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

Research on the Tip Vortex Cavitation and Its Control of an Elliptical Hydrofoil
Kang Liu1, 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

ABSTRACT

Different with the sheet cavitation on the surface of propeller or foil, tip
vortex cavitation only slightly affects the hydrodynamic performanceand efficiency of power machineries (Liu. 2019). However, during thedevelopment of the tip vortex, the collapse of the cavitation bubble
produces a pressure pulsation and lead to greatly increasing of theworking noise. The noise will reduce the comfort of the ship, and evenmore, for military ships and submarine, the noise will expose them to theenemy's detection sonar, greatly reducing the concealment and safety of
the warships. In addition, when the flow develops backward to theambient region of the rudder, TVC also affects the usage of the rudder
and reduce its efficiency. And the attachment of the TVC bubble on therudder surface leads to the erosion of the rudder surface and reduce its
working life (Chen. 2019). Therefore, it is necessary to know themechanism of TVC and how to forecast and control it.

The tip vortex induced cavitation affects the performance of the thrusters
and causes noise radiation and vibration. Thus, it is desirable to know
how to predict and control the tip vortex cavitation (TVC) andunderstand its mechanism, which a full understanding has not yet beenachieved. In this work, we perform TVC simulation of wetted andcavitating flows around an elliptical hydrofoil with the cross section ofNACA0012 and try to control the cavitation inception by injecting water.
In order to capture the TVC induced by the hydrofoil, adaptive meshrefinement (AMR) method is used for the mesh refinement in the wakeregion, especially the tip vortex region. Two steps are undertaken, firstly,
to reveal the characteristics of the tip vortex and TVC, the simulations
are performed under the wetted flow and cavitating flow, respectively.
After that, we introduce the water injection method to reduce andsuppress the cavitation inception. The improved delayed Detached Eddy
Simulation (IDDES) turbulence modeling method and Schnerr-Sauer
cavitation model are applied to guarantee the accuracy and speed of theprediction. The lift coefficients in this paper agree fairly well with theexperimental data and the max error is 5.5%, which is acceptable inengineering field. Results show that the strong swirling flow of the tipvortex region is the main reason of TVC inception. Furthermore, thepresence of TVC will increase the dilatation and baroclinic torquecomponent of the tip vortex. And the injection of water has an obvious
suppression effect on the TVC inception.

In the research of tip vortex cavitation, scholars have done some works.
Ji et al. (2014) have studied the interaction between cavitation and vortex
with Delft Twist-11 hydrofoil. After analyzing the proportions of eachcomponent in the vorticity transport equation around tip vortex region, it
is found that the dilatation term increases significantly when cavitation
occurs, and its amplitude reaches the same level as the vortex stretchingterm. At the same time, Cheng et al. (2020) simulated the tip leakage
vortex of the NACA0009 hydraulic hydrofoil by Large Eddy Simulation(LES) method and obtained the same result.
Xie et al. (2021) have numerically studied the tip vortex flow around
NACA16-020 elliptical hydrofoil. Based on the interaction of cavitation,vortex, and turbulence analyzation, it is clearly shown that the cavitation
promotes the production of vorticity and increases the thickness ofboundary layer. To explore the effect of TVC on tip vortex, Ohta et al.
(2019) simulates cavitation at the turbulent boundary layer near the wallunder the condition of 𝑅𝑒 =2000-2600. The results show that whencavitation occurs, cavitation will impede the exchange of turbulent
kinetic energy, and reduce the momentum transfer from the vortex core
to other directions.

KEY WORDS: elliptical hydrofoil; tip vortex cavitation; waterinjection; adaptive mesh refinement; IDDESINTRODUCTION
Cavitation is the cyclic process of the formation, development andcollapse of cavitation bubbles during the vapor-liquid transformation.
For offshore machinery, it is a commonly occurring phenomenon.
During its working process, velocity acceleration is accompanied withpressure reduction, and so that the liquid will transit to the gaseous phase.
There are different types of cavitation according to the structures ofcavitation bubble (sheet, cloud, tip vortex cavitation, etc.). Among them,tip vortex cavitation (TVC) is a common type in marine rotatingmachineries. For example, propeller or elliptical hydrofoil generates tip
vortex cavitation when working at a high speed.

In recent years, the inhibitory effect of mass injection methods oncavitation is a hot issue. Chang et al. (2011) finds that by injecting wateror water-based polymer into the core zone of the tip vortex, TVC
generation can be effectively inhibited, and water injection reduces theflow instability in the vortex core area. Timoshevskiy et al. (2016)

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