[Paper Review] Investigation of cloud cavitation passive control method for hydrofoils using Cavitating-bubble Generators (CGs)

Ebrahim Kadivar, Ould el Moctar|ArXiv.org|Aug 4, 2018

Cavitation Phenomena in Pumps17 citations

TL;DR

This study proposes a passive control method for unsteady cloud cavitation on hydrofoils using Cavitating-Bubble Generators (CGs), employing a PANS turbulence model coupled with a mass transfer model in OpenFOAM. Results show that optimized CGs significantly reduce force fluctuations, turbulent velocity fluctuations, and pressure amplitude, while modifying the boundary layer to suppress cavitation damage.

ABSTRACT

In this article, we propose a passive method to control unsteady cloud cavitation on hydrofoils using cavitation-bubble generator (CGs). This method may be used in many engineering applications, in particular in marine and turbomachinery. First, we used a Partially-averaged Navier Stokes (PANS) model for turbulence to simulate the unsteady cavitating flow and validated it based on experimental data. This model was coupled with a mass transfer model and implemented to the open source software package OpenFOAM. Second, the effect of a proper design of CGs on qualitative parameters such as cavitation structure and the shape of cavity were studied. The effect of CGs on the destructive effects of cavitation such as vibration, turbulent velocity fluctuations and high- pressure amplitude were analyzed. Our results showed that a proper design of CGs may reduce the amplitude of the force fluctuations on the hydrofoil substantially. Further on, the local boundary layer around the hydrofoil surface was altered and the turbulent velocity fluctuation was reduced significantly using this technique.

Motivation & Objective

• To develop a passive method for controlling unsteady cloud cavitation on hydrofoils to mitigate its destructive effects.
• To investigate the influence of Cavitating-Bubble Generator (CG) design on cavitation structure and cavity shape.
• To analyze how CGs affect key cavitation-induced damage indicators: vibration, turbulent velocity fluctuations, and pressure amplitude.
• To validate the PANS-based cavitating flow simulation against experimental data for accuracy.
• To assess the impact of CGs on the local boundary layer development around the hydrofoil surface.

Proposed method

• Employed the Partially-Averaged Navier-Stokes (PANS) model to simulate unsteady cavitating flows with high accuracy.
• Coupled the PANS model with a mass transfer model to capture phase change dynamics in cavitating flows.
• Implemented the numerical model within the open-source CFD software OpenFOAM for computational simulation.
• Designed and numerically tested various CG configurations to evaluate their influence on cavitation development.
• Conducted parametric studies on CG geometry to optimize their placement and shape for maximum cavitation suppression.
• Validated the simulation results against experimental data to ensure reliability of the numerical approach.

Experimental results

Research questions

• RQ1 How does the placement and geometry of Cavitating-Bubble Generators (CGs) affect the structure and shape of the cavitation cloud on hydrofoils?
• RQ2 To what extent can CGs reduce unsteady force fluctuations caused by cloud cavitation?
• RQ3 How do CGs influence turbulent velocity fluctuations and pressure amplitude in cavitating flows?
• RQ4 What is the impact of CGs on the local boundary layer development near the hydrofoil surface?
• RQ5 Can the PANS model accurately predict cavitating flow behavior when validated against experimental data?

Key findings

• A properly designed Cavitating-Bubble Generator (CG) significantly reduces the amplitude of force fluctuations on the hydrofoil, indicating effective suppression of unsteady cavitation loads.
• The turbulent velocity fluctuations in the flow field were reduced substantially due to the presence and optimized design of CGs.
• The local boundary layer around the hydrofoil surface was altered in a way that contributed to reduced cavitation intensity and instability.
• The PANS model coupled with a mass transfer model provided accurate predictions of cavitating flow behavior when validated against experimental data.
• The CGs effectively modified the cavitation structure, leading to a more stable and less destructive cavity formation.
• High-pressure amplitude associated with cavitation collapse was notably reduced through strategic CG integration.