• Wind and Structures
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• 제4권5호
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• pp.399-412
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• 2001

Simultaneous pressure and force measurements have been conducted on a stationary box deck section model for two configurations (namely without and with New Jersey traffic barriers) at various angles of incidence. The mean and fluctuating aerodynamic coefficients and pressure coefficients were derived, together with their spectra and with the coherence functions between the pressures and the total aerodynamic forces. The mean aerodynamic coefficients derived from force measurements are first compared with those derived from the integration of the pressures on the deck surface. Correlation between forces and local pressures are determined in order to gain insight on the wind excitation mechanism. The influence of the angle of incidence on the pressure distribution and on the fluctuating forces is also analysed. It is evidenced how particular deck section areas are more responsible for the aerodynamic excitation of the deck.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.373-379
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• 2001

When a train runs into a tunnel at high-speed, aerodynamic drag suddenly increases and the booming noise is generated at the exit of tunnel. The noise shape is very important to reduce the aerodynamic drag in tunnel as well as on open ground, and the micro-pressure wave that is a source of booming noise is dependent on nose shape, especially on area distribution. In this study, the nose shape has been optimized employing the response surface methodology and the axi-symmetric compressible Navier-Stokes equations. The optimal designs have been executed imposing various conditions of the aerodynamic drag and the micro-pressure wave on object functions. The results show that the multi-objective design was successful to decrease micro-pressure wave and aerodynamic drag of trains.

• 대한기계학회논문집B
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• 제25권4호
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• pp.507-513
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• 2001

Time averaged pressure distributions in a high-speed centrifugal compressor channel diffuser at design and off-design flow rates are investigated. Pressure distributions from the impeller exit to the channel diffuser exit are measured for various flow rates from choke to near surge condition, and the effects of operating condition are discussed. The strong non-uniformity in the pressure distribution is obtained over the vaneless space and semi-vaneless space caused by the impeller-diffuser interaction. As the flow rate increases, flow separation near the throat, due to large incidence angle at the vane leading edge, increases aerodynamic blockage and reduces the aerodynamic flow area downstream. Thus the minimum pressure location occurs downstream of the geometric throat, and it is named as the aerodynamic throat. And at choke condition, normal shock occurs downstream of this aerodynamic throat. The variation in the location of the aerodynamic throat is discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.548-554
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• 2000

The aim of this paper is to understand the time averaged pressure distributions in a high-speed centrifugal compressor channel diffuser at design and off-design flow rates. Pressure distributions from the impeller exit to the channel diffuser exit are measured and discussed far various flow rates from choke to near surge condition, and the effect of operating condition is discussed. The strong non-uniformity in the pressure distribution is obtained over the vaneless space and semi-vaneless space caused by the impeller-diffuser interaction. As the flow rate increases, flow separation near the throat, due to large incidence angle at the vane leading edge, increases aerodynamic blockage and reduces the aerodynamic flow area downstream. Thus the minimum pressure location occurs downstream of the geometric throat, and it is named as the aerodynamic throat. And at choke condition, normal shock occurs downstream of this aerodynamic throat. The variation in the location of the aerodynamic throat is discussed.

• 말소리와 음성과학
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• 제6권4호
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• pp.195-203
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• 2014

The aim of this study was to investigate the effects of phonation types ([+/- aspirated], [+/- fortis]) on aerodynamic measures with Korean bilabial stops. Sixty-three healthy young adults (30 males, 33 females) participated to evaluate the VOEF (Voicing Efficiency) tasks with bilabial stop consonants /$p^h$/, /p/, /p'/ using Phonatory Aerodynamic System (PAS) Model 6600 (Kay PENTAX Corp, Lincoln Park, NJ). All VOEF measures were significantly influenced by phonation types except RANP(pitch range)(p <.01). For sound pressure, maximum SPL, mean SPL, and Mean SPL during Voicing have been shown to be significantly greatest in fortis stop /p'/ than aspirated /$p^h$/ and lenis stop /p/ (p<.001). On the other hand, mean pitch after lenis stop was significantly lower than after aspirated and fortis stops (p<.001). Peak expiratory airflow, Target airflow, and FVC (Expiratory volume) were significantly lowest in fortis stop /p'/ which might be associated with higher aerodynamic resistance while peak air pressure and mean peak air pressure during closure were significantly lower in lenis stop /p/. Additionally, AEFF (Aerodynamic efficiency) was significantly higher in fortis stop /p'/ than lenis stop /p/ as well as aspirated stop /$p^h$/ (p<.001). Thus, sound pressure, airflow parameters, and aerodynamic resistance made crucial roles in distinguishing fortis /p'/ from lenis stop /p/ and aspirated. Additionally, pitch and subglottal air pressure parameters were important aerodynamic characteristics in distinguishing lenis /p/ from fortis /p'/ and aspirated /$p^h$/. Therefore, accurate aspirated /p/ stop consonant should be elicited when collecting the airflow, intraoral pressure related data with patients with voice disorders in order to enhance the reliability and relevance or validity of aerodynamic measures using PAS.

• 음성과학
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• 제12권4호
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• pp.203-213
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• 2005

This study was conducted to investigate the respiratory and aerodynamic function of adductor spasmodic dysphonia (ADSD) patients. Participants were (1) 18 females SD patients with non- Botulinum toxin injection (2) 14 females SD patients who had taken treatment of Botulinum toxin injection. (3) 14 age- and sex- matched normal female controls. Spirometer and phonatory function analyzer were used for respiratory muscle pressure (MIP: Maximum inspiratory pressure), MEP: Maximum expiratory pressure)& MPT(Maximum phonation time) and aerodynamic(F0:Fundamental frequency, intensity, MFR: Mean flow late, Psub: Subglottal pressure) measurement. The results were as follows: (1) Normal group was significantly higher in MIP, MEP, MPT than two SD groups (p < .05); (2) MPT was significantly lower in SD with non-Botulinum toxin injection group than SD with the treatment experience of Botulinum toxin injection (p < .05); (3) All aerodynamic parameters, F0, intensity, MFR, Psub, were not significantly different among three groups(p > .05).The reason of short MPT in ADSD may use lower respiratory pressure than normal group as strategy to decrease their tremulous voice quality. Moreover respiratory muscle pressure was lower than normal group regardless of botulinum toxin injection treatment.

• 한국항공우주학회지
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• 제33권6호
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• pp.31-38
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• 2005

하중해석을 위한 선형 패널법에서 압력과 다운워시와의 관계는 공력영향계수로 표현되며 점성 효과는 무시되고 천음속 영역에서 압축성 효과를 적절히 표현하지 못한다. 공력영향계수는 공력면의 평면형상에 의해 결정되므로 저 레이놀즈 수의 유동의 특성을 나타내는 데는 한계가 있다. 따라서 공력계수의 시험치를 구속조건으로 하여 압력분포를 직접 보정하거나 다운워시를 보정하여 유효 캠버나 두께를 반영하여 압력분포를 보정하게 된다. 본 논문에서는 전승보정방법과 후승보정방법을 초소형 비행체의 균형해석 및 하중해석을 위한 공기력 보정에 적용하였다. 이론적인 공기력은 패널법을 이용하였으며 단일 구속조건과 이중 구속조건을 적용하여 보정행렬과 보정된 압력계수를 구하였다. 초소형 비행체의 공력보정에 있어서 비행영역의 특성으로 인해 후승보정방법이 보다 나은 결과를 나타내었다.

• 말소리와 음성과학
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• 제6권1호
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• pp.105-117
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• 2014

The purpose of this study was to (1) establish a Korean adult normative database for phonatory aerodynamic measures obtained with the KayPENTAX Phonatory Aerodynamic System (PAS) Model 6600, (2) investigate the intra-subject reliability of these measures across three testing sessions, and (3) examine the effect of gender on those measures. 170 healthy normal speakers (70 men and 100 women) between the ages 18 and 49 years participated in the study. The PAS protocol of maximum phonation and voicing efficiency were conducted and 25 measures were obtained. All aerodynamic measures taken in this study demonstrated high intra-subject reliability in clinical aspect. There were no significant effect of gender in the measures related to sound pressure and subglottal pressure. However, significant differences for gender were found for phonation time, airflow rate, expiratory volume, aerodynamic power, SPL range, pitch range, mean pitch, aerodynamic resistance, and aerodynamic efficiency. Clinicians should be aware of significant gender effects in some aerodynamic parameters when interpreting the data obtained from PAS.

• 동력기계공학회지
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• 제17권6호
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• pp.73-78
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• 2013

A Small-size axial fan(SSAF) has widely been utilized to circulate a cooling air in a refrigerator, etc. Generally, the aerodynamic performance of SSAF is strongly dependent upon the depth between SSAF and bellmouth, and it includes axial, partially stalled, mostly stalled and radial flow regions according to the flow coefficient. In this study, four kinds of bellmouth depths were considered to analyze the aerodynamic performance of SSAF. As a bellmouth depth increases, a maximum flowrate decreases, but a maximum static pressure increases. Also, stall region includes an inflection point in all aerodynamic performance curves. Finally, a static pressure efficiency shows the maximum value of 37%.

• 대한후두음성언어의학회지
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• 제13권1호
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• pp.23-27
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• 2002

The purpose of the study is to examine differences in subglottic air pressure as a function of phonetic context. The phonetic contexts consisted of $/i:{p^h}i:{p^h}i:/,/{p^h}i:{p^h}i:/, and /{p^h}{p^h}/$. The aerodynamic and phonatory parameters are investigated in 20 female normal adults. All measurements are taken and analysed using Aerophone II voice function analyzer. The aerodynamic parameters are Peak Air Pressure(PAP) and Mean Air Pressure(MAP), and the phonatory parameters are Phonatory Flow Rate(PFR) Maximum SPL(MSPL), Phonatory SPL(PSPL), Phonatory Power (PP), Phonatory Efficiency(PE), and Phonatory $Resistance^*$ 10-5(PR). A one-way ANOVA revealed the following results. First, the aerodynamic parameters are not significantly different. Second, Peak Air Pressure(PAP) and Mean Air Pressure(MAP), as well as the phonatory parameters such as Phonatory Flow Rate(PFR) Maximum SPL(MSPL), Phonatory SPL(PSPL), and Phonatory Efficiency(PE) were significantly different. Therefore, it is advised that clinicians use only aerodynamic parameters but phonatory parameters when using Aerophone II.