Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 1981"
TL;DR: In this paper, the characteristics of the flow around two circular cylinders in a cross flow were investigated, and the dependence of the Reynolds number was recognized in the range of 1.1, 1.6, 2.3 and 3.0.
Abstract: Experimental investigations on the characteristics of the flow around two circular cylinders in a cross flow were carried out. Reynolds number was varied in the range of subcritical values, 8.7×103 <__= Re <__= 5.2×104 and the distance between the axes of the cylinders in the spacings 1.03 <__= Ld <__= 5.0, where d is the diameter of the cylinder. Up to the spacings of L/d=3.5, where the quasi-stationary vortices are formed between the cylinders, the changes of the flow structure around the two cylinders were observed at the spacings of L/d=1.1, 1.6, 2.3 and 3.1. Particularly, the dependency of the Reynolds number was recognized in the range of 1.1 <__= L/d <__= 2.0.
403 citations
TL;DR: In this paper, a visualization study has been conducted for the reattachment length and transition of the separated and reattached flow over blunt flat plates of finite thickness having various nose shapes over a Reynolds number range between about 40 and 2000.
Abstract: A visualization study has been conducted for the reattachment length and transition of the separated and reattached flow over blunt flat plates of finite thickness having various nose shapes over a Reynolds number range between about 40 and 2000. The reattachment length increases with an increase of the Reynolds number, reaches a maximum at a specific Reynolds number depending on the nose shape, and then decreases. The separated shear layer plays an important role on the characteristic variation of the reattachment length. Clarified is the transition Reynolds number at which the laminar separated shear layer exhibits an undulating motion before the reattachment point is reached.
65 citations
TL;DR: In this paper, the governing equations for a steady fully developed laminar flow in a helically coiled pipe are derived and the solutions are obtained for small values of a*/R*, where a* is the radius of the pipe cross-section and R * is the diameter of the circular cylinder on which the pipe center-line is helically coils.
Abstract: The governing equations for a steady fully developed laminar flow in a helically coiled pipe are derived and the solutions are obtained for small values of a*/R*, where a* is the radius of the pipe cross-section and R* is the radius of the circular cylinder on which the pipe center-line is helically coiled. The torsion of the pipe center-line causes asymmetry of the flow pattern in a pipe cross-section, an example which appears in the inclination of the flow pattern at large values of the parameter D1. Here, D1 = (C*a*3/ v*2ρ*)(2a*cos2β/R*)1/2, where C* is a costant pressure drop along the pipe center-line, v* is the kinematic viscosity, ρ* is the density of the fluid and β is a constant angle which the normal to the helix makes with the generating line of the cylinder. It is concluded that the resistance formula for a toroidally curved pipe is also applicable to a coiled pipe, if the curvature of the coiled pipe is used instead of that of the toroidally curved one.
42 citations
TL;DR: In this paper, an experimental investigation is carried out on a flow around a circular cylinder vertically mounted on a smooth plane wall along which a turbulent boundary layer is fully developed, and the pressure drag coefficient CD is found to be expressed in the form CD=a(h/δ)b, where δ is the thickness of the boundary layer and the values of a and b are dependent on h/λ 1.
Abstract: An experimental investigation is carried out on a flow around a circular cylinder vertically mounted on a smooth plane wall along which a turbulent boundary layer is fully developed. Pressure drag of the cylinder is correlated with the height h, the diameter d of the cylinder and the characteristics of the boundary layer. The pressure drag coefficient CD is found to be expressed in the form CD=a(h/δ)b, where δ is the thickness of the boundary layer and the values of a and b are dependent on h/δ. when h/δl 1. 1, a and b are linear functions of d/δ, while they are constant in the range h/δ> 1. 1.
41 citations
TL;DR: In this paper, an analytical study on the propagation of plane harmonic waves in an infinitely extended, cubi-anisotropic, elastic, and micropolar medium is presented.
Abstract: The authors start with an analytical study on the propagation of plane harmonic waves in an infinitely extended, cubi-anisotropic, elastic, and micropolar medium. It is possible to have six fundamental waves. Of these, a longitudinal uncoupled displacement wave and two coupled transverse waves of displacement and microrotation which become uncoupled with become uncoupled displacement waves at the limit of long wavelength are compared with the acoustical waves in the classical theory. The micropolar elastic constants of diamond, as well as its local moment of inertia, are estimated under the requirement that the theoretical dispersion curves for these waves fit the experimental data. Numerical computations are carried out and the results are made into a table.
38 citations
TL;DR: In this paper, the authors introduced four characteristic parameters defined for a pulsating turbulent pipe flow, and the pattern diagrams for pulsating laminar pipe flow were shown, where flow patterns were classified into three types, i.e., quasi-steady, intermediate, and inertia dominant ones with respect to the dimensionless frequency ω' and the limits between these three regions were determined.
Abstract: By introducing four characteristic parameters defined for a pulsating turbulent pipe flow, the pattern diagrams for a pulsating laminar pipe flow are shown. The flow patterns are classified into three types, i. e., quasi-steady, intermediate, and inertia dominant ones with respect to the dimensionless frequency ω' and the limits between these three regions are determined. An alternative analytical representation for wall shear stress τw including acceleration term and its approximation are proposed. Various approximate representations for τw reported previously or proposed here are compared with the analytical one by means of the four characteristic parameters and their applicability is examined.
37 citations
TL;DR: In this article, the performance of a supersonic air ejector in the case of zero-secondary flow was studied by varying the Mach number of the primary nozzle and the throat area ratio of the mixing tube to the primary.
Abstract: The performance of a supersonic air ejector in the case of zero-secondary flow was studied by varying the Mach number of the primary nozzle and the throat area ratio of the mixing tube to the primary nozzle. As the result, it has been shown that an optimum throat area ratio exists for each Mach number of the primary nozzle in which case the vacuum performance of the ejector becomes maximum with a minimum stagnation pressure of the primary flow. The physical meanings of the optimum throat area ratio and other ejector characteristics have been clarified from the results of pressure measurements and optical observations. Furthermore, modifying a previous method in the case of a constant-area mixing tube, the ejector performance was calculated for a variable-area mixing tube in the case of a larger throat area ratio than the optimum one. Calculated values agree well with the experimental results.
35 citations
TL;DR: In this paper, the root stresses of thin rim spur gears are investigated by means of the two-dimensionala1 finite element method (FEM) with triangular elements, and the effects of boundary constraints for gear models and of adjacent teeth on the root stress distribution are discussed.
Abstract: The root stresses of thin rim spur gears are investigated by means of the two-dimensiona1 finite element method (FEM) with triangular elements. The effects of boundary constraints for gear models and of adjacent teeth on the root stress distribution are discussed. The gear tooth model with a single tooth is shown to be available for a sufficiently precise evaluation of root stresses. A suitable rim thickness of gear model for the stress analysis by FEM is proposed. The true root stresses are computed and measured for gears of different rim thicknesses. The true stresses computed by FEM are in a fairly good agreement with measured ones. On the basis of these investigations the effects of rim thickness on the root stresses and on the critical sections in thin rim spur gears are also discussed.
33 citations
TL;DR: In this article, the effects of the upstream boundary layer on the pseudo-shock wave were investigated by varying the Mach number and boundary layer thickness upstream of a pseudo-shaking wave.
Abstract: Up to the present, two flow models for pseudo-shock waves have been presented, i.e. shockless model and diffusion model. However, since the effects of upstream boundary layer and wall friction in the pseudo-shock region are not considered in these models, the flow properties calculated by these models are identical with those by the theory of normal shock wave, and they are much different form experimental values. In the present study experiments have been performed to investigate the effects of the upstream boundary layer on the pseudo-shock waves, by varying the Mach number and boundary layer thickness upstream of the pseudo-shock. Based on the results and modifying the diffusion model, a new flow model of the pseudo-shock has been presented in which both effects of the upstream boundary layer and the wall friction are taken into account. Calculated values by this modified diffusion model agree better with the experimental values than the previous flow models.
32 citations
TL;DR: In this paper, the relationship between frictional losses and dimensionless frequency in an incompressible pulsating laminar pipe flow is investigated in terms of three kinds of friction factors.
Abstract: Relations between frictional losses and dimensionless frequency in an incompressible pulsating laminar pipe flow are investigated in terms of three kinds of friction factors. Furthermore, the frictional losses calculated from previously reported various approximate representations for wall shear stress are compared with those calculated from an analytical one in order to examine the validity of approximations. It becomes evident that the behaviours of instantaneous and time average friction factors in the quasi-steady, the intermediate, and the inertia dominant regions are qualitatively similar to those in a pulsating turbulent pipe flow and that the time average friction factor and the root mean square friction factor proposed here can be correlated to time-averaged cross-sectional mean viscous dissipation, while the instantaneous friction factor cannot represent the instantaneous cross-sectional mean viscous dissipation except for the quasi-steady region.
31 citations
TL;DR: In this article, a model of a circular cylindrical tank with a perfect fluid and the side wall of the tank as an elastic cylinder is presented. But the model is restricted to the axisymmetric case, and it is assumed that the tank bottom is rigid.
Abstract: Coupled oscillations of liquid and a structure of a circular cylindrical tank are studied for small motions. The liquid is assumed as a perfect fluid, the side wall of the tank is treated as an elastic circular cylindrical shell, and the tank bottom is assumed rigid. The method of separation of variables is used to obtain series from solutions for the axisymmetric case. Velocity potential is introduced to express liquid motions in series expansions of an orthogonal system. Frequency equations are obtained from a kinematical condition along the side wall and numerically solved to illustrate the effect of coupling, showing that bat lower eigenfrequencies the motions are mainly due to liquid surface sloshing, and that at higher eigenfrequencies emerge so-called bulging modes consisting mainly of sinusoidal motions of the side wall.
TL;DR: In this article, the torsional fatigue strength of several types of shrink fitted shaft couplings is estimated based on the results of stress analysis, in which the changes of frictional coefficient and contact pressure during cyclic loading are taken into account.
Abstract: Torsional fatigue strength of several types of shrink fitted shaft couplings is estimated based on the results of stress analysis, in which the changes of frictional coefficient and contact pressure during cyclic loading are taken into account. Then these estimated strengths are confirmed by torsional fatigue tests. The results are summarized as follows. The firictional coefficient in the slip region increases steadily with an increase of cycles and saturates for more than 104 cycles. The saturated value of it is about 0.7. Torsional fatigue strength reduction factor of shrink fitted shaft is found to be Kf=1.28, which is far smaller than the rotational bending fatigue strength reduction factor (Kf=2∼3). Anti-fretting measures such as groove, taper are found to be not so effective for torsionalfatigue as for rotational bending fatigue.
TL;DR: In this article, a steel rod is pressed in the radial direction on a rotating disk with periodic corrugation surface and various resonances are observed in the frictional noise and acceleration because of the nonlinearity such as loss of contact between the rod and the disk.
Abstract: Experimental and theoretical studies have been done on the frictional noise without lubrication when a steel rod is pressed in the radial direction on a rotating thick disk with periodic corrugation surface. When the surface roughness becomes larger, various resonances are observed in the frictional noise and acceleration because of the nonlinearity such as loss of contact between the rod and the disk. That is higher harmonic resonances, subharmonic resonances, higher-subharmonic resonances of the fundamental lateral natural frequency of the rod, the fundamental and higher harmonic resonances of the higher mode of the rod are observed. Moreover, the differential and additional harmonic resonances of the fundamental and 2nd lateral natural accelerations of the rod are also observed with a long rod. The calculated results by considering the corrugation surface roughness as the external force almost agree with the experimental results. However, subharmonic, higher-subharmonic and differential and additional harmonic resonances do not occur so remarkably as those in experimental results.
TL;DR: In this paper, a numerical method to analyze bolt-nut joints with many contact surfaces is developed, where the flank load ratio to axial tension can be analyzed if there are pitch and flank angle modifications.
Abstract: For the analysis of bolt-nut joints, the finite element method has been used by several investigators. However, they had difficulties in applying the finite element method to bolt-nut joints with fastened plate. Although the analysis of elastic bodies in contact is not so easy, it is important to solve such problem as bolt-nut joints. Conclusions derived from this study are as follows : A numerical method to analyse bolt-nut joints with many contact surfaces is developed here. The flank load ratio to axial tension can be analysed if there are pitch and flank angle modifications. Also this method makes it possible to analyse the elastic-plastic problems of bolt-nut joints.
TL;DR: In this article, a seismic response analysis method for a cylindrical liquid storage tank subjected to a horizontal earthquake is presented, where the kinetic and strain energies of an empty tank shell are estimated assuming it as an axisymmetric shell.
Abstract: A seismic response analysis method for a cylindrical liquid storage tank subjected to a horizontal earthquake is presented in this paper. The kinetic and strain energies of an empty tank shell are estimated assuming it as an axisymmetric shell. The virtual work of liquid pressure exerting on the tank wall is also estimated analytically by assuming that the behaviour of the liquid follows the velocity potential theory which includes the effect of sloshing. The Lagrangian formulation for the coupled vibration is then derived. Coupling this equation with the Bernoulli equation for the boundary condition of a liquid free surface, an eigenvalue analysis method for the coupled vibration can be obtained. And, a seismic response analysis method is also made using the exciting energy due to a seismic wave. As a result of numerical studies, this solution is proved to be an effective and reasonable method for the seismic response analysis of a cylindrical liquid storage tank.
TL;DR: In this paper, a high-tension steel HT55 was conducted in 1% NaCl, and the wedge effect by corrosion products and crack extension by corrosive dissolution have been estimated in terms of ΔKeff.
Abstract: Corrosion fatigue crack growth test of a high-tension steel HT55 was conducted in 1% NaCl, and the wedge effect by corrosion products and crack extension by corrosive dissolution have been estimated in terms of ΔKeff. da/dN against ΔK in 1% NaCl decreases in the order of 0.01 Hz, 0.1 Hz, in air (having no frequency effect) and 5 Hz under R=0.1. da/dN in NaCl at 5 Hz is smaller than that in air on account of the wedge effect by corrosion products. There is no wedge effect under R=0.5. When the wedge effect is eliminated by re-plotting the results in terms of ΔKeff, da/dN under R=0.1 decreases in the order of 0.01 Hz, 0.1 Hz, 5 Hz and in air as is under R=0.5. Supposing the linear summation hypothesis in terms of ΔKeff, the crack extension by corrosive dissolution (da/dt)D is reduced.
TL;DR: In this article, a spiral-grooved tube with small internal spiral grooves was used to increase the evaporation heat transfer coefficient in horizontal tubes about 4.75mm I.D. with R efrigerant R12.
Abstract: This paper presents some experimental data about evaporating heat transfer in horizontal tubes about 4.75mm I.D. with small internal spiral grooves using R efrigerant R12. The groove inclinations of the tested internal spiral-grooved tubes are 4, 7, 15 and 30 degrees. It is found that a spiral-grooved tube can increase the evaporating heat transfer coefficient in tubes from one and a half times to twice as much as that of a smooth tube for annular flow region, and about ten times due to capillary phenomenon in grooves for stratified flow region.
TL;DR: In this paper, the effect of a free-stream turbulence of high intensity on the flow past a rigid circular cylinder was experimentally studied in a Reynolds number range 7.9×103∼5.4×l04.
Abstract: The effect of a free-stream turbulence of high intensity on the flow past a rigid circular cylinder was experimentally studied in a Reynolds-number range 7.9×103∼5.4×l04. Square-meshed grids were used to produce homogeneous turbulent-flow fields. The intensity and scale of a turbulent flow in which the cylinder was immersed were varied by positioning the cylinder at various locations downstream of the grid. Measurements were made of the time-averaged drag coefficient, Strouhal number of the vortex shedding, spanwise correlation length and length of the vortex formation region in the wake of the cylinder. These properties of flow around the cylinder were found to be considerably different from those measured in a smooth flow.
TL;DR: In this paper, a linear stability theory is treated for an incompressible laminar boundary layer along a cone rotating about its axis of symmetry with a constant angular speed in an external forced flow field.
Abstract: A linear stability theory is treated for an incompressible laminar boundary layer along a cone rotating about its axis of symmetry with a constant angular speed in an external forced flow field. Small perturbations are assumed to be of spiral vortices. This leads to one set of perturbation equations including an order of magnitude (δ1/R0), where δ1 denotes a displacement thickness of the boundary layer, calculated from a velocity component in the meridional section, and R0 is a local radius of the cone at instability. A numerical procedure for solving the eigenvalue problem is shown. As an example, calculations are carried out for a cone having a total included angle of 30° at a rotating speed ratio 3, where the rotating speed ratio is defined as the ratio of the circumferential velocity at the cone surface to the external flow velocity at the outer edge of the boundary layer. From stability diagrams obtained herein, critical Reynolds number, spiral angle and the associated eigenvalues are determined. The critical Reynolds number is compared with an experiment.
TL;DR: In this article, the temperature at the cutting edge of a tool in machining glass-fiber-reinforced-plastics was measured by a special thermocouple method, in which two insulated wires were embedded in the workpiece, and the hot junction of the thermocycle was established when these wires were cut together with the work piece.
Abstract: The temperature at the cutting edge of a tool in machining glass-fiber-reinforced-plastics was measured by a special thermocouple method, in which two insulated wires were embedded in the workpiece, and the hot junction of the thermocouple was established when these wires were cut together with the workpiece. The temperature distribution along the cutting edge, and the relation between the physical property (thermal conductivity) of tool materials or cutting speed (spindle speed) and the temperature at the cutting edge were analyzed to estimate the relation between the cutting temperature and the flank wear of cutting tools.
TL;DR: In this article, the effect of material anisotropy on the cutting mechanism was studied using test pieces of aluninum single crystal of various orientations, and the results are as follows : i) There is good agreement between the angle of slip 1ines observed on the side surface of the machined test piece and the one theoretically calculated from the active slip system.
Abstract: In order to study the effect of material anisotropy on the cutting mechanism, orthogonal cutting test was carried out using test pieces of aluninum single crystal of various orientations. The results are as follows : i) There is good agreement between the angle of slip 1ines observed on the side surface of the machined test piece and the one theoretically calculated from the active slip system. ii) It i s made clear that the shear angle in cutting of single crystal can be estimated reasonably from the active slip system of crystal. iii) The expectation of shear angle in polycrystal which has a distinctive preferred orientation can be also theoretically calculated on the basis of that in single crystal. iv) Process of shearing deformation is examined in detai 1 by observing slip line in shear zone.
TL;DR: In this paper, a vibration system of two-degrees of freedom which represents the fundamental characteristics of bevel gears is constructed mathematically, and it is found from the analysis of the system that the fundamental properties of vibrations which distinguish bevel gear from spur and helical gears are caused by a change in the direction of the tooth normal in tooth-meshing.
Abstract: Equation of motion for free vibrations of a pair of gears is derived in a general form. A vibration system of two-degrees of freedom which represents the fundamental characteristics of bevel gears is constructed mathematically. It is found from the analysis of the system that the fundamental characteristics of vibrations which distinguish bevel gears from spur and helical gears are caused by a change in the direction of the tooth-normal in tooth-meshing. the influences of parameters such as the contact ratio, stiffness of gear-carrying shafts and damping ratios on the band width of unstable regions of the vibration are also shown.
TL;DR: In this article, the authors obtained more accurate solutions of the boundary layer momentum and energy equations for a wedge-type flow by the electronic computer using the Runge-Kutta method and deduced an approximate equation of the temperature gradient at the wall with a high accuracy.
Abstract: The authors obtained more accurate solutions of the boundary layer momentum and energy equations for a wedge-type flow by the electronic computer using the Runge-Kutta method and deduced an approximate equation of the temperature gradient at the wall with a high accuracy. When a two-dimensional water jet with finite nozzle width strikes normally on a flat surface, it forms a flow field which can be divided into two flow regions ; the first one is an impingement zone and the other is a uniform parallel flow zone. It is the purpose of this paper to estimate local heat transfer coefficients in such a flow field, where the velocity gradient just outside the boundary layer changes along a flat surface and to study theoretically the effect of the nozzle height above the flat plate on the local heat transfer coefficient Furthermore the calculated results were compared with experimental ones of local heat transfer coefficients along a flat surface with constant heat flux.
TL;DR: In this article, more general multiaxial distribution functions are formulated taking into consideration both the normal and shear stresses and assuming straight surface cracks and penny-shaped cracks. And the brittle fracture loci under bi-axial stress state are analyzed.
Abstract: Most of the previous theories about brittle fracture, based on the weakest link theory, ignore the effects of shear stresses. In this paper, on the contrary, more general multiaxial distribution functions are formulated taking into consideration both the normal and shear stresses and assuming straight surface cracks and penny-shaped cracks. Using new multiaxial distribution functions, the brittle fracture loci under bi-axial stress state are analysed.
TL;DR: In this paper, a free-piston type rapid compression machine has been developed to simulate combustion process occurring in a diesel engine A light piston is pneumatically shot and gets hammered in a stop ring at the compression end, permitting a nearconstant elevated pressure and temperature sufficient to explore ignition of a fuel spray and subsequent combustion.
Abstract: A free-piston type rapid compression machine has been developed to simulate combustion process occurring in a diesel engine A light piston is pneumatically shot and gets hammered in a stop ring at the compression end A satisfactory performance has been achieved by this device, permitting a near-constant elevated pressure and temperature sufficient to explore ignition of a fuel spray and the subsequent combustion From a series of tests carried out on this machine, it has been shown that the ignition lag exhibits little or small dependence on pressure and temperature at some elevated pressures and temperatures It has been also pointed out that in the so-called diffusive burning period, combustion proceeds with self-accelerating rate of heat release in the case when much fuel is allotted to this period, while the rate declines monotonically with time in the contrary case
TL;DR: In this paper, an experimental investigation was carried out to study acoustic interferences in vortex shedding from a circular cylinder in a crossflow subjected to the acoustical vibrations directed along the axis vortex shedding along the cylinder axis.
Abstract: An experimental investigation has been carried out to study acoustic interferences in vortex-shedding from a circular cylinder in a crossflow subjected to the acoustical vibrations directed along the axis vortex-shedding along the cylinder axis. The results indicate that the effects of the acoustical vibrations directed along the axis of the cylinder are similar to the effects of the cylinder on the vortex-shedding from the cylinder, and both vibrations increase the spanwise correlation of the cylinder wake. The acoustic frequencies which produce powerful effects on vortex-shedding correspond to the frequencies of laminar-turbulent transition wave in a separated shear layer, and there are critical sound pressure levels in these acoustical vibrations.
TL;DR: In this paper, the axisymmetric vibrations of a cylindrical shell of which the thickness varies in the axial direction were analyzed by using the thin and the improved thick CCS theory.
Abstract: In this paper, we analyze the axisymmetric vibrations of a cylindrical shell of which the thickness varies in the axial direction by using the thin cylindrical shell theory and an improved thick cylindrical shell theory. We solve the equations of vibration exactly by using a series solution. As numerical examples, we obtain the natural frequencies and the mode shapes of cylindrical shells with both ends clamped, simply supported and free and examine the variations of the natural frequencies and the mode shapes for the variations of the thickness. And also, we make clear the influences of the shear deformation and the rotatory inertia upon the natural frequencies and the mode shapes.
TL;DR: In this article, the authors introduced the concept of strain energy area density, which represents the state of the work absorbed (strain energy in case of the continuum) at crack tip per unit area of crack plane generally.
Abstract: Crack energy density concept is newly proposed as one of the most important parameters in fracture mechanics, and the role of it is discussed. This parameter represents the state of the work absorbed (strain energy in case of the continuum) at crack tip per unit area of crack plane generally, and it should be called, as it were, strain energy area density especially for the case of the continuum. The introduction of the concept enables us to make a unified smooth description of the fracture condition from completely elastic (brittle) fracture to ductile fracture with large scale yielding, and also to solve some ambiguous problems in fracture mechanics. For example, the physical meanings of G0(K0) criteria ; Jc criteria and COD criteria on fracture are explained clearly through the concept.
TL;DR: In this paper, the quenching distances of mixtures of methane and hydrogen with air are determined as a function of hydrogen percentage of the hydrogen-methane mixtures, excess air ratio and pressure of unburnt gas.
Abstract: The quenching distances of mixtures of methane and hydrogen with air are determined. The quenching distances are given as a function of hydrogen percentage of the hydrogen-methane mixtures, excess air ratio and pressure of unburnt gas. It is observed that the flame quenching phenomenon has probability nature at the region where the distance of the two discs approaches the quenching distance. Futhermore, the correlation of stretch factor and quenching distances is derived and the relation of hydrocarbon emission levels of piston engines and quenching distances is discussed.