• Fisheries and Aquatic Sciences
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• 제1권2호
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• pp.260-268
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• 1998

A flow pattern and water exchange in Sagami Bay is examined using a barotropic hydraulic model. In the model experiments, the volume transports of the Kuroshio Through Flow were changed with time. The results of the model experiments show that when the volume transport is increased with time, water mass and vorticity are transferred to the inner part of the bay by wakes from the western part of the bay. In the case of decrease, as the wakes are ceased, the inner cyclonic circulation water is discharged to the outside of the bay by its southward extension through the Oshima eastern channel. It is found that the water exchange by the short-term variation of volume transport in time is about 20% of all the bay water.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제3권1호
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• pp.57-73
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• 1999

Baroclinic hydraulic model experiments on the time-varying states of the flow pattern and water exchange in Sagami Bay were carried out based on quasi-steady state experiments on the flow pattern. For the model experiments, density changes as well as time changes in the volume transport of the upper layer were executed to investigate the flow response of the bay in the case of a sudden inflow of low density water and variable volume transport into the Sagami Bay. The results of the model experiments showed that when the volume transport was increased frontal eddies or frontal wave streamers from the Kuroshio Through Flow were transferred to the inner part of the bay along with cyclonic circulation in the bay. In addition, density boundary currents appeared and flowed along the eastern boundary of the bay. As the upper layer density decreased, frontal eddies, frontal streamers and coastal boundary density currents occurred and proceeded along the eastern boundary of the bay at a high speed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.682-687
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• 2003

The variations of temperature and velocity fields in a Hele-Shaw convection cell (HSC) were investigated using a holographic interferometry and 2-D PIV system with varying Rayleigh number. To measure quasisteady changes of temperature field, two different measurement methods of holographic interferometry; double-exposure method and real-time method, were employed. In the double-exposure method, unwanted waves can be eliminated effectively using digital image processing technique and the reconstruction images are clear, but transient flow structure cannot be reconstructed clearly. On the other hand, transient convective flow can be reconstructed well using the real-time method. However, the fringe patterns reconstructed by the real-time method contain more noises, compared with the double-exposure method. Experimental results show a steady flow pattern at low Rayleigh numbers and a time-dependent periodic flow structure at high Rayleigh numbers. The periodic flow pattern at high Rayleigh numbers obtained by the real-time holographic interferometer method is in a good agreement with the PIV results.

• 대한기계학회논문집B
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• 제28권4호
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• pp.493-499
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• 2004

Variations of temperature and velocity fields in a Hele-Shaw convection cell (HSC) were investigated using a holographic interferometry and 2-D PIV system with varying Rayleigh number. To measure quasi-steady variation of temperature field, two different measurement methods of holographic interferometry, double-exposure method and real-time method, were employed. In the double-exposure method, unwanted waves were eliminated effectively using a digital image processing technique. The reconstructed images are clear, but transient flow cannot be reconstructed clearly. On the other hand, transient convective flow can be reconstructed well using the real-time method. However, the fringe patterns reconstructed by the real-time method contain more noises, compared with the double-exposure method. Experimental results show a steady flow pattern at low Rayleigh numbers and a time-dependent periodic flow structure at high Rayleigh numbers. The periodic flow pattern at high Rayleigh numbers obtained by the real-time holographic interferometer method is in a good agreement with the PIV results.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2002년도 추계학술대회 논문집
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• pp.35-38
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• 2002

Variations of temperature and velocity fields in a Hele-Shaw Convection Cell (HSC) were measured using a holographic interferometry and PIV technique with varying Rayleigh number. Experimental results show a steady flow pattern at low Rayleigh numbers and a time-dependent periodic flow at high Rayleigh numbers. Two different measurement methods of holographic interferometry, double-exposure method and real-time method, were employed to measure the temperature field variations of HSC convective flow. In the double-exposure method, unwanted waves can be eliminated and reconstruction images are clear, but transient flow structure cannot be observed clearly. On the other hand, transient flow can be observed and reconstructed well using the real-time method. PIV results show that flow inside the HSC is periodic and the oscillating state is well matched with the temperature field results. The holographic interferometry and PIV techniques employed in this study are useful for analyzing the unsteady convective thermal fluid flows.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2006년도 추계학술대회 논문집
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• pp.78-85
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• 2006

Flows around two oscillating cylinders in side-by-side arrangement at Re=185 are simulated using immersed boundary method. The cylinders oscillate vertically with prescribed sinusoidal function in opposite directions in uniform cross-flow. Flow patterns and drag & lift forces are described by varying distance between two cylinders and oscillating frequency. Time series of flow patterns are investigated along with corresponding drag k lift coefficients.

• Journal of Mechanical Science and Technology
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• 제19권7호
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• pp.1517-1525
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• 2005

Liquid sloshing displays the highly nonlinear free surface fluctuation when either the external excitation is of large amplitude or its frequency approaches natural sloshing frequencies. Naturally, the accurate tracking of time-varying free surface configuration becomes a key task for the reliable prediction of the sloshing time-history response. However, the numerical instability and dissipation may occur in the nonlinear sloshing analysis, particularly in the long-time beating simulation, when two simulation parameters, the relative time-increment parameter a and the fluid mesh pattern, are not elaborately chosen. This paper intends to examine the effects of these two parameters on the potential-based nonlinear finite element method introduced for the large amplitude sloshing flow.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.530-535
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• 2001

Variations of temperature field in a Hele-Shaw convection cell (HSC) were measured using a holographic interferometry with varying Rayleigh number. Experimental results show a steady flow pattern at low Rayleigh numbers and a time-dependent periodic flow at high Rayleigh numbers. Especially, the period of oscillation at $Ra = 6.35{\times}10^6$ was 62 seconds. Two different measurement methods of holographic interferometry, double-exposure method and real-time method, were employed to measure the temperature field variations of HSC convective flow. In the double-exposure method, unwanted waves can be eliminated and reconstruction images are clear, but transient flow structure cannot be observed clearly. On the other hand, transient flow can be observed and reconstructed well using the real-time method. However, the fringe patterns reconstructed by the real-time method contain more noise, compared with the double-exposure method. The two holographic interferometer techniques employed complementary in this study were proved to be useful for analyzing the temperature field variations of unsteady thermal fluid flows.

• 대한기계학회논문집B
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• 제25권11호
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• pp.1624-1631
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• 2001

Variations of temperature field in a Hele-Shaw convection cell (HSC) were measured using a holographic interferometry with varying Rayleigh number. Experimental results show a steady flow pattern at low Rayleigh numbers and a time-dependent periodic flow at high Rayleigh numbers. Especially, the period of oscillation at Ra = 6.35 $\times$ 10$^{6}$ was 62 seconds. Two different measurement methods of holographic interferometry, double-exposure method and real-time method, were employed to measure the temperature field variations of HSC convective flow. In the double-exposure method, unwanted waves can be eliminated and reconstruction images are clear, but transient flow structure cannot be observed clearly. On the other hand, transient flow can be observed and reconstructed well using the real-time method. However, the fringe patterns reconstructed by the real-time method contain more noise, compared with the double-exposure method. The two holographic interferometer techniques employed complementary in this study were proved to be useful fur analyzing the temperature field variations of unsteady thermal fluid flows.

• 대한조선학회논문집
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• 제30권1호
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• pp.104-114
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• 1993

본 논문에서는 점성유동에 미치는 자유표면의 영향을 조사하기 위하여 자유표면을 수직으로 관통하는 원통 주위의 유동을 수치 시뮬레이션 하였다. 수치해석 방법으로서 Artificial Compressibility Method를 사용하였으며, 계산은 낮은 레이놀드수의 영역에 국한하였다. 계산결과는 자유표면에 가까운 유체영역에서 유선, 점성항력 등에 적지않은 영향이 있음을 보여주고 있다. 자유표면의 존재는 물체 후류 중의 와류를 물체로 부터 분리시키는 방향으로, 점성항력을 감소시키는 방향으로 작용하는 것으로 보인다.