Uniform Cross-sectional Area Research Articles

Numerical Prediction of Laminar Flow and Heat Transfer in Wavy Channels of Uniform Cross-Sectional Area

Numerical Prediction of Laminar Flow and Heat Transfer in Wavy Channels of Uniform Cross-Sectional Area

Stresses and Strains of Radially Reinforced Hollow Cylinders

A radially reinforced hollow cylinder subjected to a combined action of axial pressure and radial pressures at both inside and outside radii is considered. These radial pressures are induced by hoop rebars. Due to uniform cross-sectional area of radial rebars, the reinforcement ratio is inversely propertional to the radius, and the cylinder is radially nonhomogeneous. Assuming the radial rebars to be perfectly bonded to the matrix, a closed-form solution for the problem is obtained. When radial pressures vanish, hoop stress distribution varies drastically from the inside to the outside radii and is much smaller than the radial stress. With the presence of hoop rebars, radial and hoop stresses become uniform across the thickness and are of the same order of magnitude. Therefore, the axial capacity of hollow cylinders can be effectively enhanced with proper arrangement of radial and hoop rebars when the confining effect of material, such as concrete is considered.

A Measuring Theory of Impact Force Acting on a Bar with Two Different Diameters

The true value of impact force, in high speed deformation test of metals, is commonly measured by the Hopkinson-bar method. But, a drawback to this method is the restriction of measurable time because of the length of the bar. One of the authors suggested construction a measuring theory for impact force acting on a bar with uniform cross sectional area, based on the theory of the propagation of longitudinal elastic stress waves. From the stresses detected at two points on the bar, two stress waves travelling in opposite directions along the bar axis are separated, and the impact force is estimated, without the restriction of the measuring time. This paper presents a new theory for measuring the impact force which acts on a bar having two different diameters. The results of the experiments clearly confirm the validity and usefulness of this theory.

A measuring theory of impact force acting on a bar with two different diameters.

The true value of impact force, in high speed deformation tests of metals, is commonly measured by the use of the Hopkinson-bar method. But, a defect of this method is the restriction of measurable time because of the length of the bar. One of the authors suggested constructing a measuring theory for impact force acting on a bar with uniform cross sectional area, based on the theory of the propagation of longitudinal elastic stress waves. From the stresses detected at two points on the bar, two stress waves travelling in opposite directions along the bar axis are separated, and the impact force is estimated, without the restriction of the measuring time. This paper presents a new theory for measuring the impact force which occurs on a bar having two different diameters. The results of the experiments clearly confirm the correctness and usefulness of this theory.

波浪中における漁具の運動-I

A series of experiments was performed to study the motion of freely floating bodies in still water, and apply the data acquired here to the study on the motion of fishing gear. The displacement from the equilibrium position with the lapse of time was recorded on a 35mm film with the aid of a stroboscope and was evaluated for the vertical oscillation. The configuration of the models used in the experiments were of three types; a circular cylinder, a circular cone and a sphere. The main problem was to describe the motion of a float with non-uniform cross section area. For the solution of this problem, an approximation was done by substituting the amount of change in sub-merged volume due to damped oscillation as a volume of a body with uniform cross section area. Accordingly, to use this approximation menthod, the constant coefficient in the equation of motion was calculated in every period, i. e. the equation was solved by means of the method of variable constant. The theoretical consideration was performed based on the experimental results of damped oscillation to examine the possibility of applying the theory for a circular cylinder to a circular cone and a sphere. Through the experimental results, it was ascertained that the theory for circular cylinder could be applied to a circular cone or a sphere for practical purposes.

THE SEWING NEEDLE TEMPERATURE AND ITS ANALYSIS

The sewing needle-temperature rises considerably in accordance with increase of machine velocity and the number of fabric layers. The temperature rises under constant number of fabric layers increases rapidly first and then slowly, and may level off at very high machine velocity. The dependence of the temperature rise under constant machine velocity on the number of fabric layers has also similar behaviors described above.The complex shape of the needle is simplified as a semi-infinite rod having a uniform cross-sectional area. Then, it was derived the reasonable formula of the needle-temperature rises as a function of machine velocity and the number of fabric layers during the sewing without thread. This formula explains the relationship between the heat generation for a needle to move in and out of fabrics and the heat dissipation from the needle surface. The dissipation involves both the heat transfer to air and the heat transmission to fabrics. The formula has well-agreed not only with the experimental results but also with those reported in the literature.

The kinetics of adsorption of organo-phosphorus vapors from air mixtures by activated carbons

The adsorption characteristics of activated carbons for the vapors of dimethyl methylphosphonate (DMMP) and of isopropyl methylphosphonofluoridate (IMPF) were studied under kinetic flow conditions. The carbon granules were packed to a reproducible bulk density in beds of uniform cross-sectional area and subjected to constant inlet vapor concentration, volume flow rate, and temperature but varying bed weights. The breakthrough time of the vapor through the bed, at an exit concentration equal to 1 per cent of the inlet concentration, was determined for each bed weight, and plotted as a straight line in accordance with the equation for adsorption kinetics. The kinetic saturation capacity of the carbon for each vapor was determined from the slope and the pseudo first order adsorption rate constant from the intercept. Kinetic equations were constructed for each vapor and, when solved simultaneously, showed that the breakthrough time for IMPF could be correlated with that of DMMP in accord with the equation t b (IMPF) = 0.911 t b (DMMP)−8.86 for activated carbon and t b (IMPF) = 1.084 t b (DMMP)−4.32 for the same carbon after impregnation with copper, silver, and chromium salts. The close agreement between the relationships of these organophosphorus vapors on the two carbons suggests that the prediction of adsorption of one vapor based upon prior characterization with a reference vapor, originally applicable only under equilibrium, can be extended for use under kinetic conditions. A method is presented for calculating the kinetic adsorption capacity of an activated carbon for IMPF from the experimental DMMP value using equilibrium relationships, and shown capable of predicting the capacity within 4.1 per cent.

The propagation of non-uniform slow shock waves

A linearized analysis, based on small entropy variations, is used to determine the perturbation generated when an initially uniform slow magneto-hydrodynamic shock wave of arbitrary strength, propagating along a tube of uniform cross-sectional area, encounters a section of non-uniform cross-sectional area. Although this problem was solved previously, an error in the numerical computations has recently been discovered. This note serves to correct the error.

Experimental Study of Forced Convective Heat Transfer in Annular Passage with Axially Varying Cross Sectional Area

An experimental investigation of forced convective heat transfer in a passage with variable cross sectional area in the axial direction is presented. Experiments were performed with air flowing acceleratedly in the annular space constructed with a uniformly heated core tube and an outer tube with variable inner diameter. The results show that acceleration parameter K becomes a controlling characteristic quantity of heat transfer in this case. For this parameter below about 2×10-6, the local Nusselt number varies proportionally to the 0.77 power of the local Reynolds number, that is the same trend as in the turbulent case of uniform cross sectional area. Depending on the temperature distributions of fluid at the inlet, the heat transfer coefficient decreases and then increases, or monotonously increases with axial distance. Local heat transfer coefficients with K≤2×10-6 and in the axial region, where they increase with axial distance, are smaller than the values predicted by substitution of the same local flow conditions and diameter ratio into the fully developed heat transfer correlation for uniform cross section. These experimental results are correlated in the empirical formula.

Thermal decomposition of thallous azide. Crystal size effects and topochemistry

The kinetics of decomposition of polycrystalline and single crystal TIN3 were studied using the pressure-time method. Several crystal sizes were employed and the extent of an initial decomposition reaction was roughly proportional to their specific surface areas. An induction period followed the initial reaction and its duration increased with increase in crystal size. Finally, a maximum, linear rate of decomposition developed which was proportional to specific surface area. Microscopy revealed that decomposition began at preferred faces and proceeded in preferred crystal directios. A tendency to bore holes of uniform depth and constant cross-sectional area accounted for the linear kinetics.

Current Limiting Fuse Arc-Voltage Characteristics

Fusible elements of a uniform cross-sectional area, such as wire, produce an arc voltage that is directly related to available fault current, but is not basically related to circuit voltage. Conversely, nonuniform area elements, such as perforated ribbon, generate maximum arc voltages independent of fault-current magnitude, but proportional to circuit voltage. The instant of fault-current initiation determines whether the fuse will encounter maximum let-through current, arc voltage, and arc energy.

Laminar Forced Convection of a Dissipative Fluid in a Channel

In the present study, the steady laminar forced convection problem of heat transfer in the fully developed constant property flow of liquids through a certain class of channels is analyzed by considering the contribution of heat due to viscosity. The effects of viscous dissipation on the heat transfer are emphasized. A class of sufficiently long straight channels with uniform cross-sectional area is chosen such that the solutions for velocity and temperature fields are deducible directly from the equations of the boundary curves. The wall temperature is allowed to vary linearly in the axial direction, and some heat-source distribution, other than that due to viscosity, is imagined to be present in the flow field. The general solution of the problem for the given class of channels is given directly by avoiding the details of the mathematical treatment of the governing equations. To illustrate the general mathematical derivations and to visualize the effects of viscous dissipation, some basic examples have been investigated and the graphical representation of several relevant results is given in a number of figures. In the last section of this study, various relevant results and figures have been discussed from the point of view of viscous dissipation phenomena.

Further considerations in the design of lateral thrust units1

The division of thrust in a lateral thrust unit between the rotor and the ships hull is considered and shown to be of the utmost importance in the design of a thrust unit. The importance of duct inlet roundings is discussed and efficient intake shapes are derived for a unit employing ducting of uni form cross-sectional area and hence having no flow contraction or diffusion. Suggestions based on practical considerations are made for modifying these shapes. These allow for added ship resistance due to the presence of the openings and the use of the unit for slow speed manoeuvring. The question of closing doors for the unit is also discussed and finally suggestions are made for testing full scale units in certain suitable cases.

The Propagation of a Nonuniform Magnetohydrodynamic Shock Wave Into a Moving Monatomic Fluid

Summary An initially uniform magnetohydrodynamic shock wave of arbitrary strength propagates through a channel which consists of two portions of which one has uniform cross-sectional area while the other is of varying cross-sectional area. It is assumed that the flow in the nonuniform section in front of the shock is initially a uniform state and no perturbations (due to the area variations) of this flow reach the shock until the area variation is encountered. When the shock enters the nonuniform section, it is perturbed, the shock strength altered and the subsequent flow is nonisentropic. In addition to the perturbation due to the effect of the area variations on the initially uniform upstream flow, there are two further contributions—viz., a permanent perturbation caused directly b}^ the area changes and a transient disturbance— which propagates with true sonic speed with respect to the flow behind the shock, due to reflections of the permanent perturba­ tion at the shock. Expressions for these various contributions are obtained. The results presented include as special cases propaga­ tion of a nonuniform conventional gas dynamic shock into a moving nonconducting fluid and propagation of a nonuniform hydromagnetic shock wave into a stationary fluid.

Prismatic fin with non-linear heat loss analysed by resistance network and iterative analogue computer

The paper analyses heat flow by natural convection from a fin of uniform conductivity and cross-sectional area, fixed at one end to a hot wall and immersed in a cooler fluid. A resistance network analogue is used in conjunction with a new type of iterative analogue computer to determine the temperature distributions and fin efficiencies for a variety of fin proportions, on the assumption that heat loss is proportional to the local temperature to the power 5/4. Results are compared with the case of linear heat loss.

Plasmacytoma of the mandible

Plasmacytoma of the mandible

Relaxation Methods Applied to Oil Field Research

Abstract A numerical method for solving partial differential equations in steadystate fluid flow is described. This method, known as the "relaxationmethod," has two advantages over analytical methods:practically anyproblem can be solved, anda solution can be obtained quickly. Adisadvantage is that the solution is not general. The method is applied to coreanalysis and relative permeability measurement to calculate constrictioneffects and to calculate the true pressure drop measured by a center tap in a Hassler type relative permeability apparatus. Further applications aresuggested. Introduction Many problems in fluid flow cannot be solved analytically because of thenature of the boundary conditions. For many problems, however, an exact answeris not necessary because boundary conditions are not exactly defined or theparameters describing the porous medium are not accurately known. Therelaxation method can be used to obtain an approximate answer easily andquickly for the flow of incompressible fluids in porous media. The method canalso be used for other types of problems, such as determining the stress in ashaft under load, or the temperature distribution during steady state heatflow. In this discussion only calculations concerned with the flow of fluids inporous media will be considered. The method was introduced by R. V. Southwellin 1935. Theory The treatment given here follows that given by Emmons. Consider a porousmedium to be replaced entirely by a net of tubes of equal length and uniformcross-sectional area as shown in part in Fig. 1. Assume that the net of tubesbehaves exactly like the porous medium which it replaces; that is, the net canbe made fine enough to reproduce exactly the porous medium. T.P. 3145

Structure of the Keratin Molecule

WHEN wool fibres of uniform cross-sectional area are stretched extremely slowly in saturated air at 18° C., they break at 70 per cent extension1. Confined in its early stages to the amorphous regions of the fibre, extension occurs by the transformation of the crystalline phase from the I±- to the I-configuration at extensions above about 25 per cent2. It has been found possible to disentangle these two processes, and obtain a closer insight into the I±-I-transformation process, by studying the extension of wool fibres under constant stress3 in saturated air at low temperatures. Under a stress of 6·89 × 105 gm./cm.2 at 21° C., for example, the immediate extension of the fibre (3 minutes after the application of stress) was 19·4 per cent, rising to 30·2 per cent after 300 minutes and 68·4 per cent after 18,682 minutes. As might be expected, there is an exponential approach to the limiting extension of 70 per cent, as shown in the accompanying figure, where log (70 âE) is plotted against time.

Friction Coefficients for the Compressible Flow of Steam

Abstract The effect of friction on the flow of compressible fluids in pipes of uniform cross-sectional area was investigated analytically by Grashof and Zeuner who arrived at a relationship between velocity and friction coefficient for ideal gases. Stodola showed that “the curves of Fanno permit a general graphical treatment for any law of friction.” Frössel presented the first extensive measurements of friction coefficients for air flow through a smooth tube with velocities above and below the velocity of sound. His measured coefficients for compressible flow were in excellent agreement at corresponding Reynolds’ numbers with coefficients measured for incompressible flow. Egli expressed in dimensionless form the equations for flow of an ideal gas through a channel, and used them to deduce friction coefficients from measurements of flow through channels varying in width from 0.0025 in. to 0.010 in. In this paper are presented some experiments by Lang on friction in a commercial 1-in. pipe for steam flow at velocities up to the velocity of sound, and some auxiliary experiments by Benson on a similar pipe with liquid water. In an Appendix the analysis of flow of a compressible fluid in a passage of uniform cross section is restated without introducing difficult concepts, such as “work of friction” or “heat of friction.” It is elaborated to include cases in which heat flow is appreciable.