• Title/Summary/Keyword: flow contraction

검색결과 254건 처리시간 0.023초

A study on the pressure loss coefficient of non-Newtonian fluids in the stenotic tubes (비뉴턴 유체의 협착관내 압력손실계수에 관한 연구)

  • Seo, Sang-Ho;Yu, Sang-Sin;Jang, Nam-Il
    • Transactions of the Korean Society of Mechanical Engineers B
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    • 제20권5호
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    • pp.1603-1612
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    • 1996
  • The pressure loss coefficient of Newtonian and non-Newtonian fluids such as water, aqueous solutions of Carbopol-934 and Separan AP-273 and blood in the stenotic tubes are determined experimentally and numerically. The numerical analyses for flows of non-Newtonian fluids in the stenotic tubes are conducted by the finite element method. The effect of the contraction ratio and the ratio of length to diameter on the pressure drop are investigated by the experiments and numerical analysis. The pressure loss coefficients are significantly dependent upon the Reynolds number in the laminar flow regime. As Reynolds number increases, the pressure loss coefficients of both Newtonian and non-Newtonian fluids decrease in the laminar flow regime. As the ratio of length to diameter increases the maximum pressure loss coefficient increases in the laminar flow regime for both Newtonian and non-Newtonian fluids. Newtonian fuid shows the highest values of pressure loss coefficient and blood the next, followed by Carbopol solution and Separan solution in order. Experimental results are used to verify the numerical analyses for flows of Newtonian and non-Newtonian fluids. Numerical results for the maximum pressure loss coefficient in the stenotic tubes are in fairly good agreement with the experimental results. The relative differences between the numerical and experimental results of the pressure loss coefficients in the laminar flow regime range from 0.5% to 14.8%.

The Flow Variation due to Pier Construction at Kwangyang Bay (컨테이너 부두건설에 따른 광양만의 유황변동)

  • Choi, Song Yeol;Cho, Won Cheol;Lee, Won Hwan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • 제12권3호
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    • pp.115-125
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    • 1992
  • The variation of flow pattern caused by the topographical change of Kwangyang bay, is analyzed using the numerical tidal model for the depth-integrated two- dimensional long wave equation. The results of study are as follows. Due to pier construction, the area of water surface is deceased and the water inflow into the Kwangyang bay is reduced. For this result, at the outer bay of Myo island, the tidal range is slightly increased. And at the inner bay, water level is dropped generally, and especially at the time of low water tide, the phenomena of water level drop obviously appears. According to the variation pattern, flow velocities is lower than those of non-construction condition over the Kwangyang bay. But at the channel(from Kwangyang east stream) flowing into the east Kwangyang bay, for the contraction of channel profile, flow velocity is increased. The study based on the 100 year frequency design flood discharge from Sueocheon(river) and Dongcheon(river) which are flowing into the bay and Seomjin River flowing along the boundary of the bay is also performed. During the spring tide condition, the results showed the rise of water level about 1.2 m at Seomjin River Estuary and 0.3 m at inner bay is occurred.

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An Analysis on the Characteristics of Separation Zone Due to a Bed Discordance at Confluence (합류부 하상고 불일치에 의한 분리구역 특성분석)

  • Choi, Heung Sik;Mo, Sun Jea
    • Journal of Korea Water Resources Association
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    • 제48권8호
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    • pp.625-634
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    • 2015
  • The diverse patterns of separation zone according to the marked bed discordance by dredging at confluence in addition to the confluence angle of tributary and discharge ratio between tributary and main channels have been analyzed by CCHE2D model simulation. The separation zone is defined by inside of zero velocity boundary at down-stream of confluence. The separation zone dose not formed at the $30^{\circ}$ of confluence angle of tributary. The size of separation zone increases as the discharge ratio and confluence angle increase in general. The separation zone decreases as the dredging depth increases which shows the relative momentum reduction compared by the flow volume increasing by dredging at confluence. The contraction factor with the variation of confluence angle and discharge ratio has been investigated and confirmed the corresponding conveyance decreasing results in backwater effect. The regression equation of shape factor with confluence angle and discharge and dredging depth ratios has been suggested.

PIV Aanalysis of Vortical Flow behind a Rotating Propeller in a Cavitation Tunnel (캐비테이션 터널에서 PIV를 이용한 프로펠러 후류 보오텍스 유동계측 및 거동해석)

  • Paik, Bu-Geun;Kim, Jin;Park, Young-Ha;Kim, Ki-Sup;Kim, Kyoung-Youl
    • Journal of the Society of Naval Architects of Korea
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    • 제42권6호
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    • pp.619-630
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    • 2005
  • A two-frame PIV (Particle Image Velocimetry) technique is used to investigate the wake characteristics behind a marine propeller with 4 blades at high Reynolds number. For each of 9 different blade phases from $ 0^{\circ} $ to $ 80^{\circ} $, one hundred and fifty instantaneous velocity fields are measured. They are ensemble averaged to study the spatial evolution of the propeller wake in the region ranging from the trailing edge to one propeller diameter (D) downstream location. The phase-averaged mean velocity shows that the trailing vorticity is related to radial velocity jump, and the viscous wake is affected by boundary layers developed on the blade surfaces and centrifugal force. Both Galilean decomposition method and vortex identification method using swirling strength calculation are very useful for the study of vortex behaviors En the propeller wake legion. The slipstream contraction occurs in the near-wake region up to about X/D : 0.53 downstream. Thereafter, unstable oscillation occurs because of the reduction of interaction between the tip vortex and the wake sheet behind the maximum contraction point.

Numerical Study on Propeller Cavitation and Pressure Fluctuation of Model and Full Scale ship for a MR Tanker (MR Tanker 실선 및 모형선 프로펠러 캐비테이션 및 변동압력 수치해석 연구)

  • Park, Il-Ryong;Kim, Ki-Sup;Kim, Je-In;Seol, Han-shin;Park, Young-Ha;Ahn, Jong-Woo
    • Journal of the Society of Naval Architects of Korea
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    • 제57권1호
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    • pp.35-44
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    • 2020
  • Propeller cavitation extent, pressure fluctuation induced by cavitation, pressure distribution on propeller blade, total velocity distribution and nominal wake distribution for a MR Taker were computed in both conditions of model test and sea trial using a code STAR-CCM+. Then some of the results were compared with model test data at LCT and full-scale measurement (Ahn et al (2014); Kim et al (2014)] in order to confirm the availability of a numerical prediction method and to get the physical insight of local flow around a ship and propeller. The nominal wake distributions computed and measured by LDV velocimeter on the variation of on-coming velocity show the wake contraction characteristics proposed by Hoekstra (1974). The numerical prediction of propeller cavitation extent on a blade angular position and pressure fluctuation level on each location of pressure sensors are very similar with the experimental results.

Concentration Gradient Effects on Liftoff Characteristics of Triple Flame on a Slot Burner (슬롯 버너에서 농도 구배가 삼지 화염의 부상 특성에 미치는 영향)

  • Seo, Jeong-Il;Kim, Nam-Il;Shin, Hyun-Dong
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2002년도 제24회 KOSCO SYMPOSIUM 논문집
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    • pp.99-105
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    • 2002
  • The concentration gradient effects on triple flame have been studied experimentally using a slot burner in order to stabilize stationary triple flame in coflowing stream. By means of contraction we generate the coflowing stream with uniform velocity and linear concentration gradient at the outlet of the slot. In this paper we investigated the response of the triple flame. to the concentration gradient, like the stability, the liftoff height, and the structure of triple flame. Flow velocity is measured with Laser Doppler Velocimetry. As the concentration gradient increases. the flame propagation velocity in immediately upstream triple point increases until the liftoff height of triple flame becomes minimum, and then decreases.

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Preliminary Experimental Results of Pressure Control for Modulatable Thruster Applications (노즐목 가변 추력기의 압력제어 기법에 관한 예비실험 결과)

  • Choi, Jae-Sung;Huh, Hwan-Il
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 한국추진공학회 2011년도 제37회 추계학술대회논문집
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    • pp.18-21
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    • 2011
  • In this study, basic research on the pressure control using driven pintle of modulatable thruster is presented. For this purpose, pintle thruster and pintle shape was developed. The actuator model was selected by calculating pintle load using Fluent software. Preliminary unsteady experimental results show that huge pressure oscillation is occurred as the pintle approach toward nozzle wall. From the preliminary experimental results, we could see possibility of pressure control of the modulatable thruster.

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Automatic Estimation of 2D Facial Muscle Parameter Using Neural Network (신경회로망을 이용한 2D 얼굴근육 파라메터의 자동인식)

  • 김동수;남기환;한준희;배철수;권오흥;나상동
    • Proceedings of the IEEK Conference
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    • 대한전자공학회 1999년도 하계종합학술대회 논문집
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    • pp.1029-1032
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    • 1999
  • Muscle based face image synthesis is one of the most realistic approach to realize life-like agent in computer. Facial muscle model is composed of facial tissue elements and muscles. In this model, forces are calculated effecting facial tissue element by contraction of each muscle strength, so the combination of each muscle parameter decide a specific facial expression. Now each muscle parameter is decided on trial and error procedure comparing the sample photograph and generated image using our Muscle-Editor to generate a specific face image. In this paper, we propose the strategy of automatic estimation of facial muscle parameters from 2D marker movement using neural network. This also 3D motion estimation from 2D point or flow information in captered image under restriction of physics based face model.

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Pharmacological Studies of Scolopendra subspinipes mutilans $L.\;K_{OCH}$ (노랑머리지네의 약리학적(藥理學的) 연구(硏究))

  • Hong, Nam-Doo
    • Korean Journal of Pharmacognosy
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    • 제7권2호
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    • pp.99-109
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    • 1976
  • Scolopendra corpus has been used as anticonvulsants and antispasmodics in the oriental medicine. It was previously shown that water extract of Scolopendra corpus had an inhibitory action on ileum in mouse. To investigate the anticonvulsant and antispasmodic activity of Scolopendra corpus, pharmacological studies have been carried out with the water extract of Scolopendra subspinipes mutilans $L.\;K_{OCH}$, which is widely distributed in Korea. 1. The extract depressed convulsions induced by picrotoxin and strychnine. 2. Sedative and antipyretic analgesic action were observed. 3. In mouse and rabbit, tone of intestinal smooth muscle was suppressed with the treatment of the extract and intestinal contraction induced by $BaCl_2$ was also inhibited, suggesting that the extract has a papaverine-like effect. Whereas, in guinea pig, intestinal and tracheal smooth muscle were stimulated, and the effect was antagonized by pre-and after-treatment of diphenhydramine, suggesting that the extract has a histamine-like effect. 4.Flow rate was increased when hind-limb of Toad was perfused with saline containing the extract, but returned to normal within 10 min. Hypotensive effect was observed in rabbit and the effect was abolished by vagotomy.

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A Study on the Development and Application of a Design Program for Centrifugal Turbo Fan (원심 터보홴 설계용 프로그램의 개발 및 응용에 대한 연구)

  • Kim, Jang-Kweon;Oh, Seok-Hyung
    • Journal of Power System Engineering
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    • 제20권6호
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    • pp.71-79
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    • 2016
  • This paper introduces the design method of the centrifugal turbo fan and the process of developing the design program of it. The developed design program confirmed the applicability by experimental performance data. Here, we proposed new velocity coefficients and considered various losses such as impeller inlet loss, vane passage flow loss, casing pressure loss, recirculation loss power, and disk friction loss power. Especially, the inlet and outlet widths of the impeller were newly determined by reflecting the experimental results. As a result, this fan design program shows a good performance result regardless of the types of impeller and is expected to be a very useful design tool.