The outcome is a highly non-linear and hysteretic response (meaning there is a lag in the stiffness behavior due to internal friction), which changes with the applied level of tension.
Stick-slip is where the outer armour wires go through rapid change from a high to low bending stiffness once frictional forces are overcome. The stick-slip armour wire behavior is also calculated with a Python script. The model can also be linked to live data from the test rig itself to create a true digital twin. This way, the user can get a feel for how different test setups change the cable response. OrcaFlex is coupled with the Python programming interface so that the user can change the model in real time. The model presented here is a more unusual application in a workshop environment.
ORCAFLEX SOFTWARE
OrcaFlex has become an industry standard software for marine dynamic analysis, including floating wind systems. The tests can be performed in seawater and at high voltage to better simulate the real operating environment. ORE Catapult’s dynamic cable test rig applies the same load cycles as would be experienced in service – meaning problems can be identified and fixed in the factory, avoiding costly offshore repairs. In order to improve the reliability of dynamic cables, we need to improve our understanding of them, improve designs, and ensure that they are more rigorously tested than the current generation of static cables.
Cables are sensitive and complex components, and in their dynamic form will be subject to millions of bending cycles during their lives in the harsh ocean environment. Static cables will not be suitable for the next generation of floating wind assets, as they were designed for service in environments wholly different to those experienced by cables for floating wind in deeper waters. I made use of some spare time in lockdown to make a digital twin of our dynamic cable test rig – partly as a tool to understand cable behavior, but mainly as an excuse to improve my programming skills. Getting to grips with test equipment is not always easy. Will Brindley, Research Engineer, Offshore Renewable Energy (ORE) Catapult
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