bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental Load Effect Analysis of Guyed Towers
Authors: Mo O. , Moan T.
Published: November 2009

A general method for dynamic load effect analysis of slender offshore structures subjected to short crested random waves, current and wind, is given. The structure is represented by a three-dimensional space frame model utilizing dash-pots and linear or nonlinear spring elements to represent guy lines and coupling between structure and foundation. The component mode synthesis formulation is adopted for reduction of the number of degrees of freedom. The hydrodynamic forces are computed by Morison’s equation, accounting for finite wave elevation, directionality, and relative fluid-structure motion. Various kinematic models for the fluid field in the splashing zone are compared. To get a reasonable representation of nonlinearities in the loading and the structural model, a Monte Carlo approach is adopted. Starting with simulated samples of the random fluid field and wind forces, time series of structural responses are found by numerical time integration utilizing the Newmark β-family of time integration operators. Numerical results for a guyed tower at 450-m water depth are presented. The statistical uncertainties associated with the stochastic time domain simulations are discussed. A significant discrepancy is found between linearized frequency domain solutions and the present nonlinear time domain formulation. The importance of an adequate representation of superharmonic responses is particularly discussed. The differences in results due to various solution methods are found to vary significantly with sea-state conditions.
Stress Distribution Formulas and Comparison of Three Stress Analysis Techniques for Tubular Joints
Authors: Dharmavasan S. , Dover W. D.
Published: November 2009

The available data on hot spot stress for tubular welded joints has been reviewed and a database established. Stress analysis techniques in general use for the design of offshore structures and parametric equations have been assessed against this database to determine their accuracy. A set of equations to predict the stress distributions for simple joints has been proposed and has been used to predict mixed mode stress concentration factors. Results obtained from a complex K joint have been examined in detail and the importance of the stress state, when predicting the mixed mode stress concentration factors, is demonstrated.
Fundamental Research on Oscillating Water Column Wave Power Absorbers
Authors: Maeda H. , Kinoshita T. , Masuda K. , Kato W.
Published: November 2009

An oscillating water column (OWC) wave power absorber is one of the most promising devices, as well as the Salter Duck and the Clam. This paper presents a simple prediction method, in which the equivalent floating body approximation is used, for absorbing wave power characteristics of an oscillating water column device. The effects of the compressibility of air and inertia of an air turbine and electric generator on absorbed wave power are obtained by using the equivalent electric circuit concept. Both the experimental and theoretical studies are carried out in this paper.
A Summary of the Strength and Modulus of Ice Samples From Multi-Year Pressure Ridges
Authors: Cox G. F. N. , Richter J. A. , Weeks W. F. , Mellor M.
Published: November 2009

Over two hundred unconfined compression tests were performed on vertical ice samples obtained from 10 multi-yr pressure ridges in the Beaufort Sea. The tests were performed on a closed-loop electrohydraulic testing machine at two strain rates (10−5 and 10−3 s−1) and two temperatures (−20° and −5°C). This paper summarizes the sample preparation and testing techniques used in the investigation and presents data on the compressive strength and initial tangent modulus of the ice.
The Design, Installation, and Performance of a Berm-Supported Exploration Structure in the Beaufort Sea
Authors: Hewitt K. J. , Berzins W. E. , Fitzpatrick J. P. , Hogeboom H. G.
Published: November 2009

The design, installation, and performance of a berm-supported exploration structure in a dynamic ice environment is presented. Details are provided on design considerations which include horizontal ice loads, wave loads, seismic considerations, foundation characteristics and extreme temperatures. The development of specifications and installation techniques to account for these design concerns is presented. A case history is presented which includes a discussion of on-site modifications to the idealized placement technique, which were necessitated by extreme ice conditions. The success of this modified placement technique is confirmed through a review of the units performance during the drilling season, and the response of the structure to dynamic ice and drilling-related activity is examined.
New Efficient and Accurate Method of Nonlinear Analysis of Offshore Tubular Frames (the Idealized Structural Unit Method)
Authors: Ueda Y. , Rashed S. M. H. , Nakacho K.
Published: November 2009

The Idealized Structural Unit Method [1, 2] is applied to the analysis of nonlinear behavior of three-dimensional offshore tubular frames. To this purpose the “tubular structural unit” is developed and used to analyze the entire behavior of the frame until final collapse. In this method large deflections, instability, plasticity and the effect of residual stresses and initial out of straightness are considered. Modeling of a structure is very simple since large structural units are regarded as elements. The required computer effort is very small while attaining a high degree of accuracy and reliability.
Vortex-Induced Response of a Flexible Cylinder in a Constant Current
Authors: Patrikalakis N. M. , Chryssostomidis C.
Published: November 2009

In this paper we develop a method for the theoretical prediction of the static and lift responses of a flexible cylinder in a unidirectional constant current. Our theoretical prediction is based on information derived from experimental results involving rigid cylinders forced to oscillate sinusoidally orthogonally to a uniform stream. Our approach allows the prediction of a number of, independently determined, monochromatic, and multimode dynamic solutions. For each such multimode solution our procedure allows the simultaneous evaluation of lift response frequency, amplitude and phase between modes. Numerical examples assuming monomodal solutions are included to allow comparison of our theoretical predictions with experimental and other published theoretical results.
Nonlinear Inverse Perturbation in Structural Dynamics Redesign of Risers
Authors: Bernitsas M. M. , Hoff C. J. , Kokarakis J. E.
Published: November 2009

Marine risers, and offshore structures in general, may have undesirable natural frequencies and/or mode shapes. Structural redesign is mandatory in such cases. An Inverse Perturbation Redesign (IPR) method, which uses only the finite element analysis of the baseline system and was developed in previous work for general structures, is extended in this work to handle systems with geometric stiffness matrices like marine risers. The IPR method is currently applicable to undamped structural systems or systems with Rayleigh damping and is valid for large or small changes which are frequently required to change modal characteristics of offshore structures. The vibratory characteristics of risers can be altered by modifying among others, the riser top tension, the drilling mud density and the geometry of the riser tubes. The effects of their change on the riser frequencies and modes are derived and applied to two typical riser redesign problems using the IPR method.
Oxides of Nitrogen: Formation and Control in Resource Recovery Facilities
Authors: Russell S. H. , Roberts J. E.
Published: November 2009

The control of emissions of oxides of nitrogen from resource recovery facilities is becoming an increasingly important consideration in environmental permitting of new facilities. California presently has strict emission standards in place and other states are considering such standards. This paper reviews the theory of solid fuel combustion, and NOx formation and control in the context of solid waste combustion. The paper further discusses available control technology and its application to facilities burning solid waste.
Collisions and Damage of Offshore Structures: A State-of-the-Art
Authors: Ellinas C. P. , Valsgard S.
Published: November 2009

Over the recent years, following the very rapid increase in the construction and installation of offshore structures, there has been a considerable growth of interest in the assessment of the probabilities and consequences of collision and damage of such structures. This is reflected by the very large number of papers published over the last 15 yr and the multitude of conferences and meetings held on the subject. Many research programs have been completed or are in progress at many centers and institutions over the world. Accidental loading and damage are now accepted design parameters recommended for consideration in a number of Codes for the design in offshore structures. This paper reviews the state-of-the-art with respect to the probabilities and consequences of collisions and accidental loading in general, and methods for the assessment of the design of steel offshore structures against damage. Most of the available information in the field of offshore collisions and accidental loading emanates from research and experience related to ship safety. However, in this paper emphasis is placed on research activity and available information concerned with offshore structures, such as platforms, semisubmersibles, etc. There is a considerable amount of information available on methods for evaluating the extent and effects on damage of these structures and in estimating their residual strength in the damaged condition. As this is an area currently of major interest in the offshore industry, the paper presents comprehensive information and some new results relating to all major structural components. The state-of-the-art with regards to methods and principles for design against damage is also reviewed and commented upon. The paper concludes with general recommendations and indications of areas where future research could be most usefully directed.
Recent Advances in High-Frequency Wave Forces on Fixed Structures
Authors: Chakrabarti S. K.
Published: November 2009

The computation of wave forces is one of the most vital tasks in the design of offshore structures. Many analytical tools are available for the determination of wave effects on offshore structures. These methods may be divided into two major categories: one for small members of an offshore structure and one for large members. A hybrid method is used for structures that have both types of members. The advances made in the last few years in the specific area of computing the high-frequency forces are reviewed here.
Grain Size and the Compressive Strength of Ice
Authors: Cole D. M.
Published: November 2009

This work presents the results of uniaxial compression tests on freshwater polycrystalline ice. Grain size of the test material ranged from 1.5 to 5 mm, strain rate ranged from 10−6 to 10−2 s−1 and the temperature was −5°C. The grain size effect emerged clearly as the strain rate increased to 10−5 s−1 and persisted to the highest applied strain rates. On average, the stated increase in grain size brought about a decrease in peak stress of approximately 31 percent. The occurrence of the grain size effect coincided with the onset of visible cracking. The strength of the material increased to a maximum at a strain rate of 10−3 s−1, and then dropped somewhat as the strain rate increased further to 10−2 s−1. Strain at peak stress generally tended to decrease with both increasing grain size and increasing strain rate. The results are discussed in terms of the deformational mechanisms which lead to the observed behavior.
Effects of Surface Mass Transfer on Free Convection Flow Over Vertical Cylinder Embedded in a Saturated Porous Medium
Authors: Huang M.-J. , Chen C.-K.
Published: November 2009

The heat-transfer characteristics for free convection associated with isothermal vertical cylinder with surface mass transfer (blowing or suction) embedded in a saturated porous medium are analyzed. The nonsimilar equations are solved by using a suitable variable transformation and employing an implicit finite difference method. The numerical results for Nusselt number are expressed as functions of the parameters, ξ and γ, which represent the effects of the cylinder curvature and the surface mass transfer, respectively. It is found that the local Nusselt numbers for a vertical cylinder are less sensitive to the surface mass transfer than those for a vertical plate. Blowing of mass decreases the heat transfer coefficient but the suction of mass increases the heat transfer coefficient.
Solid-Phase Methane Fermentation of Solid Wastes
Authors: Ghosh S.
Published: November 2009

This paper presents the development of a novel solid-phase methane fermentation process involving acidic bioleachate production from an organic bed and biomethanation of the bed-liquefaction products in an external methane digester. Process operation with municipal solid waste showed that about 81 percent of the biodegradable volatile solids (VS) could be stabilized during three months of batch operation to afford a methane yield of 0.21 std m3 / kg VS added under ambient (∼25°C) conditions; this compares favorably with an ultimate mesophilic (35°C) methane yield of 0.26 std m3 / kg VS added.
An Approximate Procedure for Assessing the Effects of Mudslides on Offshore Pipelines
Authors: Summers P. B. , Nyman D. J.
Published: November 2009

The theoretical basis of an approximate procedure for assessing the effects of mudslides on buried marine pipelines is presented. The procedure has the capability to account for geometric nonlinearities (i.e., large-displacement “cablelike” behavior of the pipeline), nonlinear longitudinal soil restraint against pipeline pull-out, and a limited degree of nonlinear pipe material behavior. The analytical approach is based upon a variational work method known as the Theorem of Stationary Total Potential and is simpler and easier to employ than a nonlinear finite element code, while generally yielding good approximations to pipeline stresses and strains. The validity of the procedure is demonstrated for a typical mudslide situation through comparison with results of nonlinear finite element analyses.
Storm Quick-Disconnect Mooring System
Authors: Pease F. T. , Burns M. D. , Chen M.-C.
Published: November 2009

Severe storms such as hurricanes or typhoons can cause significant damage to offshore drilling rigs. Drillships, due to their high mobility, can flee severe storms after disconnecting from the mooring system. This paper presents a newly developed quick-connect/disconnect mooring system to permit the drilling rig to move off station quickly. The application of such a quick-connect/disconnect mooring system to the turret-moored drillship is presented.
The Parametrical Stress Analysis of Tubular T Joints
Authors: Chen T.-Y. , Chen B.-Z. , Wang Y.-Q.
Published: November 2009

The relationship between the geometric parameters of α, β, γ and τ of tubular T joints and chord stress concentration factor, SCF, has been investigated. With the use of calculated values as well as experimental data tables were compiled for a wide variety of cases when axial loading on the branch is applied. Finally, a probability analysis is given as to the reliability of using a particular SCF value.
Residual Strength of Dented Tubulars: Impact Energy Correlation
Authors: Richards D. M. , Andronicou A.
Published: November 2009

A procedure for the analysis of the damage of tubular members by denting and bending under lateral load is described. This leads to a relationship between impact energy and consequent damage. A large displacement, elasto-plastic analysis of dented tubular columns with imperfect straightness is introduced, which allows the effect of impact energy on member residual strength to be determined. Examples of damage reported from offshore structures are used to illustrate the analysis.
Flexural Strength and Fracture Toughness of Urea Model Ice
Authors: Timco G. W.
Published: November 2009

In many tests of ice-structure interactions performed using physical modeling techniques, the ice can fail in bending, flexure or by tensile cracking. Because of this, it is necessary to know and understand the flexural and fracture toughness properties of the model ice used in the test in order to be able to better interpret the results. In spite of this, to date there has been only a limited number of tests to measure the flexural behavior and the parameters influencing the flexural response of the model ice. The fracture toughness of model ice has not been measured. In this paper, the flexural behavior and fracture toughness of both freshwater ice and sea ice are reviewed in order to establish the prototype values and behavior which must be scaled for the model test. The results of a series of tests on the flexural properties of the model ice are presented and discussed in terms of the parameters which influence the strength including warmup time and temperature, test type (cantilever or simple beam), loading rate and loading direction. The fracture toughness of the model ice has been measured and the results are presented and compared to the prototype values for freshwater ice and sea ice. A comparison is made to assess the accuracy of the scalability of these properties of the ice.
Uniaxial Constitutive Equation of Ice From Beam Tests
Authors: Xirouchakis P. C. , Wierzbicki T.
Published: November 2009

A method is proposed to obtain ice uniaxial stress, strain, strain-rate relations from beam tests. The basic advantage of the proposed analytical technique is that it is a direct method of reducing beam test data. So, no assumption is made with regard to the ice constitutive behavior. The proposed method is an extension of Gillis and Kelly’s procedure to account for different ice response in tension and compression. It is also an extension of the procedure reported by Mayville and Finnie to account for ice response dependence on strain rate. Furthermore, it is shown that the expressions presented by Mayville and Finnie are only valid when the bending moment, with respect to the zero strain axis, is assumed independent of the centroidal extensional strain. A simple example of a linear elastic beam with a Young’s modulus that varies linearly with the beam depth is worked out to show that these earlier given expressions are not applicable in that case.
Reservoir Performance in Viscoelastic Porous Media
Authors: Rago F. M. , Ohkuma H. , Sepehrnoori K. , Thompson T. W.
Published: November 2009

The mass balance equations for a two-phase two-component fluid system are written for viscoelastic porous media. The resulting equations are approximated by finite differences and the resulting numerical simulator is used to conduct a sensitivity study on the effects of uniaxial viscoelastic deformation in geopressured aquifers. Results of this study indicate that viscoelastic deformation may have considerable influence on the pressure maintenance of these aquifers. A numerical model of the geopressured aquifer in Brazoria County, Texas, is constructed and the numerical simulator is used to predict the ultimate recovery of solution gas from this viscoelastic geopressured aquifer.
Wear Characteristics of Polycrystalline Diamond Compact Drill Bits in Small Diameter Rock Drilling
Authors: Hough C. L. , Das B.
Published: November 2009

The wear characteristics of polycrystalline diamond compact (PDC) drill bits were investigated in the context of drilling small holes in a hard abrasive medium. An efficient method for measuring wear of the PDC drill bits was developed. The wear test results were grouped or categorized in terms of rotary speed, feed and wear or failure characteristics. Contrary to the three classical wear phases (break-in, uniform wear and rapid breakdown) of the single material cutters, four distinctive wear phases were formed for the PDC cutters: I–break-in, II–diamond wear, III–carbide wear, and IV–rapid breakdown. The characteristics of the wear phases were identified and some suggestions were made to alleviate the wear problem.
Effect of Clearance on Rotary Rock Bit Journal Bearing Contact Stress
Authors: Marshek K. M. , Chen H. H.
Published: November 2009

This paper presents a numerical method for analyzing the effect of clearance on closely conforming rotary rock bit journal bearings. The modified Boussinesq point-force displacement influence function and the modified profile function are introduced in conjunction with the discretization of the integral equation. Automatic mesh generation is employed to redefine a new pressure area boundary and therefore round-off errors normally found while solving a large-scale linear system of equations can be avoided. The numerical method has been implemented in a computer program and has been applied to the problems of misaligned and perfectly aligned conformal contact. There is a close agreement with the Persson’s analytical solution at the center of the aligned bearing length. However, owing to a high stress concentration at the bearing edge, the edge pressure distribution will differ significantly from the Persson’s plane stress model. The conformal contact will have a comparatively higher peak pressure and lower contact-angle than the Hertzian line contact prediction. The results of the analysis provides a design tool for improving drill bit life.
A Shotcrete System Using a Robot
Authors: Cheng H. , Kahng C. H.
Published: November 2009

This paper describes the problems and solutions raised in an experimental approach for a shotcrete underground system design. The system consists of a retrofit dry-wet process dual purpose shotcrete machine and an industrial robot.
On the Collapse of Inelastic Thick-Walled Tubes Under External Pressure
Authors: Yeh M. K. , Kyriakides S.
Published: November 2009

The collapse of long thick-walled tubes under external pressure is studied both experimentally and analytically. A two-dimensional nonlinear formulation of the problem is presented. The formulation is general enough to include initial geometric imperfections of the tube cross section such as initial ovality and wall thickness variation. In addition the effects of residual stresses and of initial inelastic anisotropy are considered. Experiments on tubes with D/t values between 10 and 40 were carried out. Good agreement between experiments and theory is shown to occur provided all parameters are modeled correctly. A study of the effect of the various parameters of the problem on the collapse pressure is also presented.
A Computational Model for Drilled Cutting Transport in Air (or Gas) Drilling Operations
Authors: Sharma M. P. , Chowdhry D. V.
Published: November 2009

The hydrodynamics of isothermal, one-dimensional gas-solids suspension is theoretically analyzed. A computational model is developed. The model is applied in predicting the pressure drop distribution in air-sandstone mixture flows through a vertical annular space (simulating the flow stream between a bore hole and a drill pipe). The model can be applied to any isothermal, one-dimensional flow of gas-solid suspension. The numerical results are in satisfactory agreement with the experimental data collected from studies done on drilled cutting carrying capacity of air in air-drilling operations.
An Approximate Rock Stress Field for Steady Flow Into Production Casing
Authors: Fahrenthold E. P. , Cheatham J. B.
Published: November 2009

An uncoupled poroelasticity analysis of steady flow into a fixed cylindrical cavity in a porous medium gives an approximate solution for the stress field around a production casing. As compared to the open well bore case, the order of the principal stresses is inverted and larger values of the well pressure drawdown are required to initiate yielding of the porous rock. The solution quantifies the maximum formation support available from a production liner.
Fractured Well Responses in Heterogeneous Systems—Application to Devonian Shale and Austin Chalk Reservoirs
Authors: Yeh N. S. , Davison M. J. , Raghavan R.
Published: November 2009

This paper presents new methods to analyze fractured well responses in heterogeneous reservoirs. We consider wells producing formations that are naturally fractured and use the idealizations proposed by Warren and Root (pseudosteady-state flow in the matrix-system) and by deSwaan-O (unsteady-state flow in the matrix-system) to model the naturally fractured reservoir. Pressure responses are correlated in a manner suitable for direct application of field data. Methods to determine fracture half-length are presented. Two field applications are discussed. The consequences of neglecting the heterogeneous character of the porous medium are also discussed.
Analysis of the Channeling Effect in Variable Porosity Media
Authors: Vafai K.
Published: November 2009

A theoretical solution of the channeling effect is presented. The details of the channeling production are investigated in detail and an approximate method for obtaining the temperature distribution is presented. These results complete a theoretical solution of the channeling effect which has a number of different applications in energy-related problems, such as fixed-bed catalytic reactors, metal processing, underground coal gasification, oil shale, chemical-reaction engineering, drying and packed-bed heat exchangers. These differential permeability problems are also encountered in several energy resource extraction applications related to underground coal conversion, vertical modified in-situ (VSIS) oil shale retortion, steam flooding and oil recovery from tar sands. The method of matched asymptotic expansions is used to obtain the theoretical solution. The effects of using the singular perturbation solution in obtaining the temperature distribution are discussed. The existence and the concept of the triple momentum boundary layer in variable porosity media is analyzed in detail. The theoretical results are found to be in good agreement with the numerical and the available experimental results.
A Uniaxial Nonlinear Viscoelastic Constitutive Relation for Ice
Authors: Harper B. D.
Published: November 2009

The present paper concerns the description of uniaxial deformation and failure of ice in uniaxial compression in terms of a nonlinear viscoelastic constitutive theory. The constitutive model incorporates explicit dependence upon micro-structural defect growth and assumes the form of a so-called modified superposition integral contaiing a linear kernel which depends only upon time. This last feature will greatly simplify the task of experimentally characterizing the various material properties which appear in the theory. The existence of correspondence principles for the model will also facilitate the solution of practical boundary value problems. Predictions based upon this model will be shown to agree qualitatively with experimental results for creep (constant stress) and strength (constant strain-rate) tests on ice. In addition, specific empirically deduced relationships between stress, strain, strain-rate and time at certain critical points in these standard tests will be shown to result directly from the constitutive theory as special cases.
Some Latest Developments in Icebreaker Technology
Authors: Schwarz J.
Published: November 2009

Icebreaking technology has been improved over the last 10–15 yr so that the installed power of icebreaking ships could be drastically reduced. The improvement is demonstrated on four examples of icebreaking ships, one conventional and three advanced concepts, which have shown their icebreaking ability already in full scale. The icebreaking capability of ships is suggested to be evaluated through model tests, theoretical approach and by full-scale measurements. The evaluation should be carried out for various ice conditions by resistance and self-propulsion tests. Finally, some thoughts are presented on features of an advanced icebreaker.
Experimental Free Convection From Piping in District Heating Utilidors
Authors: Stewart W. E. , Verhulst J. L.
Published: November 2009

Experiments were performed to study the two-dimensional natural convection heat transfer from two heated isothermal horizontal cylinders to an isothermal-cooled rectangular enclosure. The experiments were designed to simulate the heat transfer encountered in underground heat distribution systems where steam and condensate lines are routed through underground or in-ground corridors (utilidors) from a central plant. The steam supply and condensate return lines were simulated with two copper cylinders. The fluid between the cylinders and enclosure was distilled water to simulate the Rayleigh number range encountered with air in actual utilidors. Results were obtained for the overall heat transfer coefficient between the two cylinders and the enclosure. The data was correlated over a Rayleigh number, RaL, range of 2.1 × 108 to 4.8 × 109 representative of the Rayleigh number, based upon a hypothetical gap width, in a typical utilidor exposed to extreme enclosure to piping temperature differential boundary conditions. The corresponding Nusselt numbers, NuL, ranged from 21 to 59 when both cylinders were heated for water as the intermediate fluid. Corresponding heat transfer coefficients calculated for the utilidor case with air as the intermediate fluid were found to be smaller compared to some other correlations for concentric cylinders.
Nonradiative Heat Transfer Coefficients and “Cold” Operating Experience With a Laboratory SCFBC Model
Authors: Umez-Eronini E. I. , Cannon J. N.
Published: November 2009

A cold test model study of the staged cascade fluidized bed coal combustion process is described. Proper cascade flow of solids through the system was found to be sensitive to bed and downcomer distributor plate pressure drops. Control of bed depth by weir level was also complicated at high fluidization velocities by the process of entrained particles falling back into the downcomer. Bed to tube heat transfer coefficients ranging from 142 to 256W/m2•K were measured at the top surface of a simulated boiler tube in shallow beds, 0.15 to 0.23m deep.
Two-Phase Flow in Piping Components
Authors: Sookprasong P. , Brill J. P. , Schmidt Z.
Published: November 2009

Two-phase and single-phase pressure drop data were obtained for flow in horizontal 5.08-cm-dia pipe and piping components that included: a 9.14-m straight section of pipe; a gate valve; an elbow; a combination of elbow and gate valve separated by different pipe lengths; a globe valve; a swing check valve; and a union. Single-phase pressure drops produced by each component were used to establish the resistance coefficient, K. This resistance was then used to calculate two-phase pressure drops for each component using the Tremblay and Andrews homogeneous flow model. An acceptable agreement was found between measured and predicted pressure drops for all piping components studied. Pressure recovery lengths for individual components were found to be 10–50 pipe diameters, depending on flow rates. The resistance coefficient of two components separated by a distance less than the recovery length was always greater than the summation of each individual resistance coefficient.
Collapse of Imperfect Tubulars
Authors: Pattillo P. D. , Huang N. C.
Published: November 2009

The nonlinear response and eventual collapse of a cylinder loaded by resultant external pressure and axial load is analyzed. The cross-sectional description of the cylinder is sufficiently general to include ovality, eccentricity, and local thickness anomalies. Applications of the model include the prediction of minimum collapse resistance of commercial tubulars.
Laboratory Investigation of Bit Bearing Temperatures in Rotary Drilling
Authors: Karfakis M. G. , Heins R. W.
Published: November 2009

One mechanism of bit failure in geothermal drilling is thought to be directly related to the overheating of the bearings. High temperatures alter the microstructure of the bearing material and reduce its wear resistance. This paper presents a laboratory study on bit bearing temperatures in rotary drilling using a two-roller cone micro-bit drill rig and a statistical approach referred as response surface methodology. The effects of the drilling variables on bearing temperatures were investigated. The range of bearing temperatures for the test conditions under study was determined. A second-order bearing temperature predicting equation is presented.
A Study of Rock-Bit Interaction and Wellbore Deviation
Authors: Ma D. , Azar J. J.
Published: November 2009

An overall analysis of wellbore deviation is presented. A theoretical study in side-cutting mechanism and side-cutting ability of roller cone bits is described. A full-scale drilling rig and a specifically designed cradle system for measuring rock-bit interaction forces are used to perform the experimental portion of this paper.
Outward Melting in a Cylindrical Annulus
Authors: Ho C. J. , Lin K. C.
Published: November 2009

A two-dimensional numerical simulation of outward melting process of a phase change material, n-octadecane, contained in a horizontal cylindrical annulus has been performed with a finite-difference solution of the governing partial differential equations of the system. Both conduction in the unmelted solid and natural convection induced in the melt have been taken into account. Results have been obtained for Rayleigh numbers up to Ra = 2.4 × 105 and the radius ratio of the annulus in a range of 1.6–3.0. The simulations are examined in the light of the effects of both the natural convection in the melt region and/or the subcooling in the solid region on the time-variation of the melting front during the process.
Experiments on an Electromagnetic Capsule Pump
Authors: Assadollahbaik M. , Liu H. , Hoft R. G.
Published: November 2009

A simple electromagnetic pump, based on the principle of linear induction motor (LIM), has been developed by researchers at the University of Missouri-Columbia for use in hydraulic capsule pipelines (HCP). The paper presents experimental data intended to substantiate a preliminary theory on the pump. The experiments were conducted using a LIM around a 114-mm-dia pipe. The pump and motor efficiencies, pump head, etc., were tested and compared with predictions based on the preliminary theory. The maximum discrepancy between theory and experiments was within 30 percent. The study shows that the behavior of the LIM pump for HCP can be predicted approximately from the preliminary theory. More study is needed to improve the accuracy of the theory.
Scale-up Technique of Slurry Pipelines—Part 2: Numerical Integration
Authors: Roco M. C. , Mahadevan S.
Published: November 2009

A kinetic energy turbulence model has been proposed for the computer flow simulation and scale-up of slurry pipelines (in Part 1 [1]). The numerical integration is performed by using a modified finite volume technique, with application to high-convective two-phase flows in two and three dimensions (in Part 2). The mixture kinetic energy and eddy viscosity turbulence models are compared. The one-equation eddy-viscosity turbulence model (εt - model) is formulated in Part 2 and applied for the multi-species particle slurry flow in cylindrical pipes. A modified finite volume technique is proposed for high convective transport equations, for one and two-phase flows. The integral formulation per volume yields surface and volume integrals, that are stored and counted only by interfaces using a multidimensional approach. The nonlinear distributions in volumes and on interfaces are approximated employing the derivatives in the normal and tangent directions to the bounding surfaces. Linear, analytical (upwind) and logarithmic laws of interpolations are considered for internal flows. The numerical approach was tested with good results for transport equations of momentum and various contaminants (solid particles, temperature, eddy-viscosity) in pipes. Experimental data for one and two-phase flows are compared to the integral finite volume predictions. The proposed finite volume technique can economically simulate complex flow situations encountered in the slurry pipeline scale-up applications.
Dynamic Coupled Fluid-Structure Interaction Analysis of Flexible Floating Platforms
Authors: Babu P. V. Thangam , Reddy D. V.
Published: November 2009

The paper presents the dynamic response analysis of a flexible floating platform subjected to water transmitted, amplified earthquake accelerations input at its base. The finite element method is used for formulating the unsymmetric, coupled dynamic equations of equilibrium of the fluid-structure continuum. The boundary conditions include the free surface wave and radiation damping. The amplification of the earthquake through the water medium is studied using a linear system of lumped masses, springs, and dashpots. A new procedure is demonstrated to solve the coupled, unsymmetric equations using a specially developed computer program FLUSIN. Depending on the water depth, it is estimated that the vertical accelerations transmitted to the bottom of the floating structure may be amplified considerably. Cavitation is a possibility for greater depths and higher accelerations. Two numerical illustrations are presented—a floating nuclear plant and a liquid petroleum gas storage facility subjected to amplitude earthquake accelerations. The results compare well with those obtained by other investigators using approximate techniques. The procedure can be applied to floating exploration/production-storage/transportation platforms and pipelaying barges subjected to water transmitted earthquake forces. The formulation is easily adaptable to any fluid-structure system as well as for other kinds of dynamic excitation. With the increased focusing of attention to compliant-type tension-legged platforms and semisubmersibles for production/drilling and LPG storage platforms, the project is of considerable significance. The work is a forerunner for much needed experimental investigation, particularly with respect to cavitation. Also, the findings would have considerable spin-off effects to OTEC concepts.
The Effect of Back Rake Angle on the Performance of Small-Diameter Polycrystalline Diamond Rock Bits: ANOVA Tests
Authors: Hough C. L.
Published: November 2009

The effect of back rake angle on a center vacuum bit design was investigated through factorial Analysis of Variance (ANOVA) tests for drilling in shale. Multiple performance criteria: penetration rate, specific energy and torque were used in these tests. Thrust and rotary speed were the controlled variables. Results from ANOVA tests showed that rake angle has a significant effect on penetration rate and torque but not on specific energy. Further tests of means revealed that the 20-deg bit gave the maximum penetration rate although there was no statistical difference among the 15, 20 and 25-deg angles. Tests of means also revealed that the 7-deg bit gives the minimum torque, but is statistically the same as the 15 and 25-deg bits. The results of the test will be useful for design and selection of small-diameter bits for drilling in shale and sand formations.
The Combustion of Lean Mixtures of Methane and Air—A Kinetic Investigation
Authors: Hanna M. , Karim G. A.
Published: November 2009

The combustion of lean mixtures of methane, representing natural gas, in air is examined analytically employing a detailed chemical kinetic scheme involving 14 species and made up of 32 reaction steps that proceed simultaneously. The changes with time in the concentrations of the major relevant reactive species are determined throughout, right from the commencement of the preignition reactions to the time of achieving near equilibrium conditions. The results of such an approach to the combustion process are considered over a wide range of temperature (1200 K–2200 K) and equivalence ratios (from 0.20 to the stoichiometric value). Information is then presented in relation to some important combustion parameters that included the ignition delay, overall reaction rates and the times needed for completing the combustion process. Some guidelines are suggested for effecting eventually improved energy utilization and reduced environmental pollution from combustion processes involving lean mixtures of methane and air.
An Investigation of the Volatilization of Oil Sand Surfaces When Subjected to Parallel Hot Gaseous Streams
Authors: Abdrabboh M. , Karim G. A.
Published: November 2009

Preshaped rectangular sand slabs were subjected to hot oxidizing streams. The rate of mass loss due to fluid volatilization at constant stream temperature was established and correlated with time by a simple analytical expression that fitted the experimental data well. The correlation parameters showed that the ultimate extent of volatilization depends uniquely on the surrounding stream temperature. The time rate of mass loss was found to be a function of Reynolds and Schmidt numbers and the temperature of the heating stream.
Flash-Butt Welding of Large-Diameter Oil and Gas Pipelines
Authors: Turner D. L.
Published: November 2009

Interest in developing a high-production automatic joining method for quality offshore pipelines led to full-scale evaluation of the flash-butt welding process. During the past five years, two separate flash-butt welding machines have been used to provide over 1100 welds in 914-mm (36-in.) o.d. pipe for test and evaluation. Increased speed and the quality inherent in a fully automatic welding process were the two major incentives for the development project. It is estimated that flash-butt welding can produce up to 377 joints per day in 914-mm (36-in.) o.d. × 25-mm wall thickness pipe—twice what can be produced by conventional manual (shielded metal arc) welding techniques. This paper describes the flash-butt welding process and plans to install production equipment aboard a semi-submersible laybarge in the near future.
Computer Modeling of Fixed Bed Underground Coal Gasification Using the Permeation Method
Authors: Abdel-Hadi Eed A. A. , Hsu T. R.
Published: November 2009

A two-dimensional computational model has been developed as a pilot study for the multidimensional simulation of fixed bed underground coal gasification (UCG). The analysis is based on the finite element method and incorporates a moving boundary algorithm to model the permeation linked vertical well in a forward gasification mode. In order to account for the motion of the combustion front with time, an immobilization transformation of coordinates technique is introduced in the finite element formulation. A numerical case study is included to illustrate the capability of the model. Predictions on temperatures, gas composition, pressure, and coal consumption in space and time are possible by using this model.
Non-Newtonian Fluid Flow in a Reservoir—An Application to Hydraulic Fracturing
Authors: Torok J. S. , Advani S. H.
Published: November 2009

A formulation for the flow of a power law non-Newtonian fluid in a porous-permeable medium represented by a nonlinear partial differential equation is presented. This governing equation is transformed into a nonlinear ordinary differential equation whose solution is expanded as a Lie series. As an application to hydraulic fracturing, the problem of a Newtonian reservoir fluid being displaced by an injected non-Newtonian fluid is discussed. The resulting moving boundary problem is solved, resulting in explicit solutions for the respective pressure distributions and the displacement of the moving interface. The presented solutions provide a firm theoretical basis for fluid loss characterization in the porous-permeable reservoir.
Operating Experience With a Fluidized Bed Test Combustor
Authors: Hainley D. C. , Haji-Sulaiman M. Z. , Yavuzkurt S. , Scaroni A. W.
Published: November 2009

This paper presents operating experience with a fluidized bed combustor burning various coals. The primary focus is on the effect of relevant coal properties on combustor performance. Tests were carried out using anthracite, HVB and HVC bituminous and sub-bituminous A coals, and petroleum coke. Comparisons of the performance of the combustion on the various fuels are made. A two-stage fluidized bed combustor operating in a single-stage mode without recycle was employed. Experimental measurements included temperature, fuel feed rate, fluidization velocity and bed height. For some of the coals, bed agglomeration was found to occur. The results indicate that coal properties have an important effect upon the operation of the fluidized bed combustor.
An Examination of the Interaction Between Oil Sand Fragments in Hot Gaseous Streams
Authors: Abdrabboh M. A. , Karim G. A.
Published: November 2009

Clusters of preshaped oil sand spherical fragments were subjected to hot steady streams of air at low Reynolds number and constant stream temperature. A wide range of different combinations and arrangements of these fragments were employed involving up to twenty identical spherical samples that were either piled or set normal to the free stream of air and left exposed for various prescribed time periods at constant stream temperatures. The rates of mass loss due to fluid volatilization off these clusters during this exposure were then established experimentally and compared with the corresponding rates derived from the behavior of single spheres. This comparison showed, for the cases considered in this investigation, essentially no significant effect due to the interaction of the spherical samples with each other. The behavior of a single fragment can then form the basis for establishing the volatilization rate of the cluster. However, it was shown that the confinement of these clusters of fragments within a cylindrical tube placed axially along the heating stream produced appreciable effects on the rates of volatilization. The extent of the deviation from the single fragment model observed was then examined and a number of variables affecting it identified.
Theoretical Thermal Evaluation of Energy Recovery Incinerators—Part II: Parametric Examination
Authors: Kodres C. A.
Published: November 2009

The thermal characteristics of energy recovery incinerators are examined, both parametrically and, to the extent possible, by direct comparison. A mathematic model is employed, using a computer program to solve the governing equations. Three energy recovery configurations are considered: a water tube heat exchanger downstream from the combustion chambers, waterwalls, and a combination of the two. Results show the advantages of combining water walls and a convection boiler.
Spherical Phase-Change Energy Storage With Constant Temperature Heat Injection
Authors: Kumar A. , Prasad A. , Upadhaya S. N.
Published: November 2009

Storage of thermal energy due to latent heat involved during outward radial melting of a phase-change material contained in a spherical shell is solved using variational, integral and quasi-steady methods. At uniform temperature heat is applied to inner surface. These methods provide closed-form solutions in the Stefan number, an independent parameter. The results for total energy storage, the phase-change depth and their rate obtained from these approximate analyses do not vary significantly.
Transient Natural Convection on a Vertical Flat Plate Embedded in a High-Porosity Medium
Authors: Chen C.-K. , Hung C.-I. , Horng H.-C.
Published: November 2009

This paper provides an analysis of the non-Darcian effect on transient natural convection of a vertical flat plate embedded in a high-porosity medium. The plate surface is either maintained at an uniform wall temperature (UWT), or subjected to an uniform heat flux (UHF), and convective, boundary and inertia effects are considered. The local volume-averaged principles and certain empirical relations have been utilized to establish the governing equations. The coupled nonlinear partial differential equations are solved with a numerical integration technique using a cubic spline. Along with transient mean and local Nusselt numbers at the plate, representative transient velocity and temperature profiles are presented. Both effects for non-Darcian flow model are shown to be more pronounced in high-porosity medium and, hence, reduce the heat transfer rate.