• Title/Summary/Keyword: Velocity Particle

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Review of stability calculation of an artificial reef in the breaking wave zone of coastal waters (천해 쇄파역에서 인공어초 안정성 계산에 대한 고찰)

  • Kim, Chang-Gil;Oh, Tae-Gun;Suh, Sung-Ho;Kim, Dae-Kweon;Kim, Byung-Gyun;Choi, Yong-Suk
    • Journal of Advanced Marine Engineering and Technology
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    • v.33 no.6
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    • pp.965-974
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    • 2009
  • The current study reviews the formula used to calculate the stability of an artificial reef in the breaking wave zone of coastal waters. A comparison was carried out between the existing formula and a new formula that takes into account the water particle velocity in the breaking wave zone. Water particle velocity was analyzed using the Fluent (CADMAS-SURF) software program. The new formula took into various factors, including the difference in the drag coefficient due to the direction of the current and the ratio of distance between two reefs. The drag coefficient of the artificial reef due to the direction of the current was 0.84 when the distance ratio was 0.5. When the artificial reef was placed at 45 degree angle to the current, the product of the drag coefficient and the project area were 40 to 46 % greater than when the reef was placed at 90 degree angle. Our results regarding the stability of an artificial reef indicate that the new formula provides the designers of artificial reefs with a more rational and economic design rationale rather than the existing formula.

A Study of Mixing Characteristics for Cosmetic Pine Powder (화장품용 미분체 혼합공정에서의 분산특성 연구)

  • 이종옥;송건응
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.19 no.1
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    • pp.85-107
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    • 1993
  • The cosmetic fine powders were mixed with variation of mixing time(5) in the mixers (ribbon mixer, powder mixer, micropulverizer and fine impact mill). The powders were nixed with small amount of ferric oxide. as tracer. The mixed powders ere measured the particle size distribution, specific surface area and surface color with mixing time (s). The color variation, particle size distribution and specific surface area of the mixed powder exist a relationship with mining time(s) that can be expressed as mathematical equations to show the degree of the mixing of the powder mixture. The linear velocity of the impellar tip is the main factor contributing to he mixing efficiency of the mixers un this study. According to the linear velocity, he mixers used are devieded as convection mixing (ribbon mixer), sclera mixing powder mixer) and diffusion mixing (micropulverizer/fine impact mill).

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Particle filter approach for extracting the non-linear aerodynamic damping of a cable-stayed bridge subjected to crosswind action

  • Aljaboobi Mohammed;Shi-Xiong Zheng;Al-Sebaeai Maged
    • Wind and Structures
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    • v.38 no.2
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    • pp.119-128
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    • 2024
  • The aerodynamic damping is an essential factor that can considerably affect the dynamic response of the cable-stayed bridge induced by crosswind load. However, developing an accurate and efficient aerodynamic damping model is crucial for evaluating the crosswind load-induced response on cable-stayed bridges. Therefore, this study proposes a new method for identifying aerodynamic damping of the bridge structures under crosswind load using an extended Kalman filter (EKF) and the particle filter (PF) algorithm. The EKF algorithm is introduced to capture the aerodynamic damping ratio. PF technique is used to select the optimal spectral representation of the noise. The effectiveness and accuracy of the proposed solution were investigated through full-scale vibration measurement data of the crosswind-induced on the bridge's girder. The results show that the proposed solution can generate an efficient and robust estimation. The errors between the target and extracted values are around 0.01mm and 0.003^o, respectively, for the vertical and torsional motion. The relationship between the amplitude and the aerodynamic damping ratio is linear for small reduced wind velocity and nonlinear with the increasing value of the reduced wind velocity. Finally, the results show the influence of the level of noise.

A Numerical Study on Evaporation of Sludge Particles in a Sludge Dryer (열건조기내에서 슬러지 입자의 증발현상에 관한 수치해석 연구)

  • Ku, Bon-Ki;Kim, Sang-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.8
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    • pp.1064-1072
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    • 1998
  • The evaporation of sludge particles in a sludge dryer has been numerically investigated with commercial CFX4.1 code. Gas flow field, gas temperature field, sludge particle trajectories, and the moisture content variation of sludge particles are calculated fort various influencing factors, i. e., gas swirl velocity, initial particle distribution, gas temperature. Evaporation of sludge particles increases with gas swirl velocity, several supplying positions, and gas temperature, respectively due to increased residence time, increased contacting surface area, and increased temperature difference between gas and particle.

A Study on the Flow Characteristics of the Triple Jets Using Particle Image Velocimetry (PIV를 이용한 삼중 제트의 유동 특성에 관한 연구)

  • Lee Myung Jae;Yoon Soon Hyun;Kim Dong Keon;Kim Moon Kyung
    • 한국가시화정보학회:학술대회논문집
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    • 2005.12a
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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.

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A Study of Flow Control in a Combustion Chamber (연소실내의 유동제어에 관한 연구)

  • 김정훈
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2000.05a
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    • pp.86-92
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    • 2000
  • Two-phase flow in a combustion chamber is experimentally analyzed according to the five different conditions in the Reynolds number of $1.02{\times} 10^4$ As the height difference between the primary and secondary jets increases the secondary has a little effect on the primary. In the case of the same height difference the primary jet is affected as the velocity of secondary increases. The primary-jet flow field causes the particle concentration since the particle stagnation phenomena appear in the recirculation zone. The particle concentration is controlled by the velocity of secondary jet the height difference and the angle of primary jet in the test section.

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Investigation on Flow Structure behind Circular and Elliptical Ring by Particle Image Velocimetry (PIV 속도장 측정기법을 이용한 링 후류 유동구조에 대한 실험적 연구)

  • Kim, Seung-Gon;Kim, Seok;Lee, Sang-Joon
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.312-315
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    • 2008
  • The flow structure behind circular and elliptical type rings embedded in a cross-flow was investigated experimentally using two-frame particle image velocimetry (PIV). The experiments were performed in a circulating water channel with a test section of 0.35m height ${\times}$ 0.3m width ${\times}$ 1.1m length. PIV measurements were carried out with varying the Reynolds number in the range of 4.5 ${\times}$ $10^2$ - 4.5 ${\times}$ $10^3$. In the present study, turbulent flow structures in the stream-wise direction and span-wise direction were investigated. The mean velocity field distribution was obtained by statistical-averaging instantaneous velocity fields. The spatial distributions of turbulent statistics such as turbulent intensities and turbulent kinetic energy were also investigated.

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A Contact Algorithm in the Low Velocity Impact Simulation with SPH

  • Min, Oak-Key;Lee, Jeong-Min;Kim, Kuk-Won;Lee, Sung-Soo
    • Journal of Mechanical Science and Technology
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    • v.14 no.7
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    • pp.705-714
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    • 2000
  • The formulation of Smoothed Particle Hydrodynamics (SPH) and a shortcoming of traditional SPH in contact simulation are presented. A contact algorithm is proposed to treat contact phenomenon between two objects. We describe the boundary of the objects with non-mass artificial particles and set vectors normal to the contact surface. Contact criterion using non-mass particles is established in this study. In order to verify the contact algorithm, an algorithm is implemented in to an in-house program; elastic wave propagation is an analysed under low velocity axial impact of two rods. The results show that the contact algorithm eliminates the undesirable phenomena at the contact surface; numerical result with the contact algorithm is compared with theoretical one.

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Experimental study on smoke-logging phenomenon caused by sprinklers during a compartment fire (구획 화재시 스프링클러에 의한 스모크-로깅현상에 관한 실험적연구)

  • Kwon, Young-Jin;Yoon, Ung-Gi;Seo, Dong-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2014.11a
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    • pp.121-122
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    • 2014
  • This study contemplated the descending air current from the smoke layers related to the smoke logging phenomenon in the sprinkler applied design for effective evacuation safety design. As a result, database on the average particle diameter, particle velocity and distribution of sprinkling was obtained and the relationship between the water amount and particle diameter was obtained. Also, in relation to descending air current, the movement of smoke layer to the bottom at the descending air current velocity of 0.6m/s was observed and stable descending air current was observed in existence of fire source over 100kW in size.

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Effects of Inner Jet Injection on Particle Deposition in the Annular Modified Chemical Vapor Deposition Process Using Concentric Tubes (환상형원관을 사용하는 수정된 화학증착(MCVD)방법에서 내부 제트분사가 입자부착에 미치는 영향)

  • 최만수;박경순
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.1
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    • pp.212-222
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    • 1994
  • In the annular Modified Chemical Vapor Deposition process using two concentric tubes, the inner tube is heated to maintain high temperature gradients to have high thermophoretic force which can increase particle deposition efficiency. However, higher axial velocity in a narrow gap between inner and outer tubes can result in a longer tapered entry length. In the present paper, a new concept using an annular jet from the inner tube is presented and shown to significantly reduce the tapered entry length with maintaining high efficiency. Effects of a jet injection on heat transfer, fluid flow and particle deposition have been studied. Of particular interests are the effects of jet velocity, jet location and temperature on the deposition efficiency and tapered length . Torch heating effects from both the previous and present passes are included and the effect of surface radiation between inner and outer tubes is also considered.