Line Bodies are used to create line elements for Aqwa. How they are interpreted depends on the cross section of the line; if it has a circular or circular tube cross section, then it will be automatically converted into a standard tubular (TUBE) element. All other sections with dual symmetry will create slender tube (STUB) elements. Cross sections which are not dual-symmetric are not permissible in Aqwa, as the centroid and geometric center of the cross section are required to be coincident.
Beam Properties
Each Line Body should be assigned a cross section and an orientation in DesignModeler/SpaceClaim Direct Modeler. In the Aqwa editor, when importing the geometry, each valid cross sectionis automatically paired with a Beam Section object. Beam Sections are created under the Line Body Data object in the Outline tree. Apart from storing the geometric properties of the cross section, a Beam Section object also allows mass and hydrodynamic properties to be defined.
Once the geometry has been imported, the name of the cross section assigned to a Line Body in the geometry editor is provided for reference in the Cross Section field of the Line Body details.
Each Line Body has a Beam Section associated with it. The Line Body inherits geometric, mass and hydrodynamic properties from the Beam Section. The cross section storedin the Beam Section must match the Cross Section of the Line Body.
Where multiple Line Bodies have the same cross section but different mass or hydrodynamic properties, a Beam Section can be Duplicated. The duplicate Beam Section will retain the same cross section geometry, but can have different mass or hydrodynamic properties defined. In the Line Body details, the Beam Section field can then be used to select which Beam Section the Line Body inherits its properties from.
Note: It is not possible to change the geometric properties of a Line Body in the Aqwa editor. To do his you must edit the cross section in DesignModeler/SpaceClaim Direct Modeler and re-import the geometry.
For Line Bodies with circular tube cross sections, the Tube Type field allows you to make the tube Sealed or Floodable. By default, the tube is sealed, and in this case the tube is buoyant; however, the tube does not have longitudinal drag or added mass unless discs are created at the ends.
For Line Bodies with circular or circular tube cross sections, discs can automatically be applied at either (Created at End A Only, Created at End B Only) or both (Created at Both Ends) ends with the Tube End Discs option; if you choose one of these options, default disc parameters are used. If you require different parameters, discs can be excluded here and added manually. You cannot automatically add discs to Line Bodies with non-circular cross sections, but you can add them manually if needed.
Note: All non-circular cross sections are graphically represented as solid rectangles in Aqwa.
Beam Mass Properties
The mass properties of the Line Body (Mass and X, Y, Z Position of Body COG) are displayed for information. The mass of the Line Body is determined from the cross section area and material density of its associated Beam Section, and its center of gravity is calculated from the positions of the nodes along the Line Body length.
Line Body Axes
The Local Tube Axes (LTA) are defined with their origin at the position of the first node of the element. The LTA X-axis points from this origin toward the second node of the element. If the orientation of the Line Body has not otherwise been defined in DesignModeler/SpaceClaim Direct Modeler, the LTA Y-axis is parallel to the Fixed Reference Axes (FRA) XY plane, and at right-angles to the LTA X-axis; where the LTA X-axis is vertical in the FRA, the LTA Y-axis is parallel to the FRA Y-axis. The LTA Z-axis follows the right-hand rule. For more information, see Morison Equation in the Aqwa Theory Manual.