• Journal of Advanced Marine Engineering and Technology
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• v.37 no.2
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• pp.156-162
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• 2013

The characteristics of the unsteady flowfield of a square prism having a detached splitter plate at the wake side were investigated by advanced vortex method. The instantaneous and average velocity field and pressure field around a square prism without and having splitter plate were calculated by forcing the gap ratio having the maximum drag reduction rate, at Reynolds number $Re=1.0{\times}10^4$ and the width ratio H/B=1.0 of splitter to the prism width. The drag and lift coefficients on the square prism were also obtained. The calculated results agree with the measured drag coefficients and pressure distributions on the square prism. The vortices of the opposite direction at upside and down side of the splitter plate were generated by installing of the plate. And the drag on the square prism was decreased by increasing of the pressure of back face of the prism with the vortices.

• Membrane Journal
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• v.8 no.3
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• pp.109-116
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• 1998

일반적으로 투과증발 막분리 공정에서 막상부 압력은 상압 부근에서 설정되며 막하부 압력은 투과성분의 포화증기압 보다 낮게 유지하므로써 막을 통한 물질 투과가 일어난다. 이중에 하부압력은 막공정의 추진력과 밀접한 관련이 있다. 즉, 막하부의 조건에 따라 막공정의 추진력이 결정되며 또한 막내부의 상구배가 달라진다. 그러므로 막하부의 공정조건은 막의 투과 분리특성을 결정하는 매우 중요한 제어대상이 된다. 많은 연구자들이 막하부 압력에 따른 투과속도 및 선택도 변화에 대한 연구를 진행해왔는데 이들 대부분은 막하부 압력을 투과공정의 추진력과 관련을 지어 투과 분리거동을 설명하였으며 1980년 후반 이후부터 유체역학 관점에서 막하부 압력이 투과특성에 끼치는 영향을 검토하기 시작하였다. 본 장에서는 막하부 압력이 막투과 분리 특성에 끼치는 영향에 대한 이해를 돕고자 발표된 연구 내용을 토대로 하여 투과증발 막분리 공정에서 막하부 압력의 중요성을 간략하게 정리해 보았다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.2
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• pp.213-218
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• 2013

This paper presents are experimental investigation to figure out slamming impact pressure and flow characteristics of a wedge type structure in free fall. The flow field has been obtained by 2-frame grey level cross correlation PIV(Particle Image Velocimetry) method, the impact presure of free fall structure by a pressure acquisition system apply to Dewetron system. The angles between a model and the free surface are adapted $15^{\circ}$, $25^{\circ}$, $35^{\circ}$ and $45^{\circ}$ respectively. Velocity field of water exit has higher better than water entry. The impact pressure under the bottom of the model ha been appeared higher values at 15 degrees than 45 degrees, and also at P1.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.493-499
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• 2013

This paper presents are experimental investigation to figure out impact pressure and flow characteristics of a wedge type structure in free fall. The flow field has been obtained by 2-frame grey level cross correlation PIV(Particle Image Velocimetry) method, the impact pressure of free fall structure by a pressure acquisition system apply to Dewetron system. The angles between a model and the free surface are adapted $15^{\circ}$, $25^{\circ}$, $35^{\circ}$ and $45^{\circ}$ respectively. Velocity field of water exit has higher better than water entry. The impact pressure under the bottom of the model has been appeared higher values at $15^{\circ}$ than $45^{\circ}$, and also at P1.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.94-97
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• 2008

As the partial admission turbine has a intrinsically unsteady and three dimensional flow region, numerical calculation time of these study has been too long time. The numerical analysis for gas temperature of turbine blade surface has been performed to investigate development of temperature with various pyro start pressure. Computations have been carried out several turbine rotational speeds in the range from 0 to 16000 rpm and inlet conditions with 1423K, 7.2MPa. As a result, the more rotational speed and pyro starter pressure of turbine increased, the more turbine blade's temperature decreased. It is also found that flow field of turbine blade inlet area at pyro starter pressure of 5.75MPa and rotational speed of 12100 rpm formed surface temperature uniformly.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.2
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• pp.1-8
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• 2009

Present studies of these experiments was conducted to using water, over a range of cross-flow velocities from 42 to 136 m/s, with injection frequencies from 35.7 to 166.2 Hz. In cross-flow field, main parameters of liquid jet for secondary breakup were cross-flow drag rather than pressure pulse frequency. As oscillation of the periodic pressure, liquid jet was moved up and down. Also, a bulk of liquid jet puff was detected at upper field of liquid surface. Because of pressure pulsation frequency, an inclination of SMD for the structured layer was evanescent. Cross-sectional characteristics of SMD at downstream area were non-structured distributions. The tendency of volume flux value for various frequency of pressure pulse was same distribution. And volume flux was decreased when the frequency of pressure pulse increasing.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.1
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• pp.1-12
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• 1998

Industrial ejector system is a facility to transport, to compress or to pump out a low pressure secondary flow by using a high pressure primary flow. An advantage of the ejector system is in its geometrical simplicity, not having any moving part, compared with other fluid machinery. Most of the previous works have been performed experimentally and analytically. The obtained data. are too insufficient to improve our current understanding on the detailed flow field inside the ejector. In order to provide more comprehensive data on this ejector flow field, two-dimensional computations using Reynolds-averaged Navier-Stokes equations were performed for a very wide range of operating pressure ratio of the supersonic ejector with a secondary throat. The current results showed that the supersonic ejector system has an optimum pressure ratio for the secondary flow total pressure to be minimized. The numerical results clearly revealed the shock system, shock/boundary layer interaction, and secondary flow entrainment inside the supersonic ejector.

• 한국가시화정보학회:학술대회논문집
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• 2004.04a
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• pp.9-18
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• 2004

초음속 유동하에서 측추력기 주위의 유동 현상을 실험 및 수치해석을 이용하여 해석하였다. 실험은 버지니아공대의 초음속 풍동과 건국대의 초음속 풍동을 사용하였으며 계산 코드는 Aerosoft 사의 GASP(ver.4.0)과 건국대의 AADL3D를 사용하였다. 실험결과는 Schlieren, Shadow graph 등의 가시화 장치와 압력 센서와 PSP(Pressure Sensitive Paint)를 이용하여 유동장 특성과 압력분포를 구하여 실제 작용되는 힘과 모멘트를 구하였다. 실험조건은 자유류의 흐름이 마하수 4 이고 측추력기와 자유류의 압력비가 532 이었다. 성능향상 방안으로 측추력기 후방에 램프를 설치하는 것을 제안하였으며 이에 대한 실험을 수행하여 수직력에 대한 변화는 없지만 피칭다운 모멘트가 약 $70\%$ 감소함을 보여주어 실제로 성능이 향상되었음을 입증하였다. 또한 측추력기의 성능에 영향을 주는 여러 가지 인자들에 대한 가시화실험을 수행하여 그 이해를 돕고자 하였으며, 현재 건국대에서 보유하고 있는 고속유동 관련 실험장치의 소개와 이를 이용한 연구들을 소개하므로써 압축성 유동장 연구에 이러한 실험장치의 필요성에 대한 이해를 구하고자 한다.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.4
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• pp.42-49
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• 2000

A computation using the mass-averaged implicit Wavier-Stokes equations has been applied to solve the flow fields of the supersonic jets normally injected into supersonic freestreams and several types of turbulence model has been employed to close the governing equations. The ratio of the freestream to injection flow total pressures has been varied to elucidate the major characteristics of the mixing flow of the two streams. The freestream Mach number has been varied to investigate some change in the injection flow field. The results show that the positions of the separation and reattachment, locating upstream and downstream of the injection hole respectively, are strongly dependent on the ratio of total pressures and the freestream Mach number.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.10a
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• pp.3-4
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• 2002