Model Testing
Overview
Model testing is the final stage of the design process. It is common practice in the industry to perform these tests to validate calculations and if anything to provide more in depth knowledge of the vessel in question.
For a Spar with mooring the test should contain testing the natural frequency of the system to make sure that extreme excitations in the natural frequency won’t arise.
Besides that model testing should measure the actual forces placed on the mooring system to check if it has been designed correctly, combined with this test it is possible to test if the system can survive the limit state condition with the excitation within the limitations given by the
client.
With the test result there are three possibilities.
1. The system has been designed incorrectly creating a system which has a natural frequency within the wave domain.
2. The system can’t hold the limit state design, either the mooring fails or the excitations become larger than stated by the client.
3. The system has been designed correctly and can be build.
Options 1 and 2 are not acceptable.
There are two options for changing the system.
The first a change of the mooring system i.e. number of lines and spread type. The second option is to change K which means that it has been miscalculated in the first instance.
The total system has now been tried and tested. If you encounter problems in this phase, then one should go back to the drawing board. If the forces are too large then one should go back to the design phase and make alterations. If the motions are to large, then the mooring system stiffness is insufficient. If on the other hand all the parameters are correct, the final design is ready to be built!