J. Energy Resour. Technol. 1982;104(3):193-198. doi:10.1115/1.3230402.

This paper deals with the use of finite element analysis of the creep deformation of ice covers subject to localized loads. An incremental deformation approach was adopted and better computational efficiency and stability were achieved with the selection of proper integration schemes for the constitutive equation. A numerical example is included to illustrate the usefullness of the present method. This case deals with the “sinking” of a heavy pipe into the surface of an ice cover, a situation which is analogous to the stability of heavy structures and equipment resting on frozen foundations in the cold region engineering operations. Close agreement between the analytical and experimental results were obtained.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):199-204. doi:10.1115/1.3230403.

Experimental studies on frost and ice growth under simulated summer conditions were performed on a 3.0-m (10-ft) model of an air convection pile. The air convection pile is a thermosyphon-type permafrost protection device which has been considered for use in arctic construction projects. The device consists of an outer tube, usually 45.75 cm (18 in.) in diameter, extending 3.05 to 18.3 m (10 to 60 ft) into the permafrost. This outer tube contains a shorter concentric 25.4-cm- (10-in.) dia inner tube. Data was taken for typical arctic temperatures and humidities and for simulated above-ground heights of 0.153, 1.373, and 2.88 m (0.5, 4.5, and 7.5 ft). The results have shown that the ice growth is governed by the concentration gradient in the annulus of the pile.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):205-210. doi:10.1115/1.3230404.

Velocity and temperature profiles were measured in a prototype air thermosyphon permafrost protection device. This device, known as the air convection pile, consists of an 18-in. (0.46-m) outer tube containing a shorter concentric 10-in. (0.25-m) tube extending from 10 to 60 ft (3 to 18 m) into the permafrost. Measurements showed a low frequency oscillating flow in both the annulus and inner tube. Heat removal rates compared favorable with an analytical model and previous experimental results, but the annulus velocity profiles were significantly different, possibly due to the oscillation in the flow.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):211-216. doi:10.1115/1.3230405.

A thick-walled circular cylinder, made of either isotropic or composite material, is analyzed using closed-form solutions to two different theories. The cylinder is submerged, so that the loading includes gravity body forces, external hydrostatic pressure at the outer boundary, and a physically realistic distribution of counterbuoyancy force at the inner boundary. The elasticity theory is formulated as one in plane strain using the Airy stress function. The shell theory used is a refined thick shell theory formulated in terms of generalized displacements.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):217-223. doi:10.1115/1.3230406.

Conventional analysis of tension leg platform structures yields natural frequencies which are well separated from wave excitation frequencies. However, the results presented here show that the tethers can have lateral resonant frequencies in the wave frequency range if the platform is deployed in deep water. Analysis which ignores the lateral tether dynamics gives reasonable estimates of platform motions but can seriously underestimate tether displacements. It is usually assumed that tether tension does not vary with time. However, the vertical waves forces, reacted by the tethers, cause the tension to change with time and this can cause a Mathieu type of instability in the platform sway motion. This phenomenon is investigated using a simple energy balance technique and it is shown that square law fluid damping places an upper bound on oscillation amplitude; it is found that platform sway motions due to Mathieu excitation remain acceptable even in large waves.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):224-228. doi:10.1115/1.3230407.

A marine riser pup joint was instrumented to measure riser tension, bending moment, and mud temperature and pressure. The ground rules for the design, major design decisions, significant details, and calibration and testing are discussed.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):229-234. doi:10.1115/1.3230408.

A joint development program has produced a unique flowline swivel for high-pressure natural gas service under continuous, small degree rotation, oscillating service. The swivel uses an elastomeric bearing element made up of alternate, frusto-conical shaped rings of metal and rubber (elastomer) to absorb continuous small degree rotary oscillations or flexures of the swivel. It accommodates larger oscillations, including complete 360-deg rotations, by locking the elastomeric element at its maximum design flexure capability and permitting the entire shaft assembly to rotate relative to the housing. A 6-in. (152.4-mm), 6000-psig (41,370-kPa) prototype successfully passed a rigorous qualification test program. The swivel should be useful in offshore marine production riser systems and loading terminals.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):235-240. doi:10.1115/1.3230409.

The influence that factors such as mooring line conditions, fender arrangements, dolphin arrangements, degree of ship loading, waves of long period, wave direction, and wind on the impact energy of a moored tanker were studied. Based on systematic test data, a semi-empirical formula was developed to calculate the impact energy of the moored ship on the berthing facilities under the action of regular waves. It was shown by experiment that this method is suitable for calculating the impact energy of moored ships of capacities as great as 200 × 103 t.

Topics: Waves , Mooring , Tankers , Ships , Wind
Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):241-246. doi:10.1115/1.3230410.
Topics: Oceans , Seas
Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):247-256. doi:10.1115/1.3230411.

In a previous paper by the authors [1] a procedure is given for the optimum design of single mass, anchored wave energy generators. The anchoring problem is generally regarded as one of the major obstacles of developing practical systems due to the high cost of implementation. This paper presents a procedure for the design of supporting platforms for wave generators which are essentially self-positioned and require minimum anchoring. The optimum design and control for such systems is given for a selected ocean condition. The study shows that an unanchored platform in an optimally designed two-mass system can provide appropriate support for the wave generator without any significant loss of conversion efficiency.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):257-258. doi:10.1115/1.3230412.

The ability to predict earthquakes and tsunamis is becoming increasingly important as world population continues to grow in high-density coastal metropolitan areas. Earthquakes which occur in and near undersea subduction zones where the earth’s crust slides under continental masses generate highly destructive tsunamis. Deep ocean buoy systems and sensor implantation techniques are being developed to obtain seismic data from the earth’s crust in water depths of 6000 m. For the first time, deep-sea drilling, high-resolution seismic sensors, and long-term, deep-ocean mooring technology are being combined to provide systems which continuously monitor earthquake activity in the deep ocean. Such systems provide vital seismic research information to the scientific community.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):259-268. doi:10.1115/1.3230413.

The performance of a rotor-filter pump has been studied experimentally. To develop an understanding of pump performance, and in particular to discern the mechanism of hydraulic pulsing, flow visualization in the rotor, vibration analyses of the pump, frequency analysis of the pump hydraulic pressure pulsation, and analyses of flow characteristics for different pick-up tubes in combination with different impellers and cover plates were conducted. The frequencies of the pump’s hydraulic pulsation is shown to be a function of the number of pick-up arms and the motor speed. The pump vibration and its pulsation amplitude were reduced by increasing the number of pick-up arms or by adding a radial impeller. These actions increased the lowest frequency of pulsation and decreased the chance of excitation of the pump system parts.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):269-273. doi:10.1115/1.3230414.

Performance data for single-stage, radial inflow, expansion turbines is presented in a manner to enable the process designer to quickly estimate the amount of power available from a process stream, the maximum effective pressure ratio and the temperature drop. All data presented is based on the current state of the art and recognizes the different levels of technology which may be applied.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):274-276. doi:10.1115/1.3230415.

In a hydraulic air compressor the air is surrounded by water during the compression process which is virtually isothermal. Depending on the state of the inlet air, the compressor water temperature, and the compression ratio, the compressed air may have higher or lower absolute humidity than that of the inlet air. Relationships between the two humidities are developed and criteria for “drying” to occur are presented.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1982;104(3):277-283. doi:10.1115/1.3230416.

This study deals with investigating the feasibility of an underwater glider capable of carrying cargo for long distances by alternately employing gravity and buoyancy forces for forward propulsion. The parameters controlling the vessel design, stability and control are investigated.

Commentary by Dr. Valentin Fuster

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