• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.591-597
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• 2013

Because most existing non-Newtonian models are not suitable for application to the lattice Boltzmann method, theoretical and numerical studies in this regard remain challenging. In this study, the hydrokinetic (HK) model was modified and applied to a 3D sudden contraction-expansion channel flow, and the characteristics of the HK model flow were evaluated to generate non-trivial predictions in three-dimensional strong shear flows. The HK model is very efficient for application to the lattice Boltzmann method because it utilizes the shear rate and relaxation time. However, the simulation would be unstable in a high shear flow field because the local relaxation time sharply decreases with an increase in the shear rate in a strong shear flow field. In the HK model, it may become necessary to truncate the relaxation time and non-dimensional parameter to obtain stable numerical results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.3
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• pp.374-387
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• 1999

Two-dimensional turbulent fluid flow and solidification were investigated in a continuous casting process of a steel slab with electromagnetic field. The electromagnetic field was described by the Maxwell equations. The enthalpy-porosity relation was employed to suppress the velocity within a mushy region. A revised low-Reynolds number $k-{\varepsilon}$ turbulence model was used to consider the turbulent effects. It is shown that the temperature gradient in the casting direction in the case with EMBR becomes very weak compared to that of the case without EMBR. The results also show that the velocity profiles of the case with solidification are quite different from those of the case without solidification.

• 한국가시화정보학회:학술대회논문집
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• 2006.12a
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• pp.102-108
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• 2006

The three-dimensional flows in the Weis-Fogh mechanism are studied by flow visualization and numerical simulation by the discrete vortex method. In this mechanism, two wings open, touching their trailing edges (fling), and rotate in opposite directions in the horizontal plane. The structure of the vortex systems shed from the wings is very complicated and their effects on the forces on the wings have not yet been clarified. The discrete vortex method, especially the vortex stick method, is employed to investigate the vortex structure in the wake of the two wings. The wings are represented by lattice vortices, and the shed vortices are expressed by discrete three-dimensional vortex sticks. The vortex distributions and the velocity field are calculated. The pressure is estimated by the Bernoulli equation, and the lift on the wing are also obtained.

• Journal of Ocean Engineering and Technology
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• v.25 no.3
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• pp.19-27
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• 2011

In case of constructing submerged breakwaters for the purpose of preventing coastal erosion, the number of submerged breakwaters, as well as their asymmetry is dependent on the field conditions. The aim of the present study was to examine the 3-D hydrodynamic characteristics (3-D wave field, wave height, mean water level, and mean flow) around the asymmetric submerged breakwaters using a 3-D numerical model, LES-WASS-3D, which was validated through a comparison with existing experimental data and showed fairly nice agreement. From the numerical results, the wave height, mean water level, and mean flow are discussed in relation with the variation in the breakwater length ratio.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.4
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• pp.379-388
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• 2008

A hybrid Cartesian/immersed boundary code is expanded to simulate flow field around a three-dimensional body which undergoes large dynamic deformation. Immersed boundary nodes are automatically distributed based on the edges crossing triangles on body boundary. Velocity vectors are reconstructed at those immersed boundary nodes along local normal lines to the boundary. The reconstruction of pressure is avoided using the hybrid staggered/non-staggered grid method. The developed code is validated through comparisons with other results on laminar flow over a sphere. The code is applied to simulate flow around a foil which is attached to a body of revolution and rotates under periodic deformation. The periodic variation of the tip vortex is observed and the effects of the deformation on hydrodynamic force acting on the body are investigated.

• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.206-211
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• 2003

This paper reports the numerical results for blood flow of the sac squeezed by moving actuator in the TPLS(Twin Pulse Life Support System). Blood flow in the sac is assumed to be 3-dimensional unsteady newtonian fluid. where the blood flow interacts with the sac, which is activated by the moving actuator. The flow field is simulated numerically by using the FEM code, ADINA. It is well known that hemolysis is closely related to shear stress acted on blood flow. According to this fact, we simulate four models with different speed for moving actuator and examine the distribution of shear stress for each model. Numerical results show that maximum shear stress is strongly dependent on the actuator speed.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.18 no.3
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• pp.245-256
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• 2014

This work is focused on the boundary layer and heat transfer characteristics of hydromagnetic flow over a stretching sheet with variable thickness. Steady, two dimensional, nonlinear, laminar flow of an incompressible, viscous and electrically conducting fluid over a stretching sheet with variable thickness and power law velocity in the presence of variable magnetic field and variable temperature is considered. Governing equations of the problem are converted into ordinary differential equations utilizing similarity transformations. The resulting non-linear differential equations are solved numerically by utilizing Nachtsheim-Swigert shooting iterative scheme for satisfaction of asymptotic boundary conditions along with fourth order Runge-Kutta integration method. Numerical computations are carried out for various values of the physical parameters and the effects over the velocity and temperature are analyzed. Numerical values of dimensionless skin friction coefficient and non-dimensional rate of heat transfer are also obtained.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.46-49
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• 2002

Three-dimensional flow characteristics in a liquid fuel ramjet combustor were investigated using the PIV method. The combustor has two rectangular inlets that loin a 90-degree angle each other. Three cases of test combustors are made in which those inlet angles are 30 degree, 45degree and 60 degree. The experiments were performed in a water tunnel test with the same Reynolds number as Mach 0.3 at the inlet. PIV software was developed to measure the characteristics of the flow field in the combustor. Accuracy of the developed PIV program was verified with a rotating disk experiment and standard data. The characteristics of the internal flows of the combustor are large swirling flows which appear symmetric with respect to the symmetric section. This is attributed to the fact that the flows introduced from the right and left intakes collide with each other, thus forming symmetrically large vortices. A large and complex three-dimensional recirculating flow was measured behind the intakes. An inlet angle of 30 degrees is the most suitable angle as a frame he]der in the performed experimental ranges.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.3
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• pp.181-189
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• 2000

The aerodynamic characteristics of large transport vehicle has become more and more important in recent vehicle design to improve driving performance in high speed cruising and raise the product valve with regard to a comfortable driving condition. Hence, detailed knowledge of the flow field around truck coner vane is essential to improve fuel efficiency and reduce the dirt contamination on vehicle body surface. In this study, three-dimensional flow characteristics around corner vane attached to truck cabin were computed for the steady, incompressible, and high speed viscous flow, adopting the RNG k-$\varepsilon$ turbulence model. In order to investigate the influence of configuration and structure of corner vane, computations were carried out for four cases at a high Reynolds number, Re=4.1$\times$106 (based on the cabin height). The global flow patterns, drag coefficient and the distributions such as velocity magnitude, turbulent kinetic energy around the corner vane, were examined. As a result of this study, we could identify the flow characteristics around corner vane for the variation of corner vane length and width. Also, suggest the improved structure to reduce the dirt contamination in cabin side.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.10
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• pp.1254-1264
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• 1999

A three-dimensional coupled turbulent fluid flow and solidification process were analyzed in a continuous casting process of a steel slab with Electromagnetic Brake(EMBR). A revised low-Reynolds number $k-{\varepsilon}$ turbulence model was used to consider the turbulent effects. The enthalpy-porosity relation was employed to suppress the velocity within a mushy region. The electromagnetic field was described by Maxwell equations. Tile application of EMBR to the mold region results in the decrease of the transfer of superheat to the narrow face, the increase of temperature in free surface region and most liquid of submold region, and the higher temperature gradient near the solidifying shell. The increasing magnetic flux density effects mainly to the surface temperature of the solidifying shell of narrow face, hardly to the one of wide face. It is seen that in the presence of EMBR a thicker solidifying shell is obtained at the narrow face of the slab.