Page 37: of Maritime Reporter Magazine (September 2010)

September 2010 www.marinelink.com 37

Currently, MARIN is starting a Joint

Industry Project on the hydrodynamics of thruster interaction, called the Thrust Hy- drodynamics JIP (TRUST JIP). The

TRUST JIP aims to gain insight into physical phenomena, quantifying thruster interaction effects and investigating pos- sibilities for improvement. In the TRUST

JIP model test data, CFD calculations and full-scale measurements will be com- bined to provide the methods and tools for the hydrodynamic optimisation of a

DP vessel’s thruster configuration during the design.

The project deliverables will include a calculation tool for DP capability calcu- lations. This combines traditional DP ca- pability 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 ef- fects and for the optimization of thruster configurations on DP vessels. More in- formation can be found at http:// www.marin.nl/web/JIPs-Networks/Pub- lic/ TRUST.htm.

Calculation possibilities

The application 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 com- plex but suitable modeling 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 re- quired. An example of some initial cal- culations on a single thruster under a schematical barge is shown. Results show the same trends found in the measure- ments by Nienhuis but further develop- ments are necessary to achieve more accuracy.

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 cru- cial for an accurate prediction of thruster interaction effects later on. Different modelling options will be investigated.

Subsequently, increasingly complex con- figurations are considered, introducing step-by-step additional physics, such as friction forces on the hull, deflection of the thruster wake (Coanda effect), the ef- fects 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 configura- tions can be investigated.

The latest developments in CFD calcu- lations and PIV measuring techniques offer new possibilities to increase the un- derstanding of the physics of thruster in- teraction effects. The TRUST JIP will investigate the applicability, accuracy and limitations of CFD for thruster interac- tion by comparing the results from model tests, CFD calculations and full-scale measurements.

About the Author

Hans Cozijn ([email protected]) is sen- ior project manager at the Offshore de- partment of MARIN, the Maritime

Research Institute Netherlands.

Uncompromised Control

WaterJet Bow/Stern

Thrusters 75-2200 HP

JT575AM

HT600

Low Submergence

Requirement

Small Hull Penetrations

Auxiliary Propulsion/ “Take Home” Capability

Effective Thrust In Currents

Proudly Made

In The USA!

Goltens confirmed leasing 23,000 sq. m. in Dubai Maritime City to create a ship repair facility. Goltens is the first company to sign up for a plot in Dubai Maritime

City – Industrial Precinct (DMC) in an official signing ceremony in Dubai and con- firms that it will lease Industrial Precinct plots 6 and 7 for 25 years. “Shipowners around the world rely on us to solve critical repair projects. Now finalizing our agreement with the ship repair yard, Drydocks World, Jadaf Dubai, we can embark on building a new facility to consolidate all of our services in an optimum fashion under one roof, introduce some new services and provide additional capacity for fu- ture expansion,” said Paul Friedberg, President, Goltens Worldwide Service. The 2.27 million sq. m. Dubai Maritime City – Industrial Precinct is divided into the

Maritime Center, the Industrial Precinct, The Academic Quarter, the Marina Dis- trict, the Harbor Residence, and the Harbor Offices. The Maritime Center District is the center piece of Dubai Maritime City and will serve as an international hub for maritime business. This sector is a hub for ship repair facilities, yacht repair and manufacturing, as well as workshop units. The precinct is managed by Drydocks

World, Jadaf Dubai. “We are seeing viable signs of a market recovery. Despite a global shipping recession, there is a steady flow of ship repair activity and busi- ness. We are a global point of contact for best-in-class support, repairs and con- sulting. Our new workshop and repair/maintenance center will be our hub for the

Middle East,” said Friedberg. The new DMC– Industrial Precinct integrated work- shop facilities and administration/sales offices will be substantially larger than those at Goltens current location in Al Jadaf. An increased business portfolio, together with an expected future head count considerably larger than the current 520, has made facility expansion necessary. Goltens will start construction immediately and hopes to move into the new, more centrally located Dubai facilities by 3Q 2011.

The new facility will house both a large workshop and an administrative office in its new 15,000 sq. m. purpose built facility . The new purpose-built workshop will perform specialist 2/4 stroke diesel engine reconditioning and repair services in- cluding all associated engine room and mechanical services.

Goltens to Set-Up Shop in Dubai