J. Energy Resour. Technol. 1985;107(1):1. doi:10.1115/1.3231157.
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Offshore Mechanics and Arctic Engineering

J. Energy Resour. Technol. 1985;107(1):2-11. doi:10.1115/1.3231159.

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.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):12-17. doi:10.1115/1.3231151.

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.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):18-23. doi:10.1115/1.3231156.

Laboratory measurements of the total in-line forces on a fixed vertical 2-in-dia cylinder in deep-water regular and random waves are given and compared with predictions from the Morison equation. Results show, for regular waves with heights ranging from 2 to 22 in. and frequencies ranging from 0.4 to 0.9 Hz that the Morison equation, with Stokes wave theory and constant drag and inertia coefficients of 1.2 and 1.8, respectively, provides good agreement with the measured maximum wave forces. The force variation over the entire wave cycle is also well represented. The linearized Morison equation, with linear wave theory and the same coefficients likewise provides close agreement with the measured rms wave forces for irregular random waves having approximate Bretschneider spectra and significant wave heights from 5 to 14 in. The success of the constant-coefficient approximation is attributed to a decreased dependence of the coefficients on dimensionless flow parameters as a result of the circular particle motions and large kinematic gradients of the deep-water waves.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):24-33. doi:10.1115/1.3231158.

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

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):34-41. doi:10.1115/1.3231160.

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.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):42-47. doi:10.1115/1.3231161.

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.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):48-53. doi:10.1115/1.3231162.

The response of long floating structures to a harmonic excitation is the basis for the response calculation in a short-crested wave field. This paper will present consistent formulas for obtaining the nodal loads in a finite element analysis. The accuracy of the method used is compared with the results obtained using a Rayleigh-Ritz approximation of the response with continuous eigenfunctions. The error of using an irrational finite element model is demonstrated for comparison, and to indicate to designers of similar structures the large effects which they may be overlooking.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):54-59. doi:10.1115/1.3231163.

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.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):60-67. doi:10.1115/1.3231164.

The available data on hot spot stress for tubular welded joints has been reviewed and a database established. Stress analysis techniques in general use for the design of offshore structures and parametric equations have been assessed against this database to determine their accuracy. A set of equations to predict the stress distributions for simple joints has been proposed and has been used to predict mixed mode stress concentration factors. Results obtained from a complex K joint have been examined in detail and the importance of the stress state, when predicting the mixed mode stress concentration factors, is demonstrated.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):68-73. doi:10.1115/1.3231165.

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.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):74-80. doi:10.1115/1.3231166.

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.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):81-86. doi:10.1115/1.3231167.

An oscillating water column (OWC) wave power absorber is one of the most promising devices, as well as the Salter Duck and the Clam. This paper presents a simple prediction method, in which the equivalent floating body approximation is used, for absorbing wave power characteristics of an oscillating water column device. The effects of the compressibility of air and inertia of an air turbine and electric generator on absorbed wave power are obtained by using the equivalent electric circuit concept. Both the experimental and theoretical studies are carried out in this paper.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):87-92. doi:10.1115/1.3231168.

This study describes the application of the techniques of stochastic modeling to random data obtained from the sea trials of the wave energy device Kaimei, and the interpretation of the results in terms of device efficiency. Two models of the power absorption system are developed and the relationships derived between them yield information on the influence of the vessel motions on the absorbed power. The theory of multiple frequency response functions is applied to the data, and it is shown that the motions of the Kaimei have a detrimental effect on its energy absorption capacity and the reasons for this are investigated.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):93-98. doi:10.1115/1.3231169.

Over two hundred unconfined compression tests were performed on vertical ice samples obtained from 10 multi-yr pressure ridges in the Beaufort Sea. The tests were performed on a closed-loop electrohydraulic testing machine at two strain rates (10−5 and 10−3 s−1 ) and two temperatures (−20° and −5°C). This paper summarizes the sample preparation and testing techniques used in the investigation and presents data on the compressive strength and initial tangent modulus of the ice.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):99-102. doi:10.1115/1.3231170.

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.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Ocean Engineering

J. Energy Resour. Technol. 1985;107(1):103-106. doi:10.1115/1.3231146.

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.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):107-112. doi:10.1115/1.3231147.

Spiral ropes of high load-bearing capacity are usually made of cold-drawn steel wires of high tensile strength. This material has been investigated by many researchers, not only to determine the mechanical properties of cold-drawn wires, but also to find out more about their stress-strain behavior under tensile loading and local three-dimensional stresses. It is now possible to determine load ranges for fatigue as a function of: surface conditions of the wire; the length of the wire; the diameter of the wire; local stresses resulting from damage to the wire surface; local stresses resulting from transverse pressure at points of contact where wires cross; friction between the wires produced by changes in stress; friction between the wires produced by changes in cable curvature; friction between wires and fittings or anchorage structures. Cables can be protected from corrosion due to environmental influences. If this is done the fatigue behavior of a twisted cable primarily depends on the addition of friction energy given to the material where strong contact forces cause three-dimensional stresses. A method of determining the fatigue strength of tension members made of cold-drawn wires is described using statistical methods, results of fatigue tests on short specimens, and precision measurements of the cold-drawn wire. It is possible to reach the material dependent fatigue limit of about 300 N/mm2 with a spiral rope by a welldone structural design and corrosion protection.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Emerging Energy Technology

J. Energy Resour. Technol. 1985;107(1):113-121. doi:10.1115/1.3231148.

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.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Rock Mechanics/Drilling Mechanics

J. Energy Resour. Technol. 1985;107(1):122-127. doi:10.1115/1.3231149.

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.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):128-134. doi:10.1115/1.3231150.

The nonlinear response and eventual collapse of an initially imperfect cross section of a cylinder of infinite length is analyzed. The cylinder is loaded by external pressure and axial load and is intended to model oil well casing in a service environment. Results from the analysis agree well with experimental data and provide an interesting alternative to current empirical/statistical methods for determining the minimum collapse resistance of casing for use in design calculations.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):135-137. doi:10.1115/1.3231152.

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.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1985;107(1):138-141. doi:10.1115/1.3231153.

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.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Petroleum Fluid Mechanics

J. Energy Resour. Technol. 1985;107(1):142-151. doi:10.1115/1.3231154.

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.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Solid Waste Processing

J. Energy Resour. Technol. 1985;107(1):152-162. doi:10.1115/1.3231155.

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.

Commentary by Dr. Valentin Fuster

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