DNV GL

About: DNV GL is a company organization based out in Sandvika, Norway. It is known for research contribution in the topics: Corrosion & Finite element method. The organization has 1929 authors who have published 2387 publications receiving 34644 citations.

The application of the SPAR-H method in managed-pressure drilling operations

Abstract: This paper aims to share insights gained in the application of the Standardized Plant Analysis Risk-Human Reliability Analysis (SPAR-H) technique applied to a normal-operations scenario for a managed pressure drilling concept. SPAR-H was used to identify the potential for error for each individual task related to the concept. A Systematic Human Error and Prediction Approach (SHERPA) was performed to gain more insight into the qualitative aspects of the operation including the potential consequences for safety should a task be performed erroneously. For this project, the relative Human Error Probabilities (HEP) values of SPAR-H were used rather than HEPs as absolute performance indicators. With this approach, an evaluation of the concept was performed in terms of its potential for human error and a prioritized set of improvements for the concept was presented. Such application of SPAR-H was found to be a useful approach to aiding project managers in directing focus towards those issues that require most at...

A coupled ice-ocean model of ice breakup and banding in the marginal ice zone

Abstract: A coupled ice-ocean numerical model for the marginal ice zone is considered. The model consists of a nonlinear sea ice model and a two-layer (reduced gravity) ocean model. The dependence of the upwelling response on wind stress direction is discussed. The results confirm earlier analytical work. It is shown that there exist directions for which there is no upwelling, while other directions give maximum upwelling in terms of the volume of uplifted water. The ice and ocean is coupled directly through the stress at the ice-ocean interface. An interesting consequence of the coupling is found in cases when the ice edge is almost stationary. In these cases the ice tends to break up a few tenths of kilometers inside of the ice edge.

Effect of Whipping on Fatigue and Extreme Loading of a 13000TEU Container Vessel in Bow Quartering Seas Based on Model Tests

Abstract: Many large and ultra large container vessels have entered operation lately and more vessels will enter operation in the coming years. The operational experience is limited and one of the concerns is the additional effect of hull girder vibrations especially from whipping (bow impacts), but also from springing (resonance). Whipping contributes both to increased fatigue and extreme loading, while springing does mainly contribute to increased fatigue loading. MAIB recommended the industry to join forces to investigate the effect of whipping after MSC Napoli, a Post-Panamax container vessel, broke in two in January 2007. This has been followed up by a JIP initiated in 2008 with the following participants: HHI, DNV, BV, CeSOS and Marintek. In 2009 a new design 13000TEU vessel was tested in head seas and reported in [1]. The current paper deals with fatigue and extreme loading of the same vessel, but from realistic quartering sea conditions tested in 2010. Different headings and the effect of wave energy spreading have been investigated and compared to results from head seas. Further, the effect of the vibrations have been investigated on torsion and horizontal bending, as the model is also allowed to vibrate with realistic frequencies in other modes in addition to vertical bending. The findings suggest that changing the course is not effective to reduce the fatigue loading of critical fatigue sensitive details amidships. The effect of wave energy spreading did also not reduce the fatigue loading significantly. For the highest observed vertical bending moments in each sea state and for the three cross sections the wave energy spreading in average reduced the maxima, but for the highest sea state the effect of wave spreading did not consistently give reduced maxima. This is an important aspect when considering the available safety margin that may be reduced by whipping. The whipping gave also a considerable contribution to horizontal bending and torsion. This suggests that validation of numerical tools is urgent with respect to off head sea conditions and that these tools must incorporate the real structural behavior to confirm the importance of the response from torsional and horizontal as well as for vertical vibrations.Copyright © 2011 by ASME

Effect of foundation type and modelling on dynamic response and fatigue of offshore wind turbines

Abstract: Correspondence Amir M. Kaynia, Norwegian University of Science and Technology (NTNU), Trondheim, Norway. Email:amir.kaynia@ntnu.no Abstract This paper presents dynamic response and fatigue analyses of several bottom-mounted offshore wind turbine (OWT) models, simulated in the aero-hydro-servo-elastic simulation tool FAST. The distinction between the models is the foundations, which are modelled with different methods, concepts, and dimensions. The US National Renewable Energy Laboratory has developed a 5-MW reference turbine supported on a monopile, the NREL 5MW, which was used as a reference model in this paper. The paper presents the implementation and comparison of two different foundation modeling methods, referred to as the simplified apparent fixity method and the improved apparent fixity method. Furthermore, sensitivity analyses of different monopile dimensions were performed, followed by sensitivity analyses of suction caisson foundations of different dimensions. The final part of the paper presents fatigue analyses for the foundation models considered in this study subjected to 17 load cases. Fatigue damage, fatigue life, and damage equivalent loads were calculated, as well as the relative fatigue contribution from each load case.

Detonations and vapor cloud explosions: Why it matters

Abstract: The methods used to evaluate the consequences of a vapor cloud explosion assume deflagrations within congested process pipework regions and consequently a significant effort has been invested in developing models to estimate the severity of these deflagrations. Models range from the simpler screening approaches to detailed Computational Fluid Dynamics. There is clear evidence from large scale experiments and incidents that transition from deflagration to detonation is credible and has occurred and it is the contention of this paper that deflagration is only the first stage in many major vapor cloud explosions and that detonation is readily foreseeable. Why does this matter? The methods currently used in the design and location of buildings on and around process sites are based on an incomplete picture of vapor cloud explosions. Whilst this might not have a significant effect in some cases, it is shown that there is the potential to significantly underestimate the explosion hazard. This will result in occupied buildings either being placed in the wrong location or under-designed for the explosion threat, increasing the risks to personnel on these sites.