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Author:Saari, Aino
Title:Hydrodynamic study on a ducted propeller in a large vessel by time-accurate self-propulsion simulation with Reynolds-Averaged Navier-Stokes -equations
Tutkimus suulakepotkurista isossa aluksessa hydrodynamiikan näkökulmasta käyttäen ajan suhteen tarkkaa itsepropulsiosimulointia Reynolds-keskiarvotetuilla Navier-Stokes -yhtälöillä
Publication type:Master's thesis
Publication year:2014
Pages:(13) + 74 s. + liitt. 19      Language:   eng
Department/School:Insinööritieteiden korkeakoulu
Main subject:Meritekniikka   (Kul-24)
Supervisor:Matusiak, Jerzy
Instructor:Lakatos, Miklos ; Ilkko, Juho
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201410042738
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  3822   | Archive
Keywords:ducted propulsion
power demand
self-propulsion simulation
time-accurate simulation
Chimera grid
suulakepotkuri
tehontarve
itsepropulsiosimulointi
CFD
RANS
ajansuhteen tarkka laskenta
Chimera hila
Abstract (eng):In this master's thesis the suitability of a ducted propeller on a large vessel is studied.
The study is done from the hydrodynamic point of view and aims at evaluating the effect of a ducted propulsion on the ship power demand when compared to a conventional propulsion system.
Based on the results obtained, it is decided whether the further investigations on the topic are advisable.

The study is done with a case vessel with the propeller Ka4-55 in duct 19A.
The hull form is modified from an existing hull form.
There are both model test and RANS-simulation results for the original vessel and they are used as a reference line.
The ducted propeller performance behind the vessel is studied by a time-accurate self-propulsion simulation with RANS-solver FINFLO.
The duct and propeller are modeled with the Chimera grid method.

Approximative results are obtained at the self-propulsion point of the modified vessel.
The rotation rate of the ducted propeller is significantly lower than that of the conventional propeller used in comparison and the power demand is higher.
FINFLO has tendency to overestimate the propeller torque if the computational grid is not dense enough.
When this is taken into account and a correction is made to the obtained torque value, the power demand of the ducted propeller is decreased.
Thus it is probable that with a duct and propeller optimized for the vessel in the case, an improvement in the power demand would be achieved.
However, the self-propulsion simulation with FINFLO has uncertainties and in order to obtain more reliable results, the self-propulsion tests should be done by other RANS-solvers or in model tests.
Abstract (fin):Tässä diplomityössä tarkastellaan suulakepotkurin sopivuutta suuren aluksen propulsiolaitteeksi.
Tutkimus tehdään hydrodynamiikan näkökulmasta ja sen tarkoituksena on selvittää suulakepotkurin vaikutus laivan tehontarpeeseen verrattuna tavanomaiseen avopotkuriin.
Saatujen tulosten perusteella päätetään, kannattaako jatkossa panostaa suulakepotkurien käyttöön suurissa aluksissa.

Tarkastelussa käytettiin potkuria Ka4-55 ja suulaketta 19A ja laivan runkomuoto saatiin muokkaamalla olemassa oleva runkomuoto suulakepotkurille sopivaksi.
Alkuperäisellä runkomuodolla tehtyjä RANS simulointeja ja mallikokeita pidettiin vertailukohtana.
Suulakepotkurin toimivuutta aluksen perässä testattiin itsepropulsiosimuloinnilla.
Simuloinnit tehtiin ajan suhteen tarkkana RANS-ratkaisija FINFLOlla.
Suulake ja potkuri mallinnettiin Chimera-hilalla.

Itsepropulsiosimuloinnista saatiin suuntaa-antavia tuloksia.
Potkurin pyörimisnopeus laski huomattavasti avopotkurin pyörimisnopeudesta ja potkurin tehontarve nousi.
FINFLOlla on taipumusta yliarvioida potkurimomentti, kun laskentahilan tiheys ei ole riittäävä.
Kun tämä otetaan huomioon ja potkurimomenttia korjataan, potkruin tehontarve on pienempi kuin avopotkurin tehontarve.
Siten on todennäköistä, että suulake-potkuri yhdistelmällä, joka on optimoitu kyseiselle alukselle, tehontarve tulee laskemaan.
On kuitenkin huomattava, että laskentatuloksiin liittyy epävarmuustekijöitä ja siten on tehtävä itsepropulsiosimulointeja muilla RANS-ratkaisijoilla tai itsepropulsiomallikoe ennen kuin voidaan tehdä varmoja johtopäätöksiä.
ED:2014-10-05
INSSI record number: 49798
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