Ole Andreas Hermundstad

Bio: Ole Andreas Hermundstad is an academic researcher from SINTEF. The author has contributed to research in topics: Slamming & Serviceability (structure). The author has an hindex of 3, co-authored 7 publications receiving 232 citations.

Linear hydroelastic analysis of high-speed catamarans and monohulls

Abstract: A linear method for hydroelastic analysis of high-speed vessels is presented. It is based on a modal approach and represents a generalization of the high-speed strip theory of Faltinsen & Zhao (1991a). Hydrodynamic interaction between the hulls of catamarans is properly accounted for by utilizing symmetry. It is demonstrated how an integral theorem can be utilized to find the hydrodynamic force for general mode shapes. Theoretical predictions of ship motions and sectional forces and moments are compared with experimental data for a flexible high-speed catamaran model in regular waves. The influences of hull interaction and the application of the integral theorem are demonstrated.

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

ISSC Committee II.2 – Dynamic Response

Abstract: Concern for the dynamic structural response of ships and offshore structures as required for safety and serviceability assessments, including habitability. This should include steady state, transient and random response. Attention shall be given to dynamic responses resulting from environmental, machinery and propeller excitation. Uncertainties associated with modelling should be highlighted.

Recent advances in vibration control of offshore platforms

Abstract: Offshore platforms are widely used to explore, drill, produce, storage, and transport ocean resources and are usually subject to environmental loading, such as waves, winds, ice, and currents, which may lead to failure of deck facilities, fatigue failure of platforms, inefficiency of operation, and even discomfort of crews. In order to ensure reliability and safety of offshore platforms, it is of great significance to explore a proper way of suppressing vibration of offshore platforms. There are mainly three types of control schemes, i.e., passive control schemes, semi-active control schemes, and active control schemes, to deal with vibration of offshore platforms. This paper provides an overview of these schemes. Firstly, passive control schemes and several semi-active control schemes are briefly summarized. Secondly, some classical active control approaches, such as optimal control, robust control, and intelligent control, are briefly reviewed. Thirdly, recent advances of active control schemes with delayed feedback control, sliding model control, sampled-data control, and network-based control are deeply analyzed. Finally, some challenging issues are provided to guide future research directions.

Hydroelasticity of ships: Recent advances and future trends:

Abstract: Investigations into hydroelasticity of ships commenced in the 1970s. Since then the theory has been employed to predict the responses of a wide range of marine structures, such as mono- and multihulled ships, offshore structures, and VLFS. In recent years, with increasing market demands for new buildings of slender ocean going carriers and the continuously updated high-speed and unconventional multihulled designs, the maritime industry began to notice the advantage of assessing the usefulness and applicability of hydroelasticity in ship design.At first instance, the aim of this paper is to illustrate some of the applications of hydroelasticity theory to ships, with particular reference to recent and ongoing developments focusing on ship design applications and the effects of non-linearities and viscous flows. The paper also discusses the longer term potential use of weakly and fully non-linear fluid—structure interaction, as well as Navier—Stokes based fluid dynamic methods, for the improved modelling of ...