• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2003년도 추계학술대회 논문집
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• pp.115-120
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• 2003

Flow characteristics at secondary recirculation zone in a liquid fuel ramjet combustor are investigated using CFD and 3-D Stereoscopic PIV method. The combustors have two rectangular inlets that form 90 degree each other. Three guide vanes were installed in each rectangular inlet to improve the flow stability. The tested angle of the air intakes was 60 degree. The experiments were performed in the water tunnel test with the same Reynolds number in the case of Mach0.3 at inlet. Both computational and experimental results showed the secondary recirculation flow occurred at the front junction of inlet main stream and combustor chamber. The size of secondary recirculation region increased with upon closer center of axial combustor. Since the performance of combustor depends on not only the main recirculation in the dome region but also the secondary recirculation flow in a junction region, the optimal angle of the air intakes should consider the recirculation size as frame holder.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.137-140
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• 2003

The flow characteristics of secondary recirculation region in a liquid fuel ramjet combustor are measured using PIV method. The model combustor has two rectangular inlets that form 90 degree angle each other. The tested angles of the air intakes were 30, 45 and 60. Three guide vanes are installed in each rectangular inlet to improve the flow stability. The experiments are performed in the water tunnel test with the same Reynolds number as the case of Mach 0.3 at the inlet. PIV software is developed to measure the characteristics of the flow field in the combustor. The accuracy of the developed PIV program is verified with rotating disk experiment and standard data. The experimental results show that the secondary recirculation flow occurred at the front junction of inlet main stream and combustorchamber. The size of secondary recirculation regions are increased with increasing air inlet angles. Since the performanceof combustor is very dependant on not only the main recirculation in the dome region but also the secondary recirculation flow in a junction region, the optimal angle of the air intakes should consider the both recirculation size as a frame holder.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.245-248
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• 2002

Vortex lock-on or resonance in the flow behind a circular cylinder is visualized by a time-resolved PIV when a single frequency oscillation is superimposed on the mean incident velocity. Measurements are made of the $K{\'{a}}rm{\'{a}}n$ vortices in the wake-transition regime at the Reynolds number 360. Basically, natural shedding state is observed to compare with lock-on state. Wake motion by the change of the shedding frequency of lock-on state is investigated. When lock-on occurs, the vortex shedding frequency is found to be half the oscillation frequency as expected from previous experiments. The physical flow phenomena of natural shedding and lock-on states are analyzed with physical parameters of recirculation and vortex formation region. Consequently, it is found that the change of wake bubble plays an important role in the flow at the lock-on state. Vortex formation region is also actively changed like recirculation region as the lock-on occurs. Therefore, it is deduced that the recirculation region is closely related with the vortex formation region.

• 한국가시화정보학회지
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• 제3권1호
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• pp.58-62
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• 2005

Flow characteristics at secondary recirculation zone in a liquid fuel ramjet combustor were investigated using CFD and Stereoscopic PIV method. The combustors have two rectangular inlets that form 90 degree each other. Three guide vanes were installed in each rectangular inlet to improve the flow stability. The tested angle of the air intakes was 60 degree. The experiments were performed in the water tunnel test with the same Reynolds number in the case of Mach 0.3 at inlet. The computational and experimental results showed that the secondary recirculation flow occurred at the front junction of inlet main stream and combustor chamber. The size of secondary recirculation regions are increased with approaching closer to the center of the combustor. Since the performance of combustor is closely dependent not only on the main recirculation in the dome region but also on the secondary recirculation flow in a junction region, the optimal angle of the air intakes should be considered the recirculation size as frame holder.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.499-505
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• 2001

The objective of the paper was to measure the pressure drop and to investigate the recirculation region of the conical orifices used in Kwang-yang Iron & Steel Company. The flow field with water used as a working fluid was the turbulent flow for Reynolds number of $2{\times}10^4$. The effective parameters for the pressure drop and the recirculation region were the conical orifice's inclined angle (${\theta}$) against the wall, the interval(L) between orifices, the relative angle of rotation(${\alpha}$) of the orifices, the shape of the orifice's hole(circle, rectangle, triangle) having the same area. It was found that the shape of the orifice's hole affected the pressure drop and the flow field a lot, But the other parameters did not make much differences to the pressure drop. The PISO algorithm with FLUENT code was employed.

• 태양에너지
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• 제8권2호
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• pp.57-65
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• 1988

The coefficients of convective heat transfer were investigated when air is jetted to surface of the heated side-wall. The temperature on the side-wall was measured when the offsets changed from 1.5 to 10.5 as 7 steps at the state of fixed Reynolds numbers that were 35000, 29000 and 23000. The experimental results are as follows: 1. The mean Nusselt number is very high on the surface of reattached flow region. 2. The offset and the recirculation flow region decreased, while the mean Nusselt number increased between the outlet of nozzle and the region of reattachment flow. 3. The local Nusselt number is not concerned with Reynolds number on the recirculation flow and on the reattached flow region when the offset decrease. But the Nusselt number increased only when Reynolds numbers on the wall jet flow region increased. 4. The mean and the maximum Nusselt number decreases linearly, and in particular its values rapidly decrease in accordance with changing of the offset from 1.5 to 3 in inverse proportion.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.692-697
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• 2000

Recently, Flat flame burners are hilighted in high-load burners. Our study contains flow field analysis of a flat flame burner. In this paper, We analyzed the direction and magnitude of the velocity in a round tile type burner with swirl angles, $10^{\circ},\;30^{\circ},\;50^{\circ}$. In the case of swirl angle $10^{\circ}$, because axial momentum is larger than radial momentum, Recirculation region was weakly developed. In the case of swirl angle $50^{\circ}$, Flow in front of the tile is distributed for radial direction. And Recirculation region is large. So, We expect that the radiation can be transmitted from tiles and the recirculation region may cause $NO_x$ reduction.

• Journal of Advanced Marine Engineering and Technology
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• 제33권6호
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• pp.912-917
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• 2009

An experimental flow visualization study of the entrance section of channels formed with wavy plates was made. The experiments were conducted in a water channel and a laser illuminated particle tracking was used as the technique of flow visualization. The flow region that were found in the experiments are steady, unsteady and significantly-mixed flows. Instabilities of the flow first appear near the exit of the channel. As the Reynolds number increases, the flows are characterized by the appearance of flow separation and the growth of recirculation region.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2005년도 추계학술대회 논문집
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• pp.28-35
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• 2005

Experiments were conducted to show the characteristics of the flow on triple parallel plane impinging jets. Measurements of mean velocity components and turbulent intensities were carried out with a particle image velocimetry(PIV) to investigate the flow field generated by the air issued from three identical plane parallel nozzles and mixed with the ambient air. The measurements range of these experiments were Reynolds number of 5000 and 1000 based on the nozzle width and the case of nozzle-to-plate distances were two times, six times and ten times the width of the nozzle. Results show that recirculation region of Re=5000 is the stronger than that of Re=1000. Therefore, velocity loss of centerline for Re=5000 that shows strongly recirculation region takes effect greatly.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2747-2752
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• 2007

A numerical study has been performed on the flow past a two-staged orifice in a rectangular duct. The flow field including the recirculation region behind the orifice was investigated and the pressure drop was calculated. Water was used as a working fluid and the flow was treated as the turbulent flow, of which the Raynolds number was 6000. The main parameters for the pressure drop and the recirculation region were the orifice's inclined angle against the duct, the interval between two orifices, the shape of the orifice's hole having the same area, and the change of the hole position at the same interval. The variation of the flow field was investigated with each parameter. Consequently, it was found that the most dominant parameter influencing the drop of the pressure was the change of the hole position at the same interval between orifices. Especially when the interval between orifices was narrow and the relative position the holes was changed, its effect to the flow field was shown most drastically as a result of this study. The SIMPLER algorithm with FLUENT code was employed to analyze the flow field.