Prediction of Cavitation Erosion Intensity Using Large-Scale Diesel Nozzles

An assessment of the cavitation erosion risk by using a contemporary unsteady Reynolds-averaged Navier–Stokes (URANS) method in conjunction with a newly developed postprocessing procedure is made for an NACA0015 hydrofoil and an NACA0018-45 hydrofoil, without the necessity to compute the details of the actual collapses. This procedure is developed from detailed investigations on the flow over a hydrofoil. It is observed that the large-scale structures and typical unsteady dynamics predicted by the URANS method with the modified shear stress transport (SST) k-ω turbulence model are in fair agreement with the experimental observations. An erosion intensity function for the assessment of the risk of cavitation erosion on the surface of hydrofoils by using unsteady RANS simulations as input is proposed, based on the mean value of the time derivative of the local pressure that exceeds a certain threshold. A good correlation is found between the locations with a computed high erosion risk and the damage area observed from paint tests.

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Static-pressure dependence of the cavitation erosion intensity in liquid oxygen

Ultrasonics ◽

10.1016/0041-624x(72)90305-8 ◽

1972 ◽

Vol 10 (5) ◽

pp. 239

Keyword(s):

Pressure Dependence ◽

Cavitation Erosion ◽

Static Pressure ◽

Liquid Oxygen ◽

Erosion Intensity

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Evaluation of Cavitation Erosion Intensity in a Microscale Nozzle Using Eulerian–Lagrangian Bubble Dynamic Simulation

Journal of Fluids Engineering ◽

10.1115/1.4042960 ◽

2019 ◽

Vol 141 (6) ◽

Cited By ~ 1

Author(s):

Masoud Khojasteh-Manesh ◽

Miralam Mahdi

Keyword(s):

Cavitation Erosion ◽

Bubble Dynamics ◽

Three Dimensional ◽

Bubble Surface ◽

Initial Position ◽

Bubble Collapse ◽

Lagrangian Analysis ◽

Two Phase ◽

The Impact ◽

Erosion Intensity

In the present study, cavitation erosion is investigated by implementing an Eulerian–Lagrangian approach. Three-dimensional two-phase flow is simulated in a microscale nozzle using Reynolds-averaged Navier–Stokes (RANS) solver along with realizable k−ε turbulence model and Schnerr–Sauer cavitation model. The numerical results are in agreement with experimental observations. A modified form of Rayleigh–Plesset–Keller–Herring equation along with bubble motion equation is utilized to simulate bubble dynamics. Average values of mixture properties over bubble surface are used instead of bubble-center values in order to account for nonuniformities around the bubble. A one-way coupling method is used between Lagrangian analysis and RANS solution. The impact pressure resulted from bubble collapse is calculated for evaluation of erosion in diesel and soy methyl ester (SME) biodiesel in different situations. The results show that the initial size of the bubbles is an important factor for determining the intensity of erosion. So, the bubbles erosive power increases when their initial radius increases. It is also found that the intensity of erosion in diesel is much higher than that of biodiesel and this is because of the differences in fuels properties, especially in viscosity and vapor pressure. The effect of bubbles initial position on erosion intensity is also investigated in this study, and it is found that bubbles with the highest distance from sheet cavity termination have the highest contribution in erosion rate.

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Experimental Study of Mechanism of Silt Abrasion Influenced by Cavitation in Hydraulic Machinery

ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 1, Symposia – Parts A, B, C, and D ◽

10.1115/ajk2011-06040 ◽

2011 ◽

Author(s):

Tao Zhang ◽

CiChang Chen ◽

Dan Li ◽

DongLi Lv

Keyword(s):

Abrasive Wear ◽

Large Scale ◽

Cavitation Erosion ◽

Large Angle ◽

Solid Particles ◽

Bubble Collapse ◽

Small Scale ◽

Front Part ◽

Trailing Edge ◽

Experimental Conditions

Experiments of cavitation erosion, silt abrasion and their synergetic erosion on Al hydrofoils were made in a testing-section. The erosion depth on hydrofoils was measured, and results showed that the depth value increased gradually with the condition changed from silt abrasion to synergetic erosion (lie due to contemporary action of silt abrasion and cavitation bubble collapse) and meanwhile with the position changed form the front part to the trailing edge of hydrofoil. The microtopography on hydrofoils was observed under the three experimental conditions. The cavitation erosion results appeared as regular-shape pits which differed only in the number per unit area at different position. The silt abrasion patterns was uniform in characteristics around one fixed point on hydrofoil. From the front part to the trailing edge of hydrofoil, the main abrasive wear patterns changed from ploughing type to wedge type. Small scale ploughing or cutting type and large scale wedge type were the main erosion patterns of the synergetic erosion directly caused by solid particles. From the front part to the trailing edge of hydrofoil, the size of small and large scale abrasive wear patterns increased gradually. Combining the analysis and processing of cavitation structure with the silt abrasion and synergetic erosion patterns, a viewpoint about silt abrasion influenced by cavitation was put forward. During the stage of growth of attached cavity, the hydrofoil was eroded by solid particles at small angle as a result of solid particles subjected to cavitation nucleation being accelerated along the surface of hydrofoil, and the erosion patterns were dominated by ploughing or cutting type. During the stage of cavitation cloud collapse in main flow, the hydrofoil was eroded by impact abrasion of solid particles at large angle resulted from solid particles being accelerated to high velocity by micro-jet or pressure wave, and the dominating erosion pattern was wedge type.

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Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

International Astronomical Union Colloquium ◽

10.1017/s0252921100031493 ◽

1999 ◽

Vol 173 ◽

pp. 243-248

Author(s):

D. Kubáček ◽

A. Galád ◽

A. Pravda

Keyword(s):

Image Processing ◽

Large Scale ◽

Harvard College ◽

Oak Ridge ◽

Large Scale Structures ◽

Short Period Comet ◽

Short Period ◽

Scale Structures ◽

Harvard College Observatory ◽

Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

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Evolution of Large-Scale Coronal Structures

International Astronomical Union Colloquium ◽

10.1017/s0252921100024945 ◽

1994 ◽

Vol 144 ◽

pp. 29-33

Author(s):

P. Ambrož

Keyword(s):

Magnetic Field ◽

Field Line ◽

Large Scale ◽

Coronal Magnetic Field ◽

Source Surface ◽

Solar Cycles ◽

Characteristic Relationship ◽

The Magnetic Field ◽

Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

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Large-scale Motion of Solar Filaments

International Astronomical Union Colloquium ◽

10.1017/s0252921100064502 ◽

2000 ◽

Vol 179 ◽

pp. 205-208

Author(s):

Pavel Ambrož ◽

Alfred Schroll

Keyword(s):

Magnetic Flux ◽

Proper Motion ◽

Time Scale ◽

Large Scale ◽

Accuracy Of Measurements ◽

Solar Filaments ◽

General Movement ◽

Scale Motion ◽

Velocity Scatter

AbstractPrecise measurements of heliographic position of solar filaments were used for determination of the proper motion of solar filaments on the time-scale of days. The filaments have a tendency to make a shaking or waving of the external structure and to make a general movement of whole filament body, coinciding with the transport of the magnetic flux in the photosphere. The velocity scatter of individual measured points is about one order higher than the accuracy of measurements.

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Some applications of electron beam microanalysis techniques in VLSI process evaluation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010007463x ◽

1983 ◽

Vol 41 ◽

pp. 160-161

Author(s):

Simon Thomas

Keyword(s):

Integrated Circuits ◽

Process Evaluation ◽

Large Scale ◽

Technology Development ◽

Analytical Techniques ◽

Successful Implementation ◽

Analysis Of Failures ◽

Characterization Of Materials ◽

Circuits Vlsi

Trends in the technology development of very large scale integrated circuits (VLSI) have been in the direction of higher density of components with smaller dimensions. The scaling down of device dimensions has been not only laterally but also in depth. Such efforts in miniaturization bring with them new developments in materials and processing. Successful implementation of these efforts is, to a large extent, dependent on the proper understanding of the material properties, process technologies and reliability issues, through adequate analytical studies. The analytical instrumentation technology has, fortunately, kept pace with the basic requirements of devices with lateral dimensions in the micron/ submicron range and depths of the order of nonometers. Often, newer analytical techniques have emerged or the more conventional techniques have been adapted to meet the more stringent requirements. As such, a variety of analytical techniques are available today to aid an analyst in the efforts of VLSI process evaluation. Generally such analytical efforts are divided into the characterization of materials, evaluation of processing steps and the analysis of failures.

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