Influence of Cathodic and Anodic Currents on Cavitation Erosion

CORROSION ◽  
1993 ◽  
Vol 49 (11) ◽  
pp. 910-920 ◽  
Author(s):  
J. G. Auret ◽  
O. F. R. A. Damm ◽  
G. J. Wright ◽  
F. P. A. Robinson
Keyword(s):  
Corrosion Rate ◽  
Cavitation Erosion ◽  
Loss Rate ◽  
Mechanical Damage ◽  
Bubble Collapse ◽  
Volume Loss ◽  
Test Rig ◽  
Anodic Current ◽  
Cathodic Current ◽  
Geometrical Effects

Abstract A vibratory-type cavitation test rig was constructed to study the effect of polarizing currents applied to a cavitating body. The generation of gas by electrolysis reduced mechanical damage suffered by a cavitating body because of bubble collapse cushioning. However, the net effect on overall damage depended on several factors, including the intensity of mechanical attack, corrosion rate, and surface geometrical effects. A cathodic current was shown to always decrease of the total volume loss rate, but the volume loss rate sometimes was increased and sometimes was reduced in the anodic current range.

Quantitative Evaluation of Cavitation Erosion

1998 ◽  
Vol 120 (1) ◽  
pp. 179-185 ◽  
Author(s):  
Shuji Hattori ◽  
Hiroyuki Mori ◽  
Tsunenori Okada
Keyword(s):  
Impact Energy ◽  
Cavitation Erosion ◽  
Erosion Resistance ◽  
Impact Load ◽  
Bubble Collapse ◽  
Impact Loads ◽  
Volume Loss ◽  
Developed Pressure ◽  
Cavitation Erosion Resistance ◽  
The Impact

In order to evaluate the quantitative cavitation-erosion resistance of materials, a pressure-detector-installed specimen was developed, which can measure both the impact load produced by cavitation bubble collapse and the volume loss simultaneously. Test specimens (pressure-detection rod) used were nine kinds of metals and were exposed to vibratory cavitation. A linear relation was obtained for all materials between the accumulated impact energy ∑Fi2 calculated from the distribution of impact loads and the volume loss, independent of test conditions. Impact energy accumulated during the incubation period and the energy for a unit material removal in steady-state period were obtained from the relation. These values are very Important concerning quantitative erosion resistance evaluation. That is, when the distribution of impact loads is acquired for different cavitation conditions, the volume loss can be estimated. This idea was applied to the venturi cavitation erosion. The experimental results for venturi test corresponds well with the prediction using these impact energy values. It was concluded that the quantitative impact energy values of materials can be determined independent of the apparatus and the test condition by using the newly developed pressure-detector-installed specimen.

Scale Effects in Cavitation Erosion of Materials

2006 ◽  
Vol 113 ◽  
pp. 517-520
Author(s):  
Marek Szkodo
Keyword(s):  
Mathematical Model ◽  
Material Properties ◽  
Cavitation Erosion ◽  
Loss Rate ◽  
Scale Effects ◽  
Cavitation Resistance ◽  
Volume Loss ◽  
Cumulative Volume ◽  
Area And Volume

This work presents a mathematical model describing the cavitation erosion of materials. The model of cavitation erosion is based on Weibull’s distribution. The model describes the influence of material properties and also dimensions of the eroded area and volume of the eroded material on cavitation erosion curves i.e. cumulative volume loss and volume loss rate as a function of time of cavitation loading. In addition, there is a possibility to define cavitation resistance of materials, upon the base of the adduced model.

Comparison of Different Methods for the Evaluation of Cavitation Damaged Surfaces

2005 ◽  
Author(s):  
B. Bachert ◽  
G. Ludwig ◽  
B. Stoffel ◽  
S. Baumgarten
Keyword(s):  
Mass Loss ◽  
White Light ◽  
Cavitation Erosion ◽  
Evaluation Method ◽  
Three Dimensional ◽  
Special Device ◽  
Test Rig ◽  
Rotating Disc ◽  
White Light Interferometer ◽  
Initial Stage

The experimental data which will be presented in this paper are the results of the comparison between different methods for evaluating damaged surfaces by cavitation erosion. The different methods are partly working in the initial stage of cavitation erosion and partly at developed cavitation erosion, where mass loss occurs. The used test rig consists basically of a rotating disc with a diameter of 500 mm on which four holes are located. Each hole generates a cavitation zone while the disc is rotating. The test objects are material specimens made of copper. Copper was used as test material in respect to reasonable durations for the tests. The specimen can be implemented in the casing of the test rig directly across the rotating disc on the diameter where the holes are located. This rotating disc test rig generates a very aggressive type of cavitation, so that mass loss, of course depending on the tested material, will appear after relatively short durations. Also the initial stage of cavitation erosion can be observed. The used test rig is very interesting regarding the possibility to apply different measuring techniques to characterize the erosive aggressiveness of cavitation. These techniques are at first the so-called Pitcount-Method, which allows investigations of cavitation erosion in the initial stage. The second one is an acoustic method, which is based on a structure-borne noise sensor and a specially developed signal processing system. The third method is the measuring of mass loss of the material specimen after several time steps. With the help of a CCD-camera and special digital image processing software, images of different cavitation conditions were recorded. The information obtained from these images should serve as support for the evaluation of the other used methods. After the evaluation with the above mentioned methods, the specimens were evaluated with a special device which works with the help of a white light interferometer. With this evaluation method three-dimensional information can be obtained in respect to the actually eroded volume of the specimens. With this information the lost mass of the specimens could be calculated directly. Especially the comparison of the results obtained from the Pitcount-Method, which is a two-dimensional evaluation method, and the three-dimensional results of the white light interferometer is an important point of the work within this paper.

Cavitation erosion behavior of hydraulic concrete under high-speed flow

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xin Wang ◽  
Ting-Qiang Xie
Keyword(s):  
Cavitation Bubble ◽  
High Speed ◽  
Cavitation Erosion ◽  
Concrete Strength ◽  
Bubble Collapse ◽  
High Speed Flow ◽  
Content Type ◽  
Erosion Behavior ◽  
Hydraulic Concrete ◽  
Speed Flow

Purpose Cavitation erosion has always been a common technical problem in a hydraulic discharging structure. This paper aims to investigate the cavitation erosion behavior of hydraulic concrete under high-speed flow. Design/methodology/approach A high-speed and high-pressure venturi cavitation erosion generator was used to simulate the strong cavitation. The characteristics of hydrodynamic loads of cavitation bubble collapse zone, the failure characteristics and the erosion development process of concrete were investigated. The main influencing factors of cavitation erosion were discussed. Findings The collapse of the cavitation bubble group produced a high frequency, continuous and unsteady pulse load on the wall of concrete, which was more likely to cause fatigue failure of concrete materials. The cavitation action position and the main frequency of impact load were greatly affected by the downstream pressure. A power exponential relationship between cavitation load, cavitation erosion and flow speed was observed. With the increase of concrete strength, the degree of damage of cavitation erosion was approximately linearly reduced. Originality/value After cavitation erosion, a skeleton structure was formed by the accumulation of granular particles, and the relatively independent bulk structure of the surface differed from the flake structure formed after abrasion.

scholarly journals Comparison of multiphase models for computing shock-induced bubble collapse

2019 ◽  
Vol 30 (8) ◽  
pp. 3845-3877 ◽  
Author(s):  
Eric Goncalves Da Silva ◽  
Philippe Parnaudeau
Keyword(s):  
Blast Wave ◽  
Cavitation Erosion ◽  
Volume Fraction ◽  
Free Field ◽  
Three Dimensional ◽  
Strong Shock ◽  
Bubble Collapse ◽  
Multiphase Model ◽  
Content Type ◽  
Multiphase Models

Purpose The purpose of this paper is to quantify the relative importance of the multiphase model for the simulation of a gas bubble impacted by a normal shock wave in water. Both the free-field case and the collapse near a wall are investigated. Simulations are performed on both two- and three-dimensional configurations. The main phenomena involved in the bubble collapse are illustrated. A focus on the maximum pressure reached during the collapse is proposed. Design/methodology/approach Simulations are performed using an inviscid compressible homogeneous solver based on different systems of equations. It consists in solving different mixture or phasic conservation laws and a transport-equation for the gas volume fraction. Three-dimensional configurations are considered for which an efficient massively parallel strategy was developed. The code is based on a finite volume discretization for which numerical fluxes are computed with a Harten, Lax, Van Leer, Contact (HLLC) scheme. Findings The comparison of three multiphase models is proposed. It is shown that a simple four-equation model is well-suited to simulate such strong shock-bubble interaction. The three-dimensional collapse near a wall is investigated. It is shown that the intensity of pressure peaks on the wall is drastically increased (more than 200 per cent) in comparison with the cylindrical case. Research limitations/implications The study of bubble collapse is a key point to understand the physical mechanism involved in cavitation erosion. The bubble collapse close to the wall has been addressed as the fundamental mechanism producing damage. Its general behavior is characterized by the formation of a water jet that penetrates through the bubble and the generation of a blast wave during the induced collapse. Both the jet and the blast wave are possible damaging mechanisms. However, the high-speed dynamics, the small spatio-temporal scales and the complicated physics involved in these processes make any theoretical and experimental approach a challenge. Practical implications Cavitation erosion is a major problem for hydraulic and marine applications. It is a limiting point for the conception and design of such components. Originality/value Such a comparison of multiphase models in the case of a strong shock-induced bubble collapse is clearly original. Usually models are tested separately leading to a large dispersion of results. Moreover, simulations of a three-dimensional bubble collapse are scarce in the literature using such fine grids.

Corrosion Susceptibility of a 0.35%C Steel in Seawater Electrolyte Using the Electrochemical Method

2016 ◽  
Vol 27 ◽  
pp. 20-26
Author(s):  
Ayodele Samuel Adeniyi ◽  
Mary Ajimegoh Awotunde
Keyword(s):  
Corrosion Rate ◽  
Linear Polarization ◽  
Electrode Potential ◽  
Electrochemical Method ◽  
Sea Water ◽  
Anodic Current ◽  
Potential Value ◽  
Heat Treated ◽  
Seawater Environment ◽  
Corrosion Susceptibility

The Tafel extrapolation and linear polarization methods were used as effective measures for determining the corrosion susceptibility of a spheroidized 0.35%C steel with sea water as the electrolyte. Eight pieces of steel were machined to length 5mm by 10mm in diameter. Two pieces each were heat treated at 600°C, 700°C and 800°C respectively and two pieces left as control. Electro-chemical experiments were carried out to obtain the best potential and anodic current of samples immersed in an electrolyte (seawater) at varying anodic potential of-0.7mv, -0.6mv, -0.5mv and-0.4mv respectively. The results showed that the sample with the least corrosion rate were the samples spheroidized at 700°C. They appeared to have the highest electrode potential value of-0.6mv and 800°C spheroidized samples had the least electrode potential value of-0.65mv at the end of 2000seconds respectively. From the results obtained, the samples spheroidized at 700°C appeared to be most suitable for seawater environment.

scholarly journals Aldegondabreen glacier change since 1910 from structure-from-motion photogrammetry of archived terrestrial and aerial photographs: utility of a historic archive to obtain century-scale Svalbard glacier mass losses

2020 ◽  
pp. 1-10
Author(s):  
Erik Schytt Holmlund
Keyword(s):  
Loss Rate ◽  
Aerial Photographs ◽  
Volume Loss ◽  
Entire Study Period ◽  
Elevation Change ◽  
Entire Study ◽  
Mass Losses ◽  
Elevation Data ◽  
Manual Processing ◽  
Insight Into

Abstract Photogrammetric reconstructions of the Aldegondabreen glacier on Svalbard from 17 archival terrestrial oblique photographs taken in 1910 and 1911 reveal a past volume of 1373.7 ± 78.2 · 106 m3; almost five times greater than its volume in 2016. Comparisons to elevation data obtained from aerial and satellite imagery indicate a relatively unchanging volume loss rate of − 10.1 ± 1.6 · 106 m3 a−1 over the entire study period, while the rate of elevation change is increasing. At this rate of volume loss, the glacier may be almost non-existent within 30 years. If the changes of Aldegondabreen are regionally representative, it suggests that there was considerable ice loss over the entire 1900s for the low elevation glaciers of western Svalbard. The 1910/11 reconstruction was made from a few of the tens of thousands of archival terrestrial photographs from the early 1900s that cover most of Svalbard. Further analysis of this material would give insight into the recent history and future prospects of the archipelago's glaciers. Photogrammetric reconstructions of this kind of material require extensive manual processing to produce good results; for more extensive use of these archival imagery, a better processing workflow would be required.

Study of Quantitative Numerical Prediction of Cavitation Erosion in Cavitating Flow

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Naoya Ochiai ◽  
Yuka Iga ◽  
Motohiko Nohmi ◽  
Toshiaki Ikohagi
Keyword(s):  
Erosion Rate ◽  
Cavitation Erosion ◽  
Prediction Method ◽  
Cavitating Flow ◽  
Quantitative Prediction ◽  
Bubble Collapse ◽  
Coupled Analysis ◽  
Material Surface ◽  
Two Phase ◽  
Navier Stokes Equation

Cavitation erosion is a material damage phenomenon caused by the repeated application of impulsive pressure on a material surface induced by bubble collapse, and the establishment of a method by which to numerically predict cavitation erosion is desired. In the present study, a numerical quantitative prediction method of cavitation erosion in a cavitating flow is proposed. In the present method, a one-way coupled analysis of a cavitating flow field based on a gas-liquid two-phase Navier–Stokes equation (Eulerian) and bubbles in the cavitating flow by bubble dynamics (Lagrangian) is used to treat temporally and spatially different scale phenomena, such as the macroscopic phenomenon of a cavitating flow and the microscopic phenomenon of bubble collapse. Impulsive pressures acting on a material surface are evaluated based on the bubble collapse position, time, and intensity, and the erosion rate is quantitatively predicted using an existing material-dependent relationship between the impulsive energy (square of the impulsive force) and the maximum erosion rate. The erosion rate on a NACA0015 hydrofoil surface in an unsteady transient cavitating flow is predicted by the proposed method. The distribution of the predicted erosion rate corresponds qualitatively to the distribution of an experimental surface roughness increment of the same hydrofoil. Furthermore, the predicted erosion rate considering the bubble nuclei distribution is found to be of the same order of magnitude as the actual erosion rate, which indicates that considering bubble nuclei distribution is important for the prediction of cavitation erosion and that the present prediction method is valid to some degree.

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

Experimental Investigations Concerning Erosive Aggressiveness of Cavitation at Different Test Configurations

Volume 3 ◽  
2004 ◽  
Author(s):  
B. Bachert ◽  
M. Dular ◽  
S. Baumgarten ◽  
G. Ludwig ◽  
B. Stoffel
Keyword(s):  
Mass Loss ◽  
Cavitation Erosion ◽  
Evaluation Method ◽  
Experimental Investigations ◽  
Cavitating Flows ◽  
Test Rig ◽  
The Third ◽  
Long Duration ◽  
Initial Stage ◽  
Test Objects

The experimental results, which will be presented in this paper, demonstrate the significant influence of the flow velocity, respectively the rotational speed, on the erosive aggressiveness of cavitating flows. On two of the three investigated test objects, cavitation erosion can only be observed in the initial stage by the so-called pit-count evaluation method. Developed erosion with mass loss is impossible to measure because of the very long duration until mass loss appears. The third test rig generates a very aggressive type of cavitation, so that mass loss, depending on the tested material, will appear after relatively short durations. In addition, the initial stage of cavitation erosion can be observed. Three different techniques were applied to investigate cavitation erosion in the initial and developed stage. Thereby, the capability of methods to quantify erosive effects in dependence of influencing operating parameters has been proven.

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