Response in high waves
At FORCE Technology, we offer a range of accurate and cost-effective services to assist the designer, builder or operator with determining the seakeeping abilities through the initial and the detailed design phases.
At FORCE Technology, we offer a range of accurate and cost-effective services to assist the designer, builder or operator with determining the seakeeping abilities through both the initial and the detailed design phases.
Initial design phase – numerical servicesAt the initial phase, we offer traditional seakeeping calculations employing our linear 3D radiation-diffraction code OMEGA combined with our highly efficient analysis tool MotionLab. This provides the possibility to analyse multiple bodies, wave elevations including diffraction effects, detailed pressure fields, drift forces etc. The OMEGA code has been rigorously validated against model tests with good results in the linear domain.
Every year, we perform 20-30 commercial seakeeping assignments using OMEGA and MotionLab. If the seakeeping investigation is more complex and includes non-linear effects, we recommend RANS CFD where we for the last ten years have used the commercial CFD package STAR CCM+ and today have accumulated profound know-how combined with a large computer cluster available for our services.
Among the many assignments we have solved using RANS CFD are semi-submersibles, FPSO’s, mono buoys and everything in between.
Detailed design phase - model tests
For model tests, we will normally use our large state-of-the-art towing tank. The main benefi t of using the towing tank is that it is very cost-efficient compared to model tests in a large wave basin due to lower operational costs and less complex setups.
For the seakeeping tests, we normally work with two different mooring setups. We keep the vessel stationary with a soft mooring system designed to have minimum impact on the first order motions. The results of these tests are typically used to tune numerical models in order to perform full-motion analysis with all moorings and risers included.
Alternatively we will prepare a truncated mooring system either anchored to the bottom of our towing tank or to our movable seabed. The mooring lines typically consist of wire and spring or wire, weight and spring in order to match the full-scale properties of the moorings. We typically use this setup for proof of concept tests for new designs or for variation of designs or appendages.
Both setups can be towed in order to include current effects if required by the assignment. Thus the waves and the current will be co-linear.
If the scope of work is a full mooring investigation, we also have access to wave basins where we can perform tests of non-collinear waves and current and where the current will be generated by means of a current rack, but for the above described typical assignments, the towing tank is a much more cost-efficient facility to use.