• 한국전산유체공학회지
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• 제14권1호
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• pp.18-23
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• 2009

A novel adaptive mesh refinement(AMR) strategy based on the Moment-of-Fluid(MOF) method for volume-tracking dynamic interface computation is presented. The Moment-of-Fluid method is a new interface reconstruction and volume advection method using volume fraction as well as material centroid. The adaptive mesh refinement is performed based on the error indicator, the deviation of the actual centroid obtained by interface reconstruction from the reference centroids given by moment advection process. Using the AMR-MOF method, the accuracy of volume-tracking computation with evolving interfaces is improved significantly compared to other published results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.39-41
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• 1993

This paper presents the development of interactive graphical software for the educational purpose of power flow(PF) calculation. The developed software is specially designated to give a beginner the interest on PF problem as well as to increase the understanding of it with ease. the software developed in this paper is basically composed of the pull-down menu driver, in which various functions, such as Program Master, Data File Management, Case Study Option, PF Run and View Output, are prepared to handle the software easily and thus to be familiar with power flow calculation. A special design is also considered for interactive operation of the software, wi th which user can interrupt the computation process of PF to control the convergency of PF algorithm, With this function begineer can acquire the understanding of convergency characteristics and numerical sensitivity of PF algorithm as well as basic concept of its computation logic. Futhermore, various graphic illustrations is also provided to review and compare the computation results on monitor.

• 설비공학논문집
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• 제15권11호
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• pp.910-917
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• 2003

Fluid flow in a rectangular duct for 90$^{\circ}$ bend elbow with the ratio of 1.5 between its curvature radius and width is measured by 5 W laser doppler velocity meter. The fluid flow is also computed by commercial software of STAR-CD for comparison between measured and computed velocity profiles in the duct. Reynolds numbers for the comparison are 11,643, 19,746 and 24,260. From the comparison, computation of principal velocity components in the duct predicts the experimental data somewhat satisfactorily even though those of minor velocity components and turbulent kinetic energy do not match with the experimental data quite well. K-factor for the bend elbow is computed to be average 0.086 while the equivalent ASHRAE data is 0.07.

• 대한수학회논문집
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• 제10권3호
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• pp.767-781
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• 1995

In this paper we present computation of a reflected shock in the hypersonic flow of air with chemical reactions. We consider two dimensional steady inviscid hypersonic flow of air around bodies including chemical reaction effects. At a high Mach number, a strong shock is formed in front of the body when a wedge is placed against the flow. In front of the shock, temperature and pressure increase greatly and the flow is in nonequilibrium state. If the shock hits a wall, then a reflected shock is formed in the nonequilibrium flow region. Behind this reflected shock, the temperature and pressure are very high. We carry out the computation of the reflected shock and the flow behind it. The jump conditions at the reflected shock are presented. A technique combining smooth transforms of domain and implicit difference methods is used to overcome numerical difficulties associated with the lack of resolution behind the shock and near the body.

• 대한기계학회논문집B
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• 제27권5호
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• pp.628-634
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• 2003

We present numerical and experimental results of periodic flows inside a rectangular container under a background rotation. The periodic flows are generated by changing the speed of rotation periodically so that a time-periodic body forces produce the unsteady flows. In numerical computation, a parallel-computation technique with MPI is implemented. Flow visualization and PIV measurement are also performed to obtain velocity fields at the free surface. Through a series of numerical and experimental works, we aim to clarify, if any, the fundamental reasons \ulcornerf discrepancy between the two-dimensional computation and the experimental measurement, which was detected in the previous study for the same flow model. Specifically, we check if the various assumptions prerequisite for the validity of the classical Ekman pumping law are satisfied for periodic flows under a background rotation.

• 한국전산유체공학회지
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• 제14권3호
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• pp.25-32
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• 2009

The present paper focuses on the analysis of aero-acoustics characteristic by appling different four boundary conditions. The high-order and high-resolution numerical schemes are used for discrete accurate computation of compressible flow. The four boundary conditions include extrapolation, characteristic boundary condition, zonal characteristic boundary condition. These boundary conditions are applied to the computation of two dimensional circular cylinder flows with Mach number of 0.3 and Reynolds number of 400. The computation results are validated against measurement data and other computation results for the Strouhal frequency of vortex shedding, the mean drag coefficient and root-mean-square lift for the unsteady periodic flow regime. The characteristics of secondary frequency is predicted by three kinds of boundary conditions.

• 설비공학논문집
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• 제21권5호
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• pp.282-290
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• 2009

A ceramic monolith heat exchanger is studied to find the performance of heat transfer and pressure drop by numerical computation and $\xi$-NTU method. The numerical computation was performed throughout the domain including fluid region in exhaust gas-side rectangular ducts, ceramic core and fluid region in air-side rectangular duct with the air and exhaust in cross flow direction. In addition, the heat exchanger was also analyzed to estimate the performance by conventional $\xi$-NTU method with several Nusselt number correlations for flow in rectangular duct from literature. By comparisons of both performances by the numerical computation and the $\xi$-NTU method, the effectiveness by $\xi$-NTU method was closest to the result by numerical computation within a relative error of 2.14% when Stephan's Nusselt number correlation was adopted to the $\xi$-NTU method among the several correlations.

• 설비공학논문집
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• 제15권12호
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• pp.1095-1102
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• 2003

Flow characteristics of turbulent steady fluid flow past a cylinder in rectangular duct are measured by 5 W laser doppler velocity meter. The fluid flow is also computed by commercial software of STAR-CD for comparison between the measurement and computation. The turbulent models applied in the computations are standard K-epsilon model, RNG K-epsilon model and Chen K-epsilon model. Acurracy of standard K-epsilon model is a little bit better than acurracies of other models even though those models have almost the same order of error compared to measured data. The computations predict satisfactorily the measured velocity profiles at middle section of the circular cylinder before the fluid flow diverges. However, there are some disagreements between them at down stream from the circular cylinder.

• 대한기계학회논문집B
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• 제31권9호
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• pp.814-821
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• 2007

A hybrid method is presented for efficient computation of turbulent flow noise at low Mach numbers. In this method, the turbulent flow field is computed by incompressible large eddy simulation (LES), while the acoustic field is computed with the linearized perturbed compressible equations (LPCE) derived in this study. Since LPCE is computed on the rather coarse acoustic grid with the flow variables and source term obtained by the incompressible LES, the computational efficiency of calculation is greatly enhanced. Furthermore, LPCE suppress the instability of perturbed vortical mode and therefore secure consistent and stable acoustic solutions. The proposed LES/LPCE hybrid method is applied to three low Mach number turbulent flow noise problems: i) circular cylinder, ii) isolated flat plate, and iii) interaction between cylinder wake and airfoil. The computed results are closely compared with the experimental measurements.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.7-8
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• 2006

The governing equations for high-speed lateral atomizing injector nozzle flow based on the LES-VOF model in conjunction with the CSF model are presented, and then an integrated parallel computation are performed to clarify the detailed atomization process of a high speed nozzle flow and to acquire data which is difficult to confirm by experiment such as atomization length, liquid core shapes, droplets size distributions, spray angle and droplets velocity profiles. According to the present analysis, it is found that the atomization rate and the droplets-gas two-phase flow characteristics are controlled by the turbulence perturbation upstream of the injector nozzle, hydrodynamic instabilities at the gas-liquid interface, shear stresses between liquid core and periphery of the jet. Furthermore, stable and a high-resolution computation can be attained in the high density ratio (pl/ pg = 554) conditions conditions by using our numerical method.