bluuebunny/crossref_metadata_2025 huggingface dataset:
Geotechnical and Geological Factors Affecting Offshore Engineering and Seabed Utilization on a Carbonate Margin: St. Croix, V.I.
Authors: Bennett R. H. , Bowles F. A. , Lambert D. N. , Nastav F. L. , Merrill G. F. , Almagor G. , Burton W. J.
Published: November 2009

The northern margin of St. Croix, V.I. is characterized by three morphological features: a narrow shallow water carbonate shelf; a steep slope; and a deep-sea basin. Shallow water reef material and carbonate debris occurs along the shelf. A thin carbonate ooze overlies the steep slope where occasionally rock outcrops occur. Trough sediments are clayey silts and turbidite deposits. Average shear strengths range between 3.1–10.0 kPa for the slope and 5.8–28.3 kPa for the trough (1-m cores). Values range as high as 69.1 kPa at sediment depths greater than one meter. Average sensitivities range between 3.2–6.1 for the slope and 4.1–12.1 for the trough (upper 1 m). Higher sensitivities [8–12] indicate the presence of metastable deposits and considerable strength loss upon disturbance. Variation in the sand, silt, and clay sized fractions, the nature of the carbonate particles, and bioturbation strongly affect the variability in the geotechnical properties. Quantitative studies of local morphology, processes and sediment properties reveal the need for detailed data in specific areas of engineering interest.
Investigation of API 8 Round Casing Connection Performance—Part I: Introduction and Method of Analysis
Authors: Asbill W. T. , Pattillo P. D. , Rogers W. M.
Published: November 2009

The purpose of this investigation was to gain a better understanding into the mechanical behavior of the API 8 Round casing connection, when subjected to service loads of assembly interference, tension and internal pressure. The connection must provide both structural and sealing functions and these functions were evaluated by several methods. Part I discusses the methods of analysis, which include hand calculations using strength of materials, finite element method via unthreaded and threaded models, and experimental analysis using strain gages. Comparisons of all three methods are made for stresses and show that the finite element method accurately models connection behavior.
Investigation of the Alexander L. Kielland Failure—Metallurgical and Fracture Analysis
Authors: Almar-Naess A. , Haagensen P. J. , Lian B. , Moan T. , Simonsen T.
Published: November 2009

On March 27, 1980, the semi-submersible platform Alexander L. Kielland broke down in a storm in the North sea, resulting in a loss of 123 lives. The investigation subsequently performed by the inquiry commission showed that one of the lower tubular bracings had failed by fatigue. As a result, the vertical leg attached to it was torn off, and the platform capsized. The fatigue fracture had started from a double fillet weld joining a 0.325-m tubular attachment to the bracing. The fillet welds were partially cracked in the early history of the platform due to lammelar tearing. Cumulative damage calculations indicated that the design fatigue life of the bracing was inadequate.
Ocean and Arctic Engineering: Risk and the Economic, Social, Legal Context
Authors: Wenk E.
Published: November 2009

Ocean and arctic engineers typically play three roles. Through research, they contribute new understandings of basic scientific principles applied in a strenuous and hostile environment. Through design, they apply that knowledge to such crucial functions as construction, transportation, communication, extraction of natural resources, and environmental conservancy. Through serving as a systems analyst or administrator, they are concerned with both the industrial management of marine technology and with its social management. In this latter concept, ocean and arctic engineers bond their technical talents with deeper perceptions of their client’s dilemmas in a concern for ends as well as means. This exercise is the least familiar to the engineering professional, yet it entails the most trenchant contribution that engineers make to human affairs and thus the noblest expression of social responsibility. This paper traces the connections of ocean and arctic engineering to their broadest context—the economic, social, legal, cultural and political ramifications that increasingly season intrinsic elements of research, design and application. With a series of historical and anecdotal vignettes, this theme is elaborated to dramatize the sharp changes that have accompanied the interaction of technology and society generally in the last four decades. Moving from examples of the excitment of personal enlightment through discovery to the satisfaction of successful operating performance, this review concludes with four evolving challenges: updating tools of practice to incorporate notions of risk assessment and social impact; major reforms in engineering education to emphasize breadth instead of specialization; active engagement in technology-policy analysis to facilitate citizen enlightenment and foresight; and recognition that engineering ethics must parallel technical proficiency and virtuosity in carrying to the future the unique torch of noblesse oblige.
The Stress Analysis and Experimental Research of Tubular Joints of Offshore Drilling Platform
Authors: Chen T. Y. , Chen B. Z. , Wang Y. Q.
Published: November 2009

An analytical method for the stress analysis of tubular joints of T, Y, K type is presented in this paper. The stress distribution and stress concentration factor of the joints are calculated. Numerical results are in good agreement with the experimental results.
Shear Fracture Arrestability of Controlled Rolled Steel X70 Line Pipe by Full-Scale Burst Test
Authors: Sugie E. , Kaji H. , Taira T. , Ohashi M. , Sumitomo Y.
Published: November 2009

The High Strength Line Pipe Research Committee organized by the Iron and Steel Institute of Japan has conducted five full-scale burst tests on line pipe of 48 in. o.d. × 0.720 in. w.t. (wall thickness) and grade X70 under pressure of 80 percent SMYS with air: 1) to study the influence of separation on the arrestability of shear fracture, and 2) to obtain the material criterion for arresting the propagating shear fracture. Test pipes of Charpy V notch energy from 80 to 290J with different amount of separation, were produced from both controlled rolled steels and quenched and tempered steels. These research projects clarified that the separation of material itself did not influence the crack propagation behavior and its arrestability. Furthermore, the material criterion for arresting the shear fracture was analyzed by the pressure-velocity relationship counterbalancing the crack velocity curve and gas decompression curve.
The Influence of Boundary Layer Velocity Gradients and Bed Proximity on Vortex Shedding From Free Spanning Pipelines
Authors: Grass A. J. , Raven P. W. J. , Stuart R. J. , Bray J. A.
Published: November 2009

The paper summarizes the results of a laboratory study of the separate and combined effects of bed proximity and large velocity gradients on the frequency of vortex shedding from pipeline spans immersed in the thick boundary layers of tidal currents. This investigation forms part of a wider project concerned with the assessment of span stability. The measurements show that in the case of both sheared and uniform approach flows, with and without velocity gradients, respectively, the Strouhal number defining the vortex shedding frequency progressively increases as the gap between the pipe base and the bed is reduced below two pipe diameters. The maximum increase in vortex shedding Strouhal number, recorded close to the bed in an approach flow with large velocity gradients, was of the order of 25 percent.
Stability Considerations for Existing Conventional Autopilots on Modern Ship Types
Authors: Reid R. E. , Griffin D. E.
Published: November 2009

The directional stability of three modern ship types with conventional nonadaptive autopilots is examined. It is shown that while attempting to improve the course-keeping ability of these ships, the potential exists for the operator to unknowingly cause a loss of directional stability with the controls available to him. Stable controller settings are established to prevent such an occurrence. The results of a design method allowing optimization of the autopilot to achieve a desired degree of stability controllability versus steering-induced added resistance is also presented.
On the Optimization of Ship Motion in Heavy Ice Conditions
Authors: Nawwar A. M.
Published: November 2009

For a given ship, its speed in ice decreases as ice conditions become more severe until it can no longer move continuously. The transition speed concept provides a valid cut-off point below which a ship has to switch to the discontinuous or ramming mode of operation. Solutions for the continuous and ramming mode ship motions and an analysis of a typical ramming cycle are presented. A general solution valid for all stages of ramming is given. It provides a closed form equation which can be used both to study the influence of ship characteristics and operational tactics upon ship performance and to optimize ship motion in heavy ice conditions decreasing fuel consumption and transit time.
Subharmonic and Chaotic Motions of Compliant Offshore Structures and Articulated Mooring Towers
Authors: Thompson J. M. T. , Bokaian A. R. , Ghaffari R.
Published: November 2009

Compliant offshore structures have complex nonlinear dynamics. Subharmonic resonances can co-exist with small fundamental motions. To prevent a simulation missing an entire subharmonic peak, a comprehensive set of initial conditions must be explored. Chaotic nonperiodic motions can also arise in deterministic problems. These are extremely sensitive to starting conditions and require a statistical description. Chaotic responses and their adjacent subharmonics of arbitrarily high order mean that the duration of digital, analogue and laboratory simulations must be chosen with considerable care. Resonances of articulated mooring towers, encountered in tank tests, are used to illustrate these general concepts.
Vortex Shedding Induced Dynamic Response of Marine Risers
Authors: Rajabi F. , Zedan M. F. , Mangiavacchi A.
Published: November 2009

An analytical model to predict the dynamic response of a riser in regular waves or in current to vortex shedding-induced lift forces is described. The riser is treated as a continuous beam under tension. A modal superposition scheme is used to solve the linearized equation of motion in the frequency domain. The excitation lift force is represented by a harmonic function with a frequency equal to the dominant vortex shedding frequency. Empirical correlations are used to determine the lift coefficients and shedding frequencies along the riser. Lift amplification is considered at or near the “lock-in” conditions. The fluid resistance to riser oscillations is represented by a Morison’s equation-type expression.
Improved Modeling of Tubular Brace Elements Under Severe Cyclic Loading
Authors: Powell G. H. , Row D. G. , Hollings J. P.
Published: November 2009

Theory and examples are presented for a new structural element suitable for modeling tubular steel braces in offshore platforms. Yielding, buckling and post-buckling strength losses are considered using a simplified, yet essentially rational, theory.
The Nonlinear Dynamics of Long, Slender Cylinders
Authors: Kim Y. C. , Triantafyllou M. S.
Published: November 2009

The nonlinear dynamics of long, slender cylinders for moderately large deformations are studied by projecting the solution along the set of eigenmodes of the linear problem. The resulting set of nonlinear ordinary differential equations is truncated on the basis of bandlimited response. The efficiency of the method is due to the derivation of asymptotic solutions for the linear problem in its general form, by using the WKB method. Applications for the dynamics of risers, including the effects of nonlinear fluid drag and geometric nonlinearity demonstrate the features of the method.
Performance of Drill String Hardfacings
Authors: Williamson J. S. , Bolton J.
Published: November 2009

Drill string hardfacings are composites of steel and tungsten carbide applied by welding techniques. This paper discusses the important variables involved and gives experimental results for casing wear and abrasive wear resistance.
Cavitating and Structured Jets for Mechanical Bits to Increase Drilling Rate—Part I: Theory and Concepts
Authors: Johnson V. E. , Chahine G. L. , Lindenmuth W. T. , Conn A. F. , Frederick G. S. , Giacchino G. J.
Published: November 2009

The erosion and cleaning effect of jets is enhanced when the degree of cavitation on or near the bottom of the hole is increased. Analyses indicate that self-excited, acoustically resonating nozzles, causing jets to be structured with large discrete vortex rings, should promote cavitation to depths several times greater than for conventional jets. The new nozzle designs are shown to be suitable for existing mechanical drill bits and may even effect hole cleaning in the absence of cavitation.
Stresses in a Submarine Topography Under Ocean Waves
Authors: Mei C. C. , McTigue D. F.
Published: November 2009

The problem of submarine slope stability is of interest to both offshore engineering and geology. In an uneven topography, the weight above a horizontal plane induces two-dimensional variation in the static stress field. The action of wave pressure, which changes with depth, further introduces excess pore pressure and dynamic stresses in the sea bottom. In the present paper, we combine a simple analytical theory for the static stress by the present authors, and the recent solution by Mei and Foda (6) for wave-induced stresses in a plane poro-elastic sea bed to account for mild bottom slope and wave shoaling, and obtain the effective stress field in a submarine topography under sea waves. Sample results are given for a ridge and a canyon. In particular, the dynamic pore pressure and the combined static and dynamic effective stresses are presented.
Evaluation of Seismic Behavior of a Braced Tubular Steel Structure by Pseudodynamic Testing
Authors: Shing P. B. , Javadian-Gilani A. S. , Mahin S. A.
Published: November 2009

The inelastic seismic behavior of an X-braced, tubular steel frame is studied experimentally by means of pseudodynamic testing. The pseudodynamic method, which utilizes a numerical algorithm in the on-line computer control of a test specimen, can realistically simulate the seismic response of a structural model. This paper presents a brief outline of the experimental procedure and the results of the tubular frame tests, including the global responses, the inelastic energy-dissipation capabilities, and the failure mechanism of the frame at various excitation levels. Correlation of these results with previous experimental studies illustrates the feasibility and accuracy of the new test method.
A Review of Hydraulic Fracture Modeling—Part I: General Concepts, 2D Models, Motivation for 3D Modeling
Authors: Mendelsohn D. A.
Published: November 2009

This is Part I of a two-part paper which reviews in depth the literature on the modeling of the propagation of large hydraulic fractures in underground rock formations. Part I presents a general formulation of the problem, its geometry and only the most fundamental and unrestrictive physical assumptions. The two basic two-dimensional models of constant height (rectangular) fractures which formed the core of modeling efforts from 1960 through the late 1970’s are discussed in detail followed by a brief review of the effects of fluid diffusion in the fractured medium on crack propagation. The recent field and laboratory observations which have shown that nonrectangular fractures can occur quite often are discussed, as are their impact on the modeling effort, specifically the need for three-dimensional models of crack propagation in layered environments. Part II of the paper deals with the three-dimensional modeling efforts and some fundamental crack and fracture mechanics problems related to the vertical growth of a hydraulic fracture.
Pyrolysis of Municipal Solid Waste in Japan
Authors: Igarashi M. , Hayafune Y. , Sugamiya R. , Nakagawa Y. , Makishima K.
Published: November 2009

Funabashi City’s Municipal Solid Waste Pyrolysis Plant is the first full-scale plant having a dual fluidized bed gasification system. The plant has the capacity of processing 4.5 × 105 kg/day of mixed municipal solid waste with a very limited emission of air, water and land pollutants. The energy is recovered as high calorific value fuel gas. Since April 1983, the plant has been in continuous operation. The purpose of this paper is to report on the system and the experience obtained during the 5 mo in which it was in operation. Data on the material balance of the pyrolysis, the analysis regarding the gas produced, the flue gas composition and the equipment used are included.
A Method to Optimize Steering Performance of Conventional Ship Autopilots
Authors: Griffin D. E. , Reid R. E.
Published: November 2009

A method allowing a priori optimization of fixed structure steering controllers is presented. The technique is based on the second method of Lyapunov, and allows optimization of the controller parameter values to a predefined quadratic index of steering quality. The design methodology involved is applied to different controller structures using a 250,000-dwt tanker as an example. The resulting performance is compared to that achievable for a standard setting conventional autopilot on the same ship, using frequency domain analyses. The results presented suggest that the method has the potential to result in improved steering performance.
Field Measurement of Platform Behavior, Comparison With Design, and Long-Term Monitoring of Responses Stability After Three Years of Service
Authors: Ansquer P. F. , Antalovsky S. A. , Hjelde E. , Agnello G.
Published: November 2009

Field data from structural, geotechnical and wave measurements made on the concrete gravity platform TCP2 of the Norwegian FRIGG field are disclosed in this paper. Data recorded during 3 yr are interpreted and compared to design values. The stability of invariant parameters has been followed and demonstrated in view of monitoring the long-term behavior stability of the platform. The measured behavior differs from the design behavior and exhibits that design assumptions were conservative. Particularly during this 3-yr period the platform experienced very severe storms with waves up to 25.7 m, a value close to the maximum design wave (100-yr wave: 29 m). It is shown from field data how a bridge connection to a neighboring platform may influence the actual behavior compared to the design one and must be taken into account to understand the measured behavior. It is finally shown that supposed invariant parameters like natural frequencies and others are stable on a long-term basis, and how these invariants are intended to be used for the long-term stability monitoring.
Interaction of Waves With a Moored Semisubmersible
Authors: Chakrabarti S. K. , Cotter D. C.
Published: November 2009

A semisubmersible moored in waves experiences a steady offset and two types of motion—a first-order motion at frequencies corresponding to the incident wave frequencies and a slowly oscillating motion near the natural frequency of the semisubmersible/mooring system. An extensive wave tank testing of a semisubmersible model was undertaken in which the motions of the semisubmersible and the loads in the mooring lines were measured. The semisubmersible was tested in the tank in a head sea as well as a beam sea heading in a series of regular waves, regular wave groups and irregular waves. The test results of the steady offset and first-order and slowly oscillating motions are presented for each heading and for each of these wave series as functions of the wave period. The experimental results are correlated with theoretical results based on a 3-D diffraction theory which takes into account the appropriate first and second-order terms. It is found that the nonlinear damping terms are quite important in explaining the behavior of the moored semisubmersible in waves and that the steady drift loads in wave groups can be determined from results based on regular waves.
Response of a Simple Tension Leg Platform Model to Wave Forces Calculated at Displaced Position
Authors: Spanos P. D. , Agarwal V. K.
Published: November 2009

A simple single-degree-of-freedom model of a tension leg platform is used to assess the reliability of the common practice of calculating wave-induced forces at the undisplaced position of offshore structures. This assessment is conducted in conjunction with the Morison equation based modeling of the wave-induced forces on slender structural members. It is shown by numerically integrating the equation of motion that the calculation of wave forces on the displaced position of the structure introduces a steady offset component in the structural response. This is valid for either deterministically or stochastically described wave fields. Several parameter studies are conducted. Furthermore, reliable approximate analytical deterministic and stochastic solution techniques are developed which conform to and, in fact, predict the conclusions drawn from the results of the numerical studies.
Practical Modeling for Articulated Risers and Loading Columns
Authors: McNamara J. F. , Lane M.
Published: November 2009

An efficient method for the analysis of the linear and nonlinear static and dynamic motions of offshore systems such as risers and single-leg mooring towers is presented. The technique is based on the finite element approach using connected coordinates for arbitrary large rotations and includes terms due to loads such as buoyancy, gravity, random waves, currents, ship motions and Morison’s equation. Practical features include the addition of intermediate articulations and modeling of the loading arm between the riser and associated tanker. Parametric studies are presented to show that stable and accurate results are obtained using relatively large time step increments leading to efficient design studies.
Safety Assessment of Steels and Welds Under Cyclic and Monotonic Loadings at Low Temperatures
Authors: Urabe N. , Yoshitake A. , Kagawa H.
Published: November 2009

In order to investigate the mechanisms and the factors to govern the brittle fracture initiation during the fatigue crack propagation at low temperatures, fracture toughness tests under wide range of loading rates, fatigue tests at low temperatures and fracture toughness tests after having been given pre-loading were performed on steels and weld junctions. The fatigue fracture toughness Kfc was estimated as equivalent as the fracture toughness Kc under the monotonic tensile loading if they were compared at the same loading rate, since the residual stress due to the cyclic loading was less effective on the brittle fracture initiation. The calculated fatigue life based on Paris’s formula taken into consideration of the crack closure phenomena showed a good one-by-one agreement with the observed fatigue life up to the brittle fracture initiation. Therefore, a design curve was preliminarily drawn to determine the fatigue life at low temperatures.
Design of Guylines for the Lena Guyed Tower
Authors: Power L. D. , Hayes D. A. , Brown C. P.
Published: November 2009

Exxon’s Mississippi Canyon 280-A (Lena) platform represents the first commercial application of the guyed tower concept for offshore drilling and production platforms. Unlike a conventional offshore platform, the guyed tower is held upright by an array of guylines attached near the upper end of the structure and radiating outward to anchor piles driven into the seabed. This paper describes the functional requirements of the various components of this unique guying system and shows how each component was designed to meet those requirements. Among the design parameters discussed are guying system stiffness and strength, fatigue and wear life, corrosion protection, and assembly. The major length of the guyline consists of spiral-wound bridge strand, most of which is sheathed in polyethylene. The cable constructions and terminations are described. Near the tower, the sheathed cable is connected to a length of bare cable which passes through a special fairlead arrangement to direct the cable to the upper attachment above the water line. The fairlead arrangement and the upper attachment are described as well as the means provided to protect the bare cable from corrosion. Unique pinned connections in the system are designed to ease assembly while still providing the required load capacity and service life. A special anchor pile attachment eye design allows for large tolerances in anchor pile orientation. A description of the clump weight shows how this component is designed to achieve the desired system stiffness while also providing stability against overturning or excessive settlement into the seabed.
Empirical Factors in the Prediction of Helically Armored Cable Axial Stiffness
Authors: Kurt J. P.
Published: November 2009

The object of this paper is to discuss the use of empirical factors in the prediction of armored cable axial stiffness. The stiffness of the armor wires and core that compose an armored cable are obtained from empirical data. To predict the net axial stiffness of a cable from the stiffnesses of its components a model of how the pitch diameter of an armor wire decreases as the cable is tensioned is required. The pitch diameter contraction is modeled in this paper by an experimentally determined Poisson’s ratio for the cable. The accuracy of cable axial stiffness predictions using these empirical factors is illustrated by comparing the results of mathematical models of armored cable to tension-elongation test data for ten different cables.
The Cross-Sectional Shapes of Longitudinal Hydraulic Fractures
Authors: Segalman D.
Published: November 2009

A mathematical formulation has been developed for calculating the cross-sectional shape of hydraulic fractures. This formulation treats the problem as a free-boundary-type problem and is modeled after mathematical formulations developed for contact and lubrication problems. Numerical solution of the resulting equations has been used to address problems involving particularly difficult in-situ stress distributions, including problems in which the fracture breaks through high-stress barriers. The technique is illustrated on two example problems.
Effect of Groove Shape on the Frictional Hold of a Sheave on Polyester Rope
Authors: Albro C. S. , Liu F.
Published: November 2009

This paper discusses the effects of sheave groove shape, sheave diameter, and line tension on the frictional hold of polyester rope. A series of tests were conducted using five different sheaves, 5 and 9.2-cm-dia 2-in-1 polyester rope, under both wet and dry conditions. The frictional hold was determined from the difference in rope tension on opposite sides of a rotating sheave. The maximum tension on the high side was 245 kN. It was found that the coefficient of friction between polyester rope and smooth steel sheaves decreases with increase in rope tension for a given rope size. The 70-deg-V groove sheave shape demonstrated approximately 25 percent more frictional hold than the U-groove sheave shape. Holding capacity increases with sheave diameter. Large relative velocity exists between elastic lift line and sheave surface. Data will be used in a traction winch design.
Thermodynamic Analysis of Geothermal Energy Systems With Forced Recovery From Aquifers
Authors: Lee S. K. , Reistad G. M.
Published: November 2009

A thermodynamic analysis of forced geoheat recovery from aquifers has been accomplished. The system investigated consists of a single recharging-discharging well pair, in a horizontally extensive aquifer, with either power generation or space heating as the surface application. The space heating systems investigated are (i) direct heating, (ii) heat pumps, and (iii) a combination of direct heating and heat pumps. The thermodynamic performance parameters considered are the effectiveness and fossil fuel savings. Due to the interaction between the surface and subsurface systems, the load conditions and geologic conditions play important roles in determining the thermodynamic optimum operation. For high temperature resources (higher than about 435 K), power generation yields the best performance and is therefore recommended. The relative desirability of the combination (direct heating and heat pumps) requires consideration of the load condition, resource temperature and other geologic conditions. Such evaluations for these automatically determine the appropriate ranges of direct heating. The thermodynamic optimum operation of each system is also dependent on these same parameters, as well as on the injection temperature.
An Analysis of a Method of In-Situ Thermal Properties Determination for Geologic Formations
Authors: Lin J. D. , Love T. J.
Published: November 2009

Geothermal investigations and thermal methods of oil recovery require the thermal properties of rock be known. The thermal conductivity of rock is normally determined by measuring the properties of core samples which have been removed from the well. The major problem with this is the fact that thermal properties are dependent on the moisture content of the rock. This moisture content is very likely altered in transportation and storage. This paper presents an analysis which serves as the basis of a transient heat flux probe measurement that may be used to determine the thermal conductivity and diffusivity in situ. Such in-situ measurements would overcome the disadvantages of core samples and may also be used when core samples are not available. This analysis also provides a method of estimating the time required in order to obtain valid results. The analysis indicates rather long test times may be required for accurate results. However, it does provide a basis for evaluating the results of measurements taken for shorter times. The effects of contact thermal resistance between the probe, the well casing, and the formation are evaluated.
Drag Forces on Oscillating Cylinders in a Uniform Flow
Authors: Kato M. , Abe T. , Tamiya M. , Kumakiri T.
Published: November 2009

This paper describes the drag coefficients of cylinders oscillated in both in-line and transverse directions to a uniform flow. The drag coefficients CD have been obtained experimentally over a wide range of oscillation frequencies, amplitude and flow velocities for the cylinders of various diameters under simulated practical offshore conditions. New expressions are proposed for the drag coefficients CD of an oscillating cylinder in a uniform flow. The boundary between the regions, where CD≃1 and CD<1, is clearly established by employing the Keulegan-Carpenter number and the reduced velocity as dimensionless numbers. These dimensionless numbers also clearly describe CD variation within the region of rapid CD value decrease.
Variational Embedding Technique to Inward Solidification Subject to Convection and Radiation
Authors: Chen C.-K. , Chang Y.-M. , Cleaver J. W.
Published: November 2009

The variational embedding method is presented for solving the solidified lines in the inward solidification of Cartesian, cylindrical and spherical systems with convection-radiation boundary conditions. Typical results are represented in graphical form for comparison.
Vibrations Increase Available Power at the Bit
Authors: Dareing D. W.
Published: November 2009

Drillstring vibrations are generally considered to be detrimental to downhole drilling equipment because they produce cyclic or fatigue loading. Tool joint failures, tubular washouts, and bit breakage are often fatigue related. On the positive side, dynamic forces applied to roller cone rock bits have the potential to increase penetration rate. This paper quantifies the available vibration energy at the bit and shows how to control the level of energy through bottom hole assembly design and rotary speed.
Frictional Pressure Losses for Annular Flow of Drilling Mud and Mud-Gas Mixtures
Authors: Langlinais J. P. , Bourgoyne A. T. , Holden W. R.
Published: November 2009

The calculation of single-phase and two-phase flowing pressure gradients in a well annulus is generally based on an extension of empirical correlations developed for Newtonian fluids in circular pipes. Various techniques for extending pipe flow correlations to an annular geometry have been presented in the literature which involve the representation of the annular well geometry with an equivalent circular diameter and the representation of non-Newtonian fluid behavior with an apparent Newtonian viscosity. Unfortunately, little experimental data have been available which would allow a comparison of the relative accuracy of the various proposed techniques. In this study, experimental pressure gradient data have been taken in two 6000-ft wells. Frictional pressure losses for single-phase flow (mud only) in two annuli were compared to values predicted by the Bingham plastic and power law models. These calculations utilized the equivalent diameters defined by the Crittendon criteria, the hydraulic diameter, and the slot approximation. Also, total pressure difference for two-phase flow was measured for one annular geometry. This data was compared to that predicted by the Poettmann and Carpenter, Hagedorn and Brown, Orkiszewski, and Beggs and Brill correlations. Comparison of experimental data with the various prediction techniques was favorable, each having advantage in certain situations. For the data investigated, the Crittendon criteria using a Bingham plastic model gave the best results. The two-phase flow data was best predicted by the Hagedorn and Brown correlation utilizing an equivalent hydraulic diameter.
Potential of Recycling Ash From Resource Recovery Facilities in California
Authors: Vence T. D.
Published: November 2009

In 1981, in response to Industry and government interest in recovering materials ordinarily destined for disposal, the California State Solid Waste Management Board commissioned a study entitled Utilization of Residue From Resource Recovery Facilities. This research project has encompassed examination of all aspects of residue utilization—technical, environmental, economic, institutional and regulatory—in an effort to accurately determine the promise and problems of developing residue utilization. The report serves as both a documentation of research and a source document for those desiring further information. Most of the research activity on residue recycling occurred during the period from the middle 1960’s to early 1970’s. The hiatus, however, appears to be ending with a current upswing of research activity in the United States. While both foreign and domestic residue recycling activities were examined, it is important to note that this report concentrates on the domestic development of residue recycling; the prohibitive cost of document translation prevented access to some foreign reports. While several promising applications have been identified for residue, the best demonstrated use is as an aggregate material in bituminous base course pavements. Residue has also been shown to perform excellently as subbase and fill material; however, use of residue in this manner raises serious environmental questions in California.
Added Mass and In-Line Steady Drag Coefficient of Multiple Risers
Authors: Overvik T. , Moe G.
Published: November 2009

Part of the results of an investigation with multiple rise configuration exposed to steady currents are presented. These tests were performed on smooth sectional riser models in a water flume at Reynolds numbers in the range 0.5 × 104 to 0.5 × 105. Reynolds number is based upon the diameter of the central cylinder (DC). Both the added mass, the frequency of vibration and the in-line steady drag coefficient are discussed both for vibration in the lock-in range and in the galloping mode.
Comparisons of Simulation Methods for Motions of a Moored Body in Waves
Authors: Takagi M. , Saito K. , Nakamura S.
Published: November 2009

Based on the linear water wave theory, numerical simulations are carried out for motions in waves of a body moored by a nonlinear-type mooring system. Numerical results obtained by using the equation of motion described in the time domain with a convolution integral (C.I. method) are compared with those of the second-order linear differential equation with constant coefficients (C. C. method). These results are also compared with experimental values measured from the initial stage when the action of exciting forces starts and the validity of C.I. method is discussed.
A Concept for Design of Submarine Pipelines to Resist Ocean Forces
Authors: Karal K.
Published: November 2009

A philosophy for design of submarine pipelines on the seabed to resist ocean forces is proposed. According to it, the pipeline response to hydrodynamic forces is calculated and the predicted response parameters are compared with the permitted values given by the design criteria. Some guidelines are given to achieve compatibility of individual elements in the design procedure.
Large Displacement Analysis of a Marine Riser
Authors: Huang T. , Chucheepsakul S.
Published: November 2009

A method of static analysis for a marine riser experiencing large displacements is presented. The method is suitable for analyzing a riser having a known top tension and a possible slippage at the top slip joint. Utilizing the stationary condition of a functional coupled with an equilibrium equation, one can conveniently obtain the equilibrium configuration numerically. The configuration is expressed in terms of the rectangular coordinates. The functional representing the energy and work of the riser system is expressed in terms of the horizontal coordinate which is parameterized in terms of the vertical depth instead of arc length. For a two-dimensional problem, two multipliers must be included in the functional. One of the two represents the variable axial force along the length of the riser and the other corresponds to the strain energy per unit riser length due to bending. Utilizing the finite element method, a numerical procedure to obtain the configuration of static equilibrium is given. The resulting algebraic equations are highly nonlinear and the Newton-Raphson iterative procedure is used to solve the equations. An example is given.
Corrosion Fatigue Tests on Welded Tubular Joints
Authors: Iwasaki T. , Wylde J. G.
Published: November 2009

The corrosion fatigue performance of welded tubular joints is recognized as one of the most important factors in the design of offshore structures. Because of the cost of such tests it has been practice to carry out tests on tubular joints in air and to perform corrosion fatigue tests on simple welded joints. Thus very few corrosion fatigue tests have been carried out on tubular joints. The present paper describes the results of fatigue tests which have been carried out on welded tubular joints both in air and in a sea water environment. The specimens were tubular K and KT-joints with chord dimensions of 168 mm diameter and 6 mm wall thickness. The tests were carried out under out-of-plane bending. The corrosion fatigue tests were carried in sea water at 10° C at a frequency of 10 cycles per min, which is typical of wave periods. The specimens were not cathodically protected. The fatigue results in air and sea water are compared, and discussed in connection with the current fatigue design S-N curves for tubular joints contained in various standards.
The Q.U.B. Axisymmetric and Multi-Resonant Wave Energy Convertors
Authors: Whittaker T. J. T. , Leitch J. G. , Long A. E. , Murray M. A.
Published: November 2009

This paper describes the optimization of the power conversion chain and the engineering design considerations of an oscillating water column wave power device which would form part of a 2-GW power station. Novel features of the principal device described include the multi-resonant concept, which considerably widens the frequency bandwidth response, and the use of the simple highly efficient Wells self-rectifying air turbine in the secondary power conversion stage. It is concluded that using established technology wave power stations comprising sea bed mounted reinforced concrete structures could produce power for as little as 1.3p per kW-hr after the initial capital repayment period and thus the economics are similar to that of hydro-electric power.
A Preliminary Examination of the Effect of Structure on the Compressive Strength of Ice Samples From Multi-Year Pressure Ridges
Authors: Richter J. A. , Cox G. F. N.
Published: November 2009

A series of 222 uniaxial constant-strain-rate compression tests was performed on vertical multi-year pressure ridge sea ice samples. A preliminary analysis of the effect of structure on the compressive strength of the ice was performed on 78 of these tests. Test parameters included a temperature of −5°C (23°F) and strain rates of 10−5 and 10−3 s−1. Columnar ice loaded parallel to the elongated crystal axes and perpendicular to the crystal c-axis was consistently the strongest type of ice. The strength of the columnar samples decreased significantly as the orientation of the elongated crystals approached the plane of maximum shear. Samples containing granular ice or a mixture of granular and columnar ice resulted in intermediate and low strength values. No clear relationship could be established between structure and strength for these ice types. However, in general, their strength decreased with an increase in porosity.
The Variation of Ice Strength Within and Between Multiyear Pressure Ridges in the Beaufort Sea
Authors: Weeks W. F.
Published: November 2009

A recent series of tests on the uniaxial compressive strength of ice samples taken from multiyear pressure ridges allows the testing of several hypotheses concerning the variation in strength within and between ridges. The data set consists of 218 strength tests performed at two temperatures (−5° and −20°C) and two strain rates (10−3 and 10−5 s−1). There was no significant difference between the strength of the ice from the ridge sails and the ice from the ridge keels when tested under identical conditions. As the total porosity of the ice from the sails is higher by 40 percent than the ice from the keels, the lack of a significant difference is believed to result from the large variations in the structure of the ice which occur randomly throughout the cores. A three-level analysis of variance model was used to study the variations in strength between 10 different ridges, between cores located side by side in a given ridge, and between samples from the same core. In all cases the main factor contributing to the observed variance was the differences within cores. This is not surprising considering the rather extreme local variability in the structure of ice in such ridges. There was no reason at the 5 percent level of significance to doubt the hypothesis that the different cores at the same site and the different ridges have equal strength means.
A Technique for Producing Ice From NaCl Brine for Studying Fundamental Deformation Behavior
Authors: Godavarti P. S. , Pharr G. M.
Published: November 2009

The deformation behavior of frozen saline soils involves a complex interaction between non-deformable particles (soil) and a plastic solid (ice) containing a liquid phase (brine). In order to understand this, it is highly desirable to characterize the deformation behavior of the ice-brine system alone. However, preparation of ice-brine specimens suitable for laboratory testing is difficult because migration of brine during freezing produces inhomogeneous brine distributions. To overcome these difficulties, a liquid phase sintering technique has been developed to produce ice specimens from NaCl brine. The details of the process and the resulting microstructures are presented.
Use of the Cone Penetration Test for the Design of Piles in Permafrost
Authors: Ladanyi B.
Published: November 2009

Experience gained in recent years in performing cone penetration tests in frozen soils, both in the field and in cold room, leads to the conclusion that certain frozen soil properties needed in foundation design can be successfully determined by that test, provided suitable high-capacity, rate-controlled, cone-driving equipment is available. In addition, as shown in this paper, due to its similarity with the driven pile, the tests can be used directly for pile design in frozen soils through a scaling method which takes into account the effects of size, strain rate and temperature. The paper proposes such a design method for piles under axial load, and discusses the possibility of using the CPT data also in connection with the design of laterally loaded piles.
Offshore Permafrost Well Design Lateral Soil Movement-Induced Bending Strains
Authors: Laut S. W. , Bradshaw M. T.
Published: November 2009

Offshore production wells placed through permafrost are subjected to lateral soil forces when production of hot oil thaws the surrounding permafrost. Previous work completed indicates lateral soil movements in the Canadian Beaufort Sea to be large enough to cause severe bending strains in the well casing if the well casing moves with the soil. A lateral pile program was utilized to determine the bending strains induced in the well casing subjected to a free-field displacement of the thawed permafrost soil. Parametric studies were undertaken to determine the effect of varying soil properties and well casing rigidity for a given free-field displacement. The results show well casing strains to be lower than first predicted as the well casing does not move exactly with the soil.
Creep of Frozen Sand Under Isotropic and Deviatoric Components of Stress
Authors: Domaschuk L. , Knutsson S. , Shields D. H. , Rahman M. G.
Published: November 2009

The creep behavior of frozen soil is being studied by examining its response to changes in the mean normal stress and changes in the deviatoric components of stress, using separate tests. The two response components will then be coupled to provide a model for a general stress state. The paper contains the results of three triaxial compression creep tests on frozen sand (T = −3°C) in which the samples were subjected to changes in the deviatoric components of stress only. Stepwise stress increases were applied for periods up to 1700 hr during which volumetric and axial strains were measured. The samples underwent attenuating creep when subjected to low stress levels and accelerating creep when subjected to higher stress levels, with no indication of a significantly long period of steady-state creep. The samples underwent volume reduction when the axial strains were attenuating and dilated when the axial strain rates began to accelerate.
Analysis of Corrosion Fatigue Crack Growth in Welded Tubular Joints
Authors: Hudak S. J. , Burnside O. H. , Chan K. S.
Published: November 2009

An improved fracture mechanics model for fatigue crack growth in welded tubular joints is developed. Primary improvements include the use of a wide-ranged equation for the fatigue crack growth rate properties and the incorporation of the influence of local weld-toe geometry into the stress intensity factor equations. The latter is shown to explain the dependence of the fatigue life on the size of tubular joints. Good agreement between predicted and measure fatigue lives of full-scale joints tested in air further supports the applicability of the fracture mechanics approach to offshore structures. Although the model should also be applicable to corrosion fatigue, additional imput data and verification testing are needed under these conditions. Factors which could improve the model are discussed.