The present paper summarizes various problems on non-Newtonian fluid mechanics. Due to complex rheological behaviors of non-Newtonian fluids, constitutive equations have highly nonlinear character. As two approaches to obtain constitutive equations, continuum mechanics and molecular theory are described, and then a number of models are presented. Various flow problems are discussed. With regard to measuring methods, the hole pressure error and the first normal stress difference of dilute polymer solutions are stated. Moreover, steady flow in straight pipes, entrance flow through abrupt contractions, flow instabilities, Toms effect, and numerical method are briefly described.
An inverse procedure has been developed to obtain an exact solution for the travel time of seismic rays transmitted through a nonhomogeneous medium in which the seismic velocity depends only on depth from the surface. If the nonhomogenity is in the form of distinct, horizontal layers (graded material), then the procedure of ensuring continuous displacement and stress across the interface between homogeneous layers is straight forward but involves a considerable amount of algebra. However, if the nonhomogeneous medium has a continuous variation of properties (gradient material), then the problems are reduced to Abel's integral equation.
This paper deals with elastic buckling and flexural vibration of annular plates whose thicknesses vary linearly in the radial direction. The annular plate is subjected to in-plane forces along its inner and outer edges, which vary in the circumferential direction. These problems are analyzed by the Galerkin method. Eigenfunctions of the natural vibration of a constant-thickness annular plate without in-plane forces are used as admissible functions. Two types of in-plane forces are adopted ; one a sinusoidally varying nonuniformity along the outer edge, and the other uniform along parts of the outer edge and zero on the remainder of the edge. The influences of the nonuniformity of the in-plane forces on the buckling load and natural frequencies are investigated. It is found that the increase of the nonuniformity decreases the buckling load and the fundamental natural frequency. This tendency becomes more evident when the thickness of the plate at the inner edge is thinner and the hole larger.
A Fatigue crack Propagation test was carried out on HT80 and mild steel, and crack through thickness behavior was examined in detail, both experimentally and analytically. The major results are as follows. 1) The fatigue crack shape before penetrating the whole thickness is almost semicircular, and the measured aspect ratio is larger than the value obtained by calculation using the K value proposed by Newman-Raju. 2) It is found that the crack growth behavior on the back surface, i.e., the growth behavior of cracks after they have run through the plate, is unique and can be divided into three stages, a, b and c. 3) The fatigue crack growth rate at the stage b is constant for a wide range and is in direct proportion to the n-th power of the range of stress, Δσ. 4) A new model has been proposed to evaluate the K value after cracking through the plate thickness. 5) The K value proposed by the authors makes it possible to explain quantitatively the particular behavior of cracks after they have run through the plate.
A study has been made of the influence of artificial semispherical surface flaws with diameters of 25 to 175 μm upon the fatigue limit of high-strength steel. This has been done to better understand the origin of the harmful effect of hard inclusions on the fatigue resistance of high-strength steel in which hard inclusions are poorly bonded to the matrix microstructure. An attempt has been made to estimate the true fatigue limit of the ideal inclusion-free microstructure of the steel, and the effect of inclusions on the fatigue strength of the steel has also been discussed quantitatively on the basis of the results of such an estimation of the true fatigue limit.
Three-point and four-point bending tests were carried out in water on the high strength Ni-Cr-Mo steel quenched and tempered at 653 K in order to investigate the effect of mixed-mode I-II loading on the crack propagation and crack branching in delayed failure. The crack propagation velocity before crack branching was almost constant and independent of the ratio of mode II to mode I stress intensity factors when it was within 0.3. Both the crack-branching angle and the angle between the direction of the main crack and the bisector of the crack-branching angle increased with increases in the ratio of mode II to mode I stress intensity factors. The above results were explained by a criterion which was introduced by combining the hydrostatic tensile stress and the hydrogen concentration at a crack tip.
The characteristics of the aerodynamic interblade interaction of the vibrating cascade in transonic flow are examined by a "one-blade oscillation method" and some aspects of aerodynamic interblade interaction which are hidden in case of the conventional "all-blades vibration method" are clarified. In the report, the effects of the compressibility of the flow on the aerodynamic interactions are clarified and the reasons why the characteristics of the aerodynamic damping of the uniform cascade are varied with the Mach number, reduced frequency and interblade phase angle are elucidated.
The drag coefficient of porous materials in slow flow is examined theoretically and experimentally. A theoretical solution for a three-dimensional Ossen's equation is obtained by using a variational consideration and the cell model. From this solution, the drag coefficient is determined as a function of the Reynolds number and the volume fraction. Theoretical results are compared with the experimental ones obtained by using spheres or a coil model as porous materials. It is found that theoretical analysis is available for Ossen's equation and that the upper limit of the effective range for the Reynolds number is about 30. The value of the drag coefficient for general porous materials seems to lie in the region between those obtained from two-and three-dimensional theory.
In this paper, weak natural convection effects in the transient hot wire method of liquid thermal conductivity measurement are analytically investigated. Precise numerical calculations are performed using the FDM, concerning the slow natural convection liquid flow around a single thin hot wire and the distribution of the modified temperature term due to the flow. Then, the time dependencies of the apparent thermal conductivity, including the natural convection effects, are shown for various measuring conditions. The error in measurement are also shown for the case where two hot wires, having different lengths, are set in the Wheatstone bridge circuit to decrease the edge effects. It is shown, as a result, that slight natural convection effects appear, even during short periods of measurement, where the effects on accuracy had been considered negligible.
The heat tranfer of two circular cylinders fixed on a plane wall has been investigated in a cross-flow of air. The turbulent boundary layer thickness along the wall with no cylinder present was about 21 mm. The test cylinder diameter (d) was 15-15.3 mm, and the pitch (p) between the two cylinders was 16.5-66 mm (p/d=1.1-4.4). The Reynolds number (Re) based on the undisturbed uniform flow velocity above the wall ranged from 9 000-40 000. In this paper, variations in the characteristic features of the local and mean Nusselt numbers are discussed in relation to the value p/d and Re, with the pressure distributions around each cylinder and the features of the flow field investigated.
The characteristics of the forced convective condesation of a binary mixture of vapors on a vertical tube were experimentally investigated using a R 113-R 114 mixture under the condition of 1 300<Re<9 300. One smooth tube and three kinds of finned tubes were used as test condenser tubes. The experimental results of the heat-transfer coefficient in the small temperature-difference region were compared with the theoretical results using an analogy between heat and mass transfer. In the small bulk-to-wall temperature-difference region, the heat-transfer coefficient, especially for a high-performance finned tube, was reduced markedly by the thermal resistance of the diffusion layer. The effect of the diffusion lsyer was significant in the low Re number region, but it decreased considerably in the high Re number region. On the other hand, in the large bulk-to-wall tempersture-difference region, the reduction of the heat-transfer coefficient decreased and was almost independent of the vapor flow velocity.
This report describes liquid-solid contact behavior in the subcooled pool transition-type boiling regime and the minute bubble emission boiling regime, detected by a void probe that uses a series-resonance circuit. This probe can approach the heated surface within two to three micrometers. The liquid-solid contact state discussed in this report means the nucleate boiling state caused by liquid invasion or Leidenfrost state caused by liquid rush onto the dry part on the heated surface. The dried area on the heated surface was estimated on the basis of the void signal, and the relation between the dried area on the heated surface and the measured heat flux was clarified by introducing a nucleate boiling model.
The heat flux was measured at the second burnout point of pool boiling over the range of high subcooling of 30 K to 88 K, under atmospheric pressure. The relation between the heat flux and subcooling was obtained by a mathematical model based on the mass-transfer mechanism of evaporation and condensation through a coalescent vapor bubble, and by a kinetic theory of molecules. The relationship equation gave fairly good agreement with the experimental results and showed that the second burnout heat flux did not increase unlimitedly with subcooling, but that it had a maximum value at a certain subcooling.
The vapor explosion produced by a single drop or plural drops of molten LiNO3 being dropped into tapped ethanol is studied by high-speed photography and pressure trace measurement. The temperature range of fragmentation to occur is firstly examined. The pressure trace with fragmentation is divided into two groups. Under the relatively large subcooling condition of a cold liquid, the typical vapor explosion whose pressure trace has at least three peaks and a period of reduced pressure occurs. The vapor bubble behavior is proved to be well-consistent with the pressure trace. The propagation phenomenon of vapor explosion is photographed under plural-drop experiments. The existence of a lengthy state of coherency is proved, and the pressure behavior is concluded as the control factor of the coherency. A qualitative and hypothetical modeling of the vapor explosion mechanism is made on the basis of the experimental results.
A numerical calculation method has been presented for predicting radiative heat transfer from three-dimensional isothermal black bodies of arbitrary configurations. We consider the body to be composed of numerous arbitrary polygons, which can be generated by computer graphics of CAD ; and the effective exchange area of the threedimensional body is introduced for the numerical analysis. The present numerical solutions for bodies of simple configurations show good accordance with the existing analytical solutions. Radiative exchange between two arbitrary bodies can be calculated by using the effective exchange areas. As a calculation example, the effective exchange area of an automobile crank shaft model composed of 181 polygons was demonstrated. The numerical solutions converge with a relatively small number of graphic elements.
By injecting fuel into the duct of a co-axial burner and imparting a strong swirl on the outer air, two modes of flame, turbulent flame and flat flame, appear on the burner under some conditions. The conditions under which a flat flame mode, which features a commpact and a high-density combustion, was formed were studied by measuring temperature, fuel mass concentration, and gas velocity at the burner exit. The flat flame mode was found to be formed when the centripetal force of the high-temperature combustion gases toward the burner rim exceeded that toward the burner axis.
In order to investigate the effect of swirl on combustion in a spark-ignition engine, a new experimental apparatus, namely, the single-event engine was prepared. The swirl flow in the cylinder was visualized by a smoke-wire method, and a laser Doppler anemometer and a hot-wire anemometer were adopted for the velocity measurement. The turbulence intensity was determined on the basis of the hot-wire data. A stoichiometric propane-air mixture was ignited at the center of the combustion chamber ; thus, the flame was propagated almost axisymmetrically in the flow field at various swirl intensities with no squish flow. The burning velocity, ST, and the thickness of burning zone, δT, were determined in the spark-ignition engine cylinder. The result show that ST and δT increase with increasing the turbulence intensity, and that δT is correlated linearly with ST except under the condition of weak turbulence.
This paper deals with a method of designing a dynamic damper with a preview action. It is the purpose of this investigation to achieve an optimal design of the dynamic damper with a preview action, which is applied to a vibratory system with damping. First, in order to attain a systematic design of the dynamic damper system, a modern control theory is used, and two kinds of design equations are derived; one for optimal design parameters and the other for optimal preview action. Then, from the viewpoint of nonlinear programming, these equations are solved, presenting design charts of the dynamic damper with a preview action. Furthermore, a dominant factor on the control effect is investigated. Finally, the design procedure proposed in the present paper is applied to the conventional dynamic damper, and the control effect for the suppression of the impact vibration is discussed.
A highly accurate mechanical control for the antenna reflector is necessary for the Multi-Beam Satellite Communication System (MBSCS). This paper describes the design, development and experimental performance of the antenna pointing mechanism (APM) for the MBSCS. The mechanical configuration and component performance of the mechanism is documented along with the launch and operational environments of the three-axis communications satellite. This model which is based on nonlubricated direct-drive actuators is particularly appropriate for the APM's requirements. These include compact size, low mass, high stiffness, low power consumption and high reliability.
Few investigations have been carried out on the characteristics of bolted joints subjected to external bending moments, or, more specifically, on axi-asymmetric loads such as the clamping force of bolts and the external bending moment. In this paper, the clamping effect and the force ratio in the case where clamped parts are pipe flanges subjected to external bending moments are analyzed as an axi-asymmetric problem using the three-dimensional theory of elasticity. For verification, experiments are carried out with respect to the distribution of contact stress and the force ratio for the external bending moment (relationship between an increment of bolt axial force and the external bending moment). Analytical results are in fairly good agreement with experimental ones.
This paper presents a new hydrodynamic seal, in which the pressure drops caused by the reverse steps reduce the hydrodynamic film force, while they scarcely affect the film stiffness if the step recesses are deep enough. Thus, the clearance is controlled at high-speed operation. The numerical analysis clarifies that the leakage flow rate of the seal is less than a critical value over the entire range of rotating velocities. The critical leakage flow rate which corresponds to a zero hydrodynamic film force condition is determined by the seal face design, and it is independent of the balance ratio. If the seal operates at a relatively low balance ratio, a hydrodynamic lubricating film is formed at a low velocity. In addition, leakage is limited at a high velocity. The experimental results confirm that a seal with reverse steps shows excellent performance over a wide range of rotating velocities.
Surface roughening of sheet metals with plastic strain is removed at a given strain during the forming process, and its effect on the improvement of the forming limit is investigated. As a preliminary examination to estimate how the onset of localized necking is delayed by the removal of surface roughness, a rigid-plastic FEM simulation is first made. Experiments for soft aluminium and copper sheets are also carried out, and the increase in forming limit strain is examined for a few strain paths. It is shown that the improvement of the forming limit is considerable in the stretch forming region where the major and minor strains in the plane of a sheet are positive. For balanced biaxial stretching, for example, the forming limit strain can be increased up to about 1.3 to 1.4 times as large as that for ordinary in-plane stretching.
A quantitative analyzing method for the synchrony between a speaker's voice and a listener's nodding in interpersonal communication is proposed. A parameter of nodding is defined as the total area of a subtracted image between successive binary images converted from video frames. A parameter of voice is defined as the difference between the maximum and the minimum amplitude of the voice signal in the interval corresponding to the frame image. The relation between these two parameters is evaluated by the cross-correlation function. By using this method, basic characteristics of this synchrony are discussed. In addition, a real-time analyzing system for this voice-movement synchrony is developed for the purpose of processing a large amount of data. This study is useful for many applications, especially to realize a man-machine interface with smooth information exchange.