Theoretical and Applied Mechanics Japan
Online ISSN : 1349-4244
Print ISSN : 1348-0693
ISSN-L : 1348-0693
Volume 57
Showing 1-50 articles out of 57 articles from the selected issue
INVITED PAPAR
I. SOLID AND STRUCTURAL MECHANICS
  • Kohji OHTSUKA
    2009 Volume 57 Pages 25-32
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    Griffith’s energy balance theory is a powerful concept as the criterion for the crack initiation. However the theory has little success in the crack extension process. If we want stop the running crack, we must weaken the loading, but the theory is true under constant loading. Moreover, the theory is of no help to know when the crack will stop. In this paper, they are overcome by considering the second order expansion of the energy release rate with respect to time and redefining the energy release rate under varying load.
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  • Kazuhiko MINAKUCHI, Tetsukazu KIDA, Toshiaki SAWANO, Kiyoshi KATO, Tad ...
    2009 Volume 57 Pages 33-40
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    After the Hyogoken-Nanbu Earthquake, earthquake-resistant reinforcement and repair of in-service reinforced concrete (RC) bridge piers was carried out. To develop a design concept for reinforcing RC columns to resist earthquakes, the authors conducted a compressive test on concrete columns confined by steel pipes of three different wall thicknesses, analyzed the deformation of the concrete columns, and studied the effectiveness of confining concrete columns with steel pipes. The authors propose a simplified equation for calculating the compressive strength from the relationship between the thickness of the steel pipe wall and the confinement strength ratio. The authors also propose an equation for calculating the compressive strength taking into account the stress state of a column model based on the strains obtained from the test.
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  • Toshihiro NODA, Kentaro NAKAI, Akira ASAOKA
    2009 Volume 57 Pages 41-47
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    By using a soil-water coupled finite element method, deformation/failure behavior during and after the occurrence of an earthquake in a clay foundation-embankment system was numerically examined. The elasto-plastic constitutive model named Super/subloading Yield Surface Cam-clay model (SYS Cam-clay model in short) is applied for soil skeleton. The embankment was modeled as a saturated soil. The results showed that the embankment maintained stability without any significant large deformation during the earthquake, while slip failure penetrating to the crest was suddenly generated a few hours after the earthquake.
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  • Mohamad Nazieh JLILATI, Yusuke HONJO
    2009 Volume 57 Pages 49-56
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    The sources of uncertainties in reliability analysis are usually classified to four categories, namely physical uncertainty, model uncertainty, statistical uncertainty and gross error. In the actual situation, however, what we observe is combined result of all these uncertainties. The purpose of this study is to quantitatively evaluate the physical uncertainty(i.e. spatial variability of soil properties), taking the settlement and the differential settlement prediction of a flexible square shallow foundation on statistically homogeneous elastic ground, as an example. 3-D conditions have been examined when calculating the differential settlement. The method introduced to evaluate the spatial variability of the ground property is Monte Carlo simulation(MCS).
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  • Ming-Chien HSU, Tetsukazu KIDA, Tadashi ABE, Toshiaki SAWANO, Yoshitak ...
    2009 Volume 57 Pages 57-65
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    From a series of experiments, the authors proposed a calculation for bending moment capacity of RC beams reinforced with Carbon Fiber sheets (CFS) by using strain distribution calculation under flexure at the ultimate limit state. Moreover, the authors modified the yield strength of steel reinforcing-bars and added a coefficient of CFS reinforcing effect as a function of beam aspect ratio in the calculation. Authors did this by adding extra modifying coefficients into the bending moment capacity equation. In addition, the theoretical bending moment capacity equations from repair manual of CEB-FIP and ACI were compared with the modified equation. Furthermore, the bending moment from Finite Element Method (FEM) would be also compared with the modified equation.
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  • Takakuni TATSUMI, Hidenori YOSHIDA
    2009 Volume 57 Pages 67-72
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    The mechanical behaviors of a discontinuous rock mass are strongly affected by discontinuities included in the rock mass. The surrounding rock mass around an underground cavern is subjected to compressive stress even after a cavern excavation. In this case, the shear properties of the discontinuity play an important roll in the macroscopic behavior of the rock mass. In this article, the experimental and numerical studies in terms of the material having a single discontinuity are conducted in order to seize the mechanism of the alteration of the shear properties. In the numerical study, the alteration is modeled by the concept that the surface of the discontinuity can be worn away with increasing the load which is applied to the material. Through the comparison between the experimental and numerical studies, it is turned out that the macroscopic behaviors of the rock mass are influenced by the friction of discontinuity.
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  • Satoru NISHIKAWA, Sei'ichiro FUKUSHIMA, Harumi YASHIRO
    2009 Volume 57 Pages 73-80
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    In order to draw BCP (Business Continuity Plan) for supply chain dependent enterprise, there is a need for a quantitative risk analysis method to evaluate such manufacturing system. The business interruption time (BIT) is a crucial factor in terms of economic loss. Two model enterprises each with three factories connected through series and parallel supply chain patterns are applied in comparing and analyzing the risk. The annual exceedance probability of BIT of these enterprises are calculated and compared. The BIT risk of series supply chain is greater than the parallel. Three alternative options, by provision of redundant nodes, for decreasing the risk are proposed. The options are examined from the viewpoint of BCP. This risk analysis method is proven to be realistic and functional.
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  • Tomonori YAMADA, Fumimasa ARAYA, Akemi NISHIDA, Noriyuki KUSHIDA, Nori ...
    2009 Volume 57 Pages 81-87
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    We realize a vibration table in an extended world for simulation, which is capable of emulating the real world's earthquake in digital space and brings concurrent experiments between real and digital one. There is currently a lack of methodologies and technologies for simulating huge and complex structures such as a nuclear facility. In this paper, a methodology for reproducing facilities in an extended world is proposed through analysis of assembled structures, as well as introduction of the computing framework used. The first attempt at analyzing an assembly was accomplished by structural finite element analysis and by integrating the components of an actual facility. Since the assembly analysis necessitates a massive computational cost, a grid computing environment was applied to the computational resources. Numerical experiments were performed for a test reactor. Assembly analysis using the finite element method was confirmed to be capable of analyzing a huge and complex facility.
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  • Thirapong PIPATPONGSA, Tomohide TAKEYAMA, Hideki OHTA, Atsushi IIZUKA
    2009 Volume 57 Pages 89-94
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    Discontinuity at the vertex of the Sekiguchi-Ohta model causes numerical troubles when associated flow rule is applied because the singularity encountered in the derivatives of yield function. Based on Koiter's associated flow rule, the numerical implementation to accommodate the vertex singularity had been generalized. The set of applied strains had been formulated and defined as the domain of metastability. This study is focused on validity of the domain of metastability by a regularized method. Infinitesimal vicinity adjacent to the vertex is considered to regularize all of plastic flow in outwards normal direction to the yield surface. It was confirmed that the metastable domain of the Sekiguchi-Ohta model is bounded by an elliptical cone in principal strain space.
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  • Tadashi ABE, Tetsukazu KIDA, Toshiaki SAWANO, Atsuya KOMORI, Syuniti H ...
    2009 Volume 57 Pages 95-103
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    A method of reinforcing RC slabs for road bridges against cracking damage by using CFS is investigated in the present study. Static load tests were carried out on three types of RC slab test specimens having different number of layers of CFS. The reinforcement effect of different number of CFS layers and the reduction coefficient to be applied to the CFS tensile strength was investigated. A punching shear mechanical model and load resistance equation for CFS reinforced RC slabs was proposed. The results showed that a reinforcement effect of a factor of 1.35 was obtained for CFS reinforced RC slabs relative to RC slabs, and this factor is unaffected by the number of layers. Also, there was an inverse relationship between the ultimate load on the test specimen or the strain in the CFS and the number of layers, so that the ultimate load on the test specimen and the strain in the CFS reduced as the number of layers increased. By applying this reduction in strain with respect to the tensile strength of the CFS as the reduction coefficient to the proposed equation for the punching shear load resistance, good agreement between test values and the theoretical values were obtained.
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  • Aya NIIMI, Tadashi ABE, Tetsukazu KIDA, Makiko TAKANO, Satoshi TANAKA
    2009 Volume 57 Pages 105-112
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    This paper describes a single-plane shear test conducted on the composite surface of UFC form and RC slab that have the most influence on the ultimate strength of RC slab using UFC laying form to propose evaluation equations based on the relationship between the compression strength and shear strength of concrete. Further, static load tests were carried out with specimens made of RC slab using UFC laying form to solve the failure mechanism and to reveal ultimate load-carrying capacity as well as to propose dynamic model and its punching shear evaluation equations applied with the shear strength of the composite surface.
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  • Toru TSUCHIKURA, Masao SATAKE
    2009 Volume 57 Pages 113-118
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    This paper proposes a method of statistical analysis for tensor quantities, which is explained by using the loop tensor defined for the particle graph of a granular assembly. As an example, we analyzed the change of distribution of void shapes in a computer simulation result of a biaxial compression test.
    The loop in a particle graph of a granular assembly corresponds to a local void in the two dimensions. Therefore, the loop tensor is considered to quantify the local voids. The loop tensor is decomposed into the scalar and deviatoric part, which are related with the size and anisotropy of a loop, respectively. Applying the statistical analysis to the loop tensor, we obtained an interesting result that the change of inhomogeneity of micro-structure during shear deformation is comparable to that of the volumetric strain in the granular assembly.
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  • Yoichi WATANABE, Jun OTANI, Nicolas LENOIR, Daiki TAKANO, Toshifumi MU ...
    2009 Volume 57 Pages 119-124
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    The purpose of this paper is to evaluate precise strain field of sand in three dimensions using X-ray CT. Here in this paper, the displacements in the soil are visualized under triaxial compression due to tracing the large number of soil particles and a proper method of image processing analysis is used in order to make the image quantify. Finally, the displacements under triaxial compression in three dimensions are evaluated quantitatively and as a result, the strain field in the soil specimen is calculated using numerical analysis based on the quantified CT data.
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II. DYNAMICS AND OPTIMIZATION
  • Masaya SHIGETA, Toshimasa MIURA, Seiichiro IZAWA, Yu FUKUNISHI
    2009 Volume 57 Pages 127-134
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    The purpose of this study is to develop an energy-efficient active-control device that can control cavity noise. A new control device using fluidic oscillator systems is tested, and its noise suppression effect is evaluated for cases when the oncoming boundary layer is either laminar or turbulent. As a result, it is demonstrated for the laminar flow case that a single fluidic device can completely suppress the peak cavity noise as well as the harmonic components. In the turbulent separating flow case, it is demonstrated that two synchronized devices are necessary to suppress the cavity noise.
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  • Kensuke BABA, Mai MITSUOKA, Yudai FURUNO
    2009 Volume 57 Pages 135-145
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    Adaptive identification systems are available for obtaining dynamic properties of structural construction in the off-line loop as well as searching damage spots in the on-line loop. The systems are constructed with estimative parameters evaluated uniquely when observing multiple input and output signals on vibrating structures. Objective parameters of characteristic property are estimated interactive with practical moderation factors when taking into account the delay time of estimative parameters run behind observed signals.
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  • Hiroki YAMAMOTO, Keiichi ISHIOKA, Shigeo YODEN
    2009 Volume 57 Pages 147-158
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    Fundamental dynamics of two-dimensional atmospheric general circulations symmetric about the rotation axis of planets is investigated to obtain a wide perspective from the Held and Hou model of the Hadley circulation to the Venus-like super-rotation driven by the Gierasch mechanism.A parameter sweep experiment is performed to explore steady solutions of the axisymmetric primitive equations of the Boussinesq fluid on a rotating sphere. Sweep parameters are the external thermal Rossby number (RT), the horizontal Ekman number (EH), and the vertical Ekman number (EV). Two indices are introduced to make a dynamical analysis of the numerically obtained circulations: a measure of the intensity of super-rotation (S) and a measure of rigid rotation (Rg). The characteristics of steady solutions change largely in a certain range of EH for given RT and EV. Approximate positions of this transition can be estimated theoretically as EH∼ EV S(RT), where SRT for RT ≤ 1 and S ∼ √RT for RT > 1.
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  • Atsushi ITO, Hiroaki NAKAMURA
    2009 Volume 57 Pages 159-167
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    We define local momentum density as the vector field of momentum using Dirac’s delta functions. The local momentum density should satisfy the continuity equation with a tensor field and then this tensor field is regarded as local momentum flux composed of advective term and stress tensor. From this theory, when the target region is selected arbitrarily, the stress tensor and pressure tensor on the target region can be calculated by particle simulations such as molecular dynamics simulation. Because the distribution function is not required by this theory, the stress tensor can be calculated in the non-equilibrium molecular dynamics.
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  • Daisuke KUBO, Shinji SUZUKI
    2009 Volume 57 Pages 169-178
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    The transitional flight control of tail-sitter aircraft is a challenging problem because the flight includes a wide operating range with nonlinearity and at low speed approaches the stall. In order to solve this problem, a robust autopilot design method using a variable environment genetic algorithm (VE-GA) is proposed. VE-GA is a new robust optimization method based on a real coded genetic algorithm (RCGA). Here, the word “environment” refers to the uncertainties considered in the evaluation functions. In a VE-GA, the environment is changed repeatedly after several generations. In this manner, genes go through many types of environments over generations, and obtain robustness against uncertainties. In order to improve the efficiency and accuracy of the optimization, we introduce a local optimization method. Finally, our proposed method is applied to the offline-based parameter optimization of a neural network (NN) which is part of a tail-sitter mini unmanned aerial vehicle's (UAV) autopilot architecture.
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  • Hiraku NISHIMORI, Atsunari KATSUKI, Hiromi SAKAMOTO
    2009 Volume 57 Pages 179-184
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    A coupled ODEs model is proposed to describe the collision process of barchan dunes under a few number of basic mathematical and phenomenological assumptions. Using the model the transition between coalescence and ejection of two colliding barchans depending on their initial sizes is theoretically studied, and it is shown that this simple model supplies us with a new viewpoint for clear-cut understanding of the seemingly complex dynamic of dunes.
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  • Takashi SUZUKI, Ryo TAKAHASHI
    2009 Volume 57 Pages 185-190
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    We study a degenerate parabolic equation derived from the kinetic theory using Renyi-Tsallis entropy. We have the threshold mass for the blowup of the solution and also the finiteness of type II blowup points. The results are regarded as the threshold blowup mass and also a higher-dimensional version of our previous work on the non-stationary Smoluchowski-Poisson equation associated with the Boltzmann entropy in two-space dimensions, and actually, we use the mass quantization of the blowup family of stationary solutions in the proof.
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  • Yuka YOSHIMATSU, Hiroki TANIGUCHI, Shinji SUZUKI, Rui HIROKAWA, Yohei ...
    2009 Volume 57 Pages 191-198
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    Adaptive flight control systems can accommodate errors due to aerodynamic changes or control surface failures in mid-air. In this paper, a feedback error learning (FEL) approach employing a neural network is considered as an adaptive system. In FEL, the neural network is set parallel to the conventional feedback controller. Through online training, the neural network learns to minimize the conventional feedback controller's output. The result is that it approximates the inverse dynamics of the aircraft and can thus work as a feedforward controller. Flight experiments were conducted with a small unmanned aerial vehicle. Two cases were considered as simulated failures: a trim setting error and a gain scheduling error. Experimental results demonstrated that the neural network can improve the control performance in case of changing aircraft dynamic characteristics, thereby validating the method proposed.
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  • Masatoshi YAGI, Sanae-I. ITOH, Kimitaka ITOH
    2009 Volume 57 Pages 199-205
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    The linear stability of drift tearing mode with neoclassical effect is investigated in the cylindrical geometry. It is found that there is an instability even in the limit of ? <0, if the bootstrap current term exists. The eigen-function shows the tearing-like mode. The transition between two eigen-states is observed. This instability is stabilized by the drift effect and by collisional viscosities. The nonlinear sustainment of neoclassical tearing mode is also investigated in the linearly stable region. We do not find the nonlinear sustainment in our parameters, but the magnetic island simply dumps.
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  • Satoru SUGITA, Masatoshi YAGI, Sanae-I. ITOH, Kimitaka ITOH
    2009 Volume 57 Pages 207-215
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    The 2D Hasegawa-Wakatani-type model equation is introduced to investigate the blob propagation in the scrape-off layer. The effect of the density nonlinearity on the blob propagation is investigated, focusing on the blob size effect. It is found that in the regime with the large blob size where the interchange instability is dominant, the theoretical estimation of the blob propagation velocity agrees well with the simulation results. However, in the regime with small blob size where the Kelvin-Helmholtz instability is dominant, it does not work well. This is because the blob breaks up into pieces in this regime. The center-of-mass velocity is estimated in this regime to understand the characteristic of the blob propagation.
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  • Kazuyoshi KITAZAWA
    2009 Volume 57 Pages 217-225
    Published: February 27, 2009
    Released: September 07, 2009
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    A formula for mass of Standard Model Higgs boson is derived by considering certain asymptotic behavior for singular solution of equation of motion (EOM) of Higgs field via Euler-Lagrange equation, in which MH0 is shown as a rest mass of Higgs boson mass of the field, which maintains Lorentz invariance. Where the asymptotic formula extracts a proper information near the singular solution (vacuum expectation value (vev)) from EOM. By modifying the mass formula to ‘mass triangle’ with H0 production scheme of W/Z-fusion process and by obtaining mass representation at a stationary point, the value of MH0 is determined at 120.611 GeV/c2, which is not excluded by latest experimentally preferred mass, and is consistent with simulation result for vector boson fusion.
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  • Makoto UMEKI
    2009 Volume 57 Pages 227-232
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    We consider the problem of stable stationary configurations in general gradient systems with periodic boundary conditions in two or three spatial dimensions. Such a problem arises in point vortices, classical mechanics of particles, and optimization problems in order to find the minimal state of some functions such as an energy or variables due to distances associated with every pair of two points. First, we show how triangular patterns appear in two-dimensional gradient systems. Then, the system extended into three dimensions is proposed and investigated numerically.Finally, it is shown that triangular patterns appear in the gradient system for the point vortices with the same strength.
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  • Ken SAWADA, Takashi SUZUKI
    2009 Volume 57 Pages 233-239
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    We consider the mean field equation based on Onsager's equilibrium statistical mechanical theory for a point vortex system in a two-dimensional bounded domain, in order to understand the two-dimensional turbulence with large-scale long-lived vorticity structures. We show the rigorous derivation of the mean field equation for the system where each point vortex has a unique circulation value and the point vortex number density on the circulation is determined by a probability measure. We make use of the fact that a limiting canonical measure in the mean field limit is regarded as a solution of the variational problem related to the minimum free energy principle.
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  • Atsunari KATSUKI
    2009 Volume 57 Pages 241-246
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    Crescent sand dunes called barchan are observed in desert and on the surface of the Mars. Barchans interact with each other by collision and form barchan field. We have proposed a dune model reproducing these interactions. This model includes only saltation and avalanche as the basic sand transport processes. We have reproduced a few hundred of barchans in a numerical field and have investigated dynamics of a barchan field. We found that the size distribution of barchans is well fitted by a log-normal distribution.
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  • Susumu KOBAYASHI, Takashi ADACHI, Tateyuki SUZUKI
    2009 Volume 57 Pages 247-255
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    The present study reports the quantitative behavior of the reflected wave over a multi-guttered or a step-like wedge, when the incident shock wave is strong (the incident shock Mach number Mi = 1.915). The experiment analysis revealed that the behavior of the first triple-point differed depending on the wedge inclination angle. Furthermore, the height of the first triple-point is greater for multi-guttered wedges than for step-like wedges. The angle made by the incident and reflected waves decreases more or less sinusoidally toward its corresponding asymptotic value. The behavior on the angles of incidence and reflection plane demonstrates that, although angles of incidence and reflection vary as the incident shock propagates and they do not agree with the three-shock theory, they move toward some asymptotic value on the three-shock theory. These asymptotic values for both wedges and ordinary smooth wedges differ from each other.
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  • Keiichi MURAKAMI, Atsushi HASHIMOTO, Takashi AOYAMA
    2009 Volume 57 Pages 257-262
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    A study to establish a prediction method for acoustic environment during rocket launch has been conducted using a multidisciplinary analysis method of fluid, acoustics, and structure in JAXA. This coupling method consists of following elements: numerical analyses of sound generation, sound propagation, sound transmission to fairing, and sound vibration of a payload. In this paper, a study of sound propagation analysis is reported. Using an Euler flow solver, the following two cases are compared; one is that a lifting-up rocket is modeled quasi-steadily according to rocket ascent, and the other is that a rocket is fixed above a modeled launch pad. The results of these calculations indicate that characteristic frequencies of sound wave observed at a point on flight path are different from each other and that one of the low frequency characteristics of observed sound wave at the observer point is caused by the inner acoustic resonance of a rocket plume duct.
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  • Takahiro NAKANO, Takumi INOUE, Atsuo SUEOKA
    2009 Volume 57 Pages 263-268
    Published: February 27, 2009
    Released: September 07, 2009
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    In order to perform an accurate evaluation of the dynamic response of a vibration system, it is important to estimate not only the linear vibration parameters but also the nonlinear parameters. Nonlinearities are estimated through time-varying vibration parameters, such as instantaneous damping ratio and instantaneous frequency. In the case of a relatively small nonlinearity, this technique is effective. In this paper, a segmental use of the harmonic wavelet is proposed in order to estimate time-varying parameters. The Hilbert transform is usually employed for the purpose of such estimations. However, it has been pointed out that the Hilbert transform yields unacceptable results with numerical instability under certain conditions. The proposed method shows significantly good results with respect to numerical stability as compared with the simple application of the Hilbert transform and a similar use of another wavelet.
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III. HEAT TRANSFER AND FLUID DYNAMICS
  • Taichi MATSUMOTO, Tomoyuki SHIKATA, Teiji TAKIGAWA, Naoto OHMURA
    2009 Volume 57 Pages 271-278
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    The present study investigated flow characteristics of immiscible liquid-liquid two-phase flow in micro channel systems. Two kinds of T-shaped channels of glass fabricated by micro precision machining were used. An aqueous solution of glycerol or distilled water with or without surfactant was used for the aqueous phase, while styrene monomer was used for the organic phase. Four representative flow patterns, i.e. stratified flow, stratified wavy flow, stratified flow with inclined interface and annular flow, were observed due to the difference of channel dimension of the organic-phase flow and physical properties of liquids. The void fraction of stratified flows, including stratified flow with inclined interface, was characterized using the Lockhart-Martinelli method, while the void fraction of annular flow was estimated by an equation proposed by Fujii et al. It was found that the void fraction against Martinelli parameter X can be expressed by a parameter for the roughness between two phases.
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  • Yuki TANIGUCHI
    2009 Volume 57 Pages 279-288
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    We study the barotropic flows in a domain on a rotating sphere with the rigid boundary under a uniform easterly wind, and observe two-gyre flow patterns. This flow can be considered as a localized one-gyre case on the β plane. As wind-forcing increases, an oscillating instability arises from the steady flow of westward intensification via Hopf bifurcation. As wind-forcing is strong, a vortex street occurs from each gyre, while there occurs no vortex street for a two-gyre flow on the β plane. As the size of the fluid field is larger, the number of the north and the south vortex streets increases.
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  • Takehiko SEGAWA, Hiro YOSHIDA, Shinya TAKEKAWA, Timothy JUKES, Kwing-S ...
    2009 Volume 57 Pages 289-296
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    Velocity distributions produced by a dielectric barrier discharge plasma (DBD) actuator with a pair of facing linear electrodes were measured by using a PIV system. DBD plasma was formed near the inner edge of the facing electrodes by applying high voltage between the top and bottom electrodes at radio frequencies. By using two power supplies, tangential jets with different velocity distributions in time and space were induced independently in the vicinity of the wall from both electrodes. Wall-normal jets could be inclined by colliding tangential jets with different speeds. Wall-normal jets that distributed clockwise and counterclockwise vortices could be produced alternately by applying signal packets in different phase to each of the top electrodes. The properties of the functional jets were characterized by PIV analysis.
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  • Norihiko SUGIMOTO, Minh Tuan PHAM, Kanta TACHIBANA, Tomohiro YOSHIKAWA ...
    2009 Volume 57 Pages 297-307
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    We propose a method to evaluate intensities and influential ranges of detected vortex as an extension of high speed method to detect vortex using a streamline with enhanced curvature, which is useful to identify tropical cyclones in huge climatology data. In the proposed method, center of vortex is detected by iteration of streamline from some initial points automatically. This method has high accuracy and low computational cost, because it does not need to check empirical conditions at all grid points, as in the case of conventional method. This paper exemplifies the accuracy of the vortex risk-assessing method using observational climatology data. Results suggest that this method is available for risk-assessment of tropical cyclones under global warming predicted by high resolution models.
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  • Kazuo OEDA
    2009 Volume 57 Pages 309-322
    Published: February 27, 2009
    Released: September 07, 2009
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    We will treat a non-autonomous dynamical system and investigate some long-time behavior of the solution. Our motivation is to study a dynamical system derived from a moving boundary problem. In this case the domain of the generator of the corresponding evolution equation is time-dependent. By this reason, the known theory of the process is not applicable to such a problem. The purpose of the present paper is to extend the notion of the process to be able to apply to above problems. Making use of the extended process, we can study the 2-D Navier-Stokes equation in a given time-dependent region.
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  • Takeshi KATAOKA
    2009 Volume 57 Pages 323-330
    Published: February 27, 2009
    Released: September 07, 2009
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    Time evolution of transversely distorted surface solitary waves is simulated numerically on the basis of the three-dimensional Euler equations. The solitary wave solution whose crest is distorted periodically in the transverse direction is chosen as the initial condition. It is then confirmed that there really exist transversely unstable surface solitary waves that are longitudinally stable. The results also show that, as the wavelength of the disturbance becomes shorter, the transverse instability disappears at some critical wavelength which is determined by the amplitude of the solitary wave.
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  • Takeshi SUGIMOTO
    2009 Volume 57 Pages 331-338
    Published: February 27, 2009
    Released: September 07, 2009
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    Some insist penguins porpoise to save the energy at high speeds. Some believe penguins porpoise to breathe without losing their speed. Others think penguins porpoise to watch predators in the air and on the shore. The present proposal is introduction of equations of motion: a penguin is treated as a particle; the conventional aerodynamics and hydrodynamics is used; added mass is incorporated to capture the effect due to splash; constant power is assumed. As the penguin dashes out of the water, it sprays water around: the added mass in the water is assumed as an impact, whilst the added mass in the air is neglected; no wave resistance is incorporated, because penguins are quite streamlined. Parameters are determined so as to explain the existing field data. The results show the following facts: penguins lose horizontal speed in the air because of inclined flight-trajectory; porpoising consumes more energy than steady-state swimming on the same-speed basis.
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  • Zu peng GU, Ryosuke AKAHORI, Syunsuke IKEDA
    2009 Volume 57 Pages 339-349
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    It is necessary to understand the influence of pile dike on flow in order to control morphological evolution of river banks. The three-dimensional flow around a dike, including the vertical and secondary flow, is particularly important for local sediment transport. This study investigates the three-dimensional structure of flow around dikes in a flume by laboratory experiments.
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  • Masahiro ISHIGAKI, Kazuto KUZUU, Shizuko ADACHI, Katsuya ISHII
    2009 Volume 57 Pages 351-362
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    Taconis oscillation is one of thermoacoustic oscillations. Taconis oscillation in a closed long tube is studied by the numerical simulations of the 2D compressible Navier-Stokes equations. Both end walls of the tube are hot (T = TH ), and the central regions of side walls are cold (T = TC ). The critical temperature ratio by our numerical simulation is higher than theoretical critical temperature ratio in the open-closed tube. The temporal and spatial changes of the temperature in the cold region of the closed tube are stronger than those of the open-closed tube. We examine the validity of the theoretical assumptions for the open-closed tube. The assumption of uniform distribution of the time averaged temperature is not satisfied in the temperature gradient and the cold region of the closed tube.
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IV. NUMERICAL COMPUTATIONS
  • Tatsuhito AIHARA, Hiroyuki KUMANO
    2009 Volume 57 Pages 365-376
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    This paper deals with collision vibration in a continuous system excited by periodic displacement with arbitrary functions. The analytical model is a system of steady collision vibration in simply-supported-beam with an attached mass. The attached mass collides elastically with clamped springs on asymmetrical faces. In order to clarify the main resonance of the system subjected to a displacement excitation, the resulting vibrations are analyzed using the Fourier series method and an exact solution is derived for this system. Following the theoretical analysis, numerical calculations are performed and the resonance curves are constructed using the resulting vibrations. The numerical results reveal the effects of the stiffness of clamped spring, the ratio of attached mass and the amplitude of excitation on the resonance curves. The experiment is also carried out to verify the theoretical result. The numerical result is in a fairly good agreement with the experimental one.
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  • Yosuke KOBAYASHI, Genki YAGAWA
    2009 Volume 57 Pages 377-383
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    The Free Mesh Method (hereinafter referred to as "FMM") has a good compatibility with the parallel computing. But, the conventional FMM has a problem in accuracy. Recently, the Enriched FMM (hereinafter referred to as "EFMM") was proposed by Yagawa et al. This paper describes the parallel EFMM, intending the ultra large scale analysis of 100 million degrees of freedom with high parallel performance. Saving of times is attained by parallel Conjugate Gradient method. A parallel EFMM code is developed on a cluster system.
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  • Takahiro SAITOH, Sohichi HIROSE, Takuo FUKUI
    2009 Volume 57 Pages 385-393
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    This paper presents a new time-domain boundary element method (BEM) in 2-D viscoelastic wave propagation. The conventional time-domain BEM approach cannot be used in general, since it is difficult to obtain closed time-domain fundamental solutions in viscoelastic wave propagation. To overcome the difficulty, in this paper, the convolution quadrature method (CQM) developed by Lubich is applied to 2-D viscoelastic wave propagation. In the proposed method, the convolution integral is numerically approximated by quadrature formulas, whose weights are computed by using the Laplace transform of the fundamental solution in 2-D viscoelastodynamics. In addition, the fast multipole method (FMM) is applied to improve computational efficiency.
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  • Fumio KIKUCHI, Keizo ISHII, Issei OIKAWA
    2009 Volume 57 Pages 395-404
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    As a discontinuous Galerkin FEM, we propose a formulation based on Tong’s hybrid displacement method and the stabilization technique, and develop polygonal elements for linear static plane stress problems.The basic ideas are the introduction of inter-element displacements and the use of stabilization terms. Here we only present polygonal elements with polynomial approximation functions.That is, we employ discontinuous linear polynomial fields for element displacements, while we adopt continuous piecewise linear polynomial fields for inter-element displacements. By static condensation, we can also obtain the usual element stiffness matrices and the element load vectors for nodal inter-element edge displacements, so that our elements can be easily built into various existing FEM codes and even mixed use with conventional elements is possible. We obtain some numerical results to show the validity of our approach and also to see the influence of the stabilization parameter size and the flexibility in element shape.
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  • Kotoba NISHIDA, Hiroshi FUJIWARA, Yuusuke ISO
    2009 Volume 57 Pages 405-410
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    We consider the finite difference method applied to the initial value problem for a first-order system of linear partial differential equations in the class of analytic functions. We show convergence of a scheme and existence of the analytic solution of the original differential equation by finite difference approximation. The concept of convergence is independent of that of stability as Hayakawa3)showed the fact, in 1988, for constant coefficients cases. We deal with a variable coefficients case and develop a theory in which the concept of convergence is independent of that of stability. We give some numerical results with multiple-precision arithmetic.
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  • Shinsuke NAGAOKA, Genki YAGAWA
    2009 Volume 57 Pages 411-420
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    Enriched Free Mesh Method (EFMM) is one of the mesh-less method. EFMM is considered to make large scale analysis easier without the meshing process. Analytical accuracy using EFMM is much better than analytical result of Finite Element Method and Free Mesh Method, because EFMM is a revised version of the Free Mesh Method. However, automatic mesh generation process needs a lot of time yet. Especially, the case of analysis model is complicated. In this paper, we propose new automatic mesh generation algorithm for EFMM that is faster than conventional method. At that time, we use a new boundary treatment. Moreover, we study the application of the EFMM to fracture analysis. Then we use the re-meshing function to obtain a better analytical result. Further, we discuss the accuracy when the stress intensity factor are computed using the stress method, which is a type of a direct method.
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  • Tetsuya TAKEMI
    2009 Volume 57 Pages 421-428
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    The land of Japan is characterized by complex and steep terrains, which influence locally heavy rainfall and severe wind. Due to high variability of wind speed, gusty winds are significantly affected by small-scale terrains. Thus, it is important to understand the effects of complex and steep terrains on the development of wind gusts in addition to the understanding of the physical processes of microscale meteorological phenomena such as tornadoes and downbursts. This study investigates the variability of severe local winds by conducting high-resolution numerical simulations that incorporate the 50-m mesh digital elevation map of the Geographical Survey Institute of Japan. By resolving small-scale terrain features, it is shown that the high-resolution simulations can represent the short-term and small-scale variability of surface winds.
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  • Shinsuke TOKUNAGA, Masatoshi YAGI, Sanae-I. ITOH, Kimitaka ITOH
    2009 Volume 57 Pages 429-436
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    The collapse mechanism of internal transport barrier in reversed magnetic shear configuration is investigated using multi-scale global simulation code for ion temperature gradient driven drift wave turbulence with a heat source term. In the simulation, the transport remains at the neoclassical level around the q-minimum region, on the other hand, far from q-minimum region the turbulence develops. As the result, a kind of internal transport barrier is observed. A meso-scale mode plays essential role for the decay of the transport barrier. The energy source channels supplying energy to the meso-scale mode are analyzed. It is confirmed that such mode is excited via three-wave coupling initially. After that, the contribution from the quasi-linear channel increases gradually. The modification of the temperature profile gives rise to the excitation of the ion temperature gradient driven mode at the outside edge of the transport barrier and it triggers the collapse.
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  • Yoshinobu INADA, Hikaru AONO, Hao LIU, Takashi AOYAMA
    2009 Volume 57 Pages 437-447
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    Insect flapping sound is a consequence of flow disturbance generated by flapping wing motion; spatial and temporal changes of pressures on wing surface and vortex structures generated by wing motion are considerable sources of flapping sound. To uncover such sound generation mechanisms in flapping wings, we have developed a hybrid method combining CFD techniques and acoustic analysis. Unsteady flows around a hovering insect ‘flying’ with realistic wing kinematics are computed with a multi-blocked, overset grid NS solver. Acoustic analyses of monopole and dipole sound sources are undertaken using Ffowcs-Williams and Hawkings (FW-H) method. Numerical analyses are carried out for three typical insects (hawkmoth, honeybee, and fruitfly). CFD analysis offers detailed vortex aspects and induced pressure distributions on the wing surfaces showing concrete evidence of sound sources; acoustic analysis clarifies characteristics of the induced flapping sounds, including sound direction and its spectrum distributions.
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  • Ryosuke AKAHORI, Mark SCHMEECKLE, Syunsuke IKEDA
    2009 Volume 57 Pages 449-460
    Published: February 27, 2009
    Released: September 07, 2009
    JOURNALS FREE ACCESS
    A particle-based method for numerical calculation of suspended sediment transport is presented. In the proposed method, particle trajectories are calculated depending on the combination of the deterministic force represented by the mean velocity components, settling velocity of the particles, and the random force that represents small-scale fluctuations by turbulent motions.
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