# A Study on the Effect of Cavitation on Ships' Propellers

Van Thuan Mai

► To cite this version:

Van Thuan Mai. A Study on the Effect of Cavitation on Ships' Propellers. Short Stay (SS) Program (Winter School) at Yokohama National University, Department of Systems Design for Ocean-Space Faculty of Engineering Yokohama National University, Yokohama, Japan., Feb 2019, Yokohama, Japan. hal-04503642

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Submitted on 13 Mar 2024

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# A Study on the Effect of Cavitation on Ships' Propellers

The University of Da Nang – University of Science and Technology

Faculty of Transportation Mechanical Engineering

Van Thuan Mai

Corresponding Author/ E-mail: maivanthuan996@gmail.com

**KEYWORDS:** Cavitation erosion, Corrosion, Damage, Ship Maneuvering, Stability, Ship Loading, Computational fluid dynamics, Hydrodynamics, Unsteady flows, Simulations, supercavitation.

## I. Abstract

The study of corrosion and cavitation on propellers holds significant importance in the maritime field in general, specifically ship operations. It contributes to the development of fundamental theories in the design process, aiding designers in analyzing conditions and making informed choices to optimize operational modes, thereby avoiding overloading and enhancing efficiency as such reducing the operation fee. Furthermore, erosion affects various aspects such as ship maneuverability, stability, and load distribution, and affects the ship's hydrodynamic coefficient while moving on the cruise. The investigation evaluates the importance of great significance and can be applied for predicting the corrosion on the surface of the propeller head where there is an important position for generating ship thrust, characteristics of dynamic, and estimating the efficiency of working with various suitable modes. This research advances our understanding, providing a robust scientific foundation for designing processes that maximize ship efficiency and operations.

## II. Research Method

To assess the performance of propellers, research typically involves tank experiments and software simulations. The tank experiments employ two methods: one tests a free propeller model, detached from the ship's hull, while the other evaluates the entire equipment assembly, with the propeller mounted behind the ship's hull and the first method is more commonly utilized. Additionally, evaluations are conducted concurrently using simulation software (Ansys, and STAR-CCM+) to compare of the results. The cavitation number, which is based on the rotational speed of the propeller, is defined as:

$$ \sigma_n = \frac{P_{re} - P_v}{0.5\rho(nD)^2} \qquad (1) $$

where $P_{ref}$ is the reference pressure, $P_v$ is the vapour pressure, $\rho$ is the density of water, $n$ is propeller rate of rotation and $\rho$ is the diameter of the propeller.

The equation for the advance coefficient and free stream fluid velocity are defined as:

$$ V_A = J \cdot n \cdot D, \quad J = \frac{P_A}{D} = \frac{V_A}{n \cdot D} \qquad (2,3) $$

where J the reciprocal coefficient of the propeller, and $V_A$ the speed of the propeller, respectively.

The propeller efficiency coefficient:

$$ \eta_p = \frac{K_T \cdot J}{K_Q \cdot 2\pi} \qquad (4) $$

$$ \text{With: } K_T = \frac{T}{\rho \cdot D^4 \cdot n^2}, \quad K_Q = \frac{Q}{\rho \cdot D^5 \cdot n^2} \qquad (5,6) $$

where $K_T$ the traction coefficient, and $K_Q$ the torque coefficient.

<figure><img src="image_2.png" /><figcaption>**Fig1:** a,b) Setup experimental and test diagram, c) Show the actual damage, and d,e,f) Simulation calculation results. Results are copyrighted in the reference papers below.</figcaption></figure>

## References

1) Trần Công Nghị. Lý Thuyết Tàu Tập 2-Tỉnh Học Và Động Lực Học Tàu Thủy NXB Hồ Chí Minh 2009.

2) Onur Usta, Batuhan Aktas, Matthias Maasch, Osman Turan, Mehmet Atlar, Emin Korkut. A study on the numerical prediction of cavitation erosion for propellers.

3) François Caille, Christophe Clanet, Jacques Magnaudet. Bubble capture by a propeller.

4) Bernd Budich Numerical Investigation of Ship-Propeller Cavitation with Full Description of Shock-Wave Dynamic.