CONTEXT AND OBJECTIVES
Study of moored vessel in presence of waves is a very important issue for all harbour design project as vessel dynamic behavior has a direct impact on safety of (un)loading operation as well as on berth equipments (mooring lines & fenders) integrity. In addition, waves conditions are one of the main factors which could affect the berth operational downtime. As this downtime shall be very low to ensure cost-effectiveness of port, it shall be demonstrated that waves induced motion are acceptable to enable (un)loading operations in presence of the most frequent waves conditions.
Different numerical tools are available to perform dynamic mooring analysis of ships exposed to waves. However, despite the fact that these tools are very efficient to simulate rapidly a large amount of different environnemental and mooring conditions, some parameters used in these numerical models need to be calibrated from physical model tests measurements. Physical model tests are hence required to calibrate numerical simulations but are also necessary to model some specific hydrodynamic complex configurations for which numerical approach is not sufficient (as moored vessel close to rubble-mound breakwater for instance).
In order to improve the reliability and relevancy of numerical mooring analysis as well as to improve our understanding of some specific hydrodynamic complex configurations, a research project has been launched in ARTELIA hydraulic laboratory which consists in carrying out series of physical modelling tests to provide relevant experience feedbacks for numerical modelling.
DESCRIPTION OF THE MODEL AND TESTS CAMPAIGN
The physical model built in one of ARTELIA laboratory wave basin (30m long by 16m wide) consists in a Froude scaling at 1/80 scale of a LNG carrier vessel moored at a typical LNG terminal berth.
The LNG carrier vessel model (3.6m long) represents a spherical LNG carrier vessel of about 130 000m3 capacity moored at a berth composed of 6 mooring dolphins and 2 breasting dolphins in shallow water depths ranging from 14m to 18m. In addition, for some tests, some harbour structures (such as quays or rubble mound breakwater) are implemented into the model to analyse the impact of different kinds of structures (fully or partially reflecting the waves) on moored vessel behaviour. This mooring configuration in shallow water and in presence of harbour structures represents the context of typical harbour design project performed in ARTELIA.
Different wave incidences, water depths and wave conditions (in terms of Hm0, Tp) have been tested.
Tensions in mooring lines and forces in fenders have been measured by load cells based on strain gauge technology and motions of ship in the six degrees of freedom have been measured by Qualisys system infrared cameras. In addition, five wave gauges have been installed in the basin to control incident wave conditions. All data have been monitored and recorded during the 3 hours (prototype scale) of each test.
Then, a corresponding numerical model has been developed using DiodoreTM hydrodynamic software for comparison purpose and further numerical model calibration on the basis of physical model results.
The paper will describe in details the model set-up, the instrumentation, the ship model characteristics to comply to Froude scaling and the results of the physical and numerical models.