• 제목/요약/키워드: slip flow

검색결과 362건 처리시간 0.029초

매우 작은 규모의 LOCA에 있어서 Upper Plenum분석을 위한 RETRAN코드의 연구 (Study of the RBTRAN Code for Upper Plenum Analysis in Very Small LOCA)

  • Hee Cheon No
    • Nuclear Engineering and Technology
    • /
    • 제16권3호
    • /
    • pp.125-130
    • /
    • 1984
  • 매우 작은 규모 LOCA 분석에 RETRAN코드 적용에 있어서 중요 문제점의 하나는 upper plenum에 Bubble rise model의 사용에 있다. 왜냐하면, Bubble rise model은 수리적 발산을 야기할지 모르며, 그 모텔에 사용되는 계수는 큰 규모 냉각재 상실 사고의 실험적 결과에 바탕을 두기 때문이다. 여기서, Bubble rise model을 사용하지 않고 upper plenum의 mixture level을 예측하게 해주는 방법이 제시되었다. 이 방법을 위해 노심과 upper plenum내의 지역 void 분포가 간단한 slip 모델을 이용 괘 유도되었다. 유도된 식으로부터의 결과는 실험 데이타와 매우 잘 일치한다는 것이 발견되었다. 또한, Upper Plenum에 있어서 지역 void는 대규모 LOCA에 있어서 선형 분포와는 달리 균일한 분포를 하고 있다는 것이 발견되었다. upper plenum과 upper head사이의 냉각재 교환이 연구되었다. Taylor instability 개념 도입에 의해 그들 사이에 counter-current flow가 가능하다는 것이 증명되었다.

  • PDF

Extended Graetz Problem Including Axial Conduction and Viscous Dissipation in Microtube

  • Jeong Ho-Eyoul;Jeong Jae-Tack
    • Journal of Mechanical Science and Technology
    • /
    • 제20권1호
    • /
    • pp.158-166
    • /
    • 2006
  • Extended Graetz problem in microtube is analyzed by using eigenfunction expansion to solve the energy equation. For the eigenvalue problem we applied the shooting method and Galerkin method. The hydrodynamically isothermal developed flow is assumed to enter the microtube with uniform temperature or uniform heat flux boundary condition. The effects of velocity and temperature jump boundary condition on the microtube wall, axial conduction and viscous dissipation are included. From the temperature field obtained, the local Nusselt number distributions on the tube wall are obtained as the dimensionless parameters (Peclet number, Knudsen number, Brinkman number) vary. The fully developed Nusselt number for each boundary condition is obtained also in terms of these parameters.

EXPERIMENTAL INVESTIGATION OF FRETTING BEHAVIOR OF TiAlN COATED NUCLEAR FUEL ROD CLADDING MATERIALS

  • Kim, T.H.;Kim, S.S.
    • 한국윤활학회:학술대회논문집
    • /
    • 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
    • /
    • pp.185-186
    • /
    • 2002
  • Fretting of fuel rod cladding material, Zircaloy-4 tube, in PWR nuclear power plants must be reduced and avoided. Nowadays the introduction of surface treatments or coatings is expected to be an ideal solution to fretting damage since fretting is closely related to wear. corrosion and fatigue. Therefore. in this study the fretting wear experiment was performed using TiAlN coated Zircaloy-4 tube as the fuel rod cladding and uncoated Zircaloy-4 as on of grids, especially concentrating on the sliding component. Fretting wear resistance of TiAlN coated Zircaloy-4 tubes was improved compared with that of TiN coated tubes and uncoated tubes and fretting wear mechanisms were brittle fracture and plastic flow at lower slip amplitude but severe oxidation and spallation of oxidative layer at higher ship amplitude.

  • PDF

풍력발전용 권선형 유도발전기의 회전자 여자주파수를 이용한 속도와 출력제어 (A Speed and Power Control of DFIG Using the Exciting Frequency for Wind Power Generating)

  • 이우석;오철수
    • 대한전기학회논문지:전기기기및에너지변환시스템부문B
    • /
    • 제48권7호
    • /
    • pp.349-356
    • /
    • 1999
  • Wide operating range and speed control is needed for wind power generating and a Doubly Fed Induction Generator(DFIG) has good adaptivity for that purpose. This paper deals with the speed and power control using the Grid connected DFIG in the super-synchronous speed regions, by controlling frequency and voltage fed to the rotor. Power flow of the DFIG and steady-state algebraic equations of the equivalent circuit are analyzed. For the speed control analysis, torque simulation is performed whereby the different slip between operating motor driving frequency and synchronous frequency of M-G system applied. To keep the output rating of the generator, the exciting frequency and voltage attenuation are applied.

  • PDF

익렬 날개 후단소음의 저감 (Trailing Edge Noise Modification in a Blade Cascade)

  • 손정민;김휘중;이승배;조성민
    • 유체기계공업학회:학술대회논문집
    • /
    • 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
    • /
    • pp.116-122
    • /
    • 2002
  • It is addressed that the turbulent broadband sound power from a sirocco fan can be modeled by the trailing edge noise. The trailing edge noise is usually influenced by inflow turbulenca separation, and boundary layer thickness on the blade. The design parameters such as solidity (c/s) and stagger angle are specified to predict performance and noise level because the separation and slip velocity are strongly affected by them along with the flow coefficient. This paper reports the effects of the stagger angle upon the trailing edge noise for various trailing edge shapes. It is believed that the serrated trailing edge provides break-up mechanism for organized convecting vortices, thereby reduce the overall noise level for every case of stagger angle.

  • PDF

A Simple Lagrangian PDF Model for Wall-Bounded Turbulent Flows

  • Lee, Chang-Hoon;Kim, Byung-Gu;Kim, Nam-Hyun
    • Journal of Mechanical Science and Technology
    • /
    • 제14권8호
    • /
    • pp.900-911
    • /
    • 2000
  • A simple Lagrangian pdf model is proposed with a new numerical algorithm for application in wall-bounded turbulent flows. To investigate the performance of the Lagrangian model, we minimize model's dependence on empirical constants by selecting the simplest model for turbulent dissipation rate. The effect of viscosity is also included by adding a Brownian random walk calculate the position of a particle. For the no-slip condition at the wall and correct nearwall behavior of velocity, we develop a new boundary treatment for the particles that strike the wall. By applying the model to a fully developed turbulent channel flow at low Reynolds number, we investigate the model's performance through comparison with direct numerical simulation result.

  • PDF

시로코 홴 성능 및 공력 소음 예측에 관한 연구 (Measurement and Prediction of Aerodynamic Noise from Sirocco Fans)

  • 김경호;박계찬;이승배
    • 한국유체기계학회 논문집
    • /
    • 제2권4호
    • /
    • pp.57-64
    • /
    • 1999
  • The prediction method of the performance and aerodynamic noise from a sirocco fan was developed and compared with measured data. To predict the performance of the sirocco fan, the well-known slip coefficients and various loss models were tested and applied to forward curved sirocco impellers. Using loss models proposed for both impeller and casing, the predicted performance characteristics were in good agreement with measured ones by an ANSI test plenum. Various scaling models for aerodynamic noise from the sirocco fan were evaluated and tested against measured power levels in terms of flow coefficient. It was shown that the turbulent broadband sound power from the sirocco fan can be modeled successfully by trailing edge noise.

  • PDF

초소형 원심압축기의 날개 두께 변화에 따른 성능에 관한 실험적 연구 (Performance Variations of Small Centrifugal Compressor with Exit Blade Thickness)

  • 강신형;조운제;윤하용;이승갑
    • 유체기계공업학회:학술대회논문집
    • /
    • 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
    • /
    • pp.135-141
    • /
    • 1998
  • Some sized centrifugal compressor were designed and their performance measured to investigate the effects of exit blade thickness, width and back swept angle. The impeller of larger blade thickness shows low pressure ratio compared with that of smaller one. Backswept angle have also large effect on the efficiency. Measured values of slip factor are quite different from the estimated values of Wiesner-Busemann model and increase with the flow rate.

  • PDF

부유식 해양구조물 주위의 쇄파현상을 동반한 3차원 비선형성 파의 수치해석 (Numerical Analysis of the Three-Dimensional Nonlinear Waves Caused by Breaking Waves around a Floating Offshore Structure)

  • 박종천;관전수명
    • 한국해양공학회지
    • /
    • 제10권3호
    • /
    • pp.62-73
    • /
    • 1996
  • Numerical simulation is made of the three-dimensional wave breaking motion about a part of a floating offshore structure containing a circular cylinder mounted vertically onto a lower hull in regular periodic gravity wave generated by a numerical wave maker. TUMMAC-VIII finite-difference method is newly developed for such a problem. By use of density-function technique the three-dimensional wave breaking motion is approximately implenented in the framework of rectangular grid system. A porosity technique is devised for the implementation of the no-slip bydy boundary conditions. The generation of breaking waves by the interaction of incident waves with the structure is well simulated and interesting features of breaking waves are revealed with containing degree of quantitative and qualitative accuracy.

  • PDF

선수주위 쇄파현상의 수치시뮬레이션에 관한 기초연구 (A FUNDAMENTAL STUDY ON THE NUMERICAL SIMULATION OF WAVE BREAKING PHENOMENON AROUND THE FORE-BODY OF SHIP)

  • 엄태진;이영길;정광열
    • 한국전산유체공학회:학술대회논문집
    • /
    • 한국전산유체공학회 2005년도 추계 학술대회논문집
    • /
    • pp.195-199
    • /
    • 2005
  • Wave breaking phenomenon near the fore body of a ship is numerically simulated. The ship advance with uniform velocity in calm water. For the simulation, incompressible Navier-Stokes equations and continuity equation are adopted as governing equations. The simulation is carried out in staggered variable mesh system with finite difference method. Marker and Cell(MAC) method and Marker-Density method are employed to track the free surface. Body boundary conditions are satisfied with the adoption of porosity method and no-slip condition on the hull surface. The ship model has a wedge type fore-body, and the computational domain is an appropriate region around the fore-body. The computation results are compared with some experimental results. Also the difference of the free surface tracking methods are discussed.

  • PDF