bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure Pulsations in pipe Systems with Multiple Reciprocating air Compressors and Receivers
Authors: Benson R. S. , Uçer A. S.
Published: February 2007

A modified non-steady one-dimensional homentropic theory is used to predict the pressure pulsations in pipe systems with multiple reciprocating compressors and receivers. Allowance is made for heat losses in the pipes by correcting the pipe lengths. Receivers are simulated by neglecting the lengthwise wave action and using the generalized non-steady flow energy equation. An extensive test programme is described with one, two and three compressors in pipe systems with a single receiver. Different receiver sizes are used and tests are carried out with the compressors in phase and out of phase. The experiments show that the correction for heat losses may be obtained from a single test with a simple single pipe compressor system. This correction can be applied to all the subsequent complex systems. The experiments showed excellent agreement between the predicted and measured pressure wave amplitudes, frequency and phase relations but the mass flow predictions may be in error from 2 to 14 per cent high. The methods offer an accurate method of predicting pressure pulsations and valve movement in multicycle compressor pipe and receiver systems.
Comparison of Shear, Compressive and Tensile Characteristics of Cast Irons
Authors: Adams R. D. , Fox M. A. O.
Published: February 2007

Cast irons were produced with variations in the quantity and shape of the free graphite inclusions and in the matrix structure to investigate the relationship between the shear, compressive and tensile mechanical properties. Differences were observed which may have a significant effect on design criteria for cast irons. For example, the ratio of shear to tensile strengths decreased from about 1·25 to 0·577 and the ratio of 0·1 per cent proof stress in compression to that in tension decreased from approximately 2 to 11 as the tensile strength (and ductility) were increased.
Elastohydrodynamic Sliding Friction in a low Modulus Point Contact
Authors: Thorp N. , Gohar R.
Published: February 2007

The friction in a lubricated point contact between a driven tungsten carbide ball sliding against a flat perspex plate is studied. Loads and speeds are varied to cover a wide range of conditions. Predictions based on established properties of the oil and straightforward elastohydrodynamic theory are compared with experiments. The range of application of various theories is discussed.
Thermodynamic Properties of five Halogenated Hydrocarbon Vapour Power Cycle Working Fluids
Authors: Burnside B. M.
Published: February 2007

Thermodynamic properties of five halogenated hydrocarbons, of importance as working fluids for small vapour power units, have been studied. The compounds are monochlorobenzene, hexafluorobenzene, o-dichlorobenzene, perfluoro-2-butyltetrahydrofuran and perfluorodecalin. With the aid of the Martin-Hou equation of state the properties of each compound, including sonic velocities and specific heat ratios, have been correlated. By comparison with the well established data for steam the accuracy of the sonic velocity and specific heat ratio values has been indicated. The information is presented in a manner which facilitates either the production of saturation and superheat tables or diagrams, or direct inclusion of the data in computer design and simulation studies of Rankine plant.
Concept of Slip Factor in Axial Impellers
Authors: Soundranayagam S.
Published: February 2007

A slip factor is often used to predict performance of axial impellers when exit flow does not coincide with vane exit angle. Concept of constant slip factor has no foundation.
Reaction Parameters for Uniform Beams Subjected to Displacement Excitation
Authors: Mahalingam S. , Bishop R. E. D.
Published: February 2007

Previously published numerical data on the responses of uniform beams to force excitation may be adapted for use with displacement excitation. The necessary conversion factors are presented.
Modal Response to a Specified Transient Acceleration
Authors: Mahalingam S. , Bishop R. E. D.
Published: February 2007

A judicious choice of generalized co-ordinates is shown to simplify the equations governing transient motion of a system excited by a transient generalized acceleration (as in an earthquake).
Vibration Characteristics of Bladed Disc Assemblies
Authors: Ewins D. J.
Published: February 2007

A study is made to establish the basic vibration characteristics of bladed disc assemblies. An analysis is presented and used to predict the natural frequencies and mode shapes of uniform bladed discs. It is found that there are many more natural frequencies than those indicated by a study of the blade cantilever modes. The effects of blade detuning are studied and found to give rise to irregular and complex modes of vibration. Consideration of the vibration characteristics under typical operating excitation conditions shows that a detuned system is susceptible to many more resonances than is an equivalent tuned system.
Dynamics of the Oscillogyro
Authors: Ormandy D. , Maunder L.
Published: February 2007

A previous analysis of the dynamics of this novel form of gyroscopic instrument is extended to include its response to vibratory inputs. Experimental results are presented which confirm the theoretical predictions both for constant-rate inputs and for vibratory excitation. In particular, it is shown that the tuned oscillogyro, which is the usual operational form of the instrument, is sensitive to excitation at twice the tuning frequency.
Hydrodynamic Lubrication of a Porous Slider
Authors: Prakash J. , Vij S. K.
Published: February 2007

A plane porous slider bearing is analysed and closed form expressions for pressure, load, frictional drag, coefficient of friction and centre of pressure are obtained. The effect of porosity is to decrease the load capacity and friction. However, the coefficient of friction is increased.
Separation Cavitation; Solutions for the Infinite Width Cylinder-Plane and Journal-Bearing Configurations
Authors: Taylor C. M.
Published: February 2007

Theoretical analysis of the infinite width cylinder-plane and journal-bearing configurations is undertaken using the separation cavitation boundary condition. The results could form the basis of experimental work designed to check the appropriateness of the boundary condition for low-load situations.
Response of a Strand to Axial and Torsional Displacements
Authors: Machida S. , Durelli A. J.
Published: February 2007

Taking advantage of geometric considerations the authors give explicit expressions for the determination of axial force, bending and twisting moments in the helical wires, and for the axial force and twisting moment in the core of a 7-wire strand subjected to axial and torsional displacements. The equations given are linear, could be similarly developed for strands of any number of wires or for strands subjected to large displacements, and should be found practical by designers. Measurements on oversize epoxy models of the strand show good correlation with the theory and support the observation that axial load has no effect on the effective torsional rigidity of the strand. Results of experimental strain analyses on steel strands and on models of strands, as well as other theoretical studies on helices and strands, will be published in other papers.
Creep Analysis of Smooth Curved Pipes under in-plane Bending
Authors: Spence J.
Published: February 2007

Theoretical analyses are presented for the behaviour of a smooth circular cross-section thin-walled curved pipe of constant thickness when loaded by in-plane bending moments under isothermal creep conditions. Twin energy analyses, designated type 1 and type 2 respectively, are used in conjunction with an n-power stationary creep constitutive relationship. Approximate solutions are obtained by direct minimization techniques on a computer.

Deformation results and stress-concentration factors relevant to the stationary condition based on straight-pipe values are reported for all practical geometries of pipe bends. The influence of the results on design and matters of total deformation and stress redistribution are briefly mentioned.
System for Determining the Critical Range of Stress-Intensity Factor Necessary for Fatigue-Crack Propagation
Authors: Jerram K. , Priddle E. K.
Published: February 2007

A new technique is described for determining the critical stress intensity factor required for fatigue crack propagation to occur. It enables data to be obtained more rapidly and with fewer testpieces than existing techniques. Initial results obtained for En 3A mild steel are in excellent agreement with published data.
Some Results in the Erosion of Prestressed Materials due to Water-Jet Impact
Authors: Vickers G. W. , Johnson W.
Published: February 2007

Two methods are described of applying uniaxial and biaxial tensile and compressive stresses to specimens subject to the erosive action of repetitive water jets which have speeds in the range 30–220 m/s.

The influence which prestress has on erosion is examined in a ductile material, α-brass, and in a brittle material, Perspex. The behaviour of these materials contrasts sharply due to their different fracture modes. Also the values of prestress to impact stress ratio and the type of stress applied, are shown to have a bearing on results.
Torsional Stiffness of a Thin-Walled Beam Braced by Pinned or Rigidly Fixed Transverse Diaphragms
Authors: Harrison T. , Siddall J. M.
Published: February 2007

The torsional stiffness of a thin-walled beam of open cross-sectional profile braced by evenly spaced transverse diaphragms is studied. Diaphragms rigidly fixed or attached by frictionless pins are treated and it is seen that, in either case, the only effect is to modify the St Venant torsional constant for the thin-walled beam.

The theoretical work is supported by experimental evidence from two braced perspex channels which simulate the two assumed methods of attaching the diaphragms. Good agreement is demonstrated.
Cage Slip in Roller Bearings
Authors: O'Brien K. T. , Taylor C. M.
Published: February 2007

The occurrence of cage and roller slip in lubricated roller bearings has been observed under adverse conditions of high speed and low load. Whilst slip is not normally a problem in roller bearings, in certain applications, for example the bearings supporting gas-turbine shafts, it can pose difficult design problems. For such conditions, bearing distress may occur due to increased wear and heat generation. A reduction of slip may be effected by the use of out-of-round races causing a preloading of some of the rolling elements; this, however, entails a corresponding reduction in fatigue life.

Work described in this paper supplements the small amount of existing experimental evidence available concerning slip in rolling-element bearings. As well as a consideration of the effects of load and speed on slip, particular attention is paid to the quantity of lubricant supplied and the degree of misalignment present and the influence of these parameters on slip. Experimental results show a considerable divergence from previous results obtained using a similar bearing.
Theory of Castor Oscillations
Authors: Roe G. E.
Published: February 2007

The oscillation of castored wheels is familiar in many situations, e.g. the steered wheels of motor cars, motorcycles, aircraft landing gear, caravans and trailers. The subject is well documented, with explanations usually in terms of tyre behaviour, yet none of these theories can explain the oscillation of the simplest castor—that on a tea trolley, which has no tyre. Nor are these theories applicable to the case of motorcycle stability. It seems that tyre deformation is but one instance of a more general property causing instability, namely the ability of the contact patch to move laterally relative to the steering axis. A simple theory covering these cases is presented here, and an understanding of the mechanism is possible from an energy diagram.
Heat Transfer versus Pumping Power Performance for Cross-Inclined Tube Banks
Authors: Smith E. M.
Published: February 2007

Thermal performances of several cross-inclined in-line tube banks in crossflow are compared with parallel in-line and parallel staggered tube banks of similar geometry, and found to be superior at higher flow rates.
Deflection and Vibration Analysis of a Flexible Fan Blade
Authors: Dokainish M. A. , Gossain D. M.
Published: February 2007

Finite-element technique used to obtain deflected configuration, and natural frequencies and mode shapes of flex-fan blades, used in automobile cooling system, as function of speed of fan.
Minimization of Power Consumption in Fluidic flow Control Circuits
Authors: Tippetts J. R.
Published: February 2007

Three fluidic flow control circuits are analysed so that their controlling ability and power consumption can be determined. Under certain conditions the power consumption can be minimized by judicious circuit design and it is shown that optimization depends on certain well-defined non-dimensional performance characteristics of the fluidic devices. The circuits involve unvented vortex amplifiers and bistable wall-attachment amplifiers, which are considered to operate in a few simply defined flow states. The object of this paper is to show how such calculations can be made and to show quantitatively the potentialities and limitations of currently available devices.
Study of the Injection Upsetting of Metals
Authors: Parsons B. , Milner P. R. , Cole B. N.
Published: February 2007

The punch pressure required to injection upset a cylindrical billet of an isotropic, non-work-hardening, rigid–plastic material is derived using an upper bound (velocity field) technique and by a ‘slab’ stress analysis. A method for applying the theory to the injection upsetting of work-hardening materials is evolved and the validity of this application is demonstrated by the results of experiments using pure aluminium, an aluminium alloy and copper.
Design and Performance of a Variety of Injector Systems
Authors: Hoggarth M. L. , Jones D. A.
Published: February 2007

A study of the design of injectors or ejectors as used in the gas industry has led to the identification of three principal methods of entrainment of the induced gas by the driving gas. The performances of injectors using these methods have been compared both theoretically and experimentally using the criterion of pressure efficiency. From the results obtained it was found that in practice the highest pressure efficiencies were obtained by jet entrainment injectors. This method of injection was used in an examination of the consistency of the injection ratio over the operating range with respect to variations in gas supply, governor and downstream pressures and changes in specific gravity and discharge losses.
The Mechanism of Ventilation Inception on Surface Piercing Foils
Authors: Swales P. D. , Wright A. J. , McGregor R. C. , Rothblum R.
Published: February 2007

Either separation or cavitation is a necessary but not sufficient condition for ventilation inception, and the surface ‘seal’ must be ruptured in some way to admit air. Three modes of rupture have been observed; at the nose, at the trailing edge, and through the tip vortex. Nose ventilation is associated with the vortex in a separation bubble, and tail ventilation arises from the instability of surface perturbations and can be predicted empirically. Tip vortex ventilation is not likely on prototype craft. Waves increase the likelihood of ventilation and in open sea conditions a reduction of some 4° in inception angle is predicted. Conventional fences suppress nose ventilation only.
Experimental Investigations of Strongly Swept Turbine Cascades with low Speed Flow
Authors: Hill J. M. , Lewis R. I.
Published: February 2007

Results are presented from an investigation into the blade to blade and meridional flow perturbations arising in high deflection turbine cascades subjected to large sweep angles. Experimental work has confirmed previous analytical estimates of the effect of sweep and indicated that certain common design procedures for the calculation of blade to blade flows are seriously in error. The significance of the results with reference to practical design considerations is discussed.
The Theory of the Vortex Drop
Authors: Binnie A. M.
Published: February 2007

A compact method is described of calculating the relation between the head and the discharge of water down a vortex drop of specified dimensions.
The Plastic Buckling of Thin-Walled Tubes Subject to Magnetomotive Forces
Authors: Al-Hassani S. T. S.
Published: February 2007

Aluminium alloy tubes and rings can be reduced in diameter by means of external coils through which a large capacitor bank is discharged, due to the high radial transient magnetic pressure. Both the radial and perturbed motions are investigated theoretically and experimentally. Predictions of the current waveform, radial displacement and the number of wrinkles on the tube agree well with the experimental results. The number of wrinkles increases with tube length and diameter. However, geometrically similar tubes, when reduced to the same final hoop strain, have similar buckled shapes with the same number of wrinkles.
An Investigation of two Turbulent Flows over Smooth and Rough Surfaces
Authors: Allan W. K. , Sharma V.
Published: February 2007

Experimental data for two-dimensional, low-speed, turbulent boundary layer flow has been used to verify the description of mean-velocity distributions proposed by Allan and to re-evaluate the entrainment function. The independence of pressure gradient and surface roughness as regards their effects on velocity profiles has been demonstrated. Boundary layer predictions agree with experimental data for a smooth surface, but further investigation is required for flow over a rough surface.
The Application of a Finite Element Method to the Evaluation of oil Whirl Characteristics
Authors: Shelly P. , Ettles C.
Published: February 2007

A method using finite elements for the whirl analysis of plain bearings is outlined. The special properties of an exponentially shaped element are linked to a parabolic type of approximation for the axial pressure profile.

The method is developed and applied to the prediction of whirl paths of a heavy rotor operating both in the horizontal and vertical modes. Several locus paths are presented to show the separate and combined effects of rotor unbalance and unidirectional loading over a range of rotational speeds.
The Effectiveness of the Impact Damper with a Spring-Supported Auxiliary Mass
Authors: Thomas M. D. , Sadek M. M.
Published: February 2007

This paper examines the effect of a spring-supported impact mass on the performance of an impact damper. This technique was developed after it was found that gravity detracts from the performance of a normal impact damper. The springs are used to support the impact mass at the mid point of its stroke so that the effect of gravity is negated.

The analysis presented in this paper is based on the assumption that the motion of the impact mass is stable and that there are two impacts in each cycle. The assumption that the impacts are equi-spaced is not made, and it is shown that such behaviour occurs very rarely in the resonant region. Theoretical predictions are verified experimentally, and the analysis is then used to develop design charts for the impact damper at various damping ratios, mass ratios and gap ratios. It is shown that the spring is detrimental to the performance of the damper if gravity is not present, but that the performance under gravity is improved to that of the device without gravity. It is shown that very light supporting springs make the accuracy required in centring the impact mass too high, so that the performance in practice increases with spring stiffness. The performance of the device at natural frequency ratios greater than 0.5 is not studied.
Influence of Shape Defects and Surface Roughness on the Hydrodynamics of Lubricated Systems
Authors: Berthe D. , Fantino B. , Frêne J. , Godet M.
Published: February 2007

In lubricated contacts, precision of shape governs film formation, load-carrying capacity and reliability. A theoretical study of systems containing shape defects, led the authors to consider a more general law than the classical Reynolds equation, which can separately take into account the shape defects of each surface. An application of this equation shows that shape defects can introduce harmful vibrations in ball bearings.
A New Thermodynamic Diagram for Representing Steady One-Dimensional Compressible Fluid Flow
Authors: Calladine C. R.
Published: February 2007

A graph of specific volume versus velocity is useful for describing effects in steady, one-dimensional compressible fluid flow through a converging–diverging nozzle. From a thermodynamic point of view there is nothing new in the approach, but it may serve as a useful introduction to the characteristics of compressible flow – particularly the special conditions which prevail at the throat of a choked nozzle.
Hydrodynamic Friction in Elliptical and Circular Point Contacts
Authors: Thorp N. , Gohar R.
Published: February 2007

Hydrodynamic friction in undistorted, concentrated point contacts is studied. Experimental measurements are obtained using a ball-and-plate machine, the plate being either flat, or with a circular groove. In the latter case, the ball drive-shaft is angled to vary the asymmetry of the contact. Reasonable correlation with experiment is obtained using a hydrodynamic theory which embraces the rolling, sliding and cavitation components of the total friction.
The Effect of Silencers of the Helmholtz-Resonator Type on Pressure Waves of Finite Amplitude: Single Pressure Pulses
Authors: Trengrouse G. H.
Published: February 2007

The attenuation of large-amplitude waves effected by silencers of the so-called Helmholtz-resonator type is envisaged as being due to the finite efflux of gas through the holes of the silencer with resulting partial reflection, and hence reduced transmission, of the incident wave. Quasi-steady, one-dimensional flow arguments are used to predict the attenuation, the flow conditions being assumed reversible and adiabatic, that is, isentropic. This latter assumption is avoided in an alternative method by assuming a knowledge of the relationship between pipe Mach numbers and the pressure difference in the pipe across the holes.

Indicator diagrams resulting from single pulse experiments are, in general, in good agreement with those predicted.
An Examination of the Stresses in Solids Being Conveyed in a Single-Screw Extruder
Authors: Lovegrove J. G. A.
Published: February 2007

Instead of using the traditional approach of assuming that some type of pressure exists in the solid being conveyed, the work presented takes a more fundamental approach by considering the actual stresses in the material which are associated with the conveying action.
Reference Stress for Structures Obeying the Prandtl and Dorn Creep Laws
Authors: Johnsson A.
Published: February 2007

The extraction of a reference stress for a given structure from an arbitrary two-parameter creep law is demonstrated. The technique is applied to a two-bar structure and a beam section subjected to pure bending. The material is assumed to follow creep laws of the form and .

Resulting errors in deformation rate are compared for the different creep laws and with results obtained from a Norton law.
Transient Thermal Stresses in the Quarter-Plane and their Relation to the Thermal-Cracking of Cutting Tools
Authors: Thomason P. F.
Published: February 2007

The transient thermal stresses in an insulated quarter-plane, subject to an instantaneous heat source on a segment of the surface, are determined with the aid of the Green's function for a two-dimensional infinite space.

Numerical results for the transient thermal stresses at the surfaces of the quarter-plane are superimposed on previous isothermal results for cutting-load stresses in a π/2 wedge, to provide a model for a metal-cutting tool in the transient stages of a cutting process. The results are related to the problem of the thermal-cracking of cutting tools, and mechanisms of crack nucleation and propagation are proposed for both ceramic and cemented-carbide tools.
An Experimental Canned Pump for Compressed Water at Pressures up to 100 Megapascals
Authors: Leong K. S. , Wonham J. , Bruges E. A.
Published: February 2007

A closed-loop flow circuit, incorporating a canned pump, has been developed for calorimetric studies on compressed water at pressures up to 100 MPa (MN/m2). The pump, which has a peripheral impeller, develops a maximum differential pressure of over 0.30 MPa and produces mass flow rates of up to 0.25 kg/s. The pump and associated flow circuits exhibit especially good flow stability. A unique pressurizing system is employed to raise and adjust the pressure in the pump and circuit. The oil and water pressures are equalized in a vessel where the oil/water interface is monitored using a capacitance method. Pump characteristics and associated calibrations are reported.
Hydrodynamic Induced Vibrations in Accelerated Thrust Bearings
Authors: Kettleborough C. F.
Published: February 2007

The transient response of an infinitely-wide slider bearing subject to tangential acceleration of the thrust ring has been investigated numerically. The reduced Navier-Stokes equations and the continuity equation are solved for a fixed-shoe bearing to produce a time-dependent solution for the pressure distribution, film geometry and velocity distributions for different types of runner acceleration. For a gradual increase or decrease in acceleration the new supporting film is found to be fully developed in the course of a few seconds. When the acceleration or deceleration is very rapid, an oscillation of the runner in the axial direction takes place. In the cases reported, this oscillation is always damped. As the ‘jerk’ (rate of change of acceleration) increases, the vibration increases in frequency, it has a greater amplitude and takes longer to die out. In all cases the resulting runner oscillation takes place about the steady-state position compatible with the new runner velocity.
Stability of an Axial Flow Compressor with Steady Inlet Conditions
Authors: Corbett A. G. , Elder R. L.
Published: February 2007

A series of mathematical models of varying complexity which describe the dynamic behaviour of an axial flow compressor as a set of nonlinear differential equations are derived in a systematic way. These models are justified by comparing their stability with experimental surge data.
Oil Film Thickness in Lightly-Loaded Roller Bearings
Authors: Bahadoran H. , Gohar R.
Published: February 2007

The effects of speed, load and roller geometry on the oil film thickness and shape in a complete roller bearing are demonstrated experimentally by means of optical interferometry.

At quite moderate roller speeds, increase of film thickness becomes inhibited. This effect is attributed to a truncated inlet meniscus, a similar condition having been observed elsewhere with a ball-and-plate machine and with a model of a tapered-roller thrust bearing.
Secondary Flow in Cascades: Two Simple Derivations for the Components of Vorticity
Authors: Came P. M. , Marsh H.
Published: February 2007

By considering a many-bladed cascade, two simple theories are developed for secondary flow in cascades. Following the work of Hawthorne (1)†, three components of vorticity are identified at exit from the cascade. An expression is obtained for the difference in the time taken for fluid particles to travel over the two surfaces of the blade, and this is used to derive the governing equations for the distributed secondary, trailing filament and trailing shed vorticities. It is shown that, for a many-bladed cascade, the total secondary circulation in the downstream flow is zero. The calculation of secondary flow for a real cascade is discussed, and it is shown that earlier calculations of secondary flow at exit from cascades are consistent with this new approach.
Research Note: Beam Displacement Excitation from a Support
Authors: Greif R.
Published: February 2007

The response of a beam due to displacement excitation of a support is considered. The response is determined in terms of a simple Fourier expansion. End motion is incorporated via Stokes' transformation while intermediate constraints are satisfied with Lagrange multipliers.
Buckling under External Pressure of Cylinders with Toriconical or Pierced Torispherical Ends: A Comparison of Experiment with Theory
Authors: Aylward R. W. , Galletly G. D. , Moffat D. G.
Published: February 2007

Experimental buckling pressures are given for some thin cylindrical shells closed by two types of end closure. These were (a) unpierced toriconical shells and (b) torispherical shells penetrated by axisymmetric flush cylindrical nozzles. The loading investigated was uniform external pressure and all the shell combinations were machined and stress-relieved.

The theoretical elastic buckling pressures corresponding to the above models were calculated using a digital computer program known as BOSOR 3, which is based on the variational finite-difference technique. This program calculates, for perfect elastic segmented shells of revolution, the asymmetric (i.e. with circumferential waves) bifurcation buckling pressures and also the large-deflection axisymmetric collapse pressure. In the asymmetric elastic case, both linear and non-linear pre-buckling stress resultants may be utilized.

For the five cylinders with toriconical end closures, the buckling failures were always elastic and the agreement between theory and experiment was good. For the six cylinders with pierced torispherical ends, failure was by asymmetric buckling, in the n = 1 mode. For most of these cases there were significant discrepancies between the experimental results and the predictions of elastic buckling theory. However, better agreement between theory and experiment was obtained when a more recent version of the BOSOR program, which considers elastic/plastic effects, was utilized.

Two limited comparisons, which should be of interest to designers, are also given. One comparison deals with the buckling resistance of a cylinder with either a toriconical or a torispherical head; the other considers the effect on the experimental buckling pressure of a cylinder/torisphere combination of piercing the torispherical head.
Flutter of Conservative Systems of Pipes Conveying Incompressible Fluid
Authors: Paidoussis M. P.
Published: February 2007

An examination of the dynamics of beam-like motions of pipes conveying fluid, with both ends clamped, is presented by means of beam theory and, in the case of thin-walled pipes, by thin-shell theory. Both theories predict that the system loses stability by divergence at sufficiently high flow velocity, and that at higher flow velocity the system is subject to coupled-mode flutter; between the two instabilities there is sometimes a region where the system is completely stable. The critical flow velocities obtained by beam theory and by shell theory are compared, and it is shown that the former coverage towards the latter as the length of the pipe increases.

Finally, the existence of coupled-mode flutter in gyroscopic conservative systems, such as the one investigated here, is briefly discussed.
A General Programme for Producing Pressure-Enthalpy Diagrams
Authors: Richter H. R. D. , Burnside B. M.
Published: February 2007

A computer programme for plotting the p-h diagrams of pure fluids, based on the Martin-Hou equation, is described. Flow charts are presented and the subroutines are described. The programme is a general one and is based on knowledge of about 40 constants for each fluid. These constants are presented for five fluids, perfluoro- n-hexane, perfluoromethylcyclohexane, perfluoro-(1,3)-dimethylcyclohexane, perfluoromethyldecalin and dichlorofluoromethane, which are of interest in Rankine cycle work.
Research Note: A Simple Algorithm for a Multi-Pipe Junction in Non-Steady Homentropic Flow
Authors: Benson R. S.
Published: February 2007

A simple algorithm is developed for non-steady flow at a three-way pipe junction and generalized to an n-way junction.
The Influence of Velocity and Scale on Cavitation Inception where Wall-Generated Gas Bubbles are the Sole Source of Cavitation Nuclei
Authors: Baum M. R.
Published: February 2007

It is established, using recently derived expressions relating the flow system properties to the size at which a gas bubble grown at a boundary wall will become detached, that the commonly observed variation in cavitation inception pressure with velocity in a given system can be simply attributed to variations in the size of bubble detached. However, it is concluded, from a comparison of predicted and experimental variations of inception pressure with scale of the system, that when considering scale effects the pressure necessary to promote gas-bubble growth must also be taken into account.
A Theoretical Estimation of the Performance of Journal Bearings Operating in the Turbulent Lubrication Regime
Authors: King K. F. , Taylor C. M.
Published: February 2007

The use of process fluids of low kinematic viscosity as lubricants and the ever increasing surface speeds which are being encountered in fluid-film bearings have meant an increase in the number of bearings which operate in the turbulent regime. This paper describes a theoretical evaluation of the performance of 360-degree journal bearings operating turbulently, presents generalized data and discusses the results with comments upon the assumptions made and practical realities.
Simple Approximate Treatments of Certain Incompressible Duct Flow Problems Involving Separation
Authors: Matthew G. D.
Published: February 2007

Many examples of abrupt conduit change, for example, sudden or gradual contractions, mitre bends etc., have been treated by free-streamline, potential flow theory in conjunction with the classical Borda result for sudden expansion loss. These analyses have provided results which show moderate but rarely close agreement with experimental evidence.

Here a fresh and simpler look is taken at such problems, on the basis of radical simplifying assumptions about the flow geometry and pressure distribution. It is demonstrated that direct application of the linear momentum equation, in association, where appropriate, with the Bernoulli equation, can yield results for head loss and contraction coefficients which are in consistently good agreement with experimental data (especially as far as head loss is concerned). It is shown in passing that these simplified arguments can even be used to provide a satisfactory approximation to the profile of a contracting jet, suggesting wider applications of the method in more complex geometrical situations.

The analysis is advanced in a teaching context to illustrate the power of momentum and energy methods in providing immediately useful solutions to certain problems involving abrupt change.
A Simple Composite Construction for Cylindrical Shells Subjected to External Pressure
Authors: Montague P.
Published: February 2007

A composite form of wall construction for externally pressurized cylindrical vessels is described, analysed and illustrated by experimental testing. It consists of two, thin steel membranes with an intervening filler which continues to carry load after the membranes have yielded. The wall has a high bending stiffness, making it less sensitive to initial imperfections and less susceptible to unpredictable failure by instability than the conventional rib-stiffened shell. This composite form fails eventually by strength failure of the filler, which is highly predictable. Theoretical predictions of the elastic and elastic-plastic behaviour agree well with experimental results.
Research Note: Singular Perturbation Analysis of Linear Vibrating Systems
Authors: Porter B. , Hibbert J. H.
Published: February 2007

The singular perturbation analysis of linear lumped-parameter vibrating systems presented in this note greatly facilitates the approximate determination of the natural frequencies and mode-shape vectors of complex engineering systems incorporating sub-sets of ‘small’ inertial elements. In this way it is shown that it is possible to retain in the analysis of such systems ‘small’ inertial elements which are frequently neglected in order to make tractable the vibration analysis of such systems by conventional methods.
Nonlinear Analysis of Orthotropic Plates
Authors: Chia C. Y. , Prabhakara M. K.
Published: February 2007

The large deflection of a rectangular orthotropic plate subjected to the combined action of edge compression and transverse load is investigated on the basis of von Kármán-type large-deflection equations. The edges of the plate are assumed to be either all clamped or all simply supported. A solution is obtained in the form of double Fourier series consisting of beam eigenfunctions for both transverse deflection and force function. The postbuckling of the plate is treated as a special case. Taking the first nine terms in each truncated series, numerical results in load-deflection relations and bending moments are graphically presented for three types of fibre-reinforced composite plates with various aspect ratios. The three types of transverse load considered in the combined loading are central patch load, eccentric patch load and hydrostatic pressure. The present results for postbuckling and large deflection of isotropic and orthotropic plates are in good agreement with available data.
Velocity and Temperature Distributions for Cold Air Jets Issuing from Linear slot Vents into Relatively Warm Air
Authors: O'Callaghan P. W. , Probert S. D. , Newbert G. J.
Published: February 2007

Two-dimensional jets having various exit conditions were studied with a 15 cm field of view, laser-stimulated Mach Zehnder interferometer which provided isothermal contour maps, and with a pitot and thermoprobe traverse. At low discharge velocities (around 3 ms***), the onset of turbulence in the free air stream occurred further downstream of the nozzle than for higher efflux rates, and for vent widths of 2 mm and 4 mm the hypothetical source appeared downstream of the nozzle. However, at these low velocities, jet diffusion was more rapid after transition than for higher velocity cases. In general, the thermal boundary layer breadths were greater for narrower nozzle widths. To avoid excessive entrainment, the nozzle exit Reynolds number should exceed 1000.
Analysis of Noise Reduction Obtainable from the Redesign of a Mechanical Assembly
Authors: Satter M. A. , Ahmadi G.
Published: February 2007

A mechanical assembly which has been investigated experimentally for noise reduction (1)‡ is examined analytically. The assembly is reduced to a model of two unequal masses connected by a shaft. The redesigned version is the same except for the insertion of a rubber bush which isolates the larger mass, thereby reducing radiated noise. Only the longitudinal modes in which noise radiation was known to take place are considered for mathematical formulation. Vibrational amplitude spectra are derived for any point in the models. Amplitude spectra are substituted directly into the theory of sound radiation from a piston to calculate noise levels radiated by the larger mass. Experimental results are in good agreement with those obtained theoretically.
Exploratory Tests on the Effects of Random Loading and Corrosive Environment on the Fatigue Strength of Fillet-Welded Lap Joints
Authors: Marsh K. J. , Martin T. , McGregor J.
Published: February 2007

Fatigue tests on simple, fillet-welded, mild steel lap joints have been carried out to determine the effects of a corrosive environment and random loading. At normal testing frequencies, a brine-drip environment had no effect on the constant-amplitude fatigue strength at short endurances. At stresses less than the in-air fatigue limit, the corrosive environment was sufficient to allow crack growth at very low stress levels. In these corrosive environment tests, reducing the test frequency by a factor of 50 halved the life. The results of narrow-band random loading tests could be predicted reasonably accurately either by a fracture mechanics method or by Miner's rule.
An Analysis of a Self-Balancing System for Rigid Rotors
Authors: Sharp R. S.
Published: February 2007

A stability analysis of the balanced condition of a two-ball balancer for a plane rotor is presented, and the results of a parametric study of the system are included. Conclusions are drawn regarding the satisfactory operation of the balancer.
Cross-Flow-Induced Vibrations of Finite Tube Banks in In-Line Arrangements
Authors: Southworth P. J. , Zdravkovich M. M.
Published: February 2007

A systematic experimental investigation was carried out to classify the flow-induced vibrational responses of cantilever tubes in the streamwise and transverse directions within one-, two- and three-row in-line arrangements. Experiments were conducted with transverse pitch ratios of 1.33, 1.72 and 2.0 and longitudinal pitch ratios of 1.33, 1.67, 2.0, 2.67, 3.33 and 4.0 at various natural frequencies in the range 5.7 to 26 Hz. The rigid tubes were mounted on flexible cantilever rods and the monitored tube could be any one in any of the three rows. The velocity range started from very small amplitudes of vibration and proceeded up to maximum possible amplitudes, i.e. up to severe banging of the free ends of neighbouring tubes. The vibrational response was found to depend on the position of the monitored tube in the bank, velocity and tube arrangement. The vibration of a monitored tube in the single row tended to be in a streamwise direction. Maximum amplitudes always occurred in the second row of tubes, with oval vibration in the transverse direction. When the third row of tubes was added, the tube in it vibrated in a similar oval manner, but with smaller maximum amplitudes and in a more random fashion.
Influence of Mean Stress Intensity on Fatigue Crack Growth in an Aluminium Alloy
Authors: Branco C. M. , Radon J. C. , Culver L. E.
Published: February 2007

The effects of the mean stress-intensity factor, Km, and the range of the stress intensity, Δ K, on crack propagation phenomena in the Al-alloy RR 58 have been studied using contoured double-cantilever beam specimens providing a constant stress-intensity factor for all crack lengths.

Based on the experimental data available, a relationship of the following form, between the cyclic crack growth rate, d a/d N, and the tensile loading levels, has been proposed:

where Δ K = ( Kmax - Kmin); Kmax, Kmin and Km are the maximum, minimum and mean values of the stress-intensity factor; Δ Kth is the threshold value of Δ K for crack propagation; K1C is the critical fracture toughness in plane strain conditions; A and α arc constants. In tests at room temperature (21 °C) in laboratory air and at a loading frequency of 0.15 Hz, it was found that Δ Kth decreased with increasing values of K m, α was equal to 1.36 and A equalled 3.16 times 10-5(in/cycle).
Compressible Conical Diffuser Flow Using the Energy Deficit Boundary Layer Method
Authors: Livesey J. L. , Odukwe A. O. , Kamal W. A.
Published: February 2007

A performance prediction method for high inlet Mach number conical diffusers is developed, which uses the kinetic energy deficit equation in the calculation of the compressible turbulent boundary layer. A power law velocity profile is assumed together with Crocco's relation for the temperature distribution. Following Green, Morkovin's hypothesis is invoked to extend to the compressible flow the existing relations for the shear work integral originally developed for incompressible boundary layers. Comparison of the predicted results with available experimental results shows good agreement.
The Instability of a Cantilever on an Elastic Foundation under the Influence of a Follower Force
Authors: Wahed I. F. A.
Published: February 2007

The instability of a uniform cantilever compressed by a follower force at its free tip is investigated. The cantilever is supported on an elastic foundation and subjected to external viscous damping. The differential equation of lateral vibration of the cantilever is solved simply by Galerkin's method and the instability boundary is determined by applying Routh's criterion. It is found that the cantilever becomes unstable by flutter and that the critical force and the critical frequency depend on both damping coefficient and foundation modulus. Only with no damping is the critical force independent of foundation modulus, a phenomenon reported by other investigators.
Availability and Propulsion
Authors: Clarke J. M. , Horlock J. H.
Published: February 2007

The first and second laws applied to steady-flow systems are expressed in forms which emphasize the distinction between energy, which is conserved, and available energy, which is depleted in real processes. These forms are applied to propulsive systems using, as a velocity datum, the propulsion unit itself and, alternatively, the atmosphere at rest. The maximum thrust power obtainable from the combustion of the fuel is shown to be dependent on the composition, state and velocity of the fuel and also on the composition and state of the environment in which the unit works. An illustrative calculation of the losses in a turbojet engine in flight reveals that in this case 16.64 per cent of the fuel's available energy is obtained as thrust power, 54.25 per cent is rejected by the exhaust, 2.33 per cent is dissipated by aerodynamic losses and the remainder (26.78 per cent) is lost by combustion. Available-energy calculations are seen as providing a consistent framework within which losses can be compared within machines, between machines of different types for the same job and with perfection in the form of the completely reversible machine.
The Thermal Behaviour of Gauzes as Interfacial Inserts between Solids
Authors: O'Callaghan P. W. , Jones A. M. , Probert S. D.
Published: February 2007

The distribution of contact points formed between a flat solid surface and a metallic gauze has been examined, and the thermal resistances of contacts with gauze inserts have been measured. The resistance of a steel-to-steel contact in an ambient air environment was increased by the insertion at the interface of a gauze made from soft, high-conductivity metallic wires, but similar inserts led to a decrease of the overall resistance of the assembly in a high vacuum.
Generalized Reynolds Equation for Stochastic Lubrication and its Application
Authors: Christensen H. , Shukla J. B. , Kumar S.
Published: February 2007

By using the theory of a stochastic process, a generalized form of Reynolds equation applicable to rough bearings is derived by assuming the fluxes to be represented by power series of a stochastic film-thickness function.

In the case of a step slider bearing, it is shown that load capacity and friction force increase but that coefficient of friction decreases as roughness parameter increases. Similar results are true in the case of a hydrostatic bearing. Further, in this case, good agreement between this theory and the sinusoidal approach is illustrated by suitably choosing the roughness parameter.
A Pseudo Three-Dimensional Analysis of Flows in Vaneless Diffusers for Mixed-Flow Compressors
Authors: Wallace F. J. , Atkey R. , Whitfield A.
Published: February 2007

A solution is given of the equations of motion for inviscid flow with axial symmetry in mixed-flow diffusers of any given geometry. The associated computer programmes have been applied, together with similar programmes for the impeller based on streamline-normal solutions, to predict streamline, velocity and pressure distributions in a variety of vaneless diffusers as follows: (i) radial-flow impeller with radial diffuser; (ii) mixed-flow impeller with pure conical diffuser and (iii) mixed-flow impeller with curved diffusers.

The first of these is shown to give essentially stable flow, the second extremely unstable flow and the third conditionally stable flow provided that a suitable combination of initial contraction and hub/shroud profile is adopted.