Why is VIVANA-TD a game changer?
Vortices can be generated in backside of the structure in a flow. The periodic vortex shedding may lead to resonance when its frequency is close to the natural frequency of the structure. Therefore, vortex induced vibrations (VIV) can induce rapid fatigue damage and increase drag loads, compromising structural integrity.
Traditional frequency-domain tools often yield overly conservative and costly designs because they struggle to capture the complex interaction between waves, currents, floater motions and nonlinear structural responses. In contrast, VIVANA-TD utilises a semi-empirical time-domain model integrated into the non-linear 3D finite element tool RIFLEX, enabling a much more comprehensive analysis, especially useful for deepwater riser systems, umbilical, and power cables for offshore floating wind turbines, where accurate VIV response predictions are very important.
Key advantages:
- Enhanced capabilities: VIVANA-TD can capture changes in tension, structural non-linearity and multi-directional flow conditions. It considers the wave frequency and VIV load contributions simultaneously, offering a thorough analysis that improves the safety and cost-effectiveness for slender marine structure designs.
- Robust validation: Comprehensively tested and validated in the LWR JIP (Lazy Wave Riser Joint Industrial Project) and other parallel research and projects in SINTEF Ocean.
- Industrial readiness: With Equinor’s TRL 4 approval, the tool has proven to be ready for design and production, marking a new standard in offshore engineering.
The evolution of VIVANA-TD and the LWR JIP journey
Tackling the challenge of complex configurations
The lazy wave configuration, see the illustration below, widely used to connect floaters to subsea infrastructure, is one of the most challenging design options. By employing buoyancy elements to create a wave-like shape, this design improves fatigue performance and reduces loads on floating platforms. However, predicting the behaviour of such complex configurations in variable environmental conditions (waves, currents, floater motion) has long been problematic, leading to designs that are both overly cautious and expensive. The LWR JIP has been a successful title to address the challenges here.
Bridging the gap through innovative research
The idea of VIVANA-TD comes from the need to reduce the uncertainties in conventional VIV design methodologies. Traditional frequency-domain tools fail to fully capture the dynamic interplay between wave forces and nonlinear structural responses. VIVANA-TD addresses this gap by incorporating a semi-empirical time-domain model into the established finite element framework of RIFLEX. This integration allows for a dynamic analysis that realistically simulates tension variations, non-linear behaviours, and multi-directional flow conditions.
Achievements in phases I & II
The initial two phases of the LWR JIP played a crucial role in confirming the suitability of VIVANA-TD for industrial applications. Major achievements include:
- Accurate performance across conditions: Extensive validation under both steady and oscillatory flow conditions verified the tool’s capabilities.
- Further integration of non-linear structural models: The incorporation of hysteresis damping and stiffness models gives the potential to model more realistically the non-linear structural properties of complex cross-sections.
- Collaborative training & validation: Hands-on training sessions and comprehensive feedback from industry partners have refined the tool, ensuring its practical applicability.
These accomplishments have laid a solid foundation for the ongoing Phase III, where further challenges—such as predicting behaviour under combined environmental conditions—are being addressed.
Equinor TRL 4 approval: A major milestone
Equinor recently approved the VIVANA-TD for Technology Readiness Level (TRL) 4 —a major milestone that transforms this solution from an academic research tool into a trusted engineering tool for the offshore industry. Developed through LWR JIP in collaboration with NTNU, VIVANA-TD offers game-changing time-domain prediction capabilities to address the challenges in the design of slender marine structures against VIV.
The TRL 4 designation from Equinor is a significant industrial endorsement, which delivers following messages:
- Field-readiness: VIVANA-TD has passed systematic tests with solid performances and is now ready for use in engineering projects.
- Research-to-practice transformation: What started as an academic exploration has matured into a robust tool that directly addresses the safety and cost challenges faced by the offshore industry.
- Setting new industry standards: With its promising prediction accuracy and validated performance, VIVANA-TD is ready to improve the best practices in VIV analysis and slender marine structure design.
Looking ahead – Phase III and future directions
Building on the success of the earlier phases and complementary research at SINTEF Ocean, Phase III will now focus on new functionality development and validation. Key tasks include:
- Evaluating combined environmental conditions: Testing and refining prediction models for marine risers and dynamic power cables under the simultaneous impact of waves and currents, with dedicated assessments of hysteresis stiffness and damping.
- Industrial training and hands-on case studies: Conducting practical, partner-driven case studies with robust technical support from SINTEF Ocean, ensuring that the tool is optimized to meet challenges in engineering practices.
- Formulating design recommendations: Collaborating closely with industrial partners to develop targeted recommendations and improvements for design practices, fostering safer and more cost-effective engineering solutions.
These tasks will enhance VIVANA-to be an industry-standard solution, ensuring that the tool not only demonstrates superior performance under complex conditions but also drives innovative advancements in marine structural design.
Continuing the process
The evolution of VIVANA-TD—from an innovative research tool to an industry qualified engineering solution—is an exciting progress we are proud to share. This breakthrough not only enhances prediction accuracy and cost-effectiveness but also sets new benchmarks in safety standards. As the tool further matures through continued industrial collaboration through LWR JIP Phase III, it is expected to play an important role in driving the green energy transition by enabling safer, more reliable offshore designs.
Stay tuned for further updates as we continue to push the boundaries of marine engineering innovation!
