Numerical models in real-time hybrid model testing of slender marine systems

This paper presents a study of numerical models used in Real-Time Hybrid Model (ReaTHM) testing, conducted in a still water basin at SINTEF Ocean. ReaTHM testing is a method where a system is divided into physical and numerical substructures to study complex hydrodynamics on the physical system. Basin infrastructure limitations are handled by numerically modeling structural components with large geometrical extent. The numerical and physical substructures are coupled in real-time through a system of sensors and actuators. The emulated system under consideration in the study is a moored axisymmetric cylindrical buoy. The physical substructure is the buoy in model-scale ratio 1:144, while the numerical substructure is the full-scale mooring system consisting of twelve mooring lines. The time scale ratio requires the numerical models to run twelve times faster than real-time. To potentially reduce computational cost, a study is performed of three variations of numerical models, varying from low to high fidelity. The models are evaluated based on the sensitivity to jitter, induced time delays and clock drift imposed on the system.