• Journal of Korean Society of Coastal and Ocean Engineers
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• 제19권5호
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• pp.476-483
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• 2007

One of the main function of Ieodo Ocean Research Station is to service the information about the weather and fishing grounds condition which are collected through calibrating convection flow and ocean current around the station. However, due to the influence of the station's structure below sea level, it is difficult to obtain the exact flow data. Therefore, it is required to research on the effect of the structure and the method to evaluate and revise the observed data. In this paper, as a basic study, it deals with the algorithm that simulate the interaction between ocean current and the station structure, followed by discussions about the way to applicate the algorithm. Through 3-dimensional computational fluid dynamics analyses (using Navier-Stokes equations with K-turbulence model), the influence of the station and submerged rocks are quantitatively evaluated, and we would suggest methods how to obtain accurate flow information from the measured rough data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제25권5호
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• pp.269-278
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• 2013

In this study, in order to examine the applicability of computational fluid dynamics with the porous model to the analysis of APR+ (Advanced Power Reactor Plus) internal flow, simulation was conducted with the commercial multi-purpose computational fluid dynamics software, ANSYS CFX V.14. In addition, among the various reactor internals, the effect of flow skirt geometry on reactor internal flow was investigated. It was concluded that the porous model for some reactor internal structures could adequately predict the hydraulic characteristics inside the reactor in a qualitative manner. If sufficient computation resource is available, the predicted core inlet flow distribution is expected to be more accurate, by considering the real geometry of the internal structures, especially located in the upstream of the core inlet. Finally, depending on the shape of the flow skirt, the flow distribution was somewhat different locally. The standard deviation of the mass flow rate (${\sigma}$) for the original shape of flow skirt was smaller, than that for the modified shape of flow skirt. This means that the original shape of the flow skirt may give a more uniform distribution of mass flow rate at the core inlet plane, which may be more desirable for the core cooling.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.228-231
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• 2008

Flow fields of a transonic centrifugal compressor are calculated using the commercial CFD code, CFX-TASCflow. Due to the transonic inlet condition, interactions between the shock wave and boundary layers and between the shock wave and tip leakage vortices generate complex flow structures and extra losses. The calculated results show that strong secondary flows due to high curvature and high rotational speed of the impeller. And streamlines near suction surface show that strong radially upward flow develops after the shock between the leading edge locations of main blade and splitter.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.168-171
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• 2008

In the present study, turbulent flows around cubic and L-shape buildings were simulated numerically. Standard ${\kappa}$-$\varepsilon$, RNG ${\kappa}$-$\varepsilon$, LES turbulence models were adopted for the present simulation. The wind pressure coefficients from these results were compared with the available experimental data. The result of RNG ${\kappa}$-$\varepsilon$ and LES turbulent models gave better prediction than that of standard ${\kappa}$-$\varepsilon$ turbulent model which is widely used in the turbulent flow simulation.

• Aerospace Engineering and Technology
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• 제1권2호
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• pp.1-10
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• 2002

Flow computations around forward sweep wing small aircraft have been conducted in this study. The main-wing of the forward-wing small aircraft is composed of two planforms: the inboard wing section with backward sweep angle which is known as strake and the outboard wing section with forward sweep angle. The geometrical discontinuity or kink generated by the combination of these two different planforms requires detailed flow analysis around wing. Four different solvers were used to calculate aerodynamic data and the accuracy of each method is examined. For the convenience of grid generation over the aircraft geometry, the overset grid method was applied. Through this calculation, the basic aerodynamic data of the forward-wing aircraft were provided and the aerodynamic characteristics of the wing is expounded.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.460-465
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• 2001

In the present study, steady and unsteady flow characteristics inside an industrial mixer with flat turbine type impeller are studied. For the flow analysis, STAR-CD is used with an automatic mesh generator developed in the present study. flow results are compared to the an available experimental data to show validity or the present simulation.

• Proceeding of EDISON Challenge
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• 제2회(2013년)
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• pp.337-342
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• 2013

이번 연구에서는 de Laval nozzle를 이용하여 다양한 유체해석 모델과 프로그램을 비교하여 그 성능을 파악하였다. de Laval nozzle은 eigenvalue에 의해 eigenvector값이 '-'와 '+'값을 동시에 갖는 물리현상을 내포하고 있으며, 압력조건에 따라 내부에서 Normal shock이 발생하게 된다. 이러한 non-linearity를 현재 우리가 주로 사용하고 있는 상용프로그램(cfx, fluent)과 EDISON, 직접 코딩한 프로그램(Matlab이용)이 얼마나 잘 표현하는지 알아보았다. 그 결과 Van Leer Vector Splitting을 이용할 경우 물리현상을 제일 잘 표현 하였다. 또한 난류 유동(Turbulence flow)을 고려하게 될 경우, Mesh가 Boundary layer를 표현할 정도로 정밀하지 못하다면 제대로 된 해석 결과를 얻을 수 없었으며, Wall 근처에서 Non-slip condition에 의해 Vortex가 형성되고, 이 Vortex가 Back flow를 유도하여 해가 수렴하는데 방해를 하게 됨을 알 수 있었다. 이를 방지하기 위해서는 유동이 잘 표현될 수 있도록 적절한 Computational environment를 형성해 주는 것이 매우 중요하다.

• Journal of the Korean Society for Heat Treatment
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• 제35권1호
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• pp.27-32
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• 2022

Microbubble technology has been widely applied in various industrial fields. Recently, research on many types of microbubble application technology has been conducted experimentally, but there is a limit in deriving the optimal design and operating conditions. Therefore, if the computational fluid dynamics (CFD) analysis of multiphase flow is used to supplement these experimental studies, it is expected that the time and cost required for prototype production and evaluation tests will be minimized and optimal results will be derived. However, few studies have been conducted on multiphase flow CFD analysis to interpret fluid flow in microbubble generators using swirl flow. In this study, CFD simulation of multiphase flow was performed to analyze the air-water mixing process and fluid flow characteristics in a microbubble generator with a dual-chamber structure. Based on the simulation results, it was confirmed that a negative pressure was formed on the central axis of rotation due to the strong swirling flow. And it could be seen that the air inside the suction tube was introduced into the inner chamber of the microbubble generator. In addition, as the high-speed mixed fluid collided with external water sucked by the negative pressure near the outlet, a large amount of microbubbles was ejected due to the shear force between the two flows flowing in opposite directions.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.789-795
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• 2005

This study proposes a modified bifurcation model with a computational fluid analysis according to variation of a bifurcation geometry. FLUENT is used for a calculation of the head losses in case of a generation and a pumping. The pressure, velocity field and turbulent intensity are simulated in a bifurcation. With consideration about these flow properties, we propose the modified model to improve a flow efficiency and reduce a sound. The proposed model is able to cut down a head loss by 45% when a generation and 36% when a pumping.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.215-222
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• 2009

In the present study, a numerical analysis on the sloshing in a tank with the harmonic motion was investigated. A VOF method was used for two-phase flows inside the sloshing tank and a source term of the momentum equation was applied for the harmonic motion. This numerical method was verified by comparing its results with the available experimental data. The sloshing in a tank causes the instability of the fluid flows and the fluctuation of the impact pressure on the tank. By these phenomena of the tank sloshing, the sloshing problems such as the failure and the noise of system can be generated. For the reduction of these sloshing problems, the various baffles such as the horizontal/vertical plate baffles and the porous baffles inside the tank are installed. With the installations of these baffles, the characteristics of the liquid behavior in the sloshing tank, the impact pressure on the wall, the amplitude of the free surface near the wall and the sloshing noise were numerically analyzed.