• 제목/요약/키워드: Momentum balance

검색결과 127건 처리시간 0.023초

제어체적법에 의한 Ar 아크 플라즈마의 특성 계산 (Numerical calculations of characteristics of Argon arc plasma using the control volume method)

  • 김외동;고광철;강형부
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1995년도 하계학술대회 논문집 C
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    • pp.1404-1406
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    • 1995
  • In this paper, argon gas was used for numerical analysis of an arc in a cutting plasma torch driven by constant current. We established nozzle-constricting type torch domain and calculated steady state characteristics of argon arc plasma using the control volume method(CVM). For simplicity, we assumed that the flow field is laminar and the local thermodynamic equilibrium(LTE) prevails in all domain regions. We also neglected cathode-fall and anode-fall effects. Considering magnetic pinch effect and viscosity effect, we solved the momentum equation. Voltage drop in the arc column due to input current was calculated from the temperature field obtained by the energy balance equation.

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화학적 기계 연마를 위한 탄성변형을 고려한 평균유동모델 (Average Flow Model with Elastic Deformation for CMP)

  • 김태완;이상돈;조용주
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 2004년도 학술대회지
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    • pp.331-338
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    • 2004
  • We present a three-dimensional average flow model considering elastic deformation of pad asperities for chemical mechanical planarization. To consider the contact deformation of pad asperities in the calculation of the flow factor, three-dimensional contact analysis of a semi-infinite solid based on the use of influence functions is conducted from computer generated three dimensional roughness data. The average Reynolds equation and the boundary condition of both force and momentum balance are used to investigate the effect of pad roughness and external pressure conditions on film thickness and wafer position angle.

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2방향 파랑하에서 파의 변형 (Wave Transformation in the Intersecting Wave Trains)

  • 김경호;조재희;윤영호
    • 한국해안해양공학회지
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    • 제7권4호
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    • pp.313-320
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    • 1995
  • 일정 경사를 갖는 해안에 입사하는 같은 주기의 두개의 파열이 교차하는 경우에 대하여 천해역에서 파랑 변형에 대한 수치해석을 수행하였다. 본 모형은 파랑 에너지 평형 및 파랑운동 보존식에 기초하여, 시간과 수심에 대해 평균한 질량 및 수평방향 운동 보존방정식을 반복적으로 계산하여 해를 구하였다. 계산된 결과를 이용하여, 천해역에서 파열이 교차할 때 파고와 평균수위변동에 영향을 주는 입사 파향각 및 심해파고와 같은 매개변수 변화에 따른 파랑 변형에 대해 고찰하였다.

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희체가스 가중합산모델을 적용한 미분탄 연소의 해석 (Modeling of a Pulverized Coal Combustion With Applying WSGGM)

  • 유명종;백승욱
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
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    • pp.155-163
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    • 1999
  • A numerical study for simulating a swirling pulverized coal combustion in axisymmetric geometry is done here by applying the weighted sum of gray gases model (WSGGM) approach with the discrete ordinate method (DOM) to model the radiative heat transfer equation. In the radiative transfer equation, the same polynomial equation and coefficients for weighting factors as those for gas are adopted for the coal/char particles as a function of partial pressure and particle temperature. The Eulerian balance equations for mass, momentum, energy, and species mass fractions are adopted with the standard ${\kappa}-{\varepsilon}$ turbulence model, whereas the Lagrangian approach is used for the particulate phase for soot. The eddydissipation model is employed for the reaction rate for gaseous mixture, and the single-step first-order reaction model for the devolatilization process for coal. By comparing the numerical results with experimental ones, the models used here are confirmed and found to be one of good alternatives for simulating the combustion as well as radiative characteristics.

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HCM 방법을 이용한 다중 FNN 설계에 관한 연구 (A Study on the Design of Multi-FNN Using HCM Method)

  • 박호성;윤기찬;오성권
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1999년도 추계학술대회 논문집 학회본부 B
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    • pp.797-799
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    • 1999
  • In this paper, we design the Multi-FNN(Fuzzy-Neural Networks) using HCM Method. The proposed Multi-FNN uses simplified inference as fuzzy inference method and Error Back Propagation Algorithm as learning rules. Also, We use HCM(Hard C-Means) method of clustering technique for improvement of output performance from pre-processing of input data. The parameters such as apexes of membership function, learning rates and momentum coefficients are adjusted using genetic algorithms. We use the training and testing data set to obtain a balance between the approximation and the generalization of our model. Several numerical examples are used to evaluate the performance of the our model. From the results, we can obtain higher accuracy and feasibility than any other works presented previously.

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다변수 퍼지 입력 공간 분할에 의한 퍼지-뉴럴 네트워크 (Fuzzy-Neural Networks by Means of Division of Fuzzy Input Space with Multi-input Variables)

  • 박호성;윤기찬;오성권;안태천
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1999년도 추계학술대회 논문집 학회본부 B
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    • pp.824-826
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    • 1999
  • In this paper, we design an Fuzzy-Neural Networks(FNN) by means of divisions of fuzzy input space with multi-input variables. Fuzzy input space of Yamakawa's FNN is divided by each separated input variable, but that of the proposed FNN is divided by mutually combined input variables. The membership functions of the proposed FNN use both triangular and gaussian membership types. The parameters such as apexes of membership functions, learning rates, momentum coefficients, weighting value, and slope are adjusted using genetic algorithms. Also, an aggregate objective function(performance index) with weighting value is utilized to achieve a sound balance between approximation and generalization abilities of the model. To evaluate the performance of the proposed model, we use the data of sewage treatment process.

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HCM과 유전자 알고리즘에 기반한 확장된 다중 FNN 모델 설계 (Design of Extended Multi-FNNs model based on HCM and Genetic Algorithm)

  • 박호성;오성권
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2001년도 합동 추계학술대회 논문집 정보 및 제어부문
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    • pp.420-423
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    • 2001
  • In this paper, the Multi-FNNs(Fuzzy-Neural Networks) architecture is identified and optimized using HCM(Hard C-Means) clustering method and genetic algorithms. The proposed Multi-FNNs architecture uses simplified inference and linear inference as fuzzy inference method and error back propagation algorithm as learning rules. Here, HCM clustering method, which is carried out for the process data preprocessing of system modeling, is utilized to determine the structure of Multi-FNNs according to the divisions of input-output space using I/O process data. Also, the parameters of Multi-FNNs model such as apexes of membership function, learning rates and momentum coefficients are adjusted using genetic algorithms. An aggregate performance index with a weighting factor is used to achieve a sound balance between approximation and generalization abilities of the model. To evaluate the performance of the proposed model we use the time series data for gas furnace and the NOx emission process data of gas turbine power plant.

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원심펌프의 축추력 제어법에 관한 연구 (A Method of Axial Thrust Control in Centrifugal Pump)

  • 최영도;쿠로카와준이치
    • 한국유체기계학회 논문집
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    • 제10권4호
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    • pp.15-20
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    • 2007
  • In order to control and balance axial thrust of turbo machine, many types of balancing devices are used but most of them are complicated and sometimes cause troubles. In this study, a very simple device of using shallow grooves mounted on a casing wall, known as "J-Groove", is proposed and studied experimentally and theoretically. The result shows that 70% of axial thrust in an industrial 4-stage centrifugal pump can be reduced at the best efficiency point. Moreover, the analytical method of "interfered gap flow" is established and a simple formula which can determine the optimum dimension of groove and its location is proposed.

수중폭발 이론을 사용한 노심폭주사고 시 노심 팽창 및 에너지 거동 수치해석 (NUMERICAL ANALYSIS ON THE REACTOR CORE EXPANSION AND ENERGY BEHAVIORS DURING CDA USING UNDERWATER EXPLOSION THEORY)

  • 강석훈
    • 한국전산유체공학회지
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    • 제21권3호
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    • pp.8-14
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    • 2016
  • A numerical analysis is conducted to estimate the core expansion and the energy behaviors induced by a core disruptive accident in a sodium-cooled fast reactor. The numerical formulation based on underwater explosion theory is carried out to simulate the core explosion inside the reactor vessel. The transient pressure, temperature and expansion of the core are examined by solving the equation of state and nonlinear governing equation of momentum conservation in one-dimensional spherical coordinates. The energy balance inside the computation domain is examined during the core expansion process. Heat transfer between the core and the sodium coolant, and the bubble rise during the expansion process are briefly investigated.

수평평판의 막응축에서 전도 열저항의 영향 (The Effect of Heat Conduction resistance on Laminar Film Condensation along a Horizontal Plate)

  • 이억수
    • 한국마린엔지니어링학회:학술대회논문집
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    • 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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    • pp.183-188
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    • 2005
  • The effect of heat conduction resistance on laminar film condensation of the pure saturated vapor in forced flow over a flat plate has been investigated as boundary layer solutions. A efficient numerical methods for water are proposed for its solution. The momentum and energy balance equations are reduced to a nonlinear system of ordinary differential equations with four parameters: the Prandtl number, Pr, Modified Jacob number, $Ja^{\ast}/Pr$, defined by an overall temperature difference, a property ratio $\sqrt{P_l{\mu}_l/P_v{\mu}_v}$ and the conjugate parameter ${\zeta}$. The similarity and simplified solutions obtained reveal the effects of the conjugate parameter.

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