scholarly journals Numerical Investigation of a Rectangular Jet Exhausting over a Flat Plate with Periodic Surface Deformations at the Trailing Edge

Aerospace ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 314
Author(s):  
Colby Niles Horner ◽  
Adrian Sescu ◽  
Mohammed Afsar ◽  
Eric Collins
Keyword(s):  
Flat Plate ◽  
Experimental Studies ◽  
Wing Surface ◽  
Wave Number ◽  
Noise Levels ◽  
Trailing Edge ◽  
Vehicle Performance ◽  
Rectangular Jet ◽  
Sound Levels ◽  
Jet Interactions

Multiple competing factors are forcing aircraft designers to reconsider the underwing engine pod configuration typically seen on most modern commercial aircraft. One notable concern is increasing environmental regulations on noise emitted by aircraft. In an attempt to satisfy these constraints while maintaining or improving vehicle performance, engineers have been experimenting with some innovative aircraft designs which place the engines above the wings or embedded in the fuselage. In one configuration, a blended wing concept vehicle utilizes rectangular jet exhaust ports exiting from above the wing ahead of the trailing edge. While intuitively one would think that this design would reduce the noise levels transmitted to the ground due to the shielding provided by the wing, experimental studies have shown that this design can actually increase noise levels due to interactions of the jet exhaust with the aft wing surface and flat trailing edge. In this work, we take another look at this rectangular exhaust port configuration with some notional modifications to the geometry of the trailing edge to determine if the emitted noise levels due to jet interactions can be reduced with respect to a baseline configuration. We consider various horizontal and vertical offsets of the jet exit with respect to a flat plate standing in for the aft wing surface. We then introduce a series of sinusoidal deformations to the trailing edge of the plate of varying amplitude and wave number. Our results show that the emitted sound levels due to the jet–surface interactions can be significantly altered by the proposed geometry modifications. While sound levels remained fairly consistent over many configurations, there were some that showed both increased and decreased sound levels in specific directions. We present results here for the simulated configurations which showed the greatest decrease in overall sound levels with respect to the baseline. These results provide strong indications that such geometry modifications can potentially be tailored to optimize for further reductions in sound levels.

An experimental investigation of resonant interaction of a rectangular jet with a flat plate

2015 ◽  
Vol 779 ◽  
pp. 751-775 ◽  
Author(s):  
K. B. M. Q. Zaman ◽  
A. F. Fagan ◽  
J. E. Bridges ◽  
C. A. Brown
Keyword(s):  
Mach Number ◽  
Flat Plate ◽  
Cross Section ◽  
Leading Edge ◽  
Resonant Interaction ◽  
Trailing Edge ◽  
Resonant Condition ◽  
Direction Parallel ◽  
Rectangular Jet ◽  
Axis Switching

The interaction between an 8:1 aspect ratio rectangular jet and a flat plate, placed parallel to the jet, is addressed in this study. At high subsonic conditions and for certain relative locations of the plate, a resonance takes place with accompanying audible tones. Even when the tone is not audible the sound pressure level spectra are often marked by conspicuous peaks. The frequencies of these peaks, as functions of the plate’s length, its location relative to the jet as well as jet Mach number, are studied in an effort to understand the flow mechanism. It is demonstrated that the tones are not due to a simple feedback between the nozzle exit and the plate’s trailing edge; the leading edge also comes into play in determining the frequency. With parametric variation, it is found that there is an order in the most energetic spectral peaks; their frequencies cluster in distinct bands. The lowest frequency band is explained by an acoustic feedback involving diffraction at the plate’s leading edge. Under the resonant condition, a periodic flapping motion of the jet column is seen when viewed in a direction parallel to the plate. Phase-averaged Mach number data on a cross-stream plane near the plate’s trailing edge illustrate that the jet cross-section goes through large contortions within the period of the tone. Farther downstream a clear ‘axis switching’ takes place for the time-averaged cross-section of the jet that does not occur otherwise for a non-resonant condition.

scholarly journals 303 What goes bump in the night? A literature review and noise exposure experiment in a UK paediatric emergency department

2020 ◽  
Vol 37 (12) ◽  
pp. 841.1-841
Author(s):  
Lucy Hall ◽  
Sophie Dando ◽  
Anthony Hanks
Keyword(s):  
Emergency Department ◽  
Literature Review ◽  
Literature Search ◽  
Noise Exposure ◽  
Cochrane Library ◽  
Noise Levels ◽  
Paediatric Emergency Department ◽  
Paediatric Emergency ◽  
Sound Levels ◽  
Exposure Experiment

Aims/Objectives/BackgroundIn the Emergency department (ED), noise is a frequent and often unavoidable consequence of work undertaken and levels can often be raised during the day and night. Raised ambient noise levels have potential implications for the workforce, patients and relatives.Investigation into the problem of noise levels in the ED follows feedback from a young patient who couldn’t sleep during a prolonged stay. His complaint focused on loud, irregular banging noises such as those from closing bins that kept him awake.The team felt work should be done to see if it was a wider spread problem or just isolated to his case. A simple sound recording experiment and literature search was conducted.Methods/DesignThe literature search was conducted using electronic/online databases (Medline; Cochrane library) with a fixed date range and specific inclusion criteria.The noise exposure experiment was conducted using a verified phone app to record the sound levels. They were measured at 3 times, during a night shift, in the paediatric emergency department of UHW. All measurements were at a fixed distance and were averaged and compared with WHO recommendations.Results/ConclusionsThere are many sources of noise pollution in the ED, some are unavoidable for safety and clinical reasons.The literature review produced a small number of papers all of which found that sound levels were raised above recommended levels. Similarly, all the sounds measured in the ED also exceeded the recommendations.The most consistent finding across the papers, matched by findings from recordings, was that human behavioural modification is an easy and effective way to reduce noise levels.There are simple steps that can be taken to reduce and eliminate soundsRaising awareness regarding this problem is of great importance and focussing future work on assessing the impact in younger patients within the Emergency Department is paramount.

On the flow near the trailing edge of a flat plate II

Mathematika ◽  
1969 ◽  
Vol 16 (1) ◽  
pp. 106-121 ◽  
Author(s):  
K. Stewartson
Keyword(s):  
Flat Plate ◽  
Trailing Edge

Incubator Noise

PEDIATRICS ◽  
1975 ◽  
Vol 56 (4) ◽  
pp. 617-617
Author(s):  
Gōsta Blennow ◽  
Nils W. Svenningsen ◽  
Bengt Almquist
Keyword(s):  
Low Frequency ◽  
Sound Level ◽  
Noise Levels ◽  
Frequency Sound ◽  
Mechanical Noise ◽  
Sound Levels ◽  
Infant Incubator ◽  
Improved Model ◽  
Model C

Recently we reported results from studies of incubator noise levels.1 It was found that in certain types of incubators the noise was considerable, and attention was called to the sound level in the construction of new incubators. Recently we had the opportunity to study an improved model of Isolette Infant Incubator Model C-86 where the mechanical noise from the electrically powered motor has been partially eliminated. With this modification it has been possible to lower the low-frequency sound levels to a certain degree in comparison to the levels registered in our study.

Station facilities and noise assessment: A multilevel analysis on light rail train stations

2021 ◽  
Vol 69 (4) ◽  
pp. 364-372
Author(s):  
Yalcin Yildirim ◽  
Diane Jones Allen
Keyword(s):  
Public Transportation ◽  
Transportation Systems ◽  
Urban Life ◽  
Light Rail ◽  
Noise Levels ◽  
Transit Systems ◽  
Message Boards ◽  
Sound Levels ◽  
Noise Assessment ◽  
Ticket Vending Machines

Noise is one of the most frequent consequences of traffic. Public transportation systems, such as the Dallas Area Rapid Transit (DART) authority provides various modes of transportation. Even though the availability of commuting service for the public is a boon to communities, mass transit systems are potential sources of excessive sound levels in daily urban life. This article examines the nexus between the transit station facilities of light rail train (LRT) stations and noise implications at both station and neighborhood scales by studying selected LRT stations. A multilevel linear analysis was conducted to understand the degree of train station amenities and neighborhood characteristics that affect sound levels. Using a type II sound pressure level (SPL)meter, sound measurements were obtained during the weekdays and weekends over several weeks. Upon examining the station amenities, and built environment and sociodemographic characteristics of the neighborhood, findings of this comprehensive research reveal significant implications for sound levels. Stations with ticket vending machines and informative message boards include a higher degree of significance on SPLs, while shelters, crew rooms, bike lockers, restrooms, and windshields are significantly and negatively associated with the noise levels. Additionally, neighborhoods with dense roads, higher speed limits, more neighborhood facilities, and a higher number of transit routes have an increased likelihood of noise levels. Recommendations include creating transformative policies for implementation, and approaches addressing noise for transit authorities, transportation engineers, and planners are presented. Planning and engineering aspects of comfort, aesthetics, safety, and public health, as train stations are daily use spaces for commuters and surrounding communities, should also be considered.

scholarly journals RESEARCH AND EVALUATION OF KART NOISE SPREAD INTO THE LIVING ENVIRONMENT / GOKARTŲ KELIAMO TRIUKŠMO SKLAIDOS Į GYVENAMĄJĄ APLINKĄ TYRIMAI IR VERTINIMAS

2014 ◽  
Vol 6 (4) ◽  
pp. 356-361
Author(s):  
Giedrius Juozaponis ◽  
Raimondas Grubliauskas
Keyword(s):  
Wind Speed ◽  
Experimental Studies ◽  
Soil Surface ◽  
Sound Level ◽  
Living Environment ◽  
Noise Levels ◽  
Noise Propagation ◽  
Soil Surface Temperature ◽  
Service Data ◽  
Living Area

The paper examines kart noise propagation in the living environment and sought measures for suppressing it. To conduct experimental studies, precision sound level analyzer Bruel & Kjaer 2260th has been used. In cooperation with the Lithuanian Hydrometeorological Service, data on relative humidity, wind speed and direction, soil surface temperature and air temperature have been applied. According to the Lithuanian Hygiene Standard HN 33:2011 Noise Thresholds in Residential and Public Buildings and Their Environment, the areas with an elevated noise level are identified thus selecting noise reduction measures aimed at reducing noise levels up to the permitted ones. The analysis of the obtained results has focused on the regularities between noise propagation and meteorological events and their impact on the spread of noise. The environmental factors more or less influencing the climate and noise spread in the living area have been determined. With reference to the received information, the ways to reduce noise have been suggested. Straipsnyje nagrinėjamas gokartų keliamo triukšmo sklidimas į gyvenamąją aplinką ir ieškoma priemonių jam slopinti. Eksperimentiniams tyrimams atlikti buvo naudojamas precizinis garso lygio analizatorius „Bruel&Kjaer 2260“. Bendradarbiaujant su Lietuvos hidrometeorologijos tarnyba panaudoti santykinės oro drėgmės, vėjo stiprumo ir krypties, dirvožemio paviršiaus temperatūros bei oro temperatūros duomenys. Vadovaujantis Lietuvos higienos normomis HN 33:2011 „Triukšmo ribiniai dydžiai gyvenamuosiuose ir visuomeninės paskirties pastatuose bei jų aplinkoje“ nustatomos zonos, kuriose triukšmo lygis yra viršijamas, ir parenkant triukšmo mažinimo priemones siekiama triukšmą sumažinti iki leidžiamųjų normų. Gautų rezultatų analizės metu ieškoma dėsningumų tarp triukšmo sklidimo ir meteorologinių reiškinių bei jų daroma įtaka triukšmo plitimui. Nustatomi aplinkos klimato veiksniai, darantys įtaką ar mažiau veikiantys triukšmo sklaidą gyvenamojoje teritorijoje. Atsižvelgiant į gautus rezultatus siūlomi triukšmo mažinimo būdai.

scholarly journals Design And Experimental Studies Of Flexible Trailing Edge For Variable Camber Morphing Wing

2021 ◽  
Author(s):  
Ahmad T. Kalaji
Keyword(s):  
Experimental Data ◽  
Carbon Fiber ◽  
Deflection Angle ◽  
Experimental Studies ◽  
Morphing Wing ◽  
Trailing Edge ◽  
Wing Section ◽  
Rigid Constraint ◽  
The Difference

This thesis presents a flexible trailing edge mechanism capable of undergoing a change in camber for a wing section. The mechanism takes advantage of a rigid constraint between the ends of two flexible carbon fiber panels, which produces a deflection when there is a difference in length between the two panels. A prototype was designed and built and experimental data was collected for the deformation of the panels for different values of lengths and analyzed to find a function to describe the coefficients which form the polynomials describing the shape for each of the panels, based on the difference in length value. Deflection and deflection angle results were used to develop a controller which will calculate the required change in length based on a deflection or angle and a bottom panel length input.

scholarly journals Appraisal of Noise Level Dissemination Surrounding Mining and Industrial Areas of Keonjhar, Odisha: a Comprehensive Approach Using Noise Mapping

2017 ◽  
Vol 42 (3) ◽  
pp. 423-432 ◽  
Author(s):  
Satish K. Lokhande ◽  
Satyajeet A. Dhawale ◽  
Samir S. Pathak ◽  
Rakesh Gautam ◽  
Mohindra C. Jain ◽  
...  
Keyword(s):  
Noise Level ◽  
Sound Level ◽  
Noise Levels ◽  
Night Time ◽  
Noise Mapping ◽  
High Noise ◽  
Sensitive Areas ◽  
Sound Levels ◽  
Directorate General ◽  
Open Cast

Abstract Noise mapping is a well-established practice among the European nations, and it has been follow for almost two decades. Recently, as per guidelines of the Directorate General of Mines Safety (DGMS), India, noise mapping has been made mandatory in the mining expanses. This study is an effort to map the noise levels in nearby areas of mines in the northern Keonjhar district. The motive of this study is to quantify the existing A-weighted time-average sound level (LAeq,T ) in the study area to probe its effects on the human dwellings and noise sensitive areas with the probability of future development of the mines, roads, and industrial and commercial zone. The LAeq,T was measured at 39 identified locations, including industrial, commercial, residential, and sensitive zones, 15 open cast mines, 3 major highways, and 3 haulage roads. With the utilisation of Predictor LimA Software and other GIS tools, the worked out data is mapped and noise contours are developed for the visualisation and identification of the extent and distribution of sound levels across the study area. This investigation discloses that the present noise level at 60% of the locations in silence and residential zone exposed to significantly high noise levels surpasses the prescribed limit of Central Pollution Control Board (CPCB), India. The observed day and night time LAeq, T level of both zones ranged between 43.2-62.2 dB(A) and 30.5-53.4 dB(A), respectively, whereas, the average Ldn values vary between 32.7 and 51.2 dB(A). The extensive mobility of heavy vehicles adjoining the sensitive areas and a nearby plethora of open cast mines is the leading cause of exceeded noise levels. The study divulges that the delicate establishments like schools and hospitals are susceptible to high noise levels throughout the day and night. A correlation between observed and software predicted values gives R2 of 0.605 for Ld, 0.217 for Ln, and 0.524 for Ldn. Finally, the mitigation measure is proposed and demonstrated using a contour map showing a significant reduction in the noise levels by 0-5.3 dB(A).

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