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Power Prognosis

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Wake Field Calculation/Optimization

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CFD_wake_abb3

The wake fields between model and full-scale show differences because of the underlying physics. In model-scale the boundary layer is thicker relative to full-scale and the bilge vortex more pronounced. This results in differences in the inflow to the propeller between model and ship, which should be considered when designing the propeller. Through the use of numerical methods, the wake field can be calculated for both the model and the ship. Thus it is possible, already while designing the ship lines, to evaluate the wake field and the influence of geometry modifications or appendages. Further, the wake field can be made available for propeller design.

The numerical simulations offer the following advantages:

  • Calculation of the wake field in the preliminary design stage
  • Calculation of the wake field for the Reynolds number of the vessel
  • Evaluation of the velocity components of the wake for any radius and angular increments
  • Visualising the inflow and presentation of the causes (for example, separations) for potential irregularities

 

CFD_wake_abb2CFD_wake_abb1

 

Context Related References / Research Projects

[1] Abdel-Maksoud, M., Lübke, L.: Berechnung des Nachstromfeldes der Großausführung, 97. Hauptversammlung der Schiffbautechnischen Gesellschaft, Hamburg, 20.-22.11.2002
[2] Lübke, L.: Calculation of the Wake Field in Model and Full-scale, NAV 2003, International Conference on Ship and Shipping Research, Palermo Italy, 24.-27. June 2003
[3] Lübke, L.: Calculation of the Wake Field in Model and Full-scale, CFX Conference 2003, Garmisch-Partenkirchen, 04. – 06. November 2003
[4] Lübke, L.: Validation of CFD Results behind the Working Propeller of a Ship Model, 7th Numerical Towing Tank Symposium, Hamburg, 03.-05. October 2004
[5] Lübke, L., Mach, K.-P.: LDV Measurements in the Wake of the Propelled KCS Model and its Use to Validate CFD Calculations, 25th Symposium on Naval Hydrodynamics, St. John’s, Newfoundland and Labrador, Canada, 08-13 August 2004
[6] Lübke, L.: Berechnung des effektiven Nachstromfeldes der Großausführung, 11. SVA-Forum, Potsdam, 09.11.2004
[7] Lübke, L.: Formoptimierung unter Berücksichtigung der Charakteristik des Nachstromfeldes, 4. SVA Forschungsforum „Theoria cum praxi“, Potsdam, 27.01.2011

Measurement Systems

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Curabitur eu massa vitae turpis laoreet molestie in eu velit. Nunc in condimentum nisl. Suspendisse potenti. Nullam ante ex, varius nec dignissim faucibus, suscipit vel eros. Aliquam condimentum nisi sit amet est vestibulum tincidunt. Quisque nisl enim, tempor in porttitor sed, ornare ac massa. Mauris sed convallis nisl. Aenean volutpat finibus turpis. Ut porta sagittis ligula congue vestibulum.

Cargo Ships

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Frachtschiff
Frachtschiff in der Schleppinne

Using the latest measurement technology with the highest accuracy, all cargo ship types of any size can be studied. These range from inland barges to the largest container ships and bulk carriers. In the 280 meter long towing tank, resistance, propulsion and open water tests are carried out to create power and speed predictions. During the trials it is possible to determine the EEDI Index according to the resolution Mepc.214 (63) (2012 Guidelines on Survey and Certification of the Energy Efficiency Design Index).

To make cargo ships safer and more efficient, the SVA Potsdam offers various services. Testing to optimise the propeller rotation direction for multi screw ships as well as trim and rudder angle optimisation can result in significant power savings. For the design of a wake adjusted propeller, wake measurements are performed on the model.

The seakeeping of the ship can be determined in regular and irregular sea states and in wave packets. A cavitation tunnel (Kempf & Remmers) with modern measurement technology is available for the study of the working propeller under cavitation similarity.

Wooden/GRP/PU Models

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WSSA_small_04

Modellfraese_small_05

Modellfraese_small_10

The ship model blanks are made from laminated slabs of abachi wood.

Waterjet Cutting System

The components are created with computer assistance and manufactured by means of a high-pressure waterjet cutting system (3500 bar). The machine cuts the parts very accurately and efficiently in rapid succession. The water absorption of the cut surface is very low and allows a further processing of the blanks after a drying time of one day. The machine has a working range of 2000 mm x 4000 mm and is also capable of cutting up to 120 mm thick steel.

 

5-Axis Milling Machine

The laminated ship blanks are completely machined on the Huber & Grimme 5-axis milling machine using coarse and fine milling operations, and thereby achieve a nearly perfect surface finish. With a one-time manual surface sanding after the milling process, the model is prepared for further processing. With the use of 5-axis milling machine, the requirements of the ITTC are met in terms of accuracy of model ships (± 1 mm, 0.5 % Lpp). The machine has a maximum working range of 8000 mm x 2500 mm x 1200 mm, a processing speed of up to 40 m/min. and a maximum speed of 24,000 rpm.

Wave Energy Conversion

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Curabitur eu massa vitae turpis laoreet molestie in eu velit. Nunc in condimentum nisl. Suspendisse potenti. Nullam ante ex, varius nec dignissim faucibus, suscipit vel eros. Aliquam condimentum nisi sit amet est vestibulum tincidunt. Quisque nisl enim, tempor in porttitor sed, ornare ac massa. Mauris sed convallis nisl. Aenean volutpat finibus turpis. Ut porta sagittis ligula congue vestibulum.