• 한국전산유체공학회지
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• 제10권1호
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• pp.63-66
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• 2005

A computational fluid dynamics(CFD) analysis has been made for fully developed turbulent flow in a triangular bare rod bundle with a pitch to diameter ratio (P/D) of 1.123. The nonlinear turbulence models predicted the turbulence-driven secondary flow in the triangular subchannel. The nonlinear quadratic κ-ε models by Speziale[1] and Myong-Kasagi[2] predicted turbulence structure in the rod bundle fairly well. The nonlinear quadratic and cubic k-ε models by Shih et al.[3] and Craft et al.[4] showed somewhat weaker anisotropic turbulence. The differential Reynolds stress model by Launder et al.[5} appeared to over predict the turbulence anisotropy in the rod bundle.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.517-523
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• 2010

Recently, the rapid evolution of computational fluid dynamics (CFD) has enabled its key role in industries and predictive sciences. From diverse research disciplines, however, are there strong needs for integrated analytical tools for multi-phenomena beyond simple flow simulation. Based on the concurrent simulation of multi-dynamics, multi-phenomena beyond simple flow simulation. Based on the concurrent simulation of multi-dynamics, multi-physics and multi-scale phenomena, the multi-phenomena CFD technology enables us to perform the flow simulation for integrated and complex systems. From the multi-phenomena CFD analysis, the high-precision analytical and predictive capacity can enhance the fast development of industrial technologies. It is also expected to further enhance the applicability of the simulation technique to medical and bio technology, new and renewable energy, nanotechnology, and scientific computing, among others.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.567-570
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• 2010

With continuously increasing flat panel display size, uniformity of thin film deposition has been drawing more attentions and associated fabrication methodologies are being actively investigated. Since the convective flow field of mixture gas plays a significant role for deposition characteristics of thin film in an APCVD system, it is greatly important to maintain uniform distribution and consistent concentration of mixture gas species. In this paper, computational study has been performed for the improvement of flow uniformity of mixture gas in an APCVD reactor during thin film deposition process. A diffuser slit has bee designed to spread the locally concentrated gas flow exiting from the flow distributor. A uniform flow distributor has been developed which has less dependency on operating conditions for global flow uniformity

• 한국전산유체공학회지
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• 제11권4호
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• pp.9-13
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• 2006

In the present study, a numerical analysis of transient mixer flow is performed considering free surface formation. The flow patterns and free surface shape in a mixers formed by flat paddle and pitched paddle impellers are predicted. In a flat paddle mixer, two flow circulation regions are formed due to strong radial flow, whereas one large circulation is formed in a pitched paddle mixer due to axial downward flow. These differences affect the free surface evolution and shape. It is seen from the results that a flat paddle mixer gives deeper free surface at center region than a pitched paddle mixer. The free surface of 8-blades-flat-paddle mixer is also simulated to compare with the available experimental and simulation results. The present computational results agree reasonably well with the experimental data.

• 한국전산유체공학회지
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• 제13권4호
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• pp.72-79
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• 2008

This study is to investigate the air flow around a sirocco fan which is used in a range hood. The main object of the study is to improve the flow rate of the fan by analysis of unsteady 3-dimensional incompressible flow. Overall analysis is carried out using CFD method. For this, we used a commercial code, SC/Tetra, and used a sliding mesh method to give the same condition as an actual state. First, verification of the CFD results is done by comparing the experimental data with the numerical data for the suction flow rate. It is confirmed that two results are well consistent. Then for the improvent of flow rate, the effect of shape factors such as diameter ratio of fan, geometry of case, cut-off aperture and guide angle of case exit on the suction flow rate was considered. Especially, for a new design of housing, the principle of Archimedes spiral was used. The overall analysis was applied to a new design of housing, and the result showed an increase of flow rate by 10.7%.

• 한국전산유체공학회지
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• 제11권4호
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• pp.62-66
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• 2006

High-speed flight vehicle have various cavities. The supersonic cavity flow is complicated due to vortices, flow separation, reattachment, shock waves and expansion waves. The general cavity flow phenomena includes the formation and dissipation of vortices, which induce oscillation and noise. The oscillation and noise greatly affect flow control, chemical reaction, and heat transfer processes. The supersonic cavity flow with high Reynolds number is characterized by the pressure oscillation due to turbulent shear layer, cavity geometry, and resonance phenomenon based on external flow conditions. The resonance phenomena can damage the structures around the cavity and negatively affect aerodynamic performance and stability. In the present study, we performed numerical analysis of cavities by applying the unsteady, compressible three dimensional Reynolds-Averaged Navier-Stokes(RANS) equations with the ${\kappa}-{\omega}$ turbulence model. The cavity model used for numerical calculation had a depth(D) of 15mm cavity aspect ratio (L/D) of 3, width to spanwise ratio(W/D) of 1.0 to 5.0. Based on the PSD(Power Spectral Density) and CSD(Cross Spectral Density) analysis of the pressure variation, the dominant frequency was analyzed and compared with the results of Rossiter's Eq.

• Wind and Structures
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• 제34권6호
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• pp.483-497
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• 2022

Three-dimensional (3D) computational fluid dynamics (CFD) analysis of flow around a hipped-roof building representative of UK inland conditions are conducted. Unsteady simulations are performed using three variations of the k-ϵ RANS turbulence model namely, the Standard, Realizable, and RNG models, and their predictive capability is measured against current European building standards. External pressure coefficients and wind loading are found through the BS 6399-2:1997 standard (obsolete) and the current European standards (BS EN 1991-1-4:2005 and A1:20101). The current European standard provides a more conservative wind loading estimate compared to its predecessor and the k-ϵ RNG model falls within 15% of the value predicted by the current standard. Surface shear stream-traces and Q-criterion were used to analyze the flow physics for each model. The RNG model predicts immediate flow separation leading to the creation of vortical structures on the hipped-roof along with a larger separation region. It is observed that the Realizable model predicts the side vortex to be a result of both the horseshoe vortex and the flow deflected off it. These model-specific aerodynamic features present the most disparity between building standards at leeward roof locations. Finally, pedestrian comfort and safety criteria are studied where the k-ϵ Standard model predicts the most ideal pedestrian conditions and the Realizable model yields the most conservative levels.

• 한국전산유체공학회지
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• 제13권2호
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• pp.1-7
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• 2008

For Aerodynamic analysis of vehicle at altitude, 100km, the validity of governing equations based on continuum model, was reviewed. Also, as the preliminary study for the sub-orbital space plane development, a candidate geometry was suggested and computational fluid dynamic(CFD) analysis was performed for various angles of attack in subsonic and supersonic flow regimes to analyze the aerodynamic characteristics and performance. The inviscid flow analyses showed that the stall starts at angle of attack above $20^{\circ}$, the maximum drag is generated at angle of attack, $87^{\circ}$ and the maximum lift to drag ratio is about 8 in subsonic flow. In supersonic, the stall angle is about $40^{\circ}$ and the maximum drag is generated at angle of attack, $90^{\circ}$. Also, mach number distribution of re-entry vehicle was computed versus altitudes.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.773-778
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• 2014

Recently both high performance and low noise for a cooling fan used in a server computer have been required. In this study, we measured the noise characteristics for a small cooling fan used in a computer or in a server, and compared the computational data to measured ones. SC/Tetra V10 and FlowNoise V4.3 was used for the unsteady flow field and the aeroacoustic analysis, respectively. The aeroacoustic analysis results have the good agreement with measured data within 3% errors in overall SPL. In the noise spectrum, we could find the peak tonal noise at lower frequency than 1st BPF, and confirm that the reason is caused by the asymmetry of bell mouth shape.

• 한국전산유체공학회지
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• 제4권2호
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• pp.47-56
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• 1999

We developed a computer program to simulate the flow field in the presence of electro-magnetic fields. The steady, two-dimensional conservation equations for mass and momentum were solved simultaneously with Maxwell equations for electro-magnetic fields. Using this program, a numerical analysis was carried out to analyze the fluid flow in the continuous casting mold with electromagnetic brake. The effects of magnetic fields size, nozzle angle and EMBR yoke position on the flow fields in the continuous casting were investigated in the present study. The flow fields with EMBR were compared with those without EMBR. We also investigated the distribution of tracer concentration as a function of time in order to calculate their residence time in the mold with EMBR. By controlling the flow fields properly using EMBR, we can prevent the direct flow impaction on the wall which can give a damage on the mold surface and reduce surface defects of stainless steel sheet products.