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Stochastic procedures for extreme wave induced responses in flexible ships
Jørgen Juncher Jensen,Ingrid Marie Vincent Andersen,Sopheak Seng 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.4
Different procedures for estimation of the extreme global wave hydroelastic responses in ships arediscussed. Firstly, stochastic procedures for application in detailed numerical studies (CFD) are outlined. The use ofthe First Order Reliability Method (FORM) to generate critical wave episodes of short duration, less than 1 minute,with prescribed probability content is discussed for use in extreme response predictions including hydroelastic behaviourand slamming load events. The possibility of combining FORM results with Monte Carlo simulations is discussedfor faster but still very accurate estimation of extreme responses. Secondly, stochastic procedures using measured timeseries of responses as input are considered. The Peak-over-Threshold procedure and the Weibull fitting are applied anddiscussed for the extreme value predictions including possible corrections for clustering effects.
Stochastic procedures for extreme wave induced responses in flexible ships
Jensen, Jorgen Juncher,Andersen, Ingrid Marie Vincent,Seng, Sopheak The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.4
Different procedures for estimation of the extreme global wave hydroelastic responses in ships are discussed. Firstly, stochastic procedures for application in detailed numerical studies (CFD) are outlined. The use of the First Order Reliability Method (FORM) to generate critical wave episodes of short duration, less than 1 minute, with prescribed probability content is discussed for use in extreme response predictions including hydroelastic behaviour and slamming load events. The possibility of combining FORM results with Monte Carlo simulations is discussed for faster but still very accurate estimation of extreme responses. Secondly, stochastic procedures using measured time series of responses as input are considered. The Peak-over-Threshold procedure and the Weibull fitting are applied and discussed for the extreme value predictions including possible corrections for clustering effects.
Global hydroelastic model for springing and whipping based on a free-surface CFD code (OpenFOAM)
Sopheak Seng,Jørgen Juncher Jensen,Šime Malenica 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.4
The theoretical background and a numerical solution procedure for a time domain hydroelastic code arepresented in this paper. The code combines a VOF-based free surface flow solver with a flexible body motion solverwhere the body linear elastic deformation is described by a modal superposition of dry mode shapes expressed in alocal floating frame of reference. These mode shapes can be obtained from any finite element code. The floating frameundergoes a pseudo rigid-body motion which allows for a large rigid body translation and rotation and fully preservesthe coupling with the local structural deformation. The formulation relies on the ability of the flow solver to provide thetotal fluid action on the body including e.g. the viscous forces, hydrostatic and hydrodynamic forces, slamming forcesand the fluid damping. A numerical simulation of a flexible barge is provided and compared to experiments to show thatthe VOF-based flow solver has this ability and the code has the potential to predict the global hydroelastic responsesaccurately.
Global hydroelastic model for springing and whipping based on a free-surface CFD code (OpenFOAM)
Seng, Sopheak,Jensen, Jorgen Juncher,Malenica, Sime The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.4
The theoretical background and a numerical solution procedure for a time domain hydroelastic code are presented in this paper. The code combines a VOF-based free surface flow solver with a flexible body motion solver where the body linear elastic deformation is described by a modal superposition of dry mode shapes expressed in a local floating frame of reference. These mode shapes can be obtained from any finite element code. The floating frame undergoes a pseudo rigid-body motion which allows for a large rigid body translation and rotation and fully preserves the coupling with the local structural deformation. The formulation relies on the ability of the flow solver to provide the total fluid action on the body including e.g. the viscous forces, hydrostatic and hydrodynamic forces, slamming forces and the fluid damping. A numerical simulation of a flexible barge is provided and compared to experiments to show that the VOF-based flow solver has this ability and the code has the potential to predict the global hydroelastic responses accurately.
Mancini, L.,Giacobbe, P.,Littlefair, S. P.,Southworth, J.,Bozza, V.,Damasso, M.,Dominik, M.,Hundertmark, M.,Jørgensen, U. G.,Juncher, D.,Popovas, A.,Rabus, M.,Rahvar, S.,Schmidt, R. W.,Skottfelt, J.,S EDP Sciences 2015 Astronomy and astrophysics Vol.584 No.-
<P>Context. Photometric monitoring of the variability of brown dwarfs can provide useful information about the structure of clouds in their cold atmospheres.The brown-dwarf binary system Luhman16AB is an interesting target for such a study, because its components stand at the L/T transition and show high levels of variability. Luhman16AB is also the third closest system to the solar system, which allows precise astrometric investigations with ground-based facilities. Aims. The aim of the work is to estimate the rotation period and study the astrometric motion of both components. Methods. We have monitored Luhman16AB over a period of two years with the lucky-imaging camera mounted on the Danish 1.54m telescope at La Silla, through a special i + z long-pass filter, which allowed us to clearly resolve the two brown dwarfs into single objects. An intense monitoring of the target was also performed over 16 nights, in which we observed a peak-to-peak variability of 0.20±0.02mag and 0.34±0.02mag for Luhman16A and 16B, respectively. Results. We used the 16-night time-series data to estimate the rotation period of the two components. We found that Luhman16B rotates with a period of 5.1 ±0.1h, in very good agreement with previous measurements. For Luhman16A, we report that it rotates more slowly than its companion, and even though we were not able to get a robust determination, our data indicate a rotation period of roughly 8h. This implies that the rotation axes of the two components are well aligned and suggests a scenario in which the two objects underwent the same accretion process. The 2-year complete data set was used to study the astrometric motion of Luhman16AB. We predict a motion of the system that is not consistent with a previous estimate based on two months of monitoring, but cannot confirm or refute the presence of additional planetary-mass bodies in the system.</P>
High-precision photometry by telescope defocussing - VI. WASP-24, WASP-25 and WASP-26
Southworth, J.,Hinse, T. C.,Burgdorf, M.,Calchi Novati, S.,Dominik, M.,Galianni, P.,Gerner, T.,Giannini, E.,Gu, S.- H.,Hundertmark, M.,Jorgensen, U. G.,Juncher, D.,Kerins, E.,Mancini, L.,Rabus, M.,Ric Oxford University Press 2014 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.444 No.1