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Item type:Publication, Access status: without files , Numerical and experimental investigation of the tip vortex flow induced by an elliptical foil(HAL science ouverte, 2024-11-13); ; ; ; This collaborative paper within the AVT-320 joint research activity compares Computational Fluid Dynamics (CFD) results from diverse methods across research partners, validated against Experimental Fluid Dynamics (EFD) investigations in two test facilities. Focusing on non-cavitating tip vortex flows using an elliptical foil as a test case, the study reveals flow fluctuations and highlights the synergy between research institutions and advanced measurement technologies. The evaluation of CFD methods, including hybrid RANS/LES-numerical approaches, provides insights into turbulence modeling for tip vortex flows. Strong interactions between the tip region and trailing edge flow are observed, contributing to refining our understanding of these complex fluid dynamics. The study includes a comprehensive analysis of the tip vortex behavior of the the elliptical foil NACA 662-145, which has been investigated over the past three decades. The collected data encompasses the distribution of 19 flow variables on 17 cross sections, with a detailed analysis and comparison performed on four planes. Experimental results elucidate the effects of wandering correction on variable distribution. Two approaches to model turbulence are employed in CFD computations: scale-resolved simulation models to characterise the local flow and the eddy viscosity-based k − ω SST model. The hybrid turbulence model ensures consistency in velocity and pressure in the core region, serving as a robust reference for cavitation inception.Publicationtype: Working Paper73 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Design and analysis of a pumpjet propulsor for a ferry ship(Norwegian University of Science and Technology, Department of Marine Technology, 2024-04-04); ; ; ; The high efficiency of pumpjet propulsors recently favored their application to ships, different to usual high-speed vessels and submarines, to comply with the most recent regulations on efficiency, comfort onboard and noise pollution. In this context, as a part of the activity of the EU funded project SATURN, the design, and the performances of an axial pumpjet are investigated. The pumpjet of current study is designed to replace a conventional propeller of a ferry ship. To this aim a simulation-based design optimization method employing simplified RANSE analyses, synthetic wakes generated using body force distributions and a mixing-plane based coupling between rotor and stator is employed. Main geometrical characteristics (diameter, number of rotor and stator blades) as well as distributions of pitch, chord and camber are handled in the process by a parametric description of the geometry. A genetic algorithm guides towards the Pareto convergence of the designs by requiring the maximization of the propulsive efficiency at the lowest possible cavitation inception index. Fully unsteady RANSE calculations are finally employed to characterize the unsteady performances (thrust and torque) in behind conditions including the cavitation pattern and the induced pressure pulses on the ship stern, and results are discussed and compared to those of the reference conventional propeller.Publicationtype: Conference Paper43 142 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Acoustic signature of a wetted propeller in the wake of a hydrofoil(Norwegian University of Science and Technology, Department of Marine Technology, 2024-04-04); ; Data from Large Eddy Simulations (LES) were exploited to compute the acoustic signature of a wetted propeller working in the wake of a hydrofoil at incidence angles of 0 deg, 10 deg and 20 deg. A computational grid consisting of 1.7 billion points was utilized in the framework of an immersed-boundary (IB) methodology to resolve the fluid dynamics. The Ffowcs-Williams & Hawkings (FWH) acoustic analogy was employed for the computation of the acoustic pressure from the hydrofoil-propeller system in post-processing. The results of the acoustic analysis show that the signature of the propeller is the highest in its upstream and downstream directions, while minima are located on the propeller plane in the direction aligned with the span of the hydrofoil. Also the influence of the incidence angle of the hydrofoil on the acoustic signature of the propeller is analyzed. It is reinforced at large angles, which produce separation phenomena on the suction side of the hydrofoil and enhance the loading component of the sound coming from the propeller blades operating in its wake.Publicationtype: Conference Paper19 161 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Experimental and numerical advances in underwater radiated noise prediction of cavitating propeller-hull combinations(International Commission for Acoustics (ICA), 2022-06); ; ; ; Propeller induced cavitation is the primary underwater radiated noise source of motorized shipping activities, which coincides with acoustic frequencies utilized by marine life and may therefore have negative impacts on the ecosystem. This paper is the conclusion of the research project ProNoVi introduced at ICA2019 and presents the final results of both experimental and numerical campaigns on a high-level for all participants. While propulsion related phenomena are analyzed based on evaluation of high-speed recordings, the focus lies on model and full scale comparisons of acoustic measurements with pressure pick-ups and hydrophones in the far-field. Accompanying simulations with active phase transition are undertaken, by employing high fidelity CFD methods with RANS and scale resolved DES or LES turbulence modelling. For different methods and setups, the emitted noise from the propeller and its slipstream, where induced vorticity and cavitation-dynamics play an important role, are compared for an openwater propeller case and several propeller-hull combinations. The analysis of these workflows on real propeller-ship combinations reveal adequate results, regarding comparability and reproducibility between different experimental and numerical setups and point to future opportunities for the improvement of accurate underwater noise predictions while saving numerical and experimental resources.Publicationtype: Conference Paper82 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Analysis Methods and Design Measures for the Reduction of Noise and Vibration Induced by Marine Propellers(Deutsche Gesellschaft für Akustik, 2019-09); ; ; ; The paper presents the ongoing work in the research project ProNoVi. The objective of the project is to improve the numerical and experimental methods for the prediction of noise and vibrations induced by a propeller operating behind ship hull in full-scale conditions. Based on the improved methods practical recommendations for the reduction of noise and vibration levels for diơerent classes of vessels are a further objective. The propeller cavitation noise is identified as the dominating noise source, which coincides with important frequencies of perception of marine fauna and thus may have negative impact on marine life. As a side eơect, reducing the noise under water will increase comfort and thus safety for crew and passengers on board. The project aims at delivering a better understanding of fundamental physical mechanisms related to turbulence, induced vorticity and cavitation dynamics, which play a decisive role in generation of tonal and broadband propeller noise. The project partners will give a joint presentation, focusing on state-of-the-art in the field, today’s challenges in both the experimental and numerical approaches, and how the ProNoVi project is addressing those. ProNoVi is funded by the European Union. Further information is available at www.martera.eu/projects/pronovi.Publicationtype: Conference Paper96