Orcaflex torsion
![orcaflex torsion orcaflex torsion](https://www.researchgate.net/profile/Cv-Ossia/publication/317267659/figure/fig1/AS:669448319008779@1536620325577/Typical-Umbilical-Material-Description-on-OrcaFlex-Interface_Q640.jpg)
Segment framesĪs is the case for a line segment, each blade half-segment carries a frame of reference. This angle is the difference in the user-specified structural twist of the two adjacent segments at their mid-segment arc lengths.Īt the ends of the blade, the B-frame carried by the first node is coincident with the blade root frame and the A-frame carried by the last node is coincident with the tip frame. However, their respective $x$-axes and $y$-axes are allowed to be rotated away from each other, by a constant angle, about their shared $z$-axis.
![orcaflex torsion orcaflex torsion](https://www.orcina.com/webhelp/OrcaFlex/Content/image/AnalyticCatenarySolutionGrid.gif)
At the node, these two frames are rigidly constrained together and share a common origin (the node's position) and common $z$-axis direction (the blade's axial direction at this arc length). Thus a node, which (other than an end node) connects two segments, carries two frames the segment on the node's root-side connects to the B-frame and the segment on the node's tip-side connects to the A-frame. The other ends of the pair half-segments are connected together, to form the whole segment, by the mid-segment frame – we will come to this below. Each half-segment is connected, at its outer end, to a frame carried by its adjacent node the A-half is connected to an A-frame carried by its root-side node and the B-half is connected to a B-frame carried by its tip-side node. The A-half is the half-segment nearest the blade root (end A), the B-half that nearest the blade tip (end B). A and B framesĮach blade segment is split, at the mid-segment arc length, into two half-segments which we call the A-half and the B-half. The structural model here is analogous to a line with torsion included: each node has six calculated degrees of freedom (three translational and three rotational), bending stiffness is represented by linear elastic rotational springs between the node $z$-axis and the segment $z$-axis, and axial and torsional stiffness by linear elastic springs at the mid-segment.
#Orcaflex torsion free
If the blade has free DOFs, the nodes can rotate and translate relative to each other, allowing blade flexibility to be modelled and aeroelastic coupling effects to be captured. Unlike lines, the blade DOFs can be fixed, in which case the nodes are rigidly constrained to each other and the blade forms a rigid body system (the blade can still be pitched relative to its fitting frame in this mode of operation). The root frame of reference of the blade is coincident with that of its associated fitting frame, except that it may be rotated about its $z$-axis by the blade pitch angle. The blade extends from the root at end A to the tip at end B. Blades are represented by a structural model similar in outline to that used by lines, with massless segments connecting nodes at which inertia is lumped, ordered from end A to end B.