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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Mechanical Engineers B
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Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 21, Issue 12 - Dec 1997
Volume 21, Issue 11 - Nov 1997
Volume 21, Issue 10 - Oct 1997
Volume 21, Issue 9 - Sep 1997
Volume 21, Issue 8 - Aug 1997
Volume 21, Issue 7 - Jul 1997
Volume 21, Issue 6 - Jun 1997
Volume 21, Issue 5 - May 1997
Volume 21, Issue 4 - Apr 1997
Volume 21, Issue 3 - Mar 1997
Volume 21, Issue 2 - Feb 1997
Volume 21, Issue 1 - Jan 1997
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Numerical algorithm with the concept of defect correction for incompressible fluid flow analysis
Gwon, O-Bung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 3, 1997, Pages 341~349
DOI : 10.22634/KSME-B.19220.127.116.111
The characteristics of defect correction method are discussed in a sample heat conduction problem showing the numerical solution of the error correction equation can predict the error of the numerical solution of the original governing equation. A way of using defect correction method combined with the existing algorithm for the incompressible fluid flow, is proposed and subsequently tested for the driven square cavity problem. The error correction equations for the continuity equation and the momentum equations are considered to estimate the errors of the numerical solutions of the original governing equations. With this new approach, better velocity and pressure fields can be obtained by correcting the original numerical solutions using the estimated errors. These calculated errors also can be used to estimate the orders of magnitude of the errors of the original numerical solutions.
Numerical simulation of unsteady flow field behind bluff body
Ryu, Myeong-Seok ; Gang, Seong-Mo ; Kim, Yong-Mo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 3, 1997, Pages 350~357
DOI : 10.22634/KSME-B.1918.104.22.1680
The transient incompressible flow behind the axisymmetric bluff body is numerically simulated using the random vortex method(RVM). Based on the vorticity formulation of the unsteady Navier-Stokes equations, the Lagrangian approach with a stochastic simulation of diffusion using random walk technique is employed to account for the transport processes of the vortex elements. The numerical solutions for 2-dimensional recirculating flow behind a backward-facing step in the laminar range of Reynolds number are compared with experimental data. The present simulation focuses on the transitional flow regime where the recirculation zone behind the bluff body becomes highly unsteady and large-scale vortex eddies are shed from the bluff body wake due to intrinsic shear layer instabilities. The unsteady vertical flow structures and the mixing characteristics behind the bluff body are discussed in detail.
A fundamental study of hydrogen supplemented natural gas vehicle to meet ULEV
Kim, Bong-Seok ; Lee, Yeong-Jae ; Ryu, Jeong-In ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 3, 1997, Pages 358~370
DOI : 10.22634/KSME-B.1922.214.171.1248
In the present study, investigations were carried out to obtain data on combustion characteristics of methane gas and hydrogen supplemented methane gas in a constant volume combustion chamber. The main results obtained from the study can be summarized as follows. The maximum combustion pressure increases as the initial pressure and hydrogen supplement rate increase, the total burning time is shorten by lowering the initial pressure and by increasing the hydrogen supplement rate. The maximum flame temperature and NO concentration increase by the initial pressure and hydrogen supplement rate increase. The flame propagation processes in near stoichiometric mixture are propagated with a spherical shape, but in excess rich or lean mixtures are propagated with a elliptical shape. And, they are changed an unstable elliptical shape flame with very regular cells by increasing the hydrogen supplement rate.
Similarity analysis of a forced uniform flow impinging on a rotating disk in a vapor deposition process
Song, Chang-Geol ; Hwang, Jeong-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 3, 1997, Pages 371~379
DOI : 10.22634/KSME-B.19126.96.36.1991
A theoretical study for a forced uniform flow impinging on a rotating disk, typically involved in Chemical Vapor Deposition(CVD) and Vapor-phase Axial Deposition(VAD) processes, has been carried out. A set of exact solutions for flow and temperature fields are developed by employing a similarity variable obtained from force balance on a control volume near the disk. The solutions depend on the rotating speed of the disk, .omega., and the forced flow speed toward the disk, a. For constant forced flow speed, the overall boundary layer thickness decreases when the rotating speed increases. Approximately 5%, 15%, and 30% decreases of the thickness are obtained for .omega./a = 2, 5, and 10, respectively, compared to the case of .omega./a = 0 (axisymmetric stagnation point flow). For constant rotating disk speed the boundary layer thickness immediately decreases as the forced flow speed increases, compared to the case of .omega./a .rarw. .inf. (induced flow near a rotating disk). Effects of .omega. and a on heat transfer coefficient are studied and explained with the boundary layer characteristics.
A two dimensional analysis of the evolution of the particle size distribution in particle laden high temperature jet flows including the effects of coagulation and buoyancy
Lee, Bang-Won ; Choe, Man-Su ; Hwang, Jeong-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 3, 1997, Pages 380~391
DOI : 10.22634/KSME-B.19188.8.131.520
A numerical study has been done on the evolution of particle size distribution in particle laden high temperature jet flows undergoing convection, diffusion, thermophoresis and coagulation. The dynamic behavior of these particles have been modelled by approximating the particle size distribution by a lognormal function throughout the process and the moments of the particle size distribution have been used to solve the general dynamic equation. The size distributions of spherical particles in the radial and axial direction have been obtained including the effect of buoyancy. Of particular interests are the variations of geometric mean diameter, number concentration and polydispersity. Results show that buoyancy significantly alters the size distribution in both axial and radial direction. One dimensional analysis for non-spherical particles has also been done and the results have been compared with the existing experimental data.
Analysis of flow in a square cavity with an oscillating top wall
Min, Byeong-Gwang ; Jang, Geun-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 3, 1997, Pages 392~404
DOI : 10.22634/KSME-B.19184.108.40.2062
The flow induced by the oscillatory motion of a solid body is important in a number of practical problems. As the solid boundary oscillates harmonically, there is steady streaming motion invoked by the Reynolds stresses, which could cause extensive migration of the fluid during a period of fluid motion. We here analyzed the flow in a square cavity with an oscillating top wall for the parameters which make the time derivatives and the convective terms equally important in the entire cavity flow. The full Navier-Stokes equations are solved by the second-order time accurate Momentum Coupling Method which is devised by the authors. The particular numerical scheme does not need subiteration at each time step which is usually a required process to calculate the incompressible Navier-Stokes equations. The effect of two parameters, the Reynolds number and the frequency parameter, on the oscillatory flow has been investigated.
Thermal optimization of the chip arrangement in the PCB channel using genetic algorithm
Baek, Chang-In ; Lee, Gwan-Su ; Kim, U-Seung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 3, 1997, Pages 405~413
DOI : 10.22634/KSME-B.19220.127.116.115
A thermal optimization of the chip arrangement in the PCB channel oriented vertically and cooled by natural convection has been studied. The objective of this study is to find the chip arrangement that minimizes the maximum temperature of the entire PCB channel. SIMPLER algorithm is employed in the analysis, and the genetic algorithm is used for the optimization. The results show that the chip with a maximum volumetric heat generation rate has to be located at the bottom of the channel, and chips with relatively high heat generation rates should not be close to each other, and small chip should not be located between the large chips.
Numerical study on the characteristics of the flow through injector orifice by multi-block computations
Kim, Yeong-Mok ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 3, 1997, Pages 414~426
DOI : 10.22634/KSME-B.1918.104.22.1684
Numerical computations were conducted to characterize the three-dimensional laminar flow through an injector orifice having an inclined angle of 30 .deg.. For this study, the incompressible Navier-Stokes equations in generalized curvilinear coordinates, using a pseudocompressibility approach for continuity equation, were solved. The computations were performed using the finite difference implicit, approximately factored scheme of Beam and Warming and multi-block grids of complete continuity at block interfaces. The multi-block computations were validated for the steady state using direct comparison of multi-block solutions with equivalent single-block ones, including 2-D 180.deg. TAD and 3-D 90.deg. pipe bend. The comparisons between the numerical solutions and the flow field measurements for a tube with sudden contraction were presented in this work for solution validation. Computational results showed the nature of complex flow fields within the inclined injector orifice, including strong pressure-driven secondary flows in the cross stream induced by the effect of streamline curvature. In addition, asymmetric secondary flows were induced in the Reynolds number range above assumed laminar flow regime considered. However, turbulence calculations and grid dependency studies are needed for more accurate computations.
Correlation of the Wall Skin-Friction and Streamwise Velocity Fluctuations in a Turbulent Boundary Layer(II)
Yang, Jun-Mo ; Yu, Jeong-Yeol ; Choe, Hae-Cheon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 3, 1997, Pages 427~435
DOI : 10.22634/KSME-B.1922.214.171.1247
Conditional sampling techniques are utilized to investigate the relation between the wall skin-friction and stream wise velocity fluctuations in a turbulent boundary layer. Conditionally averaged results using a peak detection and the VITA (variable-interval time-averaging) technique show that a high skin friction is associated with high frequency components of the wall skin-friction fluctuations. The conditionally averaged wall skin-friction fluctuations obtained by using the VITA technique have a positively-skewed characteristics compared with the conditionally averaged stream wise velocity fluctuations. It is confirmed that there exists a phase shift between the wall skin-friction and stream wise velocity fluctuations, which was also found from the long-time averaged space-time correlations. The amount of phase shift between the wall skin-friction and stream wise velocity fluctuations is the same as that from the long-time averaged space-time correlations and does not change despite the variation of the detection threshold.
Three-dimensional analysis of the thermophoretic particle deposition in the OVD process
Hong, Gi-Hyeok ; Gang, Sin-Hyeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 3, 1997, Pages 436~444
DOI : 10.22634/KSME-B.19126.96.36.1996
Three-dimensional conjugate heat transfer and particle deposition on a circular cylinder in the OVD process are numerically investigated. Flow and temperature fields are obtained by an iterative method, and thermophoretic particle deposition is simulated. Effects of the heat conduction in the cylinder, the rotation speed of the cylinder, and the traversing speed of torch on the deposition are studied. Effects of variable properties are also included. As the conductivity of the cylinder decreases, particle deposition rate and deposition efficiency greatly decrease due to the reduced temperature gradient. The rotation of the cylinder has no significant effect on the deposition due to the small diameter of the cylinder and low speed of rotation. Since the increase of the torch speed keeps the surface low temperature, the particle deposition increases with the traversing speed.
Numerical analysis of the continuous casting process in the presence of thermo-solutal convection
Jeong, Jae-Dong ; Yu, Ho-Seon ; Lee, Jun-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 3, 1997, Pages 445~456
DOI : 10.22634/KSME-B.19188.8.131.525
Continuous casting process is numerically analyzed using the continuum model in a non-orthogonal coordinate system. Flow damping in the mush is modeled by combining the viscosity dependence on liquid fraction in dilute mush and the permeability dependence on liquid fraction in concentrated mush. The effect of turbulence is indirectly considered by effective diffusivity determined elsewhere by experiment. The main objective is to investigate the effects of casting parameters such as casting speed and tundish superheat on the distribution of surface temperature, shell thickness, metallurgical length and centerline segregation. Some of the computed results are compared with available experiments, and reasonable agreements are obtained.
Numerical and experimental analysis of temperature distribution in TEFC induction motor
Yun, Myeong-Geun ; Go, Sang-Geun ; Han, Song-Yeop ; Lee, Yang-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 21, issue 3, 1997, Pages 457~472
DOI : 10.22634/KSME-B.19184.108.40.2067
We studied the temperature distribution and heat transfer characteristics of TEFC induction motor with thermal network program for more efficient design and better cooling performance of it. We knew the characteristics and the windage loss of outer cooling fan from fan test experiments. Frame axial and peripheral heat transfer coefficients and endwinding heat transfer coefficient were measured by various model experiments and then, compared with other experimental results. Frame was the main heat transfer surface, load-side and fan-side surface were not thermally symmetric from the heat flux distribution analysis. Steady and unsteady temperature distributions were measured by real motor experiments. From the results, we knew that rotor surface temperature was higher than coil temperature and the hottest spot in the coil was loadside endwinding outside surface. We compared the simulation results with those of real motor test and the two results showed a good agreement.