• 한국해양공학회지
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• 제10권3호
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• pp.62-73
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• 1996

Numerical simulation is made of the three-dimensional wave breaking motion about a part of a floating offshore structure containing a circular cylinder mounted vertically onto a lower hull in regular periodic gravity wave generated by a numerical wave maker. TUMMAC-VIII finite-difference method is newly developed for such a problem. By use of density-function technique the three-dimensional wave breaking motion is approximately implenented in the framework of rectangular grid system. A porosity technique is devised for the implementation of the no-slip bydy boundary conditions. The generation of breaking waves by the interaction of incident waves with the structure is well simulated and interesting features of breaking waves are revealed with containing degree of quantitative and qualitative accuracy.

• Journal of Electrical Engineering and Technology
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• 제4권2호
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• pp.249-254
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• 2009

This article deals with the analysis of a coupling between stationary Maxwell's equations, the transient state Navier-Stokes and thermal equations. The resolution of these equations is obtained by introducing the magnetic vector potential A, the vorticity ${\xi}$, the stream function ${\psi}$ and the temperature T. The flux density, the electromagnetic thrust, the electric power density, the velocity, the pressure and the temperature are graphically visualized. Also, the influence of the frequency is presented.

• 동력기계공학회지
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• 제4권3호
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• pp.40-47
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• 2000

The turbulent flow with wake, reattachment and recirculation flow is very important from the viewpoint of engineering. But that is still difficult because of especially the unsteady problems which are related with the vehicle dynamics and the aerodynamics noise. This paper evaluate LES that can analyze about all fluid flow region including the laminar, transition and turbulent. So we compare the results of LES with those of PIV measurement and Reynolds averaging models. In conclusion, LES predicts flow behavior better than Reynolds averaging models.

• 동력기계공학회지
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• 제19권5호
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• pp.80-85
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• 2015

The unsteady-state, incompressible and three-dimensional large eddy simulation(LES) was carried out to analyze the structure of turbulent flow fields according to the operating loads of three-dimensional small-size axial fan(SSAF). LES shows the best prediction performance in comparison with any other Reynolds averaged Navier-Stokes(RANS) method because static pressure coefficients analysed by LES show a little bit larger than measurements including all flow coefficients. Also, it can be known that the wake of SSAF is divided into from axial flow to radial flow before and behind stall region according to the increase of static pressure through LES analysis.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 추계 학술대회논문집
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• pp.58-62
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• 2001

Aparallel computing environment was constructed based on Windows 2000 operating system. This cluster was configured using Fast-Ethernet system to hold up together the clients within a network domain. For the parallel computation, MPI implements for Windows such as MPICH.NT.1.2.2 and MP-MPICHNT.1.2 were used with Compaq Visual Fortran compiler which produce a well optimized executives for x86 systems. The evaluation of this cluster performance was carried out using a preconditioned Navier-Stokes code for the 2D analysis of a compressible and viscous flow around a compressor blade. The parallel performance was examined in comparison with those of Linux clusters studied previously by changing a number of processors, problem size and MPI libraries. The result from the test problems presents that parallel performance of the low cost Fast-Ethernet Windows cluster is superior to that of a Linux cluster of similar configuration and is comparable to that of a Myrinet cluster.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 춘계 학술대회논문집
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• pp.72-77
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• 2001

The computational efficiency of an shape optimization procedure is highly dependent upon the proper selection of shape representation methods and design variables. In this study, shape functions, Bezier and NURBS(non-uniform rational B-splines) curves are selected as configuration generation methods and their efficiencies on the nose shape design of high-speed air vehicles, are compared. The effects of the number of control points, weighting factors and the optimization methods when utilizing the NURBS curves, are investigated. By implementing Bezier and NURBS curves, shapes having lower drag than the optimization case utilizing the shape functions, were obtained, hence it was demonstrated that these curves have better capability in representing the configuration. Efforts will be given to improve the convergence behavior when utilizing the NURBS, hence to reduce the number of Navier-Stokes analysis calculations.

• 한국전산유체공학회지
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• 제8권4호
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• pp.26-33
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• 2003

Smart UAV Development Program, one of the 21c Frontier R&D Program sponsored by MOST(Ministry of Science and Technology), was launched in 2002 As an air vehicle for the Smart UAV, CRW(Canard Rotor/wing) concept was one of the candidates compared in trade-off study. The CRW concept has not only been proven completely but its aerodynamic characteristics not known in detail yet. Two calculation methods were adopted in this study to obtain aerodynamic data for the CRW First method was the superpose DATCOM method which is capable of three lifting sufaces, and second one is the full Navier-Stokes computation around CRW configuration using overset grid method. Basic aerodynamic characteristics of the CRW configuration was analyzed and the minimum drag level with lift to drag ratio is presented. The peculiar flow characteristics around rotor/wing and hub were also examined and considered in the configuration design.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.145-150
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• 2005

Generally, Compressible Navier-Stokes codes are used to solve high mach number flows. But, Most of high mach number flows embrace low mach number flows. This phenomenon results in low convergence rate and non-physical solution in CFD analysis. So Many researchers developed preconditioning technique to solve these problems. This Study presents how to modify previous compressible N-S computer code with little changes of structure into preconditioned compressible N-S code applying Roe's Approximate Riemann Solver. And this study show developed preconditioning code is very well operated at all mach number flows.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.1-10
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• 2005

A new approach, Multi-Objective Design Exploration (MODE), is presented to address Multidisciplinary Design Optimization (MDO) problems by CFD-CSD coupling. MODE reveals the structure of the design space from the trade-off information and visualizes it as a panorama for Decision Maker. The present form of MODE consists of Kriging Model, Adaptive Range Multi Objective Genetic Algorithms, Analysis of Variance and Self-Organizing Map. The main emphasis of this approach is visual data mining. An MDO system using high fidelity simulation codes, Navier-Stokes solver and NASTRAN, has been developed and applied to a regional-jet wing design. Because the optimization system becomes very computationally expensive, only brief exploration of the design space has been performed. However, data mining result demonstrates that design knowledge can produce a good design even from the brief design exploration.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.255-259
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• 2005

An analysis is made of flow and rocket motion during a supersonic separation stage of air-launching rocket from the mother plane. Three-dimensional Euler and Navier-Stokes equations are numerically solved to analyze the steady/unsteady flow field around the rocket which is being separated from two cases of mother plane configuration: one is an idealized ogive-cylinder body and the other is a real F-4E Phantom. The simulation results clearly demonstrate the effect of shock-expansion wave interaction between the rocket and the mother plane. As a result, a design-guideline of supersonic air-launching rocket for the safe separation is proposed.