• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.108-116
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• 2013

Diesel engine injector is used for spraying the fuel into the cylinder chamber. Complex phenomenon like cavitation occurs from small scale domain, highly pressurized condition and rapid injection. Flow inside the nozzle affects the whole engine performance including combustion and exhaust, therefore understanding the flow inside the injector nozzle is very important. In this paper, cylindrical and convergent-divergent nozzles are suggested for nozzle types and their influences on nozzle internal flow and nozzle outlet characteristics will be analyzed by changing their outlet diameters.

• Bulletin of the Korean Mathematical Society
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• v.38 no.2
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• pp.337-346
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• 2001

A linearization owing to Oseen originally is performed to study the recirculating Navier-Stokes flows at high Reynolds numbers. The procedure is generalized to produce higher order asymptotic expansion for the flow velocity. We call this the Oseen-type expansion of the given flow. As a concrete example, the velocity of a steady Navier-Stockes flow due to a swimming flexible sheet in two-dimensional infinite strip domain is calculated by an asymptotic expansion technic with two-parameters, the Reynolds number R and the perturbation parameter $\varepsilon$ first and then R secondly. The asymptotic result is up to second order in $\varepsilon$.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.89-92
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• 2001

This study aims at investigating the relationship between dispersion coefficient ratio to molecular diffusion coefficient (D$_{l}$ /D$_{m}$) and Peclet number (Pe) for multi-solute system in non-Darcian flow regime. Existing understanding on solute dispersion is primarily derived from one-solute system in Darcian flow regime. We found that solute dispersion in rock fractures can be characterized by the mechanism of both macrodispersion and Taylor dispersion, even for non-Darcian f]ow domain. For the Darcian flow regime even different solutes lead to the same D$_{l}$ /D$_{m}$ at same Pe. However, as the flow becomes non-Darcian, solute with a higher molecular diffusion coefficient result in higher D$_{l}$ /D$_{m}$ at tile same Pe than that with a lower diffusion coefficient.cient.

• ETRI Journal
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• v.10 no.4
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• pp.118-126
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• 1988

A numerical analysis was performed for the flow field in the vertical channels consist of dummy cards and active cards to define the hydrodynamic role of dummy card which is often installed in electronic equipment between active cards to control the cooling air distribution. For a given velocity profile at the inlet and a pressure-based boundary condition at the outlet of the computation domain, the percentage of the flow rate distribution through active channel and dummy channel formed by an active card and dummy card, respectively, were investigated. As a result of present analysis, the pecentage of flow rate through active channel increases quadraticaly with the increase of the ratio of the height of barrier to the width of the dummy channel.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.91-94
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• 2004

A numerical analysis was made to investigate the intensity diminution of a simple silencer for high pressure blast flow fields. Reynolds-Averaged Wavier-Stokes equations were solved for an axisymmetric computational domain constructed by multi block Chimera grids. A blast flow field without the silencer was also calculated to validate the present numerical method. The evolution of high pressure blast flow fields was observed by depicting calculated contours of pressure and Mach number. It was found that the tested silencer could achieve 76 percent intensity diminution.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.169-172
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• 2005

A numerical analysis was made In investigate the pressure diminution of a silencer with baffles for high pressure blast flow fields. Reynolds-Averaged Navier-Stokes equations were solved for an axisymmetric computational domain constructed by multi block Chimera grids. A blast flow field was calculated for the silencers that are with one and three baffles. The evolution of high pressure blast flow fields was observed by depicting calculated contours of pressure. It was found that the tested silencer could achieve 97.7 percent pressure diminution.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.9
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• pp.1227-1236
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• 2001

A systematic analysis is made of suboptimal control for drag reduction. The influence of the amplitude of actuation (A) and the time scale of actuation ($\Delta$t(sub)a(sup)+) is evaluated. Two wall sensing variables are employed (∂w/∂y│(sub)w and ∂p/∂z│(sub)w) with two wall actuations (${\Phi}$$_2$and ${\Phi}$$_3$). To test the suboptimal control, direct numerical simulations of turbulent channel flow at Re(sub)$\tau$=100 are performed in a spectral domain. It is found that the effect of A and $\Delta$t(sub)a(sup)+∼1. The near-wall behaviors of flow structure are analyzed to characterize the drag reduction. The size effect of the sensor/actuator is examined.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.2
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• pp.155-162
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• 2015

Abalone (Haliotis discus hannai) is a shellfish that feeds on kelp and, as a product, it can often achieve a high market value. However, the dissolved oxygen (DO) levels in coastal waters in Korea have been negatively impacted by pollution from many anthropogenic sources. Herein, a computational fluid dynamics (CFD) software package was used to analyze the distribution of the DO concentration within an abalone containment structure. A finite volume approach was used to solve the Reynolds-averaged Navier-Stokes equations combined with a $k-{\varepsilon}$ turbulence model to describe the flow. The distribution of DO was determined within the control volume domain, and the transport equations of the pollutants were interpreted using a CFD model. The CFD analysis revealed that more than 60% and 30% of the relative oxygen concentration in one and two containers, respectively, was maintained when the flow acts along the six sheets of polyethylene plates. Therefore, it is clear that the abalone plate shelters should be placed parallel to the flow.

• Journal of the Korean Society of Industry Convergence
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• v.7 no.1
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• pp.33-39
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• 2004

Viscous flows around a cooling tower fan with sweep are numerically investigated. The Navier-Stokes equations and the continuity equation are solved in the flow domain. The Reynolds stresses are modelled using the $\kappa-{\varepsilon}$ turbulence model. The governing equations are discretized with the Finite Volume Method. The pressure and the velocity are linked with the SIMPLE algorithme. Flow and pressure characteristics around the fan are investigated. The pressure sharply increases through the fan. Pressure variations on the pressure and suction sides of the fan are well represened in the calculations. The flow streamlines in the blade passage are nearly parallel to the blade.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.12
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• pp.1255-1265
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• 2001

A numerical study has been conducted to characterize the transient flow in a utility gas turbine burning natural gas. The solution domain encompasses the supply gas pressure regulator to the combustor of the gas turbine that employs multi-nozzle fuel injectors. Some results produced for verification in the present study agree suite well with the experimental ones. It is found that the total gas flow may decrease noticeably during its combustion mode change, which would be the reason of momentary combustion upset, when a reference case of opening ratios of control valves in the system is applied. Several parameters are then varied in order to make the total gas flow stable over that period of time. Results of this study may be useful to understand the unsteady behavior of combustion system burning natural gas.