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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
Journal Basic Information
Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 22, Issue 7 - Jul 1998
Volume 22, Issue 6 - Jun 1998
Volume 22, Issue 5 - May 1998
Volume 22, Issue 4 - Mar 1998
Volume 22, Issue 3 - Mar 1998
Volume 22, Issue 2 - Feb 1998
Volume 22, Issue 1 - Jan 1998
Volume 22, Issue 10 - 00 1998
Selecting the target year
A measurement of flow noise spectrum of an axisymmetric body
Park, Yeon-Gyu ; Kim, Yang-Han ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 725~733
DOI : 10.22634/KSME-B.19126.96.36.1995
The pressure fluctuation on the surface of a submerged body has been recognized as a dominant noise source. There have been many studies concerning the flow induced noise on a flat plate. However, the noise over an axisymmetric body has not been well reported. This paper addresses the way in which we have investigated the mechanism of noise generation due to an axisymmetric body. The associated experiments and signal processing methods are introduced. A 3-dimensional axisymmetric body whose length and diameter were 2 m and 10.4 cm, was prepared as a test specimen. The wall pressure on the surface of the body was measured in a large scale low noise wind tunnel at KIMM(Korea Institute of Machinery and Metals). To measure the wall pressure, we used two microphone arrays which were tangential and normal to the flow. Based on the measured signal, frequency-wavenumber spectrum which explains the structure of turbulence noise, was estimated. Tangential to the flow, there exists convective ridge at a relatively higher wavenumber region; this can cause spatial aliasing. To circumvent this problem, the cross spectrum was interpolated. The interpolation has been performed by unwrapping the phase and smoothing the cross spectrum. The phase unwrapping was done based on the Corcos model; the phase of cross spectrum decreases linearly with the distance between microphones. Aforementioned signal processings are possible by employing the experimental results that the estimated wavenumber spectrum quite resembles the Corcos model. We try to modify the Corcos model which is applicable to the flat plate, by altering the magnitude of cross spectrum to fit the experimental data more accurately. We proposed that this wavenumber spectrum model is suitable for the 3-dimensional axisymmetric body. Normal to the flow, there exists a little correlation between signals of different microphones. The circumferential wavenumber spectrum contains uniform power along the wavenumbers.
Numerical study on the transient operation characteristics of the heat pipe cooling system with the multiple uniform heating components for broadband digital cross-connect system
No, Hong-Gu ; Lee, Jae-Heon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 734~749
DOI : 10.22634/KSME-B.19188.8.131.524
A numerical study t predict the characteristics on transient operation of the heat pipe cooling system with multiple heaters for electronic system has been performed. The heat pipe cooling system of 45 cm length and 16 mm diameter was composed of evaporator section with four heaters which simulate electronic components, insulated transport section, and condenser section with a conductor which was cooled under the constant heat flux boundary condition. Two test cases were investigated in present study; Case 1 indicated that the 1st and 2nd heaters among four heaters were heated off, while the 3rd and the 4th heaters were heated on. Case 2 was the inverse situation switched from heating locations of Case 1. Case 3 indicated that the 1st and 4th heaters among four heaters were heated off, while the 2nd and 3rd heaters were heated on. The results showed that the transient time to reach the steady state is shorter for Case 1 than for Case 2. Especially, the maximum temperature among the heaters which simulate electronic components during switching operation is relatively small compared to the maximum allowable operating temperature in electronic system. It is concluded that the heat pipe cooling system in present study operate with the good thermal reliability even for sudden switching situation of the heaters.
R-113 condensation on vertically finned plate
Kim, Nae-Hyeon ; Jo, Jin-Pyo ; Kim, Jeong-O ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 750~756
DOI : 10.22634/KSME-B.19184.108.40.2060
In this study, condensation tests were conducted on a vertically finned plate (fin height 1 mm, fin thickness 1 mm, fin spacing 1 mm) using R-113. Results showed that fins enhanced the condensation on a vertical plain surface as much as four times. Comparison with theoretical models revealed that the effect off surface tension should be included in the model. The effect of interruption plates was also investigated. The plates were not effective in enhancing the finned plate condensation. The reason may be attributed to the already thinned condensate film on the finned surface.
정익과 동익의 상호작용에 의한 비정상 천이 경계층 유동의 수치해석에 관한 연구 1
Gang, Dong-Jin ; Lakshminarayana, Budugur ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 757~770
DOI : 10.22634/KSME-B.19220.127.116.117
A Navier-Stokes code with a low Reynolds number k-.epsilon. turbulence model was tested to investigate its predictability for the unsteady transitional boundary layer flow due to rotor-stator interaction. A preliminary calculation with three different numbers of time steps 300, 600, and 1000 for a rotor wake passing period was carried out to see the effects of time steps on the unsteady flow and pressure fields due to rotor-stator interaction. Numerical solutions showed that unsteady pressure was much more sensitive to the number of time steps and over 600 time steps should be used to get a numerical solution independent of the number of time steps for a rotor wake passing period. The original low Reynolds number k-.epsilon. turbulence model showed very poor prediction of the unsteady transitional boundary layer flow due to rotor-stator interaction. This was due to the excessive production of turbulent kinetic energy near the leading edge. A modification suggested by Launder was incorporated and the modified model captured well the wake induced transitional strip. Present solutions also showed improved prediction over previous Euler/boundary layer solution in terms of the onset of unsteady transition and its extent.
Numerical Prediction of Unsteady Transitional Boundary Layer Flows due to Rotor-Stator Interaction(II)-Characteristics of Unsteady Transitional Boundary Layer Flow-
Gang, Dong-Jin ; Lakshminarayana, Budugur ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 771~787
DOI : 10.22634/KSME-B.1918.104.22.1681
A Navier-Stokes code with a modified low Reynolds number k-.epsilon. turbulence model was used to study the unsteady transitional boundary layer flow due to rotor-stator interaction. The modification, proposed by Launder, to improve prediction of stagnation flows was incorporated to the low Reynolds number k-.epsilon. turbulence model by Fan-Lakshminarayana-Barnett. Numerical solution is shown to capture well the calmed laminar flow as well as the wake induced transitional strip due to rotor-stator interaction and shows improvement, in terms of onset of transition and its length, over previous Euler/boundary layer solution. The turbulent kinetic energy shows local maximum along the upstream rotor wake in the wake induced transitional strip and this characteristics is observed untill the end of transition. The wake induced strip also shown apparent even in the laminar sublayer as the upstream rotor wake penetrates inside the boundary layer.
Time accurate method for low speed compressible flows using dual time stepping and preconditioning procedure
Choe, Yun-Ho ; Gang, Sin-Hyeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 788~802
DOI : 10.22634/KSME-B.1922.214.171.1248
A numerical method using dual time stepping and preconditioning procedure for efficient computations of unsteady low speed compressible flow problems is developed. The time-derivative preconditioning method which is valid at low speed flow conditions cannot maintain temporal accuracy because of the modification of the time-derivative term in Navier-Stokes equations. The dual time stepping procedure is incorporated to enable the time accurate computations and this procedure introduces a pseudo-time derivative in addition to the physical time derivative. At a given physical time, an inner iteration can be carried out until a steady state in pseudo-time is achieved. This will effectively yield a time accurate solution. Computational capabilities of the above algorithm are demonstrated through computation of a variety of practical fluid flows and it is shown that the algorithms is efficient in the essentially incompressible flows and low Mach number compressible flows with heat source.
Characterisic Experiment of Tilting Check Valve for Nuclear Power Plant(II)
Yeom, Man-O ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 803~812
DOI : 10.22634/KSME-B.19126.96.36.1993
In this study, testing equipment with which several kinds of valves can be tested was composed. Two kinds of tilting check valves and a swing check valve were tested to analyze their dynamic characteristics. The results of the experiment showed that the tilting check valves protected the pump but that the swing check valve could not protect the pump when the reverse flow rate was high. Also the dynamic equation of the tilting check valve was formulated and simulated using system characteristic constant t
and one method of predicting t
by comparing the results of the simulation with the results of the experiment was proposed.sed.
Combustion and Microexplosion of AI/Liquid Fuel Slurry Droplets(II)-Theoretical Study-
Jo, Ju-Hyeong ; Byeon, Do-Yeong ; An, Guk-Yeong ; Baek, Seung-Uk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 813~822
DOI : 10.22634/KSME-B.19188.8.131.523
The microexplosion of a slurry droplet was considered to be caused by the shell formation and the following pressure build-up in the shell which would be promoted by the suppression of evaporation, subsequent superheating and heterogeneous nucleation of liquid carrier. To closely investigate the pressure build-up and the heterogeneous nucleation, a numerical model was introduced by considering the internal temperature distributions with the shell formation, suppression of evaporation and pressure build-up inside. The microexplosion time was estimated by postulating the limit of superheat for heterogeneous nucleation. The simulation yielded a reasonably good agreement with experimental results for Al/n-heptane slurry droplets under various solid loadings.
Numerical study of compression waves passing through two-continuous ducts
Kim, Hui-Dong ; Heo, Nam-Geon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 823~831
DOI : 10.22634/KSME-B.19184.108.40.2063
In order to investigate the impulsive noise at the exit of high-speed railway tunnel and the pressure transients inside the tunnel, numerical calculations using a Total Variation Dimishing difference scheme were applied to axisymmetric unsteady compressible flow field. Some compression wave forms were assumed to model the compression wave produced in real high-speed railway tunnel. The numerical data were extensively explored to analyze the peak over-pressure and maximum pressure gradient in the pressure wavefront. The effect of the distance and cross-sectional area ratio between two-continuous ducts on the characteristics of the pressure waves were investigated. The peak over-pressure inside the second duct decreases for the distance and cross-sectional area ratio between two tunnels to increase. The peak over-pressure and maximum pressure gradient of the pressure wavefront inside the second duct increase as the maximum pressure gradient of initial compression wave increases. The present results were qualitatively well agreed with the results of the previous shock tube experiment.
Thermodynamic behavior of the composite system composed of two simple ideal gas systems
Jeong, Pyeong-Seok ; Jo, Gyeong-Cheol ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 832~839
DOI : 10.22634/KSME-B.19220.127.116.112
The potential work is defined as the maximum available work extractable from a composite system. It is important concept to understand the behavior of a composite system because it is a property of the composite system and shows the possible room for the system to change its state by itself. To explain this concept quantitatively, the behavior of a composite system composed of two simple ideal gas systems is analyzed. The potential work of the composite system is estimated, the various reversible processes from a given state to the equilibrium state and the processes on which potential works are constant are shown on the T-P and S-V planes. Such an effort will be necessary to understand and characteristics of composite systems as well as helpful for a deeper comprehension of the energy conversion principles.
An experimental study for preliminary design of gas turbine combustor
An, Guk-Yeong ; Kim, Han-Seok ; Jo, Eun-Seong ; Bae, Jin-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 840~848
DOI : 10.22634/KSME-B.1918.104.22.1680
The preliminary design and performance test were carried out for determining dimensions of gas turbine combustor. The combustor design program was developed and applied to design our combustor, and the specific dimensions for swirler, dome and liner holes were determined by the semiempirical manner. Based on the first performance test data, the swirl angle governing the combustion characteristics of primary combustor zone was determined as 40 deg.. Using the second performance test data, the swirler dimensions were readjusted by 24 mm i.d., 34 mm o.d., and swirl angle of 45 deg.. The geometry of liner holes were determined by considering the flame stability and recirculation zone size. It was found that flame can be more easily stabilized by adjusting the swirler dimensions rather than liner holes. The geometry of swirler and liner holes were readjusted by using the final performance test data with dilution holes. Also, the combustor performance and emission characteristics were evaluated by analysis of exhaust gases.
Heat transfer enhancement of finless TEFC induction motor frame by installing guide vanes
Jeon, Chang-Seong ; Go, Sang-Geun ; Yun, Myeong-Geun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 849~859
DOI : 10.22634/KSME-B.1922.214.171.1249
The heat generated in an induction motor is mostly dissipated through the frame. The study on the heat transfer characteristics of a newly manufactured finless TEFC(Totally Enclosed Fan Cooled) induction motor showed/that it had an unsuitable structure in view of the heat transfer. The angle of the cooling air flow was very large and the ribs disturbed the air flow and partially generated the wake region on the frame. In the wake region the temperature was very high. Thus the heat transfer coefficients were lower than those of the frame with fins. Also was investigated the heat transfer characteristics of the motor frame by installing various guide vanes in the fan-side end cap. An optimum heat transfer case was found and the average heat transfer coefficient of the frame was 70% higher and the average coil temperature measured by the resistance method was 9 deg. C lower than that of the frame which had no guide vanes.
A study on 2-D wake flow control by acoustic excitation
Kim, Hyeon-Jin ; Kim, Jae-Ho ; Kim, Myeong-Gyun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 860~873
DOI : 10.22634/KSME-B.19126.96.36.1990
In a low speed open-type wind tunnel, a group of parallel wakes downstream of two dimensional grid model consisting of several circular cylinders were experimentally investigated to study the response of the wake flows to the acoustic excitation, in hoping to promote the understanding of the underlying mechanism behind the gross flow change due to artificial excitation. In the unexcited wake flows, the development of the individual wakes behind cylinders was almost uniform for the ratio of the spacing to the cylinder diameter of s/d.geq.1.5. For smaller s/d, however, the jet streams issued through the gaps between the cylinders became biased in one side and the cylinders had wakes of different sizes. At s/d=1.25, the gap flow directions change in time, leading to unstable wake patterns. Further reduction in s/d made this unstable flip-flopping of the jets stable. The most effective excitation frequency was found to be in the Strouhal number range of St=0.5-0.6. This frequency was related to the vortex shedding. At s/d=1.75, the excitation frequency was 2 or 4 times the vortex shedding frequency. When the flow was excited at this frequency, the vortex sheddings were energized, and pairings between neighboring vortices were generated. Also, the merging process between individual wakes was accelerated. The unstable and unbalanced wake patterns at s/d=2.15 were made stable and balanced. The unstable and unbalanced wake patterns at s/d=2.15 were made stable and balanced. For smaller spacing of s/d .leq,1.0, the acoustic excitation became less effective in controlling the flow.
Development of 2-frame PTV system and its application to a channel flow
Baek, Seung-Jo ; Lee, Sang-Jun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 874~887
DOI : 10.22634/KSME-B.19188.8.131.524
A 2-frame PTV (particle tracking velocimetry) system using the concept of match probability between two consequent image frames has been developed to obtain instantaneous velocity fields. The overall 2-frame PTV system including image pre-processing, tracking algorithm and post-processing routine was implemented to apply to real flows. The developed 2-frame PTV system has several advantages such as high recovery ratio of velocity vectors, low error ratio and small computational time compared with the conventional 4-frame PTV and the FFT-based cross-correlation PIV technique. The 2-frame PTV system was applied to a turbulent channel flow over a rectangular block to check its reliability and usefulness. Total 96 sequential image frames have been captured and processed to get both mean and fluctuating velocity vector fields over the recirculating region. The mean velocity and turbulent intensity profiles were well agreed with hte LDV measurements in the separated region behind the block. Time-averaged reattachment length is about 6.3 times of the block height.
Cooling characteristics of the multichip module using paraffin slurry
Jo, Geum-Nam ; Choe, Min-Gu ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 6, 1998, Pages 888~898
DOI : 10.22634/KSME-B.19184.108.40.2068
The present study investigated the effects of the experimental parameters on the cooling characteristics of the multichip module cooled by the indirect liquid cooling method using water and paraffin slurry. The experimental parameters are mass fraction of 2.5 ~ 7.5% for paraffin slurry, heat flux of 10 ~ 40 W/cm
for the simulated VLSI chips and Reynolds numbers of 5,300 ~ 15,900. The apparatus consisted of test section, paraffin slurry maker, pump, constant temperature baths, flowmeter, etc. The test section made of in-line, four-row array of 12 heat sources for simulating 4 * 3 multichip module which was flush mounted on the top wall of a horizontal rectangular channel with the aspect ratio of 0.2. The inlet temperature was 20 deg. C for all experiments. The size of paraffin slurry was constant as 10 ~ 40 .mu.m befor and after the experiment. The chip surface temperatures for paraffin slurry with the mass fraction of 7.5% showed lower by 16 deg. C than those for water when the heat flux is 40 W/cm
. The local heat transfer coefficients for the paraffin slurry with the mass fraction of 7.5% were larger by 17 ~ 25% than those for water at the first and the fourth row. The local heat transfer coefficients reached to a row-number-independent, thermally fully developed value approximately after the third row. The local Nusselt numbers at the fourth row for paraffin slurry with the mass fraction of 7.5% were larger by 23 ~ 29% than those for water.