• Title/Summary/Keyword: Axi-Symmetric flow

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NUMERICAL ANALYSIS OF CAVITATION WITH COMPRESSIBILITY EFFECTS AROUND HEMISPHERICAL HEAD-FORM BODY (반구형 전두부 실린더에서 발생하는 캐비테이션 유동의 압축성 효과에 대한 수치해석 연구)

  • Park, S.;Rhee, S.H.;Shin, B.R.
    • Journal of computational fluids engineering
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    • v.18 no.4
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    • pp.9-16
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    • 2013
  • Cavitation on an axi-symmetric hemispherical head-form body was studied using an Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. To consider compressibility effects on the vapor phase and cavity interface, a pressure-based compressible flow CFD code was developed. To validate the developed CFD code, cavitating flow around the hemispherical head-form body was simulated using pressure-based incompressible and compressible CFD codes and validated against existing experimental data in the three-way comparison. The cavity shedding behavior, length of re-entrant jet, drag history, and Strouhal number of the hemispherical head-form body were compared between two CFD codes. The results, in this paper, suggested that the computations of cavitating flow with compressibility effects improve the description of cavity dynamics.

Heat transfer enhancement in gas tungsten arc welding using azimuthal magnetic fields generated by external current

  • Kim, Yiseul;Lee, Jaewook;Liu, Xiaolong;Lee, Boyoung;Chang, Yunlong
    • Coupled systems mechanics
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    • v.6 no.2
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    • pp.113-125
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    • 2017
  • This paper proposes the idea to enhance the heat transfer in Gas Tungsten Arc Welding (GTAW) by using the azimuthal magnetic field. The azimuthal magnetic field generated by the external currents makes the Lorentz force stronger, and consequently improves the heat transfer by the faster flow movement. The enhanced heat transfer might improve the welding performance by increasing the temperature at the workpiece. To validate the proposed idea, a two-dimensional axi-symmetric model of GTAW is built, and the multiphysics simulation of GTAW is carried out. As the analysis result, the distributions of electric current, electromagnetic fields, arc flow velocity, and temperature are investigated. Then, the proposed idea for heat transfer enhancement is validated by comparing the Lorentz force, flow velocity, and temperature distribution with and without azimuthal magnetic fields.

Flow Characteristics of Axi-symmetric Swirl Jet in the Initial Regions (축대칭 회전분사류의 초기 유동특성)

  • Han, Yong-Un;An, Yeong-Hui;Kim, Dong-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.4
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    • pp.531-538
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    • 2002
  • Flow characteristics of a round jet with swirl number of 0.17 have been investigated using a hot -wire anemometry in the initial region within 10D(exit diameter). Swirl effects were observed by comparing centerline flow characteristics, similarities and turbulent budgets of a swirl jet and a free jet, respectively. To obtain similarity of the radial profiles mean velocity and higher moments were measured at the vertical pl anes, located at 2.5, 5.0, 7.5D, 10D, respectively. The centerline velocity characteristics were also measured. It is turned out that similarities of mean and Reynolds stress are established. The jet boundary has wider width than that of a free jet and the shear stress also becomes stronger. In addition the centerline decay becomes faster than that of the free jet, indicating that the swirl induces more entrainment in the initial region of the swirl Jet by transferring the axial mean kinetic energy into the swirl energy and, therefore, has wider boundary, compared with that of free jet.

Numerical Simulation for Pressing Process of Hot glass (고온 유리의 프레스 성형 공정 시뮬레이션)

  • Ji Suk Man;Choi Joo Ho;Kim Jun Bum;Ha Duk Sik
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.5 s.170
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    • pp.205-213
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    • 2005
  • This paper addresses a method for numerical simulation in the pressing process of hot glass. Updated Lagrangian finite element formulations are employed for the flow and energy equations to accommodate moving meshes. The model is assumed axi-symmetric and creep flow is assumed due to the high viscosity. Commercial software ANSYS is used to solve the coupled flow and energy equations. Moving contact points as well as free surface during the pressing are effectively calculated and updated by utilizing API functions of CAD software Unigraphics. The mesh distortion problem near the wall is overcome by automatic remeshing, and the temperatures of the new mesh are conveniently interpolated by using a unique function of ANSYS. The developed model is applied to the pressing process of TV glasses. In conclusion, the presented method shows that the pressing process accompanying moving boundary can be simulated by effectively combining general purpose software without resorting to special dedicated codes.

Characterization of Gas Distribution Effect in Inductively Coupled Plasma System (유도결합 플라즈마 시스템의 수치 모델링에서 가스 분배 특성 해석)

  • Joo, Junghoon
    • Journal of the Korean institute of surface engineering
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    • v.46 no.3
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    • pp.133-138
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    • 2013
  • We have developed a 2D axi-symmetric numerical model for an inductively coupled plasma system in order to analyze gas mixing effect through a narrow gap shower head. For frictional flow, holes of 0.5 mm diameter and 2 mm length are approximately modeled in 2D. Gas velocity distribution 10 mm below the shower head showed 2 times difference between the center and the edge at 10 mTorr. At 10 mm above the wafer, it was increased to 6 times difference due to the pumping duct effect. The model with a 5 mm height buffer region of a shower head showed reasonable behavior of Ar discharge. The density of Ar metastable showed additional peak inside the buffer region around the edge holes.

Finite Element Analysis and Process Planning about the Auto Transmission Solenoid Valve using of Multi-Former (다단-포머를 이용한 오토트랜스 미션용 솔레노이드 밸브 공정설계 및 유한요소해석)

  • Park, Chul-Woo
    • Journal of Advanced Marine Engineering and Technology
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    • v.33 no.1
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    • pp.97-103
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    • 2009
  • The process design of forward Extrusion and Upsetting of Axi-symmetric part has been studied in this paper. During the cold forging product; auto transmission Solenoid Valve part, the defects such as folding and under-fill can be appeared by the improperly controlled metal flow. In this study, to reduce the folding and under-fill the design of experiments has been used to find out the significant design variables in the design of forging process. This paper deals with an Process Planning with which designer can determine operation sequences even after only a little experience in Process Planning of Multi-Former products by multi-stage former working. The approach is based on knowledge-based rules, and a process knowledge-base consisting of design rules is built. Based on the systematic procedure of process sequence design, the forming operation of cold forged auto transmission Solenoid Valve part is analyzed by the commercial Finite Element program, DEFORM/2D.

Simulation of heat flow for rectangular electrodes (사각형 전극에서의 열유동 해석)

  • 신윤섭;박수웅;나석주
    • Journal of Welding and Joining
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    • v.8 no.1
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    • pp.62-69
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    • 1990
  • Being focused on the recent studies that the fatigue strength of resistance spot weldmentes can be improved by using ellipsoidal weld nuggets, the voltage and temperature distribution in resistance spot weldments were simulated for the various rectangular electrodes which had the different aspect ratio of the contact area. Because the electrode shape was not axi-symmetric, the solution domain for simulation should be three dimensional. A series of experiments were carred out to verify the analytically obtained temperature distribution in the weldment. From the calculational and experimental results, it could be revealed that the nugget took the form of ellipsoid, while both results showed a considerable discrepancy for the high aspect ratio.

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A Numerical Study on the Compression Wave Generated by the Train Entering a Tunnel (열차가 터널에 진입할 때 발생하는 압축파에 대한 수치해석)

  • Kim, Sa-Ryang
    • The KSFM Journal of Fluid Machinery
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    • v.9 no.6 s.39
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    • pp.17-21
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    • 2006
  • The numerical simulations on the train entering a tunnel were performed by solving unsteady axi-symmetric problems. In the case that 5th order velocity profile is used to reduce the effects of the pressure wave generated by the train starting abruptly, the effect of the initial distance between the train and the tunnel were examined. The impulsive start gives undesired pressure disturbances to the flow field including inside the tunnel. But 5th order velocity profile with initial distance more than 80 m gives much stable pressure variance in time, and pressure distribution inside the tunnel in space. The distance to the train reaches the highest running velocity from the start should be more than 80 m when the train speed is 350 km/h.

Cooling Performance Analysis of Sub-scale Calorimeter (축소형 칼로리미터의 냉각성능 해석)

  • 조원국;문윤완
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2003.05a
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    • pp.9-12
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    • 2003
  • A cooling performance analysis has been made in the 8-channel calorimeter based on sub-scale KSR-III engine. Three-dimensional heat transfer analysis in cooling channels has been performed using the heat flux distribution through the chamber wall predicted from axi-symmetric compressible flow inside the combustion chamber. The heat flux distribution was verified against the published literature. Presented for the development and operation of the calorimeter are the coolant pressure drop, coolant temperature rise and the maximum chamber wall temperature.

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Blast Furnace Modeling for Predicting Cohesive Zone Shape (융착대 예측을 위한 고로공정 모델링)

  • Yang, Kwang-Heok;Choi, Sang-Min;Jung, Jin-Kyung
    • 한국연소학회:학술대회논문집
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    • 2006.04a
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    • pp.39-45
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    • 2006
  • Analysis of the internal state of the blast furnace is needed to predict and control the operating condition. Especially, it is important to develop modeling of blast furnace for predicting cohesive zone because shape of cohesive zone influences overall operating condition of blast furnace such as gas flow, chemical reactions and temperature. because many previous blast furnace models assumed cohesive zone to be fixed, they can't evaluate change of cohesive zone shape by operation condition such as PCR, blast condition, and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace process. In this model, cohesive zone is changed by solid temperature range, FVM is used for numerical simulation. To find location of cohesive zone whole calculation procedure is iterated Until cohesive zone is converged. Through this approach, shape of cohesive zone, velocity, composition and temperature within the furnace are predicted by model.

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