The Numerical Analysis of Forward Fan Noise Shielding Effect on the Over-the-Wing Nacelle Configuration

2014 ◽  
Author(s):  
Yuma Fukushima ◽  
Takashi Misaka ◽  
Shigeru Obayashi ◽  
Daisuke Sasaki ◽  
Kazuhiro Nakahashi
Keyword(s):  
Numerical Analysis ◽  
Shielding Effect ◽  
Fan Noise ◽  
Noise Shielding

A Numerical Analysis for Cracks Emanating from a Quarter-Spherical Cavity on the Edge of an Elastic Body

2012 ◽  
Vol 499 ◽  
pp. 243-247
Author(s):  
Long Hai Yan ◽  
Bao Liang Liu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Numerical Analysis ◽  
Elastic Body ◽  
Spherical Cavity ◽  
Numerical Results ◽  
Shielding Effect ◽  
Corner Crack ◽  
Element Method

This note is specifically concerned with cracks emanating from a quarter-spherical cavity on the edge in an elastic body (see Fig.1) by using finite element method. The numerical results show that the existence of the cavity has a shielding effect of the corner crack. In addition, it is found that the effect of boundaries parallel to the crack on the SIFs is obvious when.H/R≤3

Numerical Analysis of an Industrial Fan Fitted With Noise Reduction Devices

2006 ◽  
Author(s):  
J. Amaral Teixeira ◽  
E. Naylor ◽  
P. C. Ivey ◽  
A. G. Sheard ◽  
I. R. Kinghorn
Keyword(s):  
Numerical Analysis ◽  
Noise Reduction ◽  
Flow Characteristics ◽  
Pressure Rise ◽  
Broadband Noise ◽  
Noise Sources ◽  
Fan Noise ◽  
Trailing Edge ◽  
Low Speed ◽  
The Individual

The reduction of noise emitted by industrial low speed cooling fans, particularly those fitted to air conditioning systems is a concern to fan manufacturers. The market for industrial low speed fans is highly competitive, with fan noise being the major differentiating factor between competing products. Noise reduction strategies are therefore implemented but these can adversely affect the fan’s pressure delivery capability. A reduction of fan speed can also lead to a reduction in fan noise but this is usually accompanied by a corresponding reduction in pressure rise and flow rate. The practical difficulties associated with maintaining fan pressure and flow characteristics while simultaneously reducing fan noise present fan manufacturers with a challenge. Traditional empirical approaches to the reduction of fan noise have almost been exhausted and no longer offer the potential to significantly reduce fan noise. The understanding of the aerodynamic mechanisms that act as broadband noise sources in low speed fans has been the subject of a considerable number of papers over many years. For most fans operating as a single blade row, the main sources of noise, other than those dependent on the incident turbulence levels, depend on the trailing edge and tip gap flow conditions. A range of strategies seeking to control the noise generated by these regions have been proposed over time by various authors and a number of these schemes have reached production status. The current paper details the numerical analysis of an industrial low speed fan, commonly used in conjunction with a cooling matrix, and which incorporates two distinct noise reduction features; trailing edge crenulations and a blade tip fence. Comparisons are carried out between various combinations of blades, with and without the individual features, and a discussion of the aerodynamics of the particular configurations is undertaken from a perspective of their noise reduction capabilities.

Numerical Analysis of Levitating Force Using Magnetic Shielding Effect of YBCO Plates

2006 ◽  
Vol 16 (2) ◽  
pp. 1096-1099 ◽  
Author(s):  
T. Takao ◽  
A. Niiro ◽  
S. Suzuki ◽  
M. Hashimoto ◽  
J. Takeda ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Shielding Effect ◽  
Magnetic Shielding

Sound radiation from a cylindrical duct. Part 2. Source modelling, nil-shielding directions, and the open-to-ducted transfer function

1996 ◽  
Vol 313 ◽  
pp. 367-380 ◽  
Author(s):  
C. J. Chapman
Keyword(s):  
Transfer Function ◽  
Good Accuracy ◽  
Shielding Effect ◽  
Front Face ◽  
Main Beam ◽  
Mean Flow ◽  
Sound Fields ◽  
Ducted Fan ◽  
Noise Shielding ◽  
Cylindrical Duct

This paper analyses the sound radiated from the front face of a hard-walled circular cylindrical duct in a subsonic mean flow when the duct contains acoustic sources typical of those in a ducted-fan aeroengine. Two main results are established for modes of any given frequency and circumferential order. The first result is that in certain easily calculated directions, called here the nil-shielding directions, the sound radiated by ducted sources is the same as the sound radiated by the corresponding open sources, i.e. by unducted sources of the same distribution and strength radiating into free space. Thus in these special directions the duct has no noise-shielding effect. The second result is that, in the Kirchhoff approximation, the sound radiated by the open sources in the nil-shielding directions determines the sound radiated by the ducted sources in all directions; i.e. the sound fields radiated by open and ducted sources are related by an open-to-ducted transfer function. This function is such that the sound radiated by the ducted sources is a linear combination of certain diffraction functions, in which the coefficients are given by the sound radiated by the open sources in the nil-shielding directions. The diffraction functions do not depend on the sources and are here calculated explicitly in terms of Bessel functions. The method used in the paper is Kirchhoff's approximation; within linear theory this gives the nil-shielding directions exactly, i.e. in agreement with the Wiener—Hopf solution, and gives the main beam of the radiated field, including the major side-lobes, to good accuracy. The results are relevant to the sound radiated into the forward arc by a ducted turbofan aeroengine.

scholarly journals Numerical analysis of fan noise for the NOVA boundary-layer ingestion configuration

2020 ◽  
Vol 96 ◽  
pp. 105532 ◽  
Author(s):  
Gianluca Romani ◽  
Qingqing Ye ◽  
Francesco Avallone ◽  
Daniele Ragni ◽  
Damiano Casalino
Keyword(s):  
Boundary Layer ◽  
Numerical Analysis ◽  
Fan Noise

Fan noise shielding predictions with a coupled DG / FM-BEM for installed aircraft engines

2021 ◽  
Author(s):  
Stanislav Proskurov ◽  
Michael Moessner ◽  
Roland Ewert ◽  
Markus Lummer ◽  
Jan W. Delfs
Keyword(s):  
Aircraft Engines ◽  
Fan Noise ◽  
Noise Shielding

scholarly journals Sound quality assessment of a medium-range aircraft with enhanced fan-noise shielding design

2021 ◽  
Author(s):  
Gil Felix Greco ◽  
Lothar Bertsch ◽  
Tobias P. Ring ◽  
Sabine C. Langer
Keyword(s):  
Quality Assessment ◽  
Quantitative Description ◽  
Aircraft Design ◽  
Sound Quality ◽  
Aircraft Noise ◽  
Design Stage ◽  
Short Term ◽  
Fan Noise ◽  
Medium Range ◽  
Noise Shielding

AbstractThe investigation of technologies that can improve the sustainability of the air transport system requires not only the development of alternative fuel concepts and novel vehicle technologies but also the definition of appropriate assessment strategies. Regarding noise, the assessment should reflect the situation of communities living near airports, i.e., not only addressing sound levels but also accounting for the annoyance caused by aircraft noise. For this purpose, conventional A-weighted sound pressure level metrics provide initial but limited information as the level- and frequency-dependency of the human hearing is accounted for in a simplified manner. Ideally, subjective evaluations are required to adequately quantify the perceived short-term annoyance associated with aircraft noise. However, listening tests are time-consuming and not suitable to be applied during the conceptual aircraft design stage, where a large solution space needs to be explored. Aiming at bridging this gap, this work presents a methodology for the sound quality assessment of computational aircraft noise predictions, which is hereby conducted in terms of objective psychoacoustic metrics. The proposed methodology is applied to a novel medium-range vehicle with fan noise shielding architecture during take-off and landing procedures. The relevance of individual sound sources, i.e., airframe and engine noise contributions, and their dependencies on the aircraft architecture and flight procedures are assessed in terms of loudness, sharpness, and tonality. Moreover, the methodology is steered towards community noise assessment, where the impacts on short-term annoyance brought by the novel aircraft design are analysed. The assessment is based on the modified psychoacoustic annoyance, a metric that provides a quantitative description of human annoyance as a combination of different hearing sensations. The present work is understood as an essential step towards low-annoyance aircraft design.

Sign in / Sign up

Export Citation Format

Share Document