• Title/Summary/Keyword: Unsteady Friction

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A FLUID TRANSIENT ANALYSIS FOR THE PROPELLANT FLOW WITH AN UNSTEADY FRICTION IN A MONOPROPELLANT PROPULSION SYSTEM (단일추진제 추진시스템의 비정상 마찰을 고려한 과도기유체 해석)

  • Chae Jong-Won
    • Journal of computational fluids engineering
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    • v.11 no.1 s.32
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    • pp.43-51
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    • 2006
  • A fluid transient analysis on the Koreasat 1 & 2 pipeline system is conducted through numerical parametric studies in which unsteady friction results are compared with quasi-steady friction results and show relatively accurate prediction of the response curve with the unsteady friction. The code developed and used in this analysis has finished verification through comparing with the original Zielke model, the full and recursive convolution model and quasi-steady model as a reference. The unsteady friction is calculated by the recursive convolution Zielke model in which a complete evolution history of velocity field is no longer required so that it makes the fluid transient analysis on the complicated system possible. The results show that the application of quasi-steady friction to model cannot predict the entire response curve properly except the first peak amplitude but the application of unsteady friction to model can predict reasonably the response curve, therefore it is to know the characteristics of the propulsion system.

A fluid transient analysis for the propellant flow with an unsteady friction in a monopropellant propulsion system

  • Chae Jong-Won;Han Cho-Young
    • 한국전산유체공학회:학술대회논문집
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    • 2006.05a
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    • pp.320-323
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    • 2006
  • A fluid transient analysis on the Koreasat 1 & 2 pipeline system is conducted through numerical parametric studies in which unsteady friction results are compared with quasi-steady friction results and show relatively accurate prediction of the response curve with the unsteady friction. The code developed and used in this analysis has finished verification through comparing with the original Zielke model, the full and recursive convolution model and quasi-steady model as a reference. The unsteady friction is calculated by the recursive convolution Zielke model in which a complete evolution history of velocity field is no longer required so that it makes the fluid transient analysis on the complicated system possible. The results show that the application of quasi-steady friction to model cannot predict the entire response curve properly except the first peak amplitude but application of unsteady friction to model can predict reasonably he response curve, therefore it is to know the characteristics of the propulsion system.

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Transient Analysis of Pipeline System Considering Unsteady Friction Models (다양한 부정류 마찰항을 고려한 관망 천이류 모의와 실험연구)

  • Jang, Il;Kim, Sang Hyun;Kim, Ji Hyun
    • Journal of Korean Society of Water and Wastewater
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    • v.22 no.6
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    • pp.657-664
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    • 2008
  • This research compared several unsteady friction models for transient analysis of pipeline system. Unsteady friction is an important factor for accurate simulation of hydraulic transient. Steady friction, quasi-steady friction, Zielke's model and two versions of Brunone model were compared with measurement data of identical pipeline conditions. This study showed that the existing simple steady friction model can be useful for the safer design of pipeline system due to its overestimation of waterhammer, but introduction of more elaborate models are required for advanced analysis such as inverse transient analysis of friction or leakage and the preliminary analysis of water quality prediction of water distribution system.

Development of Discretized Combined Unsteady Friction Model for Pipeline Systems (관수로 합성 부정류 차분화 마찰모형의 개발)

  • Choi, Rak-Won;Kim, Sang-Hyun
    • Journal of Korea Water Resources Association
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    • v.45 no.5
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    • pp.455-464
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    • 2012
  • In this study, a combined unsteady friction model has been developed to simulate the waterhammer phenomenon for the pipeline system. The method of characteristics has been employed as the modeling platform for the integration of the acceleration based model and the frequency dependant model for unsteady friction. Both Zielke's model and Ramos model were also compared with pressure measurements of a pilot plant pipeline system. In order to validate the modeling approach, a pipeline system equipped with the high frequency pressure data acquisition system was fabricated. The time series of pressure, introduced by a sudden valve closure, were obtained for two Reynolds numbers. A trial and error method was used to calibrate parameters for unsteady friction model. The comparison between different unsteady friction contributions in pressure variation provided the comprehensive understanding in the pressure damping mechanism of waterhammer. The proper evaluation of unsteady friction impact is a critical factor for accurate simulation of hydraulic transient.

EIGENVALUE APPROACH FOR UNSTEADY FRICTION WATER HAMMER MODEL

  • Jung Bong Seog;Karney Bryan W.
    • Water Engineering Research
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    • v.5 no.4
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    • pp.177-183
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    • 2004
  • This paper introduces an eigenvalue method of transforming the hyperbolic partial differential equations of a particular unsteady friction water hammer model into characteristic form. This method is based on the solution of the corresponding one-dimensional Riemann problem that transforms hyperbolic quasi-linear equations into ordinary differential equations along the characteristic directions, which in this case arises as the eigenvalues of the system. A mathematical justification and generalization of the eigenvalues method is provided and this approach is compared to the traditional characteristic method.

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Application of Levenberg Marquardt Method for Calibration of Unsteady Friction Model for a Pipeline System (관수로 부정류 마찰항 보정을 위한 Levenberg Marquardt 방법의 적용연구)

  • Park, Jo Eun;Kim, Sang Hyun
    • Journal of Korea Water Resources Association
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    • v.46 no.4
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    • pp.389-400
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    • 2013
  • In this study, a conventional pipeline unsteady friction model has been integrated into Levenberg Marquardt method to calibrate friction coefficient in a pipeline system. The method of characteristics has been employed as the modeling platform for the frequency dependant model of unsteady friction. In order to obtain Hessian and Jacobian matrix for optimization, the direct differentiation of pressure to friction factor was calculated and sensitivities to friction for heads and discharges were formulated for implementation to the integration constant in the characteristic method. Using a hypothetical simple pipeline system, time series of pressure, introduced by a sudden valve closure, were obtained for various Reynolds numbers. Convergency in fiction factors were evaluated both in steady and unsteady friction models. The comparison of calibration performance between the proposed method and genetic algorithm indicates that faster and stabler behaviour of Levenberg Marquardt method than those of evolutionary calibration.

Transient Analysis and Experiment Considering Unsteady Friction and Leakage in a Pipeline System (단일관망에서 누수효과를 고려한 천이류 분석 및 실험)

  • Lee, Mi-Hyun;Song, Yong-Sok;Kim, Sang-Hyun
    • Proceedings of the Korea Water Resources Association Conference
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    • 2006.05a
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    • pp.1395-1399
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    • 2006
  • The current paper focuses the analysis of leakage detection in water pipeline systems by means of the transient analysis. In order to obtain pressure variation for evaluation the existing methodology, an extensive experimental process has been carried out in a single pipeline system. Several experimental tests were performed with and without a leakage in the system. Using the unsteady friction and improved unsteady friction factors, reasonable match between the computed and measured pressure were presented on the condition of the flow situations. The transient method attempts to estimate the leakage in water pipelines using observed pressure data collected during transient events on the system.

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Transient Analysis and Experiment Considering Unsteady Friction and Leakage in a Pipeline System (단일관망에서 누수효과를 고려한 천이류 분석 및 실험)

  • Lee, Mi-hyun;Song, Yong-sok;Kim, Sang-hyun
    • Journal of Korean Society of Water and Wastewater
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    • v.20 no.2
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    • pp.207-214
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    • 2006
  • The current paper focuses the analysis of leakage detection in water pipeline systems by means of the transient method. In order to obtain essential data for evaluation the existing methodology, an extensive experimental process has been carried out in a single pipeline system, Several experimental tests were performed with and without a leakage in the system. Using the unsteady friction and improved unsteady friction factors gives reasonable match between the computed and measured results on the condition of the flow situations presented in the paper. The transient method attempts to estimate the leakage in water pipelines using observed pressure data collected during transient events on the system.

Analysis of instantaneous friction in full-circumferentially grooved engine main bearings (원주방향 윤활홈을 갖는 엔진 주베어링의 연속 마찰 해석)

  • 전상명
    • Journal of the korean Society of Automotive Engineers
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    • v.12 no.4
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    • pp.35-46
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    • 1990
  • The instantaneous friction in main bearings of a single cylinder diesel engine was determined by measuring the instantaneous angular velocity, calculating the resulting forces acting on the bearings, and solving the unsteady Reynolds equation in combination with the mobility method. The considered system consists of only the crankshaft with flywheel and oil pump. The thermal effects were not considered because of the short testing time. The tests were conducted using an electric start motor. The results indicated that when the bearing is not near equilibrium for very small speeds, simple film lubrication theories are not accurate. The details of grooves and unsteady terms in the Reynolds equation cannot be ignored for increasing efficiency of instantaneous friction calculation of the engine bearings. The effects of speed on instantaneous friction and energy lost in friction were determined.

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Unsteady State Heat Transfer Analysis of Drum Brake System (드럼 브레이크 시스템의 비정상 열전달 해석)

  • 이계섭;국종영;천인범
    • Transactions of the Korean Society of Automotive Engineers
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    • v.7 no.9
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    • pp.172-181
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    • 1999
  • The brakes employed on commercial vehicles must be able to withstand three types of demanding services which are use-emergency stops from high speed, many repeated stops as in a delivery or bus route, and speed control in mountain descents. Two type of friction brakes are in use ; drum breaks and disc brakes. Drum brakes are of the internally expanding type in which two shoes fitted externally with friction material are forced outward against the inside of a rotating drum on the wheel unit. In this case, the Braking power is produced by the friction force between a drum and a lining, and is converted into heat. In this research an unsteady state heat transfer analysis for drum brake system of heavy truck has been performed by ABAQUS/standard code in the case of single-braking and the repeated braking condition. The temperature histories obtained by the finite Element analysis have been compared with the result calculated by the simplified formulation and the result obtained by the experiment of real vehicle conditions.

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