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).

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

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

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.

著者

斎藤 崇雄 中村 哲也 メンショフ・イゴール 中村 佳朗 前田 一郎 内山 直樹 海田 武司

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.2003, pp.480-481, 2003-07-28

被引用文献数

1

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The phenomena of ignition overpressure (IOP) has been simulated in two cases with the specific heat ratio γ=1.18 and γ=1.4. The former case assumes that a combustion gas fills the overall computational region, while the latter assumes air instead of the combustion gas. The objective of the present study is to investigate whether IOP is affected by the kind of gas. This simulation was performed for a solid rocket booster (SRB) of space shuttle. The time history of pressure rise at the nozzle inlet was taken into account by imitating the SRB ignition. The result with γ=1.18 shows good agreement with the data measured on the surface of STS-Ts SRB.

著者

竹村 早紀 佐々 浩司

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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We simulated supercell type tornadoes with our newly designed mesocyclone simulator and a wall jet generator. The fluctuating velocity of the tornado is measured near the floor by using an X-probe and hotwire anemometers. Its spectrum showed that the velocity field at the lower layer of the tornado was highly turbulent. Its peak corresponds to the existence of suction vortices in multiple vortex type tornado.

著者

山崎 麻未 濱田 一平 佐々 浩司

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

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Our mesocyclone simulator was improved to reduce the effect of separation flow generated from guide vanes. The arrangement between the mesocylone simulator and the gust generator was also changed. The results of flow visualization showed that four different flow patterns occurred depending upon swirl ratio and height.

著者

原 由紀男 中西 幹郎 小林 文明

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 (ISSN:13428004)

巻号頁・発行日

vol.2001, pp.47-48, 2001-07-31

参考文献数

1

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In order to examine the generation mechanism of a cumulonimbus that caused a heavy rain in Tokyo urban area on 22 July 1999,three numerical experiments are performed with a mesoscale simulation model; Case 1 (control run) refers to a nearly realistic experiment, Case 2 an experiment without urban effects, and Case 3 an experiment without raindrop evaporating effects. Although Cases 2 and 3 show slightly different distributions of wind and cloud from what are simulated for Case 1,all the cases reproduce clouds that occurred over Tokyo urban area. This may suggest that the main source generating clouds over Tokyo urban area lies in other effects, e.g., the convergence of sea breezes from Tokyo Bay and Sagami Bay.

著者

斎藤 貴之 台坂 博 出田 誠 岡本 崇 小久保 英一郎 和田 桂一 富阪 幸治 牧野 淳一郎 吉田 直紀

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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In this paper, we introduce Project "Origin of the Milkyway". This project aims at reliable modeling of the formation history of our Galaxy (i.e., the Milkyway), as a typical spiral galaxy, with the mass resolution 2-3 orders of magnitude higher than what has been achieved so far. In order to achieve such state-of-the-art simulations, we construct two beowulf type PC-clusters with GRAPE-6A/7, and we develop a new N-body/SPH code for parallel computing.

著者

佐藤 潤一 澤田 恵介 松山 新吾 大西 直文

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.2003, pp.114-115, 2003-07-28

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Three-dimensional numerical simulations of an accretion disc in a close binary system were performed by solving the Euler equations with radiative transfer. We used the one-dimensional (tangent-slab) approximation to calculate the radiative transfer for the vertical directions of the disc. The cooling effect of the disc is considered by discharging energy in only this directions. The influence of radiative cooling has been accounted for by assuming a specific heat ratio γ which is smaller than that of a mono-atomic gas (=5/3). In the present study, the specific heat ratio was assumed to be constant while radiative cooling effect was included as the non-adiabatic process. Our numerical simulations with radiative transfer demonstrated that spiral shocks existed in three-dimensional disc. It was found that its feature approached in the case of a lower γ but its tendency was weaker than that of two-dimensional simulation.

著者

早崎 公威 岡崎 敦男

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.2003, pp.112-113, 2003-07-28

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We study the accretion onto the neutron star in Be/X-ray binaries, using the 3D SPH code and the data from the simulations by Okazaki et al. (2002) for a coplanar system with a short period (P_<orb>=24.3 days) and moderate eccentricity (e=0.34). We find that a non-steady accretion disk is formed around the neutron star. The disk shrinks after the periastron passage of the Be star and restores its radius afterwards. While the mass-capture rate by the neutron star has a regular, strong dependence on the orbital phase, the orbital modulation in the accretion rate slowly gradually decreases. Our simulations show that the truncated Be disk model for Be/X-ray binaries is consistent with the observed X-ray behavior.

著者

長江 滝三 松田 卓也 藤原 秀和 蜂巣 泉 Boffin H. M. J.

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.124-125, 2002-07-23

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Three-dimensional hydrodynamic calculations are performed in order to investigate mass transfer in a close binary system, in which one component undergoes mass loss through a wind. The mass ratio is assumed to be unity. The radius of the mass-losing star is taken to be about a quarter of the separation of the two stars. Calculations are performed for gases with a ratio of specific heatsγ=1.01 and 5/3. Mass loss is assumed to be thermally driven so that the other parameter is the sound speed of the gas on the mass-losing star. Here, we focus our attention to two features : flow patterns and mass accretion ratio, which we define as the ratio of the mass accretion rate onto the companion, M_<acc>, to the mass loss rate from the mass-losing primary star, M_<loss>. We characterize flows by the mean normal velocity of wind on the critical Roche surface of the mass-losing star, V_R. When V_R < 0.4AΩ, where A and Ω are the separation of two stars and the rotational frequency of the binary, respectively, we obtain Roche-lobe over-flow (RLOF), while for V_R > 0.7AΩ we observe wind accretion. We find very complex flow patterns in between these two extreme cases. We derive an empirical formula of the mass accretion ratio as 0.45×10^<-1.8V_R/AΩ> in the low velocity regime and 5.0×10^<-3> (V_R/AΩ)^<-4> in the high velocity regime.

著者

池田 駿介 粕谷 泉 河村 一弘

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 = Proceedings, ... meeting of Japan Society of Fluid Mechanics (ISSN:13428004)

巻号頁・発行日

vol.2001, pp.61-62, 2001-07-01

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In the curved compound channels, there are secondary flows induced by centrifugal forces and horizontal vortices at the junction of main channel and flood plains. We conducted experiments to measure the horizontal vortices and the velocity field of flow. A quasi-three-dimensional computation using SDS-Q3D model was performed, and the results were compared with the experiments. The result shows that this model is appropriate to simulate the entire flow field except for the inner junction of the main channel and the flood plains where 3D turbulence associated with boils is predominant.