Comparison of measured and calculated velocity profiles in the thruster wake


methods and tools for the hydrodynamic optimisation of a DP vessel’s thruster configuration during the design.


The project deliverables will include a cal- culation tool for DP capability calculations. This combines traditional DP capability plots with the evaluation of other operational criteria, such as motions and accelerations. Thruster interaction data obtained will be included in this tool. Guidelines will also be developed on how to use model tests and CFD calculations in the analysis of thruster interaction effects and for the optimisation of thruster configurations on DP vessels. More information can be found at http:// www.marin.nl/web/JIPs-Networks/Public/ TRUST.htm.


Calculation possibilities The applica- tion of CFD calculations for the analysis of thruster interaction is still largely unexplored. At this moment CFD calculations of a vessel hull, complete with all its thrusters, may seem too complex but suitable modelling methods will be investigated and developed in the near future. A thorough validation of CFD models against measurement results, both at model-scale and at full-scale, is required.


An example of some initial calculations on a single thruster under a schematical barge is shown. Results show the same trends found in the measurements by Nienhuis but further developments are necessary to achieve more accuracy.


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Z X Y


VelocityX: -0.2 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 CFD calculation of an azimuthing thruster below a barge


Research into CFD calculations for thruster interaction will first focus on the calculation of the velocities in the wake of a thruster in open water. The accurate calculation of the velocities, especially at larger distances from the thruster, is crucial for an accurate prediction of thruster interaction effects later on. Different modelling options will be investigated. Subsequently, increasingly complex configurations are considered, introducing step-by-step additional physics, such as friction forces on the hull, deflection of the thruster wake (Coanda effect), the effects of current and loads on appendages. Another example is the calculation of the


loads caused by the thruster wake on the opposite pontoon of a semi-submersible. In this manner, the performance of thrusters in various different configurations can be investigated.


The latest developments in CFD calculations and PIV measuring techniques offer new possibilities to increase the understanding of the physics of thruster interaction effects. The TRUST JIP will investigate the applica- bility, accuracy and limitations of CFD for thruster interaction by comparing the results from model tests, CFD calculations and full-scale measurements.


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