GIS based Visual Expression of Marine Numerical Simulation- Flow Field and Silt Sediment as Example

Wang Rui-Fu,Chen Li-li,Bai Tao,Wang Fang-zheng 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.1

Numerical simulation has been widely applied in ocean engineering owing to its low cost, short cycle and wide application range. However, post-processing software of numerical simulation doesn’t support production specification of marine engineering and other industries, and integration production is not flexible. According to particularity of numerical simulation and user requirements, this paper took GIS as the solution to achieve dynamic visualization of numerical simulation and one-click generation of business products. Firstly, based on its characteristics, convert marine numerical simulation data into vector field represented by arrows or scalar field represented by grid. Secondly, GIS based spatial display and analysis technology is used to realize the visualization expression of marine numerical simulation data. In order to improve the effect of display and expression, we achieve rendering through symbol and color stretching mapping. Finally, we output numerical thematic map through custom map range and great map decoration function.

Ensuring Sound Numerical Simulation of Hybrid Automata

Hur, Yerang,Sim, Jae-Hwan,Kim, Je-Sung,Chai, Jin-Young Korean Institute of Information Scientists and Eng 2009 Journal of Computing Science and Engineering Vol.3 No.2

A hybrid system is a dynamical system in which states can be changed continuously and discretely. Simulation based on numerical methods is the widely used technique for analyzing complicated hybrid systems. Numerical simulation of hybrid systems, however, is subject to two types of numerical errors: truncation error and round-off error. The effect of such errors can make an impossible transition step to become possible during simulation, and thus, to generate a simulation behavior that is not allowed by the model. The possibility of an incorrect simulation behavior reduces con.dence in simulation-based analysis since it is impossible to know whether a particular simulation trace is allowed by the model or not. To address this problem, we define the notion of Instrumented Hybrid Automata (IHA), which considers the effect of accumulated numerical errors on discrete transition steps. We then show how to convert Hybrid Automata (HA) to IRA and prove that every simulation behavior of IHA preserves the discrete transition steps of some behavior in HA; that is, simulation of IHA is sound with respect to HA.

Model Concept for Simulating Mechanical Behavior of Deep Geological Repository

Pilhyeon Ju,Nakkyu Chae,Samuel Park,Taehoon Park,Seongkoo Hong,Gyosoon Kim,Yongmin Gwon,Sungyeol Choi 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

For the performance analysis of deep geological repository systems, numerical simulation with multi-physics is required, which specifically covers Thermal (T), Hydraulic (H), and Mechanical (M) behaviors in the disposal environment. Numerous simulation models have been developed so far, each of which varies in the approach and methodology for solving THM problems. Fully-coupled THM simulation codes such as ROCMAS, THAMES, and CODE_BRIGHT were mainly developed in the initial stage of DEvelopment of COupled models and their VALidation against EXperiments (DECOVALEX), with the advantage of thorough calculations consisting of correlated several variables on different physics. Due to the difficulty of solving the complex Jacobian Matrix and the following burden for the computational calculation, weakly-coupled THM models have been suggested in recent researches: TOUGH2-MP with FLAC3D, TOUGH2 with UDEC and OpenGeoSys with FLAC3D. This methodology of loose coupling allows the practical use of computational code optimized for each physics, thereby increasing the efficiency in simulation. However, these suggested models require two different numerical codes to calculate THM behaviors, which leads to several inherent issues: compatibility during maintenance, updating and dependency between two codes. In this study, therefore, the authors build a unified code for simulating THM behaviors in the deep geological repository. The concept involves the iterative sequential coupling between TH and M for calculation efficiency. As having developed the simulation code, High-level rAdiowaste Disposal Evaluation System (HADES), to describe TH behavior based on Multi-physics Object-Oriented Simulation Environment (MOOSE) software, the authors make a milestone to develop and couple the MOOSE-based new code for M behavior as Sub-app, with the previous HADES set to be Main-app. New model for M behavior will be verified with the benchmark case of DECOVALEX-THMC Task D, comparing the mechanical simulation results: stress evolution over time, profiles of stress and vertical displacement. The existing simulation results from HADES will also be updated with the coupled calculations, with regard to temperature and saturation. Additionally, the effective stress evolution can be assessed in terms of repository’s stability with Spalling Strength and Mohr-Coulomb failure criterion. This concept for new simulation model has its meaning in that it aims to demonstrate the specific methodology of loosely coupling multi-physics in unified simulation code and analyze THM complex interactions with considering mutual influence on various physics. It is expected that HADES can be renewed as an integral simulation model for deep geological repository systems by possessing the capacity for analyzing and assessing mechanical behavior.

Numerical Simulation and Experimental Research of the Flow Coefficient of the Nozzle-Flapper Valve Considering Cavitation

Lei Li,Changchun Li,Hengxuan Zhang 한국유체기계학회 2017 International journal of fluid machinery and syste Vol.10 No.2

The nozzle-flapper valves are widely applied as a pilot stage in aerospace and military system. A subject of the analysis presented in this work is to find out a reasonable range of null clearance between the nozzle and flapper. This paper has presented a numerical flow coefficient simulation. In every design point, a parameterized model is created for flow coefficient simulation and cavitation under different conditions with varying gap width and inlet pressure. Moreover, a new test device has been designed to measure the flow coefficient and for visualized cavitation. The numerical simulation and test results both indicate that cavitation intensity gets fierce initially and shrinks finally as the gap width varies from small to large. From the curve, the flow coefficient mostly has experienced three stages: linear throttle section, transition section and saturation section. The appropriate deflection of flapper is recommended to make the gap width drop into the linear throttle section. The flapper–nozzle null clearance is optionally recommended near the range of DN/16. Finally through simulation it is also concluded that the inlet pressure plays a little role in the influence on the flow coefficient.

수평 자연 개구부 면적 및 열방출률이 소규모 구획실 내 온도 분포 및 개구부 유동에 미치는 영향에 대한 전산시뮬레이션

박민영(Min Yeong Park),양지현(Ji Hyun Yang),이치영(Chi Young Lee) 한국화재소방학회 2021 한국화재소방학회논문지 Vol.35 No.3

본 연구에서는 수평 자연 개구부 면적 및 열방출률 조건이 소규모 구획실 내 온도 분포와 개구부 유동에 미치는영향을 파악하기 위해 fire dynamics simulator (FDS)를 이용하여 전산시뮬레이션을 수행하였다. 수평 자연 배연구가설치된 실규모 공연장 무대부의 축소모형을 대상으로 하였고, 개구부 면적은 0.0196, 0.1024, 0.2025 m2 (각각 바닥면적의 1, 5, 10%), 열방출률은 0.46, 1.35, 2.61 kW로 설정하였다. 개구부 면적이 감소하고 열방출률이 증가함에 따라구획실 내부 온도는 증가하였고, 열방출률이 증가함에 따라 개구부 중앙 부근에서의 속도는 증가하였다. 개구부 면적이 0.0196 m2에서 0.1024 m2로 증가한 경우 속도는 증가하였으나 0.1024 m2에서 0.2025 m2로 증가한 경우에는 큰변화가 없었다. 개구부 유동의 속도 및 온도 분포 분석 결과, 개구부 중앙에서는 유출, 개구부 주변에서는 유입이일어나는 양방향 유동 양식이 관찰되었다. 개구부를 통한 질량 유량은 개구부 면적과 열방출률이 증가함에 따라 증가하였고, 기존의 질량 유량 예측 상관식은 본 전산시뮬레이션 결과를 낮게 예측하였다. In this study, the numerical simulation to investigate the effects of horizontal natural opening areas and heat release rateson temperature distribution and vent flow in a small compartment was performed using a fire dynamics simulator. Thereduced scale model of a stage in a real scale theater with horizontal natural opening was selected for this study. Thehorizontal opening areas were 0.0196, 0.1024, and 0.2025 m2 (1, 5, and 10% of the floor area, respectively), and the heatrelease rates were 0.46, 1.35, and 2.61 kW. By decreasing the horizontal opening area and increasing the heat release rate,the temperature in the compartment increased. Additionally, by increasing the heat release rate, the average velocity near thecenter of the opening increased. For the increase in the horizontal opening area from 0.0196 to 0.1024 m2, the velocity nearthe center of the opening increased. However, when the horizontal opening area increased from 0.1024 to 0.2025 m2, thevariation in velocity was not noticeable. Considering the analyses of temperature and velocity distributions of vent flow, thebidirectional flow pattern was observed, where the outflow and inflow occurred at the center and edge of the horizontalopening, respectively. The mass flow rate through the horizontal opening increased with the increase in the horizontal openingarea and heat release rate. The previous correlation for mass flow rate under-predicted the present numerical simulation data.

Numerical Simulation and Experimental Study on Flow Forming of Laser Concave–Convex Microtexture of Cr12 Steel Surface

Xiping Yang,Yonghong Fu,Xin Kuang 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10

In this paper, Cr12 steel was taken as the research object, and laser micro melting model was established in comsol softwarebased on physical equations such as laser heat source, convection heat transfer, evaporation mobility, recoil pressure,Marangoni effect. The forming mechanism and evolution law of concave–convex microtexture morphology were studiedby numerical simulation. The research reveals the changing process of the velocity of the flow field inside the material duringthe surface deformation. In addition, it can be found from the temperature field changes under different power that thehigher the power is, the faster the surface temperature of Cr12 material increases in the process of thermal deformation. Andthe hardness of the microtexture was greatly improved after the material experienced sudden heat and cold in a very shorttime. By comparing the numerical simulation results and the experimental results, it can be found that with the increase ofpower, the height, depth and diameter of the concave–convex microtexture morphology all show an increasing trend, andthe surface geometry obtained through numerical simulation matches well with the experimental results. It indicates thatthe numerical simulation has high feasibility and can effectively reflect the forming process and morphology of concaveconvexmicrotexture.

SiC 용액 성장을 위한 수치 시뮬레이션의 최적화

김영곤,최수훈,이채영,최정민,박미선,장연숙,정성민,이명현,김영희,서원선,이원재,Kim, Young-Gon,Choi, Su-Hun,Lee, Chae-Yung,Choi, Jeung-Min,Park, Mi-Seon,Jang, Yeon-Suk,Jeong, Seong-Min,Lee, Myung-Hyun,Kim, Younghee,Seo, Won-Seon,Lee, Wo 한국결정성장학회 2017 한국결정성장학회지 Vol.27 No.3

본 연구는 SiC 용액 성장에서 Cr 40 %가 첨가된 Si melt 내부의 용액과 탄소흐름의 변화를 수치적으로 분석하여 장시간 성장과 고품질의 SiC 단결정을 얻기 위한 최적공정 조건의 설계를 목적으로 진행하였다. 수치 시뮬레이션으로는 crystal growth simulator ($CGSim^{TM}$, STR Group Ltd.)가 사용되었다. 결과적으로, 성장온도, 종자정축과 도가니축의 회전속도 및 성장 시 종자정의 위치에 따라 melt내부의 용액 흐름과 탄소흐름의 속도 및 방향이 변화함으로써 더 균일한 온도구배를 형성하여 안정적인 성장이 이루어지는 조건을 확인하였다. 그러므로, 성장조건들을 조절함으로써 시뮬레이션 상에서 실험조건의 최적화가 가능하였고 향후 실제 실험에서도 많은 도움이 될 것으로 예상된다. In this study, numerical simulation was performed to focus on optimized process condition for obtaining a long-term growth and high quality SiC crystal. It could be optimized by considering the change of fluid and a carbon flow in the Si melt added with 40 % Cr. The Crystal Growth Simulator ($CGSim^{TM}$, STR Group Ltd.) was used as a numerical simulation. It was confirmed that many parameters such as temperature, rotation speed of seed crystal and crucible, and seed position during the crystal growth step had a strong influence on the speed and direction of solution flow for uniform temperature gradient and stable crystal growth. The optimized process condition for the solution growth of SiC crystal was successfully exhibited by adjusting various process parameters in the numerical simulation, which would be helpful for real crystal growth.

태풍 마이삭과 하이선에 의한 한반도 폭풍파 수치모의

손봉교(Bongkyo Son),도기덕(Kideok Do) 한국연안방재학회 2022 한국연안방재학회지 Vol.9 No.1

In this study, we simulated storm waves induced by typhoon Maysak and Haishen in the Korean peninsula by using the third-generation numerical wave model SWAN(Simulating WAves Nearshore). We used the sea-surface wind data of KMA(Korea Meteorological Agency)’s operational meteorological model RDAPS(Regional Data Assimilation Prediction System), and JMA(Japan Meteorological Agency)’s weather forecast model JMA-MSM(Meso-Scale Model) as input forcing of the numerical wave model. In addition, the wind field of the tropical cyclone was established with JTWC(Joint Typhoon Warning Center)’s best track data for the storm wave simulation. We used two different source term options, which consider other physics of energy generation by wind and dissipation by whitecapping. Validation of the simulation result was conducted over statistical analysis with the observation data from KMA and KHOA(Korea Hydrographic and Oceanographic Agency)’s buoys. As a result, the whole scenario tended to overestimate significant wave height. The simulation result by using RDAPS as input forcing outperformed the result by using JMA-MSM. It denoted that the performance of a wave model depends on the accuracy of input forcing wind. The wind field by JTWC’s best track data was not suitable compared with the meteorological numerical model. ST6 simulated the wave height higher than Komen’s source term. However, Komen s source term simulated storm waves better than ST6 in this study, and further researches under various conditions are required to evaluate ST6 for the storm waves simulation. In the simulation of wave period parameters, it was hard to estimate the accuracy of the model, and other approaches are necessary for the evaluation.

몬테카를로 시뮬레이션방법을 이용한 환율예측분석

신동백 한국산업경제학회 2007 산업경제연구 Vol.20 No.5

1990년대에 들어와 우리나라의 금융시장은 금리 자유화, 주식시장의 개방 그리고 환율제도의 변경 및 외환시장의 개방화가 점진적으로 진행되었다. 구체적으로 지난 1990년 3월부터 고정환율제도를 포기하고 시장평균환율제도를 도입했으며 현재의 자유변동환율제도 까지 여러 단계를 거쳐오면서 금융시장의 대외개방이 빠른 속도로 진전되고 있어 그 어느 때 보다 환율을 비롯한 거시 변수들 사이의 움직임을 예의 주시할 필요가 있다. 특히 1997년에 있었던 IMF와 최근의 사건인 미국의 대 이라크공격으로 인해 국제유가의 급등과 함께 원/달러환율이 한때 1350원 대를 기록하는 등 국제사회의 불안으로 인해 국내 외환시장에 큰 불안을 가져다 주었다. 또한 최근에는 국내에서 환율의 하락으로 인한 문제점이 많이 야기되고 있다. 이러한 현실에서 본 논문의 목적은 기존의 많은 선행연구에서 주로 회귀분석, VAR, VECM의 방법으로 환율을 예측했으나, 본 연구에서는 몬테카를로시뮬레이션 방법을 통해 환율을 예측함으로써 기존의 예측방법들과 다른 방법론으로 접근을 시도하고 그 유용성을 검증하려 한다. 예측결과는 과거자료를 통해 분석하였으므로 2006년 1월의 실제관측치와 전문예측기관의 전망치를 비교함으로써 시뮬레이션 방법의 유용성을 제시할 것이다. 본 연구의 결과 몬테카를로시뮬레이션을 이용한 방법 역시 실제관측치나 전문예측기관의 예측 수치와 매우 근접한 결과를 보였다. Since the crisis of foreign exchange rales in Korea from late 1997, a significant interest has been given to the stability of the exchange rates. This paper uses a Monte Carlo simulation for forecasting of exchange rates, compares the solutions by a Monte Carlo simulation with those by a professional predicting institution's numerical analysis and 2006 January's average real data that the method is efficient as well as simple and flexible in the sense that it can be easily modified to accommodate different processes governing the underlying instruments movements. From the result of Monte Carlo simulation, We could obtain a formula of simulation. Finally, from a formula of Monte Carlo simulation to obtain future's exchange rate, 983.05. But there are a few shortcomings. First, because this study just concentrated on the existing exchange rate theory, it did not propose a new exchange model, which could effectively explain exchange rates determination and variability. Second, it did not propose a tangible exchange rates policy, but just suggests a direction of exchange rates policy. For example, for improving the autonomous function in the foreign currency market, this paper consider neither a government intervention, nor the influence of international speculative money. The paper shows that some conditions are needed in order to converge random prices into a stable status in the simulation.

Universal Power-Hardware-in-the-Loop Simulator for BLDCM and PMSM

Xu Jiaqun,Xing Meili,Zhang Hongqiang 한국자기학회 2019 Journal of Magnetics Vol.24 No.3

To improve the test efficiency and reduce the test cost, this paper presents a design method of universal power-hardware-in-the-loop (PHIL) simulator for brushless DC motor (BLDCM) and permanent magnet synchronous motor (PMSM). The actual stator winding is simulated by the power-level current source in the simulator, thus, the electric power can be interacted between the simulator and the motor driver. By the method of bilinear transform and inverse Z-transform, the line voltage based numerical models of the virtual motors are derived. Moreover, the relationship between the line voltage and phase current of the virtual motors is analyzed, which is used to calculate the phase current commands in the numerical models. Furthermore, the universal PHIL simulator is implemented and the real-time simulation is performed, and then the offline simulation with MATLAB software and the actual motor test are also performed to verify the simulator results. The simulation and experimental results show that both PMSM and BLDCM can be simulated accurately at the power level without changing any hardware of the motor driver and the simulator.