Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 1971"

Experimental Study on Structure of Gas Flow in Tube Banks with Tube Axes Normal to Flow : Part 1, Karman Vortex Flow from Two Tubes at Various Spacings

Abstract: A gas flow in and behind tube banks with tuber axes normal to the gas flow is highly turbulent containing numerous vortices of different sizes and intensities. Each vortex in this complicated wake is the result of a periodic generation, and the periodicity sometimes induces serious vibration problems in steam generators and heat exchangers. The structure of the flow may be treated ass a complex synthesized result of Karman vortex flow. This paper is the first report of a series of studies carried out form the above mentioned viewpoint, and presents the experimental results about a Karman vortex flow from two tubes at various spacings. The vortex formation region was visualized by means of the Schlieren method and was recorded by a 16mm movie camera. The vortex shedding frequency was systematically studied. The frequency for two tubes is entirely different from that for a single tube. It was found that the size of the vortex formation domain has a dominant effect on the frequency.

On the Roughening of Free Surface in Deformation Processes

Abstract: Conditions governing the roughening phenomenon of free surface in deformation processes are investigated. It is shown that the surface roughness increases with strain, and the roughening rate is affected by the mode of deformation (tension and compression), and by the position of the surface. The effects of the deformation mode and the position of the surface are related with change of the surface area during deformation. It is also found that the roughening rate is affected by grain size and the lattice structure of the metal, i.e. the roughening is remarkable in the metal of large grain size and of small number of slip systems. Wave length of the roughness is about 10 times as large as the grain size. Theoretical analysis of the wave length is carried out on the basis of probability.

Computer Controlled Bilateral Manipulator

Abstract: Computer control of an artificial hand which is incorporated with the tactile sense and force reflection is studied. In this experimental system, a digital computer is linked to the analog-type position-servomechanisms of the artificial hand using D/A and A/D converters, so that the position references can be changed repeatedly in the direction of decreasing the measured error signals. To deal with the versatility of the operation, the software system consists of a supervisory program and many basic program modules which correspond to respective basic manipulations. Furthermore, a symbolic command language which is adequate for such a purpose is prepared. It has been shown that the greatest difficulties in carrying out the complex and dexterous manipulations such as inserting a pin into a hole, turning a crank, etc., are solved by introducing the concept of bilateral servomechanism into the programming of the control computer.

Hydrodynamics and Heat Transfer of Vertical Falling Liquid Films : Part 1, Classification of Flow Regimes

Abstract: Hydrodynamics of a vertical falling liquid film has been the subject of not a few papers in which the film is analyzed in the same way as in the single phase flow without a free surface. A study for improving this situation is reported in a series of papers including this one on an experimental study on the wavy flow of falling films of water and highly viscous fluids. By analyzing the experimental study it is concluded that the flow of a vertical falling liquid film is classified as follows. 1. Purely laminar flow ; there is no wavy motion on the liquid film. 2. First transition region. 3. Stable wavy flow ; there are stable wavy motions on the liquid film in which turbulence is found. 4. Second transition region. 5. Fully turbulent low ; the flow becomes shear-flow type, and its wall law is identical with that of the turbulent boundary layer.

Study on Distribution of Flow Rates and Flow Stabilities in Parallel Long Evaporators

Abstract: Distributions of flow rates and flow stabilities in parallel evaporator tube systems have been experimentally investigated. The evaporator is composed of three parallel copper tubes of 4mm inside diameter and 40 m long. Experiments were carried out by using refrigerant R-113 as the fluid in pressure range from atmospheric pressure to supercritical pressure, in order to simulate phenomena in steam generators. It has been shown that distributions of flow rates, their hysterisis and onset of excursion phenomena can be estimated from pressure drop versus flow rate curves for single tubes. Moreover, description is made of behaviors of thermal oscillative instability which are observed at relatively low flow rate. In addition to the experimental results, by a theoretical analysis of a simple model, stability criteria in parallel tube system have been described.

Study On a Gas-Liquid Two-Phase Flow in Helically Coiled Tubes

Abstract: In this paper the frictional pressure drop, void fraction and flow pattern of an air-water two-phase flow in helically coiled tubes are presented. The coils are constructed of 9.92 mm I.D. copper tube and the ratios of inside diameter to coil diameter are 1/11 and 1/22.7, and the lengths are 4 m and 4.5 m respectively. The experiments were conducted in the range of superficial water velocity wlo: 0.35∼1.16 m/sec and superficial air velocity wgo: 0∼5 m/sec. The frictional pressure drop of the two-phase flow in these coils is 1.1 to 1.5 times as much as that in a straight tube in the range of the experiment. Three types of empirical equations for the frictional pressure drop are proposed, and also the experimental data are correlated by a modified Lockhart-Martinelli method. The values of void fraction in the coils are approximately equal to those in a straight tube for the same water and air flow rates.

Application Bulletin of the JSME of Finite-Element Method to Hydrodynamic Lubrication Problems : Part 1, Infinite-Width Bearings

Abstract: Few papers which applied the finite-element method to hydrodynamic lubrication have been published, in spite of many literatures introducing the finite-element method in structural problems. In this paper, the applications of the finite-element method for hydrodynamic lubrication of infinite-width bearings are presented. It is claimed that the finite-element method is able to obtain the accurate results by using a few elements. The finite-element solution is compared with an exact solution and a finite-difference solution of step bearings, plane slider learnings and journal bearings.

Upward Liquid Flow in Small Tube into which Air Streams : 1st Report, Experimental Apparatus and Flow Patterns

Abstract: In the main fuel pipe (main nozzle) of the carburetor of gasoline engine, a little air is let into the fuel stream, in general. This two-phase flow streams into the venturi-tube. The author's experiments are made with simple models to elucidate the basic phenomena of the confluence of air and fuel in a small tube, that is, the flow pattern of a two-phase flow, the pressure drop caused by the confluence, the two-phase flow friction, and the relaxation oscillation. In 1st Report, experimental apparatus and flow pattern are described. Vertical tubes are 6, 3, 2 mm of diameter. Liquid is tap water in the most part of experiments, and in some part of them, is distilled water, gasoline, solvent, or surface active agents solution, Unless the air holes are large, stable fish-scale type slug flow appears in some range of air and liquid. This is attributed not to the effect of so-called entrance length but to that of the small diameter of tube.

Experimental Study on the Mechanism of Transition Boiling Heat Transfer : 1st Report, Measurements of Local Solid-Liquid Contact and Temperature Fluctuations on the Heating Surface

Abstract: Measurement of solid-liquid contact and surface temperature fluctuations is conducted in case of nucleate and transition boiling of water on the horizontal copper surface of 8 mm diameter. From these measurements it is inferred that the mechanism of transition boiling is closely related to the behavior of vapor bubbles. The results obtained from the analysis of surface temperature records are as follows. (1) Transition boiling is distinguished by intermittent solid-liquid contact and the fluctuation of heat flux corresponding to the periodic departure of vapor bubbles from heating surface. (2) Local time rate of solid-liquid contact, which is smallest at the center of heating surface and largest at he circumference, decreases rapidly with the increase of wall superheat. (3) Transition boiling heat transfer can be explained as the coexistence of nucleate boiling heat transfer in the solid-liquid contact part and film boiling heat transfer in the solid-vapor contact part.

Flexural Vibrations of a Ring with Arbitrary Cross Section

Abstract: The paper deals with the flexural vibrations of a ring with arbitrary cross section and proposes an approximate theory to predict the natural frequencies by means of the Ritz's method. The frequency determinant is derived from the Hamiltonian principle by use of the stress-strain-displacement relations of three-dimensional theory of elasticity, and by expanding three components of the displacement in a finite double power series of the radial and axial coordinates with unknown coefficients. Compared with the experimental results for twenty three kinds of rings which are classified into six sets with respect to the cross section, the theory was ascertained to be available for the practical use. Furthermore, as an application to a general axi-symmetric elastic solid with free boundary surface, the frequencies of truncated conical shells and combined shells of hemispherical and circular cylindrical shells were calculated and compared with the already-known results, showing a good agreement between them.

On the Running Noise of Toothed Belt Drive : 1st Report, Mechanism of Noise Generation

Abstract: As the first step to find the noise reduction methods for toothed belt drive, the authors investigated the characteristics of the noise and its generating mechanism experimentally. The results obtained are as follows: (1) In general running condition the impact sound which is generated periodically with tooth meshing frequency is the most powerful component in the noise. And it was ascertained that the impact sound is caused by the collision of tooth tips of the driving wheel against bottom lands of the toothed belt. (2) When the belt tension is large enough the transverse vibration (string vibration) of belt resonates badly with the meshing frequency and this resonant sound sway the noise level. (3) In a case where both impact and resonant sound are not predominant, the toothed belt drive runs silent enough.

Deep Drawing of Circular Sheet Metals with Rubber Rings : 1st Report, The Case of First Drawing Operation

Abstract: The drawing limits of mind steel and aluminum sheets were examined for the case of repeated drawing operations in which the blank was deformed incrementally as the rubber ring was repeatedly loaded and unloaded. The drawing condition used was base on the optimum one for the first drawing operation clarified in our 1st report. The obtained drawing ratio was 2 for mild steel, 3 for hard aluminum and 6 for half-hard and soft aluminums. When the work hardening of the blank was diminished by intermediated annealings, a maximum drawing ratio of 12 was achieved for soft aluminum. The strain distribution, shape and a surface roughness of drawn cups were also examined. Furthermore, the relation between the height of the drawn cup and the number of drawing operations was discussed for the case of using either a vulcanized natural rubber or a polyurethane ring and was compared with the data reported by N. A. Maslennikov.

A Study on Surging Phenomena in Diesel Engine Air-Charging System

Abstract: Pulsating air flow in a diesel engine air-charging system caused by the opening and closing of the scavenging ports produces surging phenomena which are considerably different in their characteristics from those observed in the ordinary, steady flow blower system. By substituting a simple model for the engine air-charging system, the authors analyzed the surging phenomena through theoretical calculations and determined the effects of each model element on the surging. A series of experiments were then made to verify the validity of the analytical calculation method adopted. A good agreement was observed between the results of calculations and experiments, and it was found that a simplified theoretical calculation neglecting the influence of the pressure waves in the air duct of the air-charging system could serve as an effective means to deal with the surging phenomena where the air duct was comparatively short in length as that of the diesel engine.

Correlation between the Fatigue Limit of a Material with Defects and Its Non-Propagating Crack : Some Considerations Based on the Bending or Torsional Fatigue of a Specimen with a Diametrical Hole

Abstract: From our experiments carried out about the bending and torsional fatigue of S35C specimens with a diametrical hole (each specimen has a round hole or its connected holes), the following results were obtained. 1) In the case of a specimen with a diametrical hole, the root radius of the notch at the branch point is constant (ρ0c0.5 mm in our material), as in the case of the bending fatigue test of the circumferential notched specimen. This means that the fatigue limit of the material with defects is mainly determined by the limit stress for propagation of its non-propagating crack. 2) when the fatigue limit of a specimen with a diametrical hole is determined by the crack strength (whenρ<ρ0), the fatigue limit is mainly dominated by the diametrical hole in the perpendicular direction of the maximum tensile stress. This means that the fatigue limit of a material with defects is more influenced by the size of defect than by the sharpness of defect. 3) It is case of a plain specimen, τw/σwc0.6; but in the case of the specimen with a diametrical hole, τw/σw=0.750.9. This shows that the effect of defect in the bending fatigue is greater than in the torsional fatigue.

Radial Force on the Impeller of a Centrifugal Pump

Abstract: Radial force of a centrifugal pump was measured, using a pump which had a device for measuring the radial force and a volute casing with an interchangeable tongue. The authors obtained some knowledge about the following items and discussed them: (1) The effect of the cross-sectional area and shape of volute tongue on the pump characteristic and radial force. (2) The characteristic of dynamic component of radial force. (3) The effect of cavitation on the radial force.

On the Running Noise of Toothed Belt Drive : 2nd Report, Influence of Running Condition and Some Noise Reduction Methods

Abstract: In this report the authors investigate the influence of the construction and the dimension of toothed belt and some running conditions on the noise of toothed belt drive, and show some running noise reduction methods and their effectiveness. The running noise level varies with belt speed, belt tension and polygon-effect of the wheel, but there is no difinite tendency between noise level and number of teeth and module of the wheel. The effective methods to reduce the meshing impact sound and to keep the toothed belt drive silent are: (1) to soften the bottom lands of toothed belt or the tooth tip lands of wheel, (2) to make belt width narrow, (3) to cant the belt of tension side with an idle pulley, (4) to make the wheel noncylindrical, especially as barreled-shape.

Studies on the Fluctuation of pressure Drop in Two-Phase Slug Flow : 1 st Report, Experimental Study

Abstract: Experimental and theoretical studies of the fluctuation of air-water two-phase slug flow in a vertical tube, have been described in three papers. Among them, the experimental results are presented in this paper. It was verified that the time variation of pressure drop is predicted by the variation of lengths of gas bubble and liquid slug flowing in the tube. It was also shown that the probability distribution of pressure drop in long segments of tube is normal distribution, and that in short segments, distribution has generally two peaks at Δp* (i.e., dimensionless pressure drop) =0 and 1. The maximum amplitude of the pressure drop was given by the following empirical equation δΔpmax*/Δpm*=0.7LT-0.62wl0-0.62wg00.9 where, δΔpmax* and Δpm* are the maximum amplitude and the mean value of dimensionless pressure drop, respectively; wl0 and wg0 superficial liquid and gas velocity, respectively; and LT is the length of segment of tube.

An Investigation on Ultrasonic Atomization

Abstract: The characteristics and mechanisms of ultrasonic atomization have been studied, using atomizers of the type applicable to practical oil burners. As a result, it has been found that the drop-size distribution is closely approximated by the Nukiyama-Tanasawa's distribution function, Eq. (1), when α=12 and β=1. The behavior of the mean diameter of droplets has been examined and summarized in the empirical relation, Eq. (9). In addition, it has been inferred that atomization is caused by the breakup of the capillary waves (frequency: f/2) which are formed in a liquid film spread over the vibrating surface, and that collision between droplets is one of the important factors affecting drop-size distribution and spray angle.

Studies on the Convective Heat Transfer from a Rotating Disk : 5th Report, Experiment on the Laminar Heat Transfer from a Rotating Isothermal Disk in a Uniform Forced Stream

Abstract: Pressure distributions on the disk surface and along the axis through the stagnation point have been measured. The settling place of rotating disk, the measuring point of velocity, and the dimensions of the disk model have been decided to refer well to the condition assumed in theoretical analysis. The results are summarized as follows. (1) The generalized experimental formulas which contained the effect of natural convection were established for the heat transfer from a rotating disk in the quiescent fluid and a stationary disk in the axial flow. (2) Experimental results in the presence of both rotating and axial stream velocities revealed good agreement with theory (2nd Report). (3) For the rotation alone, our results agreed with Cobb-Saunders and for the axial flow alone due to separation at the edge of the disk, Sogin's experimental data are about 17% larger than our results and theory.

On the Vibration of Cylinders Caused by Karman Vortex

Abstract: As bridges becomes larger in size, the members become slenderer and a severe vibration sometimes occurs in the cylinder members because of a Karman vortex caused by gentle winds. A lot of studies have already been conducted on this phenomenon, but there are still many unknown factors left about the behaviors of cylinders, qualititatively and quantitatively. In this study we carried out a few wind tunnel tests in the subcritical range and investigated the vibrating characteristics of the cylinder and the aerodynamic force working on the vibrating cylinder. The following facts were made clear. (1) The vibration of cylinders caused by Karman vortex is self-excited and the range of self-excited vibration is effected by the damping factor of the system. (2) Strouhal's number at the resonant condition reduces to 0.17 as vibrating amplitude increases. (3) Life coefficient at the resonant condition is effected by vibrating amplitude. In the case of the large amplitude, it can be arranged from the view-point of the forced vibration to some extent.

Researches on the Performance of the Regenerative Pump with Non-Radial Vanes : 1st Report, Performance and Inner Flow

Abstract: The pump has vanes which are inclined at an angle with the radius. Experiments were carried out on the performance in each of the combinations of eleven angles of vane from 45° to 135° with four flow channels. The authors also observed the inner flow by means of a high speed camera and a few kinds of probes which contained a new type pitot tube. Their conclusions are as follows : (1) The pump performances are influenced by the vane angle and the sectional area of flow channel. (2) The ratio of the shut-off heat to the head at the maximum efficiency and the maximum power decrease with the increase of the vane angle. (3) There is a regular flow circulating through the flow channel and between the vanes, and the flow pattern depends upon the vane angle.

A Comparison of the Axial and Reversed-Torsional Strain Cycling Low-Cycle Fatigue Strength of Several Structural Materials

Abstract: As a part of series investigation on the low-cycle fatigue properties under the multiaxial stress condition, low-cycle fatigue tests were conducted under axial and reversed-torsion strain cycling conditions. Two kinds of carbon steel, a Ni-Cr-Mo steel, a commercially pure aluminum, a 7075-T6 aluminum alloy, and cold-worked and annealed coppers were tested in this investigation. The equivalent plastic strain range based on the octahedral shear strain theory was used in comparing these axial and reversed-torsional results. In general fairly good agreement was observed between the two cycling results, although some discrepancies existed in the case of the carbon steels and the annealed copper investigated. Some amount of anisotropy was found in fracture ductility between the axial direction and the diametral direction of specimens. This might affect more the reversed-torsion results. For more precise correlation of the two cycling test results, therefore, the influence of the anisotropy as well as that of the crack propagation characteristics should be taken into consideration.

Correlation of Viscosity, Thermal Conductivity and Prandtl Number for Water and Steam as a Function of Temperature and Pressure

Abstract: In this report equations of viscosity, thermal conductivity and Prandtl number for water and steam were correlated as a function of temperature and pressure, while most of equation is previous investigations had been expressed as a function of temperature and density. Directly from values of temperature and pressure without knowing the value of density, property values can be calculated using equations in this report. Whole regions of up to 1000°C, 3500 bar for viscosity, up to 700°C, 500 bar for thermal conductivity and up to 600°C, 500 bar for Prandtl number are covered by three equations each, namely equations for the water, the steam and the critical regions. In the water and the steam regions those for the water, the steam and the critical regions. In the water and the steam regions those properties are expressed as the polynomials of pressure in two or three terms, while the narrow region near the critical point is expressed in a slightly more complicated form. Values calculated by the correlated equations were compared with the recent experimental values.

Effects of Probe Dimensions on the Ion Density Measurements in Combustion Gas Flows

Abstract: The effects of various parameters on the ion currents to Langmuir-type cylindrical probes of Pt or Pt/Rh alloy were studied experimentally. First of all, in very low ion density flows of pure combustion gases, the effects of the potential and the dimensions of the probe on the ion current were examined. In the case, an apparent increase in ion current due to thermal emission of electrons occurred when the surface temperature of a probe containing Rh became higher than 1 900°K. The sheath thickness around a probe seemed to be larger than 0.5 mm. Furthermore, experiments were conducted in combustion gas flows, the ion densities of which were increased with the addition of potassium. Besides the effects of the potential and the dimensions of the probe, those of the flow velocity and the ion density of the gas on the ion current were examined, and an empirical equation for the ion current was obtained.

A Study on the Hydraulic Loss of Tubular Coils

Abstract: A knowledge of the hydraulic resistance for tubular coils is required in connection with heat exchangers. Motion of liquid in curved tube coils is greatly influenced by their configurations, namely, by the ratio of radius of tube to radius of curvature of tube d/D1 and spiral pitch of the coils, and also Reynolds number Re. To investigate these effects, flexible vinyl tubes reinforced by steel wires were employed to facilitate the experiments and the hydraulic loss of curved tube coils was measured for 3.43≤D1/d≤51.2, 1.7°≤ pitch angle θ≤70°, and 1.3×103≤Re≤5×104. Flow patterns were also measured by a cylindrical Pitot tube. Except an extreme case of D1/d=3.43, the hydraulic loss of coiled tubes can be estimated by modifying the results on curved tubes in one plane.

Upward Liquid Flow in Small Tube Into which Air Streams : 2nd Report, Pressure Drop at the Confluence

Abstract: When air streams into a liquid flowing upward in a vertical small tube, two kinds of pressure drops occur ; that is, one is the pressure drop along the liquid stream line, and the other is that along the air stream line. After consideration of void fraction, a non-dimensional basic equation is obtained, using a simple model of confluence. For each flow pattern, semi-empirical equations of the former kind of pressure drops are obtained. An empirical equation which covers the whole region of flow pattern is obtained from these equations. An empirical equation of the latter kind of pressure drop which covers the whole region is also obtained.