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Yoshinori SANO
Article type: Article
Session ID: 401
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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Passive-scalar fields in two-dimensional homogeneous isotropic turbulence with several Prandtle numbers (Pr) were investigated by means of the direct numerical simulation (DNS). In the time development, the thermal intensity was rapidly decreased at the low Pr. The thermal intensity spectra obey the power laws of k^<-1.4>, k^<-2> and k^<-5.9> in Pr=5, 1, 0.05 respectively. In the contour of the thermal dissipation rate, the remarkable increase of line structures was observed when Pr was high. In the multi-fractal analysis, we found the strong intermittency at high Prandtle number.
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Masayoshi OKAMOTO, Nobuyuki SHIMA
Article type: Article
Session ID: 402
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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Turbulent flows through concentric annuli with the oscillating inner-wall around the axis were investigated by means of direct numerical simulation (DNS). In the inner-wall oscillation with the small oscillating period, the drag reduction occurs and the flow is stabilized like the outer-wall oscillation case, while in the inner-wall oscillation with the large one, the flow becomes unstable. The variation of the phase mean quantities is strongly dependent on the magnitude of the oscillating period.
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Kaoru FUKASAWA, Masatoshi SANO
Article type: Article
Session ID: 403
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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Experiments have been performed on turbulent channel flow with suction through a slit. The inclined angle of the suction is changed 30°, 60°and 90°at the main stream velocity 10m/s. The dimensionless suction flow ratio is varied nine steps in the range of 0.067〜0.500. Difference due to the inclined angle is not observed in the result of wall pressure and heat transfer coefficient. Increasing the suction flow ratio, the heat transfer coefficient decreases. The recovery mechanism of turbulence is greatly different between the lower side and upper side of the channel.
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Yoshiyuki Tsuji, Kei Miyachi, Ikuo Nakamura
Article type: Article
Session ID: 404
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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The logarithmic velocity region is studied in zero-pressura-gradient turbulent boundary layers on the rough wall. We have already proposed the definition of log-law region in the case of smooth wall with using the probability density of velocity fluctuation. In this report this idea is expanded into the rough wall boundary layers, and extracted log-law region is discussed from the point of PDF profiles, and also its Reynolds number dependence is studied based on the experimental data.
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Shigehira OZONO, Tadateru MATSUO, Hiromori MIYAGI
Article type: Article
Session ID: 405
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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The purpose of the present study is to effectively produce isotropic high-Reynplds-number turbulence using a wind tunnel of multi-fan type. For the modes mainly examined, the fans are divided into two sets in a checkerboard pattern. Blowing and suction are provided to the respective sets of fans with a single sinusoidal component. The suction causes a maximum intensity at the inlet of the test section. Without phase shift, however, natural mixing is not enhanced. A relatively high turbulence Reynolds number has been achieved for a driving mode within a practically small distance.
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Atushi KOSUGI, Hideharu MAKITA
Article type: Article
Session ID: 406
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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A wind tunnel experiment was conducted on turbulent particle diffusion from a continuous point source in several kinds of turbulence fields. The features of concentration fluctuation of the particle diffusion were detected for grid turbulence with R_λ=36 and large-scale turbulence with R_λ=410 excited by an active turbulence generator. Turbulence characteristics were measured by a hot-wire system and a LDV system was used to obtain particle pedestal signals. To analyze the concentration fluctuation fields, time series signals of concentration were translated from discrete pedestal signals of the particles passing through a control volume of the laser beam. The present experiments clarified the concentration fluctuation characteristics for two typical types of the turbulent particle diffusion, i.e., far field diffusion in the small-scale turbulence and near field diffusion in the large-scale turbulence under the effect of the plume's meandering motion.
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Yuka Ishigami, Qinyin Fan
Article type: Article
Session ID: 419
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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As a fundamental consideration in natural convection, the flow in a vertical slot has been studied by numerical analyses with the finite element method and experimental investigations. This paper presents a simulation of natural convection in a vertical slot using a two dimensional model with the finite volume method. Regardless of very high Ra number (5×10^5), the numerical analysis results agree with the experimental data very well. In addition, this paper clarifies about the accuracy of the prism elements and hexahedra elements, and the semi-steady phenomenon.
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Kei ITO, Takaaki SAKAI
Article type: Article
Session ID: 420
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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Bathtub vortices, which have free surface dents (gas cores), are of concern in design studies on fast breeder reactors (FBRs) because of their potential causes of gas entrainments. Authors have conducted numerical simulations for the bathtub vortices to establish a prediction method for the onset of the gas entrainment and showed that the numerical simulations can roughly reproduce the structures of the bathtub vortices in the steady state. As an extension of the previous simulations, two unsteady behaviors were simulated to validate the applicability of the numerical simulations for the unsteady behaviors of the bathtub vortices in this research. As a result, the numerical simulations could reproduce the same oscillation of the gas core surface with experimental result when the perturbation was applied to the vortex flow. The oscillation was considered theoretically to deduce that the cause of the oscillation was the Kelvin-Helmholtz instability. In addition, the bubble entrainment from the tip of the gas core also could be calculated. These results showed that the numerical simulations are applicable to the unsteady behaviors of die bathtub vortices.
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N. Takahashi, T. Takahashi, T. Miyazaki
Article type: Article
Session ID: 421
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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The interaction between a columnar vortex and external turbulence is investigated numerically. The q-vortex is immersed in an initially isotropic homogeneous turbulence field, which itself is produced numerically by a direct numerical simulation of decaying turbulence. The formation of turbulent eddies around the columnar vortex and the vortex-core deformations are studied in detail by visualizing the flow field. In the less-stable case with q=-1.5, small thin spiral structure is formed inside the vortex core. In the unstable case with q=-0.45, the linear unstable modes grows until the columnar vortex make one turn. Its growth rate agrees with that of the linear analysis[1]. After the vortex made two turns, the secondary instability is excited. It caused that the columnar g-vortex collapses and many fine scale vortices appear abruptly.
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Kuniharu FUJIBAYASHI, Mamoru TANAHASHI, Toshio MIYAUCHI
Article type: Article
Session ID: 422
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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To investigate the statistics of the clusters of coherent fine scale eddies, direct numerical simulation database of homogeneous isotropic turbulence up to Re_λ=256.1 have been analyzed. The cluster of the strong coherent fine scale eddies tends to exist in the region with high local turbulent kinetic energy, which is defined as local average in the cube of integral length scale, and with high strain rate in large scales. Even in the Kolmogorov length unit, the most expected diameter of the coherent fine scale eddies depend on the characteristics of the integral length box. The diameter in each integral length boxes can be scaled by the local Kolmogorov scale (ηl). The most expected diameter is about 10_<ηl>. These characteristics of coherent fine scale eddies are similar to those in the near-wall turbulence. Moreover, the large scale eddies tend to exist in the region around the cluster where the energy transfer from GS to SGS is strong.
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[in Japanese], [in Japanese]
Article type: Article
Session ID: 423
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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Unstable periodic motions are educed by solving the Navier-Stokes equation numerically by use of Newton-Raphson iteration for Couette turbulence. It reproduces the instantaneous structures as well as the statistical characteristics of turbulence. This suggests that the turbulent state may approach frequently these periodic motions. Thus it is regarded as the fundamental spatio-temporal coherent structures or the skeleton of turbulence. In this study, we identify vortical structures by making use of sectional swirl and pressure minimum scheme to understand those dynamics in periodic motion for plane Couette turbulence. Moreover, we examine how passive particles and lines are advected and mixed in this system.
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Ayumu INASAWA, Seiichiro IZAWA, Ao-kui XIONG, Yu FUKUNISHI
Article type: Article
Session ID: 424
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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The spanwise interface between laminar and turbulent regions is experimentally investigated. The interface is detected by a rake of single hotwire probes and then its structure is measured in detail using a X-type probe. Output signals of these probes are analyzed by a conditional sampling technique together with an ensemble-averaged method. As a result, it is found that the turbulent region always starts to stick out into the laminar region at the middle height of the boundary layer, where a pair of longitudinal vortices aligned in the wall-normal direction induces the flow from turbulent to laminar regions. The expansion of the turbulent region is successfully suppressed by destroying these vortical structures using a thin plate.
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Takatsugu KAMEDA, Shinsuke MOCHIZUKI, Hideo OSAKA
Article type: Article
Session ID: 425
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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Measurements have been performed in the vicinity of the roughness element for the equilibrium boundary layer developing over the rough wall, proposed by J.C. Rotta. Pressure and velocity distributions were measured in the range of the a roughness pitch length between roughness elements at x≒2180 and 2800mm. Pressure drag coefficient is almost constant to roughness Reynolds number k^+. Mean velocity profiles have an inflectional point at y_T/k≒0 and reverse flow exists for y_T/k<0. Then, in the cavity larger eddy having a scale of cavity width was confirmed from the flow pattern described with mean streamline. The frequency f of the reverse flow is proportional to u_τ/b.
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Atsushi UEHARA, Hiroshi MAEKAWA, Daisuke WATANABE
Article type: Article
Session ID: 426
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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The three-dimensional time dependent compressible Navier-Stokes equations are numerically solved to study transition mechanism in transonic and supersonic channel flows at Mach numbers of 0.75 and 2, respectively. High-order compact schemes of 5th order are used for spatial derivatives and a 4th order Runge-Kutta scheme is employed for time advancement. The inlet flow of the channel is forced randomly. The results show that the transonic flow becomes turbulent sooner than the supersonic flow. The numerical results provide new physical insights into generation mechanisms of three-dimensional structures near the walls and development of the turbulent spot.
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Yuta KAWAI, YOSHIYUKI Tsuji, Yutaka KUKITA
Article type: Article
Session ID: 427
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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The flow field with an edgetone phenomenon induced by interaction between a two dimensional jet and a flat plate was experimentally explored by applying phase averaging technique and triple decomposition analysis. We define a coherent structure as the region where the absolute phase averaging periodic vorticity is larger than 0.15. The coherent structure formed at nozzle exit develops into downstream and then impinges on a tip of the flat plate. Addressing on Reynolds stress term and turbulent energy production term, we consider the role of coherent structure in the process of momentum and energy transport. The periodic Reynolds stress and production have a large value at same place where the coherent structure passes through. Based on this result, we assume that the rotation of coherent structure transports momentum. This process may increase the production term of periodic component.
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Ye LI, Naohiko KASAKI, Takaki NAKAMURA, Takahide NOUZAWA
Article type: Article
Session ID: 428
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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The mechanism of aerodynamic noise generated by vortices interaction was investigated applying experiment and numerical simulation. The study focuses on the aerodynamic noise generated near side window of production automobile. In simulation, the flow filed was firstly analyzed by Finite Differential Method (FDM) with 3^<rd>-order upwind scheme, then Powell's acoustic analogy was applied to evaluate the acoustic source. Furthermore, the velocity fluctuation and acoustic source were clarified by the use of experiment. It is found that the interaction between vortices separated from front-pillar and door-mirror results in the instability of boundary layer, which induces the aerodynamic noise near side window. By optimizing the relative location between front-pillar and door-mirror, the boundary layer instability can be inhibited, and then the noise is reduced.
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Mizuyasu KOIDE, Tsutomu TAKAHASHI, Masataka SHIRAKASHI
Article type: Article
Session ID: 429
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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In the previous works, the present authors showed that two types of longitudinal vortex shed periodically from a crisscross cylinder system composed of two 26mm diameter circular cylinders based on hot wire anemometry in a wind tunnel with 320mm square cross section together with visualization in a low velocity water tunnel with 200mm square cross section. The specific aim of this work is to confirm universality of this phenomenon by carrying out experiments with larger cylinder diameters and a high-velocity water tunnel. These experiments show that the longitudinal vortex sheds from systems with d=10〜127mm, i.e. the trailing vortex sheds when gap-to-diameter ratio s/d is from 0 to 0.25 and the necklace vortex sheds when s/d is from 0.25 to 0.5. The relationship between Strouhal number for their shedding frequency and Reynolds number is consistent qualitatively with me previous research works regardless of experimental conditions.
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Shinsuke MOCHIZUKI, Kazumi SUZUKAWA, Keisuke SAGA, Hideo OSAKA
Article type: Article
Session ID: 430
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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Complex turbulence field around a flat paddle impeller in a stirred vessel was investigated experimentally with LDA measurement and phase averaging analysis. The relative mean velocity filed against the flat paddle was obtained and detailed examination was made on the production mechanism of Reynolds shear stress. Containing inflexion point, the relative velocity profile in downstream direction evolves like separated shear layer. Reynolds shear stress profile has a large peak, however, the location unnecessary coincides that of the maximum mean velocity gradient. There is the case that the large Reynolds shear stress occurs around boundary between inflow and outflow behind the edge of flat paddle. It is expected that quasi-periodic inflow and outflow contribute Reynolds shear stress production.
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Masaki FUCHIWAKI, Ryo TOMII, Kazuhiro TANAKA
Article type: Article
Session ID: 431
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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Many studies on unsteady flow around an unsteady airfoil, such as a pitching airfoil and a heaving airfoil, at low Reynolds number region have been carried out with experimental and numerical approaches and vortex flow patterns and dynamic thrust of them have been reported. However, the flow field around an unsteady airfoil in pitching and heaving motions has not been understood. We have carried out PIV measurement behind an unsteady airfoil in pitching and heaving motions at low Reynolds number region, Re=4000. The thrust producing vortex street was formed behind an unsteady airfoil at low non-dimensional trailing edge velocity and low non-dimensional heaving velocity. Moreover, it was found that the thrust producing vortex street was formed by vortices of strong vorticity at ψ=π/2 and 3π/2. However, large vortex rolled up from the leading edge at ψ=π/2 and 3π/2.
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Nobumasa SEKISHITA, Hideharu MAKITA
Article type: Article
Session ID: 432
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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Vortex structures were investigated in a round buoyant jet by smoke-wire visualization and hotwire measurement. Heated air of 53℃ was ejected from a round exhaust of D=83mm. At the exhaust, mean velocity distribution was tophat-type and its mean velocity, U_0, was 2m/s. Ring vortex structures were generated around the exhaust in the buoyant jet. Unlike the usual case of an unheated jet, large vortex structures generated by the vortex pairing of the ring vortices weren't observed. The heated air rose meandering in the potential core. As a result, the buoyant jet became to be turbulent in 2〜3D times downstream from the exhaust. The behavior of the coherent vortices of the buoyant jet was apparently different from the unheated jet.
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Koji MATSUBARA, Hiroyoshi MARUSHIMA, Hitoshi SUTO, Makoto YAMAZAKI, Mu ...
Article type: Article
Session ID: 433
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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Large eddy simulation was performed for a turbulent jet of diluted hydrogen. Treated were the case where hydrogen reacts with surrounded oxygen and the case where only mixing occurs without reaction. Coherent structures of turbulence in these cases were investigated. In reacting case, temperature rise causes significant drop of flow density, and, thus, velocity is two times as higher as the counterpart at the same position of non-reacting case. In spite of dramatic change in order of velocity magnitude, there is close similarity between two-point correlation of reacting case and that of non-reacting case. In two cases, coherent structure inclined against jet central axis was suggested through distribution of two point correlation.
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Osamu NAKAKOBARU, Keisuke SHUTO, Yosuke NISHIDA, Hiroyuki TAKAHIRA
Article type: Article
Session ID: 434
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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We tested two kinds of piezoelectric ceramics for small focusing ultrasonic generators. The radius of curvature of the ceramics are 8mm and 5.77mm. We measured acoustic pressure near the focus and visualized the ultrasonic field with the schlieren method. We investigated the effect of the radius of curvature on the focusing of ultrasonic wave. The result showed that better focusing is accomplished in the generator with the large radius of curvature. The experiments were simulated numerically using the finite difference method. The simulations showed the oscillating state of the edge of the ceramics affects the focusing of the ultrasonic wave.
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Junichi SUDO, Hitoshi ISHIKAWA, Takafumi SETO
Article type: Article
Session ID: 435
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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An ion flow is the flow which contains ions or micro charged particles. Differential Ion Mobility Analyzer (DIMA) is an analytic instrument of the nanometer-scale chemical pollutants, and its accuracy is influenced by an electric field, fluid drag, Brownian motion, and turbulence. In this research, numerical simulation of ion flow in electric field was performed. The trajectory of ion was calculated by Lagrangian method in consideration of the influence of electric field, fluid drag, and turbulence.
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Kazushige YOSHIDA, Yutaka WAKAI, Shinichi TAKAYAMA, Katsumi AOKI
Article type: Article
Session ID: 436
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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This paper describes an experimental study on the flow patterns and the characteristic of flow around a circular cylinder with grooves. The surface pressure when changing Reynolds number (Re=0.4×10^5〜4.2×10^5) measured with the cylinder with grooves of three kinds of grooves number (32, 48, 64) Drag coefficient is calculated from the pressure distribution and the flow around the cylinder with grooves is investigated by hot wire and visualization. From the results, It is clarified that minimum drag coefficient shifts to high Reynolds number side as groove number increases. It turns out that wake area, separation point change and the drag coefficient is affected with the number of grooves
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Tatsuhiko ARAHATA, Makoto TSUBOKURA, Shigeaki KURODA, Binghu PIAO, Nao ...
Article type: Article
Session ID: 437
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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In this paper, flows around a square array of nine cylinders are investigated. The pressures on the surface of cylinders are measured by experiment of the wind tunnel. The effects of distance between neighboring cylinders on pressure distribution are investigated and several flow patterns are found. Some numerical results are obtained from computational simulation and compared with the experimental ones.
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Masami SUZUKI
Article type: Article
Session ID: 438
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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The method for analyzing a floating type of wave energy conversion device moored on the water surface is described under the condition that the linear water wave theory is applicable. The method is proposed in order to calculate the device characteristics of an air chamber. It derives the particular solution that satisfies the boundary condition on the free surface in the air chamber and on the bottom of the floating device. It is confirmed that the solution gives good agreement with experimental data.
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Yoshinao TAKAHASHI, Fumio TAKASE, Tomoaki NAKAO, Shinichi SUGAHARA, Ma ...
Article type: Article
Session ID: 439
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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These papers (Part1〜3) describe fire behavior in a compartment with activation of fire suppression system. At present the knowledge about it is low. Therefore we experimented by using full scale compartment with it. And we got results about vertical temperature distribution, heat release rate, heat flux and the properties of smoke and heat air current. Then we will make a reduction model of heat release rate and a calculation model of smoke and heat air current in fire time using them. If we contain offect of fire suppression system in fire safety design, building design will be free.
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Tomoaki NAKAO, Yoshinao TAKAHASHI, Fumio TAKASE, Shinichi SUGAHARA, Ma ...
Article type: Article
Session ID: 440
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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This paper describes that the experiment result and consideration about the relation between heat release rate (Q) under the fire situation with an activation of fire suppression system, and temperature, the influence on heat flux and radiant heat, the comparison between the experiment value and the value by a simple calculation of radiant heat, and the relation of heat flux and circumference temperature. Moreover, this paper is compared for the difference of the fire controlling effect of the sprinkler and the water-mist. And, we tried to propose the decrease coefficient by sprinkling to the designed simple numeration concerning the radiant heat.
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Fumio TAKASE, Yoshinao TAKAHASHI, Tomoaki NAKAO, Shinichi SUGAHARA, Ma ...
Article type: Article
Session ID: 441
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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It is a current state in fire behavior when a fire occurs in the compartment where the fire discharge equipment is set up that there are still a lot of uncertain points. There is a possibility to influence the fire fighting activity and the shelter action by formation smoke layer being stirred in the compartment when the fire discharge equipment operates by a fire in such a compartment. Then, smoke and fire plume behavior that flow out from the compartment opening to the passage when the fire discharge equipment operates are clarified.
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Shinichiro NAGANO, Tatsuo MASUTA, Yoshihiko HAYASHI, Kazuhiro Hirasawa
Article type: Article
Session ID: 442
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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This paper is tried the reproduction of city fire at Kanazawa in Edo-period by physically based city fire simulation. The old wooden houses called Machiya along the main road were burned out like a fuse along the main road. The lower-level samurai houses called Ashigaru-yashiki were burned out the same as Machiya. On the contrary, the high-level samurai houses called Buke-yashiki were difficult to burn out on account for the larger premises compared with Machiya and Ashigaru-yashiki. The case study results were shown from condition of city fire after 15 minutes occurrence of a fire to that after 360 minutes.
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Hideyuki KOJIMA, Masato OTSUKI, Hitoshi KURIOKA, Nobuyoshi KAWABATA, M ...
Article type: Article
Session ID: 443
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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A variety of studies regarding the properties of the fire plume in the crosswind were reported from the viewpoint of the spreading prevention in the town area and in the tunnel. When fire experiments are done to understand the structure of a minute flow of the fire plume in the crosswind, it is difficult to examine the properties of the fire plume strictly because of various restrictions. It was analyzed to understand the properties of the fire plume with CFD technique and could be reproduced counter-vortex-pair (CVP) in high temperature area and wall-vortex along the floor. And the properties of two kinds of whirlpool were examined and the relation between them was considered.
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Kazuhiro Hirasawa, Yoshihiko Hayashi, Iwao Suetomi
Article type: Article
Session ID: 444
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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The project, Special Project For Earthquake Disaster Mitigation in Urban Areas, is intended to lessen the damage caused by an earthquake in Urban Areas. Development of Integrated Earthquake Disaster Simulation System (IDSS) is one of the project. This paper is reported about the concept of IDSS and implemented bult-in of BRI & NILIM City Fire Simulation Model.
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Yoshifumi OHMIYA, Jun-ichi SUZUKI, Yoshinao TAKAHASHI
Article type: Article
Session ID: 445
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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It is very important to consider and plan the fire safety design of building components exposed to fire. Especially, the public often believe that timber buildings are unsafe in fires, because wood burns readily. This paper was focused on control of temperature rise within wooden elements during fire to limit the fire collapse risk of timber buildings. First of all, the incident heat flux to surface of steel specimen from a radiation panel was investigated. Next, the control effect of charring rates within wooden specimen by using the sprinkler system was examined. As a result, thickness and velocity of water film, charring rates under the condition that the surface of wooden specimen was covered with water film and so on were clarified.
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Masato OTSUKI, Hideaki MASUDA, Hideki Uesugi, Osami SUGAWA
Article type: Article
Session ID: 446
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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A Numerical simulation of car fire in the prefab parking is performed and compared with the results of full scale experiment. The car fire is simulated by LES combustion model based on mixture fraction. Fire spreading between cars is not simulated but the ignition time and the history of heat release rate is assumed for each cars. For the structural safety, surface temperature of beams during fire is important. The predicted time history of beam surface temperature by CFD shows good agreement with measured data.
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Shinichiro NAGANO, Yoshihiko HAYASHI, Mina NAKANO, Kenji ABURANO, Tosh ...
Article type: Article
Session ID: 447
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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The countercurrent often occur at smoke protect opening on the pressure type smoke extraction system. This paper is reported the occurrence condition of countercurrent and the result used punched panel on supply opening to countercurrent measures. The measurement results are compared with the simulation results. The measurement results are similar to the simulation results except the airflow field upper smoke protect opening. In case of supply opening position at the middle of wall and the under of wall against the smoke protect opening, the countercurrent occur upper the smoke protect opening. The experiment used punched panel is not able to prevent the countercurrent. On the contrary, the simulation result shows the condition of non-countercurrent.
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Takakazu SENGOKU, Nobuyoshi KAWABATA, Daisuke IKEJIMA
Article type: Article
Session ID: 448
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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The quantity of exhaust heat flow from a natural ventilation opening installed at the tunnel ceiling is examined by fire experiments by the model tunnel. As a result, It is clarified that the exhaust heat flow is depe nded on the thermal fume temperature just before the ventilation opening, and the non-dimensional exhaust heat flow is proportional to the 5/3th power of ratio of non-dimensional thermal flow and Froude number. It is confirmed that the simulation result by LES is corresponding to experiment result well. The exhaust heat flow is influenced by the aspect ratio of exhaust opening and the exhaust performance of the shape extend ed in the direction of width is high er.
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Nobuyoshi KAWABATA, Yoshikazu SARUKI, Naoyuki SHIMIZU
Article type: Article
Session ID: 449
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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The purpose of this research is to examine the evacuation environments of passengers at a tunnel fire accident. The visibility of testees entered in the model tunnel on a fire, are investigated by the questionnaire. As a result, the following was clarified. It is thought that it is possible to evacuate to the first stage of a fire under stratified thermal smoke layer. However, it is thought that most testees cannot evacuate when smoke is filled around testees and the density of smoke Cs becomes about 0.3(l/m). Lighting equipments at the tunnel ceiling are not working at a fire.
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Tomoki KIKUMOTO, Nobuyoshi KAWABATA, Masahisa YAMADA
Article type: Article
Session ID: 450
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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This study is an examination of the safety in case of a fire in the small cross sectional tunnel. We examined the influence that the height of the tunnel and the heat release rate give to the movement of smoke and the distance of smoke descent by means of 3-dimensional simulation. As a result, the thickness of thermal plume becomes thick in the tunnel with the ceiling higher, but the space under the thermal plume becomes large compared with the tunnel with the ceiling lower. And the distance of smoke descent becomes short in the case of the tunnel with the ceiling lower. Furthermore, it became clear that smoke is filled easily in the vicinity of the road in the small cross sectional tunnel.
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Jun-ichi SUZUKI, Hiroyuki SUZKI, Yoshifumi OHMIYA, Takao WAKAMATSU
Article type: Article
Session ID: 451
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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A series of structural analysis during fire is conducted in this paper. The purposes of the analysis are a clarification of the relation between performance of fire resistance and earthquake resistance, a quantification of redundancy for structural steel frames exposed compartment fire. The temperature at ultimate state of a steel frame during fire is not always equivalent to the one at a local failure such as column backing taking place. On the condition that neighboring members possess an enough bearing capacity, the temperature of failure is leaded to higher ultimate temperature owing to stress redistribution. Steel frame designed for larger seismic load has much redundancy against vertical load capacity.
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Article type: Appendix
Pages
App4-
Published: September 18, 2005
Released on J-STAGE: August 01, 2017
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