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Item type:Publication, Access status: with files , Manoeuvring in shallow water – a comprehensive and detailed analysis of shallow-water effects on the manoeuvring behaviour of modern seagoing vesselsShip manoeuvring in shallow water is critical for safe navigation and the design of waterways. This study investigates the manoeuvring behaviour of a container ship and a bulk carrier using free-running model tests (scale 1:60) across a wide range of speeds and water depths, complemented by verified and validated CFD simulations. The results reveal a strong dependence on under-keel clearance, including pronounced speed effects, directional asymmetries, and regime-dependent trend reversals.Publicationtype: Doctoral Thesis97 10 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Einfluss von Maßstabseffekten auf die hydrodynamischen Eigenschaften von DüsenpropellernModel 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.Publicationtype: Doctoral Thesis64 67 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Investigation of hydrodynamic effects on controllable-pitch propellers during crash stop maneuversPublicationtype: Doctoral Thesis96 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Quantification of the cavitating propulsor-induced underwater sound pressure in the far-field as well as on the ship hull based on turbulence resolved flow simulations and acoustic analogyThe simulation of underwater radiated noise is previously studied with well-defined single acoustic sources or propellers in open water condition. In this work the finite volume method is explored to capture the acoustic sources by resolving turbulent length scales, specifically in the propeller slipstream, applying a Volume-of-Fluid two-phase treatment with the OpenFOAM Schnerr-Sauer model and combining it with the permeable surface Ffowcs-Williams-Hawkings acoustic analogy. Beginning with advanced test cases the noise of propulsor-hull combinations is evaluated and leads to good agreement with measurements.Publicationtype: Doctoral Thesis76 327 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Effects of corrosion on the local behavior of steel structures under tensile loadingPublicationtype: Doctoral Thesis166 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Untersuchung der Propeller-Ruder-Rumpf Interferenzen für unterschiedliche Heckkonfigurationen von Unterwasserfahrzeugen und deren Einfluss auf die dynamische Stabilität und Steuerfähigkeit(2022); The interactions of the control surfaces at the stern of underwater vehicles differ depending on the stern configuration. These interactions influence the dynamic stability and the turning behavior. The forecasting methods for the design come mainly from aviation and are not optimally adapted to underwater vehicles. In this work, the prognosis of the interactions and their proportions are examined with the help of numerical investigations and experimental methods and correction functions for established prognosis methods are developed.Publicationtype: Doctoral Thesis192 209 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Numerische Untersuchung des Manövrierverhaltens von Schiffen während des StoppmanöversThis thesis focuses on the stopping behavior of ships and presents a coefficient-based approach to numerically simulate the stopping maneuver by taking into account the change of the ship speed. The maneuvering coefficients are derived from numerical calculations with a RANS method including the interaction of propeller slip stream and ship at off-design conditions. The variation of thrust deduction is covered by appropriate maneuvering coefficients and a comparison to model tests of stopping maneuvers with limited degrees of freedom allows a validation of the simulation tool.Publicationtype: Doctoral Thesis325 1294 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Entwicklung einer numerischen Methode zur Vorhersage der hydroakustischen Schallabstrahlung von Schiffspropellern(2020-10-02); In this dissertation a method for the prediction of hydroacoustic sound emission of propellers in the early design stage is developed. The sound prediction is performed by a hybride approach. A boundary element method is used for flow calculation and the Ffowcs Williams-Hawkings-equation for hydroacoustic sound prediction, extended to considering reflections. The method is validated by a calculation of a propeller behind a ship. The calculated sound pressure levels does agree well with measured data. Additional the simulation results are compared with exisitng guidelines for processing of measurement data.Publicationtype: Doctoral Thesis555 747 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Combination of time-domain flooding and evacuation simulations(2019-11); This thesis aims to take further steps towards closing the gap between time-domain flooding and evacuation simulations. Time-Domain flooding simulations are a powerful tool to calculate the spread of floodwater throughout the vessel in damaged ship condition and provide useful insights into the flooding process and its influence on a ship`s stability. The ship`s motions are usually recorded as time logs of trim and heel. These motions shall serve as input to time-domain evacuation simulations of the same vessel in this project. Thus the author aims to gain a better understanding of evacuation as calculated under more realistic conditions than the current procedure of night and day cases in calm water intact conditions. The software used to perform the simulations is: NAPA for flooding and AENEAS for evacuation. Research is performed on a cruise vessel that was also part of the recent joint industry project eSAFE.Publicationtype: Master Thesis66 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Modellierung von Abgasturboladern zur Berechnung des dynamischen Verhaltens von SchiffsmotorenPublicationtype: Doctoral Thesis150