• 제목/요약/키워드: Velocity Contour

검색결과 100건 처리시간 0.024초

비예혼합 선형 와환에서의 화염 전파 특성에 관한 실험적 연구 (An Experimental Study on Flame Propagation along Non-premixed Vortex Tube)

  • 양승연;노윤종;정석호
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집D
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    • pp.864-870
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    • 2001
  • Flame propagation along vortex tube was experimentally investigated. The vortex tube was generated by the ejection of propane from a nozzle through a single stroke motion of a speaker and the ignition was induced from a single pulse laser. Non-reactive flow fields were visualized using shadow technique. From these images, vortex ring size and translational velocity were measured in order to determine the ignition time and position. Flame structure and flame speed were measured using high speed CCD camera. Flame speed was accelerated during the initial stage of flame kernel growth, and reached near constant value during steady propagation period. Near the completion of propagation, flame speed was decelerated and then extinguished. Flame speed along the non-premixed vortex tube was found to be linearly proportional to circulation, which was similar to that of the flame propagation along premixed vortex ring. Ignition position minimally affects the propagation characteristics. These imply that flame is propagating along the maximum speed locus expected to be along stoichiometric contour and also support the existence of tribrachial flames.

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Three dimensional flow analysis within a profile extrusion die by using control volume finite-element method

  • Kim, Jongman;Youn, Jae-Ryoun;Hyun, Jae-Chun
    • Korea-Australia Rheology Journal
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    • 제13권2호
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    • pp.97-106
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    • 2001
  • Three-dimensional flow analysis was performed by using the control volume finite-element method for design of a profile extrusion die. Because polymer melt behavior is complicated and cross-sectional shape of the profile extrusion die is changing continuously, the fluid flow within the die must be analyzed three-dimensionally. A commercially available polypropylene is used for theoretical and experimental investigations. Material properties are assumed to be constant except for the viscosity. The 5-constant modified Cross model is used for the numerical analysis. A test problem is examined in order to verify the accuracy of the numerical method. Simulations are performed for conditions of three different screw speeds and three different die temperatures. Predicted pressure distribution is compared with the experimental measurements and the results of the previous two-dimensional study. The computational results obtained by using three dimensional CVFEM agree with the experimental measurements and are more accurate than those obtained by using the two-dimensional cross-sectional method. The velocity profiles and the temperature distributions within several cross-sections of the die are given as contour plots.

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An optimum design study of interlacing nozzle by using Computational Fluid Dynamics

  • Juraeva Makhsuda;Ryu Kyung-Jin;Kim Sang-Dug;Song Dong-Joo
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2006년도 PARALLEL CFD 2006
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    • pp.395-397
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    • 2006
  • Air interlacing serves to protect the yarn against damage, strengthens inter-filament compactness or cohesion, and ensures fabric consistency. The air interlacing nozzle is used to introduce intermittent nips to a filament yarn so as to improve its performance in textile processing. The effect of various interlacing nozzle geometries on the interlacing process was studied. The geometries of interlacing nozzles with single or multiple air inlets located across the width of yarn channels are investigated. The basis case is the yarn channel, with a perpendicular main air inlet in the middle. Other cases have main air inlets, slightly inclined double sub air inlets, The yarn channel cross sectional shapes are either semicircular or rectangular shapes. The compressed impinging jet from the main air inlet hole hits the opposing bottom wall of the yarn channel, is divided into two branches, joins with the compressed air coming out from sub air inlet at the bottom and creates two free jets at both ends of the yarn channel. The compressed air movement in the cross-section consists of two opposing directional vortices. The CFD-FASTRAN flow parallel solver was used to perform steady simulations of impinging jet flow inside of the interlace nozzles. The vortical structure and the flow pattern such as pressure contour, particle traces, velocity vector plots inside of interlace nozzle geometry are discussed in this pater.

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유한수심(有限水深)의 해상(海上)에서 규칙파(規則波)에 놓인 구(球)의 운동특성(運動特性) (On the Motion Characteristics of a Freely-Floating Sphere in a Water of Finite Depth)

  • 최항순;이성균
    • 대한조선학회지
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    • 제19권1호
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    • pp.23-32
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    • 1982
  • Herein the motion of a freely-floating sphere in a water of finite depth is analysed within the framework of a linear potential theory. A velocity potential describing fluid motion is generated by distributing pulsating sources and dipoles on the immersed surface of the sphere, without introducing an inner flow model. The potential becomes the solution of an integral equation of Fredholm's second type. In the light of the vertical axisymmetry of the flow, surface integrals reduce to line integrals, which are approximated by summation of the products of the integrand and the length of segments along the contour. Following this computational scheme the diffraction potential and the radiation potential are determined from the same algorithm of solving a set of simultaneous linear equations. Upon knowing values of the potentials hydrodynamic forces such as added mass, hydrodynamic damping and wave exciting forces are evaluated by the integrating pressure over the immersed surface of the sphere. It is found in the case of finite water depth that the hydrodynamic forces are much different from the corresponding ones in deep water. Accordingly motion response of the sphere in a water of finite depth displays a particular behavior both in a amplitude and phase.

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Hermite 유동함수법에 의한 정사각형 공동 내부의 자연대류 유동계산 (COMPUTATIONS OF NATURAL CONVECTION FLOW WITHIN A SQUARE CAVITY BY HERMITE STREAM FUNCTION METHOD)

  • 김진환
    • 한국전산유체공학회지
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    • 제14권4호
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    • pp.67-77
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    • 2009
  • This paper is a continuation of a recent development on the Hermite-based divergence-free element method and deals with a non-isothermal fluid flow driven by the buoyancy force in a square cavity with temperature difference across the two sides. Two Hermite functions are considered for numerical computations in this paper. One is a cubic function and the other is a quartic function. The degrees-of-freedom of the cubic Hermite function are stream function and its first and second derivatives for the velocity field, and temperature and its first derivatives for the temperature field. The degrees-of-freedom of the quartic Hermite function include two second derivatives and one cross derivative of the stream function in addition to the degrees-of-freedom of the cubic stream function. This paper presents a brief review on the Hermite based divergence-free basis functions and its finite element formulations for the buoyancy driven flow. The present algorithm does not employ any upwinding or a stabilization term. However, numerical values and contour graphs for major flow variables showed good agreements with those by De Vahl Davis[6].

난류모형을 적용한 엔진 연료실의 유동해석 (Flow Analysis in the Fuel Chamber of Engine by Applying Turbulent Models)

  • 곽승현
    • 한국항해항만학회지
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    • 제30권5호
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    • pp.369-374
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    • 2006
  • 복잡한 연료실 내의 유동현상을 난류모형을 적용하여 해석하였다. 적용한 모형은 $k-\varepsilon,\;k-\omega$, spalart-allmaras, reynolds stress이고, 연로실내의 격자는 혼합격자(hybrid grid) 이다. 속도벡터, 압력분포, 반복계산(iteration)에 의한 잔류치(residual), 동력학적 양정(dynamic head) 등을 모사하였다. 4개의 난류모형을 연료실 유동에 적용하였다. 3차원 수치실험에 앞서, 수치검증을 위하여 2차원 물체 주위의 점성유동을 $k-\varepsilon$ 난류모형을 적용하여 모사하였고 항력계수를 비교하였다.

Real-time geometry identification of moving ships by computer vision techniques in bridge area

  • Li, Shunlong;Guo, Yapeng;Xu, Yang;Li, Zhonglong
    • Smart Structures and Systems
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    • 제23권4호
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    • pp.359-371
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    • 2019
  • As part of a structural health monitoring system, the relative geometric relationship between a ship and bridge has been recognized as important for bridge authorities and ship owners to avoid ship-bridge collision. This study proposes a novel computer vision method for the real-time geometric parameter identification of moving ships based on a single shot multibox detector (SSD) by using transfer learning techniques and monocular vision. The identification framework consists of ship detection (coarse scale) and geometric parameter calculation (fine scale) modules. For the ship detection, the SSD, which is a deep learning algorithm, was employed and fine-tuned by ship image samples downloaded from the Internet to obtain the rectangle regions of interest in the coarse scale. Subsequently, for the geometric parameter calculation, an accurate ship contour is created using morphological operations within the saturation channel in hue, saturation, and value color space. Furthermore, a local coordinate system was constructed using projective geometry transformation to calculate the geometric parameters of ships, such as width, length, height, localization, and velocity. The application of the proposed method to in situ video images, obtained from cameras set on the girder of the Wuhan Yangtze River Bridge above the shipping channel, confirmed the efficiency, accuracy, and effectiveness of the proposed method.

CAP SASW 기법에 의한 지반단면의 전단강성구조 평가 (Evaluation of Stiffness Profile for a Subgrade Cross-Section by the CAP(Common-Array-Profiling)-SASW Technique)

  • 조성호;장대우;강태호;이일화
    • 한국지반공학회논문집
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    • 제21권4호
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    • pp.71-81
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    • 2005
  • 지반의 표면에서 비파괴적으로 지반의 구조나 하부강성을 구하는 표면파 기법의 초기형태는 2차원 평면파의 측정과 해석에 기반을 두었으나, 이후 3차원 입체파에 기반을 두는 형태로 발전하였다. 그러나 체적파의 간섭, 근접장 효과, 표면파 측정해상도의 한계 등으로 인하여 3차원 입체파의 활용은 제한적이었고, 측정 지반을 대표하는 1차원 평가에 국한되었다. 본 연구에서는 SASW 시험의 수치모델링을 통하여 수직 레일레이파, 수평 레일레이파, 러브파 등의 표면파 전파 특성을 3차원 영역에서 심도있게 고찰하였으며, 표면파의 근접장 효과를 최소화하기 위한 새로운 필터조건을 정립하였고, 결과적으로 CAP(common-array-profiling)-SASW라는 기법이라고 하는 개선된 표면파 기법을 제안하게 되었다. CAP-SASW 기법의 적용으로 인하여 좁은 폭의 지반단면에 대한 전단파 속도 주상도 평가가 가능하게 되었고, 지반 단면에 대한 2차원 지반강성 평가도 가능하게 되었다. 본 연구에서 제안한 기법의 검증을 위하여 자연 지반을 대상으로 하여 CAP-SASW 시험, 기존 SASW 시험, 다운홀 시험 등을 수행하여 획득된 전단파 주상도를 비교하였다.

차량 내부 탑승자의 쾌적성 평가를 위한 초기 냉방운전 성능에 대한 수치해석적 연구 (Numerical Analysis on the Initial Cool-down Performance Inside an Automobile for the Evaluation of Passenger's Thermal Comfort)

  • 김윤기;양장식;백제현;김경천;지호성
    • 한국자동차공학회논문집
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    • 제18권5호
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    • pp.115-123
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    • 2010
  • Cool-down performance after soaking is important because it affects passenger's thermal comfort. The cooling capacity of HVAC system determines initial cool down performance in most cases, the performance is also affected by location, and shape of panel vent, indoor seat arrangement. Therefore, optimal indoor designs are required in developing a new car. In this paper, initial cool down performance is predicted by CFD(computational fluid dynamics) analysis. Experimental time-averaging temperature data are used as inlet boundary condition. For more reliable analysis, real vehicle model and human FE model are used in grid generation procedure. Thermal and aerodynamic characteristics on re-circulation cool vent mode are investigated using CFX 12.0. Thermal comfort represented by PMV(predicted mean vote) is evaluated using acquired numerical data. Temperature and velocity fields show that flow in passenger's compartment after soaking is considerably unstable at the view point of thermodynamics. Volume-averaged temperature is decreased exponentially during overall cool down process. However, temperature monitored at different 16 spots in CFX-Solver shows local variation in head, chest, knee, foot. The cooling speed at the head and chest nearby panel vent are relatively faster than at the knee and foot. Horizontal temperature contour shows asymmetric distribution because of the location of exhaust vent. By evaluating the passenger's thermal comfort, slowest cooling region is found at the driver's seat.

AN OPTIMUM DESIGN STUDY OF INTERLACING NOZZLE BY ANALYZING FLUID FLOW INSIDE INTERLACING NOZZLES

  • Juraeva Makhsuda;Ryu Kyung Jin;Kim Sang Dug;Song Dong Joo
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2005년도 추계 학술대회논문집
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    • pp.93-97
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    • 2005
  • Air interlacing serves to protect the yarn against damage, strengthens inter-filament compactness or cohesion, and ensures fabric consistency. The air interlacing nozzle is used to introduce intermittent nips to a filament yarn so as to improve its performance in textile processing. This study investigates the effect of interlacing nozzle geometry on the interlacing process. The geometries of interlacing nozzles with multiple air inlets located across the width of a yarn channels are investigated. The basic interlacing nozzle is the yarn channel, with a perpendicular single air inlet in the middle. The yarn channel shapes are cross sections with semicircular or rectangular shapes. This paper presents three doubled sub air inlets with main air inlet and one of them is slightly inclined doubled sub air inlets with main air inlet. The compressed air coming out from the inlet hits the opposing wall of the yarn channel, divides into two branches, flows trough the top side of yarn channel, joins with the compressed air coming out from the sub air inlet and then creates two free jets at both ends of the yarn channel. The compressed air moves in the shape of two opposing directional vortices. The CFD-FASTRAN was used to perform steady simulations of impinging jet flow inside of the interlace nozzles. The vortical structure and the flow pattern such as pressure contour, particle traces, velocity vector plots inside of interlace nozzle geometry are discussed in this paper.

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