• 한국전산유체공학회지
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• 제13권1호
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• pp.7-13
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• 2008

Several high resolution schemes such as OSHER, MUSCL, SMART, GAMMA, WACEB and CUBISTA are comparatively studied with respect to the accurate capturing of fluid interfaces throughout the application to two typical test cases of a translation test and a collapsing water column problem with a return wave. It is accomplished by implementing the high resolution schemes in the in-house CFD code(PowerCFD) for computing 3-D flow with an unstructured cell-centered method and an interface capturing method, which is based on the finite-volume technique and fully conservative. The calculated results show that SMART scheme gives the best performance with respect to accuracy and robustness.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.51-56
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• 2006

Several high resolution schemes such as OSHER, MUSCL, SMART, GAMMA, WACEB and CUBISTA are applied to two typical test cases of a translation test and a collapsing water column problem for the accurate capturing of fluid interfaces. It is accomplished by implementing the high resolution schemes in the in-house CFD code(PowerCFD) for computing 3-D flow with an unstructured cell-centered method, which is based on the finite-volume technique and fully conservative. The calculated results are found to show that SMART scheme gives the best performance with respect to accuracy and robustness.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2000년도 춘계 학술대회논문집
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• pp.51-59
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• 2000

The Interactions of shock wave with turbulent boundary layers in high-speed flows cause complex flowfields which result in increased adverse pressure gradients, skin friction and temperature. Accurate and reliable prediction of such phenomena is needed in designing high-speed propulsion systems. Such analyses of the complex flowfields require sophisticated numerical scheme that can resolve interactions between shock wave and boundary layers accurately. Therefore the purpose of the present. article is to introduce an accurate and efficient mixed explicit-implicit generalized Galerkin finite element method. To demonstrate the validity of the theory and numerical procedure, several benchmark cases are investigated.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.27-32
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• 2008

The laminated composite materials have been applied to various mechanical structures due to their high performance to weight ratios. In this study, we suggest a stochastic finite element scheme for the probabilistic analysis of the composite laminated plates. The composite materials consist of two different materials which constitute the matrix and fiber. The material properties in the major and minor directions are determined depending on the volume fraction of these two materials. In this study, the elastic modulus and shear modulus are considered as random and the effect of these random properties on the behavior of the composite plate is investigated. We adopt the weighted integral scheme in the formulation, which has been recognized as the most accurate method in the statistical methodologies. For verification of the proposed scheme, Monte Carlo analysis is also performed for the comparison with the proposed scheme.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.518-523
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• 2001

Vortex methods were originally conceived as a tool to model the evolution of unsteady, incompressible, high Reynolds number flows of engineering interest. Recently various methods have been proposed for simulating the diffusion in vortex methods for two-dimensional incompressible flows. We test the diffusion schemes of vortex methods. In this paper we directly compare the particle strength exchange scheme with the vorticity redistribution scheme in tenus of their accuracy and computational efficiency. Comparisons between both viscous models described are presented for short-time runs of impulsively started flows past a circular cylinder for Reynolds number of 60. The particle strength exchange scheme has been shown more accurate and efficient than the vorticity redistribution scheme.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.27-30
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• 2002

As computer capacity has been progressed continuously, the studies of the flow characteristics have been performing by the numerical methods actively. In this study, 3-dimensional unsteady incompressible Wavier-Stokes equation was solved by numerical method using the fractional step method with the fourth order compact pade' scheme to achieve high accuracy To validate the present code and algorithm, 3D flow-field around a cylinder was simulated. The drag coefficient and lift coefficient were computed and, then, compared with experiment. The present code will be tailored to LES simulation for more accurate turbulent flow analysis.

• 한국전산유체공학회지
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• 제3권2호
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• pp.65-72
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• 1998

From the Boltzmann equation with BGK approximation, a gas-kinetic BGK scheme is developed and methods for its efficient calculation, using the convergence acceleration techniques, are presented in a framework of an implicit time integration. The characteristics of the original gas-kinetic BGK scheme are improved in order for the accurate calculation of viscous and heat convection problems by considering Osher's linear subpath solutions and Prandtl number correction. Present scheme applied to various numerical tests reveals a high level of accuracy and robustness and shows advantages over flux vector splittings and Riemann solver approaches from Euler equations.

• 한국통신학회논문지
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• 제33권12A호
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• pp.1217-1224
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• 2008

갈릴레오 위성시스템의 정확한 위치 확인을 위해서는 기본적으로 정화한 반송파 추적이 이루어져야 한다. 주파수 오차를 추적하기 위한 FLL은 전파 도달 시간의 변화를 발생시키는 동적 음력에 강인하지만 정확한 반송파 추적이 어렵다. 반면 위상 오차를 추적하기 위한 PLL은 정확한 반송파 추적이 가능하지만 동적음력에 약하고 높은 동적음력에서 반송파 추적성능이 저하된다. 본 논문에서는 갈릴레오 L1F 신호에서 높은 동적응력에서도 정확한 반송파 추적이 가능하도록 FLL과 PLL의 상호 보완적인 운용과 FLL지원의 PLL 루프필터를 적용한 반송파 추적루프를 설계하였으며, 모의실험을 통하여 제안한 기법의 성능을 입증하였다.

• 한국전산유체공학회지
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• 제4권1호
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• pp.8-18
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• 1999

In devising a numerical approximation for the convective spatial transport of a fluid mechanical quantity, it is noted that the convective motion of a scalar quantity occurs in one-way, or from upstream to downstream. This consideration leads to a new scheme termed a pure upwind difference scheme (PUDS) in which an estimated value for a fluid mechanical quantity at a control surface is not influenced from downstream values. The formal accuracy of the proposed scheme is third order accurate. Two typical benchmark problems of a wall-driven fluid flow in a square cavity and a buoyancy-driven natural convection in a tall cavity are computed to evaluate performance of the proposed method. for comparison, the widely used simple upwind scheme, power-law scheme, and QUICK methods are also considered. Computation results are encouraging: the proposed PUDS sensitized to the convection direction produces the least numerical diffusion among tested convection schemes, and, notable improvements in representing recirculation of fluid stream and spatial change of a scalar. Although the formal accuracy of PUDS and QUICK are the same, the accuracy difference of approximately a single order is observed from the revealed results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권2호
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• pp.974-987
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• 2018

This paper presents a novel and efficient data transmission scheme based on mobile edge computing for the massive IoT environments which should support various type of services and devices. Based on an accurate and precise synchronization process, it maximizes data transmission throughput, and consistently maintains a flow's latency. To this end, the proposed efficient software defined data transmission scheme (ESD-DTS) configures and utilizes synchronization zones in accordance with the 4 usage cases, which are end node-to-end node (EN-EN), end node-to-cloud network (EN-CN), end node-to-Internet node (EN-IN), and edge node-to-core node (EdN-CN); and it transmit the data by the required service attributes, which are divided into 3 groups (low-end group, medium-end group, and high-end group). In addition, the ESD-DTS provides a specific data transmission method, which is operated by a buffer threshold value, for the low-end group, and it effectively accommodates massive IT devices. By doing this, the proposed scheme not only supports a high, medium, and low quality of service, but also is complied with various 5G usage scenarios. The essential difference between the previous and the proposed scheme is that the existing schemes are used to handle each packet only to provide high quality and bandwidth, whereas the proposed scheme introduces synchronization zones for various type of services to manage the efficiency of each service flow. Performance evaluations show that the proposed scheme outperforms the previous schemes in terms of throughput, control message overhead, and latency. Therefore, the proposed ESD-DTS is very suitable for upcoming 5G networks in a variety of massive IoT environments with supporting mobile edge computing (MEC).