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Design Study of a Small Scale Soft Recovery System
Ilyong Yoo,Seungsoo Lee,Chongdu Cho 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.11
A soft recovery system (SRS) is a device that stops a high speed projectile without damaging the projectile. The SRS is necessary to verify the shock resistant requirements of microelectronics and electro-optic sensors in smart munitions, where the projectiles experience over 20,000 g acceleration inside the barrel. In this study, a computer code for the performance evaluation of a SRS based on ballistic compression decelerator concept has been developed. It consists of a time accurate compressible one-dimensional Euler code with use of deforming grid and a projectile motion analysis code. The Euler code employs Roe’s approximate Riemann solver with a total variation diminishing (TVD) method. A fully implicit dual time stepping method is used to advance the solution in time. In addition, the geometric conservation law (GCL) is applied to predict the solutions accurately on the deforming mesh. The equation of motion for the projectile is solved with the four-stage Runge-Kutta time integration method. A small scale SRS to catch a 20 ㎜ bullet fired at 500 m/s within 1,600 g-limit has been designed with the proposed method.
변형격자계를 이용한 3차원 날개 주변의 비정상 유동 해석
유일용(Ilyong Yoo),이승수(Seungsoo Lee) 한국전산유체공학회 2009 한국전산유체공학회 학술대회논문집 Vol.2009 No.11
Deforming mesh should be used when bodies are deforming or moving relative to each other due to the presence of aerodynamic forces and moments. Also, the flow solver for such a flow problem should satisfy the geometric conservation law to ensure the accuracy of the solutions. In this paper, a RANS(Reynolds Averaged Navier-Stokes) solver including automatic mesh capability using TFI(Transfinite Interpolation) method and GCL is developed and applied to flows induced by oscillating wings with given frequencies. The computations are pelf armed both on deforming meshes and on rigid meshes. The computational results are compared with experimental data, which shows a good agreement.
변형 격자기법을 적용하여 Synthetic jet을 이용한 언덕(hump) 주변의 박리 유동 제어 해석
유일용(Ilyong Yoo),이승수(Seungsoo Lee) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.11
As interests on the flow control increase, various methodologies based on MEMS(Micro Electro Mechanics System) technology for flow control are developed. Researches on the flow control using MEMS devices proved its effectiveness technology for flow control are developed. Researches on the flow control using MEMS devices proved its effectiveness in aerodynamic performance, thrust vectoring and vortex breakdown. In this paper, synthetic jet is chosen out of many MEMS devices. The flow over a wall-mounted hump is calculated using RANS with two-equations turbulence models. In addition, deforming mesh method is adopted to compute flows inside the actuator module without any boundary condition models. The computational results are compared with the experimental data obtained from workshop homepage as well.
변형격자계를 이용한 3차원 날개 주변의 비정상 유동 해석
유일용(Ilyong Yoo),이병권(Byungkwon Lee),이승수(Seungsoo Lee) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.1
Deforming mesh should be used when bodies are deforming or moving relative to each other due to the presence of aerodynamic forces and moments. Also, the flow solver for such a flow problem should satisfy the geometric conservation law to ensure the accuracy of the solutions. In this paper, a RANS(Reynolds Averaged Navier-Stokes) solver including automatic mesh capability using TFI(Transfinite Interpolation) method and GCL is developed and applied to flows induced by oscillating wings with given frequencies. The computations are performed both on deforming meshes and on rigid meshes. The computational results are compared with experimental data, which shows a good agreement.
3차원 저속 압축성 유동 해석을 위한 국소 예조건화 기법 적용 연구
유일용(Ilyong Yoo),진민석(Min-Suk Jin),곽인근(Einkeun Kwak),이승수(Seungsoo Lee) 한국항공우주학회 2008 韓國航空宇宙學會誌 Vol.36 No.10
압축성 유동장 해석을 위해 개발된 전산유체역학 프로그램의 응용범위를 확장하여 비압축성 유동장을 해석하고자 할 경우 해의 수렴성에 문제가 발생할 수 있다. 이러한 수렴성 저하 문제는 지배방정식의 수학적 특성에 기인하며 예조건화 방법을 이용하면 지배방정식의 큰 수정 없이 해결할 수 있다. 본 논문은 예조건화 기법을 적용한 압축성 유동해석 프로그램을 개발하여 수렴성의 문제없이 저속의 비압축성 유동장 해석의 적용에 관한 내용을 다루고 있다. 개발된 프로그램의 정확성과 수렴특성을 확인하기 위해 정상상태의 비점성 및 충류 그리고 난류 문제에 대하여 해석하였으며 이를 실험치와 비압축성 계산치와 비교하였다. Euler codes or Navier-Stokes codes for compressible flows suffer severe degradation in convergence as Mach number approaches zero. The convergence problem arose from the wide disparity in characteristic speeds can be solved using preconditioning methods without large modifications. In this paper, a preconditioned RANS(Reynolds Averaged Navier-Stokes) solver is developed for analysis of low Mach number flows. In order to validate the method, computational examples are chosen and the results are compared with the experimental data and the existing computed results showing a good accuracy and convergence characteristics for steady inviscid, laminar and turbulent flows at low Mach number.
Lee, Okbin,Yoo, Seongjin,Park, Byungjeon,Chung, Ilyong Elsevier 2006 Information sciences Vol.176 No.15
<P><B>Abstract</B></P><P>In order to maintain load balancing in a distributed network, each node should obtain workload information from all the nodes in the network. To accomplish this, this processing requires O(<I>v</I><SUP>2</SUP>) communication complexity, where <I>v</I> is the number of nodes. First, we present a new synchronous dynamic distributed load balancing algorithm on a (<I>v</I>,<I>k</I>+1,1)-configured network applying a symmetric balanced incomplete block design, where <I>v</I>=<I>k</I><SUP>2</SUP>+<I>k</I>+1. Our algorithm designs a special adjacency matrix and then transforms it to (<I>v</I>,<I>k</I>+1,1)-configured network for an efficient communication. It requires only O(vv) communication complexity and each node receives workload information from all the nodes without redundancy since each link has the same amount of traffic for transferring workload information. Later, this algorithm is revised for distributed networks and is analyzed in terms of efficiency of load balancing.</P>
APR1400DC 원전 Cooling Tower Basin 용량 크기에 대한 고찰
이재호(Jaiho Lee),유일용(Ilyong Yoo) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
In nuclear power plants(NPPs), ultimate heat sink(UHS) ultimately removes the heat generated from component cooling water system(CCWS) and essential service water system(ESWS). The UHS of APR1400DC is designed with mechanical draft cooling towers. In this paper, design features of cooling towers for US-EPR and US-APWR are qualitatively investigated to determine basin size of the cooling tower for APR1400DC. The cooling tower basin is designed to have volume capacity capable of keeping the cooling water during 30days for safe shut-down(SS) and loss of coolant accident(LOCA) with loss of offsite power(LOOP). The cooling water capacity of APR1400DC is calculated as a function of time. The calculated cooling water capacity is used to determine the basin size of cooling tower.