During the past two years, DNV Software has continuously improved the HydroD package to simplify the process of modelling hydrodynamic systems for analysis of both hydrostatic and hydrodynamic performance. These features have been well received by designers of floating structures.
At the same time we have also introduced knowledge-based engineering to further simplify and accelerate the process of performing hydrostatic or hydrodynamic analysis. In GeniE it is now possible to make the models necessary for performing such analyses, including the creation of panel, mass and structural models. A significant benefit is, of course, that the same concept model may be used for structural analysis, hydrostatic analysis, hydrodynamic analysis and coupled analysis in deepwater conditions.
Using GeniE’s unique modelling capabilities, it is easy to generate standard structure types such as barges and spars, ship-like structures such as FPSOs, or combinations of these such as semisubmersibles and TLPs.
The images below show two different concept models to be used for panel modelling as well as structure analysis. The first image shows a model typically used for transportation analysis, i.e. stability and hydrodynamic analysis of the jacket on top of the floater. Structure-wise, the engineer may account for the hydrodynamic accelerations and so on when investigating the stresses in the floater or typical utilisation factors in the jacket.
The second image shows a semisubmersible model suited to, for example, traditional stability or hydrodynamic purposes, or coupled analyses in deep water. In the latter case the risers and anchor lines need to be modelled in DeepC.
Generally speaking, the modelling philosophies in GeniE are simple, flexible and easy to understand. There are several ways of doing this, but the most common work-flow is to define 2D profiles along the length of the vessel, perform skinning operations between each profile to create the outer shell or hull form, and then specify the components below the water line by defining the wet surface. This is the simplest model required to perform a hydro analysis.
If more detailed analysis is required, the internal structure may also be defined with a great deal of refinement. Internal tanks may also be simulated by defining which parts are subjected to the tank fluid. A significant benefit is that the tank filling is carried out in HydroD. This makes it very easy to do hydrostatic computations under damaged conditions or when designing a tank filling configuration (manually or automatically) given draught, trim or heel requirements.
It is also possible to make parametric panel models by defining variables in a journal input file (also known as the script file). This makes it very easy to perform multiple analyses to identify the optimum floater early in a design process. The images to the right show a parametric model of a simplified semi-submersible where it is possible to vary all the key input dimensions since they are defined as variables (typically length, height, diameters, distance between pontoons, location of columns, size of panels and so on).
By integrating certain GeniE features with those in HydroD, it is thus very easy to define the necessary input (model and environment properties) and carry out hydrostatic and hydrodynamic analyses to find the best possible design solution.