NEZZY Tank test 1:15 scaled model

Extending the gathered experience a 1:15 scaled elastic model is fabricated to investigate in material use, installation process and seakeeping behavior. In this model, all materials for the foundation are used similar to the full scale design to gather manufacturing and assembly experience. Especially the concrete legs are designed to meet exactly the Froude scale design requirements and the guy wires are made of carbon fiber similar to the full scale design.

Elastic load tests are performed in a dry condition to show the elastic behavior of the model. The results are compared with finite element method results to show the validity. Especially the tower and guy wire load distribution was investigated in detail to validate numerical results. An analysis shows that tower top loading is transferred via the guy wires into the foundation and the tower itself is loaded by gravity loading. In a separate test phase, bending in all concrete legs is investigated in all translational directions. Strain gauges measured the deformation as structural validation showing a great design agreement.

The same measurement equipment was used in the second project phase as hydrostatic and hydrodynamic testing phase. The model was shipped to NMRI (National Maritime Research Institute, Tokyo) and reassembled. In this phase, the nezzy characteristic mooring system with catenary lines and a single buoy was used as position keeping system. Each mooring line was equipped with load cells for simulation validation. Wind forces are applied by a specific thrust system based on 4 impellers. The entire system is tested in different sea states with regular waves, irregular waves and survival conditions. nezzy showed a great seakeeping behavior, especially at extreme sea states, the tower top motion was extremely low and the guy wire transfers the turbine loads direct into the mooring system. Wind and wave misalignment tests show a great wind alignment capability of the entire structure and the measurement results validated the used materials for full-scale use.