bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wind Tunnel Hydrodynamic Testing Of A Large Submersible Vehicle Model
Authors: Van Ryzin Joseph C. 
Published: October 2008

ABSTRACT
During the development of a large (270 ton) underwater remote-controlled vehicle, it became essential for the control design that tests be conducted to determine the steady state hydrodynamic drag characteristics of the submerged vehicle. Such a large complex shape is difficult, if not impossible, to model with the correct Reynolds number in water because of the huge drag and power requirements. Testing of this vehicle was done in a wind tunnel with almost exact Reynolds number correlation. Air can be used for testing of underwater vehicles as long as the fluid is reasonably incompressible (low speeds), there is no free surface and no cavitation; it is also advantageous if the flow is not critical.
If the model is sized to conveniently fit into the wind tunnel test section, the required air velocity to reach the appropriate Reynolds number is within the approximate incompressible range (approximately 330 ft/sec) and the test forces are within the test facility balance range, then the vehicle can be conveniently tested in a wind tunnel.
This particular vehicle was tested at various roll, yaw and pitch angles to evaluate six-component forces and moments. Reynolds number effects, support tare and vehicle configuration changes were studied. The results of the test provided invaluable information for an accurate evaluation of the vehicle maneuverability and handling characteristics. Larger than expected roll moments and lift forces were encountered and compensating vehicle control design changes were made.
In conclusion, wind tunnels offer an excellent alternative and, in many cases, a better alternative than testing the vehicle in water or relying solely on an analytical solution.

INTRODUCTION
The 270 ton aluminum Submersible Pipeline Repair Vehicle (SPRV) is a twin hulled, variable ballast submersible with 9-foot diameter hulls, 156 feet long, four bridge beams of syntactic foam and aluminum, six 8-foot diameter Kort nozzle thrusters, and various tooling and electronics. This vehicle is being developed for Shell Development Company. A floating model of the vehicle is shown in Figure 1. The purpose of the SPRV is to repair deepwater pipelines. It is remote controlled via an umbilical from the surface.
The SPRV is designed to operate in a 1.5 knot bottom current and, since it docks parallel to the pipeline, it must be able to hover at any orientation (yaw angle) to this current. For proper design of the control, maneuverability, placement of the thrusters and thruster power requirements, the loads caused by the 1.5 knot current had to be known. There are six load components of concern: frontal drag, thwartship drag, lift, yawing moment, pitching moment and rolling moment.
Parametrization And Preprocessing Of Ocean Color Image Data For Studies Of Coastal Oceanography
Authors: Mueller James L. , Ball David L. , Middleton Elizabeth M. 
Published: October 2008

ABSTRACT
Methods are presented for processing ocean color image data into forms suitable for quantitative oceanographic studies. A radiative transfer technique is outlined for determining approximate corrections for atmospheric transmission. atmospheric path radiance. sun glitter. and skylight reflection from the sea surface as functions of scan angle. The radiometric accuracy of these corrections is perhaps no better than ± 20%. but they nevertheless serve to make an overall relative correction for the systematic scan-angle dependent radiance variations with which these effects badly mask the ocean color pattern in images. Further processing methods include removal of geometric scan distortions from each image. and geographic registration (accurate to 0.5 km. or a single pixel) using 'visible landmarks. Work in progress to account for effects of bottom reflectance in ocean color spectrum analyses is reviewed. Experimental results with ocean color spectra from different world locations suggest that it may be possible to standardize the parametrization of ocean color spectra with characteristic vectors.

INTRODUCTION
Ocean color images obtained from space with scanning radiometers have several potential uses for studying and monitoring oceanic phenomena. Some oft-cited examples include making maps of sediment transport in estuaries and river plumes. monitoring the dispersal of water pollutants. making maps of phytoplankton (chlorophyll) distributions in coastal waters. watching for "red tide" outbreaks. and tracking the drift of dredge-spoil from offshore mining sites.
The utility of ocean color imagery has been partially realized with LANDSAT Multi-Spectral Scanner (MSS) data. even though the MSS was not designed for water color measurements (its radiometric gains are too low and its spectral bandwidths are too wide). Better ocean color image data will become available in 1978. when the Coastal Zone Color Scanner (CZCS) flies on the Nimbus-G satellite. The CZCS will have four narrow-band channels between 400 and 700 nm, a broad-band channel in the 7001100 nm region, and a thermal infrared channel in the 10–12 µm atmospheric window. Radiometric gains on CZCS will resolve the low radiance levels emanating from the sea and will saturate over most land scenes. Finally, Nimbus/CZCS coverage of a given scene will be repeated approximately every 36 hours. compared to 18 days for LANDSAT/MSS. In order to simulate CZCS data for algorithm and software development and for pre-launch experiments. a 10channel ocean color scanner (OCS) is currently operated aboard a NASA U-2 aircraft.
Multispectral radiometric ocean color measurements with. e.g. the OCS. are multidimensional data. and therefore. somewhat awkward to handle, display and interpret.
Design Of Floating Concrete Platform For Deep Water Oil Production
Authors: Kure Gregers , Hjertas Bjørn 
Published: October 2008

ABSTRACT
The paper describes a concrete platform design, Conprod, intended for use as floating production platform in hostile areas such as the North Sea, the North Atlantic and the Gulf of Alaska. The Conprod platform is composed of the same structural elements as the Condeep gravity platform.
Theoretical calculations of platform response in irregular waves are described. The system of structure, mooring lines, added mass and hydrodynamic damping is represented by a finite element model, suitable for solution in the frequency domaine. The springs and forces are assumed to have linear characteristics.
Model tests are performed at a scale of 1:60. Some preliminary results are presented and compared with the theoretical calculations.
A twelve leg spread mooring system is proposed. The mooring lines are composed of chain, clump weights and wire rope. Restoring force and peak tension for the proposed system are compared with a conventional chain system.
For the floating production facility are briefly discussed. A total construction period of 2 years is feasible.

INTRODUCTION
Rapidly increasing development costs, particularly in the North Sea, have initiated an increasing interest in alternative techniques for offshore oil production. In many respects the concept of using a floating platform seems to be highly promising. Some of the features related to this type of field development are:reduced time lag from discovery to first productionreduced early capital investmentscapability to operate in very deep watermobility, the floating facility can be moved from one location and installed at anotherflexibility, the production facility can be utilized for extensive reservoir testingfeasible for oil production in earthquake areas. In June, 1975, the first floating production facility was brought on stream on the Argyll Field in the North Sea by Hamilton Brothers Oil Co. The operational experience during the first year seems to prove the viability of this semi-permanent production system.
A complete production system utilizing a floating platform comprises:a number of subsea completed wells with flowlines to a riser basea production riser through which oil flows from the riser base to the floating production platforma floating production platform with production equipmenta system for transfering the produced oil to shore, normally an offshore loading system. A number of different concepts for a floating production platform have been proposed during the last years, one of which is the Conprod described in this paper. The Conprod platform is structurally based on the same ideas as the Condeep gravity platform.

DESIGN PHILOSOPHY
The base for the Conprod design has been to utilize high quality concrete to create a floating platform capable of operating in water depths from 120 m to 500 m. The Conprod concept is feasible for world wide operation and can be constructed and equipped in any deep water harbour.
Analysis Of Driving Of Foundation Piles
Authors: Faa Stephen H.C. , Matlock Hudson H.C. , Meyer Patrick L. 
Published: October 2008

Abstract
A computer method has been developed to analyze the driving of foundation piles by impact and vibration, with the hammer acting at any point along the pile. A mandrel or follower may be included in the analysis.
While retaining the discrete-element concept proposed by E. A. L. Smith, the method employs an implicit (Crank-Nicolson) type of numerical solution. Soil supports may be any desired nonlinear functions of pile displacement history. Degradation in ultimate soil resistance under the action of inelastic rebound and reload of the pile may also be introduced.

Introduction
The analysis of pile driving requires some method of modelling, or simulation, of the hammer, the pile, and the supporting soil. The dynamic interaction in the system includes the elements of hammer impact, wave propagation along the length of the pile, and soil resistance associated with movement of the pile.
Methods of dynamic pile driving analysis most commonly used in practice are based on work by E. A. L. Smith (Ref 1). Smith utilized the advent of the digital computer to perform a one-dimensional computer simulation of the behavior of the system consisting of the hammer, the pile, and the soil. This method has become widely known as the "wave equation" analysis.
The name is somewhat misleading because this analysis is a discrete-element mechanical analogy of pile driving which does not directly employ the conventional mathematical equation for one-dimensional wave propagation within the solution process.
The pile driving problem requires numerical flexibility to handle varied boundary conditions, soil restraint forces, and non-uniform cross-sections which cannot be accommodated with the use of closed form mathematics. A more appropriate method of analysis is a numerical discrete-element solution such as Smith proposed. However, there has been some concern expressed recently about the accuracy of driveability analysis (Ref 2).
Discrete-element concept, the present method employs an implicit (Crank-Nicolson) type of numerical solution to yield the desired computational accuracy, stability and reliability.
There has been an increasing demand in the industry recently for a rational pile driving analysis to include a more flexible driving system. In the present method of analysis, the hammer can act anywhere along the pile, and a mandrel or follower may be included in the analysis. In order to account for forces other than those from the direct impact of the hammer system, a force-time relationship can be prescribed by the user at any desired point along the pile.
The soil supports are not limited to an approximate, simple elasto-plastic shape. They can be any nonlinear function of the pile displacement history, to reflect the actual soil response along the pile. The system is allowed to rebound and reload inelastically. A degradation in the ultimate soil resistance under the action of this rebound and reloading may also be included.
Dynamic Ice-Water-Soil-Structure Interaction Of Offshore Timers Including Nonlinear Soil Behavior
Authors: Haldar A.K. , Swamidas A.S.J. , Reddy D.V. , Arockiasamy M.K. 
Published: October 2008

ABSTRACT
This paper describes the dynamic analysis procedures, both deterministic and stochastic, for predicting he dynamic response of offshore tower - foundation systems to ice-forces. Representing the hydrodynamic interaction by the added water mass concept, the foundation - structure interaction is investigated using i) a lumped parameter (also called half space continuum and soil springs) model, and ii) a plane strain finite element model. The nonlinear soil characteristics are treated in terms of displacement and strain dependency along the depth of the foundation. The ice force records are generated artifically from sample records. The force input is specified in three different ways:Time history records,Response spectra, andPower spectral density functions.
Rationalisation of the existing design requirements is based on the numerical results obtained.

1. INTRODUCTION
The most serious problem which occurs due to the ice floe movements in an offshore site is the oscillatory or ratcheting type of ice failure which imposes Forced vibrations on the structure. Matlock et al (1) First analysed a cantilever pier, idealised as a damped, single-degree-of-freedom system subjected to a postulated saw-tooth type of deterministic loading.
Reddy and others [2, 3, 4, 5, 6, 7] carried out extensive studies on the response of framed and monopod offshore towers to ice forces. The responses were determined using response spectrum and power-spectral density methods. Procedures for developing artificial ice force records, based on the measured values of Blenkarn [9] at Cook Inlet, were formulated. The influence of the nonlinearity on the soil foundation of the tower responses was examined by Haldar [8].
The purpose of this paper is to describe the different types of modeling criteria for soil-structural interaction behavior of offshore towers. Two types of towers are investigated:A pile-supported three-dimensional tubular space frame with a platform - Fig. l(a).Model of a circular cylindrical steel tower supported by a large circular base or hull treated as a gravity type monopod platform.- Fig. 2.

2. MODELING OF THE STRUCTURAL-FOUNDATION SYSTEM

2.1 Structural Idealization

2.1.1 Framed Tower:
The tower-pile-soil-water system is roughly similar to that analysed statically by Feibush and Keith (10). The members are assumed to be rigidly connected and the added water mass b assumed equal to the mass of the water displaced. The structural modeling is based on a two-dimensional representation of the tower assuming a constant dimension equal to the base length perpendicular to the plane. The masses per unit length of the members in the plane of the frame are computed by summing up the structural mass, the mass of the water contained in the tube, and the displaced water mass. The masses of the members perpendicular to the plane are assumed to be lumped at the horizontal cross brace level joints.
Super-Sized Semisubmersible Performance In The North Sea
Authors: Kobus L.C.S. , Meyers H.M. , Haines S.W. 
Published: October 2008

ABSTRACT
The super-sized 30,000 ton displacement ZAPATA UGLAND has been drilling in the North Sea since. August 1974. This paper summarizes the experienced weather, the associated rig motions and the drilling performance in its operations in the North Sea. This paper highlights the design, equipment and operational aspects of the ZAPATA UGLAND that have been key factors in its splendid performance in the North Sea. A discussion is presented of model test data and the experienced motions and performance. This repot concludes that (1) super-sized semi submersibles, such as the ZAPATA UGLAND, are the optimum type of unit to use in year around operations in deeper waters of the North Sea and (2) self propulsion for a semi submersible is operationally effective and reliable.

INTRODUCTION
As the offshore industry extended into deeper waters of the North Sea and other severe environmental offshore regions, a new class of super-sized semi submersibles were designed, developed, constructed and put into operations. The criteria for classing a semi submersible as "super-sized" is based upon its operating displacement exceeding the working displacement of the pioneering Mohole platform the prototype and forerunner design for all twin-hull semi submersibles.
In 1969, Zapata initiated design studies to determine the optimum characteristics and carrying capacities for a super class design of semi-submersible drilling units. After initial studies of existing and proposed designs were compared with the trend of industry requirements, Zapata developed design parameters for a new unit.
These included the following key features:Ability to continue operations in seas of up to 40 to 50 feetAbility to remain moored in seas of up to 100 feetVariable deck load capacity of 3,000 tonsLoad capacity enabling all movements to be made with anchors and anchor chains stowed aboard the vesselSelf-propelled, with a target speed of 9 knots in calm waterMooring system for 1000 to 1500 ft. maximum range of water depths.
A detailed study of designs tested by Bethlehem Steel at the Netherlands Ship Model Basin indicated one of its designs was highly suitable for further development according to Zapata's target objectives. In 1971, Zapata initiated a joint program with Bethlehem to modify the design for the parameters Zapata had selected. This program included designing the structure, selection of the lower hull form, model tank tests of the new design and strength analyses concurrently with selection of the optimum drilling and auxiliary equipment.

DEVELOPMENT PROGRAM
The resulting design consisted of catamaran lower hulls with six stability columns supporting a water-tight upper hull. The lower hulls were given a sea-barge configuration with faired bows to provide optimum heave dampening action and propulsion characteristics. The trim upper hull was designed with clear lines, minimizing the amount of machinery and storage located on the upper deck exposed to the elements.
A Single Anchor Leg Mooring System For The North Sea
Authors: Foolen J. , Pincemin M. , Smulders L. 
Published: October 2008

I. INTRODUCTION
In 1974 SBM, Inc. designed and built a SALM for the Pulai Field in the South China Sea, where the water depth is 245 feet. The terminal was designed to serve a permanent storage tanker of 190,000 DWT, which will remain moored in the 100 year storm with a significant wave height of 23.5 feet. At that time only two SALMs were installed (Okinawa and Brega). The third one was to be installed at Tembungo, also in the South China Sea. All three were of the base-(riser)-chain-buoy type. (Fig. 1) Extensive model tests were conducted for Pulai at the Netherlands Ship Model Basin in Holland. The test showed that a riser-sparbuoy SALM, in which the chain between riser and buoy is eliminated, has more desireable motion characteristics. In addition lower mooring forces were measured. (Fig. 2).
The knowledge obtained from designing and building the Pulai BALM was used to start the study, model tests and design of a riser-sparbuoy SALM for 533 feet water depth, to be installed at the Thistle Field in the North Sea. The terminal will serve 80,000 DWT tankers in wave heights of 15' significant. Survival conditions are 100 foot waves and 100 knot winds. In this paper the theoretical background, as well as construction of this SALM will be discussed. (Fig. 3).

II. THEORETICAL BACKGROUND
For the design of an offshore terminal the mooring force is one of the main design criteria. However, in the severe conditions of the North Sea, the forces acting on the structure during survival are as important. The Thistle study and model tests showed that motions of the SALM, induced by the wave action are of extreme importance. It was shown by computer simulations and confirmed by model tests that correctly chosen dimensions and weight distributions on riser and buoy reduce the bending moments in the riser. Slightly different buoy dimensions and weight distributions will increase the bending moments occuring in an otherwise identical riser. Moreover, the mooring force level can be reduced significantly by applying the following theory.
The basic reason for the motion and force phenomena are the wave period and the energy level of the waves. The wave period can vary between 5 and 20 seconds. Energy levels of waves below 5 and above 16 seconds are so low that they may be overlooked. In the wave spectrum for which a SALM is designed, two frequency levels are of importance. From vibration theories it is known that a single column like the riser can vibrate in its own natural frequency, known as the beam frequency. On the other hand, the combination riser-buoy has its pendulum frequencies. Any of the frequencies can be of the same order of magnitude of the frequency of the high energy level waves, if the dimensions and weight distributions are not correctly chosen. Resulting resonance would put severe strains on the system as a whole.
Natural Backfilling Of Pipeline Trenches
Authors: Mortensen Preben , Fredsoe Jorgen 
Published: October 2008

ABSTRACT
Sea pipelines are for various reasons frequently laid in trenches in the seabed rather than on the seabed itself. In certain areas it is requested, for security reasons, that the pipeline should be covered to a certain extent, either through natural backfilling or through artificial backfilling. For the planning of the pipeline protection, it is therefore important to be able to calculate the rate of natural backfilling. The present paper describes how the natural backfilling may be calculated on the basis of the following parameters: currents, waves, bed material, shape of trench and water depth. The backfilling (sedimentation) in the trench is partly caused by a gravity effect on the bed load transport and partly by settling of the suspended load due to decreasing transport capacity over the trench. The physics behind these two sedimentation mechanisms are described. A theoretical calculation of the sedimentation, due to gravity effects on the bed load transport is developed in two steps. The first step contains only current, crossing the trench at an arbitrary angle. In the second step, it is shown how the same solution may be applied to bed load transport caused by wave action. The sedimentation due to settling of suspended load is also calculated for currents alone and for combined currents and waves. From the developed mathematical model, it is possible to calculate which portion of the suspended load will be able to settle as the current passes the trench. Four examples of how to calculate natural backfilling are presented. Two examples in current only and two examples in combined currents and waves.

INTRODUCTION
The aim of the studies presented in the present paper has been to provide mathematical models for calculation of natural backfilling in pipeline trenches under the assumption that the sea bed consists of non-cohesive sediments and that the depth of the trench is small compared to the water depth, see Fig. 1. The local scour around the pipeline is not considered in the present paper. The transportation of non-cohesive sediment is normally separated into the transportation of bed load and suspended load. In many contexts, such a distinction is of minor importance, but for the present purpose it will be demonstrated that such a distinction is necessary. As an illustrative example, the especially simple case where the alignment of the dredged trench is parallel to the direction of the current is considered. In this case, no suspended sediment is carried from the undredged regions to the trench by the current, if secondary currents are neglected. As long as the variations in water depth are small, the magnitude of secondary currents is negligible. However, while the suspended load is carried in the current direction, the direction of the transport of bed load deviates from the current direction due to gravity effect on the bed load moving on the slopes of the dredged trench.