著者
内藤 健 伊東 輝之 高木 靖雄 桑原 邦郎
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.59, no.559, pp.953-959, 1993-03-25

Large-eddy simulation of a turbulent premixed flame in an engine is performed in a wide range of operating conditions such as engine speed, airfuel ratio, and ignition timing. A numerical method for estimating supergrid fluctuations of physical quantities and the space-averaged quantities accurately is proposed. As the subgrid estimations, the Yakhot-Orszag turbulence model based on the renormalization group theory and a flamesheet model are employed. For some variations of the operating conditions, obtained computational data agree well with experimental data on turbulence intensity and pressure history. It is also shown that the developed numerical model has the potential of calculating the cyclic variations of flow and combustion. An important understanding on the physical situation in conventional 4-valve engines, is obtained from the present study, which is that laminar regions may exist at the low engine speeds.
著者
蒔田 秀治 飯田 明由
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.55, no.515, pp.1847-1854, 1989-07-25

The local similarity hypothesis was verified in quasi-isotropic turbulent flow fields with turbulence Reynolds numbers of over 3000. The quasi-equilibrium range was known to exist in a turbulence field with turbulence Reynolds numbers of Re_τ >60. The lowest wave number of the quasi-equilibrium range in the energy spectrum was dependent on T_L/T_O : the ratio between the time scale of decay of turbulence energy and the characteristic time scale o an energy-containing eddy. Turbulent eddies with characteristic time scales of less than T_L/4 were statistically stable. The energy dissipation rate was theoretically determined as ε=C_1(q^2/2)^<3/2>/l_O, and the scales of turbulence were estimated from C_1 and Re_λ.
著者
高木 周 松本 洋一郎 黄 華雄
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.61, no.586, pp.1976-1983, 1995-06-25
被引用文献数
10

A numerical method is developed to simulate the unsteady axisymmetric flow with a free surface. The method is based on a finite-volume solution of the equations on an orthogonal curvilinear oordinate system. A new iteration technique is used for the boundary condition of the free surface to stabilize the solution. The method is applied to simulate an unsteady motion of a single deformed bubble rising through a quiescent liquid. The numerical results show quantitatively good agreement with those of experiments and calculations of others. In the present study, the transitional phenomena of the initially spherical bubble in reaching the steady state are investigated. It is known experimentally that the rising bubble begins to show an unsteady three-dimensional (spiral or zigzag) motion beyond certain critical Reynolds and Weber numbers. Our numerical results of the axisymmetric flow show unsteady shape oscillations in the parameter range of the three-dimensional motions.
著者
浜口 和洋 高橋 真太郎 宮部 英也
出版者
一般社団法人日本機械学会
雑誌
日本機械学会論文集 B編 (ISSN:03875016)
巻号頁・発行日
vol.48, no.435, pp.p2207-2216, 1982-11
被引用文献数
3

スターリング機関再生器のマトリックス材としてメッシュ数の大きい金額を多数枚積層したものが使用されているが, その流動損失に関する研究は少ない. 本研究では, 10から300メッシュまでの広い範囲の金網を積層したマトリックスの定常流および非定常流における流動損失を調べた. おのおのの場合において, 金網の幾何学的形状を知ることにより, 任意の金網の摩擦係数をレイノルズ数の関数として与える実験式が得られた.
著者
藤沢 延行 Adrian Ronald J.
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.63, no.607, pp.818-823, 1997-03-25
被引用文献数
8

A new calibration technique of liquid crystal thermometry has been introduced to the quantitative measurement of temperature in a thermal fluid and applied to the study of turbulent thermal convection. The present calibration technique improves the accuracy of temperature measurement in comparison with the classical calibration technique with hue. Three-dimensional temperature measurement of turbulent thermal convection over a horizontal smooth surface is carried out at a flux Rayleigh number of 3×10^9 by scanning a light sheet normal to the image plane and capturing a number of sequential visualized images. The spatial temperature distributions of thermal plumes over a horizontal surface are demonstrated by the reconstruction of isothermal contour surfaces and various cross-sectional views of the plumes. These results indicate the presence of a polygonal cell structure close to the surface and the generation of plumes at the intersections of high-temperature lines.
著者
清水 徹 横川 明 鈴木 基光 中村 育雄
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.51, no.469, pp.2908-2915, 1985-09-25
被引用文献数
1

種種の乱れ発生要素を入り口に設けたく形断面流路における繊維懸濁液流れの濃度むらを比較的高い濃度にわたって測定し,その管軸方向への分布や平均濃度および平均流速に対する依存症について検討した.この結果,流れの乱れによる濃度むらの減少には限界値が存在すること,また十分に発達した流れ場における繊維懸濁液の濃度むらは非ニュートン流体の広義のレイノルズ数で整理できることが明らかになった.
著者
篠山 鋭一 斉藤 敬三
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.47, no.421, pp.1891-1899, 1981-09-25

比較的光化学スモッグが発生しやすい条件を基本にとり, この条件から各種因子を変えてスモッグチャンバによる光化学エアロゾルの生成実験を行うことによりこの条件における各種因子の影響を調べた. HCはエアロゾル生成に正負両面の影響を持ちその影響は種類により大きく異なること, NO_xは負の影響を持つと考えられること, SO_2は正の影響を持つこと, 湿度は大きな正の影響を持つことなどが解明された.
著者
佐藤 義久 吉田 尚嗣 田辺 幸典 藤田 秀紀
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.1335-1341, 2006-05-25
被引用文献数
2

It is necessary to use the low temperature thermal energy around 100 degress C from a viewpoint of global warming prevention. Even if a shape memory alloy is bent in normal temperature, when it is heated, it has the character which returns to the original straight form. Using this character of a shape memory alloy, unused thermal energy will be able to transform into rotation energy. A shape memory alloy belt is hung on a high temperature wheel and a low-temperature wheel. On this simple pulley type shape memory alloy engine, a shape memory alloy belt is heated with a high temperature wheel, it occurs a moment when returning to the original straight form, the moment kicks a high temperature wheel by the principle of action reaction, and torque is generated. We solved this torque generating mechanism. We proposed the theory which can design the output power of the simple pulley type shape memory alloy engine. Furthermore, the validity of this theory was verified by experiment.
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
岩本 順二郎
出版者
一般社団法人日本機械学会
雑誌
日本機械学会論文集 B編 (ISSN:03875016)
巻号頁・発行日
vol.52, no.482, pp.p3422-3427, 1986-10

The results of experiments on the thermal effect for tubes of different tapers are presented, and the effects of the tapering of the tube on the internal flow are shown. The results are summarized as follows: (1) With a tapered tube a higher temperature is obtained with smaller intervals of nozzle-tube spacings compared with the cylindrical tube. (2) With a tapered tube a higher frequency of flow oscillations and a shorter penetration length of contact surfaces which are considered to cause a higher temperature in the tube, together with stronger shock, are obtained (3) The velocity history at the open end is different for tubes with different tapers. When the taper is small, the amplitude of the velocity change becomes very small. (4) The pressure amplitude at the closed end becomes large for tubes with large tapers.
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
菅 牧子 河村 哲也 岩津 玲磨
出版者
社団法人日本機械学会
雑誌
日本機械学会論文集. B編 (ISSN:03875016)
巻号頁・発行日
vol.65, no.629, pp.108-115, 1999-01
参考文献数
16

The natural convection with large temperature difference is computed numerically using the Low-Mach-Number approximation with temperature dependent viscosity and thermal conductivity. In this study staggered grid system is used in order to hold down the numerical oscillation. Firstly, steady laminar natural convection above a horizontal heat source is simulated in order to validate the simulation method. The result is in good agreement with the analytical solution. Secondly, two dimentional flow field driven by two parallel heat sources is computed. This boundary condition may be regarded as a model situation of the big fire covering both sides of a wide straight road. At the same time, it is interesting to investigate interactions between two thermal plumes. The numerical results disclosed different flow behavior when the imposed temperature of the heat sources is changed and the rest of the governing system parameters are varied.
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.