| 1. |
- Ge, Muye, 1991, et al.
(författare)
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Improved prediction of sheet cavitation inception using bridged transition sensitive turbulence model and cavitation model
- 2021
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Ingår i: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 9:12
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Tidskriftsartikel (refereegranskat)abstract
- Sheet cavitation inception can be influenced by laminar boundary layer flow separation under Reynolds numbers regimes with transitional flow. The lack of accurate prediction of laminar separation may lead to massive over-prediction of sheet cavitation under certain circumstances, including model scale hydrofoils and marine propellers operating at relatively low Reynolds number. For non-cavitating flows, the local correlation based transition model, γ − Reθ transition model, has been found to provide predictions of laminar separation and resulting boundary layer transition. In the present study, the predicted laminar separation using γ − Reθ transition model is bridged with a cavitation mass transfer model to improve sheet cavitation predictions on hydrofoils and model scale marine propellers. The bridged model is developed and applied to study laminar separation and sheet cavitation predictions on the NACA16012 hydrofoil under different Reynolds numbers and angles of attack. As a reference case, the open case of the PPTC VP1304 model scale marine propeller tested on an inclined shaft is studied. Lastly as an application case, the predictions of cavitation on a commercial marine propeller from Kongsberg is presented for model scale conditions. Simulations using the bridged model and the standard unbridged approach with k − ω SST turbulence model are performed using the open-source package OpenFOAM, both using the Schnerr–Sauer cavitation mass transfer model, and the respective results are compared with available experimental results. The predictions using the bridged model agree well compared to experimental measurements and show significant improvements compared to the unbridged approach.
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| 2. |
- Ge, Muye, 1991, et al.
(författare)
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Numerical investigation of propeller induced hull pressure pulses using RANS and IDDES
- 2021
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Ingår i: Proceedings of IX International Conference on Computational Methods in Marine Engineering.
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the numerical predictions of pressure pulses induced by a cavitating marine propeller operating in behind-hull condition in model scale. Simulations are performed using the commercial package Star-CCM+ using RANS and IDDES approaches. The predicted sheet cavitation agreed well compared to experimental recordings and the 1st- and 2ndorder blade passing frequency (BPF) pressure pulses also agreed well compared to measurements via pressure transducers mounted on the model scale ship hull. Tip vortex cavitation (TVC) bursting was observed in the experiments and predicted as well in the numerical simulations. A traveling re-entrant jet from blade leading edge to blade tip was predicted underneath the sheet cavity structure, and triggered the partly collapse of sheet cavitation and strong TVC dynamics. The hull pressure uctuations are found to be correlated with the rate of cavitation volume growth/shrinkage and the TVC dynamics are found generating high levels of higherorder BPF pressure pulses, according to the deduced TVC volume time series. Significant cavitation variations were recorded between blade passings and propeller revolutions in the experiments, while in the numerical predictions no noticeable cavitation difference was predicted, and the predicted 3rd- to 5th-order BPF pressure pulse tonal values are generally higher than experimental measurements. The cavitation variations in the experiments are suspected to be related with sheet cavitation inception rather than blade loading difference induced by wake dynamics.
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| 3. |
- Ge, Muye, 1991, et al.
(författare)
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Numerical investigation of tip vortex bursting and induced hull pressure pulses on a container vessel
- 2021
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Ingår i: Proceedings of the 11th International Symposium on Cavitation (CAV2021).
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Konferensbidrag (refereegranskat)abstract
- A rotating marine propeller generates pressure pulses on the hull above it. The dynamics of cavitation, especially the tip vortex cavitation (TVC) bursting and TVC destruction by sheet cavity collapse have been found to induce high levels of pressure pulses on the ship hull body. The present study is focused on the numerical prediction of propeller induced pressure pulses on the hull with analysis on the interactions between ship wake, sheet cavitation and TVC. The predicted 1st – 2nd order Blade Passing Frequency (BPF) agree well with experimental measurements and higher order BPF pressure pulses are reasonably predicted as well. The study shows that the re-entrant jet, which can be related to the propeller inflow and convex shaped sheet cavity closure line, plays an important role regarding sheet cavitation collapse as well as violent TVC dynamics, and induce significant levels of hull pressure pulses.
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| 4. |
- Ge, Muye, 1991
(författare)
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Numerical prediction of propeller induced hull pressure pulses and noise
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An operating marine propeller is one of the major sources inducing hull pressure pulses, onboard noise and vibration as well as underwater radiated noise. There are rising concerns of environmental impacts and comfort and welfare of passengers and crews due to these negative effects. Cavitation is a significant source of these effects, but it is typically inevitable if only the hydrodynamic efficiency of the propeller is optimized. To reduce the noise and the pressure pulses caused by the cavitation, a trade-off of the hydrodynamic efficiency should be made to design and optimize a propeller that possess both high hydrodynamic performance and low noise and hull pressure pulse generation. More accurate predictions are needed to identify the best trade-off between a high efficiency propeller design and a low pressure pulse and noise one. The study focuses on the numerical prediction of hull pressure pulses and radiated underwater noise using viscous CFD including the opensource package OpenFOAM and commercial package Star-CCM+. Numerical predictions are performed regarding different experimental configurations for determining hull pressure pulses and ship noise, including propellers mounted on inclined shafts and propellers operating behind ship hulls, under different scales and scaling laws with different operating conditions and Reynolds numbers. Non-cavitating propeller induced pressure pulses are generally lower in levels and rich in blade passing frequency comparing to cavitating conditions, with blade tip clearance as a major impact factor. For cavitating conditions the rate of cavity growth/shrinkage is found to play the dominating role generating pressure fluctuations. For certain model scale configurations, numerical predictions with ordinary approaches predict massive sheet cavity on propeller blades leading to pressure pulse prediction discrepancies comparing to experimental observations and measurements. These can be significantly improved by a developed bridged model considering laminar to turbulence transition. Tip vortex cavitation bursting is a common phenomenon found on propellers operating behind the ship hull and generating significant levels of pressure pulses. The phenomenon is numerically predicted with investigations of its generation mechanisms in relation to the propeller inflow, convex shaped sheet cavitation closure line and traveling re-entrant jet underneath the sheet cavity. Propeller induced noise prediction was studied using approaches focused on the FWH (Ffowcs Williams-Hawkings) acoustic analogy with incompressible input on permeable/porous data surface (PDS). Studies show this combination between incompressible input and FWH acoustic analogy can be erroneous, though using certain PDS placements and closer receivers the error can be reduced.
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