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.

Adequate information on response in waves is crucial to be able to perform structural design and design of mooring lines and risers on offshore ships and floating platforms. This information is most efficiently obtained through seakeeping tests performed either numerically or through model tests.

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 services

At 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.
Seakeeping calculation using RANS CFD. 

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.