著者

溝田 武人 山本 和幸 大屋 裕二 岡島 厚

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2007, 2007-08-06

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Less spinning soccer ball aerodynamics is studied by wind tunnel experiments. Aerodynamic forces as unsteady lift and side force acting on the ball at rest are measured and estimated flight trajectory. Well agreements of flight shift magnitude in lateral direction between observed and calculated ones are obtained. As a result, in this stage the cause of this strange behavior of less spinning soccer ball is clarified by phenomenon of irregular behaviors of horseshoe-shaped vortex and longitudinal twin one, which already discovered with supper critical Re number region of smooth sphere by Taneda (1976).

著者

菊地,章太

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集

巻号頁・発行日

vol.2009, 2009-09-02

著者

加藤,一彦

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集

巻号頁・発行日

vol.2002, 2002-07-23

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We propose the new PIV image processing method to apply to the cavitation flow field. Two CCD cameras take each image shots of good quality utilizing the difference of the scatter light intensity between the seeding particles and the bubbles. From the image of the seeding particles, the cavitation aspect information such as the void fraction and the cavity boundary is obtained by using the binary process of the light intensity. From both images of the seeding particles and the bubbles, two velocity informations are obtained individually inside or outside area of the cavity by using the cross correlation method and composed into one. For the evaluation of this PIV measurement and processing, the experiment was carried out about the wake vortex cavitation flow behind a wedge. And also, the cavity area and the void fraction map, the vector map and the vorticity map were discussed in detail

著者

加藤 一彦 高阿田 勉 加村 亮子 小原 弘道 松平 晏明

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集

巻号頁・発行日

vol.2002, pp.316-317, 2002

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We propose the new PIV image processing method to apply to the cavitation flow field. Two CCD cameras take each image shots of good quality utilizing the difference of the scatter light intensity between the seeding particles and the bubbles. From the image of the seeding particles, the cavitation aspect information such as the void fraction and the cavity boundary is obtained by using the binary process of the light intensity. From both images of the seeding particles and the bubbles, two velocity informations are obtained individually inside or outside area of the cavity by using the cross correlation method and composed into one. For the evaluation of this PIV measurement and processing, the experiment was carried out about the wake vortex cavitation flow behind a wedge. And also, the cavity area and the void fraction map, the vector map and the vorticity map were discussed in detail

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2002, pp.58-59, 2002-07-23

著者

杉本 憲彦 ファン ミントゥン 橘 完太 吉川 大弘 古橋 武 水田 亮

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2008, 2008-09-04

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We propose a 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, contrary to the case of conventional method. We also extend the method to evaluate intensities and influential ranges of detected vortex. The accuracy of the method is checked using observational and climate model data. Results suggest that this method is applicable to risk-assessment of tropical cyclones under global warming simulated by high resolution models.

著者

伊藤 慎一郎 三谷 曜子 佐藤 克文 内藤 靖彦

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2006, 2006-09-05

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The authors found that bodies of seals had natural oscillation in pitching and rolling motions in drift dive phase by data loggers. The phenomenon is periodically oscillated at a low frequency not by flippering movement. Model experiments were performed in a circulating water channel and in a wind tunnel. The result shows clearly that the oscillatory motion of the bodies of seals during the drift dive was caused by flow induced vibration.

著者

森 信人 Janssen Peter A.E.M. 川口 浩二 永井 紀彦

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集

巻号頁・発行日

vol.2007, 2007

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Quasi-resonant four-wave interactions may influence the statistical properties of deep water surface gravity waves such as a freak wave. The freak wave prediction method developed by Mori and Janssen (2006) based on the quasiresonant wave theory is compared with Europian Centre for Meidum Range Weather Forecasts wave analysis data. Mori and Janssen (2006) model shows low correlation of kurtosis with the observed wave data, although the observeda data show the significant correlation between H_<max> and kurtosis.

著者

坂尾 富士彦

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2000, pp.229-230, 2000-07-25

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A circular tube is set parallel in a circular jet flow, of the same diameter, generates sound by a feedback oscillation. The feedback loop consists from sound generation at the edge, excitation of shear layer voltex fluctuation at the nozzle exit by the sound. When the edge of the tube is cut oblique, the resulting sound is observed to reduce itself considerably. The presence of acoustic resonance gives big difference in the generated sound.

著者

松田 淳 谷藤 鉄也 和才 克己 河村 政昭 安部 隆士

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集

巻号頁・発行日

vol.2007, 2007

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For the investigation of the electro-magnetic heat shield technique, the shock tube was operated as an expansion tube. By using this facility, interaction phenomena between the applied magnetic field and weakly ionized plasma was experimentally investigated by the flow visualization. The test flow velocity is conjectured to be 8km/s from the theory, when the propagation velocity of the primary shock wave is 10km/s at 0.1torr of ambient pressure. In that condition, the shock stand-off distance indicated by the self radiation region generated ahead of the test model was compared between the cases with and without the applied magnetic field. As a result, by applying the magnetic field, it is suggested that the shock stand-off distance could be larger.

著者

郡司 博史 酒井 敏

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集

巻号頁・発行日

vol.2002, pp.92-93, 2002

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A milk crown is a very attractive phenomenon. However, it is very difficult to catch a continuous picture. Therefore, there is almost no systematic research. Then, with the digital Video Camera, we took the continuous image and analyzed them. The parameters of the experiment are the velocity of the waterdrops which collides with a thin liquid layer, the depth of a liquid layer, and the viscosity of fluid of the experiment. Surprisingly, we found that crown-like structure at about 10ms to 30ms after the collision of waterdrop expand at the same speed unrelated to the parameters.

著者

皆川 佑介 小尾 晋之介 益田 重明

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集

巻号頁・発行日

vol.2002, pp.390-391, 2002

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An experimental study has been conducted for a round jet impinging perpendicularly onto a rotating disk. The mean velocity and turbulence statistics are measured by a single component LDV. The jet is issued from a pipe, in which the fully developed turbulent flow is ensured. The disk is set 5 diameters from the pipe exit. The Reynolds number based on the bulk velocity and the pipe diameter is set constant at 1.4E4 while the rotation speed of the disk has been varied between 0 and 1,500rpm. The velocity components in radial and circumferential directions are measured at some selected radial locations. The effect of the disk rotation has not become remarkable until the rotating speed of the disk reaches certain value, which has been indicated by the reduction of the half-width of wall-jet and the increase in the maximum radial mean velocity. The changes in the circumferential velocity component and in the turbulence statistics are fond to be marginal.

著者

佐藤,和雄

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集

巻号頁・発行日

vol.2002, 2002-07-23

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Force measurement test of a standard model HB-2 was conducted at the high enthalpy shock tunnel HIEST. The result obtained at lowest enthalpy condition, in which real gas effect is supposed to be negligible, was compared with the blowdown type hypersonic wind tunnel HWT1 and a good agreement was obtained at zero angle of attack. Real gas effect was also studied by changing stagnation enthalpy up to 11MJ/kg and the significant decrease in axial force with increase in stagnation enthalpy was observed.

著者

横田,祥

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集

巻号頁・発行日

vol.2010, 2010-09-09

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In the terrestrial and planetary atmospheres, vortices that exhibit a polygonal shape are occasionally observed even when the external conditions are nearly axisymmetric. Similar phenomena are also found in laboratory experiments in which water layer in a right cylindrical tank is driven by a rapidly-rotating bottom disk. In this study, we have studied these phenomena by means of laboratory experiments and a linear stability theory. It is found that the characteristics of the vortices in the laboratory experiments are well explained by those of the fastest growing waves caused by a horizontal shear instability of the basic flow. Thus, the polygons observed in the laboratory experiments are likely to be caused by a shear instability.

著者

森脇 亮 石井 宏明 神田 学

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2000, pp.221-222, 2000-07-25

参考文献数

3

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Field observation and numerical simulations were performed to investigate the atmospheric structure and distribution of air pollutants over Tokyo Bay. The following results were obtained : 1) Observed diurnal variation of potential temperature over Tokyo Bay is different from over the land or the sea. 2) There is a descending flow over Tokyo Bay. and it is the compensation for the divergent flow pattern. The peak value of descending flow exits at the height of 300-500m. 3) The rise in potential temperature in the daytime is caused by the adiabatic heating of descending flow. 4) Vertical gradient of CO_2 is positive over the bay. It suggests that CO_2 is transported over Tokyo Bay from surrounding high emission area.

著者

シャムシドニア ハミドレザ 武田 靖 村井 祐一

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2010, 2010-09-09

著者

三村 和男

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2007, 2007-08-06

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Thermal convection in a closed loop was simulated by using a grid model. From our partial differential equations, a three variables Lorentz like system can be reduced. In stable steady region of main flow, result of the simulation agree with the low order system, very well. In slightly super critical region, result of the grid model shows turbulent stable state in contrast with one of the low order system. In sufficient super critical region, the result shows Lorenz like chaotic reversal of main flow, when special resolution is sufficient. The Lorenz like chaotic reversal of main flow along the loop appeared in rather shrunk parameter region which locates in unstable region of the steady main flow. The chaotic region is surrounded by broad turbulent stable region. On the edge region between chaos and turbulent stable, the behavior has delicate sensitivity for experimental, initial and computational conditions.

著者

嶺 祐太 平原 裕行 蛭ヶ谷 潤

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2009, 2009-09-02

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A laser-induced micro shock wave was observed with shadowgraphic technique. The shock wave was induced on a metal surface by laser irradiation. In this paper, a micro shock wave was introduced in a relatively low intensity energy region. Shadowgraphic images were acquired within 1μs from laser irradiation. The shock Mach number was measured by shadowgraphic images, and it was higher than 5 in 100ns from laser irradiation in present experimental condition. Energy conversion coefficient was estimated by ratio of the shock wave energy to input laser energy. Here, the shock wave energy was estimated by self-similar analysis.

著者

坂東 佳憲 大石 正道 大島 まり

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2007, 2007-08-06

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This paper aims to visualize and measure flow structure in the cerebral aneurysm model, which is based on the medical image data. Since a blood vessel has bend and bifurcation with pulsatile blood flow, the flow structure becomes complex in the three-dimensions. The stereo PIV technique is applied to measure and visualize the flow. We calculate the wall shear stress using measurement data and the geometry data of lost model, which is used to make cerebral aneurysm model. As results of measurement at the peak systole in the pulsatile inflow condition, the flow runs into the tip of the aneurysm. The wall shear stress of the region of the aneurysm is lower than that of the region of the vessel.

著者

宮下 勝浩 新谷 賢司 河村 洋

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2004, pp.400-401, 2004-08-09

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The direct numerical simulations (DNSs) of the turbulent Ekman boundary layer over a smooth surface are performed. The Reynolds number are set to be Re_f=400, 510, 600 and 775 where Re_f based on the Geostrophic wind velocity G, kinematic viscousity υ and Ekman depth D=√<2υ/f>. The large computational box and the long averaging time are employed in order to capture the turbulence structure. A unique turbulence structure is found in the region where the mean velocity reaches its maximum, while the well-known streak structures are discussed using the obtained instantaneous flow field and the two-point correlations.