• Journal of the Korean Society of Visualization
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• v.12 no.1
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• pp.13-17
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• 2014

The growth of micro bubble has been simulated under the variation of ambient pressure. The Rayleigh-Plesset equation governs the dynamic growth and collapse of a bubble according to pressure and temperature conditions. The Rayleigh-Plesset equation was solved by 4th-order Runge-Kutta method for wide range of pressure variations. As numerical parameters, the pressure difference between initial and final pressures, and the temporal pressure gradient are changed. The results show that the pressure difference has little effect on the growth rate of the micro bubble in the inertia controlled growth region. On the other hand, the growth rate increases linearly with the increase of the pressure gradient.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.6
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• pp.731-738
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• 2010

Cavitation is described by formation and collapse of the bubbles in a liquid when the ambient pressure decreases. Formed bubbles grow and collapse by change of pressure, and when they collapse, shockwave by high pressure is generated. In general, bubble behavior can be described by Rayleigh-Plesset equation under adiabatic or isothermal condition and hence, phase shift by the pressure change in a bubble cannot be considered in the equation. In our study, a numerical model is developed from the mathematical model considering the phase shift from the previous study. In the developed numerical model, size of single spherical bubble is calculated by the change of mass calculated from the change of the ambient pressure in a liquid. The developed numerical model is verified by a case of liquid flow in a narrow channel.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.2 s.146
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• pp.177-185
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• 2006

Cavitation is the dominant noise source of the marine vehicle. Of the various types of cavitation , tip vortex cavitation is the first appearance type of marine propeller cavitation and it generates high frequency noise. In this study, tip vortex cavitation behavior and noise are numerically investigated. A numerical scheme using Eulerian flow field computation and Lagrangian particle trace approach is applied to simulate the tip vortex cavitation on the hydrofoil. Vortex flow field is simulated by combined Moore and Saffman's vortex core radius equation and Sculley vortex model. Tip vortex cavitation behavior is analyzed by coupled Rayleigh-Plesset equation and trajectory equation. The cavitation nuclei are distributed and released in the vortex flow result. Vortex cavitation trajectories and radius variations are computed according to nuclei initial size. Noise is analyzed using time dependent cavitation bubble position and radius data. This study may lay the foundation for future work on vortex cavitation study and it will provide a basis for proper underwater propeller noise control strategies.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1240-1247
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• 2003

Water jet nozzle for LCD has been used as a wet cleaning process in many industries. It is necessary for the nozzle to consider cleaning effect and flux. In this paper, we applied the bubble dynamic theory(Rayleight-Plesset equation) to improve the cleaning efficiency. Generally, Rayleigh-Plesset equations for cavitation bubbles are used in analyzing computer simulation for caviting flows. Burst of bubbles causes potential energies and we can use these energies to remove organic and inorganic compounds on the LCD. Therefore, it is necessary to analyze the bubble generations and axiomatic design by computational fluid dynamics(CFD). By comparing the weight matrix of neural networks to the design matrix of axiomatic design, we propose methods to verify designs objectively. The optimal solution could be deduced by the regression analysis using the design parameters.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.1-6
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• 2009

A flow analysis for the erosion-corrosion damaged automotive water pump which causes vehicle fire is numerically performed using the CFX program, computational fluid dynamics (CFD) code. The blade bending deformation and the blade clearance enlargement are considered in the analysis of performance reduction. For the cavitation analysis, the homogeneous multi phase model is adopted using the Ralyleigh-Plesset model for the rate equation controlling vapor generation and condensation.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.566-574
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• 2021

The process of cavitation involves generation, growth, coalescence, and collapse of small bubbles and is tremendously influenced by bubble-bubble interactions. To understand these interactions, a new cavitation model based on the transport equation is proposed herein. The modified Rayleigh-Plesset equation is analyzed to determine the bubble growth rate by assuming equal-sized spherical bubble clouds. The source term in the transport equation is then derived according to the bubble growth rate with the bubble-bubble interaction. The proposed model is validated by various test simulations, including microscopic bubble cloud evolution as well as macroscopical two- and three-dimensional cavitating flows. Compared with previous models, namely the Kunz and Zwart cavitation models, the newly proposed model does not require adjustable parameters and generally results in better predictions both microscopic and macroscopical cases. This model is more physical.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.550-555
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• 2000

Nonlinear oscillation of a microbubble under ultrasound was investigated theoretically. The bubble radius-time curves calculated by the Rayleigh-Plesset equation with a polytropic index and by the Keller-Miksis equation with the analytical solution for the Navier-Stokes equations of the gases were compared with the observed results by the light scattering method. This study has revealed that the bubble behavior such as the expansion ratio and the bouncing motion after the first collapse under ultrasound depends crucially on the retarded time of the bubble motion to the applied ultrasound.

• International Journal of Fluid Machinery and Systems
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• v.9 no.2
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• pp.119-128
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• 2016

This work presents the numerical investigation of an unsteady cavitating flow around a balancing drum of a multistage pump. The main attention is focused on the cavitation phenomena, which occur in the rear part of the drum clearance, cause the erosion of the drum material and influence the pressure losses and the flow rate through the clearance. The one-way coupling of the URANS equations and the full Rayleigh-Plesset equation is employed to analyse the flow field as well as the dynamics of cavitating bubbles. The numerical simulations show that the erosion processes are highly influenced by shaft vibrations, namely by periodic deformations of the annular clearance in time. The calculated results are verified by erosion tests on a real pump.

• The KSFM Journal of Fluid Machinery
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• v.17 no.3
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• pp.65-70
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• 2014

The effectiveness of a perforated plate installed additionally at butterfly valve to reduce cavitation which can cause vibration, noise, erosion, and flow path blockage has been investigated using CFD. Rayleigh-Plesset equation was applied to simulate cavitation phenomena. 3D flow simulations have been performed for 6 cases to consider the occurrence of cavitation at the downstream of the valve. From the present results, the perforated plate was thought to be very effective to suppress the cavitation inside of the pipe.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.2
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• pp.33-46
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• 2004

The cavitating noise of underwater propeller is considered numerically in this study. The main purpose of this research is to analyze these noise sources from marine propeller. The approach for investigation is a potential based panel method coupled with acoustic analogy. To predict propeller sheet cavitation noise, the blade surface cavity is considered as a single valued pulsating volume of vapor attached to the blade surface. The time dependent cavity volume data are used for noise prediction. Furthermore, we analyze hydrofoil cavitation bubble behavior and noise using Eulerian/Lagrangian approach. Through this study, we can analyze dominant noise source of marine propeller and provide a basis for proper noise control strategies.