• Title/Summary/Keyword: Multi-Flow

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EXTENSION OF MULTI-DIMENSIONAL LIMITING PROCESS ONTO THREE-DIMENSIONAL UNSTRUCTURED GRIDS (다차원 공간 제한 기법의 3차원 비정렬 격자계로 확장)

  • Park, J.S.;Kim, C.
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.404-411
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    • 2010
  • The present paper deals with the continuous work of extending multi-dimensional limiting process (MLP), which has been quite successfully proposed on two- and three-dimensional structured grids, onto the unstructured grids. The basic idea of the present limiting strategy is to control the distribution of both cell-centered and cell-vertex physical properties to mimic a multi-dimensional nature of flow physics, which can be formulated as so called the MLP condition. The MLP condition can guarantee a high-order spatial accuracy without yielding spurious oscillations. Recently, MLP slope limiter was proposed based on the MUSCL-type reconstruction in two-dimensional case and it can be readily extended to three-dimensional case. Through various numerical analyses and extensive computations, it is observed that the proposed limiters are quite effective in controlling numerical oscillations and very accurate in capturing both discontinuous and continuous multi-dimensional flow features on 3-D tetrahedral grids.

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Multi-dimensional Limiting Strategy for Robust, Accurate and Efficient Computations of Compressible Flows on Unstructured Meshes

  • Park, Jin-Seok;Yoon, Sung-Hwan;Kim, Chon-Gam
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03a
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    • pp.378-385
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    • 2008
  • The present paper deals with the accurate and robust limiting procedure for the multi-dimensional flow analysis on unstructured meshes. The multi-dimensional limiting process (MLP) which was successfully proposed on structured grid system is extended to unstructured meshes. Based on MUSCL-type framework on unstructured meshes, the new slope limiter is devised to satisfy the MLP condition, which is quite effective to regulate the unwanted oscillations, especially on multiple dimensions. Considering the neighborhood based on the vertex of the cell, as well as the edge, this limiting strategy captures the multi-dimensional flow features very accurately with the proper stencils. From the various numerical results, these desirable characteristics of the proposed limiting strategy are clearly shown.

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Multi-dimensional Limiting Strategy for Robust, Accurate and Efficient Computations of Compressible Flows on Unstructured Meshes

  • Park, Jin-Seok;Yoon, Sung-Hwan;Kim, Chong-Am
    • 한국전산유체공학회:학술대회논문집
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    • 2008.10a
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    • pp.378-385
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    • 2008
  • The present paper deals with the accurate and robust limiting procedure for the multi-dimensional flow analysis on unstructured meshes. The multi-dimensional limiting process (MLP) which was successfully proposed on structured grid system is extended to unstructured meshes. Based on MUSCL-type framework on unstructured meshes, the new slope limiter is devised to satisfy the MLP condition, which is quite effective to regulate the unwanted oscillations, especially on multiple dimensions. Considering the neighborhood based on the vertex of the cell, as well as the edge, this limiting strategy captures the multi-dimensional flow features very accurately with the proper stencils. From the various numerical results, these desirable characteristics of the proposed limiting strategy are clearly shown.

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An Experimental Study on the Flame Localization Characteristics and Pulsating Instability in a Radial Multi-channel (반경방향 다중 채널 내 예혼합 화염의 안정화 특성과 맥동 불안정성에 관한 실험적 연구)

  • Lee, Dae Keun;Ko, Chang-Bog
    • 한국연소학회:학술대회논문집
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    • 2013.06a
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    • pp.41-43
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    • 2013
  • In order to simulate and visually observe combustion phenomena in cylindrical radial-flow porous inert media, a radial multi-channel burner, made of transparent quartz plates, was fabricated. Flame stabilization characteristics and its pulsating instability in the burner were experimentally investigated with respect to various mixture flow rates and equivalence ratio. As a result, five different flame behaviors, such as stable flame, pulsating instability, sudden extinction, blowout and unstable extinction, were observed. Mean radial position of circularly arranged multi-flame and its averaged burning velocity were measured and then compared to the freely propagating flame. The multi-flame pulsation frequency is about several tens of Hz and it is supposed to be generated by the heat diffusion enhancement to cold pre-mixture by the intensive gas-solid interaction.

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CFD/RELAP5 coupling analysis of the ISP No. 43 boron dilution experiment

  • Ye, Linrong;Yu, Hao;Wang, Mingjun;Wang, Qianglong;Tian, Wenxi;Qiu, Suizheng;Su, G.H.
    • Nuclear Engineering and Technology
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    • v.54 no.1
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    • pp.97-109
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    • 2022
  • Multi-dimensional coupling analysis is a research hot spot in nuclear reactor thermal hydraulic study and both the full-scale system transient response and local key three-dimensional thermal hydraulic phenomenon could be obtained simultaneously, which can achieve the balance between efficiency and accuracy in the numerical simulation of nuclear reactor. A one-dimensional to three-dimensional (1D-3D) coupling platform for the nuclear reactor multi-dimensional analysis is developed by XJTU-NuTheL (Nuclear Thermal-hydraulic Laboratory at Xi'an Jiaotong University) based on the CFD code Fluent and system code RELAP5 through the Dynamic Link Library (DLL) technology and Fluent user-defined functions (UDF). In this paper, the International Standard Problem (ISP) No. 43 is selected as the benchmark and the rapid boron dilution transient in the nuclear reactor is studied with the coupling code. The code validation is conducted first and the numerical simulation results show good agreement with the experimental data. The three-dimensional flow and temperature fields in the downcomer are analyzed in detail during the transient scenarios. The strong reverse flow is observed beneath the inlet cold leg, causing the de-borated water slug to mainly diffuse in the circumferential direction. The deviations between the experimental data and the transients predicted by the coupling code are also discussed.

An experimental investigation of flow characteristics in the tangential and the multi-stage spiral inlets (접선식 및 다단식 나선 유입구 흐름 특성의 실험적 연구)

  • Seong, Hoje;Rhee, Dong Sop;Park, Inhwan
    • Journal of Korea Water Resources Association
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    • v.52 no.3
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    • pp.227-234
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    • 2019
  • The vulnerability of urban disasters is increased with the rapid urbanization and industrialization, and the extreme rainfall event is increased due to the global climate change. Urban inundation is also increased due to the extreme rainfall event beyond the capacity limit of facility for the damage prevention. The underground detention vault and the underground drain tunnel are rapidly being utilized to prevent urban inundation. Therefore, the hydraulic review and design analysis of the inlet of the underground facility are important. In this study, the water level of the approach flow according to the inflow discharge is measured and the flow characteristic of the inlet (tangential and spiral) is analyzed. For the spiral inlet, the multi-stage is introduced at the bottom of the inlet to improve the inducing vortex flow at low discharge conditions. In case of the tangential inlet, the discharging efficiency is decreased rapidly with hydraulic jump in the high flow discharge. The rising ratio of the water level in the multi-stage spiral inlet is higher than the tangential inlet, but the stable discharging efficiency is maintained at low and high discharge conditions. And the empirical formula of water level-flow discharge is derived in order to utilize inlets used in this study.

Optimal Power Scheduling in Multi-Microgrid System Using Particle Swarm Optimization

  • Pisei, Sen;Choi, Jin-Young;Lee, Won-Poong;Won, Dong-Jun
    • Journal of Electrical Engineering and Technology
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    • v.12 no.4
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    • pp.1329-1339
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    • 2017
  • This paper presents the power scheduling of a multi-microgrid (MMG) system using an optimization technique called particle swarm optimization (PSO). The PSO technique has been shown to be most effective at solving the various problems of the economic dispatch (ED) in a power system. In addition, a new MMG system configuration is proposed in this paper, through which the optimal power flow is achieved. Both optimization and power trading methods within an MMG are studied. The results of implementing PSO in an MMG system for optimal power flow and cost minimization are obtained and compared with another attractive and efficient optimization technique called the genetic algorithm (GA). The comparison between these two effective methods provides very competitive results, and their operating costs also appear to be comparable. Finally, in this study, power scheduling and a power trading method are obtained using the MATLAB program.

A study on application of aggregation method based on power flow matching technique and multi-variable control method to the power system (선로 조류 유지 기법에 근거한 계통축약 및 다변수 제어기법 적용 연구)

  • Lee, Byung-Ha;Oh, Min-Hyuk;Baek, Jung-Myoung
    • Proceedings of the KIEE Conference
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    • 2006.11a
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    • pp.342-344
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    • 2006
  • The modem enormous electric power system has made power system analysis much more complex and difficult. For effective analysis of the power system, model reduction and aggregation is required. In this paper, a new aggregation method is presented to aggregate the coherent generators in the large scale power system while matching the power flow. In order to demonstrate the effects of this aggregation method, it is applied to a small scale power system. A multi-variable control technique of $H_{\infty}$ control is also applied to enhance the dynamic stability of the aggregated power system.

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Prediction of Permeability for Multi-axial Braided Preform by Using CVFEM (검사체적 유한요소법을 이용한 다축 브레이드 프리폼의 투과율 계수 예측)

  • Y. S. Song;K. Chung;T. J. Kang;J. R. Youn
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2002.10a
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    • pp.68-70
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    • 2002
  • Prediction of 3-D permeability tensor for multi-axial preform is critical to model and design the manufacturing process of composites by considering resin flow through the multi-axial fiber structure. In this study, the in-plane and transverse permeabilities for braided preform are predicted numerically. The flow analyses are calculated by using 3-D CVFEM(control volume finite element method) for macro-unit cells. To avoid checker-board pressure field and improve the efficiency of numerical computation, a new interpolation function for velocity is proposed on the basis of analytic solutions. Permeability of a braided preform is measured through unidirectional flow experiment and compared with the permeability calculated numerically. Unlike other studies, the current study is based on more realistic unit cell and prediction of permeability is improved.

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Development of Power Flow Boundary Element Method for 3-dimensional Multi-domain Noise Analysis (3차원 다영역 공간의 소음해석을 위한 파워흐름경계요소법 개발)

  • Kim, Jong-Do;Hong, Suk-Yoon;Song, Jee-Hun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.10
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    • pp.967-974
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    • 2011
  • The direct and indirect PFBEM(power flow boundary element method) for the treatment of the 3 dimensional multi-domain problems are proposed to predict the acoustic energy density in medium to high frequency ranges. In the proposed method, the equation is derived in a matrix form by considering coupled relationships of the power flow at the interface of given domains. The proposed method can successfully obtain the analytical solutions for the problems of coupled cubes and the small-scale reverberant chamber. Then the experiment is carried out to obtain STL(sound transmission loss) by using small-scale reverberant chamber and the results are compared with analysis results.