Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 1969"
TL;DR: In this paper, an experiment was carried out on the flow around a dual jet which is issued from two parallel slot nozzles set on a common end wall and is mixed turbulently with the ambient air.
Abstract: An experiment was carried out on the flow around a dual jet which is issued from two parallel slot nozzles set on a common end wall and is mixed turbulently with the ambient air. Distribution of cavity pressure, that of mean and fluctuating velocities, shape of the jets and cavity length were determined. From these measurements, the effect of distance between the nozzles on the flow field was studied and the following results were obtained : (1) Two jets attract each other and the axis of a jet coincides with an arc of a circle. (2) Except in the case of small distance between two nozzles, the radius of the jet axis and the cavity length increase in proportion to the nozzle distance. (3) Except in the region near the nozzle and the junction of two jets, momentum flux of the jet in flow direction is conserved.
132 citations
TL;DR: In this article, a retainer is used to bound a number of thin wires into a bundle so that each end of wire, which will be a surface element of an expected contour, may be pushed in with an ultrasonic vibrator to be located at a desired position.
Abstract: This paper treats with a newly developed technique to fabricate complicated dies for press work and electrodes for electrolytic machining, which is characterized by high productivity, low cost and extreme simplicity. A number of thin wires are bound together by a retainer into a bundle so that each end of wire, which will be a surface element of an expected contour, may be pushed in with an ultrasonic vibrator to be located at a desired position. The positioning of each wire end can be controlled by utilizing a numerically controlled milling machine for instance, and the accuracy of the positioning is in the order of 5/100 mm. As the die surfaces which are constituted by a number of wire ends are not smooth, a rubber sheet is inserted between the blank and the die so that the surface of the blank may not be scratched. In electrolytic machining with a wire electrode, the surface of the product is as smooth as the one with an ordinary electrode, if the diameter of wires is less than 0.5 mm.
67 citations
TL;DR: In this article, an analysis of the effects of buoyancy forces in laminar forced-convection on a vertical flat plate is made, and an approximate similarity solution is given by introducing the assumption that a role of Gr/Re2 in stream function is negligibly small as compared with η.
Abstract: An analysis is made for the effects of buoyancy forces in laminar forced-convection on a vertical flat plate. In general, since it is difficult to obtain an exact solution, an approximate similarity solution is given by introducing the assumption that a role of Gr/Re2 in stream function, [numerical formula] is negligibly small as compared with η. The validity of this assumption is examined by comparing with the experimental data of Kliegel. Numerical calculations are performed for both the constant fluid properties and the variable fluid properties, and the results are compared with Szewczyk's solution previously obtained by perturbation analysis. The velocity and temperature distribution, the friction factor and heat transfer coefficient are given for various values of the parameter Gr/Re2.
60 citations
TL;DR: In this article, the authors analyzed the dynamic characteristics of the self-damped air spring on the basis of the linear theory from the standpoint of the design of air suspension bogies.
Abstract: In this paper, at first the authors analyze the dynamic characteristics of the self-damped air spring on the basis of the linear theory from the standpoint of the design of air suspension bogies. The equivalent mechanical model of the self-damped air spring is obtained, which is a kind of socalled elastically supported damper systems, and the relationship among the elements of the model and the design parameters of the air spring are given. Then, using the mechanical model, both natural vibration and transient response of the air suspension bogie are analyzed numerically. As the result, it is shown that the natural frequency and the damping ratio of the self-damped air suspension bogie scarcely vary with the car body weight, and the self-damped air suspension can reduce the magnitude of the transient response compared with a conventional mechanical suspension with oil-dampers.
47 citations
TL;DR: In this article, a three-dimensional solution for the stresses and deformations arising in a semi-infinite body with a spherical cavity stressed at infinity is presented, which is based on the Boussinesq's stress-function approach referred to the cylindrical and spherical co-ordinates.
Abstract: This paper contains a three-dimensional solution for the stresses and deformations arising in a semi-infinite body with a spherical cavity stressed at infinity.Formerly, such a problem approached by means of spherical dipolar co-ordinates. The method used here is based on the Boussinesq's stress-function approach referred to the cylindrical and spherical co-ordinates.The problem can be reduced to one in two simply connected domains, i.e., a semi-infinite region and an infinite region excluding the cavity. The two stress functions in each region are given by simple expressions of the cylindrical and spherical harmonics.The boundary conditions on the face of the semi-infinite body and the surface of the cavity are satisfied by the relations between the cylindrical and spherical harmonics.Numerical results are given for six different radii of the cavity.
40 citations
TL;DR: In this article, the effects of tube diameter on the propagation behavior of a shock front were investigated by using two shock tubes with different sizes and by comparing with the other data, and various factors influencing the opening time of the diaphragm and the shock formation distance were discussed and the functional relations between these factors were clarified using the dimensional analysis.
Abstract: The effects of tube diameter on the propagation behavior of a shock front were investigated by using two shock tubes with different sizes and by comparing with the other data. The process of the formation of a shock front when the diaphragm was ruptured was observed by schlieren method. From this experiment, it was found that the observed shock Mach numbers were larger than the values obtained by the simple theory. Such result depends on the opening time of the diaphragm and the diameter of the tube. Therefore, the various factors influencing the opening time of the diaphragm and the shock formation distance were discussed and the functional relations between these factors were clarified using the dimensional analysis. The expression for the shock formation distance derived by the dimensional analysis was in satisfactory agreement with the experimental results.
35 citations
TL;DR: In this article, local void fractions averaged with time were measured above and adjacent to a horizontal heating surface in saturated pool boiling of water at atmospheric pressure, and an explanation about relationship of mechanism among three boiling regions can be derived.
Abstract: Local void fractions averaged with time were measured above and adjacent to a horizontal heating surface in saturated pool boiling of water at atmospheric pressure. Measurements were performed by the"Probe Method"previously developed by authors. Main results are as follows : (1) Characteristic changes of void fraction distribution occur below a height of 4 mm. (2) An explanation about relationship of mechanism among three boiling regions can be derived. (3) In nucleate boiling, the distribution curves versus height have a peak near the heating surface. However, there is a liquid-rich layer under the peak, and the layer is considered as the region which governs heat transfer. (4) Void fractions over 90% were measured at a height of 0.3∼1.0 mm near the condition of the burn-out point. (5) In transition boiling, liquid is in contact with the heating surface. (6) In our experiment on film boiling, the minimum film thickness is very little.
34 citations
TL;DR: In this paper, the mean kinetic frictional coefficient of the "stick slip" motion in a machine tool slidingeway was investigated. And the relationship between the static and kinetic friction in the "slip" period was examined.
Abstract: The properties of the "stick slip" motion occuring in the machine tool slideway are closely connected with the characteristics both in static and kinetic friction. In a previous paper, the static friction in the "stick" period was investigated. It has been shown in this paper that the characteristics of kinetic friction in the "slip" period can be examined collectively using the mean kinetic frictional coefficient μm in this period, and that the main factors which affect μm are the static frictional coefficient at the beginning of the "slip" motion and the time of the "slip" period. As a result, an expression for μm is proposed. Then, basing on the expressions for static and kinetic friction, the boundary conditions for occurrence of the "stick slip" motion are clarified, and the relation between properties of the "stick slip" motion and frictional characteristics is examined quantitatively.
31 citations
TL;DR: In this paper, the effect of system pressure on the growth characteristics of an isolated vapor bubble was investigated experimentally using water, ethanol and carbon-tetrachloride, and the Jakob number was varied between 0.34 and 1040.
Abstract: The effect of system pressure upon the growth characteristics of an isolated vapor bubble was investigated experimentally using water, ethanol and carbon-tetrachloride. The Jakob number was varied between 0.34 and 1040. It was found that with an increasing pressure the growth rate tends to be smaller, while in low pressure region the growth exponent happens to exceed 0.5. The model of evaporation of a thin liquid layer beneath the bubble was examined, which turned out to be successful for the explanation of the experimental facts.
30 citations
TL;DR: In this paper, the vibrations of a cylindrical shell of which one end is built-in and the other is combined to a circular plate or of which both ends are combined to circular plates are studied.
Abstract: The vibrations of a cylindrical shell of which one end is built-in and the other is combined to a circular plate or of which both ends are combined to circular plates are studies. The displacements of a circular plate and a cylindrical shell which is built-in at one end are shown in graphs. The distribution of the bending moment in this cylindrical shell is also shown.
30 citations
TL;DR: In this article, the bending and twisting fretting fatigue tests of carbon steels are carried out and the effects of cycle frequency are studied in comparison with the corrosion fatigue, which shows that the fretting damage is attributed to cracks initiated under the frictional stresses at the initial stage simultaneously applied with the repeated stresses in the surface layers.
Abstract: The bending and twisting fretting fatigue tests of carbon steels are carried out and the effects of cycle frequency are studied in comparison with the corrosion fatigue. The behaviors of the frictional force with progress of fretting cycles are observed. The results obtained are as follows : The fretting fatigue strength is decreased with lower frequency. The fretting damage is saturated in the early period of the total fatigue life, and the subsequent crack propagation period constitutes the most part of the life. The lower the frequency is, the shorter the saturation period. The frictional force increases initially and then decreases after showing a peak value. These changes at various frequencies well correspond to the extents of the fretting damage. Consequently, this shows that the fretting damage is attributed to cracks initiated under the frictional stresses at the initial stage simultaneously applied with the repeated stresses in the surface layers. The fretting corrosion without the repeated stresses hardly reduces the fatigue strength though the depth of wear scars is the same as that under fretting fatigue. The greater reduction of the fatigue strength by fretting under bending than under twisting may be also explained with the combined stresses.
TL;DR: In this paper, a study was made of surface roughness effects on dry friction between two metals, assuming that the asperities are cones of slopes which depend on the surface Roughness, and a comparison of calculated values based on this theory with experimental data showed good agreement.
Abstract: A study was made of surface roughness effects on dry friction between two metals, assuming that the asperities are cones of slopes which depend on the surface roughness. Theoretical expressions were derived for ploughing, adhesion and total friction coefficients of cones, spheres and aquare pyramids ploughing along the soft metal surface. A comparison of calculated values based on this theory with experimental data shows good agreement. Moreover, theoretical discussion was made of surface roughness effects on dry friction on the basis of the analysis of mechanism of abrasive friction. The theoretical estimation of the coefficient of friction between two metal surfaces can be carried out using the relations between the surface roughness and the slope of the asperities, and the coefficient of friction due to the adhesion at the interface. The experiments also showed that the maximum displacement between two metal surfaces in contact before gross sliding occurs, increases with an increase of the surface roughness.
TL;DR: In this paper, the boundary layer theory was applied to the flow in the clearances between valves and valve-seats, thence pressure integrals were calculated, and developed formulae were different whether the flow was laminar or turbulent.
Abstract: Analysis and experiments were performed to study the static characteristics of the thrust of poppet valves. Valves with cone angles between 40 degrees and 90 degrees were tested under different conditions. Experimental result reveals the momentum theory is valid for the estimation of the thrust. For poppet valves having lappings with valve seats, pressure integrals on the seats are required for the estimation of the thrusts. The boundary layer theory was applied to the flow in the clearances between valves and valve-seats, thence pressure integrals were calculated. Developed formulae were different whether the flow was laminar or turbulent. Thrust coefficient in the transition region lay between two calculated values, hence only rough estimation was thought possible. In the regions considered laminar or turbulent, analytical results coincided fairly well with experimental results.
TL;DR: In this paper, the statistical characteristics of static pressure pulsation in upward air-water flow through a smooth tube of 26.0 mm I. D. and 5.2 m long are analyzed.
Abstract: An analysis on the statistical characteristics of static pressure pulsation in upward air-water flow through a smooth tube of 26.0 mm I. D. and 5.2 m long is made to have a correct understanding of the essentials of two-phase gas-liquid flow. The pulsating pressure is detected at five different locations along the tube and recorded simultaneously on an oscillograph paper. Using these data, the statistical properties such as the standard deviation, frequency function and spectral density of pulsating pressure are calculated. These are discussed with the particular emphasis on the relationship with the flow rates of both phases and the flow patterns.
TL;DR: In this article, the relation between the surface roughness, the apparent contact area and the initial separation which is the distance between two median planes of surface in the beginning of contact is obtained theoretically.
Abstract: Assuming that the distribution curve obtained from the profile curve of the surface has a normal distribution, the relation between the surface roughness, the apparent contact area and the initial separation which is the distance between two median planes of surface in the beginning of contact is obtained theoretically. If the asperities are cones of the slopes which depend on the surface roughness, the relation between the distributions of slopes of cones and of slopes of small facets measured manually with a protractor on the profile curve is also deduced theoretically. The results of the theoretical analyses are compared with the experimental results for the initial separation and the distribution of slopes of facets on the profile curve. Results seem to support the plausibility of the proposed theory. Moreover this plausibility shows the possibility estimating the effects of the surface roughness and the apparent contact area of end faces of an object by length measurement.
TL;DR: In this article, a numerical method of finite difference was used to solve the problem of heat convection fields in the entrance region of a heated vertical circular tube, in which the temperature and velocity profiles were developing simultaneously.
Abstract: Pure natural heat convection fields in the entrance region of a heated vertical circular tube, in which the temperature and velocity profiles were developing simultaneously, were solved by a numerical method of finite difference. And then the characteristics of heat transfer were obtained. The analysis presented here was based on the assumption that the inlet velocity profile is uniform. It was verified analytically and numerically that, for the case of uniform wall temperature, the inlet velocity U1 has an asymptotic value 1/8 as the tube length approaches infinity. As for the case of uniform heat flux at the wall, U1 is directly proportional to √(L/p)r over the range L>Le, where Le is the entrance length. The relationship between the dimensionless pipe length L and dimensionless suction velocity U1 was also obtained, using Pr=0.72, for both the wall conditios. In the case that the pipe length is semi-infinite and the wall temperature is uniform, a relationship between Pr and thermal, as well as hydrodynamic, entrance length was obtained for Pr=0.01, 0.1, 0.72, 1.0, 10 and 100, and some interesting irregularities of developing velocity profiles were also observed except for the case Pr=1.0.
TL;DR: In this paper, three different experiments on the cylinder vibration caused by the wake force are undertaken, and it is concluded that the exciting mechanism is a selfinduced vibration, i.e., the cylinder vibrations itself under the special flow velocity, say, the nondimensional velocity of about 5.
Abstract: In this investigation three different experiments on the cylinder vibration caused by the wake force are undertaken. Namely, in the first place on the elastically supported cylinder in a wind tunnel and in the second place on the oscillated cylinder in a model basin experimental studies are undertaken. And in the third place on the oscillated cylinder in a wind tunnel an experimental research is made in which a fluctuating pressure on the cylinder surface is measured. According to these experimental results it is concluded that the exciting mechanism is a selfinduced vibration. In other words the exciting force is caused by the cylinder vibration itself under the special flow velocity, say, the nondimensional velocity of about 5. In addition, the theoretical analysis under this consideration is shown to be able to explain these test results well.
TL;DR: In this article, a multi-stage model was presented to explain the mechanism of the shock formation in a simple shock tube, which improved White's theory, and some numerical calculations were carried out.
Abstract: To explain the mechanism of the shock formation in a simple shock tube, the multi-stage model was presented, which improved White's theory, and some numerical calculations were carried out. Simple and White's theories correspond respectively to the case of zero or one stage of the present multi-stage model. The shock Mach number calculated by the multi-stage model is always larger than that obtained by the White's model. The difference between them becomes large as the diaphragm pressure ratio increases. Further in order to express the variation of the shock Mach number along the tube a function II (x) was proposed. By using this function, the phenomenon that shocks stronger than that predicted by the simple theory would possibly happen was discussed.
TL;DR: In this paper, the burning characteristics of a fuel drop in heated and pressurized air stream were studied experimentally, and the results concerning the influence of temperature and pressure are as follows: when the temperature is raised, the flame becomes long and the soot formation increases.
Abstract: As a clue to elucidating the combustion process in diesel engines, the burning characteristics of a fuel drop in heated and pressurized air stream was studied experimentally. Its pressure was varied from 0.4 to 16 ata, its temperature, from the room temperature to 600°C, and its velocity, up to the transition velocity where the flame shape changes from envelope type to wake type. The fuel drops were simulated by porous spheres transpired liquid fuel. As the fuel, methanol, n-butanol and kerosene were used. Under these conditions, the flame shape, the burning rate m, and the flame transition air velocity Uc were measured. Among the results of measurement, main ones concerning the influence of temperature and pressure are as follows. When the temperature is raised, Uc rapidly icnraeses, but m scarcely changes. When the pressure is raised with the velocity, m increases remarkably. And when the temperature and the pressure are raised, flame becomes long and the soot formation increases.
TL;DR: In this paper, the results of the experimental study of loss and secondary circulation due to various combinations of commercial elbows were discussed, and the relationship between the loss and the circulation was discussed, where the two elbows produced a complete reversal in the direction of flow.
Abstract: This paper gives the results of the experimental study of loss and secondary circulation due to various combinations of commercial elbows, and discussed the relationship between the loss and the circulation. Three general combinations are ; One where the two elbows produce a complete reversal in the direction of flow, termed the"U"bend ; and two where the two elbows produce an offset but no change in direction, termed the"S"bend ; and three where the two elbows produce both an offset and a 90 degree change in the direction of flow, termed the"twisted S"bend. The last combination gives rise to a strong single spiral motion in the straight pipe of curved pipes downstream and shows the maximum bend loss.
TL;DR: In this article, the spectroscopic analyses of the radiation from the luminous flame of the liquid fuel and the gaseous fuel were carried out in the wavelength range from 1.5μ to 5.4μ.
Abstract: The spectroscopic analyses of the radiation from the luminous flame of the liquid fuel and the gaseous fuel were carried out in the wavelength range from 1.5μ to 5.4μ, and the monochromatic infrared spectra of the radiation from the soot particle cloud were measured. The results obtained are as follows. The radiation from the soot particle cloud in the luminous flame is a continuous spectrum like the one from solid surface and not a band spectrum. The radiation from the luminous flame is composed of band spectra of the gas and a continuous spectrum of the soot particles. The high emissivity of the soot particle cloud is caused by the high continuous spectrum. The monochromatic absorption coefficients of the soot particle clouds obtained in this experiment differ from the theoretical values but the effects of the size distributions upon the monochromatic absorption coefficients agree well with each other. The relation between the effective emission thickness and the total emissivity of the soot particle cloud which is calculated from the present monochromatic emissivity agrees very well with the author's previous result obtained using radiation pyrometer.
TL;DR: In this article, the authors studied the flow characteristics of water through right-angled pipe fittings by theoretical and experimental method, by means of the theory of two-dimensional potential flow, streamlines and pressure distributions along the walls of right-angle branching canals, in which the flow separated at the branch corner.
Abstract: The flow characteristics of water through right-angled pipe fittings were studied by theoretical and experimental method. By means of the theory of two-dimensional potential flow, streamlines and pressure distributions along the walls of right-angled branching canals, in which the flow separated at the branch corner, were evaluated and compared with the experimental results. Both results coincided very well. From the calculated and experimental results, the mechanisms of the pressure loss of right-angled pipe fittings were analyzed. The pressure loss in the main flow was equivalent to the pressure loss of a sudden enlargement and that in the branch flow to the sum of the pressure loss of a sudden contraction and a sudden enlargement.
TL;DR: In this paper, rotating bending and torsional fatigue tests of plain and notched steel specimens with electropolished surfaces were carried out, and the main results obtained are as follows.
Abstract: Rotating bending and torsional fatigue tests of plain and notched steel specimens with electropolished surfaces were carried out. The main results obtained are as follows. (1) The maximum shear stresses in the crack initiation limit of torsional fatigue are determined only by the stress gradient X independently of the notch depth as in the case of bending fatigue. (2) When the values of X are equal, the maximum shear stress in the crack initiation limit of torsional fatigue is about 1.2 times that of bending fatigue. (3) The surface states of notch roots after 107 cycles of the limit stress for crack initiation in torsional fatigue are similar to each other irrespective of the maximum stress repeated on the notch root, as in the case of bending fatigue. The fatigue damages at the crack initiation limit under torsional stresses are severer than the ones under bending stresses. (4) The mechanism of non-propagation of a crack in torsional notched specimens is different from that in bending notched specimens.
TL;DR: In this paper, the relation between pressure drop and a few parameters, such as rotating Reynolds number, axial-flow Reynolds number and eccentricity ratio, is investigated experimentally in connection with the development of Taylor vortices.
Abstract: We previously investigated the pressure drop in an annulus with a rotating inner cylinder under fully developed conditions and reported that there is a noticeable increase in axial resistance associated with the onset of Taylor vortices for laminar flow of axial-flow Reynolds number above 100. On the other hand, in the case with no axial flow, it has been reported that the flow between eccentric cylinders with a rotating inner cylinder is more stable to the disturbance of Taylor vortex type than the flow between concentric cylinders. However there is no investigation of axial resistance connected with the development of Taylor vortices in the flow between eccentric rotating cylinders with axial flow. We measured the pressure drop in the eccentric annulus with a rotating inner cylinder under fully developed conditions, using water and glycerine-water solutions. And in this paper the relation between pressure drop and a few parameters, such as rotating Reynolds number, axial-flow Reynolds number, eccentricity ratio and clearance ratio, is investigated experimentally in connection with the development of Taylor vortices.
TL;DR: In this article, a capillary viscometer was used in the closed circuit system with a high pressure injector and a mercury manometer to investigate the viscosity of water and steam in a wide range of temperatures up to 900°C and of pressures up to 1000 bar.
Abstract: Viscosity of water and steam was experimentally investigated in a wide range of temperatures up to 900°C and of pressures up to 1000 bar. In this investigation, a capillary viscometer was used in the closed circuit system with a high pressure injector and a mercury manometer. Measured results are compared with the standard values of the ICPS Skeleton Table (1964), and with experimental values of other investigations. A newly correlated equation represents experimental results within about 2% deviations.
TL;DR: In this paper, it was shown that the static force proportional to displacement of a poppet valve is strongly influenced by the pressure between a valve and its seat and that the dynamic force proportionally to its velocity is effected by squeezing out fluid and also by the time rate of change of momentum of fluid.
Abstract: This paper treats the self-excited lateral vibration of a poppet valve. It is shown that the static force proportional to displacement of a valve is strongly influenced by the pressure between a valve and its seat and that the dynamic force proportional to its velocity is effected by squeezing out fluid between a valve and its seat and also by the time rate of change of momentum of fluid. The effect of squeezing out fluid has a positive damping, while the time rate of change of momentum of fluid has a negative damping. Therefore, the self-excited lateral vibration of a valve occurs, when the latter damping becomes larger than the former.
TL;DR: In this paper, the authors describe an experimental study on the distributions of local void fraction along a cross section of a vertical channel in fully developed air-water two-phase flow at atmospheric presure, using a probe method.
Abstract: The present report describes an experimental study on the distributions of local void fraction along a cross section of a vertical channel in fully developed air-water two-phase flow at atmospheric presure, using a probe method. In bubble flow, a peculiar distribution which was fundamentally different from a power law distribution accepted in previous studies was observed. It had a peak of void fraction near the wall. The position of the maximum void fraction was at (0.5∼0.7)d from the wall where d was a bubble major axis. The authors proposed an empirical formula which was in good agreement with the present and another experimental results and applicable not only to bubble flow but also to slug flow. Comparisons between this formula and previous formulas were made in the experimental results.