Holland Class OPV
What would retrofitting a Hull Vane to the 108-meter Holland Class Oceangoing Patrol Vessels (OPVs) of the Royal Netherlands Navy do? This was the question asked by the DMO, the Defence Material Organisation of the Royal Netherlands Navy. A Computational Fluid Dynamics (CFD) study by Van Oossanen showed significant savings on fuel and CO2 emissions and improved operability of the vessel.
Based on the operational speed profile and the power curve of the ship, it was determined that the most fuel is consumed per year at speeds between 15 and 20 knots, in spite of the fact that the ship sails 86% of the time at speeds below 15 knots. The Hull Vane was therefore optimized for a speed of 17.5 knots.
As the vessel has a pronounced trim wedge, which is incompatible with a Hull Vane, the trim wedge was partially modified to the limits set by the DMO. Subsequently, CFD runs were done to determine the resistance at 5 knots, 12.5 knots, 17.5 knots and 22.5 knots, showing resistance reductions of 1.3%, 13.7%, 15.3% and 11.1% respectively. Multiplied by the operational speed profile, this results in an annual saving on fuel and emissions of 12.5%. The amount of CO2 emissions avoided will exceed 1.000 tons per ship per year, making the Hull Vane an extremely cost-effective CO2 abatement measure, as the investment will be paid back many times over during the lifetime of the ship.
To study the influence on the operability of the vessel, a seakeeping analysis was done in a typical wave condition. This showed a reduction of the pitching movements of 7% and a reduction of the vertical accelerations on the helicopter deck of 13%. As the vertical accelerations are the limiting factor for helicopter operations, this will enlarge the operational envelope of the vessel.
The turbulent wake zone behind the stern was reduced by about 50%, making the launching and recovery of the RHIB (Rigid-hulled inflatable boat) through the stern slipway safer and easier. Finally, the range of the vessel will be increased by 17% from 5.000 to 5.850 nautical miles.
As the savings are greater and the costs lower in the case of a newbuilding, the DMO has indicated that they will also consider the Hull Vane for their future newbuilds.
The paper written about this CFD study can be downloaded here, and will be presented by Bruno Bouckaert, Commercial Director at Hull Vane BV, on the FAST 2015 Conference in Washington DC, from 1 to 4 September 2015.
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