• Title/Summary/Keyword: Throat Area

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Finite element analysis of the fluid-structure interaction in a compliant vessel (유연 혈관에서 유체-고체 상호작용에 대한 유한요소 해석)

  • Shim, Eun-Bo;Ko, Hyung-Jong;Kamm, Roger D.
    • Proceedings of the KSME Conference
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    • 2000.11b
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    • pp.591-596
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    • 2000
  • Flow through compliant tubes with linear taper in wall thickness is numerically simulated by finite element analysis. Two models are examined: a planar two-dimensional channel, and an axisymmetric tube. For verification of the numerical method, flow through a compliant stenotic vessel is simulated and compared to existing experimental data. Computational results for an axisymmetric tube show that as cross-sectional area falls with a reduction in downstream pressure, flow rate increases and reaches a maximum when the speed index (mean velocity divided by wave speed) is near unity at the point of minimum cross-section area, indicative of wave speed flow limitation or "choking" (flow speed equals wave speed) in previous one-dimensional studies. For further reductions in downstream pressure, flow rate decreases. Cross-sectional narrowing is significant but localized. When the ratio of downstream-to-upstream wall thickness is ${\le}$ 2 the area throat is located near the downstream end; as wall taper is increased to ${\ge}$ 3 the constriction moves to the upstream end of the tube. In the planar two-dimensional channel, area reduction and flow limitation are also observed when outlet pressure is decreased. In contrast to the axisymmetric case, however, the elastic wall in the two-dimensional channel forms a smooth concave surface with the area throat located near the mid-point of the elastic wall. Though flow rate reaches a maximum and then falls, the flow does not appear to be choked.

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Study of Ejector System for Pressure Recovery of Chemical Lasers (화학레이저 압력회복용 이젝터 시스템 연구)

  • 김세훈;김춘택;권세진
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2003.05a
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    • pp.49-53
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    • 2003
  • In this study, the geometric design parameters of ejector system were investigated. The critical parameters were primary nozzle area ratio, 2nd-throat cross sectional area and 2nd-throat L/D ratio. At every geometry cases, primary pressure and secondary pressure were measured simultaneously according to secondary mass flow rate. From the results, the ejector starting pressure, unstarting pressure and minimum secondary flow pressure were found and we got the effect of geometric parameters to ejector performance and the way to optimal design of ejector system for chemical lasers operating. Also the experiments of changing secondary flow temperature were carried out.

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An Investigation on Factors Influencing the Interrupting Performance using Gas Flow Analysis (파퍼식 가스차단기의 소호실 형상 변경에 의한 유동해석 비교)

  • Choi, Y.K.;Song, K.D.;Park, K.Y.;Yoon, C.Y.;Kang, J.H.
    • Proceedings of the KIEE Conference
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    • 1999.07a
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    • pp.349-350
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    • 1999
  • Two of the factors to be considered at the design stage of the extinction chamber have been examined numerically. one is the sectional area of puffer cylinder, another is that of nozzle throat. the variation of the sectional area of puffer cylinder allowed us to find the size optimal at the interrupting performance. it is shown that the sizes of nozzle throat influenced the pressure rise of puffer cylinder strongly.

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Numerical simulations of convergent-divergent nozzle and straight cylindrical supersonic diffuser

  • Mehta, R.C.;Natarajan, G.
    • Advances in aircraft and spacecraft science
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    • v.1 no.4
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    • pp.399-408
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    • 2014
  • The flowfields inside a contour and a conical nozzle exhausting into a straight cylindrical supersonic diffuser are computed by solving numerically axisymmetric turbulent compressible Navier-Stokes equations for stagnation to ambient pressure ratios in the range 20 to 34. The diffuser inlet-to-nozzle throat area ratio and exit-to-throat area ratio are 21.77, and length-to-diameter ratio of the diffuser is 5. The flow characteristics of the conical and contour nozzle are compared with the help of velocity vector and Mach contour plots. The variations of Mach number along the centre line and wall of the conical nozzle, contour nozzle and the straight supersonic diffuser indicate the location of the shock and flow characteristics. The main aim of the present analysis is to delineate the flowfields of conical and contour nozzles operating under identical conditions and exhausting into a straight cylindrical supersonic diffuser.

Numerical Analysis of Fluid Flow in a Regenerative Cooling Passage (재생냉각 유로 내의 유동에 관한 수치해석)

  • 조원국
    • Journal of the Korean Society of Propulsion Engineers
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    • v.4 no.1
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    • pp.46-52
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    • 2000
  • A computational analysis has been made on fluid flow in a regenerative cooling Passage for a reduced size liquid rocket engine to predict pressure drop and heat transfer rate in it. The contraction/expansion of the cross sectional area of the passage turn out to increases both the pressure loss and the heat transfer rate of the duct. The changes of the cross sectional area near the nozzle throat are effective to protect the throat which suffers from severe thermal load. Also given is the qualitative characteristics of the performance of the regenerative cooling system due to the variation of coolant flow rate.

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Effects of Pintle Shape on Nozzle Flow Characteristics of Variable Nozzle Throat Area Pintle Thrusters (핀틀 형상이 가변 노즐목 핀틀 추력기의 노즐 유동에 미치는 영향)

  • Lee, Yong-Wu;Huh, Hwan-Il
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2010.05a
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    • pp.275-278
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    • 2010
  • By changing the nozzle throat area during the operation, thrust of a pintle thruster can be adjusted easily such as a liquid propulsion. In this paper, numerical analysis was carried out for SNECMA's pintle thruster with different pintle shapes. Flow field and aerodynamic load changed drastically with pintle shapes. Bore in the pintle decreased aerodynamic load significantly.

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Steady State Experimental Study of Pintle Shape for Modulatable Thruster Applications (노즐목 가변 추력기 적용 목적의 핀틀 형상에 대한 정상상태 실험 연구)

  • Choi, Jae-Sung;Huh, Hwan-Il
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.04a
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    • pp.153-156
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    • 2011
  • Steady state experiment was carried out for modulatable thruster applications, with four different pintles. Results show that thrust can be modulated by changing nozzle throat area with pintle penetration. However, effect of pintle shape on the thruster performance is yet to be concluded.

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Review on the Globus Hystericus in View of Hyungsang Medicine (매핵기(梅核氣)의 형상의학적(形象醫學的) 고찰(考察))

  • Jung, Heung-Shik;Lee, Yong-Tae
    • Journal of Physiology & Pathology in Korean Medicine
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    • v.20 no.3
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    • pp.516-521
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    • 2006
  • The following conclusions are drawn from Hyungsang medicinal review on th globs hystericus through Donguibogam and other literatures. The globs hystericus appears in the throat and the epigastric region. It is a subjective sensation as if a plum pit is stick in the throat and is compressed, usually ac companied by stuffiness in chest, depression, nausea, and hiccup. But the throat is not marked with redness and swelling. Because Gi stagnation due to seven emotions is the main cause, the globs hystericus is usually followed by Seven Gi injuries, Pain and depressive syndrome due to disorder of Gi, palpitation due to fright, continuous violent palpitation, Gi phlegm, precordial pain with palpitation, epigastric pain due to seven emotions, cough and dyspnea due to disorder of Gi, and six kinds of stagnations. When head and body or chest and abdomen is compared to heaven and earth, the blockage of Gi between heaven and earth is common to the persons with the following charcteristics in Hyungsang; Dam type rather than Bankwang type, Gi type and Shin type rather than deer type and fish type, Taeum and Yangmyeong meridian types out of six meridian types, manly women, womanly man, too long or short neck, and signs of stagnation between the eyebrows. The globus hystericus needs, distinguishing from aphonia, acute tonsilitis, goiter, and pectorial pain with stuffiness. The affected area of aphonia and acute tonsilitis is the throat but they are not cause by the disturbance of seven emotions. Goiter can be distinguished by the changes in the appearance of neck. Even though the symptoms are similar, globus hystericus is caused by the stagnation of Gi, but the pectorial pain with stuffiness, by the insufficiency of the Heart blood. The general prescriptions are Chilgitang, Sachiltang, Gamisachiltang, Gamiijintang, and Sinihwan.

Effect of Venturi System on Acceleration of Low-speed Water Flow at the Venturi Throat Installed at the Inlet of Hydro Turbine

  • Jung, Sang-Hoon;Seo, In-Ho;Kim, Chul-Ho
    • Journal of Advanced Marine Engineering and Technology
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    • v.35 no.7
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    • pp.914-920
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    • 2011
  • For a hydro turbine electricity generation system in river or bay, a venturi system could be applied to accelerate flow speed at the inlet of the turbine system in a flow field. In this study, a steady flow simulation was conducted to understand the effect of venturi system on the acceleration of current speed at the inlet of a hydro turbine system. According to the continuity equation, the flow speed is inversely proportional to the cross-section area in a conduit flow; however, it would be different in an open region because the venturi system would be an obstruction in the flow region. As the throat area is 1/5 of the inlet area of the venturi, the flow velocity is accelerated up to 2.1 times of the inlet velocity. It is understood that the venturi system placed in an open flow region gives resistance to the upcoming flow and disperses the flow energy around the venturi system. The result of the study should be very important information for an optimum design of a hydro turbine electricity generation system.

Computational Study of the Axisymmetric, Supersonic Ejector-Diffuser Systems

  • Kim, Heuy-Dong;Lee, Young-Ki;Seo, Tae-Won;Raghunathan, Srinivasan
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.520-524
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    • 2000
  • A ejector system is one of the fluid machinery, which has been mainly used as an exhaust pump or a vacuum pump. The ejector system has often been pointed out to have only a limited efficiency because it is driven by pure shear action and the mixing action between primary and secondary streams. In the present work, numerical simulations were conducted to investigate the effects of the geometry and the mass flow ratio of supersonic ejector-diffuser systems on their mixing performance. A fully implicit finite volume scheme was applied to solve the axisymmetric Navier-Stokes equations, and the standard ${\kappa}-{\varepsilon}$ turbulence model was used to close the governing equations. The flow fields of the supersonic ejector-diffuser systems were investigated by changing the ejector throat area ratio and the mass flow ratio. The existence of the second throat strongly affected the shock wave structure inside the mixing tube as well as the spreading of the under-expanded jet discharging from the primary nozzle, and served to enhance the mixing performance.

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