著者
末松 良一 伊藤 思哉 早瀬 敏幸
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.52, no.476, pp.1626-1635, 1986-04-25

It is known that a swirling flow in a diverging pipe breaks down more easily than a flow in a converging one. In this report, experiments are made using diverging, converging and straight pipes, in order to clarify the relation between the shape of pipes and the occurrence of the breakdown. Swirling flow fields, that are realized by rotation of pipes, are measured by a Laser-Doppler-Velocimeter. When each pipe rotates faster than a certain critical value, a stationary internal wave occurs. The vortex breakdown phenomenon is due to the internal waves in swirling flows, as pointed out in preceding reports. In the diverging pipe, the amplitude of the wave is rather smaller than that in the converging pipe ; but the mean axial flow near the axial is fairly retarded, so that the flow reverses at the trough of the superposed wave component, and bubble type breakdown appears. A mathematical model is also presented to give a qualitative explanation of the effect of a sectional area variation.
著者
角田 勝
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.69, no.678, pp.346-353, 2003-02-25

An experimental investigation of pulsating flow through a tapered curved tube is presented to study the blood flow in the aorta. The experiments are performed in a U-tube with the curvature radius ratio of 3.5 and including 50 percent reduction in the cross-sectional area between the inlet and the exit of the curved section. Laser Doppler velocity measurements are made for the Womersley number of 10, the mean Dean number of 400 and the flow rate ratio of 1. Flow visualizations are used to investigate qualitatively the nature of the flow, complementing the quantitative LDV measurements. The velocity profiles for the steady and pulsating flows in the tapered U-tube are compared with the corresponding results in a U-tube having a uniform cross-section. The striking effects of the tapering on the flow are exerted on the axial velocity profiles in the section from the latter half of the bend to the neighborhood of the inlet of a downstream tangent. A depression phenomena in the velocity profile appears at the position of smaller bend angle Ω and the degree of the depression against the cross-sectional averaged velocity is reduced. Strong secondary fluid motions occur near the bend exit and that leads a velocity profile to depress weakly in the downstream tangent. The value of β_m which indicates a uniformity in the velocity profiles decreases with an increase of Ω, but it rapidly increases just after the bend exit.
著者
鵜沢 潔 池尾 茂
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.51, no.472, pp.4230-4238, 1985-12-25

This paper deals with the laminar oscillatory flow of an incompressible fluid through a slightly convergent tube. The velocity distributions in the convergent tubes, whose convergent angles are in the range of 2~4°, are measured by a Laser Doppler Velocimeter. The flow in the convergent tube is numerically analysed by a finite difference method (SOR), without neglecting the convective terms in the Navier-Stokes equation. Experimental results agreed well with the numerical ones. The velocity profile of a laminar oscillatory flow in the convergent tube is quite different from the velocity profile in a straight tube of circular cross-section, even if the convergent angle is very small. The instantaneous pressure distribution in the convergent tube is uniform at each cross section as in a straight circular tube.
著者
親川 兼勇 小池 徹 馬渕 幾夫
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.59, no.558, pp.543-549, 1993-02-25
被引用文献数
1

The local heat transfer coefficients downstream of a backward-facing step were measured at various jet locations and jet velocities by discharging a jet perpendicularly to the main flow to control the heat transfer characteristics. It was found that flow field is characterized by the formation of a circulating bubble at the rear of a jet port on the opposite wall of the step surface (i.e., the jet port side), where the bubble causes acceleration of the main flow and shortening of the reattachment point length. Furthermore, at the optimum position X_j/H=2. 1(X_j : location of jet, measured from the step)position, H : the step height), the augmentation of mean heat transfer coefficients can be as much as 1. 6 times the value without jet discharge. Thus, by using a jet it is possible to control the heat transfer effectively.
著者
中林 功一 鬼頭 修己 加藤 義孝
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.61, no.589, pp.3122-3129, 1995-09-25
被引用文献数
4

Mean velocity profiles of Couette・Poiseuille-type turbulent flow developed between fixed and moving walls have been measured. The relevant parameters for the wall, 1/2-power and core region are μ(=μ^3_*/αν, where α=1/ρ・dτ/dy) and Re^*'(=u_*h'/ν), β'(=αh'/u^2_*) and Re^*', and β(=αh/u^2_*) and Re^* (=u_*h/ν) respectively. The effects of these parameters on the velocity profiles in each region considered. Except for the core region of the Couette-type flow, each region has a reference wall. In the wall region, the wall law varies largely with μ but slightly with Re^*'. Typically, the additive constant B of the logarithmic-velocity low (or Van-Driest damping factor A^+) is shown to depend only on μ. The 1/2-power velocity law depends not only on β', as well known, but also Re^*' under low Re conditions. In the core region, the normalized eddy viscosity ε_T/u_*h' is constant irrespective of Re^* and β for Poiseuille-type flow while it depends on both Re^* and β for Couette-type flow. This indicates that the turbulent structures of the core region are quite different between Poiseuille-and Couette-type flows.
著者
伊藤 智仁 志澤 高朗 本阿弥 眞治
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.66, no.644, pp.985-989, 2000-04-25
被引用文献数
1

The phase-averaged characteristic of a single pulsed vortex generator jet which is injected periodically into a turbulent boundary layer is described. Detailed measurements of the three components of the velocity in the jet made by a hot-wire anemometer with the X-type probe show evolution of the longitudinal vortex in the jet. The pulsed vortex generator jet in the stable period has a similar longitudinal vortex structure to that in the steady one. Down-wash motion of the longitudinal vortex in the jet introduces high wall shear stress.
著者
新井 雅隆 天谷 賢児 長瀧 翼 沖田 秀樹
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.71, no.702, pp.737-743, 2005-02-25

Ignition and combustion characteristics of diesel spray impinging on an inclined wall were experimentally investigated. Ignition position and appearance position of the luminous flame kernel were stereoscopically observed using a two-way fiber optical system. Flat impingement wall was fixed in a high temperature, high pressure combustion chamber. Inclined angle of the flat wall was set at 30 degees or right angle against the center axis of the injection spray. Distance from nozzle tip to the impingement point on the wall was set at 50mm. Effect of ambient temperature on ignition position was investigated. As the result, ignition positions were observed near the spray periphery in the both cases of 30 degrees and right angle impingements. However, the luminous flame appeared near the wall surface at downword side of inclined wall because the fuel rich region was formed around the downword side of spray impingement point.
著者
川口 知宏 長瀧 翼 天谷 賢児 古畑 朋彦 新井 雅隆
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.72, no.717, pp.1378-1383, 2006-05-25

Ignition and combustion characteristics of diesel spray impinging on a wall were experimentally investigated. Ignition position and appearance position of the luminous flame kernel were stereoscopically observed using a two-way fiber optical system. Flat
著者
藤田 稔彦 手塚 俊一
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.49, no.443, pp.1521-1529, 1983-07-25
被引用文献数
2

向流形および直交流形の強制通風冷却塔の熱的性能について,エシクルピ差を用いた理論にしたがって,電子計算機により広範囲の計算を行った.まず交換係数を簡単に精度よく手計算する方法について検討し,直交流形の修正係数を求めた.つぎに強制通風冷却塔の特性を考慮して,入口湿球温度とレンジの関係を示す性能曲線を求め,その傾向を調べた.この結果から,強制通風冷却塔の簡単な性能試験と評価の方法を導いた.
著者
竹島 敬志 藤井 照重 竹中 信幸 浅野 等
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.66, no.646, pp.1467-1472, 2000-06-25
被引用文献数
1

An experimental study has been carried out to clarify the characteristics of the void fraction and liquid film thickness of air-water two-phase flow in vertical tubes of 25 mm inside diameter with wire coil of varying wire diameter and pitch. Flow pattern in the experiment of average void fraction and local void fractrion distribution in a cross section is bubble flow, and liquid film thickness is in the region of semi-annular and annular flow. It is clarified from these experiments that the average void fraction in tubes with a wire coil is lower than that of the smooth tube and decreases with the wire diameter owing to the centrifugal force of swirl flow which concentrates bubbles at the center of the tube, and the liquid film thickness between the wire coil is uniformed with the decrease of the pitch of wire coil and that liquid film becomes thicker after the passage of wire coil with the increase of the wire diameter.
著者
石井 俊夫 岸本 健 永田 勝也
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.50, no.449, pp.151-158, 1984-01-28
被引用文献数
2

ヘルムホルツ形燃焼振動をしている燃焼器に膨張形消音器および共鳴器消音器を付設して、それぞれの燃焼に及ぼす影響について議論し、また、音響インピーダンスの配分をばね-質点系モデルの上で実現し、配分割合の周波数依存性をテコ-コロを用いて摘用させた。その結果十分精度あるモデル化ができ、このタイプの消音器設計に有意な寄与できる方法を確立した。
著者
許斐 敏明 佐々木 洋二郎
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.71, no.705, pp.1428-1435, 2005-05-25
被引用文献数
22

A technique to be able to improve efficiency of PEFC (Polymer Electrolyte Fuel Cell) has been investigated by classification into over voltages. Effects of running condition on it were surveyed by using this technique. Results show that dry condition at MEA makes cathode activation and IR over voltage increase, and that wet condition increases cathode concentration over voltage caused by flooding. It is proved this technique could be able to obtain best running condition in trade off and to improve efficiency of PEFC.
著者
新井 雅隆 樋口 豪 廣安 博之
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.50, no.453, pp.1345-1352, 1984-05-24

軽油および複合燃料によるディーゼル噴霧の着火おくれを定容燃焼器を用いて測定した。この際、着火おくれは発火おくれとし、これをフォト・トランジスタにより検出した。測定結果をアレニウス表示したところ、高温側と低温側に分かれた2本の直線になることがわかった。またエタノール混合軽油で約50%以下、水-軽油エマルジョンで約40%以下の混合割合であれば、着火おくれは軽油の場合と大差のないことがわかった。
著者
笹原 俊雄 山崎 慎三 富田 幸雄
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.46, no.404, pp.673-683, 1980-04-25

再生形にて主として送風機内部流れおよび性能と機械諸要素との関係を実験的に研究し,さらに粘性を変えて実験したポンプの場合も含めて検討し,つぎのことを明らかにした.(1)内部流れと機械諸要素の関係は送風機およびポンプととも類似の傾向を示し,性能諸係数も同じ無次元数で概略の整理が行える.(2)流路の断面内および全区間にわたって羽根角度が異なる送風機の内部流れを調べ,特に逆流が性能曲線の特長と密接に関係する.
著者
藤居 達郎 西口 章 福島 敏彦 大内 富久 功刀 能文
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.61, no.587, pp.2683-2689, 1995-07-25
被引用文献数
1

This paper presents an experimental validation of the mathematical model of an evaporator and absorber, which are components of a water/lithium-bromide absorption chiller heater. The experimental cycle employs a gas-fired, 176 kW (50 RT) machine, which is mainly used in individually distributed air conditioning systems. One of the features of this model, described in the 1st report, is prediction of both static and dynamic characteristics of the machine, especially transient response to rapid change in external conditions. In this experiment, an immediate change in chilled water flow rate is the input signal. Output signals for comparison with predicted data are transient responses of chilled water outlet temperature, evaporating pressure and cooling capacity derived from chilled water temperature and its flow rate. From comparison between experimental data and values predicted using the model, steady-state analytical error is less than ±3%, and dynamic behavior can be predicted within ±10% analytical error of response time.
著者
黒川 淳一 森川 薫博
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.51, no.467, pp.2076-2083, 1985-07-25
被引用文献数
15

円管内の加速・減速流れにおける速度分布,遷移および管摩擦係数に及ぼす加速度の影響をおもに実験的に検討した.その結果,粘性の伝ぱ速度に対して加速が大の場合と小の場合では断面速度分布および遷移レイノルズ数が著しく異なり,層流加速域と乱流加速域では管摩擦係数の傾向が異なること,および減速流れではほぼ全期間を通じて乱流状態が保持され,管摩擦係数は準定常値より大きくなることなどを明らかにした.
著者
古川 明徳 曹 銀春 大熊 九州男 眺野 貴裕 渡邊 聡
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.67, no.657, pp.1184-1190, 2001-05-25
被引用文献数
11

Demands for higher performance of axial flow pumps have led pump designers to consider the creative strategies for the new type. As a solution, contra-rotating rotors might be applied to a pump. Comparative experiments were conducted for two types, consisting of contra-rotating rotors and a rotor and a stator respectively, which were designed under the same specifications of pump head, flow rate and rotor specific speed. The measured pump performances and flow distributions are shown and the advantages of using contra-rotating type are clarlfied as follows. Contra-rotating type is superior in pump efficiency and cavitation performance in range of partial flow rates to conventional one though the specified pump head and maximum efficiency were not satisfied at design point in the case of contra-rotating test rotors. Results demonstrate that the rear rotor design is important to improve the pump efficiency.
著者
富山 明男 平野 雅司 松田 隆男 坂口 忠司
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.58, no.551, pp.2177-2183, 1992-07-25
被引用文献数
1

Computational time for numerical simulation of transient incompressible viscous flow is governed by numerical methods to solve the Poisson equation of the pressure. In order to improve the computational efficiency of the SOR method, a mathematical analysis was conducted in the present study to derive the spectral radius, i. e., the maximum modulus of the eigenvalues of the iteration matrix for a discrete Poisson equation in staggered mesh system. The derived spectral radii for the point, line and area Jacobi iteration matrices are applicable to the Dirichlet, the mixed boundaryvalue and the Neumann problems in an n-dimensional rectangular region. The validity of the optimum relaxation parameter of the SOR method, which was calculated by the derived spectral radii, was confirmed by numerical experiments. Furthermore, a simple estimation method of the optimum relaxation parameter for the non-rectangular region was presented for transient flow analyses.
著者
田辺 誠一 山口 雄三 横山 俊昭 高木 武夫
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.51, no.464, pp.1147-1156, 1985-04-25

高比速度フランシス水車ランナの出口流れを非定常流れ計測用のピトー管を使って測定し,ランナ出口部におけるベーン間の流れのようすを明らかにした.特に,油膜流跡実験結果と対比させて検討することにより,ランナベーンの後流部やベーン負圧面に逆流が発生した時の流れのようすを明らかにした.
著者
眞下 伸也 仲津 英治 青木 俊之 松尾 一泰
出版者
一般社団法人日本機械学会
雑誌
日本機械学會論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.62, no.597, pp.1847-1854, 1996-05-25
参考文献数
23
被引用文献数
6

Compression waves generated by a high-speed train entering a tunnel were measured in three Shinkansen tunnels and the results were compared with the numerical values calculated using the TVD scheme. The strength of a compression wave is exponentially attenuated with distance as it propagates along the tunnel in both slab and ballast track tunnels, and the attenuation in the ballast track tunnel is considerably larger than that in the slab track tunnel. In the slab track tunnel, the compression wave is steepened as it propagates, while it spreads in the ballast track tunnel. The criterion for judgment whether the compression wave is steepened or spreads is expressed by the value of acoustic Reynolds number of about l0〜15.