Compartments - Ultramarine.com

Compartments - Ultramarine.com Compartments

Compartments are entities used for three purposes:

To define hydrostatic, wind, and current forces on complicated shapes,
To define the sea/body interaction forces on things for which Morison's Equation is not applicable, and
To define ballast in the interior of a body.

In essence, compartments are used to model the exterior of bodies and the interior compartmentation of bodies. Thus, we have two types of compartments: interior and exterior.

The distinction between interior and exterior compartments is made when the compartment is named. Whenever a body is defined, MOSES will automatically define a compartment with the same name as the body. This compartment is an exterior compartment. Any other compartment defined whose name is not also the name of some part is an interior compartment. Only exterior compartments can attract hydrodynamic loads, and only interior compartments can be flooded or ballasted.

Compartments are a collection of two basic entities: pieces and tube tanks. A tube tank is used to model the interior of a tube, and pieces are used to model everything else. In essence, a piece is a "ship like" part of the compartment. When a piece is part of an exterior compartment it creates buoyancy, drag force, wind force, and behaves according to either Strip Theory, Three Dimensional Diffraction Theory, or attracts no hydrodynamic load at all. When part of an interior compartment, it can be damaged (flooded) or ballasted and defines part of the inertia of the system. The way to define pieces and tube tanks will be discussed below.

Compartments are defined in a fashion similar to bodies and parts. In other words, the data for a compartment follows an &DESCRIBE command naming the compartment:


     &DESCRIBE COMPARTMENT, CNAME -OPTIONS

Here, CNAME is the name of the compartment and the options define additional attributes for interior compartments and will be discussed later.

Tube tanks are a computationally efficient way to define interior compartments. The only restriction is that the physical shape defined by a tube tank must be a circular cylinder. A given compartment can have as many tube tanks as desired, and each one is defined by:


     TUBTANK, DIA, PNT(1), PNT(2)

Here, DIA is the diameter (inches or mm) of the tank and PNT(1) and PNT(2) are the names of two points defining the ends of the tank. Alternately, the coordinates of the ends (feet or meters) can be input instead of point names. If one uses coordinates, points will be defined with these coordinates. These tanks can be mixed with other pieces for an internal compartment. If one attempts to define a tube tank for an exterior compartment, an error will result.