Abstract
Wave tank testing is a standard for validating scale models of wave energy converters (WECs). While physical geometries of WECs can be simply scaled, the mooring setup and forces are more complex to scale and accurately model due to flume depth limitations. There are limited approaches to modeling the dynamics seen in moored devices. The standard approach uses springs to replicate some of the forces experienced from mooring in at-sea tests. Springs (and all other current methods for replicating mooring forces on lab-scale WECs) cannot reproduce the real-world dynamics of mooring lines, fail to properly simulate nonlinear tension behaviors, and cannot be used to demonstrate failure events such as line breakage. To improve the testing fidelity of lab-scale WECs, it is critical to develop a technique for simulating mooring line forces. This work proposes a real-time hybrid simulation or hardware-in-the-loop method for simulating mooring dynamics. With this approach, simulations are used in conjunction with lab-scaled prototypes in a real-time feedback loop to introduce user-defined forces for a range of scenarios.
Our work will detail the design process for integrating a real-time hybrid mooring simulation with the wave flume at Oregon State University’s Hinsdale Wave Lab. This process includes the development of a numerical modeling environment using WEC-Sim and MoorDyn (a lumped-mass mooring model compatible with WEC-Sim and widely used in the marine energy space) and the design of a physical communication and actuation setup at the Wave Lab. The completed real-time hybrid simulation setup will involve a scaled WEC with mooring lines attached to motors driven by real-time results from WEC-Sim. The resulting system will be capable of applying realistic mooring forces on wave energy converters in the wave flume. This system can be used to test mooring effects with various mooring designs, water depths, and mooring line qualities, and will allow more extensive and accurate testing of WECs prior to full-scale deployments.