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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 26, Issue 12 - Dec 2002
Volume 26, Issue 11 - Nov 2002
Volume 26, Issue 10 - Oct 2002
Volume 26, Issue 9 - Sep 2002
Volume 26, Issue 8 - Aug 2002
Volume 26, Issue 7 - Jul 2002
Volume 26, Issue 6 - Jun 2002
Volume 26, Issue 5 - May 2002
Volume 26, Issue 4 - Apr 2002
Volume 26, Issue 3 - Mar 2002
Volume 26, Issue 2 - Feb 2002
Volume 26, Issue 1 - Jan 2002
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Propagation Characteristics of Pressure Pulse of Unsteady Flow in n Hydraulic Pipeline
Yu, Yeong-Tae ; Na, Gi-Dae ; Kim, Ji-Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 1~11
DOI : 10.3795/KSME-B.2002.26.1.001
Flow of fluid has been studied in various fields of fluid engineering. To hydraulic engineers, the unsteady flow such as pulsation and liquid hammering in pipes has been considered as a serious trouble. So we are supposed to approach the formalized mathematical model by using more exact momentum equation for fluid transmission lines. Most of recent studies fur pipe line have been studied without considerations of variation of viscosity and temperature, which are the main factors of pressure loss causing the friction of fluid inside pipe line. Frequency response experiments are carried out with use of a rotary sinusoidal flow generator to investigate wave equation take into account viscosity and temperature. But we observed that measured value of gains are reduced as temperature increased. And it was respectively observed that the measured value of gains are reduced and line width of gain is broadened out, when temperature was high in the same condition. As we confessed, pressure loss and phase delay are closely related with the length, diameter and temperature of pipe line. In addition, they are the most important factors, when we decide the momentum energy of working fluid.
The Influence of Liquid-Vapor Interactions on Friction in Micro-Channel Flow with Trapezoidal Grooves
Seo, Jeong-Se ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 12~17
DOI : 10.3795/KSME-B.2002.26.1.012
Abstract The flow of liquid and vapor is investigated in trapezoidal grooves. The effect of variable shear stress along the interface of the liquid and vapor is studied for both co-current and counter-current flows. Velocity contours and results for the friction are obtained for both trapezoidal grooves. An approximate relation that was previously utilized for the friction for the liquid was modified to obtain accurate agreement with the results for trapezoidal grooves.
Statistical Characteristics of Fractal Dimension in Turbulent Prefixed Flame
Lee, Dae-Hun ; Gwon, Se-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 18~26
DOI : 10.3795/KSME-B.2002.26.1.018
With the introduction of Fractal notation, various fields of engineering adopted fractal notation to express characteristics of geometry involved and one of the most frequently applied areas was turbulence. With research on turbulence regarding the surface as fractal geometry, attempts to analyze turbulent premised flame as fractal geometry also attracted attention as a tool for modeling, for the flame surface can be viewed as fractal geometry. Experiments focused on disclosure of flame characteristics by measuring fractal parameters were done by researchers. But robust principle or theory can't be extracted. Only reported modeling efforts using fractal dimension is flame speed model by Gouldin. This model gives good predictions of flame speed in unstrained case but not in highly strained flame condition. In this research, approaches regarding fractal dimension of flame as one representative value is pointed out as a reason for the absence of robust model. And as an extort to establish robust modeling, Presents methods treating fractal dimension as statistical variable. From this approach flame characteristics reported by experiments such as Da effect on flame structure can be seen quantitatively and shows possibility of flame modeling using fractal parameters with statistical method. From this result more quantitative model can be derived.
The Effect of Reynolds Number on the Three-Dimensional Flow Measurements with a Two-Stage Cone-Type Five-Hole Probe in a Non-Nulling Mode
Lee, Sang-U ; Jeon, Sang-Bae ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 27~38
DOI : 10.3795/KSME-B.2002.26.1.027
The effects of Reynolds number on the non-nulling calibrations of a cone-type ave-type probe in low-speed flows have been investigated at Reynolds numbers of 2.04
. The calibration is conducted at the pitch and yaw angles in ranges between -35 degrees and 35 degrees with an angle interval of 5 degrees. In addition to the calibration coefficients, reduced pitch and yaw angles, static and total pressures, and velocity magnitude are obtained through a typical non-nulling reduction procedure. The result shows that each calibration coefficient, in general, is a function of both the pitch and yaw angles, so that the pre-existing calibration data in a nulling mode are not enough in accounting far the full non-nulling calibration characteristics. Due to interference of the probe stem, the calibration coefficient are more sensitive to Reynolds number at positive pitch angles than at negative ones. The calibration data reduced in this study may serve as a guide line in the estimation of uncertainty intervals resulted from the Reynolds number effects at low Reynolds numbers.
Pulsatile Flow in the Artery with Stenosis
Son, Jeong-Rak ; Ju, Sang-U ; Seo, Sang-Ho ; Sim, Eun-Bo ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 39~44
DOI : 10.3795/KSME-B.2002.26.1.039
The arterial stenosis related to the intimal thickening of the arterial wall is the main cause of many diseases in human cardiovascular system. Hemodynamic behavior of the blood flow is influenced by the presence of the arterial stenosis. In this study, effects of the pulsatile flow, caused by the periodic motion of the heart, on the blood flow and its interaction with the arterial stenosis are analyzed by the FEM-based computational fluid dynamics. As a result, it was found that the characteristics of the pulsatile flow in the artery with stenosis are quite different from those of the steady flow. And, the pulsatile flow condition affects the wall shear stress, which is one of the most important physiological parameters in the hemodynamics.
A Study on the Nonlinear Motion of a Vertical Liquid Jet
Seok, Ji-Gwon ; Jeong, Hwan-Mun ; Mun, Su-Yeon ; Lee, Chung-Won ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 45~54
DOI : 10.3795/KSME-B.2002.26.1.045
The breakup phenomena of a vertical laminar jet issuing from capillary tubes in a quiescent ambient air are investigated using a forced vibration analysis of the surface wave. Using a linear approach to the transient jet velocity, an approximate solution fur the longitudinal motion of a vertical liquid jet is theoretically derived, thus performing an instability analysis by a vibration method. The damping term of this equation is nonlinear as it depends on dimensionless parameters, a Weber number, and an Ohnesorge number. The instability condition is determined based on whether the coefficient of the damping term is less than zero or not. Uniform drop formation is dependent on the vibration frequency fur the forced vibration case.
Performance Analysis and Preliminary Design for the Turbo-Shaft Engine of the Multi-Purpose Helicopter
Seo, Jeong-Won ; Yun, Geon-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 55~65
DOI : 10.3795/KSME-B.2002.26.1.055
In this study, the procedures for the preliminary design of the turbo-shaft engine for the light multi-purpose helicopter are established. The engine specifications are determined through the performance analysis on the on-design and off-design conditions by the use of simulation program. In addition, the effect of humidity on the engine performance is examined by considering the change of the gas properties and characteristic maps due to moisture contents. The calculation results show that the engine power is reduced by the existence of moisture in working fluid.
Performance Analysis of a Thermally Asymmetric Triangular Fin
Gang, Hyeong-Seok ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 66~73
DOI : 10.3795/KSME-B.2002.26.1.066
Fin effectiveness and efficiency of a thermally asymmetric triangular fin are represented as a function of the ratio of fin lower surface Biot number to upper surface Biot number and the non-dimensional fin length. For this analysis, two dimensional separation of variables method is used. When fin effectiveness is 2 and efficiency is 90%, the relationship between the non-dimensional fin length and the ratio of fin lower stir(ace Biot number to upper surface Biot number is shown. The relationship between the non-dimensional fin length and the upper surface Biot number for the same condition is also presented.
Design and Development of Micro Combustor (I) - Combustion Characteristics in Scale-Downed Combustor -
Lee, Dae-Hun ; Choe, Gwon-Hyeong ; Gwon, Se-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 74~81
DOI : 10.3795/KSME-B.2002.26.1.074
Combustion phenomena in a sub-millimeter scale combustor have been investigated. To evaluate scale effect on flame propagation characteristics, a cylindrical combustion chamber with variable depth was built in-house. The combustor was charged with premixed gas of hydrogen and air and ignited electronically. A piezo electric pressure transducer recorded transient pressure after the ignition. Measurements were made at different test conditions specified with chamber depth and initial pressure as parameters. Visual observation was made through a quartz glass window on top side of the combustion chamber using high speed digital video camera. From the pressure data, available work was estimated and compared with energy input required for stable ignition. The preliminary results suggested that the net thermal energy release is sufficient to generate power and enables a combustor of the size in the present study to be used as the energy source of a micro power devices .
The Experimental Study of the Interaction Between the Flow rind Temperature Field and a Boundary Layer Due to a Variety of tole Height of a Vortex Generator
Gwon, Su-In ; Yang, Jang-Sik ; Lee, Gi-Baek ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 82~93
DOI : 10.3795/KSME-B.2002.26.1.082
The effects of the interaction between the flow and temperature field and a boundary layer due to a variety of the height of a vortex generator are experimentally investigated. The test facility consists of a boundary-layer wind tunnel with the vortex generator protruding from the bottom surface. In order to control the strength of the longitudinal vortices, the angle of attack and the spacing distance of the vortex generator are 20 degree and 40 mm, respectively. The height of the vortex generator (H) is 15 mm, 20 mm and 30 mm and the cord length of it is 50 mm. Three-component mean velocity measurements are made using a 5-hole probe system and the surface temperature distribution is measured by the hue capturing method using thermochromatic liquid crystals. By using the method mentioned above, the following conclusions are obtained from the present experiment. The boundary layer is thinned in the downwash region where the strong downflow and the lateral outflow of the boundary layer fluid occur and thickened in the upwash re,3ion where the longitudinal vortex sweeps low momentum fluid away from the bottom surface. In case that the height of the vortex generator increases, the averaged circulation and the maximum vorticity of the vortex pair decrease. The contours of the non-dimensional temperature show the similar trends fur all the cases (H=15 mm, 20 mm and 30 mm). The peak augmentation of the distribution of the local non-dimensional temperature occurs in the downwash region near the point of minimum boundary-layer thickness.
The Effects of Periodic Fuel Supply on the Flame Stability and Soot Formation
Lee, Sang-Hyeop ; Jeon, Dae-Hyeon ; Lee, Byeong-Jun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 94~100
DOI : 10.3795/KSME-B.2002.26.1.094
The effects of periodic fuel supply on the nonpremixed flame stability and soot formation were experimentally studied. A solenoid valve was used to control the period of fuel supply. The laser induced incandescence technique was used to visualize cool: volume fraction profile. The flame base shape was changed significantly by the fuel supply period and partially by the fuel flowrates. The portion of bluish flame near the flame base became larger as the period increased. When the period was long, two flames coexisted within one period. It seemed that the characteristic of flame stability were repeated with 4.68m change of fuel supply line length. The soot mass measurements and soot volume fraction measurements revealed that the maximum suppression of soot by the perioic fuel supply was approximately 75% , which occurred when the occurred when the fuel supply period was relatively long.
The Effects of Impingement Hole Arrangements on Heat Transfer of an Impingement/Effusion Cooling System
Choe, Jong-Hyeon ; Lee, Dong-Ho ; Jo, Hyeong-Hui ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 101~109
DOI : 10.3795/KSME-B.2002.26.1.101
Two perforated plates are used to investigate local heat/mass transfer characteristics in an impingement/effusion cooling system. A naphthalene sublimation method is conducted to determine the local heat/mass transfer coefficients on the upward facing surface of the effusion plate. Two plates are placed in parallel position with gap distances of 1, 2, 4 and 6 times of effusion hole diameter. The effects of hole arrangements of the plates are studied fur staggered, square, and hexagonal arrays. The experiments are conducted at Reynolds number of 10,000 based on the effusion hole diameter. The results show that the smaller hole size in the staggered array has the higher transfer coefficients on the stagnation region due to the formation of higher momentum flows through the impingement holes. In the square array, heat/mass transfer on the target plate is more uniform as the number of impingement holes increases. High and uniform heat/mass transfer coefficients are obtained for the hexagonal array.
Estimation of Pollutants Exhausted :From vehicles for Tunnel ventilation Control
Hong, Dae-Hui ; Kim, U-Dong ; Kim, Tae-Hyeong ; Min, Won ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 110~115
DOI : 10.3795/KSME-B.2002.26.1.110
The tunnels built in recent years are equipped with traffic counters and pollution sensors (mostly, CO and Vl sensors). Utilizing these built-in sensors, it is possible to develop an algorithm to estimate the amount of pollutants exhausted from the each class of cars passing through the tunnel. These estimated data can be effectively utilized not only for ventilation control but also for designing ventilation facilities. The diffusion of pollutants in a tunnel can be described with one-dimensional diffusion-convection equation. This equation is approximated with interpolation functions and weighted residual method converting to adequate form for standard state estimate algorithms. With this converted equations, a least square optimization based algorithm is developed, whose outputs are the estimated amounts of pollutants emitted from each class of cars. In order to verify the feasibility of the developed algorithms, simulations are performed with the real data acquisitioned from the Tunnae tunnel located in Young-Dong highway in Korea.
Effects of Tube Inclination Angle on Nucleate Pool Boiling Heat Transfer
Gang, Myeong-Gi ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 116~124
DOI : 10.3795/KSME-B.2002.26.1.116
An experimental parametric study of a tubular heat exchanger has been carried out far the saturated water at atmospheric pressure to determine effects of tube inclination on pool boiling heat transfer. For the analysis, seven inclination angles(0°, 15°, 30°, 45°, 60°, 75°, and 90°) and two tube diameters(12.7 and 19.1 mm) were tested. According to the results, inclination angles result in very much change on pool boiling heat transfer. As the inclination angle is around horizontal or vertical, maximum or minimum heat transfer is expected, respectively. For the same wall superheat(about 5.5K) the ratio between two heat fluxes fur
=15° and 75° has the value of more than five when the tube diameter is 12.7 mm and heat flux is increasing.
Characteristics of Turbulent Nonpremixed Jet Flame in Cross Air Flow
Lee, Gi-Man ; Park, Jeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 125~132
DOI : 10.3795/KSME-B.2002.26.1.125
An experimental study on the characteristics of stability of propane turbulent nonpremixed jet flames discharged normal to air free-streams with uniform velocity profile is conducted. Experimental observations are focused on the flame shape, the stability considering two kinds of flame, lift-off distance, and the flame length according to velocity ratio. In order to investigate the mixing structure of the flame base at the lower limit, we employ the RMS technique and measure the species concentration by a gas chromatography. In the results of the stability curve and lifted flame, it is fecund that the dependency of nozzle diameter is closely related to the large-scale vortical structure representing counter-rotating vortices pair. Also, the detailed discussion on the phenomenon of blowout due to this large vortical motion, is provided.
A Large-scale Structural Mixing Model applied to Blowout of Turbulent Nonpremixed Jet Flames in a Cross Jet Flow
Lee, Gi-Man ; Park, Jeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 133~140
DOI : 10.3795/KSME-B.2002.26.1.133
This article presents an application of a large-scale structural mixing model(Broadwell et at. 1984) to the blowout of turbulent reacting cross flow jets. Experimental observations, therefore, aim to identify the existence of large-scale vortical structure exerting an important effect upon the flame stabilization. In the analysis of common stability curve, it is seen that the phenomenon of blowout are only related to the mixing time scale of the two flows. The most notable observation is that the blowout distance is traced at a fixed positions according to the velocity ratio at all times. Measurements of the lower blowout limits in the liftable flame are qualitatively in agreement with the blowout parameter
, proposed by Broadwell et al. Good agrement between the results calculated by a modified blowout parameter
'and the present experimental results confirms the important effect of large-scale structure in the stabilization feature of blowout.
Prediction of Jet Impingement Heat Transfer on a Cylindrical Pedestal
Park, Tae-Seon ; Seong, Hyeong-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 141~149
DOI : 10.3795/KSME-B.2002.26.1.141
A numerical simulation is performed for the cooling heat transfer of a heated cylindrical pedestal by an axisymmetric jet impingement. Based on the k-
/ model of Park et at., the linear and nonlinear stress-strain relations are extended. The Reynolds number based on the jet diameter(D) is fixed at Re
D/ = 23000. The local heat transfer coefficients are compared with available experimental data. The predictions by k-
/ model are in good agreement with the experiments, whereas the standard 7- f model does not properly resolve the flow structures.
Heat/Mass Transfer Augmentation in a Square Duct . Roughened with Angled Discrete Ribs Having Narrow Gaps
U, Seong-Je ; Lee, Se-Yeong ; Choe, Cheong ; Jo, Hyeong-Hui ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 150~158
DOI : 10.3795/KSME-B.2002.26.1.150
Local heat/mass transfer and friction loss in a square duct roughened with various types of continuous and discrete rib turbulators are investigated. The combined effects of the gap flows of the discrete ribs and the secondary flows are examined for the purpose of the reduction of thermally weak regions and the promotion of the uniformity of heat/mass transfer distributions as well as the ;augmentation of average heat/mass transfer. The rib-to-rib pitch to the rib height ratio (p/e) of 8 and the rib angles of 90° and 60° are selected with e/D
h/=0.08. The vortical structure of the secondary flows induced by the parallel angled arrays are quite distinct from that induced by the cross angled arrays. This distinction influences on heat/mass transfer and friction loss in all the tested cases. The gap flows of the discrete ribs reduce the strength of the secondary flows but promote local turbulence and flow mixing. Consequently, the angled discrete ribs with the small gaps provide a more uniform heat/mass transfer distribution sustaining high average heat/mass transfer.
A Numerical Study on the Flow Development around a Rotating Square-Sectioned U-Bend (I) - Laminar Flow -
Lee, Gong-Hui ; Baek, Je-Hyeon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 26, issue 1, 2002, Pages 159~169
DOI : 10.3795/KSME-B.2002.26.1.159
The present study investigates in detail the combined effects of the Coriolis and centrifugal farce on the development of laminar flows in a square-sectioned U-bend rotating about an axis parallel to the center of bend curvature. When a viscous fluid flows through a rotating curved region, two types of secondary flow occur. One is caused by the Coriolis force due to the rotation of U-bend and the other by the centrifugal farce due to the curvature of U-bend. When the values of Rossby number and curvature ratio are large, the flow field in a rotating U-bend can be represented by two dimensionless parameters ; the Dean number K
LC/=Re/√λ and a body ratio F=λ/Po. For positive rotation, where the rotation is in the same direction as that of the main flow, both the Coriolis force and the centrifugal force act radially outwards, the directions of the two secondary flows are the same. Therefore, the flow structure is qualitatively similar to that observed in a stationary curved duct with a larger f7c. On the other hand, in case of negative rotation, where two farces act in opposite direction, more complex flow fields can be observed depending on the relative magnitudes of the forces.