Flexcom: Simulation software evolving in harmony with the offshore energy industry

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The advancement of offshore field developments into deeper water and harsher environments, coupled with progressively more stringent safety requirements, has led to the need for a high-quality software to support the engineering design process.

With a global track record spanning almost 40 years, Wood’s proprietary software Flexcom is a simulator for dynamic offshore structures and has delivered advanced engineering solutions to major operators, EPC contractors, equipment suppliers and engineering consultancy firms. This all-round software is suitable for a variety of scenarios, ranging from FEED studies, detailed engineering design, fatigue life assessment, structural installation and decommissioning. It is highly versatile, readily lending itself to applications in growing sectors such as marine renewable energy and floating offshore wind.

The name Flexcom derives from its origins as a computational software simulating flexible risers, befitting the emerging oil production technology of the North Sea in the early 1980s. By contrast, the most recent edition has been developed to focus on floating offshore wind. The tool’s evolution is a classic example of an innovative solution provider adapting to ever-changing industry requirements. From humble beginnings of just one client back in 1983, Flexcom now has a global user base of over 300.

So, what makes Flexcom unique? Fundamentally, Flexcom is a finite element analysis (FEA) tool that uses an industry-proven finite element formulation, widely acknowledged as best-in-class. Offshore structures undergo significant motions when subjected to ocean waves, therefore, unlike some other FEA solvers, Flexcom uses a convected coordinate technique to cater for large-scale displacements. Each element of the finite element discretisation has a local axis system associated with it, which realigns with the element as it moves in space and time. This allows small, strain-inducing elastic deformations to be accurately identified from sizeable rigid body motions. This technique makes Flexcom particularly well-suited to modelling structures that have large motions, such as the highly dynamic inter-array cables between floating offshore wind turbines.

Given the growing importance of offshore wind in the decarbonisation strategy of many countries, and particularly the predicted exponential future growth in floating wind, the requirement for validated numerical modelling tools to support detailed engineering design is now greater than ever. Wood established an independent technical advisory group in 2016, alongside some key players in floating offshore wind, which has helped to shape a new product known as Flexcom Wind. This tool provides state-of-the-art aerodynamic modelling delivered via a fully integrated coupling with the industry recognised OpenFAST software, while detailed structural analysis of subsea components, such as mooring lines and dynamic cables, is ensured by Flexcom itself.

Wood has been awarded multiple contracts for floating wind projects, supported by Flexcom Wind. One example was for a proposed wind farm located off the west coast of Ireland, an ambitious project targeting up to 1.35GW of wind power. In practical terms, this wind farm has the potential to power as many as 1,145,000 homes by harnessing the power of the North Atlantic wind. However, this location represents a harsh environment with severe seastates and high winds, posing significant challenges for the design of mooring systems and dynamic power cables, including long term fatigue performance and integrity of the cables. A truss element has recently been introduced to Flexcom, specifically designed for modelling structures with low structural bending stiffness, such as mooring chains. The new feature provides a highly efficient solution, with faster computation times compared with a traditional beam element.

Continually developing technology and solutions to meet the evolving industry requirements is a key focus area for Wood. A typical 1GW floating offshore wind farm will have over 120 dynamic cables, and the sheer volume of cables required for floating wind provides a unique opportunity to utilise digital twin and machine learning technologies to assist with integrity management.

Wood is actively developing a ‘Subsea Cable Digital Twin’. This digital twin considers both mechanical fatigue and electrically induced thermal damage, the former based on FEA in quasi-real time, where Flexcom is set to play a key role. This will sit alongside Flexcom’s sister product Layercom, a simulation tool which provides additional insight into fatigue at a localised cross-sectional level including armour wires and cable strands within the dynamic cable. The benefit of a digital twin approach is that an integrated, as-maintained picture of cable health can be developed, giving the owner confidence in real-time integrity and performance. The approach has been well validated by cable thermal monitoring and cable fatigue damage assessments for many operational cable assets in the North Sea. Wood’s long-term vision is to provide specialised software which meets both current and future industry requirements, where large scale deployments of floating wind become a commercial reality.

Originally published in Global Underwater Hub Magazine (page 14)

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