bluuebunny/crossref_metadata_2025 huggingface dataset:
Paper 7. Unsteady Flow around a Slender Fish-Like Body
Authors: Wu Th. Y. , Newman J. N.
Published: February 2007

This paper attempts to extend some recent theoretical calculations on the unsteady flow generated by body movements of a slender ‘flat’ fish by further including the effect of finite body thickness in the consideration for various configurations of side and caudal fins as major appendages. Based on the slender-body approximation, the cross-flow is determined for different longitudinal body sections which are characterized by a variety of cross-sectional shapes and flow conditions (such as having smooth or fin-edged body contours, with or without vortex sheets alongside the body section). The effect of body thickness is found to arise primarily from its interaction with the vortex sheet already existing in the cross-flow. New results for the transverse hydro-dynamic force acting on the body are obtained, and their physical significances are discussed.
Paper 14. Ship Manoeuvring with Application to Shipborne Predictors and Real-Time Simulators
Authors: Norrbin N. H.
Published: February 2007

The main object of this paper is to define the role of shipbornc manoeuvring predictors and pre-launch simulators in ship operation and new design, as well as to discuss a few selected details of simulator models and man-machine interface. Evidence is given to show that the manually operated free-sailing scale model will fail as a steering simulator in important cases. Records of helm manoeuvres on board large tankers in harbour approaches reveal a need for predictor assistance. A schematic flow diagram (Fig. 14.2) indicates the way modern computer and control theory will make new use of inputs from ship-model testing and hydrodynamic theory. Quasi-steady computer models are reviewed with respect to size and usefulness, and it is shown that a correct linearization is not always achieved by dropping non-linear terms. The on-line system identification technique will make it possible to use formally simple models in a shipborne predictor. The shore-based simulator for research and development or training requires a more complex model to handle effects of waterway confinements and ambient disturbances.
Paper 21. Estimation of the Effectiveness of Lateral Thrust Units
Authors: Nikolaev E. P. , Pershits R. Y. , Russetzky A. A.
Published: February 2007

This paper suggests standard manoeuvres which can serve as the basis for evaluating ship controllability, in cases when no particular specification has been drawn up concerning the control of a ship equipped with a lateral thrust unit (LTU). Calculation procedures are given for prediction of LTU thrust necessary for a ship to perform the suggested manoeuvres while under the action of external forces due to wind of a given intensity. The paper also supplies data concerning ship speed influence on LTU thrust and moment, which may be used for calculation of the manoeuvring behaviour of a ship moving ahead or astern.
Paper 28. Yawing of a Ship Steered by an Automatic Pilot in Rough Seas
Authors: Afremoff A. Sh. , Nikolaev E. P.
Published: February 2007

This paper is concerned with the non-linear characteristics of an auto-pilot in improving the stability of ships in following seas. The theory is developed for optimizing the auto-pilot, accounting for the non-linearities introduced by limitations on rudder angle and rudder angular velocity. The yaw and rudder angles are assumed to be stationary random processes, and the Wiener–Hopf integral is used to obtain the transfer function relating them in a system of waves, hence yielding the optimum rudder behaviour. For given auto-pilot characteristics, it is shown how root-mean-square yaw angles may be estimated for a ship in a given course in a known sea state.
Orthotropic Characteristics of Glass-Fibre-Epoxy Laminates under Plane Stress
Authors: Ogorkiewicz R. M.
Published: February 2007

Deformational characteristics of laminates of unidirectionally arranged glass fibres and epoxy resin under plane stress are shown to correspond very closely under uniaxial tension and, to a lesser extent, under shear to the theroetical pattern of stiffness of an orthotropic material. The anisotropy in stiffness is also shown to be accompanied by an even greater degree of anisotropy in tensile strength.
Solids Conveying in a Single Screw Extruder; a Comparison of Theory and Experiment
Authors: Lovegrove J. G. A. , Williams J. G.
Published: February 2007

As a check on the usefulness of solids conveying theory, a series of experiments was carried out. These experiments are described and their results are compared with some obtained theoretically.
Vibration of Flexibly Mounted Gyroscopes
Authors: Maunder L.
Published: February 2007

Flexibility in the supporting structure of two-axis or single-axis gyroscopes is shown to have a radical effect on vibrational characteristics. The analysis determines the ensuing natural frequencies and critical speeds.
Oil-Film Temperature Distribution in an Infinitely wide Slider Bearing: An Application of the Finite-Element Method
Authors: Tieu A. K.
Published: February 2007

From the Glansdorff–Prigogine local potential in non-equilibrium thermodynamics (1)† (2), a variational principle for a thin film incompressible flow with viscous dissipation is formulated as the basis of a finite-element method, which is applied to solve the energy equation. Temperature distributions in tapered land and parallel oil films for infinitely wide bearings are obtained by digital computer. The application of the finite-element method in a three-dimensional oil film with side leakage is also discussed.
Lower Bound on the time to Initial Rupture of Creeping Structures
Authors: Ponter A. R. S. , Hayhurst D. R.
Published: February 2007

In a previous paper (I)‡ an upper bound on the deformation of a creeping structure subject to constant load was derived which remained valid until rupture occurred at the most highly strained point of the body. Here we show that this bound may be used to evaluate a lower bound to the time of initial rupture for a certain class of structures. The method suggests that for many structures simple design calculation of an approximate nature should be possible. Values of the rupture life, obtained using the prediction method, are shown to compare well with the results of experiments carried out on a number of structures.
A Class of Slipline Field Solutions for the Hot Rolling of Strip
Authors: Dewhurst P. , Collins I. F. , Johnson W.
Published: February 2007

This paper presents the results of computer calculations of a class of slipline field solutions for the hot rolling of strip. The solutions are valid for the geometries encountered in the first few stands of a typical rolling mill. Comparisons are made with force and torque values predicted from technological analyses.
Limit Analysis of Curved Tubes
Authors: Calladine C. R.
Published: February 2007

An existing elastic solution is used in a lower-bound limit analysis of pure bending of a thin curved tube.
The Effect of Centrifugal Stretching in High-Speed, Self-Acting Gas Bearings Operating under Steady-State Conditions
Authors: Sadek K. S. H. , Cole B. N. , Dowson D.
Published: February 2007

The study reported in this paper arose from an investigation of methods of achieving oil-free compression of refrigerant vapours. One part of the investigation included a feasibility study of a high-speed rotary machine running in self-acting gas bearings lubricated by the refrigerant.

In certain designs of very high-speed rotor-bearing arrangements, centrifugal or radial growth of the journal might disturb the shape and magnitude of the nominal clearance space and thus affect the performance characteristics of the bearing. The nature and magnitude of these changes in bearing performance for uniform and for two forms of non-uniform centrifugal growth have been examined theoretically. Typical gas-film pressure distributions are presented together with design charts showing how attitude angle and load carrying capacity vary with speed. Comparisons are made with the performance of bearings having the same eccentricity ratio on the mid-plane, and guidance is given on the calculation of uniform radial growth at high speeds.

It is concluded that changes in lubricating film geometry resulting from centrigual stretching might have a significant effect upon the performance of certain high-speed, self-acting gas-lubricated bearings.
A Critical Review of the Theorems of Thermodynamic Availability, with Concise Formulations
Authors: Haywood R. W.
Published: February 2007

In this review, which includes some new material, the terms ‘availability’ and ‘irreversibility’ are used to denote certain concepts, their alternative use to denote certain physical quantities being avoided. The review commences with careful definition of the physical quantities, concepts and terms involved in the study, before proceeding to the formulation and proof of seven Theorems, three of which are treated in Part 1. The remainder of this part of the paper is devoted to the detailed evaluation of reversible work quantities, dealing specifically with such terms as available energy, free energy, exergy, anergy and essergy.

Part 2 (which will appear in the next issue) will be concerned principally with the evaluation of lost work output (or extra work input) due to irreversibility, while a critical, historical review will be presented in an Appendix.
Analysis of Elastic Plastic Composite Rotors
Authors: Bratt J. F. , Vangen G.
Published: February 2007

Composite rotors with cylinders or rings having orthotopic properties are considered. Each ring is unidirectionally reinforced in the tangential direction, and the rings are bonded together to secure continuity of radial displacements. It is shown that by varying the stiffness coefficient in the tangential direction according to linear laws an improvement in the overall strength of rotors results.
Laminar Heat Transfer in Rotating Eccentric Annuli
Authors: Launder B. E. , Ying W. M.
Published: February 2007

The paper presents numerical solutions to the problem of laminar heat transfer in eccentric annuli with the inner cylinder rotating. The method of solution is based on the general finite-difference procedure for solving elliptic partial differential equations developed by Gosman et al.(1)‡.

The solutions show that, for an eccentricity of 0.5, even modest levels of swirl greatly reduce the large circumferential variation in Nusselt number that is present without swirl. Moreover rotation appears to offer a particularly effective way of increasing the level of heat transfer since, for a Prandtl number of 0.7, the Nusselt number is raised by twice as much as the friction factor.
Research Note: The Effect of Variation of Shear Stress Factor on Vibrating Beams
Authors: Ghosh N. G.
Published: February 2007

It is known that in the calculation of natural frequencies and modal shapes for a vibrating beam, a value for the shear stress factor K has to be used. What exact value should be used is not known. This note presents the results of an investigation into the effect of various values of K on the natural frequencies.
Research Note: Performance of an Externally Pressurized Gas Porous Thrust Bearing
Authors: Murti P. R. K.
Published: February 2007

A circular porous thrust pad, externally pressurized with a compressible lubricant and with predominantly axial flow in the bearing matrix, is analysed. Closed-form expressions are derived for pressure distribution, load capacity, mass flow rate and static stiffness of the bearing. It is concluded that optimum performance of the bearing is obtained when it operates close to the critical bearing number.
Theoretical Studies of Tip Clearance and Radial Variation of Blade Loading on the Operation of Ducted Fans and Propellers
Authors: Gibson I. S.
Published: February 2007

Actuator disc theory and surface singularity techniques are applied to the performance of ducted fans and propellers, with particular reference to the radial clearance between rotor tips and duct inner surface and the radial distribution of rotor-blade loading. Many accounts have been written on ducted propellers but none includes the effects of clearance in any other than an approximate manner, that is, one-dimensional theory. The few studies that have been made of the radial variation in blade loading have been inconclusive and vague, mainly because of the inadequate duct model employed.

Here an accurate nonlinear theory is used to represent the duct and centrebody which has already been used successfully in the prediction of ducted propeller performance. Actuator disc theory, which is particularly suitable for combination with blade-element theory, is used to represent the variable-load propeller. Computed performance characteristics compare favourably with experimental results and the present studies enable the designer to fix both tip clearance and radial load distribution to suit the particular application under consideration. The general conclusions confirm and reinforce the limited experimental results available.
A Surface Vorticity Analysis of Three-Dimensional Flow through Strongly Swept Turbine Cascades
Authors: Graham D. , Lewis R. I.
Published: February 2007

The two-dimensional surface vorticity theory of Martensen is extended to deal with the full three-dimensional flow through a swept turbine cascade, including end effects. Basic concepts of surface vorticity theories are dealt with initially, as also are three three-dimensional flow considerations for swept cascades. The paper goes on to develop two theoretical models for the representation of swept blade row flows. The first model assumes that the blade bound vorticity remains constant across the span of the blade. In the second model, this assumption is relaxed so that the blade bound vorticity is allowed to vary in the spanwise direction. In both cases the theories are applied to turbine nozzle cascades. Some of the solutions obtained are compared with experimental tests which were the subject of a previous paper.
Research Note: A Method of Optimizing Vane Angles inside a Duct for Most Uniform Gas-Flow Velocity Profile
Authors: Smith R. M. A.
Published: February 2007

An optimization technique is described as applied to vanes inside a duct carrying a gas flow. With only a minimum of experimental data, optimum vane incidence can be predicted so that the flattest possible velocity profile is produced downstream.
Ricochet of Spheres off Water
Authors: Johnson W. , Reid S. R.
Published: February 2007

The ricochet of spheres from a water surface is reviewed, starting with an account of the historical interest in the phenomenon. The theoretical aspects of the problem are considered and a simple theory due to Birkhoff et al. (1)‡ is used to provide data on sphere trajectories.
The Yield, Flow and Creep Behaviour of Annealed En24 Steel under Combined Stress
Authors: Shahabi S. N. , Shelton A.
Published: February 2007

Constant stress-ratio tests under combinations of tension, torsion and internal pressure have been performed on annealed En24 steel. The initial yield locus conformed to the Maxwell Mises criterion under tension-internal pressure but lay between the Maxwell-Mises and Tresca criteria under tension-torsion. This implies a small degree of initial anisotropy.

Post-yield behaviour showed the plastic strain and strain-rate vectors to be normal to the initial yield locus and to remain so with respect to both time and increasing stress. The work-hardening hypotheses of plasticity theory were unsatisfactory in correlating any of the combined-stress results but equivalence of the strains was established from a consideration of the strain components and the angle between the stress and plastic-strain vectors. This resulted in the graphs of equivalent stress versus equivalent plastic strain in different stress fields being superposable.

Room-temperature creep of the logarithmic form ε a In t + c was exhibited by all strain components and correlation of the creep coefficients was established by a method similar to that introduced for plastic strains. This finally led to a complete correlation of the stress-strain-time behaviour of this material under complex stress.
The Stability of a Damped Elastic System with a Follower Force
Authors: Saw S. S. , Wood W. G.
Published: February 2007

A theoretical and experimental analysis is made of the behaviour of a double pendulum with viscoelastic hinges subjected to a follower force. The effects of variations in the masses, stiffnesses, geometry and the internal and external velocity-dependent forces on the stability of the system are examined in detail. The picture that emerges shows all these factors to be important. In all cases, instability occurs in the first mode of flutter motion and the results accurately confirm theoretical predictions.
The Second Virial Coefficient of Ordinary Water Substance: A New Correlation
Authors: Le Fevre E. J. , Nightingale M. R. , Rose J. W.
Published: February 2007

It is shown that the specific second virial coefficient for ordinary water substance, expressed as a function of temperature, is correlated by

This correlation, motivated by recent observations from low-pressure steady-flow calorimetry from 20°C to 140°C, also covers older tabulated values of the second virial coefficient extending to 800°C. The Boyle temperature is found to be 1498 K.

B2 = a1 f1 + a2 f2 + a3 f3

where f1 = 1/(1 + T/α), f2 = (1 - e-β/ T)5/2( T/β)1/2eβ/ T, f3 = β/ T, α = 10000 K, β = 1500 K, a1 = 0.0015 m3/kg, a2 = −0.000942 m3/kg and a3 = −0.0004882 m3/kg.
A Comparison of Numerical Solutions of the Unsteady Flow Equations Applied to Reciprocating Compressor Systems
Authors: MacLaren J. F. T. , Tramschek A. B. , Sanjines A. , Pastrana O. F.
Published: February 2007

The paper reviews briefly a number of methods which are now available to facilitate solutions to the hyperbolic partial differential equations describing unsteady compressible fluid flow. Various schemes are considered and their merits and disadvantages discussed. Equations describing unsteady one-dimensional flow with heat transfer, area change and friction are presented in conservation-law, normal and characteristic forms. Pulsations in a compressor system are predicted using both the two-step Lax-Wendroff scheme and a scheme based on the characteristic form of the equations. The Lax-Wendroff scheme was simpler to apply, required less computer time, and gave better agreement with experimental results obtained from a single-stage reciprocating air-compressor system.
Generalized Reynolds Equation for Micropolar Lubricants and its Application to Optimum One-Dimensional Slider Bearings: Effects of Solid-Particle Additives in Solution
Authors: Shukla J. B. , Isa M.
Published: February 2007

The effects of solid-particle additives in the lubricant are considered by characterizing this suspension as a micropolar fluid. The generalized Reynolds equation for this case has been derived and the optimum one-dimensional slider bearing is studied by using the techniques of the calculus of variations.
Transverse Bending of Cross-Ply Laminated Circular Cylindrical Plates
Authors: Sinha P. K. , Rath A. K.
Published: February 2007

The paper deals with the transverse bending of simply supported, circular, cylindrical plates consisting of cross-ply laminates with arbitrary sequences of 0° and 90° plies. The analysis is carried out within the framework of laminated-plate theory and shallow-shell theory, where the effect of transverse shear deformation is considered. The non-dimensional deflection parameters are computed for panels consisting of antisymmetric graphite-epoxy plies. The influence of the coupling between bending and extension, the plate curvature and the aspect ratio are studied and discussed.
Prediction of the Wavelength of Interface Waves in Symmetric Explosive Welding
Authors: Reid S. R. , Sherif N. H. S.
Published: February 2007

A theory is developed for calculating the wavelength of the waves produced at the welded interface between two identical and explosively projected (flyer) plates using the so-called symmetric welding arrangement. The theory appeals to the analogy between interface wave formation and the formation of a vortex street behind an obstacle in a fluid stream which has been discussed elsewhere (1)‡. It is a notional theory in the sense that the results of an inviscid analysis of jet collision are combined with a semi-empirical vortex shedding theory. In spite of this, the authors believe that it provides a useful first approximation to a more rigorous analysis, and this belief is supported by the agreement found between the theory and certain experimental results obtained from the welding of steel flyer plates.
On the Dynamics of Compressor Surge
Authors: McQueen D. H.
Published: February 2007

The one-dimensional equations of surge in centrifugal compressors are solved graphically for the pressure head and mass flow rate as functions of time for a variety of situations, and the results are discussed in terms of the acoustical properties of the external piping. Two important parameters affecting the nature of the surge limit cycle are found to be simply related to the acoustic capacitance and acoustic inductance of the system.
The Dynamic Behaviour of Passively Compensated, Hydrostatic Journal Bearings with Various Numbers of Recesses
Authors: Davies P. B.
Published: February 2007

A previously established small-perturbation analysis is developed to express the unsteady-state continuity-of-flow equation for an isolated recess in a passively compensated, multirecess, hydrostatic journal bearing in terms of generalized co-ordinates. The concise form of this equation enables motion of the shaft about the concentric position to be described by equations which are derived in closed form for bearings with orifice, capillary or constant flow compensation and any number of recesses.

These equations of motion, and hence the expressions for the receptances which describe the response of a bearing to external excitation, are shown to be of exactly the same form for all bearings of the type considered. Furthermore, the damping ratio and natural frequency in any particular case are determined by a single dynamic constant which is shown to be equal to a linear combination of circular functions and a limited number of coefficients which may be found explicitly by routine use of signal flow graphs.

The results of the analysis, which is exact within the stated assumptions, are compared with those of other workers and the steady-state solution of the equations of motion is shown to give an expression for static stiffness which is useful for design purposes. Numerical values of the dynamic constant for bearings with between 3 and 20 recesses are given graphically.
The Nonlinear Behaviour of Thin, Orthotropic, Curved Panels under Lateral Loading
Authors: Marshall I. H. , Rhodes J. , Banks W. M.
Published: February 2007

A theoretical analysis is presented for the snap-buckling behaviour of thin, orthotropic, spherically curved panels subject to central point and uniform pressure loading on the convex face. Clamped and simply supported edges are considered. The results are presented graphically for a range of panel aspect ratios and comparison is made with experimental studies.
Research Note: Streamline Pattern in a Confined Vortex Flow
Authors: Kotas T. J.
Published: February 2007

Using some simple assumptions with regard to the boundary conditions and confining the considerations to flows with small Rossby numbers, a pattern of streamlines corresponding to an axial plane of an incompressible vortex flow in a cylindrical vortex chamber is computed. The pattern obtained agrees qualitatively, in the main regions, with velocity profile measurements and dye-injection flow visualization experiments.
Research Note: Hydrodynamic Basis of Wave-Energy Converters of Channel Form
Authors: French M. J.
Published: February 2007

A study is made of a train of ideal deep-sea waves, 2 b in width, entering a channel of the same width whose flexible walls move horizontally and normally to the wave direction in simple harmonic motion so as to extract energy from the waves.
The Effect of Reynolds Number and Turbulence Intensity on the Performance of a Compressor Cascade with Prescribed Velocity Distribution
Authors: Citavy J. , Norbury J. F.
Published: February 2007

Experimental results are presented on the effect of Reynolds number ( Re) and turbulence intensity ( Tu) on the aerodynamic performance of a PVD compressor cascade at design incidence. The pressure distribution, outlet flow angle and losses were measured within the ranges Re = 0.6 times 105 to 2 times 105 and Tu = 0.35 to 4.4 per cent. In some experiments, the effect of axial velocity ratio ( AVR) was investigated. A substantial effect of the Reynolds number and turbulence intensity on the growth and bursting of the separation bubble was observed, with consequent effects on the aerodynamic performance of the cascade. The bursting of the bubble also gave rise to a hysteresis effect with Reynolds number.
Calculation of the Blade-to-Blade Compressible Flow Field in Turbo Impellers Using the Finite-Element Method
Authors: Adler D. , Krimerman Y.
Published: February 2007

No variational principle can be found for Wu's blade-to-blade equation and therefore no appropriate variational functional associated with the problem can be derived. This difficulty is overcome by using a Poisson equation as the basis for an iterative procedure. Thus the method retains the advantage of the variational approach in which the coefficient matrix of the linear algebraic equations is always symmetric. The symmetry of the coefficient matrix allows reduction of computer storage.
Research Note: Temperature-Entropy Diagrams of the Immiscible Liquid Binary Cycle
Authors: Burnside B. M.
Published: February 2007

Some characteristics of the immiscible liquid binary cycle are illustrated on T-s diagrams. The effect on optimization of matching to waste-heat loads is explained.
The Action of Lubricants in Metal Cutting
Authors: Williams J. A.
Published: February 2007

One important way in which cutting lubricants operate is by reducing the degree of adhesion between the tool rake-face and the freshly formed chip surface. It is suggested that processes of molecular transport within a network of interfacial capillaries play a dominant role in controlling the effectiveness of cutting fluids, providing that they are capable of reaction with, or adsorption into, the metal surfaces.
Modelling of Air Movements in Rooms
Authors: Nevrala D. J. , Probert S. D.
Published: February 2007

Dimensionless parameters pertinent to air flows in rooms are examined. Consideration of the limitations of modelling techniques leads to suggestions as to how significant results for full-size systems can be obtained from models of less than one-tenth full scale.
Hydrodynamic Lubrication of Ball-Bearing Cage Pockets
Authors: Molina M. A. , Gohar R.
Published: February 2007

This paper reports a theoretical study of the hydrodynamic load capacity and friction between a ball-bearing ball element and its straight-sided annular pocket. Design curves are derived which enable forecasts of load capacity, stiffness, torque and power absorbed to be made. The theory is confirmed by appropriate experiments and is also compared with previously published results obtained elsewhere by indirect means.
The Dynamics of a Multigimbal Hooke's-Joint Gyroscope
Authors: Burdess J. S. , Fox C. H. J.
Published: February 2007

The paper considers the dynamics of a gyroscope where the gyro rotor is supported and driven through a gimbal suspension, which takes the form of a parallel assembly of universal couplings. The linearized equations of motion are derived and the free response, and the response to a constant applied rate of turn, are determined. It is shown that the form of each response is greatly influenced by the geometry, inertia and stiffness characteristics of the suspension and the rotor speed. Tuning conditions are identified and the performance of the gyroscope as either an angular rate or an angular displacement sensor is evaluated.
Frequency and Loss Factors of Sandwich Beams under Various Boundary Conditions
Authors: Rao D. K.
Published: February 2007

A complete set of equations of motion and boundary conditions governing the vibration of sandwich beams are derived by using the energy approach. They are solved exactly for important boundary conditions. The computational difficulties that were encountered in previous attempts at the exact solution of these equations have been overcome by careful programming. These exact results are presented in the form of design graphs and formulae, and their usage is illustrated by examples.
Flow through a Slightly Curved Flame Front
Authors: Horlock J. H.
Published: February 2007

The flow through a slightly curved flame front located in a channel is analysed using actuator-disc theory. It is supposed that small variations in the conditions far upstream are specified (velocity u1, density ρ1, and flame speed S1, all as distributions across the channel), together with the density ratio across the flame, Λ. The curvature of the flame is related to u1, ρ1, S1 and Λ.
Analysis of the Local Deformations in Machine Joints
Authors: Burdekin M. , Back N. , Cowley A.
Published: February 2007

This paper presents a general method for calculating the pressure distribution and the deformations in machine joints. This method assumes that the components of the joint are connected through finite elements which are defined as a function of the surface finish, material and pressure at the apparent area of contact. The system so established is solved in an iterative manner using the finite-element method, obtaining, as a final result, the pressure distribution at the contacting surfaces of the components and the deformations of the surrounding body. To prove the validity and precision of the theoretical formulation, several examples of joints are considered where the correlation between the calculated and measured deflections is shown to be good.
Evaluation of the Autocorrelation Functions Used When Investigating Surface Roughness
Authors: Loukjanov I. V.
Published: February 2007

The use of autocorrelation functions and correlation lengths in surface texture investigation is considered. Approximate methods for evaluating correlation functions using random-process analysis are considered. Experimental data are also given. In particular, some important properties of the surface texture parameters, Sm and S, used in the approximate evaluation of the autocorrelation function, are considered.
Research Note: The Effect of an Upstream Impeller on the Flow in a Convergent/Divergent Duct
Authors: Preston J. H. , Rossiter J.
Published: February 2007

This note reports two sets of experiments dealing with the interaction of fans and the flow in a convergent/divergent duct system. A critical ratio of the angular velocities of the fans determines the type of flow.
Thermal Resistance of Pressed Contacts between Steel Surfaces: Influence of Oxide Films
Authors: Mian M. N. , Al-Astrabadi F. R. , O'Callaghan P. W. , Probert S. D.
Published: February 2007

Flat, rough surfaces of steel specimens were oxidized and subsequently pressed into contact. From a statistical analysis of the experimental measurements for freshly-assembled contacts, an expression has been established relating the loading pressure, mean roughness of the two surfaces and oxide film thicknesses to the thermal resistance of the contacts in high vacua. The thermal contact resistance increased with (i) the film thickness and (ii) the ratio of the total film thickness to the mean surface roughness, and decreased with the loading pressure and the mean surface roughness. Increasing and decreasing the applied load revealed a slight hysteresis effect.
The Plastic Behaviour of Annealed OFHC Copper
Authors: Holloway G. , Shelton A.
Published: February 2007

The effect of progressive deformation in the plug-drawing process on the initial yield and subsequent plastic flow behaviour of oxygen-free high-conductivity (OFHC) copper has been investigated. This paper relates to the behaviour of the annealed material under combinations of tension, torsion and internal pressure, prior to cold-drawing.

All loads were applied under constant stress ratio, and the initial yield points were obtained by utilizing the backward extrapolation of curves of stress versus strain and creep coefficient versus stress. The Maxwell-Mises criterion described the experimental yield locus obtained under biaxial tension but not the two tension-torsion loci. The difference is attributed to a small initial anisotropy.

In post-yield behaviour, the plastic strain and strain-rate vectors were normal to the initial yield locus and remained so under increased loading. The work-hardening hypotheses of plasticity theory failed to correlate any of the combined-stress results but equivalence of the strains was established by a consideration of the coaxial stress-strain path. This method resulted in a complete correlation of the stress-strain relationship for all loading paths in all stress fields.

Primary creep of the logarithmic form ε=a In t + C was exhibited by all plastic strain components, and a correlation of the creep coefficients was established on the same basis as that used for plastic strains. Finally, a complete correlation of the stress-strain-time behaviour of this material at room temperature was established.
The Elastohydrodynamic Performance of Low-Friction, Zero-Leakage Metal Seals
Authors: Ruskell L. E. C.
Published: February 2007

Part 1 discusses the requirements for the satisfactory operation of a reciprocating metal rod seal for a hydraulic actuator. Elastohydrodynamic theory is used to predict seal performance, and results indicate that with a suitable geometry good lubrication is possible in both stroking directions of the jack rod, even when the fluid flow is against the sealed pressure.

In Part 2, an experimental study of the lubrication of these seals is described. They exhibited low friction and zero net leakage, and measurements of oil film shape are presented which illustrate why this is so.
Optimal Twisting of Blades in Axial Turbomachines
Authors: Lesokhin Y. A.
Published: February 2007

One possible way to improve the aerodynamic performance of turbomachines is to analyse and generalize existing results obtained from design and testing. These can be applied to develop a quantitative relationship between the geometry of various regions of the flow path and turbomachine performance. An optimal correlation between various geometric parameters can be established in this manner. By studying blade geometry of various kinds of axial turbomachine (compressors, gas turbines, hydraulic turbines and pumps), the author has found some regularities in their geometry which enabled the design of highly efficient blades. Regularities in the twisting of impeller blades of axial compressors working over a wide range of Mach numbers are represented in this work. Information is presented showing that analogous regularities exist also for axial hydraulic turbine and pump blades.
Electroforming and Mechanical Properties of Iron-Nickel Alloy Foil
Authors: Lai S. H. F. , McGeough J. A.
Published: February 2007

A method of electroforming smooth, bright, iron-nickel alloy foil, of thickness about 0.1 mm, is developed. The electrolyte, mainly a solution of ferrous chloride and nickel chloride, is operated at a temperature of 95 °C, and at current densities of between 5 and 20 A/dm2. Below that temperature, and at current densities greater than 20 A/dm2, the foil becomes cracked. The amount of nickel co-deposited in the alloy can be increased up to a limit of 6.24 per cent, by reducing the current density and/or increasing the concentration of nickel chloride in the electrolyte. As the nickel content of the foil rises, the material suffers increasingly from hydrogen embrittlement. The main mechanical properties of the alloy foil are more affected by hydrogen embrittlement, the amount of which is influenced by current density and the concentration of nickel chloride, than by changes in grain size. This behaviour is in contrast with that of electroformed iron foil, for which the mechanical properties are largely controlled by the influence of the current density and electrolyte temperature upon its grain size. However, when the other process conditions are held constant, the mechanical properties of the alloy foil behave like the iron foil in decreasing with increasing foil thickness, owing to increases in average grain size.
On the Effect of Bearing Clearances in the Dynamic Analysis of Planar Mechanisms
Authors: Bahgat B. M. , Osman M. O. M. , Sankar T. S.
Published: February 2007

A systematic procedure for the dynamic analysis of planar mechanisms with multiple clearances is presented. Each link of the mechanism is considered as a rigid member, and contact modes are detected by iteration according to the inequalities of input torque and pin forces. The method is useful for predicting the number and frequency of contacts and separations occurring in the mechanism-joints for one complete cycle of the input crank.

A four-bar mechanism is used to illustrate the procedure. Results show that there are significant changes in accelerations, torque and pin forces as compared with the case without clearances. Minimal changes have been detected in displacement and velocity relationships.

The model presented in the paper provides a design method for investigating torque requirements, pin forces and separation occurrences in high-speed machines with clearance.
The Characteristics of a Statically Loaded Journal Bearing with Superlaminar Flow
Authors: Hinton R. E. , Roberts J. B.
Published: February 2007

Experimental results are presented, relating to the friction factor, load capacity and attitude angle, for a plain, cylindrical journal bearing with a central, circumferential inlet groove. The length to diameter ratio of the journal bearing was 1/3 and the clearance ratio was 0.011. By the use of various lubricants, including water, Reynolds numbers ranging from 40 to 50 000 were attained. Comparisons with various theoretical predictions are given. It is shown that a simple, empirical theory, which incorporates measured friction factors, gives better agreement with the experimental load capacity results than previous theories.
Some Effects of Heat-Treatment upon the Mechanical Properties of Electroformed Iron-Nickel Alloy Foil
Authors: Lai S. H. F. , McGeough J. A.
Published: February 2007

Contributions intended for publication as Research Notes should preferably be limited in length to 1000 words and two illustrations, and should be addressed to the Manuscript Section, The Institution of Mechanical Engineers, I Birdcage Walk, Westminster, London SW1H 9JJ

The problem of hydrogen embrittlement, which adversely affects the quality and mechanical properties of electroformed iron-nickel alloy foil, is considered. Heat-treatment, such as annealing, can reduce these effects of hydrogen embrittlement. The electroformed metal can also be converted to alloy steel by carburizing; and by other heat-treatments, such as hardening and tempering, a range of mechanical properties for the foil can be achieved.
Measurement with Rotary Gratings
Authors: Daly K. J. , Smith J. D.
Published: February 2007

A gear drive transmission error measurement system has been developed using small rotary optical gratings. Results can be obtained over a wide range of operating conditions up to shaft speeds of 6000 revs/min. Error components at frequencies up to 600 Hz have been measured and up to l000 Hz is achievable
Gas Dynamics of the Temperature-Determined Stirling Cycle
Authors: Organ A. J.
Published: February 2007

The Stirling cycle machine is modelled as a number of sections of duct in series, some tapered, some parallel. The working fluid assumes the temperature of the adjacent metal wall. Flow is defined by two conservation equations (mass and momentum) and the equation of state, p = ρRT. Friction is taken into account by using the steady-state correlation between friction factor, local instantaneous Reynolds number, and local hydraulic radius. The formulation permits frictional drag and frictional reheating to interact more or less as they do during operation of a Stirling cycle machine at high rotational speeds.

The equations are converted to characteristic form and solved numerically with pressure, p, and velocity, u, as state variables rather than the more usual a (acoustic speed) and u. This formulation paves the way for a full characteristics solution incorporating the energy equation but avoiding the entropy gradient term ∂s/∂x which is inappropriate to conditions within the Stirling machine.

The paper includes a Mach-line net plotted by computer for the first revolutions of the crankshaft after start-up. Indicator diagrams are presented corresponding to different angular speeds. It is found that the indicator diagram for the compression space is not greatly affected by angular speed, while that for the expansion space changes from positive, via figure-of-eight to negative over a relatively narrow speed range. An attempt is made to explain this unexpected finding in terms of the momentum equation for constant area flow with a severe temperature gradient.

A comparison is included between the computed results and those predicted for the same operating conditions by the Schmidt isothermal analysis.
The Effect of Sliding on Rolling Contact Pitting
Authors: Dawson P. H.
Published: February 2007

Using a disc machine and conditions generally relevant to gearing the effect of sliding on the pitting of a relatively soft 0·3 per cent carbon steel has been investigated. It is concluded that the magnitude of sliding has little effect in the region where pitting normally occurs and that the reluctance to pit under positive sliding is due to failure of the oil pressure propagation mechanism. The very occasional appearance of a pit in the addendum of gears is examined.
Turbulence Generated Secondary Flows in Ducts of Non-Circular Cross-Section
Authors: Seale W. J.
Published: February 2007

The use of algebraic stress models in the prediction of secondary flows in straight ducts of non-circular cross-section is found to be unsatisfactory and to give inconsistent results in the sub-channels within a rod bundle. An algebraic expression is presented which allows the source of axial vorticity to be calculated directly and without iteration. The expression is shown to reproduce secondary velocities in square and triangular ducts, and in a duct consisting of two inter-connected subchannels.
On the Thermal and Hydrodynamic Stability of a Fluid in a Vertical Slot
Authors: Sorour M. M.
Published: February 2007

This investigation is devoted to studying the thermal and hydrodynamic stability of the conduction regime of natural convection of a fluid with a nonlinear density temperature relationship in a slender slot with different, but constant, temperature walls. Linear perturbation techniques are applied for the transverse two dimensional disturbances to derive a set of two coupled twelfth order partial differential equations; the Galerkin method was used to solve the eigenvalue problem. The results of this analysis indicate that this flow is much more susceptable to thermal stability than to hydrodynamic stability for Prandtl number, Pr > 3·2. On the other hand for Pr < 3·2 the reverse is true.

Furthermore, both shear and bouyant mode characteristics are determined for a wide range of Pr.
Extension of the Patir-Cheng Flow Simulation of a Rough Surface Bearing to a Compressible Lubricant
Authors: Majumdar B. C. , Hamrock B. J.
Published: February 2007

It is shown that the average Reynolds equation for rough surfaces using an incompressible lubricant derived by Patir and Cheng (1)§ can be used for a compressible lubricant if the surface structures of both surfaces are the same. The average Reynolds equation is applied to an infinitely long gas journal bearing to find the hydrodynamic load capacity. The effect of the roughness parameter and the surface pattern parameter on the hydrodynamic load is also investigated.
Resonant Intake and Variable Geometry Turbocharging Systems for a V8 Diesel Engine
Authors: Watson N
Published: February 2007

A mathematical model is used to analyse the performance of conventional and resonant (Cser type) intake systems on turbocharged six-cylinder and V8 engines. For the V8 the system is slightly less effective than for the six, but is more compact and easily installed within the V of the engine. An optimum system was designed and tested on a V8 engine, with maximum torque b.m.e.p. increasing from 12.0 bar at 1850 rev/min to 12.7 bar at a reduced speed of 1600 rev/min.

Engine performance with the resonant system is compared to that with a simple variable-geometry turbocharger turbine, having only one major moving part. A mass-flowrate turndown of 42 per cent was achieved, but with a loss of turbine efficiency largely due to the constraints of adapting an existing turbocharger design. However a flat boost pressure curve was achieved from 1800–2600 rev/min. Maximum torque b.m.e.p. (with conventional inlet manifold) increased to 14 bar at 1600 rev/min. Engine performance at maximum speed (2600 rev/min) was unaffected with either system.
Systematic Procedure for Selection of Heat Exchangers
Authors: Larowski A , Taylor M A
Published: February 2007

This paper is addressed to the engineer responsible for preparing the heat transfer equipment data sheet, on which will be specified all the parameters required by the vendor for tendering for the equipment. Initially, the engineer must decide the type of equipment best suited for his application; guidelines for this selection are given in Part A of this paper. Finally he must supply all the data required by the specialist for preparing his design. In the case of proprietary equipment, this data will be limited to process details. For more general equipment, especially shell and tube heat exchangers, he also needs to supply some equipment specifications. Part B of the paper gives guidelines for preparing shell and tube heat exchanger data sheets.
Engine Transmission Systems for the Heavy Goods Vehicle and the Passenger Carrying Bus
Authors: Wallace F J , Tarabad M
Published: February 2007

This paper examines five engine transmission systems for heavy vehicles, two with stepped and three with continuously variable transmissions. They are compared from the standpoint of torque/speed and efficiency characteristics. A strong case is made for systems with differentially driven compressors.
Development of a Large-Bored Stirling Engine in Japan
Authors: Fujita H , Kushiyama T , Iwabuchi M , Kanzaka M , Goto H , Okada M , Goto T
Published: February 2007

The object of this study was to clarify problems and to assess the feasibility of developing a marine Stirling engine in the near future. The paper reports results of field tests which have been carried out and describes the design and production of the heat exchanger, combustor and experimental engine. A 66 kW output was recorded with a mean working gas pressure of 10.8 MPa and a gas temperature of 700°C in a series of operating tests. The results of these studies and tests have convinced the establishment that the design method for the heat exchanger and the practical approach for the design of the sealing device provide the basis for an actual engine in the near future.