Line contact: Data

Line contact data for all lines in the model are given on a single data form with two pages: Relationships and penetrator locations.



This option allows for individual relationships to be disabled and made inactive. A disabled relationship is ignored and has no impact on any calculations.

Penetrating line, penetrating line is, splined line

These three choices select two lines from those present in the model, and specify the contact and containment relationship between them.

The splined line will present a curved cylindrical contact surface to the penetrators attached to the penetrating line, and the curved cylinder axis will follow a smooth spline curve that follows and passes through the nodes of the splined line.

Penetrators on the penetrating line, as specified by the penetrator locations data, will then come into contact with this surface if they meet it, and experience reaction and friction forces that are calculated based on the normal stiffness and shear stiffness. The splined line contact surface will be either the external or internal surface of its curved cylinder, depending on whether the penetrating line is inside, outside or around the splined line. For more detail on how this interaction is modelled, see the modelling page.

Penetrator locations

Penetrators are attached to some or all of the nodes of the penetrating line. The default behaviour is to attach a penetrator at every node on the penetrating line, at the node centre. Alternatively, the distribution and position of penetrators on the penetrating line can be defined in detail, by defining a named data set of penetrator locations on the penetrator locations page of the data form, and then selecting that name set on the relationships page.

Containment enabled

Defines whether or not fluid loads and elastic solid contact on the inner line in this relationship should take account of its containment within the outer line.

Penetrator discretisation count and scale

Count specifies the number of penetrators used to represent the contact at each node or, if penetrator locations have been specified, at each row of the penetrator locations data set.

If the count is greater than one, the penetrators are discretised and the scale is used to calculate the effective contact radius and effective contact area of the penetrators.

Normal and shear stiffness

Normal stiffness can be either linear or nonlinear. A linear stiffness is given by a single stiffness value representing the reaction force that the contact generates per unit depth of penetration per unit area of contact. For nonlinear stiffness, use variable data to specify a table of reaction force per unit area of contact against depth of penetration.

Shear stiffness is used by the friction calculation. A value of 0 disables friction. A value of ~ results in the normal stiffness being used, in which case if the normal stiffness is nonlinear, the normal stiffness corresponding to a penetration of zero is used.

If both stiffness values are zero no contact forces will be applied, but fluid loads will still be affected by any containment that the relationship defines.

Friction coefficients

Normal and axial friction coefficients. If the axial coefficient is set to '~', then the normal friction coefficient is used for all directions of motion.

Penetrator locations

Number of data sets, name

A set of penetrator locations represents a specific distribution of line contact penetrators along the penetrating line. Each data set is named, rather than being associated with a particular relationship. These locations can therefore be used by more than one relationship if desired.

Position, z relative to

The penetrator locations are specified by giving their $x$, $y$ and $z$ position relative to the penetrating line. The $z$ value is the arc length along the penetrating line, starting from zero at either end A or end B according to z relative to; OrcaFlex will attach a penetrator to the line node nearest to the arc length required. The $x$ and $y$ values give the radial offset from the penetrating line axis, in line axes directions.

Contact diameter, contact area, contact length

The contact properties of the penetrators. The contact length specifies the length considered for scaling. A value of ~ for the contact length indicates that it is to be calculated as contact area divided by contact diameter.