All issues
Successor
Volume 69, Issue 683
Displaying 1-24 of 24 articles from this issue
- |<
- <
- 1
- >
- >|
-
Kyoji KAMEMOTO, Teruhiko KIDA2003 Volume 69 Issue 683 Pages 1564-1569
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSA brief remark on the recent development of the vortex method is presented in this paper. In Section 2, the primary governing equations for the vortex method is derived from the Navier-Stokes equations, and in Section 3 typical vortex methods are briefly remarked. The vortex method is essentially applicable to the turbulent flow, so that in Section 4 the recent development to the turbulent flows is discussed.View full abstractDownload PDF (732K) -
Koichi FUKUDA, Hiromu SUGIYAMA, Kazuhide MIZOBATA, Kiyokazu ENDO, Liqu ...2003 Volume 69 Issue 683 Pages 1570-1576
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSThis paper describes an experimental study on the internal structure of the Mach 4 pseudo-shock wave (PSW) in a straight square duct with cross section of 80×80 mm2, using the new Mach 4 supersonic wind tunnel of Muroran Institute of Technology. The free stream Mach number, unit Reynolds number, and flow-confinement just upstream of the PSW were M∞=3.98, Re=2.6×107 m-1, and δ∞/h=0.39, respectively, where δ∞ is the boundary layer thickness, and h is the half height of duct. The development and characteristics of the turbulent boundary layer on the top and bottom walls of the duct was investigated by LDV measurements. The internal structure of the Mach 4 PSW was clarified by color schlieren photographs and Particle Image Velocimetry (PIV) measurements. It reveals that the turbulent boundary layer on the top or bottom wall of the duct separates in large just after the first oblique shock of the PSW, and the internal flow with the PSW becomes asymmetric flow.View full abstractDownload PDF (1047K) -
Masashi YAMAKAWA, Kenichi MATSUNO2003 Volume 69 Issue 683 Pages 1577-1582
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSUnstructured grid system is suitable for flows with complex boundary geometry's. As for the problem with moving boundary walls, the grid system is also changing and deforming with time. In this paper, a new moving-grid finite volume method on unstructured grid system is presented and developed for unsteady compressible flows. To assure geometric conservation laws on moving grid system, a control volume on the space-time unified domain is adopted for estimating numerical flux. The method is implicit and is solved iteratively at every time step in order to assure both the geometric conservation laws and numerical accuracy. The method is described for two-dimensional flows and validated using simple test problems. Application to a piston problem and a gun tunnel problem has shown a promising feature of the method.View full abstractDownload PDF (759K) -
Hiroshi OHUE, Genshi KAWASHIMA2003 Volume 69 Issue 683 Pages 1583-1589
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSAn experimental study is performed to disclose the unsteady flow inside a rotating drum induced by an impulsive start of motion. Laser Doppler velocimeter (LDV) is employed to determine the distribution of both the angular and radial velocity components in the flow field on the meridional plane in the rotating drum. The laser light sheet method is also engaged to enable visualization of flow patterns. Fluid viscosity, drum size and rotational speed are varied to determine their effects on the flow. From these results, the time history of the distribution of both the angular and radial velocity are disclosed. The time history of Ekman boundary layer thickness are also determined from radial velocity distribution.View full abstractDownload PDF (879K) -
Koichi YONEZAWA, Kazuhiko YOKOTA, Yasuhide WATANABE, Yoshinobu TSUJIMO ...2003 Volume 69 Issue 683 Pages 1590-1598
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSIn the present paper, the experimental and numerical investigations are performed to clarify the mechanism of the side load in rocket nozzles using two types of nozzles-modified ideal nozzle and modified compressed truncated perfect (CTP) nozzle. In the experiment, the flow field is visualized by the Schlieren method and asymmetric flow patterns are observed. In the modified CTP nozzle, two types of the separation patterns are observed. One is "free shock separation" and the other is "restricted shock separation." The numerical simulations predict that the transition of separation pattern from the FSS to the RSS causes a large impulsive side load. It is also shown that the flow in a two-dimensional nozzle can be three dimensional due to flow separation on the side wall.View full abstractDownload PDF (1111K) -
Motomu NAKASHIMA2003 Volume 69 Issue 683 Pages 1599-1606
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSIn the preceding papers, we developed a linear theory for a two-joint dolphinlike propulsion mechanism, which was a simplified model of high speed swimming animals. However, the effect of the simplification implied in that theory has not been quantitatively discussed so far. To this end, in this paper, by using the three-dimensional panel method, the effects which authors' linear theory can not treat on propulsive characteristics are examined. First, we investigate the fluid force acting on the body part. It is found that the calculated values of the amplitude of the fluid force by the linear theory becomes 10 to 20% larger than those by the panel method, while the values of the phase of the fluid force by those two methods agree well. Next, we examined the effects of the presence of the body and the surging motion of the caudal fin on propulsive characteristics. It is found that the presence of the body makes the propulsive efficiency slightly lower and that the surging of the caudal fin produces higher thrust but lower propulsive efficiency.View full abstractDownload PDF (915K) -
Yasuyuki TANAKA, Masanobu IIDA, Katsuhiro KIKUCHI2003 Volume 69 Issue 683 Pages 1607-1614
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSA method to simulate the generation of tunnel compression wave at train entry is investigated by using a simple geometry model. The tunnel is represented by a circular and the train by an axisymmetric body which has a cross-sectional area distribution equivalent to that of an actual train. In order to simulate the entry into a double tracked tunnel, the train center axis is positioned offset from the tunnel axis and the effect of the ground plane is treated by the mirror image method. Analysis and model experiments are performed to confirm the validity of the present method to use a simple geometry model. The difference of the peak pressure gradient of the compression wave has turned out to be within a few percent between field measurements and model experiments.View full abstractDownload PDF (925K) -
Yasufumi KONISHI, Masahito ASAI2003 Volume 69 Issue 683 Pages 1615-1620
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSThe streak instability is examined experimentally through artificially producing spanwiseperiodic low-speed streaks in a flat-plate laminar boundary layer. The observation focuses on sinuous instability modes which are responsible for the regeneration of quasi-streamwise vortices in near-wall turbulence. Effects of the interaction between disturbances developing along the neighboring streaks on the instability are examined through comparing the disturbance development for various streak spacing. The instability characteristics are also compared with those for a single low-speed streak. The development of subharmonic modes does not strongly depend on the streak spacing and they grow with almost the same growth rate as that for the single streak. By contrast, the development of fundamental modes is very sensitive to the streak spacing, and is completely suppressed when the streak spacing is less than 2.5 times the streak width.View full abstractDownload PDF (842K) -
Masami SUZUKI, Chuichi ARAKAWA2003 Volume 69 Issue 683 Pages 1621-1627
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSWells turbine can rotate in the same direction irrespective of reciprocating airflow produced with wave energy. The good performance is required from 0 to 90 degrees of attack angle because the turbine is driven in the operating condition and must be able to self-start. This is a report of a fundamental study on the design method that includes the interaction between air chamber and turbines, using the rule of similarity in the non-dimensional form of governed equations. It is presented how to analyze the power absorbed in irregular waves and the staring characteristics by use of probability. Turbine performances in irregular waves are easily shown with the probability density distribution, that is, Gaussian distribution. It is described that a optimal turbine is selected by only the turbine characteristics regardless of the air chamber. The method is very useful to select the optimal.View full abstractDownload PDF (666K) -
Hoshio TSUJITA, Yasuhiro ISHIDA, Shimpei MIZUKI, Atsumasa YAMAMOTO2003 Volume 69 Issue 683 Pages 1628-1636
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSThe secondary flow within a passage of a turbomachinery exhibits a complex flow pattern by the effects of the centrifugal and the Coriolis forces. In this secondary flow, the passage vortex generates a major part of the losses. However, the mechanism of the loss generation by the secondary flow has not been fully clarified yet. In this point of view, the passage vortex is closely examined by the numerical computations using the curved square ducts as fundamental models for the generation of the passage vortex. The inlet boundary layer thickness and the inlet velocity profiles are chosen as the major parameters affecting the generation of passage vortex in the present study. The computed results exhibited that the passage vortex gave the predominant effects for the generation of loss not only in the breakdown process but also in the development process.View full abstractDownload PDF (1066K) -
Kazuhiko TOSHIMITSU, Takeshi OTSUKA, Hiroko HANDA, Masanobu NAMBA2003 Volume 69 Issue 683 Pages 1637-1643
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSThe paper presents a theoretical analysis and an experimental study of blade flutter suppression by means of active acoustic excitation. In the theoretical analysis, a linearized mathematical method to calculate the aerodynamic force and work on an oscillating airfoil interacting with sound waves generated from a loud-speaker mounted at a wall surface of a wind tunnel is formulated. Dependence of the suppression effect on the location, width of the actuator surface and the phase difference between the blade and actuator surface oscillations are investigated. Both theoretical and experimental results show that the actuator surface oscillation most effectively suppresses a coupled bending-torsional oscillation of the blade when the center of the loud-speaker diaphragm is placed a quarter blade chord downstream from the leading edge of the blade. Furthermore a 12.5% increase in a critical flutter velocity could be attained by the active control system.View full abstractDownload PDF (690K) -
Takashi TOKUMASU, Taku OHARA, Kenjiro KAMIJO2003 Volume 69 Issue 683 Pages 1644-1650
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSIn this paper the effect of molecular structure on thermal conductivity of diatomic liquid is analyzed by the Molecular Dynamics (MD) Method. Five liquids such as O2, CO, CS2, Cl2 and Br2 are assumed and 2 center Lennard-Jones (2 CLJ) potential is used for these molecules. First, simulations are performed at various combinations of density and temperature and Equation of State (EOS) of each liquid is obtained by using these results. Using the equations critical temperature and density of each liquid is obtained. Thermal conductivities of these liquids at the corresponding state based on each critical temperature and density (T=0.7Tcr and ρ=2.24ρcr) are simulated and the results are compared with experimental results. Moreover, these results are reduced based on m, ρcr and Tcr and compared with each other. The reduced thermal conductivity increases as the elongation of molecule increases.View full abstractDownload PDF (743K) -
Masanori MONDE, Wei LIU, Yuhichi MITSUTAKE, Takayoshi YEE2003 Volume 69 Issue 683 Pages 1651-1658
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSAn analytical method has been developed for predicting position of moving heat source using an inverse solution, which is explicitly given for two-dimensional heat conduction by using Laplace transform technique. Three procedures are possible using the inverse solution in order to predict moving heat source : the first one is to look for a maximum value of derivative of surface heat flux with respect to time, the second with respect to a coordinate along moving heat source, the third a maximum heat flux. The maximum value of derivative of surface heat flux with respect to time is analytically found to be the best among them to predict its position. The maximum heat flux is experimentally easier than the maximum derivative to follow the wetting point, although the maximum heat flux appears a little after the wetting point does.View full abstractDownload PDF (865K) -
Hiroaki TANAKA, Shigefumi NISHIO2003 Volume 69 Issue 683 Pages 1659-1665
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSThe model for high heat-flux boiling, introduced in this paper, is based on a similarity between dropwise condensation and high heat-flux boiling, observed in simultaneous visualization experiment of liquid-solid contact and bubble structure. The bubble coalescing process in boiling on a horizontal flat surface is formulated into integral equations, assuming random positioning of dry patches and bubbles. Taking the nucleation site density and the activeness of nucleation sites, measured by image processing technique, into account, the equations are numerically solved to yield a dry patch diameter distribution as a result of cyclic process of bubble nucleation, transient bubble growth and bubble departure. The three-phase contact-line density, calculated from the dry patch distribution, has a maximum point, similar to that of experimental data. This model has a potential to explain the CHF as the extreme of smooth boiling curve, regarding wall superheat as the driving force of the CHF phenomenon.View full abstractDownload PDF (932K) -
Kazunari MOMOSE, Kouhei ABE, Hideo KIMOTO2003 Volume 69 Issue 683 Pages 1666-1672
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSA reverse computation based on adjoint formulation of forced convection heat transfer is proposed to obtain the optimal thermal boundary conditions for heat transfer characteristics ; such as a total heat transfer rate or a temperature at a specific location. In the reverse analysis via adjoint formulation, the heat flow is reversed in both time and space. Thus, using the numerical solution of the adjoint problem, we can inversely predict the boundary condition effects on the heat transfer characteristics. As a result, we can obtain the optimal thermal boundary conditions in both time and space to control the heat transfer at any given time.View full abstractDownload PDF (1011K) -
Ryozo ECHIGO, Takeshi HARA, Masaru HIRATA2003 Volume 69 Issue 683 Pages 1673-1678
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSIt is important to understand the frozen-melting behavior of thermal active layer in permafrost area for dual periodic temperature changes combined with daily and annual cycles. The numerical results are compared with the single cyclic change and discussed on the temperature profiles in detail. The thermal structures are revealed to be consisted of dual Stokes depths and, in consequence, the net heat fluxes at the surface are illustrated to be affected by daily cycle to a certain extent. The influences on temperature profiles due to daily cycle penetrate only in Stokes depth pertinent to its own cycle, while the entire tempkrature distributions are decided by the annual cycle. Additionally, a simple experiment is performed to demonstrate the validity of the findings, predicted in former paper, regading the temperature decreases in deep underground compared with an average (or initial) surface temperature, which is essential to form the permafrost structure.View full abstractDownload PDF (732K) -
Shigeki HIRASAWA, Masato IKEGAWA, Akihiro GUNJI, Hiroyuki ISHIBASHI, T ...2003 Volume 69 Issue 683 Pages 1679-1684
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSTemperature distributions in a GSO crystal during Czochralski single-crystal growth were numerically investigated by 2D axisymmetric thermal radiation heat transfer analysis with conduction. As properties of the GSO crystal changed from transparent to opaque at a wavelength of 4.5 nm, the band-energy approximation was used. We assumed that the melt was opaque with a constant temperature. Longitude and radial temperature distributions in the crystal were calculated by changing parameters of the apparatus. Radial temperature distribution was always large at the top of the crystal. There are the optimum height, diameter and temperature of the crucible to reduce radial temperature distribution in the crystal in the crucible. Low thermal conductivity of insulator and top lid of the insulator are effective to reduce radial temperature distribution at the top of the crystal. Radial temperature distribution increased when the diameter of the crystal was large.View full abstractDownload PDF (686K) -
Junya TAKAHASHI, Osamu FUJITA, Kenichi ITO2003 Volume 69 Issue 683 Pages 1685-1691
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSThe objective of this work is to provide information about the details of the effect of light wavelength on radiative ignition of solid material. An experiment of radiative ignition has been performed in microgravity to determine the events occurring in ignition processes in a quiescent atmosphere. Filter papers were irradiated by infrared radiation (CO2 laser 10.6 μm) or near infrared radiation (Diode laser, 800.1 nm). The ignition delay was measured for various experimental conditions, and the density change of gas phase before ignition were observed by a Mach-Zehnder interferometer. The results showed that the ignition delay time of the infrared radiation was much shorter than that of near infrared radiation, and it was observed that the difference of light wavelength of radiations had a strong effect on the ignition process. It was suggested that one of main reasons to give the difference was the difference of radiative absorption in gas phase as well as the difference of absorptivity by solid surface according to the Mach-Zehnder interferometer.View full abstractDownload PDF (823K) -
Yoshitaka KATO, Kunio YOSHIKAWA2003 Volume 69 Issue 683 Pages 1692-1697
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSHigh temperature air gasification of wood sawdust was done using 200 kg/day scale pebble bed slagging gasifier, where ceramic balls were packed below the entrained bed section. Tar free syngas was successfully produced, where achieved calorific value of the syngas was 3 697 MJ/Nm3 (883 kcal/Nm3), the cold gas efficiency was 53% and the carbon conversion rate was 86%. Compared with the experiment using crushed coal as a fuel, the carbon conversion rate was low due to poorer capturing efficiency of char in the pebble bed caused by low ash content of sawdust. To raise carbon conversion rate, two measures were tested. One measure is to increase the air exoess ratio. Another is to increase the length of the entrained bed section to enhance the reaction time of fuel in the entrained bed section. Both measures were effective for increasing the carbon conversion rate, where increase of the length of entrained bed section is effective for both increasing the carbon conversion rate and the cold gas efficiency.View full abstractDownload PDF (774K) -
Hiroshi KAWANABE, Graham K. HARGRAVE, Tim C. WILLIAMS2003 Volume 69 Issue 683 Pages 1698-1703
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSThe velocity field and the temperature distribution are measured simultaneously in a nonpremixed jet flame by applying particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) of nitric oxide with known concentration added as a tracer. The fuel flow of low temperature is surrounded by the high temperature region. Also, turbulence kinetics in a jet flame was analyzed based on the statistical characteristics of the temperature and velocity, including mean velocity, turbulence intensity and Reynolds stress. It was shown that u' is quickly decayed in the high temperature region. And the maximum point of density weighted average of Reynolds stress is located at fuel stream side of shear layer. As a result, production of the turbulence is mainly occurred in the fuel stream.View full abstractDownload PDF (887K) -
Yoshiaki HANEDA, Yoshiaki TSUCHIYA, Hideo KURASAWA, Kazuyoshi NAKABE, ...2003 Volume 69 Issue 683 Pages 1704-1711
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSExperiments of jet impingement heat transfer were performed for the case that a circular cylinder was inserted into a two-dimensional slot jet. The diameter of the cylinder and its insertion location were changed to investigate their effects on the heat transfer rates on the target surface. The distance between the slot and the surface was kept constant to be 3 or 5 times of the slot width, h=l5 mm. The Reynolds number based on the slot width was fixed at 9 500 for the heat transfer experiments, and 4 800 for flow visualization. Two kinds of flow pattern behind the cylinder were observed, which corresponds well to pressure distributions in the near-field of the geometrically-obtained stagnation point and also the Nusselt number distributions. The peak Nusselt number in the case of the insertion location relatively close to the slot was found to be at most two times higher than that in the case without the cylinder insertion.View full abstractDownload PDF (881K) -
Eiji KINOSHITA, Choesnul JAQIN, Kazunori HAMASAKI2003 Volume 69 Issue 683 Pages 1712-1718
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSIn order to clarify the utilization of palm oil methyl ester (PME) as an alternative diesel fuel, the engine performance with PME and the exhaust emissions from PME are investigated using a swirl-chamber diesel engine. Rapeseed oil methyl ester (RME) and gas oil also are tested to compare with PME. The results show that ignition delay of PME is shorter than those of RME and gas oil, that brake thermal efficiency with PME is slightly higher than one with gas oil, and that NOx and Smoke emissions from PME simultaneously are lower than those from gas oil. Moreover, blended fuels of PME with gas oil also are tested to improve the pour point of PME and use PME in lower ambient temperature. As a result, although the pour point of PME is 12.5°C, one of 50 mass percent blended fuel reduce to 0°C. NOx and Smoke emissions of the blended fuels are depended on the mixing ratio.View full abstractDownload PDF (816K) -
Sanyo TAKAHASHI, Hiroyuki MORITA, Osamu KURATA, Iwao YAMASHITA2003 Volume 69 Issue 683 Pages 1719-1726
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSCharacteristics of hydrogen internal combustion Stirling engine were analyzed by comparing the engine performances on steam injection and H2-O2 injection. The experimental results of the steam injection showed that the internal conversion efficiency and pressure ratio increased to comparable levels with H2-O2 injection. Also, a two-space model predicted the concentration of steam in high temperature space to be around 3% from the pressure rises in the steam injection and the H2-O2 injection experiment. Simulations and estimations on these characteristics suggested a large amount of steam condensed and the condensed water evaporated at the regenerator in a cycle, leading to the conclusion that the performance improvement in the hydrogen internal combustion Stirling engine was caused by not only temperature increase in the expansion space but also the condensation-evaporation of water at the regenerator.View full abstractDownload PDF (902K) -
Yoshihiro NABARA, Yoshihiro OKUNO2003 Volume 69 Issue 683 Pages 1727-1732
Published: July 25, 2003
Released on J-STAGE: March 28, 2008
JOURNAL FREE ACCESSMHD flow behavior and the performance of a middle scale nonequilibrium subsonic disk MHD generator have been examined with time-dependent r-z two- and r-θ-z three-dimensional numerical simulations. The generator performance, such as the enthalpy extraction ratio and the isentropic efficiency, can be varied time-dependently because the boundary layer separation occurs and the fluid flow fluctuates in the diffuser. However a mean enthalpy extraction ratio of 23% and a mean isentropic efficiency of 83% are achieved for the optimal load resistance under the inlet stagnation pressure of 0.75atm. This performance is almost high enough for the commercial generator. When the low electron temperature plasma flows into the generator channel, the ionization instability occurs and the discharge structure becomes nonumiform in θ-direction, which deteriorates the generator performance considerably. This fact indicates the importance to produce the proper plasma for the power generation by optimizing the generator channel or utilizing the preionization.View full abstractDownload PDF (844K)
- |<
- <
- 1
- >
- >|