• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.1026-1035
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• 1987

The injection molding process is used in the fabrication of a large variety of plastic articles. A numerical simulation of the filling stage along the thickness direction is proposed by combining the free surface boundary condition with the relevant governing equations. The mathematical model is based on the equations of continuity, momentum and energy along with inelastic power-law model and relevant boundary conditions. Due to the significant implications for microstructure development in the pro duct, the fountain effect at the advancing free surface is explicitly taken into consideration in the simulation. The model yields data on free surface shape as well as velocity, pressure, temperature and shear stress distributions within the mold cavity. The rearrangement of the velocity and temperature profiles in the vicinity of the melt front is considered in detail.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.195-198
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• 1996

This paper is studid the flow analysis of cardio vascular assist device. The experimental study is carried out to measure velocity profiles, Shear stress distributions and Velocity Vector for the flowrare of 4l/min, the frequency of 0.5Hz, the stroke volume of 60ml, the inlet and outlet pressure of 100mmHg by the L.D.V and P.I.V system. These results are agreed with the numerical simulations.

• Coupled systems mechanics
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• v.7 no.4
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• pp.373-393
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• 2018

This paper is concerned with the wave propagation behavior of rotating functionally graded temperature-dependent nanoscale beams subjected to thermal loading based on nonlocal strain gradient stress field. Uniform, linear and nonlinear temperature distributions across the thickness are investigated. Thermo-elastic properties of FG beam change gradually according to the Mori-Tanaka distribution model in the spatial coordinate. The nanobeam is modeled via a higher-order shear deformable refined beam theory which has a trigonometric shear stress function. The governing equations are derived by Hamilton's principle as a function of axial force due to centrifugal stiffening and displacement. By applying an analytical solution and solving an eigenvalue problem, the dispersion relations of rotating FG nanobeam are obtained. Numerical results illustrate that various parameters including temperature change, angular velocity, nonlocality parameter, wave number and gradient index have significant effect on the wave dispersion characteristics of the understudy nanobeam. The outcome of this study can provide beneficial information for the next generation researches and exact design of nano-machines including nanoscale molecular bearings and nanogears, etc.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.716-724
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• 1990

Oblique impinging plane jets were investigated experimentally and numerically at Reynolds number 21000. The inclination angle was varied from 90.deg.(normal to the impinging plate) to 60.deg.. The distance H between the nozzle exit and the stagnation point on the impinging plate was fixed at H/D=8. The working fluid was air. The mean velocity components and turbulent quantities were measured by a hot-wire anemometer. And the static pressure distributions on the impinging plate were measured by a Pitot tube. In numerical computation, the governing partial differential equations of elliptic type were solved with conventional k-.epsilon. turbulence model. The measurements show that, after impingement, the jet half width alone the wall increases in both directions, and that similarity for each turbulent quantity such as Reynolds shear stress or turbulent kinetic energy is revealed in the wall jet region. The computed results show some deviation from experimental data in the impingement region, where streamline curvature is significant. However, the computed results agree qualitatively well with measurements.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.9
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• pp.780-789
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• 2007

Lock-on phenomenon in the wake of a circular cylinder is investigated at the Reynolds number of 360 using direct numerical simulation (DNS). To induce lock-on, a streamwise velocity perturbation with a frequency of twice the natural shedding frequency is superimposed on the free stream velocity. The Reynolds stress distributions are investigated to analyze the streamwise force balance acting on the recirculation region and the results are compared with the previous experimental result. When the lock-on occurs, the pressure force on the recirculation region is shown to increase mainly due to the reversal of the Reynolds shear stress distribution, which is consistent with our previous results using PIV measurement. It is also shown that, with the lock-on, the strength of the primary vortices increases whereas that of the secondary vortices decreases significantly. Further, under the lock-on condition the wavelength of the secondary vortices increases by as much as 2.5 times.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.97-104
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• 2005

A simple but efficient grid generation technique by using the modified compressible form of stream function has been formulated. Transformation of a physical plane to a streamline plane, the Von Mises Transformation, has been widely used to solve the differential equations governing flow phenomena, however, limitation arises in low velocity region of boundary layer, mixing layer and wake region where the relatively large grid spacing is inevitable. Modified Von Mises Transformation with simple mathematical adjustment for the stream function is suggested and applied to solve the confined coaxial turbulent jet mixing with simple $\kappa-\epsilon$ turbulence model. Comparison with several experimental data of axial mean velocity, turbulent kinetic energy, and Reynolds shear stress distribution shows quite good agreement in the mixing layer except in the centerline where the turbulent kinetic energy distributions were somewhat under estimated. This formulation is strongly suggested to be utilized specially for free turbulent mixing layers in axisymmetric flow conditions such as the investigation of mixing behavior, jet noise production and reduction for Turbofan engines.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.3
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• pp.254-260
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• 2002

There have been many studies for the flow through internally finned tube, since the heat exchangers with fin device derive much attention in heat transfer enhance cent. In this study, analysis of laminar flow through the circular tube with longitudinal fins are investigated. The height and the number of fins are arbitrary. The flow field is assumed to be laminar and conformal mapping is used to obtain analytic solution. From the analytic solution, equi-velocity lines are shown, and the flow rate through the finned tube is calculated for various fin heights and numbers of fins. Darcy friction factor for this finned tube and shear stress distributions on the wall and fin are also considered.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.10
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• pp.102-112
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• 1995

Temperature distribution on the rake face and flank face in orthogonal turning with cutting tool of high speed steel is studied by using a finite element method and experiments. Experiments are carried out to verify the validity of the temperature measurement by using a thermoelectric couple junction imbedded in a cutting tool of high speed steel. Good agreement is obtained between the analytical results and the experimental ones for the temperature distributions on both the rake face and flank face of cutting tool with high speed steel. The analytical results show that the temperature on the top flank face of a tool is higher than it on the top rake face of the tool because of the difference of the friction velocity on each face of the tool.

• Journal of Power System Engineering
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• v.2 no.1
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• pp.31-38
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• 1998

A diffuser, an important equipment to change kinetic energy into pressure energy, has been studied for a long time. Though experimental and theoretical researches have been done, the understanding of energy transfer and detailed mechanism of energy dissipation is unclear. As far as numerical prediction of diffuser flows are concerned, various numerical studies have also been done. On the contrary, many turbulence models have constraint to the applicability of diffuser-like complex flows, because of anisotropy of turbulence near the wall and of local nonequilibrium induced by an adverse pressure gradient. The existing $k-{\epsilon}$ turbulence models have some problems in the case of being applied to complex turbulent flows. The purpose of this paper is to test the applicability of the nonlinear $k-{\epsilon}$ model concerning diffuser-like flows with expansion and streamline curvature. The results show that the nonlinear $k-{\epsilon}$ turbulence model predicted well the coefficient of pressure, velocity profiles and turbulent kinetic energy distributions, however the shear stress prediction was failed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1971-1978
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• 1992

A turbulent flow in a conical diffuser with total divergence angle of 8.deg. was numerically studied. The low Reynolds number k-.epsilon. model(Launder-Sharma model) was adopted to simulate the turbulence. The continuity and time averaged Navier-Stokes equations in a nonorthogonal coordinate system were solved by a finite volume method based on the fully elliptic formulation. The low Reynolds number k-.epsilon. model reasonably simulates the pressure recovery and the mean velocity components. However, there are also considerable discrepancies between predicted and measured shear stress distribution on the wall and turbulent kinetic energy distributions. It is necessary to investigate the flow structure at the entry of the diffuser, numerically as well as experimentally.