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Einfluss von Maßstabseffekten auf die hydrodynamischen Eigenschaften von Düsenpropellern
Citation Link: https://doi.org/10.15480/882.15342
Publikationstyp
Doctoral Thesis
Date Issued
2025
Sprache
German
Author(s)
Advisor
Referee
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2025-06-26
Institute
TORE-DOI
Citation
Technische Universität Hamburg (2025)
Model tests are carried out to test the hydrodynamic performance of ships, particularly for high-cost systems. However, these test are limited, as the test facilities and the test costs, which must be kept as low as possible, only permit comparatively large scales and consequently small models with low inflow velocities. In open water tests, the speeds must be adapted to the mechanical load limits of the measurement systems and propellers. Due to the resulting Reynolds number effects, a Reynolds number correction of the test results is necessary. When carrying out experimental investigations, the aim is to realize fully turbulent boundary layer flow on the test models. However, if the boundary layer is only partially turbulent in the model scale, new methods must be developed which allow the conversion of the hydrodynamic parameters as a function of the position of the laminar-turbulent boundary layer transition. Therefore, the development and further development of Reynolds number correction methods is of fundamental importance in model testing. The work presented here deals with the development of a Reynolds number correction method for open water test results of ducted propellers with accelerating nozzles.
To isolate and better understand the physical effects, preliminary investigations were carried out using numerical flow calculations. Using a 2D- and a rotating 3D profile in a neutral, free-slip nozzle, the influence of the Reynolds number on the laminar/turbulent boundary layer and its effect on the drag and lift forces as well as the resulting relationships between lift and drag or propulsive force and torque were determined. CFD calculations of isolated propeller nozzles at different Reynolds numbers, in which the propeller effect was clearly defined by means of an actuator disk model, provided insights into the Reynolds number effects of the nozzles and their consequences for the propeller. It is shown that the formation of the boundary layer has a direct influence on the frictional and pressure forces.
Four propellers were selected for systematic model tests and manufactured in two scales each (D = 200 mm and D = 350 mm) as controllable pitch propellers. The propeller hub was designed in such a way that different propeller diameters could be realized by means of spacer plates on the propeller blade feet and thus different gap dimensions between the propeller tip and the inside of the nozzle could be realized with a constant nozzle diameter. This made it possible to carry out extensive free-running and paint flow tests with the propellers with different pitch, gap dimensions and Reynolds numbers in the SVA-Potsdam towing tank. Since only a small Reynolds number range can be covered in model tests, comprehensive CFD calculations were carried out with ducted propellers for a wide Reynolds number range. The CFD calculations were validated on the basis of a large number of test results. Series calculations of geometrically different propellers in the Wag. 19A nozzle over a wide Reynolds number range generated a data basis for the development of an empirical Reynolds number correction model. This made it possible to determine the Reynolds number effects for 50 propellers with different area ratios, pitch settings, tip loads due to pitch and chord length, gap dimensions and skew distributions at different operating points.
On the basis of this data, an empirical Reynolds number correction method for ducted propellers was developed for the most widely used Wag. 19A nozzle, in which both laminar-turbulent boundary layer effects and geometric propeller parameters are taken into account. The method makes it possible to determine the influence of the Reynolds number on the free running characteristics of ducted propellers as a function of geometric propeller parameters for the cavitation-free state.
To isolate and better understand the physical effects, preliminary investigations were carried out using numerical flow calculations. Using a 2D- and a rotating 3D profile in a neutral, free-slip nozzle, the influence of the Reynolds number on the laminar/turbulent boundary layer and its effect on the drag and lift forces as well as the resulting relationships between lift and drag or propulsive force and torque were determined. CFD calculations of isolated propeller nozzles at different Reynolds numbers, in which the propeller effect was clearly defined by means of an actuator disk model, provided insights into the Reynolds number effects of the nozzles and their consequences for the propeller. It is shown that the formation of the boundary layer has a direct influence on the frictional and pressure forces.
Four propellers were selected for systematic model tests and manufactured in two scales each (D = 200 mm and D = 350 mm) as controllable pitch propellers. The propeller hub was designed in such a way that different propeller diameters could be realized by means of spacer plates on the propeller blade feet and thus different gap dimensions between the propeller tip and the inside of the nozzle could be realized with a constant nozzle diameter. This made it possible to carry out extensive free-running and paint flow tests with the propellers with different pitch, gap dimensions and Reynolds numbers in the SVA-Potsdam towing tank. Since only a small Reynolds number range can be covered in model tests, comprehensive CFD calculations were carried out with ducted propellers for a wide Reynolds number range. The CFD calculations were validated on the basis of a large number of test results. Series calculations of geometrically different propellers in the Wag. 19A nozzle over a wide Reynolds number range generated a data basis for the development of an empirical Reynolds number correction model. This made it possible to determine the Reynolds number effects for 50 propellers with different area ratios, pitch settings, tip loads due to pitch and chord length, gap dimensions and skew distributions at different operating points.
On the basis of this data, an empirical Reynolds number correction method for ducted propellers was developed for the most widely used Wag. 19A nozzle, in which both laminar-turbulent boundary layer effects and geometric propeller parameters are taken into account. The method makes it possible to determine the influence of the Reynolds number on the free running characteristics of ducted propellers as a function of geometric propeller parameters for the cavitation-free state.
Subjects
Düsenpropeller
Reynoldszahl
Propulsion
Schiffbau
Reynoldszahleinfluss
Maßstabseffekte
DDC Class
623: Military Engineering and Marine Engineering
620.1: Engineering Mechanics and Materials Science
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