著者

八木田 幹 鹿野 一郎 清野 将人

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.70, no.691, pp.594-601, 2004-03-25 (Released:2011-03-03)

参考文献数

17

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This paper presents experimental and numerical results on the unstable flow along the surface of a circular cylinder in the Coanda effect. The unstable phenomenon depends on the nominal Reynolds number Re*=Uj√ (1/4) hD/ν and the nozzle height of the jet, h. In this paper, the changing phenomenon of two-dimensional jet direction is found numerically and the results are compared with the experimental ones. The numerical calculation is carried out by using the finite-difference method for the conditions of unstable phenomenon, that is, 1.5×104≤Re*≤2.5×104 and 0.100≤h/D≤0.200. Numerical results agree well with experimental results qualitatively. Also, it is found that the unstable phenomenon is sensitive to both Re* and h/D in the vicinity of h/D=0.10. Furthermore, a hysteresis phenomenon of jet direction by Re* was observed.

著者

小原 哲郎 大八木 重治 高藤 亮一 蔡 品

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.67, no.659, pp.1680-1686, 2001-07-25 (Released:2008-03-28)

参考文献数

14

---

Experiments are carried out to investigate behavior of shock wave diffraction from a safety-engineering point of view. Because, once the shock wave is released into an ambience, high pressure and negative pressure lasting for relatively long period have possibility to cause serious damages against human bodies as well as general buildings. Therefore, it should be one of the most significant subjects to attenuate the shock wave efficiently within a short distance from the source. In this report, a cavity is installed at an open end of a shock tube and flow-fields behind diffracted shock wave are visualized using schlieren photography. In addition, piezo-electric pressure transducer is flush mounted on the surface of reflector, which is installed at test section, and pressure histories are recorded with wide frequency response. Lastly, numerical simulation using the TVD finite difference scheme is performed to compare with the experimental results. As a result, (i) the pressure histories on the reflector coincides well between the numerical and experimental results, (ii) flow-fields behind the shock wave are clarified, (iii) maximum pressure behind reflected shock wave can be attenuated by installing several cavities inside the open end of the shock tube.

著者

高藤 亮一 山中 昭央 小原 哲郎 蔡 品 大八木 重治

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.65, no.639, pp.3602-3607, 1999-11-25 (Released:2008-03-28)

参考文献数

12

被引用文献数

2 2

---

As is well known when a shock wave is emitted from an open end of a tube, an expansion wave and a vortex ring are generated behind the shock wave. Furthermore, a contact surface, slip line and these wave interactions may cause considerably complicate flow-fields. In this study, shock waves of Mach number 1.3, 1.6 and 2.2 are produced utilizing diaphragm-less shock tube of 50 mm diameter and c. a. 10 m total length, and the flow-fields are visualized with an aid of schlieren optical techniques. A cylindrical reflector is installed at test section and stagnation pressure behind reflected shock wave is measured with wide frequency response. A numerical analysis is also carried out to investigate these flow-fields using Predictor-Corrector TVD finite difference scheme. As a result, (i) the contour of diffracted shock wave is well coincided between experimental and numerical results, (ii) pressure histories behind reflected shock wave are clarified, (iii) an empirical formula is obtained between Mach number, non-dimensional distance from the open end of the tube and non-dimensional pressure just behind reflected shock wave.

著者

米本 幸弘 功刀 資彰

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.74, no.742, pp.1310-1317, 2008-06-25 (Released:2011-03-03)

参考文献数

16

被引用文献数

1 2

---

The Young's equation describes the interfacial equilibrium condition of a liquid droplet on a smooth solid surface. This relation is derived by Thomas Young in 1805. It has been discussed until today after his work. In general, the Young's equation is discussed from the viewpoint of thermo-dynamics. However, there is no answer which elucidates the normal force balance σlg sin θ in the Young's equation. From the hydrodynamics point of view, there is a momentum jump condition at a gas-liquid interface. This jump condition is derived based on mechanical balance by using mathematical procedure such as Stoke's theorem and the differential geometry. In this study, we reconsider the Young's equation from this momentum jump condition point of view. Finally, we dynamics. However, there is no answer which elucidates the normal force balance σlg sin θ in the Young's equation. From the hydrodynamics point of view, there is a momentum jump condition at a gas-liquid interface. This jump condition is derived based on mechanical balance by using mathematical procedure such as Stoke's theorem and the differential geometry. In this study, we reconsider the Young's equation from this momentum jump condition point of view. Finally, we derive the revised Young's equation in which there is the normal force term (σlg sin θ). Then, we evaluate the revised Young's equation by comparing the analytical solution with the experimental data reported by Amirfazli. Moreover, we discuss on the line tension and the contact angle for a lens

著者

中村 元 福江 高志 小泉 雄大 石塚 勝

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.76, no.768, pp.1184-1190, 2010-08-25 (Released:2017-06-09)

参考文献数

8

被引用文献数

4 2

---

A compact air-cooling device often encounters high-density mounting environment, which may reduce a flow-rate of a cooling fan. In this work, the PQ characteristics of a cooling fan was investigated which varied by placing an obstacle in close proximity of a fan. Small axial-flow fans of 30-80mm in side length and small centrifugal fans of 35-52mm in side length were tested here. As a result, it was found that the maximum flow rate for the free air-flow begin to decrease when the opening area of the gap-flow between the fan and the obstacle becomes smaller than twice the fan flow area, and decreases suddenly if it becomes smaller than the fan flow area. This relation was almost independent of type and size of a fan, rotation speed of impeller, and shape and position of an obstacle.

著者

段 智久 大石 直己 千田 二郎 藤本 元

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.60, no.577, pp.3192-3197, 1994-09-25 (Released:2008-03-28)

参考文献数

4

被引用文献数

1 6

---

In the experiments presented, a single diesel spray of n-tridecane was injected for a certain duration through a hole-type nozzle into a quiescent atmosphere at room temperature at high pressure. The experimental variables were nozzle hole dimensions such as the hole diameter dn, the hole length ln and the hole offset between the nozzle axis and the hole axis, and the nozzle needle lift, in order to assess the turbulent flow field inside the nozzle, and the other was the back pressure, in order to examine the effect of the ambient gas properties, especially its kinematic viscosity. The macroscopic spray structures were observed by using instantaneous photography and a high-speed video camera system. Furthermore, the microscopic structure was observed by meant of scattering photography of fuel droplets taken by the laser light sheet of a pulsed ruby laser, and the quantitative 2-D image of fuel concentration in the cross section of the spray containing its central axis was obtained by the image processing. From the experiments, the variation in the spray cone angle with the needle lift is promoted by the turbulence in the sac volume, and spray angle is closely related to the ambient kinematic vincosity.

著者

清水 優史 谷田 好通

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.434, pp.1936-1944, 1982-10-25 (Released:2008-03-28)

参考文献数

9

---

血圧測定のよりどころであるコロトコフ音の発生機構のうち最低血圧でのそれを, 実験及び理論計算により明らかにした. コロトコフ音は外圧によりいくぶん圧平された管部を圧力波が出播する際, 波の先頭部に形成される圧力不連続面(衝撃波面)が管を急激に膨張させることにより生ずる. この衝撃波面は管法則の非線形性に起因する波の追いつき現象により作られ, その強さは管の圧平の度合と圧平部長さにより決定される.

著者

清水 優史

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.50, no.460, pp.3107-3115, 1984-12-25 (Released:2008-03-28)

参考文献数

9

---

The genesis of Korotkoff sound at high cuff pressure has been made clear by the model expreimental study using the thin walled silicon rubber tube being modified to have zero internal cross sectional area as an artery ehen compressed by the relatively higher external pressure than the internal one. The sound is generated by the steep pressure wave front formed in the course of pressure wave propagation through the completely collapsed tube segment under the cuff. The amplitude of the pressure wave penetrating into the collapsed tube segment and that of the steep wave front reaching to the distal end of the segment, measured from the artery also weakens correspondingly and, at some Peb, the sound becomes unaudible. The pressure wave form depends strongly on the transmural pressure at the distal end of the collapsed segment.

著者

田中 忠良 山田 幸生 石黒 博 竹内 正顕 山下 衛 小竹 進

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.55, no.515, pp.p2018-2023, 1989-07

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The body temperatures of anesthetized patients under going operations decrease gradually because control of the body temperature is suppressed and the temperature of the operating room is kept lower than the body temperature. In order to prevent a patient's body temperature from lowering during an operation, a mat with hot-water circulation is often used. However, it has been reported that burn injuries occasionally occur in such cases, even when no defect in temperature setting and control of the mat is found. The mechanism causing this burn injury has not been determined. This report analyzes the heat transfer of a body-mat system simulated by a simplified model to examine the possibility and mechanism of such burn injuries. The analysis discusses the effects of hot-water flow rates, hot-water temperature and metabolic heat generation on body temperature. It is found that burn injury can occur, particularly in the high metabolic state, when heat transfer by the blood flow is negligible and the rate of water flowing into the mat is reduced considerably.

著者

鈴木 敦 藤岡 和正 桑原 平吉 高崎 利夫

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.62, no.595, pp.1172-1177, 1996-03-25 (Released:2008-03-28)

参考文献数

3

---

This study describes the transient temperature distribution in a cooling apparatus for high-power semiconductor devices used to drive motors of electric rolling stocks. The cooling apparatus is composed of heat pipes. In the model for simulation, we substituted solid elements for heat pipes, and determined their thermal properties by experiment. Consequently, the heat transfer rate of heat pipes can be obtained by a heat conduction analysis. Calculations show that when heat generation in the device changes, the temperature of cooling apparatus changes more slowly than that of the devices. A comparison between calculations and experiments confirms the accuracy of the modeling and prediction method.

著者

森西 洋平

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.62, no.604, pp.4098-4105, 1996-12-25 (Released:2008-03-28)

参考文献数

8

被引用文献数

12 10

---

In this report, finite difference schemes in staggered and collocated grid systems are considered in light of the analytical requirements that were discussed in the first report. The standard second-order accurate finite difference scheme with divergence form in a staggered grid system is proper. Proper second-order accurate advective and skew-symmetric forms have been proposed in the staggered grid system. Existing fourth-order accurate convective schemes in a staggered grid system are not proper. Proper higher-order accurate finite difference schemes in a staggered grid system are proposed. This is novel because higher-order staggered grid schemes that conserve momentum and kinetic energy simultaneously do not previously appear in the literature. The pressure term is not conservative in the kinetic energy equation in the collocated grid system, although we can construct proper-second and fourth-order accurate convective schemes in this system.

著者

梶島 岳夫

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.60, no.574, pp.2058-2063, 1994-06-25 (Released:2008-03-28)

参考文献数

16

被引用文献数

29 33

---

A proper finite difference method based on the gradient/convective form of the equation of motion of incompressible fluid is discussed. The gradient form discretized on the staggered grid has essentially the same conservation properties as those of the divergence/momentum-conservative form or the quadratic-conservative form under some conditions. First, the mass continuity should be numerically satisfied. Second, the numerical consistency between the mass continuity and the momentum convection should be satisfied. The gradient form evaluated at midpoints between velocity points in the direction of convection, rather than directly calculated at velocity points, meets this requirement. In this paper, through mathematical description of the above-mentioned features, the performance of the higher-order finite difference method for the gradient form is demonstrated.

著者

山田 敏郎 可児 弘毅 生田 耕治

出版者

The Japan Society of Mechanical Engineers

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.47, no.415, pp.450-460, 1981

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衝撃超高圧力研究用に超高速飛しょう体発射装置(二段式軽ガス銃)が試作され, その性能の数値解析が試みられた. 試作装置により16.4gの飛しょう体が3.57km/sまで加速・発射された. 発射実験結果と性能解析の予想値との良い一致により, 解析法の妥当性が確かめられた. 性能解析により, 試作装置は9.5gの飛しょう体が5km/sまで加速できることおよび発射速度支配因子のうち, 特に装薬量と飛しょう体質量の影響が大であることなどが明らかにされた.

著者

田中 耕太郎 根岸 明 増田 俊久

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.58, no.553, pp.2857-2862, 1992-09-25 (Released:2008-03-28)

参考文献数

13

---

The replacement of working fluid of the alkali metal themoelectric converter (AMTEC) is eminently suitable for achieving higher performance under lower operating temperatures. Potassium is a reasonable condidate because it has lower latent heat of vaporization and higher vapor pressure than sodium over the AMTEC operating conditions. The performance of the AMTEC cycle with potassium as the working fluid has been evaluated and discussed based on the recently reported ionic conductivity data of potassium-β"-alumina solid electrolyte. The calculated results show that the replacement of working fluid increases the peak efficiency from 28% to 31% at 1100K with 1mm thick β"-alumina solid electrolyte. If the thinner solid electrolyte is practically developed, the improvement of the performance can obviously be recognized because of the decrease of ionic conductivity.

著者

佐藤 明

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.61, no.583, pp.933-938, 1995-03-25 (Released:2008-03-28)

参考文献数

15

---

The object of the present study is to evaluate the performances of various microcanonical molecular dynamics algorithms. To do so, the divergence times and energy fluctuations are discussed for a model system, i. e. a three-dimensional Lennard-Jones system under various conditions of number densities and temperatures. The results of the evaluations of superiority or inferiority of algorithms are as follows. The velocity Verlet, leapfrog, and Beeman algorithms are significantly superior to the other algorithms such as the 4-value Gear algorithm since a system does not diverge and the energy conservation law is reasonably satisfied for much larger time intervals. Although these three algorithms show approximately the same performance concerning the properties of divergence times and energy fluctuations, we can conclude that the velocity Verlet algorithm is the most suitable for molecular dynamics simulations of flow problems, since this algorithm is easy to use, requires less computer memory, and evaluates molecular positions and velocities at the same time steps.

著者

梶島 岳夫 太田 貴士 岡崎 和彦 三宅 裕

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.63, no.614, pp.3247-3254, 1997-10-25 (Released:2008-03-28)

参考文献数

25

被引用文献数

13 13

---

To apply the direct numerical simulation (DNS) and the large-eddy simulation (LES) of turbulence to flow fields of complicated geometry, a higher-order finite-difference method (FDM) has been developed for the body-fitted coordinate system. The consistency and the conservation property of FDMs are discussed for the collocated grid. As numerical examples, DNS results of decaying isotropic turbulence and DNS/LES results for plane channel flow are shown and the influence of variable arrangement is examined. The results by the consistent 'interpolation' method for gradient form on the collocated grid agree well with those by other proper FDMs and the spectral method.

著者

千田 二郎 柴田 一郎 段 智久 藤本 元

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.63, no.613, pp.3173-3178, 1997-09-25 (Released:2008-03-28)

参考文献数

8

被引用文献数

1 2

---

This study investigates the atomization mechanism of fuel spray dissolved in noncondensable gas, such as N2, CO2. The fuel spray was injected at room temperature and in an atmospheric pressure field through a diesel-hole-type nozzle. In this paper, N2 gas was dissolved into diesel fuel, n-tridecane, under several pressurized conditions using a gas bubbling method in a constant volume vessel. This fuel, with high gas solubility, was injected under several injection pressures using an accumulated injection system designed by the authors. It was found that the dissolved gas separated into gas bubbles like gas cavitation phenomena under the atmospheric field. The change in spray patterns caused by the gas solubility is discussed using photographs of the patterns.

著者

西原 淳夫

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.73, no.728, pp.1052-1058, 2007-04-25 (Released:2011-03-03)

参考文献数

15

被引用文献数

1 1

---

An optimization method for fin pitch in naturally cooled heat sinks is described. Because the heat sinks for the power units of electric trains are stacked vertically, lower heat sinks heat upper heat sinks. However the fin pitch of conventional heat sinks is optimized as single heat sink without accounting for the influence of the lower heat sinks. Equations to predict heat dissipation and a rise in exhaust air temperature in the heat sinks, along with an optimization method for the fin pitch are presented. These equations were carried out from a developed profile of velocity and temperature between two plates. A valid range of the Rayleigh number for the equations is shown, and the optimizing process for the fin pitch of stacked heat sinks is described. The experimental results of the rise in fin temperature of triple stacked heat sinks are compared with the calculated results. The heat sink with optimized arrangement of fins shows over 10% improvement in performance compared with the conventional heat sink.

著者

森西 洋平

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.65, no.630, pp.505-512, 1999-02-25 (Released:2008-03-28)

参考文献数

18

被引用文献数

2 3

---

Finite difference method in a collocated grid system has the merits of both regular and staggered grid systems, and has mainly been used for steady flow simulations. Recently, some unsteady flows have been simulated by using the collocated grid system. The author pointed out a violation of kinetic energy conservation in the collocated grid system, which is important to unsteady turbulent flow simulations. In this paper, a modified algorithm for improving the conservation property of the collcated grid system is proposed. Van Kan type pressure correction is introduced to minimize the defect. The modified algorithm with fourth order accuracy in space is also proposed. Conservation properties of the numerical algorithms in the collocated grid system are demonstrated on the example of two dimensional periodic inviscid flow simulations. Plane turbulent channel flow simulations are also performed to confirm the reliavility of the modified algorithm.

著者

阿部 裕幸 筒井 康賢 吉識 晴夫

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.59, no.567, pp.3388-3392, 1993-11-25 (Released:2008-03-28)

参考文献数

9

被引用文献数

1

---

The Agency of Industrial Science and Technology, Ministry of International Trade and Industry has been researching and developing three types of 300kW ceramic gas turbines since 1988. The turbine blade's Reynolds numbers based on the basic design are predicted to be in the region of l04∼105. In the field of wind turbines, for example, some studies on the characteristics of airfoils at low Reynolds numbers have been carried out. However, it is not yet obvious how the turbulence affects the characteristics of airfoils. This paper describes the experimental results obtained with use of turbulence screens. It is found that laminar seperated flows, in some cases, reattaches to airfoils by raising turbulence intensity of free stream at Reynolds numbers of 0.5×105 and 1×105, and that lift to drag ratios increase further.