Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Comparative Study on Wake Instabilities of a Propeller with and without Duct
Xidi Zhang1, Jianwei Wu2, Liushuai Cao1, Decheng Wan1*1

Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering,
Shanghai Jiao Tong University, Shanghai, China
2Wuhan Second Ship Design and Research Institute, Wuhan, China*Corresponding author

same time, it has been found in recent studies by Wang et al. (2019) andQin et al. (2021) that when the ducted propeller is arranged on a heavyduty ship, it is beneficial to reduce vibration, which is helpful to improve
the noise performance. In addition, with the development of underwater
unmanned vehicles, ducted propellers have been widely used due to theirresistance is in general increased to external sea conditions, antiinterference ability to maintain a stable heading, and protection of thepropeller to deal with complex underwater conditions. However, if
rubbish is sucked, the resistance performance is just worse, which is amajor disadvantage of the ducted propeller.
The hydrodynamic performance of ducted propellers is affected by manyfactors. Research on ducted propellers generally adopts changing asingle parameter to observe its influence on various performances ofducted propellers. Among them, Gaggero et al. (2017) studies exploredits influence on the hydrodynamic performance of the ducted propeller
by using different ducts, and Song et al. (2015) explored its influence on
the hydrodynamic performance of the ducted propeller by changing thegeometric parameters of the propeller such as the propeller shaft and thedisk surface ratio. Compared with open-water propellers, ducted
propellers have many special properties, and the flow characteristics ofthe flow field and the dynamics of wakes are also quite different fromthose of open-water propellers. There are few comparisons such as thestudy of Gong et al. (2021) between ducted propellers and open water
propellers.
There are some related researches on the analysis and research ofpropeller wake instability in China. Wang et al. (2021) carried out
numerical and experimental studies on the dynamic characteristics of thepropeller wake based on the delayed detached eddy simulation (DDES),
large eddy simulation (LES) and non-turbulence model simulation
methods, and particle image velocity measurement flow field test,
respectively, the triggering mechanism of propeller wake instability isanalyzed.
Heydari et al. (2020) used computational fluid dynamics (CFD)
numerical simulation methods to study the wake field behind thepropeller under different propulsion coefficients under open waterconditions. The local variables (velocity, pressure) and wake structure
characteristics are extensively analyzed using mean analysis, root meansquare analysis and Fourier analysis. When the advance coefficient J ishigh, the rotation of the entire propeller determines the fluctuation of theside force, and when the advance coefficient J is low, the rotation of aABSTRACT
Due to its special geometric shape and appropriate propeller and duct
design, ducted propeller has the characteristics of low noise, highefficiency, and ability to work normally under heavy load conditions,which are superior to ordinary propellers. The existence of the duct hasa significant impact on the open water performance, vortex structures, aswell as the instability of the wake evolution. In this paper, based on theKa4-70 propeller and 19A duct model, simulations of open water
propeller and a ducted propeller with tip clearance d = 1.01mm arecarried out. Firstly, open water simulations of the two conditions wereperformed. Numerical results of d=1.01mm ducted propeller werecompared with the experimental data to verify the accuracy of thesimulation. Four sets of meshes with different resolution and density
were used to undertake the grid independence study. Secondly, based on
the detached eddy simulation (DES) turbulence modelling method, threeadvance coefficients J = 0.2, 0.6 and 1.0 were simulated. The influenceof the duct on vortex structures was analyzed in detail. The measurement
points were set at y/R = 0.9, x/R = 0.25, 1.5, 3.6, and 6, of which the flow
field scalars were collected for spectrum analysis. Results show that theexistence of the duct has a significant effect on the wake structures of thepropeller.

KEY WORDS: ducted propeller; wake; instability; DES; tip clearance
INTRODUCTION
Ducted propeller is one of the special propellers. Compared with theopen water propeller, it has an external duct, and propeller is fixed in the
middle of duct with a two-dimensional hydrofoil in cross-section. In
general applications in the marine propulsion field, the results show thatduct can improve propeller’s thrust and torque and other propulsion
parameters, and can provide additional thrust under heavy load and low
speed conditions, thereby improving the propulsion efficiency of theducted propeller in given conditions. In addition, the duct also has asignificant optimization effect on the propeller flow field. The propeller
wake working behind ship has been significantly improved, so the main
engine power can be absorbed under some working conditions. At the3708