Hydrodynamic Analysis

Calc incorporates a module for analysing the hydrodynamic performance of the hullform, which earlier formed the Hydrodynamics program. This module includes four modes:

• Powering Mode.

• Manoeuvering Mode.

• Seakeeping Mode.

• Dynamic Positioning mode.

The Powering sub-module, which incorporates a number of well proven empirically derived methods, can be used to predict the resistance and powering characteristics of a hullform and its associated appendages. This sub-module can also use resistance data obtained from model experiment tests in order to produce more accurate full size ship estimates.

The Manoeuvering sub-module, which uses semi-empirical formulae for both merchant vessels and warships, can be used to predict the following ship manoeuvering characteristics: crash stop, turning, zig-zag and reverse spiral manoeuvres. It is also possible to directly input hydrodynamic motion coefficients as determined from model experiments.

The Seakeeping sub-module, which uses the conventional linear response, strip theory based method, can be used to predict and assess the seakeeping capabilities of a hullform in wave conditions, including overall motions, global rigid-body accelerations, and the resulting hull girder dynamic vertical and lateral bending moments, torsion and shear forces at various stations.

Finally, the Dynamic Positioning sub-module provides the ability to design the thruster system of any vessel, which requires a station-keeping capability with three or more thrust units. The program undertakes a static analysis where the thruster system can be designed subject to steady environmental effects. A safety margin can be included to allow for unsteady environmental effects.

Calc can thus be used, in conjunction with the geometry modelling programs, during the early stages of the design development process in order to assess the feasibility of a particular hullform based on at-sea performance considerations. Calc can also be used at the design-approval stage where potential through-life in-service wave environment demands need to be determined.