bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Fluid Damping Using Random Excitation
Authors: Yang J. C. S. , Marks C. H. , Jiang J. , Chen D. , Elahi A. , Tsai W-H.
Published: November 2009

An experimental investigation has been carried out to verify the validity of the use of the random decrement technique to determine the damping coefficients for a circular cylinder oscillating in water. Data are reported for amplitudes ranging from 0.4 diameters to 0.8 diameters, for water speeds from zero to 0.192 m/s (0.63 ft/sec), and for frequencies ranging from 0.37 Hz to 1.4 Hz. Comparison with other data, which has been reported in the literature or obtained by the authors, shows that the random decrement method yields comparable damping coefficients to those obtained using the logarithmic decrement technique for the range of variables in this experiment.
Hydrodynamic Forces on Multitube Production Risers Exposed to Currents and Waves
Authors: Demirbilek Z. , Halvorsen T.
Published: November 2009

This paper presents the experimental results of a joint industry riser test program. Over a five-year period, an extensive experimental investigation of hydrodynamic loads acting on various production risers was carried out. The program included the laboratory testing of many multitube riser configurations as well as a single cylinder. Several major oil companies sponsored the project. The tests were made with rather large-scale models which were: 1) held stationary in steady current, 2) moved at constant speed or constant acceleration through a quiescent fluid or through a moving fluid, and 3) held stationary in oscillating flow or in steady current superimposed on oscillating flow. The primary objective of this investigation was to establish an accurate measurement of the hydrodynamic forces on bundle-type risers. The findings from this study will be presented in two papers. In the first, we shall present the hydrodynamic force coefficients for some marine risers consisting of one or more cylinders interacting either only with currents or oscillatory flow separately. In a companion paper, the pertinent data for the joint presence of the oscillatory flow and currents will be discussed. Among the results outlined here are the drag, inertia, and lift coefficients for various composite risers as a function of the Reynolds and Keulegan-Carpenter numbers. An analysis and synthesis of the test data are also presented.
Optimization in Oil and Gas Pipeline Engineering
Authors: Huang Z. , Seireg A.
Published: November 2009

A survey of applications of optimization techniques in oil and gas pipeline engineering is presented. These applications include the optimal design, optimal expansion, optimal control and optimal operation of pipeline systems. Applications in off shore pipeline engineering is also involved.
The Development and Testing of a Wave-Activated Navigation Buoy With a Wells Turbine
Authors: Whittaker T. J. T. , McPeake F. A. , Barr A. G.
Published: November 2009

This paper presents and discusses the results of the first stage of an ongoing research program to improve the design of wave powered navigation aids using the oscillating water column principle. Wave tank testing has shown that the heave motion of current tail tube buoys is the predominant feature of the hydrodynamic response. A Wells self rectifying air turbine, coupled to a 100-W generator which produces an optimum level of damping to the water column for peak performance, has been designed and tested. It has been concluded from preliminary sea trails that a simple, efficient, reliable, turbine-generator has been developed to meet the requirements of the current design of navigation buoy. However there is considerable scope for improving the hydrodynamic design of wave activated buoys.
Multiple Artificial Geothermal Cracks in a Hot Dry Rock Mass for Extraction of Heat
Authors: Shibuya Y. , Sekine H. , Takahashi Y. , Abe´ H.
Published: November 2009

Theoretical analysis is made for multiple geothermal cracks. A periodic array of two-dimensional cracks is considered as a model of the multiple geothermal cracks, and is anlayzed on the basis of the two-dimensional theory of quasi-static thermo-elasticity. The singular integral equations are derived from the boundary conditions, and they are solved by applying the combination of inversion formula and collocation method. Numerical results for the fluid temperature at an outlet, the rock mass temperature, the shape of the geothermal cracks and the stress distribution around the geothermal cracks are shown in graphs.
Large-Scale Rotary Shear Shredder Performance Testing
Authors: Spencer D. B. , Temple J. W. , Forsythe D. M. , Bond B. E.
Published: November 2009

Slow-speed rotary shear shredders have recently received considerable attention for processing of municipal solid waste. Potential benefits from shear shredding could include reduced explosion potential, lower power consumption, lower operating and maintenance costs and less overgrinding of glass. Although there has been much interest in rotary shear shredders, little actual operating data exists showing the capacity and performance of these units on municipal solid waste at full scale. A large-scale, 50 tph (45.3 tonnes/hr) Iowa Manufacturing Company (Cedarapids) Model 5096 (127 cm × 244 cm) shear shredder was installed and has been evaluated over a 6-mo period at the Charleston County Solid Waste Reduction Center. Two Heil 42F vertical shaft hammermills also are operated at the reduction center. Long-term landfill tests were conducted on waste processed by both shredders to measure the performance of the shear shredder and compare the effect of shredder type on landfilling characteristics. These results show capacity in excess of 60 tph (54.4 tonnes/hr) using 4-in. (10-cm) cutters and comparable landfilling characteristics for both types of shredders.
A Strip Method for Lateral Drift Force of a Semisubmersible
Authors: Kim C. H. , Bao W.
Published: November 2009

This paper presents the results of an application of a strip technique for the prediction of the lateral drift forces on a semisubmersible platform floating in oblique regular waves. The method employs Maruo’s formula and source distribution technique, without taking account of the hydrodynamic interaction between the twin hulls and columns of the semisubmersible. Overall the strip technique shows a more favorable correlation with the experimental data than the three-dimensional theory. It is, however, premature to conclude that the technique has been fully validated.
Optimum Design of Submarine Suspended Pipelines
Authors: Huang Z. , Seireg A.
Published: November 2009

Almost all submarine pipelines are currently laid on the sea floor. This practice is inherently expensive and the system is difficult to maintain and has a high possibility of excessive bending stress. The concept of suspending a pipeline under the ocean surface is investigated in the reported study. An optimum design algorithm is developed which can minimize the dynamic oscillation and the tensile stress of the pipeline resulting from the wave excitation. Numerical examples are given to illustrate the optimization procedure.
Behavior of Damaged Tubular Structural Members
Authors: Ueda Y. , Rashed S. M. H.
Published: November 2009

An analytical model of dented tubular members is constructed. Using this model, an ultimate strength interaction relationship between axial force and biaxial bending moments is derived. The implementation of this interaction relationship to take account of denting and bending damage in the analysis of nonlinear behavior of tubular space frames by ISUM (the Idealized Structural Unit Method) is described. An experimental study of the behavior of dented members subjected to pure bending is reported. Comparison with theoretical predictions is presented.
A Design Formulation for Axisymmetric Collapse of Stiffened and Unstiffened Cylinders
Authors: Croll J. G. A. , Ellinas C. P.
Published: November 2009

A procedure, developed for predicting the elastic-plastic general axisymmetric collapse of stiffened and unstiffened cylinders, is presented. This permits the formulation of reliable lower bounds to collapse loads for any combination of radial pressure and axial loadings, with any prescribed forms and levels of initial geometric imperfection, in a simple, “column-type,” analysis. The approach provides a unified format for the treatment of isotropic and orthotropic cylinder buckling, which is compact and design orientated.
Protection of Arctic Submarine Pipelines Against Ice Scour
Authors: Nessim M. A. , Jordaan I. J.
Published: November 2009

A decision-theoretic approach to the problem of optimizing strategies for the protection of submarine pipelines against ice scour is presented. The model simultaneously considers twinning, deep trenching, and valve segmentation. The opitmal solution is dependent on the uncertainty regarding the frequency of pipeline damage and the associated consequences. Two sources of uncertainty are considered, namely the rate and the depth of scour. Consequences of pipeline damage are represented by their impact on economy and enviornmental safety. An example is presented and the model is used to check the sensitivity of the optimal solution to different input parameters.
A Damage Mechanics Model for Uniaxial Deformation of Ice
Authors: Karr D. G.
Published: November 2009

A one-dimensional stress-strain relationship is developed for pure polycrystalline ice subjected to uniaxial compression. The model is based on the continuous damage theories and includes the effects of elastic, plastic and brittle deformation mechanisms. A damage law for ice is established based on a statistical model for internal microfracture. Quantitative results are presented by directly relating the formation of internal cracks to published acoustic emission response of ice samples subjected to compression.
Tensile Strength of Multi-Year Pressure Ridge Sea Ice Samples
Authors: Cox G. F. N. , Richter-Menge J. A.
Published: November 2009

Thirty-six constant strain-rate uniaxial tension tests were performed on vertically oriented multi-year pressure ridge samples from the Beaufort Sea. The tests were performed on a closed-loop electro-hydraulic 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 tensile strength, initial tangent modulus, and failure strain of the ice.
Quantitative Analysis of Ice Sheet Failure Against an Inclined Plane
Authors: Frederking R. M. W. , Timco G. W.
Published: November 2009

The main force components on inclined offshore structures in the Arctic include the flexural and crushing behavior of the ice sheet, rotation and translation of broken ice, gravity and buoyancy in lifting and moving ice, and friction between ice and structure. Tests were carried out to isolate these components and analytical expressions were derived for them. Measured and predicted components compare favorably, the analytical model overpredicting by about 20 percent.
Analysis of Fiber-Core Wire Rope
Authors: Velinsky S. A.
Published: November 2009

A theory has been developed for the analysis of fiber-core wire rope with multilayered strands. The rope is subjected to both an axial force and an axial twisting moment. The previously developed linear theory for helically shaped wires is used and the equations governing compliance of the fiber core are formulated in a linear fashion. The resultant linear equations are easily solved. The theory is applied to a 6 × 19 Seale fiber-core wire rope and dimensionless results are presented. A load-deformation curve for a Seale fiber-core wire rope is obtained experimentally. Both the theoretically predicted effective modulus of elasticity and the predicted effective Poisson’s ratio of the rope compare favorably with the experimental results.
Simulation of a Major Oilfield Gas-Gathering Pipeline System
Authors: Brill J. P. , Sifferman T. R. , Samaroo B. , Arirachakaran S.
Published: November 2009

An engineering design study was performed on a gas-gathering system in a major offshore oilfield in Saudi Arabia. The dew point gas from separators will undergo retrograde condensation in the pipelines with reduction of pressure and temperature. Calculations presented for sizing the pipelines include phase behavior, pressure drop, temperature profiles, liquid volumes, flow pattern predictions, liquid flow rates and the minimum gas velocity required to continuously remove liquid from the risers.
Riser Instrumentation: Deep Water Drilling Campaign Results
Authors: Schawann J.-C. , Sparks C.
Published: November 2009

During the 1982–1983 drilling campaign in the Mediterranean, two wells were drilled by the Discoverer Seven Seas in record water depths of 1714 m and 1252 m. The riser was equipped with instruments to measure tensions, moments and angles at points close to the extremities. Simultaneously ship motions and environmental conditions including current measurements at various depths were recorded by ELF AQUITAINE and I.F.P. A large quantity of data relating to riser behavior was gathered and recorded. The results available for publication include raw data relating to the evolution of current at different depths, long period lateral ship motion acting at the riser top end, induced by the dynamic positioning system. Simultaneous measurements of angles at extremities were recorded to confirm the validity of two-dimensional riser analysis. Measurements of riser parameters made with deliberately large ship excursions from the vertical, enabled the riser practical profile to be compared with the theoretical one. Measurements, made with the riser hung off in storm conditions, confirmed the existence of large dynamic tensions and enabled them to be compared with the theoretical values. Correlation of the fluctuation of cable tension with ship heave has led to practical values of tensioner stiffness.
Free Span Vibrations of Submarine Pipelines in Steady Flows—Effect of Free-Stream Turbulence on Mean Drag Coefficients
Authors: To̸rum A. , Anand N. M.
Published: November 2009

In this paper part of the results of a laboratory study related to free span vibrations of submarine pipelines in steady and wave-induced fluid flows are summarized. Tests have been carried out using an elastically supported rigid smooth circular cylinder close to a plane smooth boundary in steady flows with turbulence intensities of 3.4, 5.5, and 9.5 percent for four cylinder gap to diameter ratios, G/D equal to 0.5, 0.75, 1.0, and 3.0. The range of Reynolds numbers based on mean velocity of flow and cylinder diameter was 0.65·104 to 0.35·105. Effect of turbulence intensity on the mean drag force and vibration amplitudes are discussed.
A Slender-Body Theory for a Rigid Pile Under Static or Low-Frequency Axial Loading
Authors: Fallou S. N. B. , Mei C. C.
Published: November 2009

If the seabed is modeled as a poroelastic medium, the stresses and pore pressure induced by sea waves attacking pile-supported structures can be approximately treated by a quasi-static, single-phase theory almost everywhere except near the unsealed mudline. Therefore, the theory of a pile in an elastic half-space is fundamental. A survey of literature indicates that existing theories are only numerical; the few analytical formulas are based on either intuitive argument or interpolation of numerical work. A more systematic theory is first developed here for an axially loaded pile by employing slender-body approximation to a pair of integral equations. The results are used to calculate the pore pressure in the seabed around low-frequency loading.
Effect of Soil Anisotropy on the Wave-Induced Pore Pressures in the Seabed
Authors: Silvestri V. , Soulie´ M. , Marche C. , Louche D.
Published: November 2009

Waves propagating over the ocean bottom create pressure waves on the seafloor, which during severe storms can lead to significant deformations or even failure. To investigate this phenomenon, a theoretical analysis of the wave-induced pore-water pressures in a semi-infinite bed of cohesionless soil has been performed. This analysis is based on the poroelastic theory of Biot and an anisotropic soil model, which allows us to consider physical properties, such as dilatancy. A much broader spectrum of soil responses can then be considered through the analysis. A parametric study has been performed to assess the effects of these factors. In addition, we compare the results from theoretical predictions with the pore pressure data obtained from a field monitoring program.
Comparative Evaluation of Fracture Mechanics Methodologies as Applied to Offshore Structural Design and Integrity Analyses
Authors: Rhee H. C. , Salama M. M.
Published: November 2009

A comparative study was performed to evaluate the three most widely used elastic-plastic fracture mechanics methodologies. The three methods are the crack opening displacement (COD) design curve, which is widely used in the offshore industry, the British Central Electricity Generating Board (CEGB) R6 method, and the J-resistance curve method. Analyses of various flawed geometries based on these three methods were performed using consistent material fracture properties. The results of both the COD and R6 methods were compared with those of the J-resistance curve, which is the most rigorous of the three methods. The results of the COD concept, following BSI PD 6493 procedures, appear to be conservative at applied stress levels below 60 percent of the material yield strength and unconservative above this value. However, the results of the R6 method appear to be consistently conservative. The behavior of COD design curve solutions can be improved when the structural geometry and the actual stress-strain relationship are properly considered in the analyses.
Structure, Salinity and Density of Multi-Year Sea Ice Pressure Ridges
Authors: Richter-Menge J. A. , Cox G. F. N.
Published: November 2009

Data are presented on the variation of ice structure, salinity, and density in multi-year pressure ridges from the Beaufort Sea. Two continuous multi-year pressure ridge cores are examined as well as ice sample data from numerous other pressure ridges. The results suggest that the large scale properties of multi-year pressure ridges are not isotropic, and that the use of anisotropic ridge models may result in lower design ridge ice loads.
A Model for Jet Piercing of Oil Sands
Authors: Gates E. M. , Toogood R. W.
Published: November 2009

The impact of a stationary confined high pressure water jet on a solid surface has been investigated. Flow visualization by high-speed photography and measurements of average surface pressures show the action of the jet is to exert a series of discrete impulses rather than a steady force. It appeared more appropriate then to analyze the pressure data statistically to obtain the probability of occurrence of pressures above a critical value required for failure of the material. These probability values were then incorporated into a cutting model to predict jet piercing rates and expected maximum depths of penetration. Comparison of these model predictions with some limited field data was then carried out.
General Solutions for Pistonlike Displacement of Compressible Fluids in Porous Media
Authors: Advani S. H. , Torok J. S. , Lee J. K.
Published: November 2009

Exact solutions for the one-dimensional problem of a compressible fluid having a time-dependent pressure at the source (fracture face) and displacing a compressible reservoir fluid are generated. Special solutions for various cases represented by step, step with constant slope front, and sinusoidal pressure variations at the fracture face are derived. Numerical results and trends for fluid interface motion are revealed for selected cases. The applicability of the presented solutions to hydraulic fracturing is discussed. In addition, response solutions for problems in reservoir mechanics, underground coal gasification, and nuclear waste management can be similarly investigated.
Pressure Drop Correlations for Inclined Two-Phase Flow
Authors: Mukherjee H. , Brill J. P.
Published: November 2009

Pressure drop behavior in two-phase inclined flow was studied. For bubble and slug flow, a no-slip friction factor calculated from the Moody diagram was found adequate for friction head loss calculations. In downhill stratified flow, the friction pressure gradient is calculated based on a momentum balance equation for either phase assuming a smooth gas-liquid interface. For this calculation, a prior knowledge of the liquid holdup is needed. For annular-mist flow, a friction factor correlation is presented that is a function of holdup ratio and no-slip Moody friction factor. Results agree well with the experimental data and correlations were further verified with Prudhoe Bay and North Sea data.
A Simplified Approach on the Elastic-Plastic Analysis of Threaded Connectors
Authors: Chen L. Y. , Williams M. R.
Published: November 2009

The design of threaded connectors based on an elastic analysis appears overly conservative. This, in turn, will result in unnecessary material and manufacturing costs. To improve cost effectiveness, the design of connectors from the elastic-plastic viewpoint is warranted. This paper presents a simplified approach on the elastic-plastic finite element analysis of connectors. This approach would save tremendous computer costs which may be incurred in conducting a regular elastic-plastic analysis of threaded connectors.
Fracture Propagation in Underwater Gas Pipelines
Authors: Maxey W. A.
Published: November 2009

Two full-scale ductile fracture propagation experiments on segments of line pipe pressurized with nitrogen gas have been conducted underwater at a depth of 40 ft (12 m) to evaluate the ductile fracture phenomenon in underwater pipelines. The pipes were 22-in. (559-mm) diameter and 42-in. (1067-mm) diameter. Fracture velocities were measured and arrest conditions were observed. The overpressure in the water surrounding the pipe resulting from the release of the compressed nitrogen gas contained in the pipe was measured in both experiments. The overpressure in the water reduces the stress in the pipe wall and thus slows down the fracture. In addition, the water surrounding the pipe appears to be more effective than soil backfill in producing a slower fracture velocity. Both of these effects suggest a greater tendency toward arrest for a pipeline underwater than would be the case for the same pipeline buried in soil onshore. Further verification of this effect is planned and a modified version of the existing model for predicting ductile fracture in buried pipelines will be developed for underwater pipelines.
Cable Recovery With Overrun
Authors: Shashaty A. J.
Published: November 2009

Cable is normally recovered by hauling in from ahead, with the cable guiding the ship. In an early paper, Zajac presented a method for recovery, proposed by Shea, in which the cable is overrun, and hauled in tending aft. The potential advantage is lower tension in recovery. Cable was recovered with overrun in two recent exercises. The tensions and cable angles observed at the ship in these exercises are used to work out cable configurations and bottom tensions. The calculations show that the bottom tension was considerably less than it is for normal recovery in both exercises. As the overrun is increased, the tension decreases, and tends to a limiting value defined by the ship speed and the slack rate at which the cable was originally laid. Recovery with overrun is practical and advantageous.
The Effect of Cable Dynamics on the Station-Keeping Response of a Moored Offshore Vessel
Authors: Ansari K. A. , Khan N. U.
Published: November 2009

An anchoring system for an offshore structure must meet certain prescribed requirements controlled by factors such as the site environment, operational constraints and the vessel employed. Its adequacy, survival and ability to stay on site must, therefore, be checked out with proper methods of analysis. The inclusion of cable dynamics is an important consideration in the dynamic analysis of a moored vessel. In this paper, mooring line equations of motion are derived for a multi-component, n-segment model using Lagrange’s modified equation, permitting anchor motion, and then numerically solved to yield time histories of cable displacements and cable tensions for the various cable configurations that can occur. Initial conditions can be provided through the mooring line static catenary equations. The nonlinear restoring force terms in the vessel equations of motion are generated through the dynamic tension- displacement characteristics of individual lines. The equations of motion of the moored vessel subjected to an open ocean environment are then numerically solved to yield time histories of vessel motions and cable tensions. An example involving a moored production barge is examined and results are compared with those of previous work in which a quasi-static cable configuration is employed.
Vortex-Induced Response of a Flexible Cylinder in a Sheared Current
Authors: Patrikalakis N. M. , Chryssostomidis C.
Published: November 2009

In this paper we outline a method for the approximate prediction of the static and lift responses of a flexible cylinder in a unidirectional variable stream. Our prediction is based on information derived from experimental results involving rigid cylinders forced to oscillate sinusoidally orthogonally to a uniform stream. Our approach represents the multifrequency lift response of a flexible cylinder in a sheared current by predicting a number of independently determined, monochromatic, multimode dynamic solutions. For each such multimode solution, our procedure allows the simultaneous evaluation of lift response frequency, amplitude, and phase between modes. A numerical example assuming bimodal solutions is included to illustrate our method for the geometry of a single-tube marine riser.
The Coefficient of Friction Between Sea Ice and Various Materials Used in Offshore Structures
Authors: Saeki H. , Ono T. , Nakazawa N. , Sakai M. , Tanaka S.
Published: November 2009

When structures having inclined surfaces, such as cone-type and inclined-pile structures, are constructed in coastal and offshore cold regions, sea ice forces must be considered in their design. In order to estimate these forces, the relationships of the coefficients of static and kinetic friction between sea ice and construction materials must be evaluated. The authors have been conducting, for four years, experiments on the coefficients of friction between sea ice and various commonly used offshore construction materials such as concrete and steel. This paper summarizes the results of this study. The coefficients of friction have been found to be affected by the following: (i) relative velocity (i.e., velocity of construction material relative to sea ice); (ii) sea ice temperature; and (iii) surface roughness of construction material. They have been found to be relatively unaffected by the following: (i) contact area, (ii) normal stress, (iii) growth direction of sea ice, and (iv) water at the sea ice-material interface.
Sensitivity of Flexibility Monitoring of Offshore Jacket Platforms
Authors: Rubin S. , Coppolino R. N.
Published: November 2009

Flexibility monitoring is a vibration-based method for simplifying the detection of major underwater damage on offshore jacket platforms. Ambient vibrations are detected at each of the underwater framing levels relative to abovewater vibration in the fundamental sway and torsional modes. Derived are flexibility parameters which relate to the shear flexibilities of each framing bay and of the foundation. Great promise has been shown by laboratory and field testing. This paper presents a comprehensive sensitivity assessment for severance of diagonal members over a wide range of structural redundancy for generic platform configurations.
An Approximate Solution for the Potential Flow of a Pore Fluid Into a Slotted Cylinder
Authors: Fahrenthold E. P. , Cheatham J. B.
Published: November 2009

Conformal mapping may be used to approximate the two-dimensional pore pressure distribution around a cylinder with a single longitudinal slot. A nonsymmetric flow field can significantly affect the stress distribution around a slotted casing. In order to investigate analytically the importance of such asymmetry on incipient rock yielding and casing collapse in producing wells, an approximate solution is obtained for the pore pressure distribution in the extreme case of a cylinder with a single slot. The derived solution does not employ the Schwartz-Christoffel transformation used in previous work. Hence the resulting expression gives the pore pressure as an explicit function of position. Comparison with the exact solution for typical reservoir radius to casing radius ratios gives predicted flow rates correct to within one percent.
Comparison of Hydraulic Fracture Models for Highly Elongated Fractures of Variable Height
Authors: Palmer I. D. , Luiskutty C. T.
Published: November 2009

There is a pressing need to compare and evaluate hydraulic fracture models which are now being used by industry to predict variable fracture height. The fractures of concern here are vertical fractures which have a pronounced elongation in the direction of the payzone, i.e., there is a dominant one-dimensional fluid flow along the payzone direction. A summary is given of the modeling entailed in the basic ORU fracture model, which calculates fracture height as a function of distance from the wellbore in the case of a continuous sand bounded by zones of higher (but equal) minimum in-situ stress. The elastic parameters are assumed the same in each layer, and injected flow rates and fluid parameters are taken to be constant. Leak-off is included with spurt loss, as well as non-Newtonian flow. An advantage of the model is its small computer run time. Predictions for wellbore height and pressure from the ORU model are compared separately with the AMOCO and MIT pseudo-3D models. In one instance of high stress contrast the ORU wellbore pressure agrees fairly well with the AMOCO model, but the AMOCO wellbore height is greater by 32 percent. Comparison between the ORU and MIT models in two cases (also high stress contrast) indicates height disagreement at the wellbore by factors of 1.5–2.5 with the MIT model giving a lower height. Thus it appears there can be substantial discrepancies between all three models. Next we compare the ORU model results with six cases of elongated fractures from the TERRA-TEK fully-3D model. Although two of these cases are precluded due to anomolous discrepancies, the other four cases show reasonable agreement. We make a critical examination of assumptions that differ in all the models (e.g., the effective modulus-stiffness multiplier approximation in the AMOCO model, the effect of finite fluid flow in the vertical direction in the MIT model, and the effect of 2D flow and limited perforated height in the TERRA-TEK model). Suggestions are made for reconciling some of the discrepancies between the various models. For example, the ORU/AMOCO height discrepancy appears to be resolved; for other discrepancies we have no explanation. Our main conclusion is that the AMOCO, TERRA-TEK and ORU models for fracture height and bottomhole pressure are in reasonable agreement for highly elongated fractures. Despite the difficulties in understanding the different models, the comparisons herein are an encouraging first step towards normalizing these hydraulic fracture models.
A Numerical Study of Geothermal Well Flow With Salts and Noncondensables Present
Authors: Michaelides E. E. , Shafaie F. F.
Published: November 2009

This work examines the upward natural or forced flow of geothermal fluids in liquid-dominated wells. The objective of the project is to develop a model that would adequately describe these flows and would yield predictions of use to geothermal engineers and plant designers. The unique part of this model is that it takes into account the presence and the effect of noncondensable gases, such as CO2, in the flow as well as the salts, such as NaCl. In the subsequent sections the two-phase flow equations are developed and solved with the help of a computer program. The results obtained agree well with experimental data and qualitative expectations.
Model Test of an Ice Class Bulk Carrier With the Thyssen/Waas Bow Form
Authors: Freitas A. , Nishizaki R. S.
Published: November 2009

Alternative bow forms have been investigated for the “M. V. Arctic” in a test program sponsored by the German Ministry for Research and Technology and the Transportation Development Centre of Transport Canada. The “M. V. Arctic” is a Canadian Arctic Class 2 bulk carrier of 28000 dwt which operates between the Northwest Territories and Europe during the summer and fall months. The tests were conducted at the Hamburg Ship Model Basin using a 1/30th scale model fitted with three different forebody forms. These included the Thyssen/Waas design, a new design by Melville Shipping Ltd., Calgary, and the existing bow form. The tests were performed in ice, still water and irregular seaway. The Thyssen/Waas icebreaker system includes a novel bow form and employs an unconventional icebreaking technique. The system has been successfully tested in model and demonstrated in full scale with the modified icebreaker “Max Waldeck”. The Melville design uses a conventional form incorporating the latest technology. This paper describes the model tests and discusses the relative performance as indicated by the test results. The investigation has shown the potential for the use of the Thyssen/Waas bow form on icebreaking cargoships such as the “M.V. Arctic”.
The Limits of Flame Propagation Within Homogeneous Streams of Fuel and Air
Authors: Karim G. A. , Wierzba I. , Soriano B.
Published: November 2009

Information about the limits of flame propagation within streams of homogeneous gaseous fuel-air mixtures at atmospheric pressure is presented for both low velocity streams, in the presence of pilot jet flame ignition, as well as for high velocity streams when ignited by an electric spark of adequate and constant energy. In addition to methane, representing natural gas, other gaseous fuels were considered that included hydrogen and propane. The roles of the presence of varying concentration of the diluent gases, nitrogen and carbon dioxide, with the methane and changes in the intensity of turbulence were also investigated.
Performance Characteristics of a Kite-Powered Pump
Authors: Goela J. S. , Vijaykumar R. , Zimmermann R. H.
Published: November 2009

A kite-powered pump which employs a kite to convert wind energy into potential energy of water has been studied to determine its performance characteristics and see if the steady-state operation is feasible. Governing equations describing the motion of the pump in both the ascent and descent modes have been developed assuming that the tether is inflexible and that its profile is a straight line. These equations have been solved numerically to assess how performance parameters of the pump, such as output power, load-carrying capacity and cycle time vary with the pump stroke, kite weight, kite’s lift to drag ratio (CL/CD), initial tether length and tether angle of inclination. Further, conditions for steady-state operation of the pump have been specified. The results show that (i) the maximum power during the ascent is produced when the kite motion is approximately crosswind, (ii) the steady-state cyclic motion of the kite pump is feasible with a net power output, (iii) the average pump power increases at a rate slower than (CL/CD)2 as (CL/CD) increases, and (iv) the pump power peaks with the kite weight.
Particulate Fluidized-Bed Fixtures for Automated Manufacturing
Authors: Thompson B. S. , Gandhi M. V.
Published: November 2009

Flexible manufacturing systems are designed to produce a wide variety of parts with different shapes and sizes. However, the current philosophy of employing dedicated fixtures is expensive, and inefficient, and if these modern manufacturing systems are to be truly flexible, then the fixturing must be flexible also. This paper which reports on an innovative class of flexible fixtures based on particulate fluidized beds, not only presents a mathematical model governing the holding ability of this novel class of fixtured, but also summarizes the results of parametric computer studies.
Damage Detection in Offshore Platforms Using Vibration Information
Authors: Shahrivar F. , Bouwkamp J. G.
Published: November 2009

Damage detection based on changes in dynamic characteristics is considered for eight-legged k-braced steel offshore oil and gas production towers. Both experimental and analytical results are presented to improve damage detection capabilities. A 1/50th scale plastic model representing the structural system of a typical full-scale tower in 218 ft (66m) of water is used for the studies. Effects of severance of diagonal bracing members on selected vibration frequencies and mode shape parameters measurable at the deck are investigated. The effects of changes in deck mass, increase in jacket mass, and deck mass eccentricity on the selected parameters are also investigated and are shown to be different from the effects of damage.
Simulation of Transient Two-Phase Flow in Pipelines
Authors: Sharma Y. , Scoggins M. W. , Shoham O. , Brill J. P.
Published: November 2009

The laws of conservation of mass and linear momentum were applied to a two-phase mixture to formulate a mathematical model which simulates isothermal, transient two-phase flow of gas and liquid in a pipeline. Liquid holdup and friction factors were incorporated via existing empirical correlations, and the black oil method was used to describe interphase mass transfer. Implicit finite difference analogues were derived for the nonlinear set of partial differential equations which constituted the basis of the model. The system of difference equations was solved using a sequential solution algorithm implementing a Newton-Raphson iterative procedure. The numerical model formulated was used to predict the performance of an existing wet gas pipeline to establish the validity of the model. Example simulation runs were used to provide insights into the nature of transient two-phase flow.
Predicting Compositional Two-Phase Flow Behavior in Pipelines
Authors: Furukawa H. , Shoham O. , Brill J. P.
Published: November 2009

A computational algorithm for predicting pressure and temperature profiles for compositional two-phase flow in pipelines has been developed. The algorithm is based on the coupling of the momentum and energy balance equations and the phase behavior of the flowing fluids. Mass transfer between the gas and the liquid phases is treated rigorously through flash calculations, making the algorithm capable of handling retrograde condensation. Temperatures can be predicted by applying the enthalpy balance equation iteratively. However, it was found that the explicit Coutler and Bardon analytical solution for the temperature profile yields nearly identical results for horizontal and near horizontal flow.
Development of a Scale Model for the Dynamic Interaction of a Pile in Clay
Authors: Kana D. D. , Boyce L. , Blaney G. W.
Published: November 2009

Similitude theory is used to develop a scale model for determining the dynamic response properties of a single pile embedded in over-consolidated clay. The basis for the design is a full-scale pile embedded in natural soil, for which dynamic response measurements had been made in previous work. Correlation of the model and prototype results constitutes a major difference in this work over previous efforts using scale models. The model pile material is selected to provide the correctly scaled stiffness and mass properties. The required model soil properties are achieved by developing a mixture of bentonite, aerosil, and veegum. Elastic properties of the model soil are compared with those of the prototype by standard monotonic stress and cyclic stress soil tests. Nonlinearity of the soil stiffness is included in the modeling. Dynamic response of the pile is monitored while excited by impact and swept sine forces at the pile top cap. The results are obtained in terms of time histories for excitation and response at various locations, frequency response functions, natural frequency and mode shapes, and modal damping. Validity of the model is established by comparing the appropriately scaled responses with those of the prototype under similar excitation conditions. It is concluded that the approach should be suitable for measurement of pile/soil dynamic interaction behavior in other types of material and excitation conditions, providing that suitable soil and pile material properties can be selected to allow testing in a one-g environment. Therefore, the scale model approach can be used to verify predictions made by analytical design methods or to provide input parameters for those methods.
Scale-up Technique of Slurry Pipelines—Part 1: Turbulence Modeling
Authors: Roco M. C. , Mahadevan S.
Published: November 2009

A kinetic energy turbulence model is proposed for the flow simulation and scale-up of slurry pipelines (in Part 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 [1]). The mixture kinetic energy and eddy viscosity one-equation turbulence models are compared. The constitutive equations and model constants are tested using laboratory experiments and then employed for large-scale applications. The governing equations are derived from the space/time averaging of the momentum equations and integrated in the pipe cross section using the finite volume approach. The specific interaction stresses (liquid-liquid, liquid-solid, solid-solid and solid-wall) are expressed in the mathematical formulation. The predictions for the velocity and concentration distributions, as well as on the mean velocity-headloss correlations, have been compared to available experimental data (water-sand, water-glass, water-coal mixtures; of concentrations αS = 5 – 40 vol percent, in pipes of various diameters D = 40 – 500 mm). The suggested model can simulate multi-species particulate pipe flow for which the semiempirical methods cannot be satisfactorily applied. The numerical tests and comparison to experiments show the model capabilities to scale-up data from laboratory to real flow situations via infinitesimal two-phase flow analysis.
Linearization Technique for Probabilistic Riser Frequency Domain Analysis
Authors: Ertas A.
Published: November 2009

This paper presents a rigorous derivation of equations for the minimization of the mean-squared error and defines the describing function for different input components. The technique has a direct application to analyze the dynamic response of marine risers. The describing function method will be used to determine the linearization coefficients for the nonlinear drag effects, taking into account a steady current and the random sea waves. The method will have significant impact on other problems such as fixed offshore platforms and tension leg platforms.
Incipient Yielding and Solids Production for Perforated Casing Completions
Authors: Fahrenthold E. P. , Cheatham J. B.
Published: November 2009

Production rate limits for perforated casing completions in weak rock formations are estimated for a material obeying a quadratic yield condition. Plastic stresses around a spherical cavity are calculated to determine the well pressure value which precipitates solids production. Elastic solutions for a cylindrical cavity are utilized to place upper and lower bounds on the well pressure value which initiates yielding around a perforated casing. The separate analyses define consistent critical well pressure values for initial yield and solids production as a function of rock properties and in-situ conditions.
Pressure-Resistant Plane Disk Viewports From Allyl Diglycol Carbonate Plastic for Hyperbaric Chambers
Authors: Stachiw J. D. , Stachiw M. A.
Published: November 2009

Acrylic plastic viewports have been used for over 40 yr in pressure vessels for human occupancy without any catastrophic failure resulting in a loss of life. However, there are special applications, such as for example in hyperbaric chambers for medical purposes, where the susceptibility of flexure stressed acrylic plastic to surface crazing and cracking in the presence of common organic solvents contained in antibacterial sprays is a distinct disadvantage. To solve this problem, a search has been initiated for transparent plastics that are not attacked by organic solvents and can be cast economically in thick sections. Allyl diglycol carbonate plastic appears not only to satisfy the foregoing requirement, but also to provide better resistance to abrasion, pitting, and X-ray or gamma irradiation than acrylic plastic. Short-term, long-term, and cyclic pressure testing has been conducted on over one hundred allyl diglycol carbonate plane disk viewports with t/D0 ratio in the 0.06 to 0.4 range and temperature in the 4°C to + 52°C (+40F to 125°F) range. It appears that plane disks cast from allyl diglycol carbonate plastic can perform safely as pressure-resistant viewports in pressure vessels for human occupancy. It is recommended that for such an application their design temperature be limited to under 52°C (125°F), and that their design pressure at 52°C (125°F) design temperature not exceed 4 percent of their (STCP) short-term critical pressure at 24°C (75°F).
Pipeline Monitoring
Authors: Jamieson R. M. , McDonald J. S.
Published: November 2009

TransCanada PipeLines Limited has established a comprehensive program for in-line inspection of its extensive pipeline system. TransCanada has been developing inspection tools since 1968 and currently has three types of inspection tools capable of detecting corrosion on either the inside pipe surface or both the inside and outside pipe surfaces and/or mechanical damage (e.g., dents). Development of inspection tools continues and is mentioned briefly. A major development thrust is the creation of computer software for the interpretation of inspection data.
An Evaluation Method for Peak/Off-Peak Price Functions in Energy Storage Technologies
Authors: Vadasz P. , Weiner D.
Published: November 2009

A method of evaluation for peak/off-peak price functions in energy storage technologies is presented. The method is particularly useful in statical optimization of the fundamental parameters required for planning energy storage plants. Its application permits to transform the original dynamic optimization problem into a statical equivalent problem, thus reducing considerably the computing time needed. This transformation introduces two additional parameters to be optimized using statical optimization methods, i.e., charging and discharging duration.
Operational Physical Conditions for a Solid-State-Engine (SSE) Applying Shape Memory (SM) Alloy
Authors: Kajamaa J.
Published: November 2009

The physical conditions for a solid-state-engine (SSE) applying shape memory (SM) alloy is treated based on both experimental results and theoretical considerations. First, the mechanical efficiency is derived. It is compared to that of the fuel engine. Then, the energy transformation diagram is drawn. By means of this the overall efficiency of the system is defined. Also it is concluded that this system can store a part of the accepted kinetic energy as a potential energy in a reversible manner.