Investigation on RANS prediction of propeller induced pressure pulses and sheet-tip cavitation interactions in behind hull conditions
Examensarbete för masterexamen
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|Type: ||Examensarbete för masterexamen|
|Title: ||Investigation on RANS prediction of propeller induced pressure pulses and sheet-tip cavitation interactions in behind hull conditions|
|Authors: ||Eloho, Kelvin Elo-Oghene|
|Abstract: ||Propeller blades’ cavitation is not only a significant cause of Underwater radiated
Noise (URN), but it is also detrimental to the propeller blades and ship
engines due to resulting erosion and vibrations, respectively. Over the years,
different approaches have been engaged to predict cavitation using viscous
flow methodologies accurately. However, the practicalities of these methodologies
have not been stamped.
Data from previous experiments in open-water, full and model scale are used
for verification. Details of the experimental approach used are not included
in this report. This thesis investigates propeller-induced pressure pulses and
resulting cavitation providing visuals of the cavities formed corresponding to
the pressure broadband spectra. In decades past, sheet cavitation has been
predicted more often in comparison to tip-vortex cavitation. However, this
thesis aims also to shed light on blade-tip cavitation, showing a detachment
from sheet to vortex cavitation from the propeller blade trailing edge tip.
The upstream wake on which the propeller works is simulated from the provided
ship hull. This is done by performing steady-state simulations. After
which, transient simulations are performed. The transient simulations comprise
the propeller’s rotations in cavitating and non-cavitating conditions.
The simulations aim to depict the real-life scenario by operating the propeller
in behind-hull conditions. However, the free surface and resulting kelvin waves
are neglected in this thesis.
The investigation analyses the accuracy of the approach used. Initially, the
wake field is predicted after which spectral analyses of the pressure pulses
are performed and compared to the experimental. The cavitating pattern is
also reviewed. The studies engaged in this report show the RANS methodology
provide a accurate prediction of the propeller rotation phenomenom in
non-cavitating conditions. However, the RANS approach requires a highly independent
and fine mesh to make correct predictions in cavitating conditions.
The power spectral densities predicted show disparities with the experimental
result. However, an analogous visualization of cavitation is achieved. The
predictions is highly dependent on the accurate ship-propeller wake prediction.|
|Keywords: ||cavitation;RANS;CFD;pressure pulses|
|Issue Date: ||2022|
|Publisher: ||Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper|
|Series/Report no.: ||2022:01|
|Collection:||Examensarbeten för masterexamen // Master Theses|
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