Cavitation erosion of a single bubble in water as a kind of dynamic damage

2017 ◽  
Vol 231 (11) ◽  
pp. 1383-1389 ◽  
Author(s):  
Feng Cheng ◽  
Weixi Ji
Keyword(s):  
High Velocity ◽  
Cavitation Erosion ◽  
Water Pressure ◽  
Bubble Radius ◽  
Rotating Disk ◽  
Experimental Results ◽  
Single Bubble ◽  
Bubble Wall ◽  
Dynamic Damage ◽  
Disk Test

In this study, a rotating disk test rig was used for the cavitation test of the brass samples. A pit of single black dapple and a large pit of multiring black dapple were found on the sample surfaces after 30 h test. A cavitation model of the rotating disk test was further developed by applying a periodic water pressure into the Keller–Miksis equation, so as to obtain the bubble dynamic characteristics. A comparison with the available experimental results reveals that the velocity of the bubble wall is governed by the initial bubble radius, and the bubble collapsing mode has changed from single bubble compression with high velocity to multiple bubble compression, with a increase in the initial bubble radius. The results also show that the movement of the spherical bubble wall induces the formation of the micro-jet with high velocity, leading to cavitation erosion pits on the specimen surface in the rotating disk test, which are well verified by the present theoretical model as well as the available experimental results.

Assessment of resistance of non-metallic coatings to silt abrasion and cavitation erosion in a rotating disk test rig

Wear ◽  
1996 ◽  
Vol 194 (1-2) ◽  
pp. 149-155 ◽  
Author(s):  
J. Zhang ◽  
M.O.W. Richardson ◽  
G.D. Wilcox ◽  
J. Min ◽  
X. Wang
Keyword(s):  
Cavitation Erosion ◽  
Rotating Disk ◽  
Metallic Coatings ◽  
Test Rig ◽  
Disk Test

Numerical and experimental study on dynamic characteristics of cavitation bubbles

2018 ◽  
Vol 70 (6) ◽  
pp. 1119-1126
Author(s):  
Feng Cheng ◽  
Weixi Ji
Keyword(s):  
Theoretical Model ◽  
Dynamic Characteristics ◽  
Water Pressure ◽  
Bubble Radius ◽  
Bubble Wall ◽  
Content Type ◽  
Cavitation Bubbles ◽  
Perturbation Frequency ◽  
Bubble Evolution ◽  
Evolution With Time

Purpose Cavitation bubbles cannot be avoided in the hydraulic system. Because of instability of flow and variation of water pressure, the jet often occurs in a bubble collapse. This study aims to accurately predict the shape, velocity and time of the resulting jet, so as to inhibit cavitation erosion. Design/methodology/approach In the study, a theoretical model of cavitation bubbles in the water has been developed by applying a periodic water film pressure into the Rayleigh–Plesset equation. A fourth-order in time Runge–Kutta scheme is used to obtain an accurate computation of the bubble dynamic characteristics. The behavior of the proposed theory is further simulated in a high-speed photography experiment by using a cavitation bubble test rig. The evolution with time of cavitation bubbles is further obtained. Findings A comparison with the available experimental results reveals that the bubble evolution with time has a duration of about 0.3T0, that well predicts the expanding and compressing process of cavitation bubbles. The results also show that the initial bubble radius in the water influences the moving velocity of the bubble wall, whereas the perturbation frequency of the water pressure has less effect on the velocity of the bubble wall. Originality/value A theoretical model well predicts dynamic characteristics of cavitation bubbles. The bubble evolution with time has a duration of about 0.3T0, Initial bubble radius influences the velocity of bubble wall. Perturbation frequency has less effect on the velocity of bubble wall.

scholarly journals H2O maser emission from the Seyfert 2 galaxy IC 2560: evidence for a super-massive black hole and a probe for mass-accretion rate

2002 ◽  
Vol 206 ◽  
pp. 400-403
Author(s):  
Yuko Ishihara ◽  
Naomasa Nakai ◽  
Naoko Iyomoto ◽  
Kazuo Makishima ◽  
Phil Diamond ◽  
...  
Keyword(s):  
Black Hole ◽  
High Velocity ◽  
Accretion Rate ◽  
Rotating Disk ◽  
Massive Black Hole ◽  
Central Mass ◽  
Maser Emission ◽  
Mass Accretion Rate ◽  
Systemic Velocity ◽  
Velocity Drift

Our observations of H2O masers have detected some high-velocity features and a secular velocity drift of the systemic features in the Seyfert 2 Galaxy IC 2560. The high-velocity features were blue- and red-shifted from the systemic velocity of 220-420 km s−1 and 210-350 km s−1, respectively. The velocity of the systemic features drifted at a secular rate of 2.62 km s−1 yr−1. Assuming the existence of a compact rotating disk as in NGC 4258, IC 2560 possesses a nuclear disk with inner and outer radii of 0.07 pc and 0.26 pc, respectively, and a confined mass of 2.8 × 106M⊙ at the center, making the central density > 2.1 × 109M⊙ pc−3. Such a dense object cannot be a cluster of stars, and this strongly suggests that the central mass is a super-massive black hole. Since the 2-10 keV luminosity of IC 2560 is 1 × 1041 erg s−1, the mass accretion rate of the suggested black hole must be 2 × 10−5M⊙ yr−1.

Experimental Investigation of Particle Decontamination Efficiency in a Single-Bubble by Pool Scrubbing

2020 ◽  
Author(s):  
Kota Fujiwara ◽  
Yuki Nakamura ◽  
Kohei Yoshida ◽  
Akiko Kaneko ◽  
Yutaka Abe
Keyword(s):  
Nuclear Power ◽  
Particle Concentration ◽  
Source Term ◽  
Mechanistic Model ◽  
Particle Diameter ◽  
Fission Products ◽  
Decontamination Factor ◽  
Experimental Results ◽  
Single Bubble ◽  
Internal Particle

Abstract Nuclear power plant (NPP) safety has become a public issue since the Fukushima daiichi NPP accident. In order to evaluate the risks caused by severe accidents (SAs), it is very important to understand the on-site source term events. One of the important unsolved source term events is the decontamination efficiency of fission products (FPs) in the suppression chamber by pool scrubbing. Therefore, a mechanistic model to analyze the particle decontamination efficiency by pool scrubbing is highly regarded. Despite the demand, particle decontamination mechanism by pool scrubbing has never been understood due to the complexity of phenomena. In our experiment, we aim to develop a reliable mechanistic model to evaluate particle decontamination efficiency of pool scrubbing by conducting separate effect tests. As to obtain the fundamental process of particle decontamination from gas to liquid-phase, we focused on decontamination factor (DF) of particle from a single bubble. However, it is very difficult to calculate the initial particle concentration inside the bubble. Therefore, in our experiment, we developed a method to measure the internal particle concentration inside the bubble by combining image processing and particle measurement. By using the experimental results, we succeeded to obtain reasonable DF for glycerin particles and CsI particles as a simulant particle for FPs. From the experimental results, detailed particle decontamination efficiency for various submergence were measured. The results tend show that DF increase linearly as submergence increases which suggests that DF is constant on bubble rise region. Moreover, the fact that glycerin particle with larger particle diameter takes a higher value shows that particle diameter significantly affects DF.

scholarly journals The Application of Nonordinary, State-Based Peridynamic Theory on the Damage Process of the Rock-Like Materials

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
X. B. Gu ◽  
Q. H. Wu
Keyword(s):  
Geotechnical Engineering ◽  
Damage Model ◽  
Numerical Results ◽  
Experimental Results ◽  
Stress Change ◽  
Peridynamic Theory ◽  
Damage Process ◽  
Finite Distance ◽  
Point Bend ◽  
Dynamic Damage

Peridynamics has a great advantage over modeling the damage process of rock-like materials, which is assumed to be in a continuum interaction with each other across a finite distance. In the paper, an approach to incorporate classical elastic damage model in the nonordinary, state-based peridynamics is introduced. This method can model the dynamic damage process and stress change of rock-like materials. Then two instances about three-point bend experiment are simulated in the rock-like materials. Finally the conclusions are drawn that numerical results are close to the experimental results. So the method has a great predictable value in the geotechnical engineering.

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