s):  
Mathematical Modeling ◽  
Noise Reduction ◽  
Current Knowledge ◽  
Foraging Strategies ◽  
Aerodynamic Noise ◽  
Noise Generation ◽  
Reduction Strategies ◽  
Noise Measurements ◽  
Modeling And Experiments ◽  
Review Current

The ability of some species of owl to fly in effective silence is unique among birds and provides a distinct hunting advantage, but it remains a mystery as to exactly what aspects of the owl and its flight are responsible for this dramatic noise reduction. Crucially, this mystery extends to how the flow physics may be leveraged to generate noise-reduction strategies for wider technological application. We review current knowledge of aerodynamic noise from owls, ranging from live owl noise measurements to mathematical modeling and experiments focused on how owls may disrupt the standard routes of noise generation. Specialized adaptations and foraging strategies are not uniform across all owl species: Some species may not have need for silent flight, or their evolutionary adaptations may not be effective for useful noise reduction for certain species. This hypothesis is examined using mathematical models and borne out where possible by noise measurements and morphological observations of owl feathers and wings.

Future Trends in Aircraft Engine Noise Research

1970 ◽  
Author(s):  
Jervis D. Kester
Keyword(s):  
Power Plant ◽  
Aircraft Engine ◽  
Low Noise ◽  
Future Research ◽  
Noise Generation ◽  
Future Trends ◽  
Noise Abatement ◽  
Engine Component ◽  
Bypass Ratio ◽  
Selection Of

The high bypass ratio engines being introduced into service have generally been acknowledged to provide significant improvement in noise abatement. Substanital improvements in future designs will require research into several areas of engine-component noise generation. Low-noise standards also will be influenced by the aircraft mission requirements that affect selection of the power-plant cycle. Each mission requirement presents special noise problems, which must be solved. This paper explores the relationships among aircraft mission requirements, noise research in process at Pratt & Whitney Aircraft, and trends predicted for future research.

Recent Status on Development of the Turbofan Engine in Japan

1974 ◽  
Author(s):  
Masakatsu Matsuki ◽  
Tadao Torisaki ◽  
Kiyoto Miyazawa
Keyword(s):  
Low Noise ◽  
Noise Generation ◽  
Jet Engines ◽  
Smoke Emission ◽  
Turbofan Engine ◽  
Front Fan ◽  
Made In

Efforts to design and develop new jet engines have been made in Japan since 1953. One family of propulsion engine (J3) succeeded in getting into production to be installed on two models of Japanese developed aircraft (T1B and P2J). Another family of lift engine (JR) has been successfully used for overall VTOL system studies. Based upon these experiences, studies on a new fan engine for main propulsion are being carried out. This new engine (FJR-710) is a high bypass front fan engine developed for low noise generation and low smoke emission.

Optimization of Low-Noise and Large Air Volume Blower Based on Load Characteristic

2015 ◽  
Vol 656-657 ◽  
pp. 700-705
Author(s):  
Jian Dong Chen ◽  
Bei Bei Sun
Keyword(s):  
Flow Rate ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Strong Wind ◽  
Centrifugal Fan ◽  
Fan Noise ◽  
Load Characteristic ◽  
Air Volume ◽  
Actual Working ◽  
Working Point

The blower is a kind of garden machinery, which blows strong wind to clean up leaves by a centrifugal fan, but it causes a loud aerodynamic noise. To compromise the contradiction between large air flow rate and low fan noise, some optimizations are proposed to reduce fan noise without lowering its air volume. In this paper, a CFD numerical model to compute airflow field of blower is established, where the centrifugal fan is simulated by the MRF model, and theturbulent model is selected. By smoothing the transition section, improving the volute tongue and optimizing the shape and optimizing number of fan blade, the blower work performance is increased obviously. In order to find out the actual working point, both the fan and motor load characteristic curves are drawn out. The simulation results show that, at the actual working point, the speed of the centrifugal fan is reduced, while the flow rate of blower is raised up. The optimizations are applied to the blower, and the experiment of the improved blower shows the flow rate is increased 5%, and the noise is reduced 2dB.

scholarly journals On the Study of Aerodynamic Noise Measurement of Turbulent Flow Field with a Low-noise Turbulence Generator

2007 ◽  
Vol 73 (732) ◽  
pp. 1629-1636 ◽  
Author(s):  
Akiyoshi IIDA ◽  
Kenji MORITA ◽  
Hiroyuki TANIDA ◽  
Toshitaka MINBU ◽  
Akisato MIZUNO ◽  
...  
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Low Noise ◽  
Noise Measurement ◽  
Aerodynamic Noise ◽  
Turbulent Flow Field ◽  
Turbulence Generator

scholarly journals Prediction and Reduction of Aerodynamic Noise of the Multiblade Centrifugal Fan

2014 ◽  
Vol 6 ◽  
pp. 712421 ◽  
Author(s):  
Shuiqing Zhou ◽  
Jun Wang
Keyword(s):  
Flow Field ◽  
Sound Pressure ◽  
Acoustic Analysis ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Hybrid Technique ◽  
Field Calculation ◽  
Pressure Amplitude ◽  
Centrifugal Fan ◽  
Hybrid Techniques

An aerodynamic and aeroacoustic investigation of the multiblade centrifugal fan is proposed in this paper, and a hybrid technique of combining flow field calculation and acoustic analysis is applied to solve the aeroacoustic problem of multiblade centrifugal fan. The unsteady flow field of the multiblade centrifugal fan is predicted by solving the incompressible Reynolds-averaged Navier-Stokes (RANS) equations with conventional computing techniques for fluid dynamics. The principal noise source induced is extracted from the calculation of the flow field by using acoustic principles, and the modeled sources on inner and outer surfaces of the volute are calculated with multiregional boundary element method (BEM). Through qualitative analysis, the sound pressure amplitude distribution of the multiblade centrifugal fan in near field is given and the sound pressure level (SPL) spectrum diagram of monitoring points in far field is obtained. Based on the analysis results, the volute tongue structure is adjusted and then a low-noise design for the centrifugal fan is proposed. The comparison of noise tests shows the noise reduction of improved fan model is more obvious, which is in good agreement with the prediction using the hybrid techniques.

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