• Journal of the Korean GEO-environmental Society
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• v.15 no.3
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• pp.41-48
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• 2014

Experimental study of sedimentation and self-weight consolidation has been primary research area in dredged soil. However, good quality of the dredged soil and minimum water pollution caused by the pumping of reclaimed soil require intensive study of the flow characteristics of dredged material due to dumping. In this study, continuity and the equilibrium equations for mass flow assuming single phase was derived to simulate mass flow in dredged containment area. To optimize computation and modeling time for three dimensional geometry and boundary conditions, depth integration is applied to governing equations to consider three dimensional topography of the site. Petrov-Galerkin formulation is applied in spatial discretization of governing equations. Generalized trapezoidal rule is used for time integration, and Newton iteration process approximated the solution. DG and CDG technique were used for weighting matrix in discontinuous test function in dredged flow analysis, and numerical stability was evaluated by performed a square slump simulation. A comparative analysis for numerical methods showed that DG method applied to SU / PG formulation gives minimal pseudo oscillation and reliable numerical results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.749-757
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• 1999

Holographic interferornetric tomography can provide reconstruction of instantaneous three dimensional gross flow fields. The technique however confronts ill-posed reconstruction problems in practical applications. Experimental data are usually limited in projection and angular scanning when a field is captured instantaneously or under the obstruction of test models and test section enclosures. An algorithm, based on a series expansion method, has been developed to improve the reconstruction under the ill-posed conditions. A three-dimensional natural convection flow around two interacting isothermal cubes is experimentally investigated. The flow can provide a challenging reconstruction problem and lend itself to accurate numerical solution for comparison. The refractive index fields at two horizontal sections of the thermal plume with and without an opaque object are reconstructed at a limited view angle of 80" The experimental reconstructions are then compared with those from numerical calculation and thermocouple thermometry. It confirms that the technique is applicable to reconstruction of reasonably complex, three-dimensional flow fields.elds.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.1
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• pp.34-46
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• 2020

Computational assessment of gas-dynamic characteristics is explored for a three-dimensional counter-flow thrust vector control system in a rectangular supersonic nozzle. This convergent-divergent nozzle is designed by Method of Characteristics and its design Mach number is specially set as 2.5. Performance variations of the counter-flow vector system are illustrated by varying the gap height of the secondary flow duct. Key parameters are quantitatively analyzed, such as static pressure distribution along the centerline of the upper suction collar, deflection angle, secondary mass flow ratio, and resultant thrust coefficient. Additionally, the streamline on the symmetry plane, three-dimensional iso-Mach number surface contour, and three-dimensional turbulent kinetic energy contour are presented to reveal overall flow-field characteristics in detail.

• Journal of Digital Convergence
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• v.14 no.6
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• pp.245-251
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• 2016

A numerical model is developed to predict distributions of current density and temperature. Also the complete fuel cell performances were compared. In this study the effect of flow field design and flow direction on current density and temperature distribution as well as full cell performance. The complete three-dimensional Navier-Stokes equations were solved with convergence of electro-chemical reactions terms. In this paper, the two different flow field design were simulated, straight channel and rectangular serpentine flow channel, which is commonly used. The effect of flow direction, co-flow and counter-flow, was also analyzed. The current density and temperature is higher with abundant oxygen not fuel. Also, temperature distribution was able to be drawn by using computer simulation. In this paper, the relationship among flow pattern, flow field design and current denstity distribution.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.40-42
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• 2010

Unsteady CFD results of the backward facing step (BFS) flow field is reconstructed by the low-dimenstional modes using the POD (Proper Orthogonal Decomposition) technique. Flow responses to the blowing or suction with various frequencies and amplitudes applied at the edge of the BFS can also be analysed using the same technique. The present technique can be effectively applied to the feedback flow control device.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.309-316
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• 2010

In this study, a digital particle holographic system and its application to channel-flow measurements were investigated. A double-exposure hologram recording system that is capable of recording digital holograms in a short time interval was developed. A correlation coefficient method was used to determine the focal plane of particles. The Wiener filter was used to remove noises and improve image quality. Two-threshold and image segmentation methods were used for binary image transformation. The cross-correlation method was used for particle pairing. The developed system was employed to study channel flow fields, and the axial velocities of channel flow were measured. The measurement errors are acceptable, and this proves the feasibility of using the digital particle holographic system as a good tool for flow-field measurements.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.187-195
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• 2012

This paper deals with numerical computations of cryogenic flows around turbopump inducer. Firstly, we introduce numerical methods to compute compressible/incompressible cryogenic two-phase flow. As a validation problem, computation results of 2 dimensional/axi-symmetric cryogenic flow will be presented. In this process, various cavitation model will be compared. Finally, numerical simulation of 3 dimensional turbopump inducer will be presented.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.305-310
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• 2007

For the understanding of the complex flow characteristics in the counter-rotating axial flow fan, it is necessary to investigate the three-dimensional unsteady flow fields in the counter-rotating axial flow fan. This information is also essential for the prediction of the aerodynamic and acoustical characteristics of the counter-rotating axial flow fan. Experimental study on the three-dimensional unsteady flow in the counter-rotating axial flow fan is carried out at the design point(operating condition). Three-dimensional unsteady flow fields in the counter rotating axial flow fan are measured at the cross-sectional planes of the upstream and downstream of each rotor using the $45^{\circ}$ inclined hot-wire. Three-dimensional unsteady flow fields in the counter-rotating axial flow such as the wake, the tip vortex and the tip leakage flow are shown the form of the velocity vectors and the velocity contours.

• Tunnel and Underground Space
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• v.11 no.1
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• pp.42-58
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• 2001

In order to protect the environment from waste disposal activities, the prediction of the flux and flow paths of the contaminants from underground facilities should be assessed as accurately as possible. Especially, the prediction of the pathways and travel times of the nuclides from high level radioactive wastes in a deep repository to biosphere is one of the primary tasks for assessing the ultimate safety and performance of the repository. Since the contaminants are mainly transported with groundwater along the discontinuities developed within rock mass, the characteristics of groundwater flow through discontinuities is important for the prediction of contaminant fates as well as safety assessment of a repository. In this study, the actual fracture network could be effectively generated based on in situ data by separating geometric parameter and hydraulic parameter. The calculated anisotropic hydraulic conductivity was applied to a 3D porous medium model to calculate the path flow and travel time of the large studied area with the consideration of the complex topology in the area. Using the model, the pathways and travel times for groundwater were analyzed. From this study, it was concluded that the suggested techniques and procedures for predicting the pathways and travel times of groundwater from underground facilities to biosphere is acceptable and those can be applied to the safety assessment of a repository for radioactive wastes.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.268-271
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• 2008

In order to understand mixing characteristics of the APU combustor, sector combustor which size is 1/6 of the real combustor was manufactured. To see the inner side of combustor, Poly Carbonate material is used as a combustor riner. Turbo blower is used as a air supplying device and valves are used as controling the air flow. Maximum flow rate of the blower is 7 $m^3$/min and maximum inlet velocity is up to 100 m/s.