Static analysis

Purpose and method

The static analysis is designed to help find the static equilibrium of any assembly that can be defined in FRyDoM. It takes into account all elements that do not provide energy to the system : bodies, links (with no motorization), catenary lines, etc. The wave, wind and current field are of course set to null for the static analysis.

Warning

Almost all model forces are not included in the static analysis, including the hydrodynamic forces (radiation damping also). Only the hydrostatic forces and the damping forces are taken into account.

The static equilibrium is solved using a dynamic simulation with relaxation of the system, regularly applied. The relaxation consists in setting to null the velocity and/or acceleration of the bodies.

Note

The assembly of body linked is not solved in this analysis, but is done during the initialization of the system, as a prerequisite of any static or dynamic simulation. This means that the positions of the elements of the system do not need to be setup as already linked.

Assembly

Fig. 15 Representation of the elements at setup, after the assembly and after the static analysis.

Tolerance criteria

A tolerance criteria for the static equilibrium is defined as

\[\epsilon = \sum_{bodies} |\mathbf{v}|\]

where \(\mathbf{v}\) is the velocity of a body. If this criteria is below a user specified tolerance, the equilibrium is supposed to be reached and the static solving stops.