• Proceedings of the KSME Conference
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• 2002.08a
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• pp.389-392
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• 2002

In many industrial applications, multiphase flow analysis is the norm rather than an exception as compared to more-conventional single-phase investigation. This paper describes the implementation of the multiphase flow simulation capability in the general purpose CFD software AVL FIRE/SWIFT. The governing equations are discretized based on a finite volume method (FVM) suitable fur very complex geometry, The pressure field is obtained using the SIMPLE algorithm. Depending on the characteristics of the multiphase flow to be examined, the user can choose either the two-fluid model or an explicit interface-tracking model based on the Volume-of-Fluid approach. For truly 'multi'-phase flow problems, it is also possible to apply a hybrid model where certain phases are explicitly tracked while the other phases are handled by the two fluid model. In order to demonstrate the capability of the method, applications to the Taylor bubble flow simulations are presented.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.410-418
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• 2024

Study of flow behavior within rod bundles has been an active topic. Surface modification technologies are important parts of the design of the fourth generation reactor, which can increase the strength of the secondary flow within the rod bundle lattices. Quasi-periodic large-scale vortex structure (QLVS) is introduced by arranging micro ribs on the surface of rod bundles, which enhanced the scale of the secondary flow between the rod bundle lattices. Using computational fluid dynamics (CFD) and water experiments, the flow field distribution and drag coefficient of the rod-bundle lattices are studied. The secondary flow between the micro-ribbed rod-bundle lattice is significantly enhanced compared to the standard rod-bundle lattice. The numerical simulation results agree well with the experimental results.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.290-291
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• 2005

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.535-540
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• 2000

The objective of the present study is to visualize the pulsatile flow fields by using three-dimensional computer simulation and the PIV system. A closed flow loop system was built for the steady and unsteady experiments. The Harvard pulsatile pump was used to generate the pulsatile pressure and velocity waveforms. Conifer powder as the tracing particles was added to water to visualize the flow field. Two consecutive particle images were captured by a CCD camera for the image processing. The cross-correlation method in combination with the moving searching area algorithm was applied for the image processing of the flow visualization. The pulsatile flow fields were visualized effectively by the PIV system in conjunction with the applied algorithm. The range validation and the area interpolation methods were used to obtain the final velocity vectors with high accuracy. The finite volume predictions were used to analyze three-dimensional flow patterns in the bifurcation model. The results of the PIV experiment and the computer simulation are in good agreement and the results show the recirculation zones and formation of the paired secondary flow distal to the apex of the bifurcated model. The results also show that the branch flow is pushed strongly to the inner wall due to the inertial force effect and helical motions are generated as the flow proceeds toward the outer wall.

• Journal of Wetlands Research
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• v.19 no.4
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• pp.484-490
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• 2017

In order to examine flow characteristics according to the shape of the meandering low flow channel in the compound cross section typed straight channel, we assumed the representative channel type in Korea and confirmed the validity of the 3D numerical simulation by carrying out the hydraulic model. Based on this study, numerical simulations were also conducted on other types of river channel. As a result of the numerical model test (using the velocity value measured by the water depth observation from the hydraulic model test), it was confirmed that the numerical simulation results are in good agreement with the numerical simulation results. As a result of analyzing the flow field according to the changes in the shape of the low flow channel, it was confirmed that the secondary flow examined in the previous studies occurred. Also, it was confirmed that the maximum flow velocity point moves according to the expansion cross sectional area of flow in high flow plain. Ultimately, it is thought that it is necessary to understand the position of the water impingement (which is an important factor in river design) and the extent of the impact because the change of the channel width affects the flow.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.159-162
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• 2008

In this paper, a numerical simulation of three-dimensional flow field and heat transfer coefficient distribution are conducted for two types of gas turbine blade with plane and squealer tips. The numerical results show that gas turbine blade with squealer tip considerably changes the flow structures near the tip regions of pressure and suction sides, so the overall heat transfer coefficients on the tip and shroud with squealer tip are lower than those with the plane tip blade. Finally, the effect of tip gap clearance on the flow field and heat transfer characteristics are investigated.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.324-327
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• 2005

HydroSphere can simulate integrated surface and subsurface flow and transport. Using field experiments conducted at Canadian Forces Base Borden, in Ontario, Canada, by Abdul [1985], HydroSphere is evaluated to verify its capabilities for fully integrated surface and subsurface flow modeling. And a field scale simulation will be performed with HydroSphere, using rainfall and surface and subsurface hydrogen isotope analysis data measured at small basin, in Yu-sung, by Park et al. [2003], to verify its capabilities for fully integrated surface and subsurface flow and transport modeling.

• Wind and Structures
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• v.38 no.4
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• pp.295-307
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• 2024

The funnel-shaped vortex structure of tornadoes results in a spatiotemporally varying wind velocity (speed and direction) field. However, very limited full-scale tornado data along the height and radius positions are available to identify and reliably establish a description of complex vortex structure together with the resulting aerodynamic effects on the high-speed train (HST). In this study, the improved delayed detached eddy simulation (IDDES) for flow structures and aerodynamic pressures around an HST under tornado-like winds are conducted to provide high-fidelity computational fluid dynamics (CFD) results. To demonstrate the accuracy of the numerical method adopted in this study, both field observations and wind-tunnel data are utilized to respectively validate the simulated tornado flow fields and HST aerodynamics. Then, the flow structures and aerodynamic pressures (as well as aerodynamic forces and moments) around the HST at various locations within the tornado-like vortex are comprehensively compared to highlight the importance of considering the complex spatiotemporal wind features in the HST-tornado interactions.

• Journal of Computational Design and Engineering
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• v.1 no.3
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• pp.173-186
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• 2014

The failure of a subsea production plant could induce fatal hazards and enormous loss to human lives, environments, and properties. Thus, for securing integrated design safety, core source technologies include subsea system integration that has high safety and reliability and a technique for the subsea flow assurance of subsea production plant and subsea pipeline network fluids. The evaluation of subsea flow assurance needs to be performed considering the performance of a subsea production plant, reservoir production characteristics, and the flow characteristics of multiphase fluids. A subsea production plant is installed in the deep sea, and thus is exposed to a high-pressure/ low-temperature environment. Accordingly, hydrates could be formed inside a subsea production plant or within a subsea pipeline network. These hydrates could induce serious damages by blocking the flow of subsea fluids. In this study, a simulation technology, which can visualize the system configuration of subsea production processes and can simulate stable flow of fluids, was introduced. Most existing subsea simulations have performed the analysis of dynamic behaviors for the installation of subsea facilities or the flow analysis of multiphase flow within pipes. The above studies occupy extensive research areas of the subsea field. In this study, with the goal of simulating the configuration of an entire deep sea production system compared to existing studies, a DES-based simulation technology, which can logically simulate oil production processes in the deep sea, was analyzed, and an implementation example of a simplified case was introduced.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.11
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• pp.519-526
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• 2005

This paper presents computer simulation results for developing new type of SF$_{6}$ Circuit Breaker in terms of cold gas flow after small current interruption. This cold gas flows down a nozzle into the chamber of a circuit breaker. There are many difficult problems in analyzing the gas flow due to complex geometry, moving boundary, shock wave and so on. When predicting the dielectric capability of a gas circuit breaker after interruption, the gas pressure and density distributions due to the cold gas must be considered in addition to the electrical field imposed across the gas. A self-coded computational fluid dynamics (CFD) program is used for the simulation of cold gas flow in order to evaluate the electrical field characteristic across open contacts and transient characteristics of insulations after small current interruption.