ShipX

SINTEF has developed a programme for numerical calculation of station keeping performance of ships. The programme solves the DP problem statically, and requires a minimum of input, hence it is very well suited to be used in the early design phase. The programme is integrated in the hydrodynamic workbench ShipX.

The motivation for developing this software was to enable the ShipX workbench environment to provide the user with station keeping prediction capabilities. In addition, existing programmes were complicated to use requiring manual editing of input files, limiting user settings with respect to prediction options and lacking features required by our customers. In the development of the ShipX station keeping software, a fast-to use, easy-to-learn user interface has been one of the main focuses. 

The station keeping software is integrated as an application in ShipX, and has the same intuitive, easy-to-use user interface as the rest of ShipX. Running the calculations takes from a few seconds up to a few minutes, depending on the speed of the computer, the number of environmental headings calculated for, and the calculation method used. As soon as the calculations are finished, reports and plots are available directly from ShipX. Reports and plots can easily be exported to Microsoft Word or pdf for quick and easy report generating. 

Numerical methods 

The station keeping software has several calculation modes. 

In Capability Study mode the user defines what environmental effects to include, and the programme will iterate the magnitude of the environment to find the maximum withstandable environmental force for each heading (see Figure 1). 

In Propulsor Load mode the user defines the environment. The typical calculated result is the load on each propulsor (see Figure 2). 

The station keeping programme also supports IMCA, ERN, ABS and DPCAP specific calculation methods. 

Several generic propulsors are implemented in the programme, including rudder and propeller units. The user can implement their own propulsors through an open programming interface (using either Java or Fortran).

The power configuration is defined in a graphical tool where the user connects different objects of the power system (see Figure 3). 

The allocation routine implemented uses quadratic programming with minimum thrust optimisation. The allocation routine handles thrust saturation, thrust loss and forbidden zones on all propulsors. 

The environmental forces are based on force coefficients. Databases for wind, current and wave drift coefficients for a range of ships are included. Additional coefficients can be imported from open file formats, literature and other software.