• Journal of Advanced Marine Engineering and Technology
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• 제25권4호
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• pp.846-856
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• 2001

An experimental study has been made to investigate the effect on wake flow and vortex shedding frequency by vortex stabilizer in Karman vortex type air flow sensor. The conditions investigated include 3 types of shapes and 3 types of separation distances of the vortex stabilizer. The phase averaged technique and smoke-wire flow visualization method are used to understand the detail information. The rolling up position of shear layer is fixed by the influence of the vortex stabilizer. Especially, the convex type vortex stabilizer has shown the more stable repeatability and linearity regarding the vortex shedding frequency compared to the other types.

• 한국전산유체공학회지
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• 제14권3호
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• pp.76-85
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• 2009

The shock wave is deformed and the vortex is elongated simultaneously during the shock-vortex interaction. More precisely, the shock wave is deformed to a S-shape, consisting of a leading shock and a lagging shock by which the corresponding local vortex flows are accelerated and decelerated, respectively: the vortex flow swept by the leading shock is locally expanded and the one behind the lagging shock is locally compressed. As the leading shock escapes the vortex in the order of microseconds, the expanded flow region is quickly changed to a compression region due to the implosion effect. An induced shock is developed here and propagated against the vortex flow. This happens for a strong vortex because the tangential flow velocity of the vortex core is high enough to make the induced-shock wave speed supersonic relative to the vortex flow. For a weak shock, the vortex is basically subsonic and the induced shock wave is absent. For a vortex of intermediate strength, an induced shock wave is developed in the supersonic region but dissipated prematurely in the subsonic region. We have expounded these three shock-vortex interaction patterns that depend on the vortex flow regime using a third-order ENO method and numerical shadowgraphs.

• 한국분무공학회지
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• 제10권4호
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• pp.26-31
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• 2005

Today, the research to examine a fact that interaction between the air and the fluid free surface affects the steady state flow and air. We proved the interaction between vortex pairs and free surface on each condition that is created by the end of delta wings. Another purpose of this study is to investigate the effect of surface active material which call change the surface tension and we must consider when we refer to turbulent flow on surface tension. Therefore, this research examined the growth process of vortex pairs on condition of clean, contaminated free surface and wall after we made vortex pairs through counter rotating flaps. The results of this study suggest that vortex pairs in clean free surface rise safely but the vortex pairs in contaminated free surface and rigid, no slip is made secondary vortex or rebounding. However the secondary vortex in rigid, no slip is stronger than before. and we can find the vortex shape which roll up more completely. However, these will disappear by the effect of wall.

• 한국안전학회지
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• 제14권1호
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• pp.3-9
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• 1999

The vortex tube is a simple device which splits a compressed gas stream into a cold stream and a hot stream without any chemical reactions. Recently, vortex tube is widely used to local cooler of industrial equipments and air supply system. In this study, the insulation effect of surface on the efficiency of vortex tube was performed experimentally. The experiment is carried out for nozzle area ratio of 0.194, diameter ratio of cold end orifice of 0.6 and input pressure ranging from 0.2Mpa to 0.5Mpa. The purpose of this study is focused on the effect of surface insulation of vortex tube with the variation of cold air mass flow ratio. The results indicate that the temperature difference of cold and hot air are higher about 12% and 30% than that of not insulated vortex tube respectively. Furthermore, for the insulated vortex tube, the similarity relation for the prediction of cold end temperature as the function of cold air mass flow ratio and input pressure is obtained.

• 설비공학논문집
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• 제12권8호
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• pp.703-710
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• 2000

Energy separation characteristic occurring in a counterflow vortex tube was studied experimentally, where air, $C_2$, and R22 were used as working fluids. The experiments were carried out with pressure ratio from 3 to 8 and cold mass fraction(y) from 0.1 to 0.9. As results, Ranque-Hilsch effect showed different results from adiabatic expansion process. Temperature difference in vortex tube outlet was affected by Joule-Thomson effect as well as Ranque-Hilsch effect. The more effective the energy separation was, the more increased the entropy in the cold oulet of vortex tube was.

• 설비공학논문집
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• 제25권2호
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• pp.94-100
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• 2013

A convergent-divergent nozzle or venturi nozzle has been used to accelerate the wind speed at its throat. The wind speed at the throat is inversely proportional to its area according to the continuity equation. In this numerical study, an airflow phenomena in the venturi system placed at a vertical structure was investigated to understand the vortex effect occurred at the rear-side of the vertical structure on the air speed increment at the throat of the venturi system. For this study, a venturi system sized by $20(m){\times}20(m){\times}6(m)$ was modelled and the area ratio(AR) of the model venturi was 2.86. To see the vortex effect on the air flow acceleration in the venturi throat, two different boundary conditions was defined From the study, it was found that the pressure coefficient(CP) of the venturi system with the vortex formed at the exit of the venturi was about 2.5times of the CP of the venturi system without the vortex effect. The velocity increment rate of the venturi system with the vortex was 61% but 9.5% only at the venturi system without the vortex. Conclusively, it can be said that the venturi system installed in a vertical structure has very positive effect on the flow acceleration at its throat due to the vortex formed at the rear-side of the vertical structure.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2002년도 추계학술대회 논문집
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• pp.67-72
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• 2002

Today, the research to examine a fact that interaction between the air and the fluid free surface affects the steady state flow and air. We proved the interaction between vortex pairs and free surface on each condition that is created by the end of delta wings. another purpose of this study is to investigate the effect of surface active material which can change the surface tension and we must consider when we refer to turbulent flow on surface tension. therefore, this research examined the growth process of vortex pairs on condition of clean, contaminated free surface and wall after we made vortex pairs through counter rotating flaps. The results of this study suggest that vortex pairs in clean free surface rise safely but the vortex pairs in contaminated free surface and rigid, no slip is made secondary vortex or rebounding. However the secondary vortex in rigid, no slip is stronger than before, and we can find the vortex shape which roll up more completely. However, these will disappear by the effect of wall.

• 대한기계학회논문집B
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• 제31권1호
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• pp.8-15
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• 2007

The jet impingement cooling characteristics are investigated experimentally. The study is motivated by the potential application of local hot spot cooling by means of the vortex tube. The purposes of this research are to examine the effect of the nozzle-block spacing and flow rate. The results of jet through vortex tube is compared with ones of circular Jet. Flow visualization by the smoke-wire technique is also performed to investigate the flow structure. As the nozzle-block spacing is increased and flow rate decreased, the cooling effect of the Jet through the vortex tube decreases mere remarkably than that of the circular jet. So the cooling effect for the jet through the vortex tube is higher than that for the circular jet at $H/D{\leq}3$, $Q{\geq}10m^3/h$.

• Journal of Magnetics
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• 제13권4호
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• pp.157-159
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• 2008

The effect of the perpendicular field on the trajectory of a vortex core driven by spin-transfer torque was investigated using micromagnetic simulations. The trajectory of the vortex core was staggered due to distortions of the moving vortex core. The core trajectory was affected by both the perpendicular field and ${\beta}$ value, which is the relative magnitude of nonadiabatic spin torque to the adiabatic spin torque. This suggests that the effect of the perpendicular field should be considered when examining a vortex core trajectory affected by ${\beta}$.

• 대한기계학회논문집B
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• 제36권12호
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• pp.1161-1169
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• 2012

지면효과를 받는 3차원 대칭단면 날개(NACA0015)의 공력특성과 끝단와(wing-tip vortex)의 거동에 관하여 수치적 연구를 수행하였다. 날개가 지면에 근접함에 따라 공기 역학적 특성과 끝단와의 거동은 두 가지 상이한 현상(지면효과와 벤츄리효과)에 의하여 영향을 받는다. 지면효과는 양력을 증가시키며 항력을 감소시켜 공기역학적 특성을 향상시키는 반면 벤츄리효과는 음의 양력을 만들고 항력을 급격히 증가시킨다. 대칭형 익형은 받음각에 따라 이러한 현상이 모두 나타난다. NACA0015의 경우 받음각이 4도 보다 작은 경우 벤츄리효과가 지배적이며 받음각이 이 보다 큰 경우 지면효과가 지배적으로 나타난다. 특이하게 4도에서는 이 두 가지 현상이 모두 나타났다. 벤츄리효과가 지배적인 경우 지면과 날개 사이의 흡입현상의 증가로 인하여 끝단와는 날개의 안쪽으로 끌려 들어오는 반면 지면효과가 지배적인 경우 끝단와는 날개의 바깥쪽으로 밀려나가는 현상을 알 수 있었다.