Second Order Roll Motions for FPSO's Operating in Severe Environmental Conditions

2007 ◽  
Author(s):  
Flavia Caldi Rezende ◽  
Xiao Bo Chen ◽  
Marcos Donato Ferreira
Keyword(s):  
Environmental Conditions ◽  
Second Order

Hydrodynamic Modeling of Large-Diameter Bottom-Fixed Offshore Wind Turbines

2015 ◽  
Author(s):  
Erin E. Bachynski ◽  
Harald Ormberg
Keyword(s):  
Wind Turbines ◽  
Environmental Conditions ◽  
Limit State ◽  
Second Order ◽  
Offshore Wind ◽  
Stokes Wave ◽  
Intermediate Water ◽  
Hydrodynamic Loads ◽  
Offshore Wind Turbines ◽  
Wave Kinematics

For shallow and intermediate water depths, large monopile foundations are considered to be promising with respect to the levelized cost of energy (LCOE) of offshore wind turbines. In order to reduce the LCOE by structural optimization and de-risk the resulting designs, the hydrodynamic loads must be computed efficiently and accurately. Three efficient methods for computing hydrodynamic loads are considered here: Morison’s equation with 1) undisturbed linear wave kinematics or 2) undisturbed second order Stokes wave kinematics, or 3) the MacCamy-Fuchs model, which is able to account for diffraction in short waves. Two reference turbines are considered in a simplified range of environmental conditions. For fatigue limit state calculations, accounting for diffraction effects was found to generally increase the estimated lifetime of the structure, particularly the tower. The importance of diffraction depends on the environmental conditions and the structure. For the case study of the NREL 5 MW design, the effect could be up to 10 % for the tower base and 2 % for the monopile under the mudline. The inclusion of second order wave kinematics did not have a large effect on the fatigue calculations, but had a significant impact on the structural loads in ultimate limit state conditions. For the NREL 5 MW design, a 30 % increase in the maximum bending moment under the mudline could be attributed to the second order wave kinematics; a 7 % increase was seen for the DTU 10 MW design.

scholarly journals The second order axes in the formation of the virginile tree crown of the Ulmus glabra Huds

2021 ◽  
pp. 70-81
Author(s):  
Ирина Сергеевна Антонова ◽  
Мария Сергеевна Телевинова ◽  
Виктор Александрович Барт
Keyword(s):  
Environmental Conditions ◽  
Second Order ◽  
Annual Growth ◽  
Tree Crown ◽  
Accurate Indication ◽  
Ulmus Glabra

Последовательность возрастных этапов дерева отражается ходом роста самых крупных осей 2 порядка формирующихся на годичных приростах ствола. Именно эта последовательность определяет контур кроны виргинильного дерева и его успешность в конкретных экологических условиях. Самая сильная верхняя ветка каждого годичного прироста ствола ходом своего роста отражает тот возрастной этап развития кроны дерева, когда она начала формироваться, являясь своеобразным маркером. Свойства ветвей можно использовать для сравнительной характеристики деревьев в одном возрастном состоянии для более точной индикации внешних условий. The series of the age-stages of the tree is reflected by the growth of the largest axes of the second order formed on the annual growth of the trunk of tree. This series determines the contour of the crown of the virginal tree and its success in specific environmental conditions. The strongest upper branch of each annual growth of the trunk in the course of its growth reflects that age stage in the development of the crown of the tree when it began to form, being some sort of a marker. Branch properties can be used to compare trees in the same age stage for a more accurate indication of external environmental conditions.

Full Scale Measurements and Theoretical Predictions of 2nd Order Pitch and Roll Slow Motions of a Semisubmersible Platform

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Vinicius L. F. Matos ◽  
Eric O. Ribeiro ◽  
Alexandre N. Simos ◽  
Sergio H. Sphaier
Keyword(s):  
Environmental Conditions ◽  
Scale Effects ◽  
Vertical Plane ◽  
Production Capacity ◽  
Slow Motion ◽  
Second Order ◽  
Full Scale ◽  
Wave Basin ◽  
Theoretical Predictions ◽  
Slow Motions

In Oct. 2007, the semisubmersible platform PETROBRAS 52 (P-52) was installed in Campos Basin (Roncador Field) offshore Brazil, in a depth around 1800 m through 16 lines in taut-leg con. The maximum production capacity is 180.000 bpd with a displacement of 80,986t at the operational draft of 27.5 m. Slow drift motions in the vertical plane (heave, roll, and pitch) were observed in a model test performed in a wave basin during the design phase. As resonant responses vary considerably with the damping loads, slow motion could be affected by scale effects. To observe the phenomena, by that time, it was a doubt if this phenomenon would happen during the platform operation. Since June 2008, PETROBRAS has been monitoring P-52 motions with the use of accelerometers and rate-gyros. Through spectral analysis of the measured signals, it was possible to verify the presence of slow motions with frequencies around the natural frequencies of roll and pitch during almost the whole monitoring period. Sometimes, the 2nd order amplitudes were even greater than the 1st order ones. Furthermore, the environmental conditions have also been monitored through wave radars, ADCPS (current) and meteorological stations (wind) in the vicinity of P-52 location, making the excitation loads identification possible. A comparative study confronting full-scale measurements and theoretical predictions was performed. First and second-order forces and responses were calculated using Wamit® second order module. This study permitted the estimation of the full scale damping values of this offshore system (hull plus mooring and riser lines) for one of the environmental conditions measured. The results indicate the importance of considering the resonant roll and pitch motions in the seakeeping analysis of large-volume semisubmersible platforms, contributing with an important feedback to future designs.

2nd Order Pitch and Roll Slow Motions of a Semi-Submersible Platform: Full Scale Measurements and Theoretical Predictions Comparative Study

2010 ◽  
Author(s):  
Vini´cius L. F. Matos ◽  
Eric O. Ribeiro ◽  
Alexandre N. Simos ◽  
Sergio H. Sphaier
Keyword(s):  
Comparative Study ◽  
Environmental Conditions ◽  
Scale Effects ◽  
Vertical Plane ◽  
Production Capacity ◽  
Second Order ◽  
Full Scale ◽  
Wave Basin ◽  
Theoretical Predictions ◽  
Slow Motions

In October 2007, the semi-submersible platform PETROBRAS 52 (P-52) was installed in Campos Basin (Roncador Field) offshore Brazil. This Unit is moored through 16 lines in taut-leg configuration in a water depth around 1.800m. Its displacement at the operational draft (T = 27.5m) is 80.986t. The maximum production capacity is 180.000bpd. During the design phase of this floating system, a model test campaign was performed in a wave basin and slow drift motions in the vertical plane (heave, roll and pitch) were identified. It is known that resonant responses vary considerably with the damping loads. As these loads are affected by scale effects, by that time, it was a doubt if this phenomenon would happen during the platform operation. Since June 2008, PETROBRAS has been monitoring P-52 motions with the use of accelerometers and rate-gyros. Through spectral analysis of the measured signals, it was possible to verify the presence of slow motions with frequencies around the natural frequencies of roll and pitch during almost the whole monitoring period. Sometimes, the 2nd order amplitudes were even grater than the 1st order ones. Furthermore, the environmental conditions have also been monitored through wave radars, ADCPS (current) and meteorological stations (wind) in the vicinity of P-52 location, making the excitation loads identification possible. A comparative study confronting full-scale measurements and theoretical predictions was performed. First and second-order forces and responses were calculated using WAMIT® second order module. This study permitted to estimate the full scale damping values of this offshore system (hull plus mooring and riser lines) for one of the environmental conditions measured. This work demonstrates the importance of considering the resonant roll and pitch motions in the seakeeping analysis of large-volume semi-submersible platforms, contributing with an important feedback to future designs.

Rooting of Jack Pine (Pinusbanksiana Lamb.) Cuttings

1974 ◽  
Vol 4 (4) ◽  
pp. 557-561 ◽  
Author(s):  
L. Zsuffa
Keyword(s):  
Environmental Conditions ◽  
Root Systems ◽  
Jack Pine ◽  
Second Order ◽  
Clonal Variation ◽  
Third Order ◽  
Medium Length ◽  
Old Trees ◽  
Better Than

Cuttings from 6- and 10-year-old trees of jack pine rooted under intermittent mist. Well balanced root systems with many fine side roots were produced.The influence of several factors on rooting was studied. Clonal variation in rooting was observed. In general 6- and 10-year-old ortets rooted similarly. The ortets with heavy, long branches rooted better than the ones with light, short branches. Cuttings taken from second-order shoots rooted and survived like those taken from third-order shoots. Cuttings of medium length rooted and survived best.A high percentage of the cuttings of all clones callused. However, a number of callused cuttings later died, possibly due to unfavorable environmental conditions in the propagation house. Survival was highest for clones rooting best.

Disappearance Voltage Determinations Using a Convergent Beam

1971 ◽  
Vol 29 ◽  
pp. 184-185
Author(s):  
W. L. Bell
Keyword(s):  
Second Order ◽  
Objective Method ◽  
Uniform Thickness ◽  
Rocking Curve ◽  
Crystal Perfection ◽  
Kikuchi Line ◽  
Central Maximum ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Technique

Disappearance voltages for second order reflections can be determined experimentally in a variety of ways. The more subjective methods, such as Kikuchi line disappearance and bend contour imaging, involve comparing a series of diffraction patterns or micrographs taken at intervals throughout the disappearance range and selecting that voltage which gives the strongest disappearance effect. The estimated accuracies of these methods are both to within 10 kV, or about 2-4%, of the true disappearance voltage, which is quite sufficient for using these voltages in further calculations. However, it is the necessity of determining this information by comparisons of exposed plates rather than while operating the microscope that detracts from the immediate usefulness of these methods if there is reason to perform experiments at an unknown disappearance voltage.The convergent beam technique for determining the disappearance voltage has been found to be a highly objective method when it is applicable, i.e. when reasonable crystal perfection exists and an area of uniform thickness can be found. The criterion for determining this voltage is that the central maximum disappear from the rocking curve for the second order spot.

Vibration Isolator System for Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 182-183
Author(s):  
K. Ohi ◽  
M. Mizuno ◽  
T. Kasai ◽  
Y. Ohkura ◽  
K. Mizuno ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Magnetic Fields ◽  
Environmental Conditions ◽  
Vibration Isolator ◽  
Air Conditioners ◽  
Vibration Isolators ◽  
Large Size ◽  
Electron Microscopes

In recent years, with electron microscopes coming into wider use, their installation environments do not necessarily give their performance full play. Their environmental conditions include air-conditioners, magnetic fields, and vibrations. We report a jointly developed entirely new vibration isolator which is effective against the vibrations transmitted from the floor.Conventionally, large-sized vibration isolators which need the digging of a pit have been used. These vibration isolators, however, are large present problems of installation and maintenance because of their large-size.Thus, we intended to make a vibration isolator which1) eliminates the need for changing the installation room2) eliminates the need of maintenance and3) are compact in size and easily installable.

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