bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrodynamic Impact Analysis of a Cylinder
Authors: Cointe R. , Armand J.-L.
Published: November 2009

The problem of the vertical entry of a rigid horizontal cylinder into an incompressible inviscid fluid initially at rest is addressed. The contributions of previous researchers are presented and discussed in the light of various assumptions introduced and the validity of the results obtained. Based on this review, realistic simplifying assumptions are introduced and the problem formulated. The method of matched asymptotic expansions is used to solve the resulting boundary-value problem. A new formula for the impact force is obtained, which differs from the classical von Ka´rma´n’s formula by a corrective term. The results obtained are compared with those of experimental observations and numerical calculations. The method may be extended to different geometries and nonvertical velocities to provide an estimate of the impact forces on the partially emerged pontoons of damaged semi-submersibles.
Dynamics of Flexible Hose Riser Systems
Authors: Vogel H. , Natvig B. J.
Published: November 2009

The paper describes a highly effective method for computing the dynamics of the catenary-shaped suspension of flexible hose systems. The method accounts for a number of nonlinearities, it is 3-dimensional and it is performed in the time domain. The paper addresses the analysis method and demonstrates its effectiveness on a sample flexible riser analysis.
Indentation and Penetration of Edge-Loaded Freshwater Ice Sheets in the Brittle Range
Authors: Timco G. W.
Published: November 2009

A series of indentation and penetration tests have been performed by edge loading of a vertical indentor into a floating sheet of columnar S2 freshwater ice. The load on the indentor was measured as a function of interaction speed (v = 0.1 – 60 cm-s−1), indentor width (D = 2.54 – 12.7 cm), ice thickness (h = 0.6 – 3.3 cm), strain rate (ε˙ = v/2D = 10−2 – 101 s−1) and aspect ratio (D/h = 0.5 − 22). In total, 66 tests were performed. In this paper, a description of the test procedures is given along with the full results in both graphical and tabular form. Five different ice fracture modes are identified and described. From the test results, an ice-failure mode map is derived which indicates the conditions in which each ice fracture mode predominates.
Wave Force Analysis by the Finite Element Method
Authors: Imai K. , Riho Y. , Matsumoto T. , Takahashi T. , Bando K.
Published: November 2009

The finite element method is applied to determine the wave forces and wave fields for various coastal and ocean structures. Wave diffraction and radiation problems are solved by the method. A special infinite element is implemented in a computer program to model an outer infinite sea area. The employed numerical examples are for a vertical breakwater, a gravity-type ocean platform and a floating rectangular caisson. All computed results are compared with ones from experiments and other numerical methods. As a result, it is concluded that the finite element method using infinite elements can give sufficient accuracy to be applicable to most practical structures in the ocean.
Wave Drift Enhancement Effects for Semisubmersible and TLP Systems
Authors: Eatock Taylor R. , Hung S. M.
Published: November 2009

Hydrodynamic interactions between the component bodies of a multi-body offshore system can cause substantial enhancement of certain load effects, such as mean horizontal drift forces and radiation damping. It is found, for example, that for a group of N similar members these forces can be of the order of N2 times the force on one member in isolation, over a range of low frequencies; and at higher frequencies interaction effects continue to have important consequences on design parameters. This paper discusses some theoretical background which sheds light on this phenomenon, and presents numerical results for semisubmersible, TLP and other configurations which provide further insight. The numerical evaluation of wave flow past these complex multibody systems is performed using a coupled finite element/boundary element model, together with the near field (direct integration) calculation of drift forces. Results are compared with an existing approximate method, and with idealizations based on the columns alone, with a view to the development of simple procedures for hydrodynamic synthesis.
Henderson Hoops: A New System for Marine Growth Inhibition on Offshore Tubulars
Authors: Stansby P. K. , Henderson T.
Published: November 2009

Polypropylene hoops encircling the tubulars of offshore structures are used to inhibit marine growth through their rotation which is induced by the action of current on flaps with a hinged connection to the hoop. Axial motion occurs naturally for inclined and horizontal tubulars in tidal flow and requires an extra vane attachment for vertical tubulars. Controlled tests in the marine environment suggest that the concept is nearly completely effective. The final design for the device which is being mass-produced is described.
A Methodology for the Determination of Drag Coefficients for Ice Floes
Authors: Madsen O. S. , Bruno M. S.
Published: November 2009

Governing equations are derived for the response of partially ice-covered continental shelf waters to atmospheric and tidal forcing. The assumptions underlying these equations are discussed, with emphasis on the physical processes represented by the air-ice and ice-water drag coefficients. Combining the equations that separately govern the water and ice floe motions, a coupled ice-water equation is obtained. The coupled equation reduces, under certain simplifying assumptions, to an equation involving only the air and water velocities relative to the ice velocity. This suggests an approximate but extremely simple methodology for the determination of drag coefficients for ice floes. The methodology is applied to data obtained during BASICS and MIZEX, and shown, in the former application, to yield drag coefficients comparable to those obtained from considerably more laborious methods.
Sub and Superharmonics in Natural Waves
Authors: Mansard E. P. D. , Sand S. E. , Klinting P.
Published: November 2009

Simulation of waves in numerical and physical models are often done using 1st-order linear waves; but recent investigations have shown that, under certain wave conditions, the magnitude of nonlinear waves present in a sea state can become important and necessitate the various models to include these nonlinearities. Investigations of a series of prototype records were therefore undertaken to establish the magnitude of these nonlinear waves for three different ranges of water depth. Analysis of these waves were also carried out in order to evaluate their effects on design parameters such as crest levels, velocities, etc.
Design Analysis of Ship Steering Gear Control Systems
Authors: Zheng J. Y. , Reid R. E.
Published: November 2009

The paper presents design analyses of ship steering gear control systems. Emphasis is placed on compressibility, leakage, friction, hydrodynamic damping, limiter and relay aspects of systems design. Computer simulation results are presented to assess the effect of design parameters on system performance for two different steering system/ship configurations. A design example is presented to show the main steps for designing a steering gear control system using single-loop bang-bang control with a variable capacity pump. The performance of the system is shown to be good.
Three-Dimensional Nonlinear Motions of Risers and Offshore Loading
Towers
Authors: O'Brien P. J. , McNamara J. F. , Dunne F. P. E.
Published: November 2009

A method is developed for the three-dimensional nonlinear motions of marine risers, pipelines and offshore loading towers. The technique is based on the finite element method and the separation of the rigid body motions and deformations of elements under conditions of finite rotations. The position of the riser is defined by a set of co-rotational axes and the evaluation of the finite rotations of this convected system is detailed. The method includes all nonlinear effects including geometry changes, bending-axial and bending-torsional coupling and follower forces and pressures. The computation of Morison-type loads is described with respect to three-dimensional axes. In order to verify the procedure numerical results are presented for the case of a vertical cantilever under bi-directional loading and axial torque; the results are shown to agree exactly with independent calculations. Results are also presented for an example from the literature on the three-dimensional response of an articulated tower to noncollinear waves and current.
A New Method for Calculation of the Position of Separation Points in
Two-Dimensional Flow Around Bodies at High Reynolds Number
Authors: Yang X.-C. , Moe G.
Published: November 2009

A method for analysis of separated flow about bluff bodies is presented. The emphasis is on boundary layer calculations and the determination of separation points. The wake flow in this project has been treated by point vortices, in accordance with a method presented by Sarpkaya and Shoaff. The wake model is not discussed herein, however. The boundary layer is treated by means of a Falkner-Skan transformation and the resulting differential equations are solved by a finite difference method. The external flow can change both in magnitude and direction, but so far only slow, gradual changes have been dealt with. The boundary layer model includes a laminar model and also, optionally, a simple model of turbulence. The flow very close to the separation point presents special problems. It has herein been modeled by a so-called triple-deck model, valid for laminar, subsonic flows.
Ultimate Strength and Post-Ultimate Strength Behavior of Damaged
Tubular Members in Offshore Structures
Authors: Yao T. , Taby J. , Moan T.
Published: November 2009

An idealized structural unit model is constructed to represent the pre and post-ultimate strength behavior of a damaged tubular member with various boundary conditions subjected to various end loads. Local denting and overall permanent lateral deflection are considered as a damage. The calculated results using this model are compared with a large number of previous and new experimental results. A parametric study regarding the influence of damages on the ultimate strength of tubular members is also performed.
Large-Scale Ice Strength Tests at Slow Strain Rates
Authors: Chen A. C. T. , Lee J.
Published: November 2009

In the winter of 1979/80, five petroleum companies participated in an Exxon Production Research Company program in which thirteen large-scale ice strength tests were conducted offshore in the vicinity of Prudhoe Bay. The purpose of the program was to determine the uniaxial compressive strength of annual sea ice as a function of strain rate and direction of loading with respect to preferred crystal alignment. Full ice sheet thickness test blocks with dimensions of 10 ft × 20 ft (3.05 m × 6.10 m) were cut free from the surrounding sheet ice. A hydraulic loading system with two million pounds of force capacity was used to compress the ice blocks at constant strain rates ranging from 10−7 s−1 to 10−5 s−1. Deformation in three orthogonal dimensions along with the axial had were measured and recorded throughout the test. This paper describes the field operations and test results, including uniaxial compressive strength, stiffness, Poisson’s ratio, and failure modes. Measured ice temperature, salinity and crystallographic structure are also presented.
Wave Forces Acting on a Moving Cylinder
Authors: Koterayama W. , Nakamura M.
Published: November 2009

Wave forces acting on a surging circular cylinder in regular waves are measured in a wave tank. Experiments are carried on various combinations of the amplitude of a wave and a surge, and the phase difference between them. The results of experiments are compared with those of calculations. The Morison equation extended to the case of relative motion is employed to calculate the forces on the cylinder. The inertia, added mass and drag coefficients used in the calculations are obtained from wave force measurements on a fixed cylinder and forced-surge tests in still water.
Thermal Buckling of Offshore Pipelines
Authors: Ju G. T. , Kyriakides S.
Published: November 2009

The vertical buckling of offshore pipelines caused by thermal loads is analyzed by modeling the pipeline as a long heavy beam resting on a rigid foundation. The axial restraint provided to the line by the surrounding soil is modeled as Coulomb friction. The study is concerned with the effect of localized, small initial geometric imperfections on the response and stability of the structure. In the presence of initial imperfections, the response is characterized by the temperature rise required to cause initial uplift and by a limit temperature rise beyond which the structure becomes unstable. Both of these critical values are shown to be sensitive to the form and magnitude of the imperfections as well as by the pipe material inelastic characteristics.
Fracture Toughness of Bohai Bay Sea Ice
Authors: Shen W. , Lin S.-Z.
Published: November 2009

In this paper linear elastic fracture mechanics is used to evaluate the fracture toughness of sea ice, which was collected from Bohai Bay and researched experimentally in the recent 84/85 winter. The value of fracture toughness and its trend under different loading rate is analyzed. Not only the fracture toughness of mode I is discussed, but also the fracture criterion of II and combined mode is firstly investigated. If the rate is not too low, the critical stress intensity factor KIIC does not vary with the variation of stress intensity factor rate K˙II. Experimental results of sea ice under combined fracture mode coincide well with the criterion obtained from the strain energy density factor theorem. But this theorem cannot be employed so well to determine the orientation of crack propagating tendency.
Steady Temperature in a Rotating Cylinder Subject to Surface Heating and Convective Cooling
Authors: Gecim B. , Winer W. O.
Published: November 2009

This study utilizes an integral transform technique in order to solve the heat conduction equation in cylindrical coordinates. The major assumption is the high speed (i.e., large Peclet number) assumption. The boundary value problem is governed by the parabolic form of the heat equation representing the quasi-stationary state. The boundary conditions are a combination of Neumann and mixed type due to simultaneous heating and cooling on the surface of the cylinder. The surface temperature reaches a peak value over the heat source and gradually decreases to a nearly constant level over the cooling zone. Thermal penetration in the radial direction is shown to be only a few percent of the radius, leaving the bulk of the body at a uniform temperature. The width of the heat source and the total heat input are shown to be effective on the level of temperature whereas the input distribution is shown to be unimportant. The dimensionless numbers involved are the Biot and the Peclet numbers where the solution is governed by the ratio of the Biot number to the square root of the Peclet number.
Interactions Among Friction, Wear, and System Stiffness—Part 3: Wear Model
Authors: Aronov V. , D’Souza A. F. , Kalpakjian S. , Shareef I.
Published: November 2009

It is shown that wear is an increasing function of system stiffness. The increase in the frequency of the applied load oscillations in normal direction causes increase of number of loading cycles per unit time that, in turn, causes increased rate of wear particles formation due to fatigue. A wear model has been developed which accounts for slider oscillation in the normal direction. Experimental data correlate very well with the theoretical analysis.
The Numerical Solution of Dynamically Loaded Elastohydrodynamic Contact as a Nonlinear Complementarity Problem
Authors: Oh Kong Ping
Published: November 2009

A numerical method has been developed for solving the nonlinear differential equation which arises in the elastohydrodynamic contact of bearing surfaces. This method is based upon the finite element approximation of the governing field equation, the Newton-Raphson algorithm for solving nonlinear systems, and the complementarity formulation of free-boundary problems. The lubricated contact between a sphere and a semi-infinite half-space under dynamic loading is analyzed as an illustrative problem.
Assessing the Effect of Stylus Tip Radius and Flight on Surface Topography Measurements
Authors: McCool J. I.
Published: November 2009

The mean square height, slope, and curvature are characteristics of roughness microgeometry that govern the performance of real surfaces in elastic contact. The values of these quantities deduced from stylus profile traces are distorted by the nonlinear filtering effect of the finite stylus tip and by the failure, at high enough tracing speeds of the stylus to maintain contact with the profile being traced. This paper describes the development of a simulation model for assessing the magnitude of this distortion as well as the effect of record length and sampling frequency with tracing profiles that are realizations of a random process having a specified spectrum. Illustrative parametric runs of the model are discussed.
An Approximate Analysis of the Temperature Conditions in a Journal Bearing. Part II: Application
Authors: Lund J. W. , Tonnesen J.
Published: November 2009

To test the validity of the theory, described in Part I of this investigation, calculations are performed for a cylindrical, two-axial groove journal bearing over a range of loads and speeds. The results give the temperature distribution in the lubricant film and in the bearing sleeve, the journal surface temperature, the heat balance for the bearing, the journal center eccentricity, and the film pressure profile. The calculated results are compared with experimental measurements, and although significant discrepancies are observed, the overall agreement is satisfactory, considering the usual tolerance effects and the uncertainties in defining some of the design parameters
Hydrodynamic Lubrication of the Rib-Roller End Contact of a Tapered Roller Bearing
Authors: Gadallah Nabil , Dalmaz Gerard
Published: November 2009

The behavior of the lubricated rib-roller end contact of a tapered roller bearing is studied both theoretically and experimentally. A theoretical hydrodynamic approach was first developed for smooth and rigid surfaces for the particular geometry and kinematic conditions found in this contact. Simultaneous measurements of traction forces and film thicknesses by optical interferometry are performed in a special device made of a flat glass disk and a steel toric specimen which simulates this contact, lubricated with a mineral oil at ambient temperature. Good argeement is noted for both film thickness and traction forces between the hydrodynamic theoretical and experimental results. The experiments which are extended to the elasto-hydrodynamic regime show that central and minimum film thicknesses are lower than the calculated values using classical fully flooded and starved elastohydrodynamic theories. This departure is attributed to side flow effects. Traction curves obtained in this regime, under moderate pressures, show that the oil behavior remains newtonian.
Non-Newtonian Fluid Model Incorporated Into Elastohydrodynamic Lubrication of Rectangular Contacts
Authors: Jacobson B. O. , Hamrock B. J.
Published: November 2009

A procedure is outlined for the numerical solution of the complete elastohydrodynamic lubrication of rectangular contacts incorporating a non-Newtonian fluid model. The approach uses a Newtonian model as long as the shear stress is less than a limiting shear stress. If the shear stress exceeds the limiting value, the shear stress is set equal to the limiting value. The numerical solution requires the coupled solution of the pressure, film shape, and fluid rheology equations from the inlet to the outlet. Isothermal and no-side-leakage assumptions were imposed in the analysis. The influence of dimensionless speed U, load W, materials G, and sliding velocity U* and limiting-shear-strength proportionality constant γ on dimensionless minimum film thickness Hmin was investigated. Fourteen cases were investigated for an elastohydrodynamically lubricated rectangular contact incorporating a non-Newtonian fluid model. The influence of sliding velocity (U*) and limiting shear strength (γ) on minimum film thickness was observed to be small. Hence the film thickness equation obtained for a Newtonian fluid is sufficient for calculations considering non-Newtonian effects. Computer plots are also presented that indicate in detail pressure distribution, film shape, shear stress at the surfaces, and flow throughout the conjunction.
An Application of a Free Volume Model to Lubricant Rheology I—Dependence of Viscosity on Temperature and Pressure
Authors: Yasutomi S. , Bair S. , Winer W. O.
Published: November 2009

Analyses of the dependence of lubricant viscosity on temperature and pressure, μ(T,P), have been carried out by using a modified WLF equation in which pressure effects on viscosity are given in terms of the pressure dependence of the glass transition temperature, Tg, and of thermal expansivity of free volume, αf. logμ(T,P)=logμg−C1•(T−Tg(P))•F(P)C2+(T−Tg(P))•F(P) where C1 and C2 are well known WLF constants, and μg is a viscosity at Tg. Tg(P) and F(P) are functions for describing the pressure dependence of Tg and αf, respectively. On the basis of the iso-viscous concept for Tg(P), μg has been assumed to have a constant value, 1 TPa•s, at any pressure (SCHEME I). SCHEME I yields a reasonable variation in Tg and αf with pressure for synthetic lubricants, while this analysis suggests a lower μg for mineral oils. In order to improve the applicability of the free volume model, a reference temperature Ts(P), at which the viscosity is 10 MPa•s, has been introduced instead of Tg(P) (SCHEME II). Analyses of dielectric transition for some lubricants and of μ(T,P) in the ASME Pressure-Viscosity Report have confirmed the excellent applicability of the present free volume model over wide ranges of temperature and pressure.
An Application of a Free Volume Model to Lubricant Rheology 2—Variation in Viscosity of Binary Blended Lubricants
Authors: Yasutomi S. , Bair S. , Winer W. O.
Published: November 2009

The modified WLF equation developed in Part 1 was applied to the variation in viscosity, μ(T,P), for two series of binary blended lubricants containing a common synthetic diester (di(2ethylhexyl)sebacate) in a polyphenyl ether (5P4E) and in a naphthenic mineral oil (N1). Dilatometric observations and the viscosity analysis indicate that the relations needed to predict the pressure functions in the modified WLF equation for the binary mixture can be obtained from those of respective components. These relations allow us to estimate μ(T,P) of a binary blended lubricant without measurements of the high pressure viscosity of the blend. For practical applications, the modified WLF equation may also be useful for predicting μ(T,P) of blended lubricant products.
A Numerical Assessment of the Effect of Striated Roughness on Gas Lubrication
Authors: To̸nder K.
Published: November 2009

Based upon the assumption that Reynolds’ equation holds in the presence of roughness, the present work establishes that the film thickness averages previously derived for incompressible lubrication with striated roughness are correct for gas lubrication as well. This result has been obtained by solving the Reynolds equation proper, for sample bearings having sinusoidal grooves in or across the direction of motion, and comparing the ensuing pressure profiles with limiting forms. The clear trend of these comparisons is strengthened by the very close correspondence between the directly computed pressure and mean or “expected” pressures obtained from modified Reynolds equations in which the average film heights found for incompressible lubrication have been used.
Pumping Action of Aligned Smooth Face Seals Due to Axial Vibrations—Theory
Authors: Kaneta M. , Jinnouchi Y. , Fukahori M.
Published: November 2009

This is an analytical study of the mechanism of pumping action produced in two axially symmetrical disks. The disks have a continuous parallel film thickness between them, and one of them has a recess at the center and is subjected to a normal sinusoidal oscillation. It is found out that whether the pumping action is inward or outward depends upon a shift of phase between a variation of flow resistance due to a periodic fluctuation of the film thickness between seal faces and a variation of pressure in the recess.
Influence of the Thermal Field on the Resistance Law in the Turbulent Bearing-Lubrication Theory
Authors: Di Pasquantonio F. , Sala R.
Published: November 2009

In recent years, a joint theoretical and experimental research programme has been carried out by ANSALDO, ENEL, and the Department of Mechanics of the Milan Polytechnic. The purpose of this paper is to investigate the effects of the thermal field on the resistance law. In particular, a study is made of the behavior of the lubricating film of an infinite and inclined-plane slider-bearing, using a turbulence model similar to that employed by Launder and Leschziner. In our method, the complete boundary layer equations of mass, momentum, and energy are solved numerically, by a finite-difference technique in the plane normal to the sliding surface. The equations are discretized on a staggered grid, in which the scalar quantities (pressure, viscosity, and temperature) are located at the nodes and the velocity components between them. Having assumed arbitrary distribution of velocity at the inlet and pressure distribution, the set of conservation equations can be solved at the downstream stations. Since the velocity field obtained does not satisfy the global mass conservation law at every station, a Poisson-type equation for pressure correction is derived by imposing such a mass conservation condition. Velocity and pressure distribution at the inlet are then corrected, and a new computation performed. This iterative procedure is repeated until the solution is no longer significantly modified. The numerical results show that the resistance coefficients obtained taking into account the thermal field, are lower than those obtained in isothermal conditions.
The Film Thickness in Piezoviscous-Rigid Regime; Film Thickness Lubrication Regimes Transition Criteria
Authors: Houpert L.
Published: November 2009

A new general formula is proposed to calculate the lubricant film thickness in the piezoviscous rigid lubrication regime. Equivalent radii ratio, load, speed, and material dimensionless parameters are included. New general criteria to decide whether piezoviscous rigid or EHD (elasto-hydrodynamic) or isoviscous elastic lubrication film thickness formulas have to be used are proposed. Comparisons with some other published results are made.
The Division of Frictional Heat—A Guide to the Nature of Sliding Contact
Authors: Berry G. A. , Barber J. R.
Published: November 2009

The work of Jaeger [1] and Barber [2] indicates that the division of frictional heat between sliding solids should be sensitive to the interfacial boundary conditions. Thus it should provide a guide to the nature of asperity interactions and a more accurate statement of the boundary conditions for any subsequent analysis. Measurement of the division of heat in a symmetric “cylinder on cylinder” system was frustrated by the widespread occurrence of thermoelastic instability. An alternative specimen geometry has been developed which has permitted the division of heat between sliding solids of various materials to be investigated experimentally. The characteristics of the microscopic thermal resistance at the surface of a sliding solid have been investigated theoretically for several types of asperity interaction. An approximate method has been employed to estimate the thermal resistance of an oxidized surface. The observed division of heat is interpreted with reference to the characteristic behavior associated with the various types of asperity interaction. It is shown that in the mild wear regime oxide films have an appreciable effect on the microscopic thermal resistance and hence, on the thermal behavior of the sliding solids, particularly the division of heat between them.
Analytical Curve Fits for Solution Parameters of Dynamically Loaded Journal Bearings
Authors: Goenka P. K.
Published: November 2009

The mobility method of solution is frequently used for analyzing dynamically loaded journal bearings. Curve fits of journal-bearing solutions are used in this method. All the currently available curve fits are lacking in one or more of three important features—the solution accuracy, the solution detail, and the solution time. A new set of analytical curve fits is presented in this paper. The set includes: the two components of mobility vectors, location and magnitude of maximum film pressure, and the starting and finishing angles of the pressure curve. For an ideal journal bearing, the new curve fits give accuracy and solution detail comparable to an expensive finite-element analysis, while keeping the solution time comparable to that required for the short-bearing approximation. An example is presented to demonstrate the use of the new curve fits.
The Hydrodynamic Lubrication of Rough Surfaces Based on a New Perturbation Approach
Authors: To̸nder Kristian
Published: November 2009

A new method for treating roughness problems in hydrodynamic lubrication is presented. The approach consists of an expansion of the pressure by means of the perturbation parameter ε which is the ratio of the characteristic wavelengths across and along the direction of motion, respectively. This parameter may also be interpreted as the inverse of the Peklenik number of the surface texture. It is found that the zeroth components are those of To̸nder’s approximate theory. The terms are modified so as to remain finite at infinite ε. It is demonstrated that the corrections thus obtained are very accurate for configurations which are not disconnected pockets, even for very large roughness amplitudes. Such pockets are well treated, however, for moderate roughnesses. The method is applicable to statistically symmetric cases and may be easily extended to two-sided roughness. The application of the approach is quite straightforward numerically and does not require the boundary conditions of sample roughnesses to be known.
Applying Quasi-Linearization to the Problem of Steady Laminar Flow of a Second Grade Fluid Between Two Rotating Porous Disks
Authors: Verma P. D. , Sharma P. R. , Ariel P. D.
Published: November 2009

The problem of steady laminar flow of an incompressible second grade fluid between two rotating porous disks has been investigated. The equations of motion are solved by regular perturbation method for small suction/injection parameter and by the quasilinearization method for higher values of suction/injection parameter. The results from both the methods have been compared for both the Newtonian and Non-Newtonian fluids. The effects of suction/injection parameter, rotation parameter and visco-elastic parameter on the velocity components and skin friction have been discussed numerically and shown graphically.
Computer-Aided Study of Journal Bearings With Undulating Surfaces
Authors: Mokhtar M. O. A. , Aly W. Y. , Shawki G. S. A.
Published: November 2009

This paper presents the results of an analytical study of the performance of a cylindrical journal bearing of finite length as influenced by undulations intentionally produced on the surface. With the aid of a digital computer, the analysis has been applied to some common cases to obtain relevant numerical solutions. Compared with journal bearings having perfectly smooth surfaces, wavy bearings may well run at lower values of journal eccentricities and attitude angles. Wavy bearings may thus operate with higher safety. It is herein also established that, with load criterion as parameter, the higher the wave amplitude ac and the number of waves along the bearing circumference nc, the lower would be the eccentricity ratio. Moreover, when running at same eccentricity, higher values of ac and nc show a tendency of the journal center to move closer to the load line, thus leading to lower attitude angles.
On Slip Flow Considerations in Gas-Lubricated Porous Bearings
Authors: Malik M. , Rodkiewicz Cz. M.
Published: November 2009

A modified form of Reynolds equation is derived for the compressible lubrication of porous bearings. The analysis takes into account two kinds of nonadherence conditions on the sliding surfaces, namely, the slip flow under the influence of molecular mean free path and the slip flow at gas film-porous shell interface. Numerical results are presented to illustrate the relative effects of the two kinds of slip flow conditions on static characteristics of self acting journal bearings.
Thermal Elastohydrodynamic Lubrication of Rider Rings
Authors: Simon Vilmos
Published: November 2009

The full thermal elastohydrodynamic analysis of the lubrication of rider rings is presented. A numerical solution of the coupled Reynolds, elasticity, energy, and Laplace’s equations for the oil film thickness, pressure, and temperature and rider rings temperatures is obtained. The temperature variation across the oil film is included. The real rider ring geometry is treated. The effect of the operating conditions on the performance characteristics is discussed.
CFD Modeling and X-Ray Imaging of Biomass in a Fluidized Bed
Authors: Deza Mirka , Franka Nathan P. , Heindel Theodore J. , Battaglia Francine
Published: November 2009

Computational modeling of fluidized beds can be used to predict the operation of biomass gasifiers after extensive validation with experimental data. The present work focused on validating computational simulations of a fluidized bed using a multifluid Eulerian–Eulerian model to represent the gas and solid phases as interpenetrating continua. Simulations of a cold-flow glass bead fluidized bed, using two different drag models, were compared with experimental results for model validation. The validated numerical model was then used to complete a parametric study for the coefficient of restitution and particle sphericity, which are unknown properties of biomass. Biomass is not well characterized, and so this study attempts to demonstrate how particle properties affect the hydrodynamics of a fluidized bed. Hydrodynamic results from the simulations were compared with X-ray flow visualization computed tomography studies of a similar bed. It was found that the Gidaspow (blending) model can accurately predict the hydrodynamics of a biomass fluidized bed. The coefficient of restitution of biomass did not affect the hydrodynamics of the bed for the conditions of this study; however, the bed hydrodynamics were more sensitive to particle sphericity variation.
Pressure Drop in Laminar Developing Flow in Noncircular Ducts: A Scaling and Modeling Approach
Authors: Muzychka Y. S. , Yovanovich M. M.
Published: November 2009

A detailed review and analysis of the hydrodynamic characteristics of laminar developing and fully developed flows in noncircular ducts is presented. New models are proposed, which simplify the prediction of the friction factor–Reynolds product f Re for developing and fully developed flows in most noncircular duct geometries found in heat exchanger applications. By means of scaling analysis it is shown that complete problem may be easily analyzed by combining the asymptotic results for the short and long ducts. Through the introduction of a new characteristic length scale, the square root of cross-sectional area, the effect of duct shape has been minimized. The new model has an accuracy of ±10% or better for most common duct shapes when nominal aspect ratios are used, and ±3% or better when effective aspect ratios are used. Both singly and doubly connected ducts are considered.
Slow Release of Nitric Oxide from Charged Catheters and Its Effect on Biofilm Formation byEscherichia coli
Authors: Regev-Shoshani Gilly , Ko Mary , Miller Chris , Av-Gay Yossef
Published: November 2009

Catheter-associated urinary tract infection is the most prevalent cause of nosocomial infections. Bacteria associated with biofilm formation play a key role in the morbidity and pathogenesis of these infections. Nitric oxide (NO) is a naturally produced free radical with proven bactericidal effect. In this study, Foley urinary catheters were impregnated with gaseous NO. The catheters demonstrated slow release of nitric oxide over a 14-day period. The charged catheters were rendered antiseptic, and as such, were able to prevent bacterial colonization and biofilm formation on their luminal and exterior surfaces. In addition, we observed that NO-impregnated catheters were able to inhibit the growth ofEscherichia coliwithin the surrounding media, demonstrating the ability to eradicate a bacterial concentration of up to 104CFU/ml.
Dose Escalation Study of the Safety, Tolerability, and Pharmacokinetics of Nemonoxacin (TG-873870), a Novel Potent Broad-Spectrum Nonfluorinated Quinolone, in Healthy Volunteers
Authors: Lin Luke , Chang Li-Wen , Tsai Cheng-Yuan , Hsu Ching-Hung , Chung David T. , Aronstein William S. , Ajayi Funmi , Kuzmak Barbara , Lyon Robert A.
Published: November 2009

Nemonoxacin (TG-873870) is a novel nonfluorinated quinolone with potent broad-spectrum activity against Gram-positive and Gram-negative pathogens, including methicillin-resistant
Staphylococcus aureus
, penicillin- and quinolone-resistant
Streptococcus pneumoniae
, and vancomycin-intermediate and vancomycin-resistant
Staphylococcus aureus
. The safety, tolerability, and pharmacokinetics of nemonoxacin were investigated in a double-blind, ascending-single-dose study involving 56 healthy subjects (48 males and 8 females) who were randomly assigned to 1 of 7 dose cohorts. In each successive cohort, two subjects received a placebo and six received single oral doses of 25, 50, 125, 250, 500, 1,000, or 1,500 mg nemonoxacin. Nemonoxacin was well tolerated up to the maximum dose of 1,500 mg. No severe or serious adverse events were observed. The most frequent adverse events were contact dermatitis, pruritus, and erythema. No clinically significant abnormalities were noted in the electrocardiograms, vital signs, or laboratory tests. The plasma concentrations increased over the dose range, and at 500 mg, the free area under the plasma concentration-time curve/MIC
90
ratios and free maximum nemonoxacin concentration/MIC
90
ratios against drug-sensitive/drug-resistant
S. pneumoniae
and
S. aureus
were greater than 227 and 24, respectively. The peak time and elimination half-life of nemonoxacin were 1 to 2 h and 9 to 16 h, respectively. The oral clearance was approximately 0.22 liter/h/kg. The plasma protein binding was approximately 16%. The results of this study support further evaluation of the multiple-dose safety, tolerability, and pharmacokinetics of nemonoxacin.
Multiple-Dose Safety, Tolerability, and Pharmacokinetics of Oral Nemonoxacin (TG-873870) in Healthy Volunteers
Authors: Chung David T. , Tsai Cheng-Yuan , Chen Shu-Jen , Chang Li-Wen , King Chi-Hsin R. , Hsu Ching-Hung , Chiu Kit-Mui , Tan Hao-Chen , Chang Yu-Ting , Hsu Ming-Chu
Published: November 2009

Nemonoxacin (TG-873870) is a novel nonfluorinated quinolone with broad-spectrum activities against Gram-positive and Gram-negative aerobic, anaerobic, and atypical pathogens, as well as against methicillin-resistant
Staphylococcus aureus
, vancomycin-resistant
S. aureus
, and multiple-resistant bacterial pathogens. We conducted a randomized, double-blind, placebo-controlled, dose-escalating study to ascertain the safety, tolerability, and pharmacokinetics of nemonoxacin. We enrolled 46 healthy volunteers and used a once-daily oral-dosing range of 75 to 1,000 mg for 10 days. Additionally, the food effect was evaluated in subjects in the 500-mg cohort. Nemonoxacin was generally safe and well tolerated, with no significant changes in the clinical laboratory tests or electrocardiograms. Adverse effects, including headache, contact dermatitis, and rash, were mild and resolved spontaneously. Nemonoxacin was rapidly absorbed within 2 h postdosing, and generally, a steady state was reached after 3 days. The maximum plasma concentration and the area under the plasma concentration-time curve were dose proportional over the dosing range. The elimination half-life was approximately 7.5 h and 19.7 h on days 1 and 10, respectively. Approximately 37 to 58% of the drug was excreted in the urine. Food affected the pharmacokinetics, with decreases in the maximum plasma concentration and area under the plasma concentration-time curve of 46% and 27%, respectively. However, the free AUC/MIC
90
of nemonoxacin was more than 100 under both the fasting and fed conditions, predicting the efficacy of nemonoxacin against most of the tested pathogens. In conclusion, the results support further clinical investigation of once-daily nemonoxacin administration for antibiotic-sensitive and antibiotic-resistant bacterial infections.
In Vitro Activity of CEM-101 against
Streptococcus pneumoniae
and
Streptococcus pyogenes
with Defined Macrolide Resistance Mechanisms
Authors: McGhee Pamela , Clark Catherine , Kosowska-Shick Klaudia M. , Nagai Kensuke , Dewasse Bonifacio , Beachel Linda , Appelbaum Peter C.
Published: November 2009

CEM-101 had MIC ranges of 0.002 to 0.016 μg/ml against macrolide-susceptible pneumococci and 0.004 to 1 μg/ml against macrolide-resistant phenotypes. Only 3 strains with
erm
(B), with or without
mef
(A), had CEM-101 MICs of 1 μg/ml, and 218/221 strains had CEM-101 MICs of ≤0.5 μg/ml. CEM-101 MICs were as much as 4-fold lower than telithromycin MICs against all strains. For
Streptococcus pyogenes
, CEM-101 MICs ranged from 0.008 to 0.03 μg/ml against macrolide-susceptible strains and from 0.015 to 1 μg/ml against macrolide-resistant strains. Against
erm
(B) strains, erythromycin, azithromycin, and clarithromycin MICs were 32 to >64 μg/ml, while 17/19 strains had telithromycin MICs of 4 to 16 μg/ml; CEM-101 MICs were 0.015 to 1 μg/ml. By comparison,
erm
(A) and
mef
(A) strains had CEM-101 MICs of 0.015 to 0.5 μg/ml, clindamycin and telithromycin MICs of ≤1 μg/ml, and erythromycin, azithromycin, and clarithromycin MICs of 0.5 to >64 μg/ml. Pneumococcal multistep resistance studies showed that although CEM-101 yielded clones with higher MICs for all eight strains tested, seven of eight strains had clones with CEM-101 MICs that rose from 0.004 to 0.03 μg/ml (parental strains) to 0.06 to 0.5 μg/ml (resistant clones); for only one
erm
(B)
mef
(A) strain with a parental MIC of 1 μg/ml was there a resistant clone with a MIC of 32 μg/ml, with no detectable mutations in the L4, L22, or 23S rRNA sequence. Among two of five
S. pyogenes
strains tested, CEM-101 MICs rose from 0.03 to 0.25 μg/ml, and only for the one strain with
erm
(B) did CEM-101 MICs rise from 1 to 8 μg/ml, with no changes occurring in any macrolide resistance determinant. CEM-101 had low MICs as well as low potential for the selection of resistant mutants, independent of bacterial species or resistance phenotypes in pneumococci and
S. pyogenes
.
Echinocandin Susceptibility Testing ofCandidaSpecies: Comparison of EUCAST EDef 7.1, CLSI M27-A3, Etest, Disk Diffusion, and Agar Dilution Methods with RPMI and IsoSensitest Media
Authors: Arendrup Maiken Cavling , Garcia-Effron Guillermo , Lass-Flörl Cornelia , Lopez Alicia Gomez , Rodriguez-Tudela Juan-Luis , Cuenca-Estrella Manuel , Perlin David S.
Published: November 2009

This study compared nine susceptibility testing methods and 12 endpoints for anidulafungin, caspofungin, and micafungin with the same collection of blindedFKShot spot mutant (n= 29) and wild-type isolates (n= 94). The susceptibility tests included EUCAST Edef 7.1, agar dilution, Etest, and disk diffusion with RPMI-1640 plus 2% glucose (2G) and IsoSensitest-2G media and CLSI M27A-3. Microdilution plates were read after 24 and 48 h. The following test parameters were evaluated:fkshot spot mutants overlapping the wild-type distribution, distance between the two populations, number of very major errors (VMEs;fksmutants misclassified as susceptible), and major errors (MEs; wild-type isolates classified as resistant) using a wild-type-upper-limit value (WT-UL) (two twofold-dilutions higher than the MIC50) as the susceptibility breakpoint. The methods with the lowest number of errors (given as VMEs/MEs) across the three echinocandins were CLSI (12%/1%), agar dilution with RPMI-2G medium (14%/0%), and Etest with RPMI-2G medium (8%/3%). The fewest errors overall were observed for anidulafungin (4%/1% for EUCAST, 4%/3% for CLSI, and 3%/9% for Etest with RPMI-2G). For micafungin, VME rates of 10 to 71% were observed. For caspofungin, agar dilution with either medium was superior (VMEs/MEs of 0%/1%), while CLSI, EUCAST with IsoSensitest-2G medium, and Etest were less optimal (VMEs of 7%, 10%, and 10%, respectively). Applying the CLSI breakpoint (S ≤ 2 μg/ml) for CLSI results, 89.2%fkshot spot mutants were classified as anidulafungin susceptible, 60.7% as caspofungin susceptible, and 92.9% as micafungin susceptible. In conclusion, no test was perfect, but anidulafungin susceptibility testing using the WT-UL to define susceptibility reliably identifiedfkshot spot mutants.
Identification of a Claudin-4 Residue Important for Mediating the Host Cell Binding and Action of
Clostridium perfringens
Enterotoxin
Authors: Robertson Susan L. , Smedley James G. , McClane Bruce A.
Published: November 2009

The 24-member claudin protein family plays a key role in maintaining the normal structure and function of epithelial tight junctions. Previous studies with fibroblast transfectants and naturally sensitive Caco-2 cells have also implicated certain claudins (e.g., Claudin-4) as receptors for
Clostridium perfringens
enterotoxin (CPE). The present study first provided evidence that the second extracellular loop (ECL-2) of claudins is specifically important for mediating the host cell binding and cytotoxicity of native CPE. Rat fibroblast transfectants expressing a Claudin-4 chimera, where the natural ECL-2 was replaced by ECL-2 from Claudin-2, exhibited no CPE-induced cytotoxicity. Conversely, CPE bound to, and killed, CPE-treated transfectants expressing a Claudin-2 chimera with a substituted ECL-2 from Claudin-4. Site-directed mutagenesis was then used to alter an ECL-2 residue that invariably aligns as N in claudins known to bind native CPE but as D or S in claudins that cannot bind CPE. Transfectants expressing a Claudin-4
N149D
mutant lost the ability to bind or respond to CPE, while transfectants expressing a Claudin-1 mutant with the corresponding ECL-2 residue changed from D to N acquired CPE binding and sensitivity. Identifying carriage of this N residue in ECL-2 as being important for native CPE binding helps to explain why only certain claudins can serve as CPE receptors. Finally, preincubating CPE with soluble recombinant Claudin-4, or Claudin-4 fragments containing ECL-2 specifically blocked the cytotoxicity on Caco-2 cells. This result opens the possibility of using receptor claudins as therapeutic decoys to ameliorate CPE-mediated intestinal disease.