Hydrodynamic Assessment and Motion Optimization of Mechanically Coupled Barges

Hydrodynamic Assessment and Motion Optimization of Mechanically Coupled Barges

Mathios, V.A.

Metrikine, A.V. (mentor)
Van Wingerden, J.W. (mentor)

Civil Engineering and Geosciences

Offshore Engineering

2015-11-23

The decommissioning market expenditure is expected to grow further in the years to come due to increasing number of platforms that near the end of their production cycle, mainly being xed steel structures (<4,000 [Te]) positioned in shallow waters (30 to 75 [m]). The risks of such operation emerged the need for semi-submersible, heavy-lift vessel or ultimately catamaran vessel design (i.e Pioneering Spirit), all being expensive concepts with high lifting capacities making a single-lift option possible, also ensuring robust operating windows; however, these designs are tailored to be project-speci c and technically redundant. Such way of thinking do not comply with the lean, modular and reusable engineering philosophy Mammoet Global Engineering is introducing via its novel conceptual design counterproposal, under the name Mammoet O shore Platform (MOP); a twin barge concept with proper mechanical couplings would create a modular and thus resusable, less stiff configuration that achieves operational robustness in irregular seas.The technical challenge identi ed is the asymmetric barge roll motion due to the eccentric topside weight and the respective roll hydrodynamic loading. Roll motion in beam waves ( 900angle of attack) is expected to be the dominant design parameter and is addressed via the implementation of a kinematic constraint so that barges and topside roll (f) is synchronized. Furthermore, the barges are modeled to heave and pitch independently, therefore significant differential motions in the corresponding DOF (bank : & flip : ) are anticipated and need to be treated; the use of a passive link, modeled as a spring-dashpot, has qualified while its structural parameters will be optimized with the H1 technique. The research question in hand comprises of MOP concept technical feasibility study which will be quantitatively assessed via the following Key Performance Indices (KPI): Steady-state dynamic behavior of MOP (constrained barges) against two free oating barges and a catamaran barge of identical geometry speci cations, working entirely in the frequency domain (modeling in linear potential solver Wamit) Steady-state dynamic behavior of MOP (constrained barges & link optimized in H1) against the model identified in the previous analysis (state-space modeling and control in Matlab) The frequency domain simulations for the case studies tabulate that the roll kinematic constraint has successfully attenuated & shifted the peak response while the link structural properties optimization has minimized the differential barge motions in heave and pitch ensuring wider operational windows and verifying this work ow as a proof of concept.

multibody dynamics
hydrodynamics
H infinity synthesis

http://resolver.tudelft.nl/uuid:d4a9cfd0-84e5-4094-958a-52109e173fb7

Student theses

master thesis

(c) 2015 Mathios, V. A.