• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1996.10a
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• pp.184-187
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• 1996

기존의 항만 부진동현상 해석은 대부분 완전유체라는 가정하에 선형이론에 기초하여 개발된 수치 모델에 의해 수행되고 있다. 실제의 경우에는 해저면의 마찰, 고체경계면을 따른 에너지 손실, 단면의 급 축소 및 확대에 따른 에너지 손실 등이 존재하므로, 이와 같은 에너지의 손실을 고려하지 않고 선형해석을 수행하게 되면 실제와는 다른 과장된 결과를 얻게 된다. 특히, 항 입구의 폭이 좁은 경우에는 실제와는 다르게 증폭비가 대단히 크게 예측된다. (중략)

• Proceedings of the KAIS Fall Conference
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• 2001.05a
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• pp.108-112
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• 2001

본 논문에서는 전산유체해석 기법을 이용하여 저소음ㆍ고효율 공조기의 입구형상에 대한 유동해석을 하였다. 공조기 입구형상을 결정하는 여러 설계변수가 입구와 출구의 유동조건과 유로의 압력손실에 미치는 영향을 평가하였다. 이를 바탕으로 입구와 출구유동의 균일성과 압력손실의 최소화를 만족하는 최적의 설계 변수를 결정하여 공조기의 최적설계를 달성하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.295-298
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• 2009

Bent ducts add loss and decrease efficiency. Many researchers have been conducted the performances of bent ducts, but their shapes of inlet and outlet are same. However, in this investigation, the focus is on a bent duct which is annular at the inlet and circular at the outlet. The bent duct of these complex shapes has not been investigated, but has been used in many fields. The performance of such bent duct is investigated under inlet speed 54 m/s and Re = 238,000. Wall static pressure tappings are located surface of the bent duct to measure the static pressure and a probe is traversed at the inlet and outlet of the bent duct to measure the total pressure. As a result, it presents static pressure distribution on the bent duct surface, streamwise velocity profile at inlet and outlet of the bent duct and total pressure loss profile at outlet. In this investigation, the total pressure loss coefficient is 0.243.

• Aerospace Engineering and Technology
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• v.8 no.2
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• pp.8-12
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• 2009

It is absolutely necessary to measure the inlet pressure and temperature of a turbine or a compressor to evaluate the performance of it. And to measure the representative-averaged pressure and temperature of turbine inlet flow, rake is normally used. Rake has several elements for temperature and pressure and several rakes are installed at the inlet to average the radial and circumferential distribution of inlet flow. However the rakes cause unexpected losses and flow distortion at the turbine inlet which make the measured rake data different from true inlet value. So the evaluation of a turbine or a compressor performance becomes not accurate. This study suggest a correlation method which measure the loss by inlet rake and incorporates it in evaluating the performance of turbomachinery.

• Journal of Biomedical Engineering Research
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• v.22 no.1
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• pp.35-40
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• 2001

압력기반의 유한체적법과 k-$\varepsilon$난류모델을 이용하여 신생아 보육기 내의 삼차원 정상난류유동해석과 대류현상에 의한 열전달을 해석하였다. 보육기 내의 주된 공기유동은 입구에서 유입된 공기가 보육기 위쪽을 지나 출구로 이동하며 각진 구석에서 작은 와류들이 관찰되었다. 보육기의 입구부를 제외한 대부분에서의 유속은 0.1m/s 이하로 나타났으며, 신생아의 다리부분에서의 속도가 머리부분보다 다소 크게 관찰되었다. 입구쪽의 온도가 출구쪽의 온도보다 1~2$^{\circ}C$ 높게 나타났으며 속도 크기가 큰 다리부분에서의 온도가 머리 또는 목부분보다 다소 낮았다. 보육기 내의 온도변화는 약3~4$^{\circ}C$로 다소 크게 나타났는데 이는 입구에서 유입된 공기가 상벽과 직각으로 만나며, 보육기 외벽의 각진 구석부분에 의한 영향으로 생각된다. 따라서 입구속도를 적절히 줄이거나 유선형의 유동을 갖도록 설계하여 열손실을 최소화한다면 보다 효율적인 보육기가 될 것으로 생각된다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.4
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• pp.216-230
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• 1999

A Galerkin finite element model for the analysis of harbor oscillation has been developed based on the extended mild-slope equation. Infinite elements are used to accomodate the radiation condition at infinity and joint elements to treat the matching conditions at the harbor entrance which include the energy loss due to flow separation. The numerical tests for rectangular harbors with fully or partially open entrances show that the energy loss at the harbor entrance considerably reduces the the amplification ratios at the innermost parts of the harbors and that the amplification ratios decrease considerably with increasing incident wave heights and jet lengths at the harbor entrance. Application of the model to the Gamcheon harbor show that when the incident wave amplitude is small the amplification ratios rather increase when the entrance energy loss is included than when ignored because of the shift of the resonance periods. Even though the entrance energy loss was insignificant for the measured long-period incident waves, it would be of great importance if the incident waves were large as in the attack of tsunamis. The resonance period of the Helmholtz mode at the Gamcheon Harbor was calculated to be 31 minutes, which agrees well with the measured one between 27 and 33.3 minutes. The measured resonance periods between 9.4 and 12.1 minutes and 5.2 and 6.2 minutes were also calculated by the numerical model as 10.4 minutes and 6.6 or 5.6 minutes, indicating good performance of the model. On the other hand, it was shown that a variety of oscillation modes exists in the Gamcheon Harbor and lateral resonances of considerable amplification ratios also exist at the periods of 3.6 and 1.6 minutes as in the Young-II Bay.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.1
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• pp.48-55
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• 2010

The purpose of this paper was to address the methodology of the air flow measurement using duct mach number that was considered area-weighed average obtained by total, static pressure and temperature measured at engine inlet duct. Without installing boundary rake, the prediction of air flow measurement was discussed. Actual air flow measurement and pressure value using pressure loss through inlet seal were described to improve the reliability and operability of altitude engine test facility.

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.29-34
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• 2007

The purpose of this paper was to address the methodology of the air flow measurement using duct mach number that was considered area-weighed average obtained by total pressure and temperature measured at engine inlet duct. Without installing boundary rake, the prediction of air flow measurement was discussed. Actual air flow measurement and pressure value using pressure loss through inlet seal were described to improve the reliability and operability of altitude engine test facility.

• 유체기계공업학회:학술대회논문집
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• 1998.02a
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• pp.150-156
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• 1998

가스터어빈 트랜지션 덕트 내에서의 공기 역학적인 거동을 입구 스월각의 변화에 대하여 고찰하였다. 트렌지션 덕트가 작은 확산각(divergence angle)을 가지더라도 스트럿 영향으로 인한 탈설계점에서의 유동 패턴은 트랜지션 덕트 내에서의 유동특성을 더욱 악화시킨다. 시험범위의 스월각은 마하수 변화에 따라 손실계수에 큰 영향을 주지 못하였으며 트랜지션 덕트 내에서의 손실 정조는 만족할만 하나, 시험결과에 따르면 저압터빈의 노즐손실은 큰 입사각의 영향으로 커질것으로 생각되며, 또한 스트럿으로부터 떨어져 나오는 와류는 저압터빈의 로우터 블레이드의 진동에 악영향을 미칠 것으로 생각된다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.103-106
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• 2008

In this work it was studied that the effect on sub-component of engine considering change of engine inlet pressure caused by variable acceleration during flight of launcher. Also the transitional performance was predicted according to variable acceleration. Engine inlet pressure was defined as summation of propellant head in tank, ullage pressure and pressure difference of line, etc. Therefore consumption of propellant and acceleration of launcher led to change of engine inlet pressure, which affected on discharge pressure of pumps. This effect changed mass flow rate of gas generator and main combustor hence it was observed that engine performance was changed definitely.