Rock on! MARIN tests Fall Pipe Ship design for Boskalis


Fall Pipe Ships com- bine the robustness of a working vessel


with the precision of a surgeon as they


drop rocks on exactly the right place. This combination of requirements


demands a special approach to the


hydrodynamic design and validation of such a vessel. Royal


Boskalis Westminster found that MARIN had the diverse areas of expertise


needed to obtain the best results.


Frans Quadvlieg & Klaas Kooiker


f.quadvlieg@marin.nl report 11


Dynamic Positioning (DP) capabilities and course stability were fundamental require- ments but MARIN also had to examine the behaviour of the ship in waves, the possible intake of green water and propulsive per- formance.


Special aft body design For good DP capability, two azimuthing thrusters in the aft ship were used for the main propulsion. For a full block ship, with its usual steep buttocks, this choice demands a special aft body design. The combination of head boxes on an aft body with steep buttocks can easily lead to flow separation. There- fore, an aft body design with integrated head boxes was developed using viscous flow CFD. The design was validated using a model test.


Directional stability of a full block ship with azimuthing thrusters is an issue with many ships. A dedicated skeg design was first


calculated and then several variations were tested using Free Running manoeuvring tests. This was combined with seakeeping tests to verify the open top requirements of IMO MSC/Circular 608.


DP capabilities thoroughly tested The DP capabilities were investigated in two phases. DP capability calculations were carried out, giving the vessel’s station- keeping capabilities based on mean wind, wave and current forces. For the initial sizing of the propulsors at an early design stage, this can be a very useful approach. However, these capability diagrams do not tell the full story. Therefore, DP model tests were carried out to further assess the stationkeeping capabilities. These tests give insight into stationkeeping accuracy and variations in thruster loading. In these model tests all physical aspects such as thruster interaction and thruster ventilation are automatically included.


76222


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32