Session: 06-15-03 Unsteady Hydrodynamics, Vibrations, Acoustics and Propulsion - III

Submission Number: 180647

Numerical Prediction of Cavitation Inception on Marine Propellers 

Cavitation-free operations up to a certain ship speed are required for special-purpose ships to fulfill assigned missions due to noise signals and hull pressure pulses amplified by cavitating flows from marine propellers [1, 2]. There is a need for accurate predictions of cavitation inception speeds (CIS) in order to balance it on the suction and pressure sides of the propeller blade in a range of operating conditions for achieving optimum CIS. A numerical method based on CFD simulations is introduced for predicting cavitation inception curves for both sides of the blade and the numerical predictions are validated against experimental measurements from cavitation tunnel tests.

Detached-eddy simulations (DES) are applied to propeller and rudder models in the behind-hull condition with modeling multiphase flows and cavitation [3, 4]. Hull wake numerically modelled by an inlet boundary condition and momentum sources is applied to the propeller inflow. Cavitation simulations are made at an inception speed obtained from cavitation tunnel tests to derive a threshold value of the maximum cavity volume for determining CIS on a ship operation curve.

Fully-wetted flow simulations are made to predict inception curves based on an equivalent cavity volume corresponding to the volume of cells having pressure below the vapor pressure, as it requires excessively high computational effort to use cavitation simulations for predicting a number of inception points in a range of propeller loading conditions. Inception on the suction and pressure sides of the blade is predicted by considering different blade positions showing the minimum pressure on each side.

Two propellers designed for different ships are considered as test cases. One is a 5-bladed propeller with a large expanded area ratio and the other is a 4-bladed propeller with a high skew. Both propellers have been tested in the large-size cavitation tunnel of SSPA including a hull model for estimating inception curves. The test cases are used for validation of CFD cavitation simulations, numerical predictions of inception curves and propeller design optimization for increasing CIS.

REFERENCES

[1] ITTC. The specialist committee on cavitation induced pressure fluctuation: Final report and recommendations to the 22nd ITTC. Proc. of 22nd ITTC, Seoul/Shanghai, Korea/China, 1999.

[2] S. Shin, J.W. Hong, D. Nagarathinam, B.K. Ahn and S.G. Park. Tip vortex cavitation and induced noise characteristics of hydrofoils. Applied Sciences, 11, 5906, 2021.

[3] K.W. Shin and P. Andersen. CFD analysis of ship propeller thrust breakdown. Proc. of SMP’19, Rome, Italy, 2019.

[4] K.W. Shin and P. Andersen. Practical numerical method for erosion risk prediction on ship propellers. International Shipbuilding Progress, 67, 2020.

Presenting Author: Keun-Woo Shin Everllence

Presenting Author Biography: Currently a senior research engineer in Propeller & Aftship R&D Department in Everllence (2010-). CFD-based optimization of propeller and energy-saving devices related to propeller and cavitation simulations with focus on hull pressure pulses, erosion risk and underwater radiated noise as the research field. His PhD research (2007-2010) in Mechanical Engineering Department, Denmark Technical University on cavitation model development in RANS CFD solver and propeller cavitation analysis.

Authors:

Keun-Woo Shin Everllence
Mina Kim Chungnam National University
Byoung-Kwon Ahn Chungnam National University
Jens Ring Nielsen Everllence