Cavitation Erosion in a Thin Film as Affected by the Liquid Properties

1971 ◽  
Vol 93 (4) ◽  
pp. 470-477 ◽  
Author(s):  
F. F. Tao ◽  
J. K. Appledoorn
Keyword(s):  
Thin Film ◽  
Cavitation Erosion ◽  
Environmental Control ◽  
Ambient Pressure ◽  
Atmospheric Environment ◽  
Bubble Collapse ◽  
Liquid Jets ◽  
Gas Solubility ◽  
Vapor Pressures ◽  
Reduced Pressures

The effect of liquid properties and the atmospheric environment on cavitation erosion was investigated in a thin film cavitation apparatus which consists of an ultrasonic horn with a flat tip vibrating against a stationary 1/2 in. ball at a frequency of 20 KC. The experimental results show that cavitation erosion is less severe for liquids of higher gas solubility or at vapor pressures greater than 100 torr. It is therefore possible to reduce the damage by blending a light component in lubricants or liquids and/or by environmental control. The effect of ambient pressure was also observed by tests in vacuum and under various reduced pressures up to one atmosphere. The damage increases with the increase of pressure. These results indicate that the most important factor in cavitation erosion is the differential pressure inside and outside the cavities, with the dissolved gases and/or vapor serving to control this pressure differential. The investigation of cavitation erosion with liquids of various properties also provides information for the understanding of the erosion mechanism. Evidence was obtained which supports the theory that the damage is caused by fatigue failure attributable to the impingement of liquid jets during bubble collapse. The liquid properties may control the jets velocity and thus affect the applied stress on surface boundaries.

Simulation of Laminar Liquid Jets in Gaseous Crossflow Before the Onset of Primary Breakup

2011 ◽  
Author(s):  
C.-L. Ng ◽  
K. A. Sallam
Keyword(s):  
Experimental Data ◽  
Fuel Injection ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Jet Breakup ◽  
Primary Breakup ◽  
Density Ratios ◽  
First Time ◽  
Two Sides ◽  
Reduced Pressures

The deformation of laminar liquid jets in gaseous crossflow before the onset of primary breakup is studied motivated by its application to fuel injection in jet afterburners and agricultural sprays, among others. Three crossflow Weber numbers that represent three different liquid jet breakup regimes; column, bag, and shear breakup regimes, were studied at large liquid/gas density ratios and small Ohnesorge numbers. In each case the liquid jet was simulated from the jet exit and ended before the location where the experimental data indicated the onset of breakup. The results show that in column and bag breakup, the reduced pressures along the sides of the jet cause the liquid to move to the sides of the jet and enhance the jet deformation. In shear breakup, the flattened upwind surface pushes the liquid towards the two sides of the jet and causing the gaseous crossflow to separate near the edges of the liquid jet thus preventing further deformation before the onset of breakup. It was also found out that in shear breakup regime, the liquid phase velocity inside the liquid jet was large enough to cause onset of ligament formation along the jet side, which was not the case in the column and bag breakup regimes. In bag breakup, downwind surface waves were observed to grow along the sides of the liquid jet triggered a complimentary experimental study that confirmed the existence of those waves for the first time.

scholarly journals A low-cost automized anaerobic chamber for long-term growth experiments and sample handling

2020 ◽  
Author(s):  
Achim J. Herrmann ◽  
Michelle M. Gehringer
Keyword(s):  
Environmental Control ◽  
Low Cost ◽  
Environmental Data ◽  
Atmospheric Environment ◽  
Regular Growth ◽  
Continuous Growth ◽  
Sample Handling ◽  
Hand Column ◽  
Oxygen Sensitive

1AbstractThe handling of oxygen sensitive samples and growth of obligate anaerobic organisms requires the stringent exclusion of oxygen, which is omnipresent in our normal atmospheric environment. Anaerobic workstations (aka. Glove boxes) enable the handling of oxygen sensitive samples during complex procedures, or the long-term incubation of anaerobic organisms. Depending on the application requirements, commercial workstations can cost up to 60.000 €. Here we present the complete build instructions for a highly adaptive, Arduino based, anaerobic workstation for microbial cultivation and sample handling, with features normally found only in high cost commercial solutions. This build can automatically regulate humidity, H2 levels (as oxygen reductant), log the environmental data and purge the airlock. It is built as compact as possible to allow it to fit into regular growth chambers for full environmental control. In our experiments, oxygen levels during the continuous growth of oxygen producing cyanobacteria, stayed under 0.03 % for 21 days without needing user intervention. The modular Arduino controller allows for the easy incorporation of additional regulation parameters, such as CO2 concentration or air pressure. This paper provides researchers with a low cost, entry level workstation for anaerobic sample handling with the flexibility to match their specific experimental needs.Specifications table[please fill in right-hand column of the table below]

The Nanostructure Fabrication on Conductive Diamond-like Carbon Thin Film by Nano-Oxidation Technique

2014 ◽  
Vol 939 ◽  
pp. 671-678
Author(s):  
Jen Ching Huang ◽  
Ho Chang ◽  
Hui Ti Ling
Keyword(s):  
Thin Film ◽  
Atomic Force Microscope ◽  
Applied Voltage ◽  
Processing Parameters ◽  
Atmospheric Environment ◽  
High Wear Resistance ◽  
Mold Material ◽  
Diamond Like Carbon ◽  
Atomic Force ◽  
Carbon Thin Film

This paper mainly focuses in the use of an atomic force microscope, research about the nanooxidation technique of conductive diamond-like carbon thin film in the atmospheric environment. The hardness, high wear resistance and chemical stability of diamond-like carbon thin film is high, and coefficient of friction is low, it is very suitable as a mold material for nanoscale mold. However, tool can only use a diamond cutter to machine the high hardness diamond-like carbon by traditional hard machining method, and tool life is not long. To overcome this drawback, the paper proposed an atomic force microscope (AFM) as a platform, a conductive AFM probe for tool under atmospheric conditions, and imposed nanooxidation technique on conductive diamond-like carbon thin film using electroluminescent etching to carry out nanofabrication processing. During the nanofabrication process, by changing the various processing parameters, such as applied voltage, repeated nanooxidation times and probe speed, etc., in order to understand the effect of processing parameters. The experimental results show, the nanooxidation technique can be carried out nanofabrication on conductive diamond-like carbon thin film successfully. And found that applied voltage, repeated nanooxidation times and probe speed all for the groove depth on the conductive diamond-like carbon thin films have significant influence. Additionally, this study successfully created a nanopattern. Therefore, the adequate machinability of DLC coating was achieved successfully in this study, indicating a promising application in the fabrication of nanopatterns on a nanoscale.

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.

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.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - The collapse of cavitation bubbles and the pressures thereby produced against solid boundaries

1966 ◽  
Vol 260 (1110) ◽  
pp. 221-240 ◽  
Keyword(s):  
Cavitation Erosion ◽  
Experimental Information ◽  
Liquid Jets ◽  
Steam Turbines ◽  
Jet Formation ◽  
Cavitation Damage ◽  
Cavity Collapse ◽  
New Ideas ◽  
The Impact ◽  
Shape Changes

Our object is to present a broad review of this subject as a branch of hydrodynamics, referring both to the well known ‘implosion’ mechanism first analysed by Lord Rayleigh and, more particularly, to the recently perceived possibility that effects of equally great violence, such as to damage solid boundaries, may arise through the impact of liquid jets formed by collapsing cavities. In §2 a few practical facts about cavitation damage are recalled by way of background, and then in §3 the significance of available theoretical and experimental information about cavity collapse is discussed. The main exposition of new ideas is in §4, which is a review of the factors contributing to shape changes and eventual jet formation by collapsing cavities. Finally, in §5, some new experimental observations on the unsymmetrical collapse of vapour-filled cavities are presented.

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