• Title/Summary/Keyword: Jet Velocity Distribution

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Characteristics of Thickness and Velocity of the Liquid Sheet Formed by Two Impinging Jets Considering Jet Velocity Profile (충돌 제트 속도 분포를 고려한 액막의 두께와 속도 특성)

  • Choo, Y.J.;Kang, B.S.
    • Journal of ILASS-Korea
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    • v.12 no.2
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    • pp.79-85
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    • 2007
  • In this study, the effect of jet velocity profile on the thickness and velocity of the liquid sheet formed by two impinging low speed jets was investigated. To predict the distribution of thickness and velocity of liquid sheet theoretically, the jet velocity profile which was measured experimentally was adopted in addition to the constant jet velocity as well as Poiseuille's parabolic profile. For three cases, the distribution of thickness and velocity of liquid sheet was analytically predicted by solving conservation equations including stagnation point. The predicted results were compared with previous experimental results. The jet velocity profile definitely affected the resulting characteristics of liquid sheet. The distribution of thickness and velocity of liquid sheet was more close to the measured results compared with that which was predicted by the assumption of constant jet velocity.

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A study on the Velocity Distribution of the Liquid Sheet Formed by Two Impinging Jets at Low Velocities (저속 충돌제트에 의해 형성되는 액막의 속도 분포에 관한 연구)

  • Choo, Yeon-Jun;Kang, Bo-Seon
    • Journal of ILASS-Korea
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    • v.5 no.1
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    • pp.41-48
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    • 2000
  • In this research, the velocity distribution of the liquid sheet formed by two impinging jets at low velocities are measured using LDV. The spatial distribution of the sheet velocity as well as the effects of impinging anlge and jet velocity on the sheet velocity are examined. The sheet velocity is highest along the sheet axis and it decreases with the increase of the azimuthal angle. With the increase of the impinging angle, the average sheet velocity is decreased due to the increased impact momentum. The average sheet velocity is proportional to the jet velocity but it is always higher than the jet velocity. This result is against the fact that the sheet velocity can be assumed to be equal to the jet velocity in the previous researches.

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A study on the Velocity Distribution of the Liquid Sheet Formed by Two Impinging Jets at Low Velocities (저속 충돌제트에 의해 형성되는 액막의 속도 분포에 관한 연구)

  • Choo, Yeon-Jun;Kang, Bo-Seon
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.728-733
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    • 2000
  • In this research, the velocity distribution of the liquid sheet formed by two impinging jets at low velocities are measured using LDV. The spatial distribution of the sheet velocity as well as the effects of impinging angle and jet velocity are examined. The sheet velocity is the highest along the sheet axis and it decreases with the increase of the azimuthal angle. With the increase of the impinging angle, however, the difference of sheet velocity on the liquid sheet is decreased. The average sheet velocity is proportional to the jet velocity but it is always higher than the jet velocity as against the fact that the sheet velocity can be assumed to be equal to the jet velocity in the previous researches.

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Analysis of Velocity Structure of Round Wall Jet (원형바닥젵의 유속구조 해석)

  • Kim, Dae-Geun;Seo, Il-Won
    • Journal of Korea Water Resources Association
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    • v.30 no.5
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    • pp.467-475
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    • 1997
  • In this study, breakwater model which has several outlet pipes to discharge heated water is settled in the experimental open channel and velocity distribution of wall jet is measured. Numerical simulation of velocity structure of wall jet using 3-dimensional computer model. Fluent model, is also carried out. The calculated results are verified with the experimental results and the flow characteristics of wall jet are investigated. The length of zone of flow establishment of wall jet is shorter than that of free jet, and the diminution rate of jet centerline longitudinal velocity is larger than that of free jet. Characteristics of buoyant jet and non-buoyant simple jet simulated by Fluent model are compared. Near the outlet pipe, in the region where x/lQ is over 15, this is reversed. Comparison of vertical distribution of longitudinal velocity shows that positive velocity of non-buoyant jet is bigger than that of buoyant jet in the bottom layer and in the upper layer, negative velocity of non-buoyant jet is bigger too. Flow separation in free surface of the buoyant jet occurs in smaller distances from the outlet than the non-buoyant jet. Buoyant jet expands faster than the non-buoyant jet in vertical direction.

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The effect of the nozzle exit geometry on the flow characteristics of the free condensing jet

  • Jaewon Myeong;Seungwan Kim;Dehee Kim;Jongtae Kim;Weon Gyu Shin
    • Nuclear Engineering and Technology
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    • v.56 no.7
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    • pp.2545-2556
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    • 2024
  • In the present study, we investigated the velocity distribution, temperature distribution and condensation characteristics of steam jet issuing from four different orifice nozzles with a Reynolds number of approximately 79,000 using the phase Doppler particle analyzer system and a K-type thermocouple. The steam jet discharged from the orifice nozzle has a wider jet width compared to pipe nozzle because of the vena-contracta which can enhance the mixing of steam jet with the ambient air. Therefore, the orifice jet showed less condensation due to its wideness, resulting in small velocity decay rate and large temperature decay rate due to momentum conservation and decreased latent heat release compared to pipe nozzle, respectively. Also, the wider jet width of the orifice jet resulted in larger velocity and temperature spread rate compared to the pipe jet. In addition, the increase in the aspect ratio of the orifice jet led to more condensation and larger velocity spread rate and temperature spread rate due to both the vena-contracta and axis-switching effect, resulting in the increase of jet entrainment.

Effect of Circumferential Velocity from Guide Vane on the Nozzle Flow of a Jet Fan (제트팬 노즐내부 유동에 대한 고정익 출구 원주속도의 영향)

  • 최충현;이재헌
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.3
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    • pp.209-216
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    • 2001
  • A numerical study is peformed to investigate the effect of circumferential velocity generated by the guide vane on the nozzle flow of a jet fan, s a way of increasing the penetration force of jet fan with nozzle of 175mm diameter. For the validation of numerical results. the velocity is measured by a 5-hole pitot tube and flow visualization is conducted by the tuft method. Under the inlet condition that the maximum circumferential velocity in the stator outlet of the present jet fan is 1.8m/s, the axial velocity in the nozzle outlet has the feature that the velocity at the axis is low and the velocity near the wall high. Therefore, to increase the throw length of the jet fan, the configuration of the fairing and nozzle needs to be developed and the precise revise of the stator angle is required, In addition, the bigger the circumferential velocity, the smaller the axial velocity at the axis and the bigger non-uniformity of the flow distribution.

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Experimental Study of Molten Wood's Metal Jet Breakup in Subcooled Water (과냉각수조 내의 제트에 의한 용융우드메탈 미립화에 관한 실험적 연구)

  • Heo, Hyo;Jerng, Dong Wook;Bang, In Cheol
    • Journal of ILASS-Korea
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    • v.19 no.4
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    • pp.197-203
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    • 2014
  • The liquid jet breakup has been studied in the areas such as aerosols, spray and combustion. The breakup depends on several physical parameters such as the jet velocity, the nozzle inner diameter, and the density ratio of the water to the jet. This paper deals with characteristics of the jet breakup according to the jet velocity and the nozzle diameter. In order to consider only hydrodynamic factors, all the experiments were conducted in non-boiling conditions. The jet behavior in the water pool was observed by high-speed camera and PIV technique. For the condition of the inner diameter of 6.95 mm and the jet velocity of 2.8 m/s, the debris size of 22 mm gave the largest mass fraction, 39%. For higher jet velocity of 3.1 m/s, the debris size of 14 mm gave the largest mass fraction, 36%. For the nozzle with inner diameter of 9.30 mm, the debris size distribution was different. For jet velocity of 2.8 m/s and 3.1 m/s, the debris size with the largest mass fraction was found to be 14 mm. It was identified that the debris size decreased as the diameter or the jet velocity increased.

Turbulent Flow Field Structure of Initially Asymmetric Jets

  • Kim, Kyung-Hoon;Kim, Bong-Whan;Kim, Suk-Woo
    • Journal of Mechanical Science and Technology
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    • v.14 no.12
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    • pp.1386-1395
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    • 2000
  • The mear field structure of round turbulent jets with initially asymmetric velocity distributions is investigated experimentally. Experiments are carried out using a constant temperature hot-wire anemometry system to measure streamwise velocity in the jets. The measurements are undertaken across the jet at various streamwise stations in a range starting from the jet exit plane and up to a downstream location of twelve diameters. The experimental results include the distributions of mean and instantaneous velocities, vorticity field, turbulence intensity, and the Reynolds shear stresses. The asymmetry of the jet exit plane was obtained by using circular cross-section pipes with a bend upstream of the exit. There pipes used here include a straight pipe, and 90 and 160 degree-bend pipes. Therefore, at the upstream of the upstream of the pipe exit, secondary flow through the bend mean streamwise velocity distribution could be controlled by changing the curvature of pipes. The jets into the atmosphere have two levels of initial velocity skewness in addition to an axisymmetric jet from a straight pipe. In case of the curved pipe, a six diameter-long straight pipe section follows the bend upstream of the exit. The Reynolds number based on the exit bulk velocity is 13,400. The results indicate that the near field structure is considerably modified by the skewness of an initial mean velocity distribution. As the skewness increases, the decay rate of mean velocity at the centerline also increases.

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NUMERICAL ANALYSIS FOR 2-D FREE JET FLOW BY SMAC SCHEME (SMAC법에 의한 2차원 자유분류의 수치해석)

  • Jung, S.H.;An, Y.J.;Shin, B.R.
    • 한국전산유체공학회:학술대회논문집
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    • 2009.04a
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    • pp.298-302
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    • 2009
  • Numerical analysis of two dimensional incompressible laminar free jet flow was carried out by using finite difference SMAC scheme. Flow characteristics of free jet flow such as jet width, similarity of jet velocity and hypothetical origin were investigated for different Reynolds numbers of Re=30 and 100. The reliability of predictions were confirmed by comparison with exact solution. Non-dimensional velocity distribution showed similarity of jet flow velocity after initial region. In the region of laminar flow, the location of hypothetical origin becomes more distant with Reynolds number.

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Heat transfer and flow characteristics of sweeping jet issued from rectangular nozzle with thin plate (박판이 부착된 사각노즐에서 분사되는 Sweeping jet의 유동 및 열전달 특성)

  • Kim, Donguk;Jung, Jae Hoon;Seo, Hyunduk;Kim, Hyun Dong;Kim, Kyung Chun
    • Journal of the Korean Society of Visualization
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    • v.17 no.2
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    • pp.58-66
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    • 2019
  • This study investigated heat transfer and flow characteristics of a sweeping jet issued from a rectangular nozzle with a thin plate. A thin vertical aluminum plate was attached on outlet of fluidic oscillator to increase velocity of central area with Coanda effect and enhance heat transfer performance. From visualization and PIV experiments, sweeping jet with a thin plate has larger velocity distribution in center region than that of the normal sweeping jet while oscillating frequency is similar as the normal one. Thermographic phosphor thermometry method was used to visualize the temperature field and Nu distribution of plate with impinging sweeping jet with thin plate. Four Reynolds numbers and three jet-to-wall distances were selected as parameters. It is found that heat transfer performance in the low jet-to-wall spacing was enhanced as the cooled area was expanded. However, when the jet-to-wall spacing became greater than 8dh, heat transfer performance became similar due to reduced impinging velocity.