Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 1982"
TL;DR: In this article, a hot wire anemometer over ranges of Reynolds numbers Re os = |μm, os, l| D/ν(|μm and os, L| is the cross-sectional mean velocity amplitude, D = 2R the pipe diameter, ν the kinematic viscosity) from 600 to 65000 and of dimensionless frequencies √(ω') = R√(ϵ/ν) (ω is the angular frequency) from 2.6 to 41.
Abstract: Experiments on transition to turbulence in an oscillating pipe flow were made by using a hot wire anemometer over ranges of Reynolds numbers Re os = |μm, os, l| D/ν(|μm, os, l|is the cross-sectional mean velocity amplitude, D = 2R the pipe diameter, ν the kinematic viscosity) from 600 to 65000 and of dimensionless frequencies √(ω') = R√(ω/ν) (ω is the angular frequency) from 2.6 to 41. Critical Reynolds numbers from laminar to transitional and from transitional to turbulent flows agreed well with published experimental results. In the turbulent regime turbulent bursts follow by relaminarization in the same cycle. It is observed that the instantaneous velocity profile in every phase when a turbulence with higher frequency appears is represented by the well-known Blasius 1/7 power law, but in the laminar-like phase it does not follow the laminar theoretical solutions for a steady oscillating pipe flow.
90 citations
70 citations
TL;DR: In this paper, the vibration and sound of a rolling bearing with one dent on the race surface of the inner or outer ring or on the ball surface were studied, and the fundamental characteristics of ball bearings having one defect were clarified, and a method by which to locate the defect and determine its size was established.
Abstract: An investigation was undertaken with a view to establishing a procedure for diagnosing rolling bearings for defects from their vibration and sound. In the present investigation the vibration and sound of a rolling bearing with one dent on the race surface of the inner or outer ring or on the ball surface were studied. When the inner ring was caused to rotate at a constant speed under a given thrust load applied to the outer ring, the outer ring radial vibration velocity was determined by a moving coil type converter. Using the data so obtained, vibration waveforms were observed, peak vibration pulses measured, and real time frequencies of the vibration analyzed by Fast Fourier Transform analyzer. As a result, the fundamental characteristics of ball bearings having one defect were clarified, and a method by which to locate the defect and determine its size was established.
68 citations
TL;DR: In this paper, an experimental study has been made to investigate heat transfer and flow around tubes of in-line tube banks and it is found that the mean heat transfer coefficient shows no essential variation with the cylinder spacing for the second and farther downstream cylinders.
Abstract: An experimental study has been made to investigate heat transfer and flow around tubes of in-line tube banks. Measurements were conducted for seven cylinder spacings in the Reynolds number range from 104 to 6x104. It is found that the mean heat transfer coefficient shows no essential variation with the cylinder spacing for the second and farther downstream cylinders. The flow through the tube bank deflects in the case of a very narrow cylinder spacing and the heat transfer behaviors under such situations are clarified.
59 citations
TL;DR: In this paper, the characteristics of a flow around two circular cylinders of different diameters with the ratio d2/d1 = 0.68 arranged in tandem were carried out.
Abstract: Experimental investigations on the characteristics of a flow around two circular cylinders of different diameters with the ratio d2/d1 = 0.68 arranged in tandem were carried out. Reynolds number defined by the diameter of the first cylinder was varied in the range of 1.3×104 ≤ Re ≤ 5.8×104, and the longitudinal spacing between the axes of the cylinders in the interval of 0.9 ≤ L/d1 ≤ 4.0. The reattachment of a separated shear layer from the first cylinder, the jump phenomenon and the bistable flow at the critical region were confirmed in the same manner as the case of two cylinders of equal diameters. The differences between the two cases were discussed. Flow patterns were divided according to the spacing and Reynolds number. Characteristics of those flow patterns and effects of the Reynolds number were clarified.
55 citations
TL;DR: In this paper, an experimental study was conducted to investigate the heat transfer and flow around tubes in staggered tube banks in a cross flow of air, and the cylinder spacings examined Cy/d x Cx/d are 1.6 x 1.2 where Cx and Cy denote the cylinder spacing along and normal to the upstream uniform flow direction, and d the cylinder diameter.
Abstract: An experimental study was conducted to investigate the heat transfer and flow around tubes in staggered tube banks in a cross flow of air. The cylinder spacings examined Cy/d x Cx/d are 1.6 x 1.6 and 1.2 x 1.2 where Cx and Cy denote the cylinder spacings along and normal to the upstream uniform flow direction, and d the cylinder diameter, respectively. Main results obtained are as follows. In case of 1.2 x 1.2, the mean Nusselt numbers for the second and subsequent cylinders are almost equal to each other and much higher than that for the first cylinder. In case of 1.6 x 1.6, the third cylinder exhibits the maximum heat transfer rate. This may be due to the high velocity of an oncoming flow to that along with its high turbulence intensity.
51 citations
50 citations
TL;DR: In this article, the performance of a supersonic air ejector was experimentally studied over a range of ejector-to-nozzle throat-area-ratios and primary nozzle Mach numbers Mlp.
Abstract: The performance of a supersonic air ejector was experimentally studied over a range of ejector-to-nozzle throat-area-ratios Ψ and primary nozzle Mach numbers Mlp. The investigations covered both straight-tube and second-throat ejector types. As the result, the effects of the ratio Ψ on the ejector performance were made clear. The performance curves were classified into five groups by the values of Ψ and a primary chamber-to-ambient pressure ratio pop/pa. For a fixed Ψ, an optimum pop/pa exists which realizes a maximum secondary flow rate and a minimum secondary chamber pressure. Also, for a fixed Mlp, the optimum pop/pa becomes minimum at a certain Ψ, which was defined as an optimum throat-area-ratio. The physical meanings of the optimum pressure ratio and the optimum throat-area-ratio were clarified using the results of pressure measurements and optical observations.
47 citations
TL;DR: In this article, the authors defined turbulent quasi-steady state as the state in which relationship between cross-sectional mean velocity and wall shear stress for steady turbulent pipe flow holds at any moment in a cycle.
Abstract: Velocity distribution and pressure gradient in an oscillating pipe flow are measured over wide ranges of Reynolds numbers and dimensionless frequencies. Wall shear stress is determined by substituting experimental values of cross-sectional mean velocity and pressure gradient into an unsteady momentum integral equation. From these experimental quantities frictional losses and four characteristic parameters describing the flow pattern are calculated. They are well represented by the known laminar theory in a laminar regime and by the turbulent quasi-steady relations in a turbulent regime. Here, turbulent quasi-steady state is defined as the state in which relationship between cross-sectional mean velocity and wall shear stress for steady turbulent pipe flow holds at any moment in a cycle.
46 citations
TL;DR: In this article, a theoretical analysis on the characteristics of the slipper bearing is made from the standpoint of fluid film lubrication, considering all the oil-film parameters, that is, tilting angle, maximum tilting angles azimuth and mean clearance.
Abstract: A slipper bearing is one of the factors which affect significantly the performance of swash plate type axial piston machines. In this paper, considering all the oil-film parameters, that is, tilting angle, maximum tilting angle azimuth and mean clearance, a theoretical analysis on the characteristics of the slipper bearing is made from the standpoint of fluid film lubrication. As numerical examples, changes in the oil-film parameters due to a rectangular change of a supply pressure are shown. And also, the limit of fluid film lubrication is given in relation to the supply pressure and the rotational speed.
42 citations
TL;DR: In this article, the gear noise and the dynamic load acting on the meshing teeth of the gears with profile modification and without profile modification were carried out using power-circulating gear test rigs until a surface failure caused by scoring was observed.
Abstract: Measurements of the gear noise and the dynamic load acting on the meshing teeth of the gears with profile modification and without profile modification which are shifted by different amounts of addendum modification were carried out using power-circulating gear test rigs until a surface failure caused by scoring was observed. According to the experimental results of the gear noise and the dynamic load it is clear that the dynamic load acting on the meshing teeth decreases due to profile modification and that the gear noise of the gears with profile modification is lower about 5 dB than that of the gears without tooth profile modification. Further, the sound pressure levels at all the pass frequencies, the mesh frequency and the 2nd harmonic of the mesh frequency of the gears decrease at the incipient stage of scoring.
TL;DR: In this paper, a series of impact tests for steel plates have been carried out, where cylindrical, semi-spherical and conical-nosed SUS304 stainless steel projectiles were impacted onto carbon steel target plates 7∼38 mm thick.
Abstract: In order to clarify the strength of structures which require leak tightness, when struck by projectiles, a series of impact tests for steel plates have been carried out. Cylindrical, semi-spherical and conical-nosed SUS304 stainless steel projectiles were impacted onto carbon steel target plates 7∼38 mm thick. Test results showed that critical fracture energies of target plate by cylindrical and semi-spherical -nosed projectiles mostly agree with the values predicted by empirical formulas generally used, however, the critical fracture energy of target plate by a conical-nosed projectile is fairly smaller than these values. An evaluation formula for the critical fracture energy of target plate, applicable to three kinds of nose shaped projectiles, has been derived from the test results.
TL;DR: In this paper, the properties of high damping alloys, such as Mn-Cu alloy and Fe-Cr-Al alloy, were studied with a view to assessing the damping characteristics.
Abstract: The viscoelastic behaviors of two kinds of high damping alloys, Mn-Cu alloy and Fe-Cr-Al alloy, are studied with a view to assessing the damping characteristics. Under the assumption that the material is a linear viscoelastic body, the complex compliance is obtained from the wave propagation data on a long rod analyzed with Fourier transform technique. Copper is also examined for comparison. Experimental results reveal the frequency and amplitude dependences of damping capacity in each material. It is also found that the 4-element model should be applied for both high damping alloys, and the Maxwell model for copper, respctively.
TL;DR: In this article, the instantaneous velocity distributions and pressure gradients in a reversing pulsatile flow and an oscillatory flow in which turbulent bursts follow by relaminarization in the same cycle are investigated.
Abstract: The instantaneous velocity distributions and pressure gradients in a reversing pulsatile flow and an oscillatory flow in which turbulent bursts follow by relaminarization in the same cycle are investigated. They are predicted with sufficient accuracy by the theory for a transient pulsatile laminar flow in the laminar phase. Meanwhile, in the phase where turbulence with higher frequency appears, they are well approximated by the well-known 1/7 power law and the turbulent quasi-steady friction law respectively.
TL;DR: In this article, the free vibration of a simply-supported rectangular plate having a straight notch simulating a through-crack in the plate is analyzed to obtain its eigenvalues and the dynamic stress concentration in the front of the notch.
Abstract: Free vibration of a simply-supported rectangular plate having a straight notch simulating a through-crack in the plate is analyzed to obtain its eigenvalues and the dynamic stress concentration in the front of the notch. That is, the plate is divided into two parts along the notch and then, Fredholm integral equations of the first kind are derived for the internal moment and shearing force, using Green functions satisfying the boundary conditions of each part and continuity conditions of deflection and deflection angle of the original plate. The integral equations are transformed into the algebraic equations by the numerical integration and subdomain method, to calculate the eigenvalues and the moment and shearing force distributions. They are numerically calculated with regard to the lower four modes and the effects of the aspect ratio of the plate and the length and location of the notch on them are discussed in detail.
TL;DR: In this article, the influence of fuel properties on combustion with various emulsified fuels in a direct injection diesel engine was investigated, and it was shown that water-to-C heavy oil emulsion reduces NOx, CO and smoke as water to gas oil and water to C heavy oil do.
Abstract: The authors investigated the influence of fuel properties on combustion with various emulsified fuels in a direct injection diesel engine. Results show that water-to-C heavy oil emulsion reduces NOx, CO and smoke as water-to-gas oil and water-to-C heavy oil emulsions do. The improvement of the specific fuel consumption, however, is less remarkable than expected. This is because the effect of water vapour explosion is smaller than in the other emulsified fuels.
TL;DR: In this paper, theoretical equations for the coefficients of restitution as a function of the impact velocity for the impact of spheres of equal diameter and equal material are presented under the assumption that the separation of the impacting spheres is determined at zero relative displacement.
Abstract: Although current equations for coefficient of restitution in the central impact of solid spheres were presented only empirically as a function of the impact velocity v., theoretical equations for the coefficients of restitution as a function of vi for the impact of spheres of equal diameter and equal material are presented in this study under the assumption that the separation of the impacting spheres is determined at the zero relative displacement. Through comparison of results measured here using two ball pendulums for spheres of brass, lead, glass, porcelain and agate, the viscous nature of the materials is estimated.
TL;DR: In this paper, a hot wire is sandwiched between a plate-type specimen and a reference material of the known thermal conductivity, and the error and the reproducibility of the experimental values by this method are within ±4 % and ±1.5 % of the thermal conductivities of standard materials respectively.
Abstract: As an application of the usual hot wire method, a method of determining the thermal conductivity of the specimen is discussed theoretically, in which the hot wire is sandwiched between a plate-type specimen and a reference material of the known thermal conductivity. It is found that when the thermal conductivity of the reference material is known the thermal conductivity of the specimen can be determined theoretically just as in the case of applying the usual hot wire method to a homogeneous material. The error and the reproducibility of the experimental values by this method are within ±4 % and ±1.5 % of the thermal conductivities of standard materials respectively and this method is found very good.
TL;DR: In this paper, a periodic multi-sampling measuring system was developed which consists of a slanted single hot wire probe connected to a pulse motor, a scanning pulse generator, an analogdigital converter and a micro computer.
Abstract: In order to measure a three dimensional flow field and turbulent characteristics behind an impeller, a periodic multi-sampling measuring system has been developed which consists of a slanted single hot wire probe connected to a pulse motor, a scanning pulse generator, an analogdigital converter and a micro computer. With this system, three components of the mean velocity and the six Reynolds stresses in a complicated turbulent flow can be determined more accurately than with the conventional methods. Typical experimental results are presented for a measurement of a flow field immediately behind an axial flow impeller to show the availability of this measuring system.
TL;DR: In this paper, an optical dispersion equation is applied to describe the spectral characteristics of interband transitions and conduction absorption of electrons of these three metals, and quantitative expressions for the parameters in the equation are obtained for temperatures up to 1700, 1400 and 1000 K for nickel, cobalt and chromium, respectively.
Abstract: Infrared reflectivities and emissivities of nickel, cobalt and chromium are measured at high temperatures. Cobalt is found to have a remarkable hysteresis of emissivity around the martensitic transformation temperature. An optical dispersion equation is applied to describe the spectral characteristics of interband transitions and conduction absorption of electrons of these three metals. Quantitative expressions for the parameters in the equation are obtained for temperatures up to 1700, 1400 and 1000 K for nickel, cobalt and chromium, respectively. Spectral and total emissivities are calculated as functions of temperature and crystal phase.
TL;DR: In this article, the surface-restriction compensated gas bearing with T-shaped grooves has the following advantages ; (1) good damping performance, and (2) manufacturing ease, because of a small number of grooves, compared with the I-shaped groove bearing, which is composed of many narrow linear grooves.
Abstract: The surface-restriction compensated gas bearing with T-shaped grooves has the following advantages ; (1) good damping performance, and (2) manufacturing ease, because of a small number of grooves, compared with the I-shaped groove bearing, which is composed of many narrow linear grooves. This paper reports on dynamic characteristics of T-shaped groove bearing analyzed by the small perturbation method and results of an investigation by modified finite difference method, which can rationally express any bearing surface division, including both groove and land parts, by only one grid. Based on these calculated results, design criteria are given for a high performance bearing with high stiffness and high damping values. Furthermore, stability thresholds are also calculated.
TL;DR: In this paper, the axisymmetric vibrations of a vessel with variable thickness composed of a cylindrical shell and two circular plates as its lids were investigated and the Lagrangian of the vessel expressed by quadratic forms of unknown boundary values and obtained the frequency equations from the minimum condition of the lagrangian.
Abstract: In this paper, the authors investigate the axisymmetric vibrations of a vessel with variable thickness composed of a cylindrical shell and two circular plates as its lids. They obtain the Lagrangian of the vessel expressed by quadratic forms of unknown boundary values and obtain the frequency equations from the minimum condition of the Lagrangian. Effects of the variations of thickness of circular plates and a cylindrical shell, of the length of a cylindrical shell etc.upon natural frequencies and mode shapes are clarified in discussions of numerical results.
TL;DR: In this paper, the flow behavior around two cylinders with the same diameters and the local mass transfer around the downstream one have been made clear experimentally in the range of Re=(1.5∼8)×10 and the clearance x*=(0∼5)d.
Abstract: Succeeding to the former, report on two circular cylinders with different diameters, the flow behavior around two cylinders with the same diameters and the local mass transfer around the downstream one have been made clear experimentally in the range of Re=(1.5∼8)×10 and the clearance x*=(0∼5)d. The main results are summerized as follows. (1) Flow in a closed vortex region formed between two cylinders can be classified. (2) The maximum Nu (Sh) up to the jump clearance closely depends on the velocity gradient at the reattachment point. (3) Overall Nusselt number is proportional to Re2/3 and shows an increase of 20-30% as compared with that of a single cylinder in spite of the change of the flow pattern due to the clearance.
TL;DR: In this paper, the in-plane vibrations of a curved bar of which the cross-section varies are analyzed by using the classical theory and the equations of vibration and the boundary conditions are determined from the stationary conditions of the Lagrangian of vibration in a period of the curved bar with varying cross-sections.
Abstract: In this paper, the in-plane vibrations of a curved bar of which the cross-section varies are analyzed by using the classical theory. The equations of vibration and the boundary conditions are determined from the stationary conditions of the Lagrangian of vibration in a period of the curved bar with varying cross-section. The equations of vibration are solved exactly by a series solution. As numerical examples, the natural frequencies and the mode shapes of symmetric elliptic arc bars with both clamped ends and with both simply supported ends are obtained. And the variations of the natural frequencies and the mode shapes for the variations of the cross-section are clarified.
TL;DR: In this article, the authors investigated the optimum conditions for squeeze casting applied to fabrication of SiC fiber reinforced aluminium and found that the selected conditions satisfy the requirements, i.e., soundness and high strength.
Abstract: Squeeze casting increases the productivity of the fabrication of composite materials, whereas the theoretically expected strength is not easily attainable by it due to many factors. The present investigation has been carried out systematically to find the optimum conditions for squeeze casting applied to fabrication of SiC fiber reinforced aluminium. From the experiment, it is found that the selected conditions satisfy the requirements, i.e., soundness and high strength. The results obtained are summarized as follows : l) Squeeze pressure must exceed 500 kg/cm2 to produce composites free from cavities. 2) Infiltration speed does not affect the microstructures and tensile strength. 3) There exists a suitable temperature range to fabricate reliably sound composite materials with a given volume fraction of fiber. The range can be presented by considering a parameter depending on both temperatures of fiber and molten aluminium immediately before infiltration.