INFLUENCES OF THE AREA RATIO OF THE SKIN GLASS AND THE OUTER WALL POSITION OF A SIDE CORRIDOR ALONGSIDE AN EXTERNAL PASSAGE ON PSYCHOLOGICAL QUANTITIES OF STUDENTS WITH HEARING IMPAIRMENT

2020 ◽  
Vol 85 (778) ◽  
pp. 935-942
Author(s):  
Toshiyuki MIURA ◽  
Hiroki SATAKE ◽  
Hiroki YAMAWAKI ◽  
Hajime IMAI
Keyword(s):  
Hearing Impairment ◽  
Outer Wall ◽  
Area Ratio ◽  
Wall Position

Flow Characteristics in Symmetrically Branched Tubes Simulating the Human Aortic Bifurcation

1980 ◽  
Vol 102 (4) ◽  
pp. 340-342 ◽  
Author(s):  
F. Walburn ◽  
P. Stein
Keyword(s):  
Pulsatile Flow ◽  
Transient Flow ◽  
Flow Characteristics ◽  
Outer Wall ◽  
Laser Doppler Anemometer ◽  
Area Ratio ◽  
Minimal Flow ◽  
Aortic Bifurcation ◽  
Descending Aorta ◽  
Shear Rates

The purpose of this study was to investigate the characteristics of flow in a symmetrically branched tube that had an area ratio (0.8) and angle of branching (70 deg) that were comparable to the human descending aorta. Velocity profiles were measured in steady and pulsatile flow with a laser Doppler anemometer. A region of transient flow reversal was found along the outer wall during minimal flow in the pulsatile cycle. Flow separation did not occur. For both steady and pulsatile flow, the shear rates were higher along the inner wall and lower along the outer wall in the region of the vertex of the bifurcation.

scholarly journals Numerical Analysis of a Vortex Controlled Diffuser

1995 ◽  
Vol 117 (1) ◽  
pp. 86-90 ◽  
Author(s):  
R. E. Spall
Keyword(s):  
Turbulence Model ◽  
Stokes Equations ◽  
Numerical Study ◽  
Outer Wall ◽  
Vortex Chamber ◽  
Area Ratio ◽  
Navier Stokes ◽  
Good Qualitative Agreement ◽  
Abrupt Increase ◽  
Navier Stokes Equations

A numerical study of a prototypical vortex controlled diffuser is performed. The basic diffuser geometry consists of a step expansion in a pipe of area ratio 2.25:1. The incompressible Reynolds averaged Navier-Stokes equations, employing the RNG based κ − ∈ turbulence model, are solved. Results are presented for bleed rates ranging from 1 to 7 percent. Diffuser efficiencies in excess of 80 percent were obtained. These results are in good qualitative agreement with previous experimental work. The results do not confirm previous suggestions that the increases in effectiveness of the VCD over a step expansion result from an inhibition of flow separation due to the generation and downstream convection of extremely high levels of turbulence generated in the region of the bleed gap. The results do indicate that the effectiveness of the diffuser is a consequence of the turning of the flow toward the outer wall due to the influence of the low pressure vortex chamber. Calculations employing the RNG based turbulence model were able to capture the abrupt increase in diffuser effectiveness that has been shown experimentally to occur at low bleed rates. Calculations employing the standard κ − ∈ model were unable to predict this occurrence.

Numerical investigation of the effect of geometry on the performance of a jet pump

2011 ◽  
Vol 225 (7) ◽  
pp. 1614-1625 ◽  
Author(s):  
R Mallela ◽  
D Chatterjee
Keyword(s):  
Energy Requirement ◽  
Outer Wall ◽  
Area Ratio ◽  
Tube Length ◽  
Maximum Efficiency ◽  
Jet Pump ◽  
The Past ◽  
Ratio Curve ◽  
Discharge Ratio ◽  
Parametric Studies

Jet pump plays a major role in transporting materials. The efficiency of jet pump is poor and it usually has a sharp peak in the efficiency–discharge ratio curve. These are undesirable. In the past, experiments were conducted to understand the functioning of each component of the jet pump. The experimental method is reliable but performing parametric studies through experiments is problematic as it is difficult to systematically vary one parameter while keeping other parameters unchanged. In this study, numerical simulations were carried out to determine the effects of area ratio, setback distance, mixing tube length, and shape of the driving nozzle on the performance of the jet pump. It was seen that major losses arise in the jet pump primarily due to an improper mixing of primary and secondary fluids and because of the formation of recirculation near the mixing tube entrance. Based on these studies, a normalized mixing tube length ( Lm/ Dm) of 7–9, area ratio of 0.28, setback ratio of 1.54–2.02, and a modified shape of the outer wall of driving nozzle are recommended. Such geometry offers maximum efficiency of 40 per cent, a relatively flat efficiency curve, and a lower total pressure drop. This last effect is important from the energy requirement to drive the centrifugal pump.

An Experimental Investigation of the Performance of Equiangular Annular Diffusers with Swirled Flow

1985 ◽  
Vol 199 (4) ◽  
pp. 293-297
Author(s):  
A M Elkersh ◽  
A H Elgammal ◽  
N R L Maccallum
Keyword(s):  
Experimental Study ◽  
Experimental Investigation ◽  
Outer Wall ◽  
Flow Patterns ◽  
Area Ratio ◽  
Geometrical Parameters ◽  
Centrifugal Forces ◽  
Free Vortex ◽  
Inlet Swirl ◽  
Swirled Flow

An experimental study of the influence of geometrical parameters and swirl on the performance of equiangular diffusers is presented. Three diffusers were tested over a range of inlet swirls up to 45°, the swirls being of free vortex distribution. The data presented indicate similar flow patterns for different cant angles, and show that the centrifugal forces due to swirl stabilize the flow on the outer wall, while increasing the tendency towards separation at the inner wall. Diffuser performance improves as the inlet swirl increases up to 30°, the improvement being influenced by area ratio and cant angle. A further increase of swirl causes a deterioration of performance.

Impact of a Cooled Cooling Air Installation on the External Aerodynamics of a Gas Turbine Combustion System

2015 ◽  
Author(s):  
A. D. Walker ◽  
L. Guo
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Leading Edge ◽  
Outer Wall ◽  
Area Ratio ◽  
Test Facility ◽  
Combustion System ◽  
External Aerodynamics ◽  
Cooling Air ◽  
The Impact

The trend for higher overall pressure ratios means that turbine entry temperatures are continually increasing. Furthermore, the development of lean, low-emission combustion systems reduces the availability of cooling air and is accompanied by new problems at the combustor/turbine interface. For example, the exit temperature traverse differs from that found in traditional rich-burn combustors with increased swirl and a much flatter profile. Effectively cooling the turbine components is becoming increasingly difficult. One solution is to employ cooled cooling air (CCA) where some of the compressor efflux is diverted for additional cooling in a heat exchanger located in the by-pass duct. An example CCA system is presented which includes an off-take within the dump cavity and the addition of radial struts within the pre-diffuser through which the cooled air is returned to the engine core. This paper addresses the impact this CCA system has on the combustion system external aerodynamics. This included the development of a fully annular, isothermal test facility which incorporated a bespoke 1.5 stage axial compressor, engine relevant outlet guide vanes, pre-diffuser and combustor geometry. A datum aerodynamic performance was established for a non-CCA configuration with a clean, un-strutted pre-diffuser. Results for this baseline CCA system demonstrated that inclusion of a bleed in the dump cavity had limited effect on the overall flow field. However, the inclusion of struts within the pre-diffuser caused a reduction in area ratio and a notable increase in system loss. Consequently an alternative pre-diffuser was designed (using CFD) with the aim of increasing the area ratio back to that of the un-strutted datum. A so-called hybrid diffuser was designed in which the CCA bleed was moved to the pre-diffuser outer wall. The bleed was then used to re-energize the boundary layer, preventing flow separation, enabling the area ratio to be increased close to the datum value. The mechanisms of the hybrid diffuser are complex; the geometry of the off-take and its location with respect to the OGV and strut leading edge were seen to be critical. Experimental evaluation of the final design demonstrated the effective operation the hybrid diffuser with the result that the system loss returned to a level close to that of the datum. Only small differences were seen in the overall flow field.

Architecture of Radiolitid Rudist (Mollusca) Shell-Wall Structures and its Phylogenetic Implications

1975 ◽  
Vol 33 ◽  
pp. 686-687
Author(s):  
David H. Sturm ◽  
Bob F. Perkins
Keyword(s):  
Phylogenetic Relationships ◽  
Outer Wall ◽  
Shell Microstructure ◽  
Shell Wall ◽  
Wall Structures ◽  
Phylogenetic Implications ◽  
Cellular Wall ◽  
Superfamily Analysis ◽  
Central Texas

Each of the seven families of rudists (Mollusca, Bivalvia, Hippuritacea) is characterized by distinctive shell-wall architectures which reflect phylogenetic relationships within the superfamily. Analysis of the complex, calcareous, cellular wall of the attached valve of the radiolite rudist Eoradiolites davidsoni (Hill) from the Comanche Cretaceous of Central Texas indicates that its wall architecture is an elaboration of the simpler monopleurid rudist wall and supports possible radiolite-monopleurid relationships.Several well-preserved specimens of E. davidsoni were sectioned, polished, etched, and carbon and gold coated for SEM examination. Maximum shell microstructure detail was displayed by etching with a 0.7% HC1 solution from 80 to 100 seconds.The shell of E. davidsoni comprises a large, thick-walled, conical, attached valve (AV) and a small, very thin, operculate, free valve (FV) (Fig. 1a). The AV shell is two-layered with a thin inner wall, in which original structures are usually obliterated by recrystallization, and a thick, cellular, outer wall.

Hearing Aid Amplification Reduces Communication Effort of People With Hearing Impairment and Their Conversation Partners

2020 ◽  
Vol 63 (4) ◽  
pp. 1299-1311 ◽  
Author(s):  
Timothy Beechey ◽  
Jörg M. Buchholz ◽  
Gitte Keidser
Keyword(s):  
Hearing Impairment ◽  
Hearing Aid ◽  
Normal Hearing ◽  
Referential Communication ◽  
Hearing Impaired ◽  
Directional Hearing ◽  
Acoustic Environment ◽  
Communication Task ◽  
Acoustic Environments ◽  
The Impact

Objectives This study investigates the hypothesis that hearing aid amplification reduces effort within conversation for both hearing aid wearers and their communication partners. Levels of effort, in the form of speech production modifications, required to maintain successful spoken communication in a range of acoustic environments are compared to earlier reported results measured in unaided conversation conditions. Design Fifteen young adult normal-hearing participants and 15 older adult hearing-impaired participants were tested in pairs. Each pair consisted of one young normal-hearing participant and one older hearing-impaired participant. Hearing-impaired participants received directional hearing aid amplification, according to their audiogram, via a master hearing aid with gain provided according to the NAL-NL2 fitting formula. Pairs of participants were required to take part in naturalistic conversations through the use of a referential communication task. Each pair took part in five conversations, each of 5-min duration. During each conversation, participants were exposed to one of five different realistic acoustic environments presented through highly open headphones. The ordering of acoustic environments across experimental blocks was pseudorandomized. Resulting recordings of conversational speech were analyzed to determine the magnitude of speech modifications, in terms of vocal level and spectrum, produced by normal-hearing talkers as a function of both acoustic environment and the degree of high-frequency average hearing impairment of their conversation partner. Results The magnitude of spectral modifications of speech produced by normal-hearing talkers during conversations with aided hearing-impaired interlocutors was smaller than the speech modifications observed during conversations between the same pairs of participants in the absence of hearing aid amplification. Conclusions The provision of hearing aid amplification reduces the effort required to maintain communication in adverse conditions. This reduction in effort provides benefit to hearing-impaired individuals and also to the conversation partners of hearing-impaired individuals. By considering the impact of amplification on both sides of dyadic conversations, this approach contributes to an increased understanding of the likely impact of hearing impairment on everyday communication.

Relationships Between Subjective Ratings and Objective Measures of Performance in Speechreading Sentences

1997 ◽  
Vol 40 (4) ◽  
pp. 900-911 ◽  
Author(s):  
Marilyn E. Demorest ◽  
Lynne E. Bernstein
Keyword(s):  
Hearing Impairment ◽  
Performance Evaluations ◽  
Objective Measures ◽  
Large Individual ◽  
Subjective Ratings ◽  
Objective Performance ◽  
Phonetic Distance ◽  
Stimulus Length ◽  
Measures Of Performance ◽  
Confidence Scale

Ninety-six participants with normal hearing and 63 with severe-to-profound hearing impairment viewed 100 CID Sentences (Davis & Silverman, 1970) and 100 B-E Sentences (Bernstein & Eberhardt, 1986b). Objective measures included words correct, phonemes correct, and visual-phonetic distance between the stimulus and response. Subjective ratings were made on a 7-point confidence scale. Magnitude of validity coefficients ranged from .34 to .76 across materials, measures, and groups. Participants with hearing impairment had higher levels of objective performance, higher subjective ratings, and higher validity coefficients, although there were large individual differences. Regression analyses revealed that subjective ratings are predictable from stimulus length, response length, and objective performance. The ability of speechreaders to make valid performance evaluations was interpreted in terms of contemporary word recognition models.

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