Flexcom 8.3.2 running on Windows 7
|Developer(s)||Wood Group Kenny Ireland|
8.4.4 / March 3, 2016
|Development status||Actively developed|
|Operating system||Microsoft Windows|
|Type||Finite element analysis|
|License||Proprietary commercial software|
The name Flexcom derives from its origins as a computational software initially geared towards the analysis of flexible risers, befitting the emerging riser technology of the North Sea in the early 1980s. The first version of the software was released in 1983, and a continuous update program has been maintained ever since. As of March 2016, the version on general release is Flexcom 8.4.4.
The program uses a specialised finite element formulation, incorporating a hybrid beam-column element with fully coupled axial, bending and torque forces, well suited to the modelling of slender offshore structures such as risers and mooring lines. A range of seastate modelling options are provided, and hydrodynamic loading is based on Morison’s equation. Although originally a time domain analysis tool, more recent versions of Flexcom also incorporate frequency domain analysis capabilities. It is also capable of performing modal analysis and estimating damage caused by fatigue.
Hybrid beam element
In order for the software to be capable of analysing flexible structures (such as flexible risers, mooring lines etc.), in addition to more rigid structures (such as steel catenary risers, pipelines etc.), a numerical solution scheme is required which caters for
- bending stiffnesses which are much lower than both axial stiffness and torsional stiffness values, and
- arbitrarily large and nonlinear displacements and rotations in three dimensions.
To accommodate the low or zero bending stiffness problem, very early versions of Flexcom were based on a 2D hybrid beam-column element. In this approach the axial force appeared as an explicit nodal solution variable, and was interpolated independently of the axial strain. The stress-strain compatibility relationship was applied outside of the virtual work statement by means of a Lagrangian constraint. This proved an accurate approach, and was subsequently extended to three dimensions. Further developments resulted in the addition of an extra Lagrangian constraint on the torque degree of freedom, in order to make the scheme more robust and accurate when this variable plays a significant role in the solution. This leads to a fourteen degree of freedom hybrid finite element with two end nodes, where the axial force and torque are added to the usual form of a three-dimensional beam element.
- McNamara, J.F.; O'Brien, P.J.; Gilroy, J.P. (April 1986), "Nonlinear Analysis of Flexible Risers Using Hybrid Finite Elements", Proceedings of the 5th International Offshore Mechanics and Arctic Engineering Symposium, 3, Tokyo: ASME, pp. 371–377. (Later published as: McNamara, J.F.; O'Brien, P.J.; Gilroy, J.P. (1988), "Nonlinear Analysis of Flexible Risers Using Hybrid Finite Elements", Journal of Offshore Mechanics and Arctic Engineering, ASME, 110 (3): 197–204, doi:10.1115/1.3257051)
- O'Brien, P.J.; McNamara, J.F. (June 1988), "Analysis of Flexible Riser Systems Subject to Three-Dimensional Seastate Loading", Proceedings of the International Conference on Behaviour of Offshore Structures (BOSS '88), 3, Trondheim, Norway, pp. 1373–1388
- O'Brien, P.J.; McNamara, J.F.; Grealish, F. (June 1991), "Extreme Bending and Torsional Responses of Flexible Pipelines", Proceedings of the 11th International Offshore Mechanics and Arctic Engineering Symposium, Calgary, Canada: ASME, pp. 319–324