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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 24, Issue 12 - Dec 2000
Volume 24, Issue 11 - Nov 2000
Volume 24, Issue 10 - Oct 2000
Volume 24, Issue 9 - Sep 2000
Volume 24, Issue 8 - Aug 2000
Volume 24, Issue 7 - Jul 2000
Volume 24, Issue 6 - Jun 2000
Volume 24, Issue 5 - May 2000
Volume 24, Issue 4 - Apr 2000
Volume 24, Issue 3 - Mar 2000
Volume 24, Issue 2 - Feb 2000
Volume 24, Issue 1 - Jan 2000
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A New VOF-based Numerical Scheme for the Simulation of Fluid Flow with Free Surface(I)-New Free Surface Tracking Algorithm and Its Verification-
Kim, Min-Su ; Sin, Su-Ho ; Lee, U-Il ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1555~1569
DOI : 10.22634/KSME-B.2000.24.12.1555
Numerical simulation of fluid flow with moving free surface has been carried out. For the free surface flow, a VOF(Volume of Fluid)-based algorithm utilizing a fixed grid system has been investigated. In order to reduce numerical smearing at the free surface represented on a fixed grid system, a new free surface tracking algorithm based on the donor-acceptor scheme has been presented. Novel features of the proposed algorithm are characterized as two numerical tools; the orientation vector to represent the free surface orientation in each cell and the baby-cell to determine the fluid volume flux at each cell boundary. The proposed algorithm can be easily implemented in any irregular non-uniform grid systems that are usual in finite element method (FEM). Moreover, the proposed algorithm can be extended and applied to the 3-D free surface flow problem without additional efforts. For computation of unsteady incompressible flow, a finite element approximation based on the explicit fractional step method has been adopted. In addition, the SUPG(streamline upwind/Petrov-Galerkin) method has been implemented to deal with convection dominated flows. Combination of the proposed free surface tracking scheme and explicit fractional step formulation resulted in an efficient solution algorithm. Validity of the present solution algorithm was demonstrated from its application to the broken dam and the solitary wave propagation problems.
A New VOF-based Numerical Scheme for the Simulation of Fluid Flow with Free Surface(II)-New Free Surface Tracking Algorithm and Its Verification-
Kim, Min-Su ; Park, Jong-Seon ; Lee, U-Il ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1570~1579
DOI : 10.22634/KSME-B.2000.24.12.1570
Finite element analysis of fluid flow with moving free surface has been carried out in two and tree dimensions. The new VOF-based numerical algorithm that has been proposed by the present authors was applied to several 2-D and 3-D free surface flow problems. The proposed free surface tracking scheme is based on two numerical tools that have been newly introduced by the present authots; the orientation vector to represent the free surface orientation in each cell and the baby-cell to determine the fluid volume flux at each cell boundary. The proposed numerical algorithm has been applied to 2-D and 3-D cavity filling and sloshing problems, which demonstrated versatility and effectiveness of the new free surface tracking scheme as well as the overall solution procedure. The proposed numerical algorithm resolved successfully the interacting free surface with each other. The simulated results demonstrated the applicability of proposed numerical algorithm to the practical problems of large free surface motion. Also, it has been demonstrated that the proposed free surface tracking scheme can be easily implemented in any irregular non-uniform grid systems and can be extended to the 3-D free surface flow problem without additional efforts.
Planar Imaging of Temperature and Concentration of a Laminar Nonpremixed
flame Using a Tunable KrF Excimer Laser
Kim, Gun-Hong ; Jin, Seong-Ho ; Kim, Yong-Mo ; Park, Gyeong-Seok ; Kim, Se-Won ; Kim, Gyeong-Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1580~1587
DOI : 10.22634/KSME-B.2000.24.12.1580
Rayleigh scattering and laser induced predissociative fluorescence are employed for capturing two-dimensional images of temperature and species concentration in a laminar nonpremixed flame of a diluted hydrogen jet. Rayleigh scattering cross-sections are experimentally obtained ar 248nm. Dispersed LIPF spectra of OH and O
are also measured in a flame in order to confirm the excitation of single vibronic state of OH and O
.OH and O
are excited on the P
(8) line of the A
band and R(17) line of the Schumann-Runge band B
, respectively. Fluorescence spectra of OH and Hot O
are captured and two-dimensional images of the hydrogen flame field are successfully visualized.
Planar Imaging of Temperature and Concentration of a Laminar Nonpremixed H²/N² Flame Using a Tunable KrF Excimer Laser
Kim, Gun Hong ; Jin, Seong Ho ; Kim, Yong Mo ; Park, Gyeong Seok ; Kim, Se Won ; Kim, Gyeong Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1582~1582
DOI : 10.22634/KSME-B.2000.24.12.1582
Rayleigh scattering and laser induced predissociative fluorescence are employed for capturing two-dimensional images of temperature and species concentration in a laminar nonpremixed flame of a diluted hydrogen jet. Rayleigh scattering cross-sections are experimentally obtained at 248nm. Dispersed LIPF spectra of OH and O₂ are also measured in a flame in order to confirm the excitation of single vibronic state of OH and O₂are excited on the P₁(8) line of the A ²∑+ (v＇=3) - X ²∏(v˝=0) band and R(17) line of the Schumann-Runge band B ³∑u- (v＇=0) - X ³∑g-∏(v˝=6), respectively. Fluorescence spectra of OH and Hot O₂ are captured and two-dimensional images of the hydrogen flame field are successfully visualized.
A Study on the Characteristics of Natural Convection in a Partially Opened Enclosure with a Heat Source
Sim, Dong-Sik ; Gang, Bo-Seon ; Cha, Dong-Jin ; Ju, Won-Jong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1588~1595
DOI : 10.22634/KSME-B.2000.24.12.1588
Natural convection heat transfer in an enclosure with an opening in the right veritcal wall and a heat source at the bottom surface is investigated using a holographic interferometric technique. The effects of the opening length, divider length attached to the top wall, and heater temperature on the temperature distribution are examined. The opening length as well as the divider length greatly affects the degree of inflow and outflow of air. In the case of small opening length, the opening doesnt affect much the upward warm air flow resulting in the symmetric temperature distribution .The upward flow in hindered by the divider resulting in the decrease of heat transfer from the heater region to the upper region. The longest divider shows the highest temperature in the lower region of enclosure. In the case of large opening length, the inward cold flow moves the upward flow to the left direction. Among the cases of different divider length, the case of H(sub)d=0.25H shows the highest temperature in the lower region of enclosure.
Numerical Design of Auto-Catalyst Substrate for Improved Conversion Performance Using Radially Variable Cell Density
Jeong, Su-Jin ; Kim, U-Seung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1596~1607
DOI : 10.22634/KSME-B.2000.24.12.1596
The optimal design of auto-catalyst needs a good compromise between the pressure drop and flow uniformity in the substrate. One of the effective methods to achieve this goal is to use the concept of radially variable cell density. But this method has not been examined its usefulness in terms of chemical behavior and conversion performance. In this work, two-dimensional performance prediction of catalyst coupled with turbulent reacting flow simulation has been used to evaluated the benefits of this method n the flow uniformity and conversion efficiency. The results showed that two cell combination of 93cpsc and 62 cpsc was the most effective for improved pressure drop and conversion efficiency due to balanced space velocity and efficient usage of geometric surface area of channels. It was also found that large temperature difference between the bricks in case that the edge of the frontal face of brick has too much lower cell density(less than 67% of cell density of the center of the brick). This study has also demonstrated that the present computational results show the better prediction accuracy in terms of CO, HC and NO conversion efficiencies compared to those of conventional 1-D adiabatic model by comparison with experimental results.
A Study on the Flame Propagation Characteristics for LPG and Gasoline fuels by Using Laser Deflection Method
Lee, Gi-Hyeong ; Lee, Chang-Sik ; Gang, Geon-Yong ; Gang, U ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1608~1614
DOI : 10.22634/KSME-B.2000.24.12.1608
For the purpose of obtaining fundamental data which is needed to develope combustion system of LPG engine, we made constant volume chamber and analyzed flame propagation characteristics under different intial temperature, initial pressure and equivalence ratio which affect combustion of LPG. We investigated flame propagation speed of each fuel using laser deflection method and compared with the investigated flame propagation speed of each fuel using laser deflection method and compared with the results of image processing of flame. As a result, the maximum flame propagation speed was found at equivalence ratio 1.0 and 1.1 for LPG and gasoline, respectively. In the lean region, we can see that flame propagation speed of LPG surpasses that of gasoline. On the contrary, flame propagation speed of gasoline surpasses LPG in the rich region. As initial temperature and initial pressure were higher, flame propagation speed was faster. And, as equivalence ratio was larger and initial temperature was higher, combustion duration was shorter and maximum combustion pressure was higher.
Numerical Analyses on Wall-Attaching Offset Jet with Algebraic Reynolds Stress Model
Seo, Ho-Taek ; Bu, Jeong-Suk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1615~1624
DOI : 10.22634/KSME-B.2000.24.12.1615
Algebraic Reynolds Stree (ARS) model is applied in order to analyze the turbulent flow of wall-attaching offset jet and to evaluate the predictability of model. The applied numerical schemes are the upwind scheme and the skew-upwind scheme. The numerical results show a good prediction in the first order calculations(i.e., reattachment length, mean velocity, pressure), however, slight deviations in the second order(i.e., kinetic energy and turbulence intensity). Comparing with the previous results using the k-
model, the ARS model predicts better than the standard k-
model, however, slightly worse than the k-
model including the streamline curvature modification. Additionallay this study can reconfirm that the skew-upwind scheme has approximately 25% improved predictability than the upwind scheme.
Development of Performance Analysis Methodology for Nuclear Power Plant Turbine Cycle Using Validation Model of Performance Measurements
Kim, Seong-Geun ; Choe, Gwang-Hui ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1625~1634
DOI : 10.22634/KSME-B.2000.24.12.1625
Verification of measurements is required for precise evaluation of turbine cycle performance in nuclear power plant. We assumed that initial acceptance data and design data of the plant could provide correlation information between performance data. The data can be used as sample sets for the correct estimation model of measurement value. The modeling was done practically by using regression model based on plant design data, plant acceptance data and verified plant performance data of domestic nuclear power plant. We can construct more robust performance analysis system for an operation nuclear power plant with this validation scheme.
On the Thermal Boundary Conditions at the Interface Between the Porous Medium and the Impermeable Wall
Kim, Deok-Jong ; Kim, Seong-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1635~1643
DOI : 10.22634/KSME-B.2000.24.12.1635
The present work investigates a heat transfer phenomenon at the interface between a porous medium and an impermeable wall. In an effort to appropriately describe the heat transfer phenomenon at the interface, the heat transfer at the interface between the microchannel heat sink, which is an ideally organized porous medium, and the finite-thickness substrate is examined. From the examination, it is clarified that the he heat flux distribution at the interface is not uniform for the impermeable wall with finite thickness. On the other hand, the first approach, based on the energy balance for the representative elementary volume in the porous medium, is physically reason able. When the first approach is applied to the thermal boundary condition, and additional boundary condition based on the local thermal equilibrium assumption at the interface is used. This additional boundary condition is applicable except for the very th in impermeable wall. Hence, for practical situations, the first approach in combination with the local thermal equilibrium assumption at the interface is suggested as an appropriate thermal boundary condition. In order to confirm our suggestion, convective flows both in a microchannel heat sink and in a sintered porous channel subject to a constant heat flux condition are analyzed. The analytically obtained thermal resistance of the microchannel heat sink and the numerically obtained overall Nusselt number for the sintered porous channel are shown to be in close agreement with available experimental results when our suggestion for the thermal boundary conditions is applied.
Numerical Study of Laminar Flow in a Combustor with a Planar Fuel Jet
Eom, Jun-Seok ; Kim, Do-Hyeong ; Yang, Gyeong-Su ; Sin, Dong-Sin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1644~1651
DOI : 10.22634/KSME-B.2000.24.12.1644
In this study, the confined laminar flow and transport around a square cylinder with a planar fuel jet are numerically simulated. Both rear and front jets are considered, respectively. In each case, various ratios of the jet velocity to the fixed upstream velocity are taken into consideration. In case of the rear jet, the high mass-fraction region is formed along the streamlines from the jet exit, and the oscillation of the force on the square cylinder eventually disappears as the jet velocity is close to the upstream velocity. In case of the front jet, drag is significantly reduced when the jet velocity ratio is grater than 1. The results obtained exhibit flow and scalar-mixing charactered in a planar combustor.
A Visualization Study on the Effects of Ignition Systems on the Flame Propagation in a Constant Volume Combustion Chamber
Song, Jeong-Hun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1652~1661
DOI : 10.22634/KSME-B.2000.24.12.1652
A visualization study using the schlieren method is adopted in an optically-accessible, cylindrical constant volume combustion chamber to identify the mechanism of ignition energy and ignition system interaction in spark ignited, lean gasoline-air mixture. In order to research the effects of ignition system on flame propagation, two kinds of ignition system are designed, and several kinds of spark plugs are tested and evaluated. To control the discharge energy, the dwell time is varied. The initial flame development is quantified in terms of 2-D images which provides information about the projected flame area and development velocity as a function of ignition system and discharge energy. The results show that high ignition energy and extended spark plug gap can shorten the combustion duration in lean mixtures. The material, diameter and configuration of electrodes the flame development by changing the transfer efficiency from electrical energy to chemical energy and discharge energy. However these factors do not affect of flame development as much a ignition energy or extended gap does.
Characteristics of Premixed Flames in a Double Concentric Burner
Gwon, Seong-Jun ; Cha, Min-Seok ; Choe, Man-Su ; Jeong, Seok-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1662~1669
DOI : 10.22634/KSME-B.2000.24.12.1662
Various flame types are observed in a double concentric burner by varying equivalence ratio and flow rates in each tube. Observed flame types include bunsen-type flame, ring-shaped flame, outer lifted flame, inner lifted flame, and oscillatory lifted flame, The doman of existence of various flames is mapped with equivalence ratio and annular jet velocity. Each flame is investigated through direct photography and OH PLIF. As central air velocity increase, the blowout region is diminished and lifted oscillating flames are observed. Inner lifted flames are observed from bunsen flames or rich shaped flames by increasing central air velocity. For inner lifted flames, annular jet velocity, at flame liftoff decreases with increasing central air jet velocity. Axial velocity profile and temperature fie이 using LDV and CRS, respectively, for a typical inner lifted flame are also measured through which the role of tribrachial flame for stabilization in emphasized.
Study on the Jet Impingement Heat Transfer Characteristics at Protruding heated Blocks
Jeong, In-Gi ; Park, Si-U ; Park, Su-Cheol ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1670~1677
DOI : 10.22634/KSME-B.2000.24.12.1670
An experimental investigation on heat transfer characteristics of two-dimensional heated blocks using a confined impinging slot jet has been performed. The effect of jet Reynolds number(Re=3900, 5800, 9700), streamwise block spacing(p/w=0.5, 1, 1.5) and dimensionless nozzle to block distance(H/B=1, 2, 4, 6) have been examined with five isothermally heated blocks. With the measurement of jet mean velocity and turbulence intensity distributions at nozzle exit, initially turbulent regimes, are classified. To clarify local heat transfer characteristics, naphthalene sublimation technique as used. The maximum Nusselt number at the stagnation point for the jet Reynolds number is occurred at H/B=4. Besides, the local and a average heat transfer of heated blocks increase with decreasing streamwise block spacing and increasing jet Reynolds number.
An Alternative Use of the Heat Transfer Coefficient in Terms of the Gradient Thickness
Kim, Chan-Jung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1678~1682
DOI : 10.22634/KSME-B.2000.24.12.1678
In this article, the concept of gradient thickness is further extended to characterize the gradient behavior of the thermal and momentum boundary layer near a solid surface. The gradient thickness can replace the use of the conventional of the Nusselt and Reynolds numbers in terms of the gradient thickness provides a much easier grasp of the physical and practical meaning of the processes involved. Although there is no urgent need to discard the concept of the conventional convective heat transfer coefficient, the concept of the gradient thickness is believed to serve an efficient tool in helping students understand physics.
Study on the Similarity of Laminar Flows between in Orthogonally Rotating Square Duct and Stationary Curved Squared Duct
Lee, Gong-Hui ; Baek, Je-Hyeon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 24, issue 12, 2000, Pages 1683~1691
DOI : 10.22634/KSME-B.2000.24.12.1683
In this study, it is numerically revealed that the secondary flow due to the Coriolls force in a straight duct rotating about an axis perpendicular to that of the duct is analogous to that caused by the centrifugal force in a stationary curved duct. Dimensionless parameters
and Rossby number in a rotating straight duct were used as a set corresponding to Dean number and curvature ratio in a stationary curved duct. When the value of Rossby number and curvature ratio is large, it is shown that the flow field satisfies the `asymptotic invariance property`, that is, there are strong quantitative similarities between the two flows such as friction factors, flow patterns, and maximum axial velocity magnitudes for the same values of
and Dean number.