Global Product Management delivering on your requests for new features supporting floater design.

Encouraged by advances in the user interfaces available in DeepC, GeniE and HydroD, several customers have asked us to implement features for stability computations and tank balancing. The development for the first release of these features is now complete; they will be available as an extension to HydroD later this year. HydroD will also be capable of hydrodynamic analysis of floating structures which have a trim or heel as computed in the stability analysis, with the hydrodynamic calculations performed using Wadam.

In addition, HydroD can now be used to import a panel and mass model from both GeniE and Patran-Pre. In the first case concept modelling is used throughout, from model creation right through to report generation, showing detailed results including GZ-curves and still water bending moments. The report created contains all the information necessary to fully document hydrostatic stability.

We have added panel modelling capabilities to GeniE since these were identified as top priority requirements by our customers. This means it is very easy to create models intended for hydrodynamic as well as hydrostatic analysis in HydroD. You can take the concept model created in GeniE and continue working on it in HydroD. The most recent version of GeniE (v3.2) includes features for panel modelling of curved and planar plates. These are available as extensions to the standard GeniE installation. (Fig. 1)

Fig. 1: A panel model created in GeniE, with the positon of a particular tank (left) and the non-symmetrical mass model (right).

With the new version you can also model internal tanks (one per loadcase) for subsequent use within HydroD in its tank balancing or stability calculations. You do not need to specify the tank fluid level in GeniE or Patran-Pre as this is done in HydroD – this allows the designer to easily change the filling fraction and density of the fluid and immediately see the effects on floating position and other important data such as the GZ-curve. (Fig. 2)

Fig. 2: The floater in equilibrium position with high heel and trim due to tank filling and the non-symmetrical point masses added to the floater. The red dot represents a user-specified postion for computation of the distance to the water line.	The important GZ-curve, distance to the waterline and the still water bending moment. In this case the up-righting moment (0-40 degrees) is 1.85E08Nm.

There are several ways of improving the stability characteristics – one way is to change the filling of the various tanks. This can be done manually or automatically – three tanks at a time – in the latter case the designer specifies a target draught, trim and heel. (Fig. 3)

Fig. 3: A new equilibrium position is computed following an automatic tank balancing (the floater has no trim). The stability characteristics are improved as can be seen on the graph to the right, the GZ-curve integral (0-40 degrees) has improved from 0.4m to 1.2m. Similarly, the up-righting moment (0-40 degrees) is now improved by a factor of 2.6 to 4.852E08Nm. This requires only three user operations - specify no trim, perform automatic tank filling, and re-compute the stability characteristics.

The new features for hydrostatic stability computations in GeniE and HydroD provide excellent flexibility and make it very easy for designers to perform the type of analyses described above, as well as to do sensitivity studies, whether considering the hull form, the filling of tanks or the position of additional masses.