• Title/Summary/Keyword: lateral flow

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Feedback flow control using the POD method on the backward facing step wall model

  • Cho, Sung-In;Lee, In;Lee, Seung-Jun;Lee, Choong Yun;Park, Soo Hyung
    • International Journal of Aeronautical and Space Sciences
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    • v.13 no.4
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    • pp.428-434
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    • 2012
  • Missiles suffer from flight instability problems at high angles of attack, since vortex flow over a fuselage cause lateral force to the body. To overcome this problem at a high angle of attack, the development of a real time vortex controller is needed. In this paper, Proper Orthogonal Decomposition (POD) and feedback controllers are developed for real time vortex control. The POD method is one of the most well known techniques for modeling low order models that represent the original full-order model. An adaptive control algorithm is used for real time control.

A Study on Non-Axisymmetric Precision Forging with and without Flash (플래쉬 유무에 따른 비축대칭 정밀단조에 관한 연구)

  • 배원병;김영호;최재찬;이종헌;김동영
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1993.10a
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    • pp.218-223
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    • 1993
  • An UBET(Upper Bound Elemental Technique) program has been developed to analyze forging load, die-cavity filling and effective strain distribution for flashless forging. To analyze the process easily, it is suggested that the deformation is divided into two different parts. Those are axisymmetric part in corner and plane-strain part in lateral. The total power consumption is minimized through combination of two deformation parts by building block method, from which the upper-bound forging load, the flow pattern, the grid pattern, the veocity distribution and the effective strain are determined. To show the merit of flashless forging, the result of flashless and flash forging processes are compared through theory and experiment. Experiments have been carried out with plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agreement with the experimental results.

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Development of a Subchannel Analysis Code MATRA Applicable to PWRs and ALWRs

  • Yoo, Yeon-Jong;Hwang, Dae-Hyun;Sohn, Dong-Seong
    • Nuclear Engineering and Technology
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    • v.31 no.3
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    • pp.314-327
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    • 1999
  • A subchannel analysis code MATRA applicable to PWRs and ALWRs has been developed to be run on an IBM PC or HP WS based on the existing CDC CYBER mainframe version of COBRA-Rf-1. This MATRA code is a thermal-hydraulic analysis code based on the subchannel approach for calculating the enthalpy and How distribution in fuel assemblies and reactor cores for both steady-state and transient conditions. HATRA has been provided with an improved structure, various functions, and models to give more convenient user environment and to enhance the code accuracy. Among them, the pressure drop model has been improved to be applied to non-square-lattice rod arrays, and the models for the lateral transport between adjacent subchannels have been improved to enhance the accuracy in predicting two-phase flow phenomena. The predictions of MATRA were compared with the experimental data on the flow and enthalpy distribution in some sample rod-bundle cases to evaluate the performance of MATRA. All the results revealed that the predictions of MATRA were better than those of COBRA-IV-I.

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A Computational Study on the Unsteady Lateral Loads in a Rocket Nozzle

  • Nagdewe, Suryakant;Kim, Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.05a
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    • pp.289-292
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    • 2008
  • Highly over-expanded nozzle of the rocket engines will be excited by non-axial forces due to flow separation at sea level operations. Since rocket engines are designed to produce axial thrust to power the vehicle, non-axial static and/or dynamic forces are not desirable. Several engine failures were attributed to the side loads. Present work investigate the unsteady flow in an over-expanded rocket nozzle in order to estimate side load during a shutdown/starting. Numerical computations has been carried out with density based solver on multi-block structured grid. Present solver is explicit in time and unsteady time step is calculated using dual time step approach. AUSMDV is considered as a numerical scheme for the flux calculations. One equation Spalart-Allmaras turbulence model is selected. Results presented here is for two nozzle pressure ratio i.e. 100 and 20. At 100 NPR, restricted shock separation (RSS) pattern is observed while, 20 NPR shows free shock separation (FSS) pattern. Side load is observed during the transition of separation pattern at different NPR.

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Experimental Investigation of Unsteady Pressure Generated by Oscillating Outer Cylinder (진동하는 외부 실린더에 의해 유발되는 비정상 압력의 실험적 고찰)

  • 심우건
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.2
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    • pp.519-526
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    • 1995
  • Experiments have been performed to test the analytical tools developed concurrently for the motion-related unsteady pressure in annular passages. The outer cylindrical body was oscillated by a shaker in either rocking motion about a hinge-point or lateral translation motion. In the equilibrium configuration the two bodies are either concentric or eccentric, in the plane of oscillation or normal to it. The unsteady pressure generated by the oscillatory motion with low amplitudes (displacement/radius) was measured on wall of the fixed inner cylinder at various axial and azimuthal locations. The unsteady pressure were compared with theoretical predictions, and agreement was found to be within 10%. Experiments have been shown that the effect of flow velocity on the unsteady pressure is minimal and the pressure increases more or less with oscillatory motion, for low flow velocities (Re = 2 900).

Flow in turbulent boundary layers with coriolis force (코리올리힘 이 作용하는 亂流境界層內 의 流動 에 관한 硏究)

  • 이규한
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.2
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    • pp.181-189
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    • 1985
  • The effect of the Coriolis force on the 2-D turbulent boundary layer which is developed in the side wall of the rotating rectangular flow channel was investigated. In this study, we measured mean velocities, turbulent velocity components(axial as well as lateral ones) and Reynolds stresses of the turbulent boundary layer. For high Reynolds number flows, the turbulent boundary layer without pressure gradient is hardly affected by the rotation. For low Reynolds number flows, however, the shearing stress at suction side decreases. Consequently, the velocity near the wall become slower so that the thickness of the viscous sublayer expands. On the other hand, the velocity near the wall at pressure side turns out increased.

Rotordynamic Analysis of Compressor Labyrinth Seals (압축기용 라비린스 실의 동특성 해석)

  • 하태웅;이안성
    • Journal of KSNVE
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    • v.8 no.5
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    • pp.849-855
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    • 1998
  • An analysis of lateral hydrodynamic forces of compressor labyrinth seals is presented. Basic equations are derived using a two-control-volume model for compressible flow. Blasius' wall friction-factor formula and jet flow theory are used for the calculaton of wall shear stresses and recirculation velocity in the cavity. Linearized zeroth-order and first-order perturbation equations are developed for a small motion about the centered position by expansion in the eccentricity ratio. Integraton of the resultant first-order pressure distribution over the seal defines the rotordynamic coefficients. As an application a rotordynamic analysis of the balance drum labyrinth seal found in an ethylene regrigeration copmressor is carried out. The rotordynamic characteristic results of the labyrinth seal are presented and compared with other types of seals, honeycomb seal and smooth seal.

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STRUCTURAL INTEGRITY EVALUATION OF NUCLEAR FUEL WITH REDUCED WELDING CONDITIONS

  • Park, Nam-Gyu;Park, Joon-Kyoo;Suh, Jung-Min;Kim, Kyu-Tae;Jeon, Kyeong-Lak
    • Nuclear Engineering and Technology
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    • v.41 no.3
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    • pp.347-354
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    • 2009
  • Welding is required for a connection between two different components in the nuclear fuel of a pressurized water reactor. This work relies on a mechanical experiment and analytic results to investigate the structural integrity of nuclear fuel in a situation where some components are not welded to each other. A series of lateral vibration tests are performed in a test facility, and the test structures are examined in terms of dynamic behavior. In the tests, the displacement signal at every grid structure that sustains fuel rods is measured and processed to identify the dynamic properties. The fluid-elastic stability of the structure is also analyzed to evaluate susceptibility to a cross flow with an assumed conservative cross flow distribution. The test and analysis results confirm that the structural integrity can be maintained even in the absence of some welding connections.

Effect of Piston Shape on the Lubrication Characteristics of Hydraulic Piston Pump and Motor (피스톤 형상이 유압피스톤 펌프$cdot$모터의 윤활특성에 미치는 영향)

  • 이정오;박태조
    • Tribology and Lubricants
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    • v.10 no.3
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    • pp.47-53
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    • 1994
  • Thin film flow in the clearance between cylinder bore and axially moving compositeshape piston is analyzed to study the effect of piston shape on the lubrication characteristics of hydraulic piston pump and motor. It is shown that the piston shape significantly affect the distribution of fluid film pressure, lateral force acting on the piston and leakage flow rate in the clearance. And it is also shown that the composite-shape piston is more effective than the cylindrical piston under tilted condition to reduce the possibility of hydraulic locking. Therefore, the results of present study can be used usefully in the design-and manufacturing of hydraulic piston pump and motor.

Theoretical Prediction Method of Subcooled Flow Boiling CHF

  • Kwon, Yong-Min;Cahng, Soon-Heung
    • Proceedings of the Korean Nuclear Society Conference
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    • 1998.05a
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    • pp.449-456
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    • 1998
  • A theoretical critical heat flux (CLE) model. based on lateral bubble coalescence on the heated wall, is proposed to predict the subcooled flow boiling CHF in a uniformly heated vertical tube. The model is based on the concept that a single layer of bubbles contacted to the heated wall events a bulk liquid from reaching the wall at near CHF condition. Comparisons between the model predictions and experimental data result in satisfactory agreement within less than 9.73 % root-mean-square error by the appropriate choice of the critical void fraction in the bubbly layer. The present model shows comparable performance with the CHF look-up table of Groeneveld et al.

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