• Bulletin of the Society of Naval Architects of Korea
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• v.23 no.1
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• pp.13-22
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• 1986

Axisymmetric turbulent thick boundary layers on a rotating body of revolution are calculated numerically in the paper. Richardson number is introduced to the mixing length to take account of swirl effects on Reynolds stresses. Interactions of the boundary layer and the external potential flow are included by adding the displacement thickness of boundary layers on the original body. Pressure distributions on the body surface are estimated by integrating normal momentum equation across the boundary layer. A model is designed and tested in the wind tunnel. Mean velocities are measured. Through the present study, swirl effects on the thick axisymmetric boundary layer development are considerable in comparison with those of non-totating cases. Rotational motion generally increase boundary layer thickness, axial skin friction coefficients, and form drags. Circumferential flow can be reversed to induce negative skin friction when the section area is reduced.

• Journal of Ocean Engineering and Technology
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• v.22 no.3
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• pp.1-7
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• 2008

In this study, a mathematical model for flaw with silt protector is proposed that adds a second-order energy loss term in the momentum equation. The three-dimensional numerical model was developed based on mathematical models and verified through comparison with flume test results. Loss coefficients were evaluated through the flume tests and applied to the numerical model. It was found through the investigation of various example cases that the downstream flow pattern was affected mainly by penetration of the silt curtain, not by the approach velocity, and also that the blocking effect of velocity was increased by the increase in mesh density of the silt curtain, below a certain mesh density. The blocking effect did not increase further above a certain mesh density.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.813-815
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• 2000

This paper is concerned with the development of PC based computer simulation and design tools for auto-expansion SF6 circuit breaker with the arc rotary. The simulation model takes into account radiation transport, turbulence enhanced momentum. energy transport. The conversation gas dynamic equation together with Maxwells equations are solved. For the arc simulation the straightforward procedure has been used. The temperature, gas density and velocity space distributions within the circuit breaker are simulated in details. The presented results show that the computer simulation of gas flow in SF6 interrupter is a subject of much interest for design and optimization of contacts. The presented results show that the shape and sizes of contacts are chosen by this tool from judiciously compromise between electrical breakdown strength and interruption ability that are functions of gas flow parameters.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.213-216
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• 2010

A typical unsteady internal ballistic analysis model was proposed to take account of the erosive burning for a solid rocket motor. The variance of local velocity and pressure along grain surface are analyzed by using the continuity and momentum equation. The model introduced in this study showed good agreements with the results of previous internal ballistics program. It was investigated that the change of combustion pressure, gas velocity and regrestion rate along the grain axis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.12
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• pp.945-953
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• 2008

Laminar film condensation of saturated vapor in forced flow over a flat plate is analysed. The problem is formulated as exact boundary-layer solution and integral approximate solution. From numerical solutions of the governing equations, it is found that the energy transfer by convection and the effect of inertia term in the momentum equation in negligibly small for low pressure but quite important for high pressure. The condensate rate, liquid-vapor interfacial shear stress and local heat transfer are strongly dependent on the reduced pressure $P_r$ and the modified Jacob number Ja/Pr.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.358-362
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• 2003

Numerical simulation is conducted to clarify the heat transfer and fluid flow characteristics of HVAC(Heating, Ventilating and Air-Conditioning} for double-deck train. The HVAC system is installed under the roof of carbody. In the lay-out of HVAC system, air duct must be installed to supply air to 1st and 2nd floor respectively. The standard k-epsilon turbulent models and SIMPLEC algorithm based on finite volume method are used to solve the physical HVAC model. To assure convergence, QUICK scheme for momentum equation and the first order upwind scheme for turbulent equations are used. From the results of simulation, the temperature and velocity magnitude are also distributed uniformly in the interior of passenger car.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.167-173
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• 2003

For the measurement of mass flow rate at a wide range of operation conditions, it is required that the critical nozzle gas different diameters, since the mass flow rate through the critical nozzle depends on the nozzle supply conditions and the nozzle throat diameter. In the present study, both computational and experimental investigations are performed to explore the variable critical nozzle. Computational work using the 2-dimensional, axisymmetric, compressible Navier-Stokes equations are carried out to simulate the gas flow through variable critical nozzle. In experimnet, a cylinder with several different diameters is inserted into the critical nozzle to vary the nozzle throat diameter. Computational results are compared with the experimented ones. The computed results are in close agreement with experiment. It is found that the displacement and momentum thickness of variable critical nozzle are given as a function of Reynolds numbers. The discharge coefficient of the variable critical nozzle is predicted using an empirical equation.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.231-237
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• 2003

A numerical study has been conducted to investigate the effect of an inlet flow pulsation on mixing of two solutions with different concentrations in a micro conduit. We treat an unsteady, incompressible and two-dimensional flow through a micro conduit by adopting the momentum equations with the electrostatic force due to streaming current and the concentration equation. The feasibility of the inlet flow pulsation to enhance the mixing process inside the micro conduit is carefully examined by varying the inlet pulsation frequency. When a low-frequency pulsation is induced at the inlet, the interface between two solutions with different concentrations becomes wavy, which results in mixing enhancement. As the pulsation frequency increases, the waviness of the interface becomes meager, and the concentration gradients at the interface approach the value for the non-pulsating steady flow.

• Journal of Ocean Engineering and Technology
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• v.26 no.5
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• pp.55-62
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• 2012

In this paper, the rigid lid boundary condition is applied to simulate the influence of floating structures such as ships or pontoons, and the pressure term in both the momentum equations and continuity equation are modified. The pressure of a floating structure under the free surface is dependent on the draft of the structure, generally called a ship. If the free surface is covered by a floating structure, the free surface cannot move freely. The water level should be fixed, using a rigid lid boundary condition. This boundary condition is implemented by reducing the storage area of the grid cell with a factor between zero and one. The numerical model developed by Hong (2009) is verified through a comparison with experimental results, and the influence of the reduction factor is investigated using the verified numerical model.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.43-48
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• 2013

In this paper, magnetic buoyancy force on nonmagnetic solid object submerged in magnetic liquid was simulated and measured. For the evaluation of the force, a multi-physics approach of hydrostatic equilibrium considering magnetic body force as well as gravity is presented. The magnetic body force should be regarded as an additional forcing term in the momentum equation of hydrodynamics. It is also shown that the virtual air-gap based Kelvin's force formula is a useful method for the calculation of force distribution in the magnetic liquid. The experimental result which was performed by a load-cell measurement system agreed quantitatively well with the numerical one.