The link between Movability Number and Incipient Motion in river ...

African Journals Online (AJOL)

2009-06-05

Jun 5, 2009 ... d. Median sediment diameter (mm or m). D. Hydraulic mean depth (m) d/Y. Relative ... Motion as well as a new bedload transportation equation. Additional ... Incipient Motion, in the context of sediment transport in rivers, ...... Eng. Part 2 59 827-835. ... Report of the Environmental Research Center, University.

Hemolytic potential of hydrodynamic cavitation.

Science.gov (United States)

Chambers, S D; Bartlett, R H; Ceccio, S L

2000-08-01

The purpose of this study was to determine the hemolytic potentials of discrete bubble cavitation and attached cavitation. To generate controlled cavitation events, a venturigeometry hydrodynamic device, called a Cavitation Susceptibility Meter (CSM), was constructed. A comparison between the hemolytic potential of discrete bubble cavitation and attached cavitation was investigated with a single-pass flow apparatus and a recirculating flow apparatus, both utilizing the CSM. An analytical model, based on spherical bubble dynamics, was developed for predicting the hemolysis caused by discrete bubble cavitation. Experimentally, discrete bubble cavitation did not correlate with a measurable increase in plasma-free hemoglobin (PFHb), as predicted by the analytical model. However, attached cavitation did result in significant PFHb generation. The rate of PFHb generation scaled inversely with the Cavitation number at a constant flow rate, suggesting that the size of the attached cavity was the dominant hemolytic factor.

A theoretical study of hydrodynamic cavitation.

Science.gov (United States)

Arrojo, S; Benito, Y

2008-03-01

The optimization of hydrodynamic cavitation as an AOP requires identifying the key parameters and studying their effects on the process. Specific simulations of hydrodynamic bubbles reveal that time scales play a major role on the process. Rarefaction/compression periods generate a number of opposing effects which have demonstrated to be quantitatively different from those found in ultrasonic cavitation. Hydrodynamic cavitation can be upscaled and offers an energy efficient way of generating cavitation. On the other hand, the large characteristic time scales hinder bubble collapse and generate a low number of cavitation cycles per unit time. By controlling the pressure pulse through a flexible cavitation chamber design these limitations can be partially compensated. The chemical processes promoted by this technique are also different from those found in ultrasonic cavitation. Properties such as volatility or hydrophobicity determine the potential applicability of HC and therefore have to be taken into account.

Super-Cavitating Flow Around Two-Dimensional Conical, Spherical, Disc and Stepped Disc Cavitators

Science.gov (United States)

Sooraj, S.; Chandrasekharan, Vaishakh; Robson, Rony S.; Bhanu Prakash, S.

2017-08-01

A super-cavitating object is a high speed submerged object that is designed to initiate a cavitation bubble at the nose which extends past the aft end of the object, substantially reducing the skin friction drag that would be present if the sides of the object were in contact with the liquid in which the object is submerged. By reducing the drag force the thermal energy consumption to move faster can also be minimised. The super-cavitation behavioural changes with respect to Cavitators of various geometries have been studied by varying the inlet velocity. Two-dimensional computational fluid dynamics analysis has been carried out by applying k-ε turbulence model. The variation of drag coefficient, cavity length with respect to cavitation number and inlet velocity are analyzed. Results showed conical Cavitator with wedge angle of 30° has lesser drag coefficient and cavity length when compared to conical Cavitators with wedge angles 45° and 60°, spherical, disc and stepped disc Cavitators. Conical cavitator 60° and disc cavitator have the maximum cavity length but with higher drag coefficient. Also there is significant variation of supercavitation effect observed between inlet velocities of 32 m/s to 40 m/s.

Cavitation

International Nuclear Information System (INIS)

Anon.

1983-01-01

Cavitation in fluid machines or flow passages can cause loss of performance or material damage due to erosion. This conference reports the results of world-wide research into all aspects of the study of cavitation. Contents include: Cavitation effects in machinery such as pumps, water turbines, propellers and positive displacement machinery; Cavitation in structures, flow passages, valves, flow meters and bearings; Cavitation erosion, noise and instability effects; Cavitation inception; Developed flows; Supercavitating flows and machines; Fundamentals; Bubble dynamics and thermodynamics of cavitation in various fluids; Test facilities and methods of cavitation research and testing; Special instrumentation for cavitation studies, and standards and recommendations for cavitation or erosion

Some observations of tip-vortex cavitation

Science.gov (United States)

Arndt, R. E. A.; Arakeri, V. H.; Higuchi, H.

1991-08-01

Cavitation has been observed in the trailing vortex system of an elliptic platform hydrofoil. A complex dependence on Reynolds number and gas content is noted at inception. Some of the observations can be related to tension effects associated with the lack of sufficiently large-sized nuclei. Inception measurements are compared with estimates of pressure in the vortex obtained from LDV measurements of velocity within the vortex. It is concluded that a complete correlation is not possible without knowledge of the fluctuating levels of pressure in tip-vortex flows. When cavitation is fully developed, the observed tip-vortex trajectory flows. When cavitation is fully developed, the observed tip-vortex trajectory shows a surprising lack of dependence on any of the physical parameters varied, such as angle of attack, Reynolds number, cavitation number, and dissolved gas content.

Harness cavitation to improve processing

Energy Technology Data Exchange (ETDEWEB)

Pandit, A.G.; Moholkar, V.S. [Univ. of Bombay (India)

1996-07-01

Mention cavitation to most chemical engineers, and they undoubtedly think of it as an operational problem. Indeed, the rapid creation and then collapse of bubbles, which is after all what cavitation involves, can destroy pumps and erode other equipment. Cavitation, however, also can have a positive side--presuming it is designed for and not unplanned. In this article, the authors look at how cavitation can be harnessed to improve processes, and the mechanisms for inducing cavitation--ultrasonics and hydrodynamics--and their likely roles. Sonication, that is, the use of ultrasound, is the conventional approach for creating cavitation, and so they turn to it first. Over the past few years, a number of groups have attempted to solve the problem of scale-up and design of ultrasonic reactors. The authors review the systems that already exist and also explore a simpler and efficient alternative to the ultrasonic reactor, the hydrodynamic cavitation reactor.

Experimental research of a microjet cavitation

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Olšiak Róbert

2012-04-01

Full Text Available The paper presents some results of a cavitation research behind a micro-orifice. Investigated were the conditions of the origin of cavitation represented by parameters such as upstream pressure, downstream pressure, liquid temperature and cavitation number. Presented are also images of a cavitating microjet made by the high speed high definition camera RedLake Y3. Dimensions of a microjet are: diameter 0,3 mm; length 0,5 mm.

Properties of sound attenuation around a two-dimensional underwater vehicle with a large cavitation number

International Nuclear Information System (INIS)

Ye Peng-Cheng; Pan Guang

2015-01-01

Due to the high speed of underwater vehicles, cavitation is generated inevitably along with the sound attenuation when the sound signal traverses through the cavity region around the underwater vehicle. The linear wave propagation is studied to obtain the influence of bubbly liquid on the acoustic wave propagation in the cavity region. The sound attenuation coefficient and the sound speed formula of the bubbly liquid are presented. Based on the sound attenuation coefficients with various vapor volume fractions, the attenuation of sound intensity is calculated under large cavitation number conditions. The result shows that the sound intensity attenuation is fairly small in a certain condition. Consequently, the intensity attenuation can be neglected in engineering. (paper)

Effect of free-air nuclei on fully developed individual bubble cavitation

International Nuclear Information System (INIS)

Danel, F.; Lecoffre, Y.

1976-01-01

Fully developed individual-bubble cavitation was studied. Nuclei population and pressure distribution at the boundary of a cavitating converging-diverging test section were measured. It was shown that some cavitation tests can only yield valid results if the free air content of the water is known. During the initial stages of bubble growth the wall pressure in the cavitation region is lower than the vapor pressure. Wall pressure rises later. For a given cavitation number and flow velocity, the pressure distribution depends on the number of expanding bubbles on the hydrofoil. Minimum pressure coefficient depends only on the cavitation number, the flow velocity and the number of expanding bubbles present. Bubbles generate pressure pulses at the wall; combined effect of all such pulses is to shift the wall pressure away from the value that would be obtained at the same cavitation number if no cavitation was present. The greater the number of expanding bubbles, the more the wall pressure tends to approach the vapor pressure. An important result of the work is to pin-point free air contents of water tunnel which lead to correct scaling of cavitation flows [fr

Disintegration of materials by cavitating microjets

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Mlkvik M.

2013-04-01

Full Text Available In the paper is presented an investigation of material disintegration by cavitating microjets. Cavitating microjet develops behind the micro-orifice at high flow speeds, when local pressure drop initiates a cavitation phenomenon. Described is a method and presented are selected results of experiments. Experiments were carried out with 2 micro-orifices at different flow conditions (cavitation number, distance between sample and micro-orifice. Experiments are based on flow visualisation as well as on a character of material displacement.

Influence of cavitation bubble growth by rectified diffusion on cavitation-enhanced HIFU

Science.gov (United States)

Okita, Kohei; Sugiyama, Kazuyasu; Takagi, Shu; Matsumoto, Yoichiro

2017-11-01

Cavitation is becoming increasingly important in therapeutic ultrasound applications such as diagnostic, tumor ablation and lithotripsy. Mass transfer through gas-liquid interface due to rectified diffusion is important role in an initial stage of cavitation bubble growth. In the present study, influences of the rectified diffusion on cavitation-enhanced high-intensity focused ultrasound (HIFU) was investigated numerically. Firstly, the mass transfer rate of gas from the surrounding medium to the bubble was examined as function of the initial bubble radius and the driving pressure amplitude. As the result, the pressure required to bubble growth was decreases with increasing the initial bubble radius. Next, the cavitation-enhanced HIFU, which generates cavitation bubbles by high-intensity burst and induces the localized heating owing to cavitation bubble oscillation by low-intensity continuous waves, was reproduced by the present simulation. The heating region obtained by the simulation is agree to the treatment region of an in vitro experiment. Additionally, the simulation result shows that the localized heating is enhanced by the increase of the equilibrium bubble size due to the rectified diffusion. This work was supported by JSPS KAKENHI Grant Numbers JP26420125,JP17K06170.

Experimental investigation of hydrodynamic cavitation through orifices of different geometries

Science.gov (United States)

Rudolf, Pavel; Kubina, Dávid; Hudec, Martin; Kozák, Jiří; Maršálek, Blahoslav; Maršálková, Eliška; Pochylý, František

Hydrodynamic cavitation in single and multihole orifices was experimentally investigated to assess their hydraulic characteristics: loss coefficients, inception cavitation number, cavitation number for transition to supercavitation. Significant difference for singlehole and multihole orifices was observed in terms of the measured loss coefficient. It is significantly more effective to use multihole orifices, where energy dissipation is much lower.It was found that using scaling factor given by ratio of orifice thickness suggests linear behaviour of both loss coefficient and inception cavitation number. Orifices seem to be convenient choice as flow constriction devices inducing cavitation due to their simplicity.

Experimental investigation of hydrodynamic cavitation through orifices of different geometries

Directory of Open Access Journals (Sweden)

Rudolf Pavel

2017-01-01

Full Text Available Hydrodynamic cavitation in single and multihole orifices was experimentally investigated to assess their hydraulic characteristics: loss coefficients, inception cavitation number, cavitation number for transition to supercavitation. Significant difference for singlehole and multihole orifices was observed in terms of the measured loss coefficient. It is significantly more effective to use multihole orifices, where energy dissipation is much lower.It was found that using scaling factor given by ratio of orifice thickness suggests linear behaviour of both loss coefficient and inception cavitation number. Orifices seem to be convenient choice as flow constriction devices inducing cavitation due to their simplicity.

Hydrodynamic cavitation for sonochemical effects.

Science.gov (United States)

Moholkar, V S; Kumar, P S; Pandit, A B

1999-03-01

A comparative study of hydrodynamic and acoustic cavitation has been made on the basis of numerical solutions of the Rayleigh-Plesset equation. The bubble/cavity behaviour has been studied under both acoustic and hydrodynamic cavitation conditions. The effect of varying pressure fields on the collapse of the cavity (sinusoidal for acoustic and linear for hydrodynamic) and also on the latter's dynamic behaviour has been studied. The variations of parameters such as initial cavity size, intensity of the acoustic field and irradiation frequency in the case of acoustic cavitation, and initial cavity size, final recovery pressure and time for pressure recovery in the case of hydrodynamic cavitation, have been found to have significant effects on cavity/bubble dynamics. The simulations reveal that the bubble/cavity collapsing behaviour in the case of hydrodynamic cavitation is accompanied by a large number of pressure pulses of relatively smaller magnitude, compared with just one or two pulses under acoustic cavitation. It has been shown that hydrodynamic cavitation offers greater control over operating parameters and the resultant cavitation intensity. Finally, a brief summary of the experimental results on the oxidation of aqueous KI solution with a hydrodynamic cavitation set-up is given which supports the conclusion of this numerical study. The methodology presented allows one to manipulate and optimise of specific process, either physical or chemical.

The Frequency of Incipient Fires at the Savannah River Site

International Nuclear Information System (INIS)

Blanchard, A.

1999-01-01

Fire is a significant hazard in most industrial and nuclear facilities. As such it is important that adequate safeguards be provided to ensure a responsible level of safety. In determining this level of safety it is necessary to know three key parameters. These are the frequency of the incipient fire, the probability that a fire will grow from the incipient stage to cause the potential consequence, and the potential consequences (i.e., losses) from an unwanted fire. Consequence predictions have been modeled and evaluated extensively and can be readily confirmed by comparison with historic loss records. These loss records can also provide significant insight into the probability that given a fire it grows to create a defined consequence. The other key parameter, frequency, is the focus of this report. this report determines an alternative method for estimating Savannah River Site (SRS) building fire frequencies as a function of floor area to the linear method previously used. The frequency of an incipient fire is not easily derived from existing fire loss records. This occurs because the fire loss records do not make reference to the sample population. To derive an initiating frequency both the number of events (incipient fires) and the population (number of buildings and years in service) must be known. this report documents an evaluation that estimates the frequency of incipient fires in industrial and nuclear facilities. these estimates were developed from the unique historical record that has been maintained at the Savannah River Site

Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems

Science.gov (United States)

Ferrari, A.

2017-03-01

Cavitation is the transition from a liquid to a vapour phase, due to a drop in pressure to the level of the vapour tension of the fluid. Two kinds of cavitation have been reviewed here: acoustic cavitation and hydrodynamic cavitation. As acoustic cavitation in engineering systems is related to the propagation of waves through a region subjected to liquid vaporization, the available expressions of the sound speed are discussed. One of the main effects of hydrodynamic cavitation in the nozzles and orifices of hydraulic power systems is a reduction in flow permeability. Different discharge coefficient formulae are analysed in this paper: the Reynolds number and the cavitation number result to be the key fluid dynamical parameters for liquid and cavitating flows, respectively. The latest advances in the characterization of different cavitation regimes in a nozzle, as the cavitation number reduces, are presented. The physical cause of choked flows is explained, and an analogy between cavitation and supersonic aerodynamic flows is proposed. The main approaches to cavitation modelling in hydraulic power systems are also reviewed: these are divided into homogeneous-mixture and two-phase models. The homogeneous-mixture models are further subdivided into barotropic and baroclinic models. The advantages and disadvantages of an implementation of the complete Rayleigh-Plesset equation are examined.

Hydrodynamic cavitation in Stokes flow of anisotropic fluids

Science.gov (United States)

Stieger, Tillmann; Agha, Hakam; Schoen, Martin; Mazza, Marco G.; Sengupta, Anupam

2017-05-01

Cavitation, the nucleation of vapour in liquids, is ubiquitous in fluid dynamics, and is often implicated in a myriad of industrial and biomedical applications. Although extensively studied in isotropic liquids, corresponding investigations in anisotropic liquids are largely lacking. Here, by combining liquid crystal microfluidic experiments, nonequilibrium molecular dynamics simulations and theoretical arguments, we report flow-induced cavitation in an anisotropic fluid. The cavitation domain nucleates due to sudden pressure drop upon flow past a cylindrical obstacle within a microchannel. For an anisotropic fluid, the inception and growth of the cavitation domain ensued in the Stokes regime, while no cavitation was observed in isotropic liquids flowing under similar hydrodynamic parameters. Using simulations we identify a critical value of the Reynolds number for cavitation inception that scales inversely with the order parameter of the fluid. Strikingly, the critical Reynolds number for anisotropic fluids can be 50% lower than that of isotropic fluids.

Appearance of high submerged cavitating jet: The cavitation phenomenon and sono luminescence

Directory of Open Access Journals (Sweden)

Hutli Ezddin

2013-01-01

Full Text Available In order to study jet structure and behaviour of cloud cavitation within time and space, visualization of highly submerged cavitating water jet has been done using Stanford Optics 4 Quick 05 equipment, through endoscopes and other lenses with Drello3244 and Strobex Flash Chadwick as flashlight stroboscope. This included obligatory synchronization with several types of techniques and lenses. Images of the flow regime have been taken, allowing calculation of the non-dimensional cavitation cloud length under working conditions. Consequently a certain correlation has been proposed. The influencing parameters, such as; injection pressure, downstream pressure and cavitation number were experimentally proved to be very significant. The recordings of sono-luminescence phenomenon proved the collapsing of bubbles everywhere along the jet trajectory. In addition, the effect of temperature on sono-luminescence recordings was also a point of investigation. [Projekat Ministarstva nauke Republike Srbije, br. TR35046

Influence of Thermodynamic Effect on Blade Load in a Cavitating Inducer

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Kengo Kikuta

2010-01-01

Full Text Available Distribution of the blade load is one of the design parameters for a cavitating inducer. For experimental investigation of the thermodynamic effect on the blade load, we conducted experiments in both cold water and liquid nitrogen. The thermodynamic effect on cavitation notably appears in this cryogenic fluid although it can be disregarded in cold water. In these experiments, the pressure rise along the blade tip was measured. In water, the pressure increased almost linearly from the leading edge to the trailing edge at higher cavitation number. After that, with a decrease of cavitation number, pressure rise occurred only near the trailing edge. On the other hand, in liquid nitrogen, the pressure distribution was similar to that in water at a higher cavitation number, even if the cavitation number as a cavitation parameter decreased. Because the cavitation growth is suppressed by the thermodynamic effect, the distribution of the blade load does not change even at lower cavitation number. By contrast, the pressure distribution in liquid nitrogen has the same tendency as that in water if the cavity length at the blade tip is taken as a cavitation indication. From these results, it was found that the shift of the blade load to the trailing edge depended on the increase of cavity length, and that the distribution of blade load was indicated only by the cavity length independent of the thermodynamic effect.

Techniques of Ultrasound Cavitation Control

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S. P. Skvortsov

2015-01-01

Full Text Available The control methods of ultrasonic cavitation applied now within the range from 20 kHz to 80 kHz use either control of ultrasound source parameters (amplitude, acoustic power, etc. or control of one of the cavitation effects (erosion of materials, sonoluminescence, power of acoustic noise, etc.. These methods provide effective management of technological processes, however, make it impossible to relate the estimated effect with parameters of pulsations of cavitation bubbles. This is, mainly, due to influence of a number of uncontrollable parameters, in particular, such as temperature, composition of liquid, gas content, etc. as well as because of the difficulty to establish interrelation between the estimated effect and parameters of pulsations. As a result, in most cases it is difficult to compare controlled parameters of ultrasonic cavitation among themselves, and quantitative characteristics of processes become depending on the type of ultrasonic installation and conditions of their measurement.In this regard, methods to determine parameters of bubble pulsations through sounding a cavitation area by low-intensity laser radiation or to record cavitation noise sub-harmonics reflecting dynamics of changing radius of cavitation bubbles are of interest. The method of optical sounding, via the analysis of spectral components of a scattered signal recorded by a photo-detector, allows us to define a phase of the bubbles collapse with respect to the sound wave and a moving speed of the bubbles wall, as well as to estimate a cavitation index within the light beam section.The method to record sub-harmonicas of cavitation noise allows us to define parameters of pulsations, average for cavitation areas.The above methods allow us both to study mechanisms of cavitation action and to form quantitative criteria of its efficiency based on the physical processes, rather than their consequences and are convenient for arranging a feedback in the units using

Cavitation Generation and Usage Without Ultrasound: Hydrodynamic Cavitation

Science.gov (United States)

Gogate, Parag R.; Pandit, Aniruddha B.

Hydrodynamic Cavitation, which was and is still looked upon as an unavoidable nuisance in the flow systems, can be a serious contender as an alternative to acoustic cavitation for harnessing the spectacular effects of cavitation in physical and chemical processing. The present chapter covers the basics of hydrodynamic cavitation including the considerations for the bubble dynamics analysis, reactor designs and recommendations for optimum operating parameters. An overview of applications in different areas of physical, chemical and biological processing on scales ranging from few grams to several hundred kilograms has also been presented. Since hydrodynamic cavitation was initially proposed as an alternative to acoustic cavitation, it is necessary to compare the efficacy of both these modes of cavitations for a variety of applications and hence comparisons have been discussed either on the basis of energy efficiency or based on the scale of operation. Overall it appears that hydrodynamic cavitation results in conditions similar to those generated using acoustic cavitation but at comparatively much larger scale of operation and with better energy efficiencies.

Assessment of non-cavitated and cavitated carious lesions among 12- to 15-year-old government and private school children in Pune, Maharashtra, India.

Science.gov (United States)

Machale, Priyanka S; Hegde-Shetiya, Sahana; Shirahatti, Ravi; Agarwal, Deept

2014-01-01

The present cross-sectional study was conducted to assess and compare the mean number of non-cavitated (initial lesions, IL) and cavitated carious lesions (WHO criteria) per child in the permanent dentition and to correlate it with the plaque index among 12- to 15-year-old government and private school children. 481 schoolchildren aged 12-15 years were selected randomly by multistage random sampling from two government and two private schools. Demographic details were collected at the time of examination. Baseline plaque scores were recorded using the Silness and Löe plaque index. Immediately after brushing and drying the teeth, cavitated lesions were recorded based on WHO recommendations and non-cavitated lesions were recorded using the IL criteria of Nyvad et al and Fyffe et al. The mean number of surfaces with cavitated and non-cavitated lesions for government school children was 2.13 ± 2.98 and 3.21 ± 2.97, respectively, and 1.24 ± 1.86 and 3.08 ± 2.33 for private school children, respectively. WHO + IL surfaces among private school children were 4.33 ± 3.48 and in government school children 5.35 ± 4.45. There was a positive correlation of plaque score with IL (r = 0.63) and WHO+IL (r = 0.73). Non-cavitated lesions are about twice as common as cavitated carious lesions in school children. Government school children had a higher number of cavitated and non-cavitated carious lesions when compared with private school children.

Application of flat plate cavitation data to the analysis of limited cavitation from an isolated triangular surface protrusion

International Nuclear Information System (INIS)

Holl, J.W.

1985-01-01

Isolated surface roughness can cause significant localized pressure reductions which can lead to premature cavitation and degradation of the cavitation performance of a marine vehicle. The characteristic velocity theory was developed to analyze the limited cavitation characteristics of isolated surface protrusions. This theory is dependent upon knowing the boundary layer velocity profile in the vicinity of the roughness and the limited cavitation number for the roughness in a uniform stream. In the investigation described in this paper, the equation for triangular surface protrusions was determined experimentally by testing sharpedged flat plates in a water tunnel. These data were then employed in the characteristic velocity theory to calculate the cavitation characteristics of a triangular protrusion in a turbulent boundary layer for comparison with experimental data

Degradation of chlorocarbons driven by hydrodynamic cavitation

Energy Technology Data Exchange (ETDEWEB)

Wu, Z.L.; Ondruschka, B.; Braeutigam, P. [Institut fuer Technische Chemie und Umweltchemie, Friedrich-Schiller-Universitaet Jena, Jena (Germany)

2007-05-15

To provide an efficient lab-scale device for the investigation of the degradation of organic pollutants driven by hydrodynamic cavitation, the degradation kinetics of chloroform and carbon tetrachloride and the increase of conductivity in aqueous solutions were measured. These are values which were not previously available. Under hydrodynamic cavitation conditions, the degradation kinetics for chlorocarbons was found to be pseudo first-order. Meanwhile, C-H and C-Cl bonds are broken, and Cl{sub 2}, Cl{sup .}, Cl{sup -} and other ions released can increase the conductivity and enhance the oxidation of KI in aqueous solutions. The upstream pressures of the orifice plate, the cavitation number, and the solution temperature have substantial effects on the degradation kinetics. A decreased cavitation number can result in more cavitation events and enhances the degradation of chlorocarbons and/or the oxidation of KI. A decrease in temperature is generally favorable to the cavitation chemistry. Organic products from the degradation of carbon tetrachloride and chloroform have demonstrated the formation and recombination of free radicals, e.g., CCl{sub 4}, C{sub 2}Cl{sub 4}, and C{sub 2}Cl{sub 6} are produced from the degradation of CHCl{sub 3}. CHCl{sub 3} and C{sub 2}Cl{sub 6} are produced from the degradation of CCl{sub 4}. Both the chemical mechanism and the reaction kinetics of the degradation of chlorocarbons induced by hydrodynamic cavitation are consistent with those obtained from the acoustic cavitation. Therefore, the technology of hydrodynamic cavitation should be a good candidate for the removal of organic pollutants from water. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

Cavitating behaviour analysis of Darrieus-type cross flow water turbines

International Nuclear Information System (INIS)

Aumelas, V; Pellone, C; MaItre, T

2010-01-01

The aim of this paper is to study the cavitating behaviour of bare Darrieus-type turbines. For that, the RANS code CAVKA, has been used. Under non-cavitating conditions, the power coefficient and the thrusts calculated with CAVKA are compared to experimental values obtained in the LEGI hydrodynamic tunnel. Under cavitating conditions, for several cavitation numbers, the numerical power coefficients and vapour structures are compared to experimental ones. Different blade profiles and camber lines are also studied for non-cavitating and cavitating conditions.

Experimental investigation on cavitating flow shedding over an axisymmetric blunt body

Science.gov (United States)

Hu, Changli; Wang, Guoyu; Huang, Biao

2015-03-01

Nowadays, most researchers focus on the cavity shedding mechanisms of unsteady cavitating flows over different objects, such as 2D/3D hydrofoils, venturi-type section, axisymmetric bodies with different headforms, and so on. But few of them pay attention to the differences of cavity shedding modality under different cavitation numbers in unsteady cavitating flows over the same object. In the present study, two kinds of shedding patterns are investigated experimentally. A high speed camera system is used to observe the cavitating flows over an axisymmetric blunt body and the velocity fields are measured by a particle image velocimetry (PIV) technique in a water tunnel for different cavitation conditions. The U-type cavitating vortex shedding is observed in unsteady cavitating flows. When the cavitation number is 0.7, there is a large scale cavity rolling up and shedding, which cause the instability and dramatic fluctuation of the flows, while at cavitation number of 0.6, the detached cavities can be conjunct with the attached part to induce the break-off behavior again at the tail of the attached cavity, as a result, the final shedding is in the form of small scale cavity and keeps a relatively steady flow field. It is also found that the interaction between the re-entrant flow and the attached cavity plays an important role in the unsteady cavity shedding modality. When the attached cavity scale is insufficient to overcome the re-entrant flow, it deserves the large cavity rolling up and shedding just as that at cavitation number of 0.7. Otherwise, the re-entrant flow is defeated by large enough cavity to induce the cavity-combined process and small scale cavity vortexes shedding just as that of the cavitation number of 0.6. This research shows the details of two different cavity shedding modalities which is worthful and meaningful for the further study of unsteady cavitation.

Investigation of the cavitation fluctuation characteristics in a Venturi injector

International Nuclear Information System (INIS)

Xu, Yuncheng; Chen, Yan; Wang, Zijun; Zhou, Lingjiu; Yan, Haijun

2015-01-01

The suction flow rate in a Venturi injector increases to a maximum and appears to be unstable when critical cavitation occurs. This study analyzes changes in the cavitation length in high-speed videos of a Venturi injector with critical cavitation to find periodic fluctuations in the cavitation cloud. Pressure fluctuation measurements show a dominant low frequency fluctuation that is almost as large as the oscillation frequency seen visually for the same conditions. The variation of the cavitation numbers and the measured transient outlet pressure show that critical cavitation occurs in the Venturi injector when the peak-to-peak pressure difference is greater than a critical value. Moreover, when the cavitation numbers become very small in the cavitation areas, the peak-to-peak pressures begin to decrease. The relationship between the suction performance and the outlet pressure fluctuations has a significant inflection point which can be used to determine proper working conditions. These experimental statistics provide a pressure range based on the inlet and outlet pressures for which the improvement of suction performance will not substantially change the outlet pressure fluctuations. Both the high-speed photography and the pressure measurement show the periodic oscillations of the cavitation cloud in a Venturi injector and can be used to detect the occurrence of critical cavitation. (paper)

Investigation of the cavitation fluctuation characteristics in a Venturi injector

Energy Technology Data Exchange (ETDEWEB)

Xu, Yuncheng; Chen, Yan; Wang, Zijun; Zhou, Lingjiu; Yan, Haijun, E-mail: yanhj@cau.edu.cn [College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083 (China)

2015-04-15

The suction flow rate in a Venturi injector increases to a maximum and appears to be unstable when critical cavitation occurs. This study analyzes changes in the cavitation length in high-speed videos of a Venturi injector with critical cavitation to find periodic fluctuations in the cavitation cloud. Pressure fluctuation measurements show a dominant low frequency fluctuation that is almost as large as the oscillation frequency seen visually for the same conditions. The variation of the cavitation numbers and the measured transient outlet pressure show that critical cavitation occurs in the Venturi injector when the peak-to-peak pressure difference is greater than a critical value. Moreover, when the cavitation numbers become very small in the cavitation areas, the peak-to-peak pressures begin to decrease. The relationship between the suction performance and the outlet pressure fluctuations has a significant inflection point which can be used to determine proper working conditions. These experimental statistics provide a pressure range based on the inlet and outlet pressures for which the improvement of suction performance will not substantially change the outlet pressure fluctuations. Both the high-speed photography and the pressure measurement show the periodic oscillations of the cavitation cloud in a Venturi injector and can be used to detect the occurrence of critical cavitation. (paper)

Cavitation erosion - scale effect and model investigations

Science.gov (United States)

Geiger, F.; Rutschmann, P.

2015-12-01

The experimental works presented in here contribute to the clarification of erosive effects of hydrodynamic cavitation. Comprehensive cavitation erosion test series were conducted for transient cloud cavitation in the shear layer of prismatic bodies. The erosion pattern and erosion rates were determined with a mineral based volume loss technique and with a metal based pit count system competitively. The results clarified the underlying scale effects and revealed a strong non-linear material dependency, which indicated significantly different damage processes for both material types. Furthermore, the size and dynamics of the cavitation clouds have been assessed by optical detection. The fluctuations of the cloud sizes showed a maximum value for those cavitation numbers related to maximum erosive aggressiveness. The finding suggests the suitability of a model approach which relates the erosion process to cavitation cloud dynamics. An enhanced experimental setup is projected to further clarify these issues.

Measurement on the cavitating vortex shedding behind rectangular obstacles

International Nuclear Information System (INIS)

Hegedus, F; Hos, C; Pandula, Z; Kullmann, L

2010-01-01

Measurement results on the cavitating vortex shedding behind sharp-edged rectangular bodies are presented, intended to provide benchmark cases for the validation of unsteady cavitation models of CFD codes. Rectangular bodies of increasing aspect ratio (1, 2, 3 and 4) were used with a constant 25mm height (12.5% blockage ratio). The water velocity in the 0.2x0.05m test section of the channel was varied between 1 and 12 m/s resulting in a Reynolds number in the range of (0.4-3.5)x105. Pressure signals were measured at several locations, notably in the wake. Dominant frequencies and Strouhal numbers are reported from cavitation-free flow (classic von Karman vortex shedding) up to supercavitation as a function of the free-stream Reynolds number. The results are in good agreement with the literature in case of the square cylinder. We experienced a slight increase of the dominant Strouhal number with increasing aspect ratio. This result is somewhat inconsistent with the literature, in which a fall of the Strouhal number can be observed at side ratio 2. This may be the consequence of the different ranges of Reynolds numbers. It was also found that between the inception of cavitation and the formation of supercavitation the Strouhal number is not affected by cavitation.

Measurement on the cavitating vortex shedding behind rectangular obstacles

Energy Technology Data Exchange (ETDEWEB)

Hegedus, F; Hos, C; Pandula, Z; Kullmann, L, E-mail: hegedusf@hds.bme.h [Department of Hydrodynamic Systems, Budapest University of Technology and Economics Muegyetem rkp. 1, Budapest 1111 (Hungary)

2010-08-15

Measurement results on the cavitating vortex shedding behind sharp-edged rectangular bodies are presented, intended to provide benchmark cases for the validation of unsteady cavitation models of CFD codes. Rectangular bodies of increasing aspect ratio (1, 2, 3 and 4) were used with a constant 25mm height (12.5% blockage ratio). The water velocity in the 0.2x0.05m test section of the channel was varied between 1 and 12 m/s resulting in a Reynolds number in the range of (0.4-3.5)x105. Pressure signals were measured at several locations, notably in the wake. Dominant frequencies and Strouhal numbers are reported from cavitation-free flow (classic von Karman vortex shedding) up to supercavitation as a function of the free-stream Reynolds number. The results are in good agreement with the literature in case of the square cylinder. We experienced a slight increase of the dominant Strouhal number with increasing aspect ratio. This result is somewhat inconsistent with the literature, in which a fall of the Strouhal number can be observed at side ratio 2. This may be the consequence of the different ranges of Reynolds numbers. It was also found that between the inception of cavitation and the formation of supercavitation the Strouhal number is not affected by cavitation.

Cavitations synthesis of carbon nanostructures

International Nuclear Information System (INIS)

Voropaev, S

2011-01-01

Originally an idea of diamonds production by hydrodynamical cavitation was presented by academician E.M. Galimov. He supposed the possibility of nature diamonds formation at fast magma flowing in kimberlitic pipes during bubbles collapse. This hypothesis assumes a number of processes, which were not under consideration until now. It concerns cavitation under high pressure, growth and stability of the gas- and vapors bubbles, their evolution, and corresponding physical- and chemical processes inside. Experimental setup to reproduce the high pressure and temperature reaction centers by means of the cavitation following the above idea was created. A few crystalline nanocarbon forms were successfully recovered after treatment of benzene (C 6 H 6 ).

Effects of the number of inducer blades on the anti-cavitation characteristics and external performance of a centrifugal pump

International Nuclear Information System (INIS)

Guo, XiaoMei; Shi, GaoPing; Zhu, ZuChao; Cui, BaoLing

2016-01-01

Installing an inducer upstream of the main impeller is an effective approach for improving the anti-cavitation performance of a high speed centrifugal pump. For a high-speed centrifugal pump with an inducer, the number of inducer blades can affect its internal flow and external performance. We studied the manner in which the number of inducer blades can affect the anti-cavitation characteristics and external performance of a centrifugal pump. We first use the Rayleigh-Plesset equation and the mixture model to simulate the vapor liquid flow in a centrifugal pump with an inducer, and then predict its external performance. Finally, we tested the external performance of a centrifugal pump with 2-, 3- and 4-bladed inducers, respectively. The results show that the simulations of external performance in a centrifugal pump are in accordance with our experiments. Based on this, we obtained vapor volume fraction distributions for the inducer, the impeller, and in the corresponding whole flow parts. We discovered that the vapor volume fraction of a centrifugal pump with a 3- bladed inducer is less than that of a centrifugal pump with 2- or 4-bladed inducers, which means that a centrifugal pump with a 3-bladed inducer has a better external and anti-cavitation performance.

Cavitation noise studies on marine propellers

Science.gov (United States)

Sharma, S. D.; Mani, K.; Arakeri, V. H.

1990-04-01

Experimental observations are described of cavitation inception and noise from five model propellers, three basic and two modified, tested in the open jet section of the Indian Institute of Science high-speed water tunnel facility. Extensive experiments on the three basic propellers of different design, which included visualization of cavitation and measurements of noise, showed that the dominant type of cavitation was in the form of tip vortex cavitation, accompanied by leading edge suction side sheet cavitation in its close vicinity, and the resultant noise depended on parameters such as the advance coefficient, the cavitation number, and the propeller geometry. Of these, advance coefficient was found to have the maximum influence not only on cavitation noise but also on the inception of cavitation. Noise levels and frequencies of spectra obtained from all the three basic propellers at conditions near inception and different advance coefficient values, when plotted in the normalized form as suggested by Blake, resulted in a universal spectrum which would be useful for predicting cavitation noise at prototype scales when a limited extent of cavitation is expected in the same form as observed on the present models. In an attempt to delay the onset of tip vortex cavitation, the blades of two of the three basic propellers were modified by drilling small holes in the tip and leading edge areas. Studies on the modified propellers showed that the effectiveness of the blade modification was apparently stronger at low advance coefficient values and depended on the blade sectional profile. Measurements of cavitation noise indicated that the modification also improved the acoustic performance of the propellers as it resulted in a complete attenuation of the low-frequency spectral peaks, which were prominent with the basic propellers. In addition to the above studies, which were conducted under uniform flow conditions, one of the basic propellers was tested in the simulated

String cavitation formation inside fuel injectors

Science.gov (United States)

Reid, B. A.; Gavaises, M.; Mitroglou, N.; Hargrave, G. K.; Garner, C. P.; McDavid, R. M.

2015-12-01

The formation of vortex or ‘string’ cavitation has been visualised at pressures up to 2000 bar in an automotive-sized optical diesel fuel injector nozzle. The multi-hole nozzle geometry studied allowed observation of the hole-to-hole vortex interaction and, in particular, that of a bridging vortex in the sac region between the holes. Above a threshold Reynolds number, their formation and appearance during a 2 ms injection event was repeatable and independent of upstream pressure and cavitation number. In addition, two different hole layouts and threedimensional flow simulations have been employed to describe how, the relative positions of adjacent holes influenced the formation and hole-to-hole interaction of the observed string cavitation vortices, with good agreement between the experimental and simulation results being achieved.

Simulations of Steady Cavitating Flow in a Small Francis Turbine

Directory of Open Access Journals (Sweden)

Ahmed Laouari

2016-01-01

Full Text Available The turbulent flow through a small horizontal Francis turbine is solved by means of Ansys-CFX at different operating points, with the determination of the hydrodynamic performance and the best efficiency point. The flow structures at different regimes reveal a large flow eddy in the runner and a swirl in the draft tube. The use of the mixture model for the cavity/liquid two-phase flow allowed studying the influence of cavitation on the hydrodynamic performance and revealed cavitation pockets near the trailing edge of the runner and a cavitation vortex rope in the draft tube. By maintaining a constant dimensionless head and a distributor vane opening while gradually increasing the cavitation number, the output power and efficiency reached a critical point and then had begun to stabilize. The cavitation number corresponding to the safety margin of cavitation is also predicted for this hydraulic turbine.

Cavitation

CERN Document Server

Young, F Ronald

1999-01-01

First published by McGraw-Hill in 1989, this book provides a unified treatment of cavitation, a phenomenon which extends across the boundaries of many fields. The approach is wide-ranging and the aim is to give due consideration to the many aspects of cavitation in proportion to their importance. Particular attention is paid to the diverse situations in which cavitation occurs and to its practical applications.

Killing rate of colony count by hydrodynamic cavitation due to square multi-orifice plates

Science.gov (United States)

Dong, Zhiyong; Zhao, Wenqian

2018-02-01

Currently,in water supply engineering, the conventional technique of disinfection by chlorination is employed to kill pathogenic microorganisms in raw water. However, chlorine reacts with organic compounds in water and generates disinfection byproducts (DBPs), such as trihalomethanes (THMs), haloacetic acids (HAAs) etc. These byproducts are of carcinogenic, teratogenic and mutagenic effects, which seriously threaten human health. Hydrodynamic cavitation is a novel technique of drinking water disinfection without DBPs. Effects of orifice size, orifice number and orifice layout of multi-orifice plate, cavitation number, cavitation time and orifice velocity on killing pathogenic microorganisms by cavitation were investigated experimentally in a self-developed square multi-orifice plate-type hydrodynamic cavitation device. The experimental results showed that cavitation effects increased with decrease in orifice size and increase in orifice number, cavitation time and orifice velocity. Along with lowering in cavitation number, there was an increase in Reynolds shear stress,thus enhancing the killing rate of pathogenic microorganism in raw water. In addition, the killing rate by staggered orifice layout was greater than that by checkerboard-type orifice layout.

Microbubble Cavitation Imaging

Science.gov (United States)

Vignon, Francois; Shi, William T.; Powers, Jeffry E.; Everbach, E. Carr; Liu, Jinjin; Gao, Shunji; Xie, Feng; Porter, Thomas R.

2014-01-01

Ultrasound cavitation of microbubble contrast agents has a potential for therapeutic applications such as sonothrombolysis (STL) in acute ischemic stroke. For safety, efficacy, and reproducibility of treatment, it is critical to evaluate the cavitation state (moderate oscillations, stable cavitation, and inertial cavitation) and activity level in and around a treatment area. Acoustic passive cavitation detectors (PCDs) have been used to this end but do not provide spatial information. This paper presents a prototype of a 2-D cavitation imager capable of producing images of the dominant cavitation state and activity level in a region of interest. Similar to PCDs, the cavitation imaging described here is based on the spectral analysis of the acoustic signal radiated by the cavitating microbubbles: ultraharmonics of the excitation frequency indicate stable cavitation, whereas elevated noise bands indicate inertial cavitation; the absence of both indicates moderate oscillations. The prototype system is a modified commercially available ultrasound scanner with a sector imaging probe. The lateral resolution of the system is 1.5 mm at a focal depth of 3 cm, and the axial resolution is 3 cm for a therapy pulse length of 20 µs. The maximum frame rate of the prototype is 2 Hz. The system has been used for assessing and mapping the relative importance of the different cavitation states of a microbubble contrast agent. In vitro (tissue-mimicking flow phantom) and in vivo (heart, liver, and brain of two swine) results for cavitation states and their changes as a function of acoustic amplitude are presented. PMID:23549527

Microbubble Cavitation Imaging

OpenAIRE

Vignon, Francois; Shi, William T.; Powers, Jeffry E.; Everbach, E. Carr; Liu, Jinjin; Gao, Shunji; Xie, Feng; Porter, Thomas R.

2013-01-01

Ultrasound cavitation of microbubble contrast agents has a potential for therapeutic applications such as sonothrombolysis (STL) in acute ischemic stroke. For safety, efficacy, and reproducibility of treatment, it is critical to evaluate the cavitation state (moderate oscillations, stable cavitation, and inertial cavitation) and activity level in and around a treatment area. Acoustic passive cavitation detectors (PCDs) have been used to this end but do not provide spatial information.

Released air during vapor and air cavitation

Energy Technology Data Exchange (ETDEWEB)

Jablonská, Jana, E-mail: jana.jablonska@vsb.cz; Kozubková, Milada, E-mail: milada.kozubkova@vsb.cz [VŠB-Technical University of Ostrava, Faculty of Mechanical Engineering, Department of Hydromechanics and Hydraulic Equipment, 17. listopadu 15, 708 33 Ostrava-Poruba (Czech Republic)

2016-06-30

Cavitation today is a very important problem that is solved by means of experimental and mathematical methods. The article deals with the generation of cavitation in convergent divergent nozzle of rectangular cross section. Measurement of pressure, flow rate, temperature, amount of dissolved air in the liquid and visualization of cavitation area using high-speed camera was performed for different flow rates. The measurement results were generalized by dimensionless analysis, which allows easy detection of cavitation in the nozzle. For numerical simulation the multiphase mathematical model of cavitation consisting of water and vapor was created. During verification the disagreement with the measurements for higher flow rates was proved, therefore the model was extended to multiphase mathematical model (water, vapor and air), due to release of dissolved air. For the mathematical modeling the multiphase turbulence RNG k-ε model for low Reynolds number flow with vapor and air cavitation was used. Subsequently the sizes of the cavitation area were verified. In article the inlet pressure and loss coefficient depending on the amount of air added to the mathematical model are evaluated. On the basis of the approach it may be create a methodology to estimate the amount of released air added at the inlet to the modeled area.

Investigation of the cavitating flow in injector nozzles for diesel and biodiesel

Science.gov (United States)

Zhong, Wenjun; He, Zhixia; Wang, Qian; Jiang, Zhaochen; Fu, Yanan

2013-07-01

In diesel engines, the cavitating flow in nozzles greatly affects the fuel atomization characteristics and then the subsequent combustion and exhaust emissions. At present the biodiesel is a kind of prospective alternative fuel in diesel engines, the flow characteristics for the biodiesel fuel need to be investigated. In this paper, based on the third-generation synchrotrons of Shanghai Synchrotron Radiation facility (SSRF), a high-precision three-dimension structure of testing nozzle with detailed internal geometry information was obtained using X-ray radiography for a more accurate physical model. A flow visualization experiment system with a transparent scaled-up vertical multi-hole injector nozzle tip was setup. A high resolution and speed CCD camera equipped with a long distance microscope device was used to acquire flow images of diesel and biodiesel fuel, respectively. Then, the characteristics of cavitating flow and their effects on the fuel atomization characteristics were investigated. The experimental results show that the nozzle cavitating flow of both the diesel and biodiesel fuel could be divided into four regimes: turbulent flow, cavitation inception, development of cavitation and hydraulic flip. The critical pressures of both the cavitating flow and hydraulic flip of biodiesel are higher than those of diesel. The spray cone angle increases as the cavitation occurs, but it decreases when the hydraulic flip appears. Finally, it can be concluded that the Reynolds number decreases with the increase of cavitation number, and the discharge coefficient increases with the increase of cavitation number.

Incipient nonarteritic anterior ischemic optic neuropathy.

Science.gov (United States)

Hayreh, Sohan Singh; Zimmerman, M Bridget

2007-09-01

To describe the clinical entity of incipient nonarteritic anterior ischemic optic neuropathy (NAION). Cohort study. Fifty-four patients (60 eyes) seen in our clinic from 1973 through 2000. At their first visit to our clinic, all patients gave a detailed ophthalmic and medical history and underwent a comprehensive ophthalmic evaluation, color fundus photography, and fluorescein fundus angiography. At each follow-up visit (of 49 patients [55 eyes]), the same ophthalmic evaluation was performed, except for fluorescein fundus angiography. Clinical features of incipient NAION. Mean age (+/- standard deviation) of the patients was 58.7+/-15.9 years. Median follow-up time was 6.3 years (interquartile range [IQR], 2.1-8.5). At initial visit, all had optic disc edema (ODE) without any visual loss attributable to NAION. In 55%, the fellow eye had classic NAION; in 25%, incipient progressed to classic NAION (after a median time of 5.8 weeks [IQR, 3.2-10.1]); and in 20%, classic NAION developed after resolution of the first episode of incipient NAION. Patients with incipient, compared with classic, NAION had a greater prevalence of diabetes mellitus (Pheart disease (P = 0.046). Patients who progressed to classic NAION versus those who did not were significantly younger (P = 0.025), and their visual acuity worsened in 31% and 0%, respectively, and remained stable in 62% and 98%, respectively; in the eyes with progression, central (in 31%) and peripheral (in 77%) visual fields worsened compared with only 1 eye and 2 eyes, respectively, that did not (P = 0.01 and Pversus 9.6 weeks (IQR, 6.0-17.7) in those who did not progress. The results show that incipient NAION is a distinct clinical entity, with asymptomatic ODE and no visual loss attributable to NAION. When a patient seeks treatment with asymptomatic ODE, incipient NAION must be borne in mind as a strong possibility in those who have had classic NAION in the fellow eye, in diabetics of all ages, and in those with high risk

Experimental and numerical studies on super-cavitating flow of axisymmetric cavitators

Directory of Open Access Journals (Sweden)

Byoung-Kwon Ahn

2010-03-01

Full Text Available Recently underwater systems moving at high speed such as a super-cavitating torpedo have been studied for their practical advantage of the dramatic drag reduction. In this study we are focusing our attention on super-cavitating flows around axisymmetric cavitators. A numerical method based on inviscid flow is developed and the results for several shapes of the cavitator are presented. First using a potential based boundary element method, we find the shape of the cavitator yielding a sufficiently large enough cavity to surround the body. Second, numerical predictions of supercavity are validated by comparing with experimental observations carried out in a high speed cavitation tunnel at Chungnam National University (CNU CT.

Luminescence from hydrodynamic cavitation. Method and preliminary analysis

International Nuclear Information System (INIS)

Leighton, T.; Farhat, M.; Field, J.

2001-01-01

This report describes a photon-counting study of the cavitation luminescence produced by flow over a hydrofoil. The object was to obtain quantitative data on the number of photons emitted for various flow conditions and to study the link between the light output and the potential for cavitation damage. The flow experiments were performed in a cavitation tunnel capable of achieving flow velocities of up to ca. 50 m s -1 in the test sections. The experimental hydrofoil was a NACA 009 blade. Parameters varied were the flow velocity, the incident angle of the hydrofoil and the cavitation index. The results show that significant photon counts are recorded when leading edge cavitation takes place and U-shaped vortices (cavities) shed from the main cavity. The photon count increases dramatically as the flow velocity increases or the cavitation index is reduced. Departure from a Poisson distribution in the arrival times of photons at the detector may be related to the way vortices shed from the main cavity. Finally, there is a clear correlation between light output and the conditions which could cause cavitation damage. (author)

Luminescence from hydrodynamic cavitation. Method and preliminary analysis

Energy Technology Data Exchange (ETDEWEB)

Leighton, T.; Farhat, M.; Field, J. [and others

2001-06-01

This report describes a photon-counting study of the cavitation luminescence produced by flow over a hydrofoil. The object was to obtain quantitative data on the number of photons emitted for various flow conditions and to study the link between the light output and the potential for cavitation damage. The flow experiments were performed in a cavitation tunnel capable of achieving flow velocities of up to ca. 50 m s{sup -1} in the test sections. The experimental hydrofoil was a NACA 009 blade. Parameters varied were the flow velocity, the incident angle of the hydrofoil and the cavitation index. The results show that significant photon counts are recorded when leading edge cavitation takes place and U-shaped vortices (cavities) shed from the main cavity. The photon count increases dramatically as the flow velocity increases or the cavitation index is reduced. Departure from a Poisson distribution in the arrival times of photons at the detector may be related to the way vortices shed from the main cavity. Finally, there is a clear correlation between light output and the conditions which could cause cavitation damage. (author)

Frequency characteristics of liquid hydrogen cavitating flow over a NACA0015 hydrofoil

Science.gov (United States)

Zhu, Jiakai; Wang, Shunhao; Qiu, Limin; Zhi, Xiaoqin; Zhang, Xiaobin

2018-03-01

Large eddy simulation on unsteady cavitating flow of liquid hydrogen over a three-dimensional NACA0015 hydrofoil with the attack angle (α) of 6° are carried out to investigate the dynamic features of cavity with the existence of thermal effects. The numerical model considers the compressibility of both liquid and vapor phase, and is validated by comparing the results with the available experimental data. Special emphasis is put on analyzing the frequency characteristics of cavitation cloud. Strouhal number (St) is plotted against σ/2α (σ is cavitation number), and the water cavitation data reported by Andrt et al. are also used as a reference. It is found that the St number for LH2 cavitation is much smaller than the water, in which the thermal effects are generally not considered, at the same σ/2α value when it is greater than about 2.0, while it returns to the same level as water when σ/2α decreases to below 2.0. The reason is primarily ascribed to the thermal effects, and the detailed explanations are given based on the recognitions that the shedding mechanism of cavitation clouds is predominated by the combined action of the vortex flow and thermal effects. While, when σ/2α decreases to a critical value, the relative effect of the thermal effects on the cavitation dynamics is greatly weakened compared with the mechanism due to the vortex flow, like those in isothermal cavitation flow in traditional fluids. The results provide a deeper understanding of the cryogenic fluid cavitation flow.

Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

Energy Technology Data Exchange (ETDEWEB)

Mitroglou, N.; Lorenzi, M.; Gavaises, M. [City University London, School of Mathematics Computer Science and Engineering, London (United Kingdom); Santini, M. [University of Bergamo, Department of Engineering, Bergamo (Italy)

2016-11-15

The flow inside a purpose built enlarged single-orifice nozzle replica is quantified using time-averaged X-ray micro-computed tomography (micro-CT) and high-speed shadowgraphy. Results have been obtained at Reynolds and cavitation numbers similar to those of real-size injectors. Good agreement for the cavitation extent inside the orifice is found between the micro-CT and the corresponding temporal mean 2D cavitation image, as captured by the high-speed camera. However, the internal 3D structure of the developing cavitation cloud reveals a hollow vapour cloud ring formed at the hole entrance and extending only at the lower part of the hole due to the asymmetric flow entry. Moreover, the cavitation volume fraction exhibits a significant gradient along the orifice volume. The cavitation number and the needle valve lift seem to be the most influential operating parameters, while the Reynolds number seems to have only small effect for the range of values tested. Overall, the study demonstrates that use of micro-CT can be a reliable tool for cavitation in nozzle orifices operating under nominal steady-state conditions. (orig.)

Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

Science.gov (United States)

Mitroglou, N.; Lorenzi, M.; Santini, M.; Gavaises, M.

2016-11-01

The flow inside a purpose built enlarged single-orifice nozzle replica is quantified using time-averaged X-ray micro-computed tomography (micro-CT) and high-speed shadowgraphy. Results have been obtained at Reynolds and cavitation numbers similar to those of real-size injectors. Good agreement for the cavitation extent inside the orifice is found between the micro-CT and the corresponding temporal mean 2D cavitation image, as captured by the high-speed camera. However, the internal 3D structure of the developing cavitation cloud reveals a hollow vapour cloud ring formed at the hole entrance and extending only at the lower part of the hole due to the asymmetric flow entry. Moreover, the cavitation volume fraction exhibits a significant gradient along the orifice volume. The cavitation number and the needle valve lift seem to be the most influential operating parameters, while the Reynolds number seems to have only small effect for the range of values tested. Overall, the study demonstrates that use of micro-CT can be a reliable tool for cavitation in nozzle orifices operating under nominal steady-state conditions.

Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

International Nuclear Information System (INIS)

Mitroglou, N.; Lorenzi, M.; Gavaises, M.; Santini, M.

2016-01-01

The flow inside a purpose built enlarged single-orifice nozzle replica is quantified using time-averaged X-ray micro-computed tomography (micro-CT) and high-speed shadowgraphy. Results have been obtained at Reynolds and cavitation numbers similar to those of real-size injectors. Good agreement for the cavitation extent inside the orifice is found between the micro-CT and the corresponding temporal mean 2D cavitation image, as captured by the high-speed camera. However, the internal 3D structure of the developing cavitation cloud reveals a hollow vapour cloud ring formed at the hole entrance and extending only at the lower part of the hole due to the asymmetric flow entry. Moreover, the cavitation volume fraction exhibits a significant gradient along the orifice volume. The cavitation number and the needle valve lift seem to be the most influential operating parameters, while the Reynolds number seems to have only small effect for the range of values tested. Overall, the study demonstrates that use of micro-CT can be a reliable tool for cavitation in nozzle orifices operating under nominal steady-state conditions. (orig.)

Mechanism of cavitation damage and structure of a cavitating eddy

International Nuclear Information System (INIS)

Efimov, A.V.; Vorob'ev, G.A.; Filenko, Yu.I.; Petrov, K.N.

1976-01-01

As a result of experimental studies of the structure of a cavitating eddy and the action of single cavitation bubbles on a solid surface the assumption of double nature of cavitation damage forces depending on its regimes was made. The first type of the damage forces is shock waves, appearing around collapsing spherical bubble, the second type is hydraulic impacts of microjets making a hole in a collapsing aspherical bubble. The outward appearance of single microdents differs from each other. The damage of the first type is accompanied by corrosion. The cavitation erosion intensity of the damage of the first type exceeds that of the damage of the second type by one order of magnitude. The values of the porosity of a cavitation eddy, the bubble concentration and the distance between them, the bubble distribution according to the size and the form for the initial cavitation stage are given from holographic investigations

Modeling hydrodynamic cavitation

Energy Technology Data Exchange (ETDEWEB)

Kumar, P.S.; Pandit, A.B. [Mumbai Univ. (India). Chemical Engineering Div.

1999-12-01

Cavitation as a source and method of energy input for chemical processing is increasingly studied due to its ability to generate localized high temperatures and pressures under nearly ambient conditions. Compared to cavitation generated by ultrasound, hydrodynamic cavitation has been proved to be a very energy-efficient alternative. A simple and unified model has been developed to study the cavitation phenomena in hydraulic systems with emphasis on the venturi tube and high-speed homogenizer. The model has been found to be satisfactory in explaining the effect of operating variables and equipment geometry on two different modes of cavitation generation qualitatively and in some cases quantitatively. (orig.)

Cavitation guide for control valves

Energy Technology Data Exchange (ETDEWEB)

Tullis, J.P. [Tullis Engineering Consultants, Logan, UT (United States)

1993-04-01

This guide teaches the basic fundamentals of cavitation to provide the reader with an understanding of what causes cavitation, when it occurs, and the potential problems cavitation can cause to a valve and piping system. The document provides guidelines for understanding how to reduce the cavitation and/or select control valves for a cavitating system. The guide provides a method for predicting the cavitation intensity of control valves, and how the effect of cavitation on a system will vary with valve type, valve function, valve size, operating pressure, duration of operation and details of the piping installation. The guide defines six cavitation limits identifying cavitation intensities ranging from inception to the maximum intensity possible. The intensity of the cavitation at each limit Is described, including a brief discussion of how each level of cavitation influences the valve and system. Examples are included to demonstrate how to apply the method, including making both size and pressure scale effects corrections. Methods of controlling cavitation are discussed providing information on various techniques which can be used to design a new system or modify an existing one so it can operate at a desired level of cavitation.

Cavitation guide for control valves

International Nuclear Information System (INIS)

Tullis, J.P.

1993-04-01

This guide teaches the basic fundamentals of cavitation to provide the reader with an understanding of what causes cavitation, when it occurs, and the potential problems cavitation can cause to a valve and piping system. The document provides guidelines for understanding how to reduce the cavitation and/or select control valves for a cavitating system. The guide provides a method for predicting the cavitation intensity of control valves, and how the effect of cavitation on a system will vary with valve type, valve function, valve size, operating pressure, duration of operation and details of the piping installation. The guide defines six cavitation limits identifying cavitation intensities ranging from inception to the maximum intensity possible. The intensity of the cavitation at each limit Is described, including a brief discussion of how each level of cavitation influences the valve and system. Examples are included to demonstrate how to apply the method, including making both size and pressure scale effects corrections. Methods of controlling cavitation are discussed providing information on various techniques which can be used to design a new system or modify an existing one so it can operate at a desired level of cavitation

Spatial distribution of cavitation-shock-pressure around a jet-flow gate-valve

International Nuclear Information System (INIS)

Oba, Risaburo; Takayama, Kazuyoshi; Ito, Yukio; Miyakura, Hideto; Nozaki, Satoru; Ishige, Tadashi; Sonoda, Shuji; Sakamoto, Kenji.

1987-01-01

To make clear the mechanism of cavitation erosion, the spatial distribution of cavitation shock pressures were quantitatively measured by a pressure sensitive sheet in the 1/10 scale model of a jet-flow gate-valve, for various valve-openings and cavitation numbers. The dynamic pressure response of the sheet was corrected by the shock wave generated from detonation explosives. It is made clear that the erosive shock pressures are distributed in a limited part of the whole cavitation region, and the safety region without the fatal cavitation erosion is defined. (author)

Characterization of the cavitating flow in converging-diverging nozzle based on experimental investigations

Directory of Open Access Journals (Sweden)

Rudolf Pavel

2014-03-01

Full Text Available Cavitation phenomena occuring in converging-diverging nozzle (Venturi tube are described in the paper. A closed test circuit with possibility to control both flow rate and static pressure level were used. Loss coefficient was evaluated for different sigma numbers resulting in full „static“ characterization of the nozzle. Visualizations of the cavitation pattern development were acquired and matched with evolution of the loss coefficient. Three cavitation regimes are described: partial cavitation, fully developed cavitation, supercavitation.

Vortex flow and cavitation in diesel injector nozzles

Science.gov (United States)

Andriotis, A.; Gavaises, M.; Arcoumanis, C.

Flow visualization as well as three-dimensional cavitating flow simulations have been employed for characterizing the formation of cavitation inside transparent replicas of fuel injector valves used in low-speed two-stroke diesel engines. The designs tested have incorporated five-hole nozzles with cylindrical as well as tapered holes operating at different fixed needle lift positions. High-speed images have revealed the formation of an unsteady vapour structure upstream of the injection holes inside the nozzle volume, which is referred to as . Computation of the flow distribution and combination with three-dimensional reconstruction of the location of the strings inside the nozzle volume has revealed that strings are found at the core of recirculation zones; they originate either from pre-existing cavitation sites forming at sharp corners inside the nozzle where the pressure falls below the vapour pressure of the flowing liquid, or even from suction of outside air downstream of the hole exit. Processing of the acquired images has allowed estimation of the mean location and probability of appearance of the cavitating strings in the three-dimensional space as a function of needle lift, cavitation and Reynolds number. The frequency of appearance of the strings has been correlated with the Strouhal number of the vortices developing inside the sac volume; the latter has been found to be a function of needle lift and hole shape. The presence of strings has significantly affected the flow conditions at the nozzle exit, influencing the injected spray. The cavitation structures formed inside the injection holes are significantly altered by the presence of cavitation strings and are jointly responsible for up to 10% variation in the instantaneous fuel injection quantity. Extrapolation using model predictions for real-size injectors operating at realistic injection pressures indicates that cavitation strings are expected to appear within the time scales of typical injection

Cavitation in Hydraulic Machinery

Energy Technology Data Exchange (ETDEWEB)

Kjeldsen, M.

1996-11-01

The main purpose of this doctoral thesis on cavitation in hydraulic machinery is to change focus towards the coupling of non-stationary flow phenomena and cavitation. It is argued that, in addition to turbulence, superimposed sound pressure fluctuations can have a major impact on cavitation and lead to particularly severe erosion. For the design of hydraulic devices this finding may indicate how to further limit the cavitation problems. Chapter 1 reviews cavitation in general in the context of hydraulic machinery, emphasizing the initial cavitation event and the role of the water quality. Chapter 2 discusses the existence of pressure fluctuations for situations common in such machinery. Chapter 3 on cavitation dynamics presents an algorithm for calculating the nucleation of a cavity cluster. Chapter 4 describes the equipment used in this work. 53 refs., 55 figs.,10 tabs.

Acoustic cavitation studies

Science.gov (United States)

Crum, L. A.

1981-09-01

The primary thrust of this study was toward a more complete understanding of general aspects of acoustic cavitation. The effect of long-chain polymer additives on the cavitation threshold was investigated to determine if they reduced the acoustic cavitation threshold in a similar manner to the observed reduction in the cavitation index in hydrodynamic cavitation. Measurements were made of the acoustic cavitation threshold as a function of polymer concentration for additives such as guar gum and polyethelene oxide. The measurements were also made as a function of dissolved gas concentration, surface tension and viscosity. It was determined that there was a significant increase in the acoustic cavitation threshold for increased concentrations of the polymer additives (measurable effects could be obtained for concentrations as low as a few parts per million). One would normally expect that an additive that reduces surface tension to decrease the pressure required to cause a cavity to grow and thus these additives, at first thought, should reduce the threshold. However, even in the hydrodynamic case, the threshold was increased. In both of the hydrodynamic cases considered, the explanation for the increased threshold was given in terms of changed fluid dynamics rather than changed physical properties of the fluid.

Effects of physical properties on thermo-fluids cavitating flows

Science.gov (United States)

Chen, T. R.; Wang, G. Y.; Huang, B.; Li, D. Q.; Ma, X. J.; Li, X. L.

2015-12-01

The aims of this paper are to study the thermo-fluid cavitating flows and to evaluate the effects of physical properties on cavitation behaviours. The Favre-averaged Navier-Stokes equations with the energy equation are applied to numerically investigate the liquid nitrogen cavitating flows around a NASA hydrofoil. Meanwhile, the thermodynamic parameter Σ is used to assess the thermodynamic effects on cavitating flows. The results indicate that the thermodynamic effects on the thermo-fluid cavitating flows significantly affect the cavitation behaviours, including pressure and temperature distribution, the variation of physical properties, and cavity structures. The thermodynamic effects can be evaluated by physical properties under the same free-stream conditions. The global sensitivity analysis of liquid nitrogen suggests that ρv, Cl and L significantly influence temperature drop and cavity structure in the existing numerical framework, while pv plays the dominant role when these properties vary with temperature. The liquid viscosity μl slightly affects the flow structure via changing the Reynolds number Re equivalently, however, it hardly affects the temperature distribution.

Cavitation simulation on marine propellers

DEFF Research Database (Denmark)

Shin, Keun Woo

Cavitation on marine propellers causes thrust breakdown, noise, vibration and erosion. The increasing demand for high-efficiency propellers makes it difficult to avoid the occurrence of cavitation. Currently, practical analysis of propeller cavitation depends on cavitation tunnel test, empirical...... criteria and inviscid flow method, but a series of model test is costly and the other two methods have low accuracy. Nowadays, computational fluid dynamics by using a viscous flow solver is common for practical industrial applications in many disciplines. Cavitation models in viscous flow solvers have been...... hydrofoils and conventional/highly-skewed propellers are performed with one of three cavitation models proven in 2D analysis. 3D cases also show accuracy and robustness of numerical method in simulating steady and unsteady sheet cavitation on complicated geometries. Hydrodynamic characteristics of cavitation...

Hydrodynamic cavitation in microsystems. I. Experiments with deionized water and nanofluids

Science.gov (United States)

Medrano, M.; Zermatten, P. J.; Pellone, C.; Franc, J. P.; Ayela, F.

2011-12-01

An experimental study of hydrodynamic cavitation downstream microdiaphragms and microventuris is presented. Deionized water and nanofluids have been characterized within silicon-Pyrex micromachined devices with hydraulic diameters ranging from 51 μm to 104 μm. The input pressure could reach up to 10 bars, and the flow rate was below 1 liter per hour. The output pressure of the devices was fixed at values ranging from 0.3 bar to 2 bars, so that it was possible to study the evolution of the cavitation number as a function of the Reynolds number in the orifice of the diaphragms or in the throat of the venturis. A delay on the onset of cavitation has been recorded for all the devices when they are fed with deionized water, because of the metastability of the liquid and because of the lack of roughness of the walls. For the first time, hydrodynamic cavitation of nanofluids (nanoparticles dispersed into the liquid) has been considered. The presence of nano-aggregates in the liquid does not exhibit any noticeable effect on the cavitation threshold through the venturis. However, such a presence has a strong influence on the cavitation onset in microdiaphragms: above a critical volume solid concentration of ≈10-5, the metastability is broken and the nanofluids behave as tap water filled up with large nuclei. These microdevices, where a low amount of fluid is required to reach cavitating flows, appear to be useful tools in order to study cavitating phenomena in localized area with specific fluids.

Characterization of string cavitation in large-scale Diesel nozzles with tapered holes

Science.gov (United States)

Gavaises, M.; Andriotis, A.; Papoulias, D.; Mitroglou, N.; Theodorakakos, A.

2009-05-01

The cavitation structures formed inside enlarged transparent replicas of tapered Diesel valve covered orifice nozzles have been characterized using high speed imaging visualization. Cavitation images obtained at fixed needle lift and flow rate conditions have revealed that although the conical shape of the converging tapered holes suppresses the formation of geometric cavitation, forming at the entry to the cylindrical injection hole, string cavitation has been found to prevail, particularly at low needle lifts. Computational fluid dynamics simulations have shown that cavitation strings appear in areas where large-scale vortices develop. The vortical structures are mainly formed upstream of the injection holes due to the nonuniform flow distribution and persist also inside them. Cavitation strings have been frequently observed to link adjacent holes while inspection of identical real-size injectors has revealed cavitation erosion sites in the area of string cavitation development. Image postprocessing has allowed estimation of their frequency of appearance, lifetime, and size along the injection hole length, as function of cavitation and Reynolds numbers and needle lift.

Disruption of Brewers' yeast by hydrodynamic cavitation: Process variables and their influence on selective release.

Science.gov (United States)

Balasundaram, B; Harrison, S T L

2006-06-05

Intracellular products, not secreted from the microbial cell, are released by breaking the cell envelope consisting of cytoplasmic membrane and an outer cell wall. Hydrodynamic cavitation has been reported to cause microbial cell disruption. By manipulating the operating variables involved, a wide range of intensity of cavitation can be achieved resulting in a varying extent of disruption. The effect of the process variables including cavitation number, initial cell concentration of the suspension and the number of passes across the cavitation zone on the release of enzymes from various locations of the Brewers' yeast was studied. The release profile of the enzymes studied include alpha-glucosidase (periplasmic), invertase (cell wall bound), alcohol dehydrogenase (ADH; cytoplasmic) and glucose-6-phosphate dehydrogenase (G6PDH; cytoplasmic). An optimum cavitation number Cv of 0.13 for maximum disruption was observed across the range Cv 0.09-0.99. The optimum cell concentration was found to be 0.5% (w/v, wet wt) when varying over the range 0.1%-5%. The sustained effect of cavitation on the yeast cell wall when re-circulating the suspension across the cavitation zone was found to release the cell wall bound enzyme invertase (86%) to a greater extent than the enzymes from other locations of the cell (e.g. periplasmic alpha-glucosidase at 17%). Localised damage to the cell wall could be observed using transmission electron microscopy (TEM) of cells subjected to less intense cavitation conditions. Absence of the release of cytoplasmic enzymes to a significant extent, absence of micronisation as observed by TEM and presence of a lower number of proteins bands in the culture supernatant on SDS-PAGE analysis following hydrodynamic cavitation compared to disruption by high-pressure homogenisation confirmed the selective release offered by hydrodynamic cavitation. Copyright 2006 Wiley Periodicals, Inc.

Cavitation phenomena in extracorporeal microexplosion lithotripsy

Science.gov (United States)

Tomita, Y.; Obara, T.; Takayama, K.; Kuwahara, M.

1994-09-01

An experimental investigation was made of cavitation phenomena induced by underwater shock wave focusing applied to the extracorporeal microexplosion lithotripsy (microexplosion ESWL). Firstly an underwater microexplosion generated by detonation of a 10 mg silver azide pellet was studied and secondly underwater shock focusing and its induced cavitation phenomena were investgated. Underwater shock wave was focused by using a semi-ellipsoidal reflector in which a shock wave generated at the first focal point of the reflector was reflected and focused at the second focal point. It is found that an explosion product gas bubble did not produce any distinct rebound shocks. Meantime cavitation appeared after shock focusing at the second focal point where expansion waves originated at the exit of the reflector were simultaneously collected. A shock/bubble interaction is found to contribute not only to urinary tract stone disintegration but also tissue damage. The cavitation effect associated with the microexplosion ESWL was weaker in comparison with a spark discharge ESWL. The microexplosion ESWL is an effective method which can minimize the number of shock exposures hence decreasing tissue damage by conducting precise positioning of urinary tract stones.

Experimental study of the cavitation erosion in centrifugal pump impeller

International Nuclear Information System (INIS)

Rayan, M.A.

1985-01-01

Research on cavitation damage scale effects show that the damage rate is increased with size and velocity. It seems that for constant velocity there is no clear trend for the variation of erosion with cavitation number. Research on the time effects on damage rate show similarity between cavitation and impingement erosion. The cumulative weight loss versus time curve is of a ''S'' shaped type characterized by an incubation period followed by a period of increasing erosion rate, then a maximum erosion rate, and finally a period of decreasing erosion rate. The objective of this investigation is to present a prototype cavitation erosion experiment in order to clarify the time dependency of the erosive wear

Cavitation instabilities and rotordynamic effects in turbopumps and hydroturbines turbopump and inducer cavitation, experiments and design

CERN Document Server

Salvetti, Maria

2017-01-01

The book provides a detailed approach to the physics, fluid dynamics, modeling, experimentation and numerical simulation of cavitation phenomena, with special emphasis on cavitation-induced instabilities and their implications on the design and operation of high performance turbopumps and hydraulic turbines. The first part covers the fundamentals (nucleation, dynamics, thermodynamic effects, erosion) and forms of cavitation (attached cavitation, cloud cavitation, supercavitation, vortex cavitation) relevant to hydraulic turbomachinery, illustrates modern experimental techniques for the characterization, visualization and analysis of cavitating flows, and introduces the main aspects of the hydrodynamic design and performance of axial inducers, centrifugal turbopumps and hydo-turbines. The second part focuses on the theoretical modeling, experimental analysis, and practical control of cavitation-induced fluid-dynamic and rotordynamic instabilities of hydraulic turbomachinery, with special emphasis on cavitating...

Surface mechanics design by cavitation peening

Directory of Open Access Journals (Sweden)

Hitoshi Soyama

2015-07-01

Full Text Available Although impacts at cavitation bubble collapses cause severe damage in hydraulic machineries, the cavitation impacts can be utilised for surface mechanics design such as introduction of compressive residual stress and/or improvement of fatigue strength. The peening method using the cavitation impacts was called as cavitation peening. In order to reveal the peening intensity of hydrodynamic cavitation and laser cavitation, the arc height of Almen strip and duralumin plate were measured. In the case of hydrodynamic cavitation, cavitation was generated by injecting a high speed water jet into water with a pressurised chamber and an open chamber, and the cavitating jet in air was also examined. The laser cavitation was produced by a pulse laser, and a high speed observation using a high speed video camera was carried out to clarify laser abrasion and laser cavitation with detecting noise by a hydrophone. It was concluded that the peening intensity by using the cavitating jet in water with the pressurized chamber was most aggressive, and the impact induced by the laser cavitation was larger than that of the laser abrasion at the present condition.

Cavitating Orifice: Flow regime transitions and low frequency sound production

NARCIS (Netherlands)

Testud, P.; Moussou, P.; Hirschberg, A.; Aurégan, Y.

2005-01-01

Detailed data are provided for the broadband noise in a cavitating pipe flow through a circular orifice in water. Experiments are performed under industrial conditions, i.e., with a pressure drop varying from 3 to 30 bars and a cavitation number in the range 0.10 = s = 0.77. The speed of sound

Surface mechanics design by cavitation peening

OpenAIRE

Hitoshi Soyama

2015-01-01

Although impacts at cavitation bubble collapses cause severe damage in hydraulic machineries, the cavitation impacts can be utilised for surface mechanics design such as introduction of compressive residual stress and/or improvement of fatigue strength. The peening method using the cavitation impacts was called as cavitation peening. In order to reveal the peening intensity of hydrodynamic cavitation and laser cavitation, the arc height of Almen strip and duralumin plate were measured. In the...

Modeling liquid hydrogen cavitating flow with the full cavitation model

Energy Technology Data Exchange (ETDEWEB)

Zhang, X.B.; Qiu, L.M.; Qi, H.; Zhang, X.J.; Gan, Z.H. [Institute of Refrigeration and Cryogenic Engineering, Zhejiang University, Hangzhou 310027 (China)

2008-12-15

Cavitation is the formation of vapor bubbles within a liquid where flow dynamics cause the local static pressure to drop below the vapor pressure. This paper strives towards developing an effective computational strategy to simulate liquid hydrogen cavitation relevant to liquid rocket propulsion applications. The aims are realized by performing a steady state computational fluid dynamic (CFD) study of liquid hydrogen flow over a 2D hydrofoil and an axisymmetric ogive in Hord's reports with a so-called full cavitation model. The thermodynamic effect was demonstrated with the assumption of thermal equilibrium between the gas phase and liquid phase. Temperature-dependent fluid thermodynamic properties were specified along the saturation line from the ''Gaspak 3.2'' databank. Justifiable agreement between the computed surface pressure, temperature and experimental data of Hord was obtained. Specifically, a global sensitivity analysis is performed to examine the sensitivity of the turbulent computations to the wall grid resolution, wall treatments and changes in model parameters. A proper near-wall model and grid resolution were suggested. The full cavitation model with default model parameters provided solutions with comparable accuracy to sheet cavitation in liquid hydrogen for the two geometries. (author)

Overview of Rotating Cavitation and Cavitation Surge in the Fastrac Engine LOX Turbopump

Science.gov (United States)

Zoladz, Thomas; Turner, Jim (Technical Monitor)

2001-01-01

Observations regarding rotating cavitation and cavitation surge experienced during the development of the Fastrac 60 Klbf engine turbopump are discussed. Detailed observations from the analysis of both water flow and liquid oxygen test data are offered. Scaling and general comparison of rotating cavitation between water flow and liquid oxygen testing are discussed. Complex data features linking the localized rotating cavitation mechanism of the inducer to system surge components are described in detail. Finally a description of a simple lumped-parameter hydraulic system model developed to better understand observed data is given.

Cavitation instabilities in hydraulic machines

International Nuclear Information System (INIS)

Tsujimoto, Y

2013-01-01

Cavitation instabilities in hydraulic machines, hydro turbines and turbopump inducers, are reviewed focusing on the cause of instabilities. One-dimensional model of hydro turbine system shows that the overload surge is caused by the diffuser effect of the draft tube. Experiments show that this effect also causes the surge mode oscillations at part load. One dimensional model of a cavitating turbopump inducer shows that the mass flow gain factor, representing the cavity volume increase caused by the incidence angle increase is the cause of cavitation surge and rotating cavitation. Two dimensional model of a cavitating turbopump inducer shows that various modes of cavitation instabilities start to occur when the cavity length becomes about 65% of the blade spacing. This is caused by the interaction of the local flow near the cavity trailing edge with the leading edge of the next blade. It was shown by a 3D CFD that this is true also for real cases with tip cavitation. In all cases, it was shown that cavitation instabilities are caused by the fundamental characteristics of cavities that the cavity volume increases with the decrease of ambient pressure or the increase of the incidence angle

Relative roughness controls on incipient sediment motion in steep channels

Science.gov (United States)

Prancevic, J.; Lamb, M. P.; Fuller, B. M.

2012-12-01

For over eight decades, researchers have noted an appreciable increase in the nondimensional shear stress (Shields number) at initiation of fluvial bedload transport with increasing bed slope. The precise cause of the trend, however, is obscured by the covariance of several factors with increased slope: a greater downstream component of the gravity acting on the grains and fluid, changes in bed morphology, increased grainsize relative to the channel width that may lead to grain bridging, and increased grainsize relative to flow depth (relative roughness) that may change flow hydraulics and particle buoyancy. Here, we report on ongoing laboratory experiments spanning a wide range of bed slopes (2% to 67%) designed to isolate these variables and determine the true cause of heightened critical Shields numbers on steep slopes. First, we eliminated bed morphology as a factor by using only planar beds. To investigate the effect of grain bridging, we used two different channel widths, representing width-to-grainsize ratios of 23:1 and 9:1. Finally, to separate the effects of slope from relative roughness, we compared incipient motion conditions for acrylic particles (submerged specific gravity of 0.15) to natural siliciclastic gravel (submerged specific gravity of 1.65). Different particle densities allowed us to explore incipient motion as a function of relative roughness, independent of channel slope, because lighter particles move at shallower flow depths than heavier ones of the same size. Results show that both materials exhibit a positive trend between bed slope and critical Shields number despite the existence of planar beds for all slopes. Furthermore, changing the grainsize-to-width ratio had a negligible effect on this trend. For all slopes, the critical Shields number for bedload transport was higher for the acrylic particles than for gravel, indicating that relative roughness has a strong control on incipient sediment motion independent of channel slope. These

Cavitation inception in nozzle-plate and wire mesh pressure droppers in water and sodium

International Nuclear Information System (INIS)

Collinson, A.E.

1976-01-01

Cavitation tests on multi-hole nozzle plates and wire meshes approximately 100mm diameter in water at 20 deg C and sodium at 300 deg C are described. These pressure dropping elements were mounted in recirculating loops where cavitation was induced by gradually lowering the back-ground pressure at constant flow. Cavitation was detected acoustically using wall mounted piezoelectric microphones, the signal being displayed on a ratemeter recording individual cavitation events. For nozzle plates, cavitation started intermittently as the pressure was lowered, the noise level suddenly increasing at a critical cavitation number sigma. For meshes the intermittent region was absent. Values of sigma for nozzles and meshes were similar in water and sodium for the conditions prevailing during the tests. It was apparent that cavitation took place on the axes of vortices both in the free stream and close to nozzle curved surfaces

Statistical analysis of hydrodynamic cavitation events

Science.gov (United States)

Gimenez, G.; Sommer, R.

1980-10-01

The frequency (number of events per unit time) of pressure pulses produced by hydrodynamic cavitation bubble collapses is investigated using statistical methods. The results indicate that this frequency is distributed according to a normal law, its parameters not being time-evolving.

Numerical simulation of wall roughness effects in cavitating flow

International Nuclear Information System (INIS)

Echouchene, F.; Belmabrouk, H.; Le Penven, L.; Buffat, M.

2011-01-01

Hydrodynamic cavitation has an important effect on the performance of Diesel injectors. It influences the nature of the fuel spray and the efficiency of the combustion process. In the present study, we investigate numerically the effect of wall roughness in the cavitating and turbulent flow developing inside a Diesel injector. The mixture model based on a single fluid is adopted and the commercial Fluent software is used to solve the transport equations. The discharge coefficient C d is computed for different cavitation numbers and wall roughness heights. Profiles of density mixture, vapor volume fraction, mean velocity and turbulent kinetic energy are reported. The effects of wall roughness and injection pressure are analyzed.

Numerical simulation of wall roughness effects in cavitating flow

Energy Technology Data Exchange (ETDEWEB)

Echouchene, F. [Laboratoire d' electronique et de microelectronique, Departement de Physique, Faculte des Sciences de Monastir, 5000 (Tunisia); Belmabrouk, H., E-mail: frchouchene@yahoo.fr [Laboratoire d' electronique et de microelectronique, Departement de Physique, Faculte des Sciences de Monastir, 5000 (Tunisia); Le Penven, L.; Buffat, M. [LMFA UMR CNRS 5509, Universite de Claude Bernard Lyon 1, Ecole Centrale de Lyon, INSA de Lyon (France)

2011-10-15

Hydrodynamic cavitation has an important effect on the performance of Diesel injectors. It influences the nature of the fuel spray and the efficiency of the combustion process. In the present study, we investigate numerically the effect of wall roughness in the cavitating and turbulent flow developing inside a Diesel injector. The mixture model based on a single fluid is adopted and the commercial Fluent software is used to solve the transport equations. The discharge coefficient C{sub d} is computed for different cavitation numbers and wall roughness heights. Profiles of density mixture, vapor volume fraction, mean velocity and turbulent kinetic energy are reported. The effects of wall roughness and injection pressure are analyzed.

Influences of hydrodynamic conditions, nozzle geometry on appearance of high submerged cavitating jets

Directory of Open Access Journals (Sweden)

Hutli Ezddin

2013-01-01

Full Text Available Based on visualization results of highly-submerged cavitating water jet obtained with digital camera, the influences of related parameters such as: injection pressure, nozzle diameter and geometry, nozzle mounting (for convergent / divergent flow, cavitation number and exit jet velocity, were investigated. In addition, the influence of visualization system position was also studied. All the parameters have been found to be of strong influence on the jet appearance and performance. Both hydro-dynamical and geometrical parameters are playing the main role in behavior and intensity of cavitation phenomenon produced by cavitating jet generator. Based on our considerable previous experience in working with cavitating jet generator, the working conditions were chosen in order to obtain measurable phenomenon. [Projekat Ministarstva nauke Republike Srbije, br. TR35046

Cavitation and non-cavitation regime for large-scale ultrasonic standing wave particle separation systems--In situ gentle cavitation threshold determination and free radical related oxidation.

Science.gov (United States)

Johansson, Linda; Singh, Tanoj; Leong, Thomas; Mawson, Raymond; McArthur, Sally; Manasseh, Richard; Juliano, Pablo

2016-01-01

We here suggest a novel and straightforward approach for liter-scale ultrasound particle manipulation standing wave systems to guide system design in terms of frequency and acoustic power for operating in either cavitation or non-cavitation regimes for ultrasound standing wave systems, using the sonochemiluminescent chemical luminol. We show that this method offers a simple way of in situ determination of the cavitation threshold for selected separation vessel geometry. Since the pressure field is system specific the cavitation threshold is system specific (for the threshold parameter range). In this study we discuss cavitation effects and also measure one implication of cavitation for the application of milk fat separation, the degree of milk fat lipid oxidation by headspace volatile measurements. For the evaluated vessel, 2 MHz as opposed to 1 MHz operation enabled operation in non-cavitation or low cavitation conditions as measured by the luminol intensity threshold method. In all cases the lipid oxidation derived volatiles were below the human sensory detection level. Ultrasound treatment did not significantly influence the oxidative changes in milk for either 1 MHz (dose of 46 kJ/L and 464 kJ/L) or 2 MHz (dose of 37 kJ/L and 373 kJ/L) operation. Copyright © 2015 Elsevier B.V. All rights reserved.

Fundamentals of Cavitation

CERN Document Server

Franc, Jean-Pierre

2005-01-01

The present book is aimed at providing a comprehensive presentation of cavitation phenomena in liquid flows. It is further backed up by the experience, both experimental and theoretical, of the authors whose expertise has been internationally recognized. A special effort is made to place the various methods of investigation in strong relation with the fundamental physics of cavitation, enabling the reader to treat specific problems independently. Furthermore, it is hoped that a better knowledge of the cavitation phenomenon will allow engineers to create systems using it positively. Examples in the literature show the feasibility of this approach.

Occurrence of hydrodynamic cavitation.

Science.gov (United States)

Nosov, V R; Gómez-Mancilla, J C; Meda-Campaña, J A

2011-01-01

In this paper, the conditions under which cavitation (or liquid film rupture) can or cannot occur in thin layers of moving liquid are derived for three typical cases. At the same time, expressions depending on geometrical and movement parameters, where cavitation might start, are given. The results are obtained using simple engineering terms, which can be used in cases whether it is necessary to avoid cavitation or to induce it.

A novel ultrasonic cavitation enhancer

NARCIS (Netherlands)

Rivas, Fernandez D.; Verhaagen, B.; Galdamez Perez, Andres; Castro-Hernandez, Elena; Zwieten, Van Ralph; Schroen, Karin

2015-01-01

We introduce a Cavitation Intensifying Bag as a versatile tool for acoustic cavitation control. The cavitation activity is spatially controlled by the modification of the inner surface of the bag with patterned pits of microscopic dimensions. We report on different measurements such as the

A novel ultrasonic cavitation enhancer

NARCIS (Netherlands)

Fernandez Rivas, David; Verhaagen, B.; Galdamez Perez, Andres; Castro-Hernandez, Elena; van Zwieten, Ralph; Schroen, Karin

2015-01-01

We introduce a Cavitation Intensifying Bag as a versatile tool for acoustic cavitation control. The cavitation activity is spatially controlled by the modification of the inner surface of the bag with patterned pits of microscopic dimensions. We report on different measurements such as the

Prediction method for cavitation erosion based on measurement of bubble collapse impact loads

International Nuclear Information System (INIS)

Hattori, S; Hirose, T; Sugiyama, K

2009-01-01

The prediction of cavitation erosion rates is important in order to evaluate the exact life of components. The measurement of impact loads in bubble collapses helps to predict the life under cavitation erosion. In this study, we carried out erosion tests and the measurements of impact loads in bubble collapses with a vibratory apparatus. We evaluated the incubation period based on a cumulative damage rule by measuring the impact loads of cavitation acting on the specimen surface and by using the 'constant impact load - number of impact loads curve' similar to the modified Miner's rule which is employed for fatigue life prediction. We found that the parameter Σ(F i α xn i ) (F i : impact load, n i : number of impacts and α: constant) is suitable for the evaluation of the erosion life. Moreover, we propose a new method that can predict the incubation period under various cavitation conditions.

Comparison of Radiography, Laser Fluorescence, and Visual Examination in Diagnosing Incipient OcclusalCaries of Permanent First Molars

Directory of Open Access Journals (Sweden)

Zahra Bahrololoomi

2015-10-01

Full Text Available Objectives: Early diagnosis of incipient and non cavitated carious lesions is crucial for performing preventive treatments. The aim of this study was to compare the effi- ciency of three diagnostic methods of bite-wing radiography, DIAGNOdent, and visu- al examination in diagnosing the incipient occlusal caries of permanent first molars.Materials and Methods:  In this diagnostic cross-sectional study, 109 premanent first molar teeth of 31 patients aged 7-13 years were examined visually by bite-wing radi- ograghy, and DIAGNOdent. Scoring of visual and radiography examinations were based on the Ekstrand classification. Visual examination after pit and fissure opening was used as the gold standard. ROC curve (Receiver Operating Characteristics was used to define the best cut-off point for DIAGNodent compareing with gold standard and inter-examiner reproductibility of visual, radiography were assessed using Kappa test and ICC (Intraclass Correlation wase used for DIAGNOdent values.Results: The sensitivity of detecting caries that had extended into the enamel was 81.4%, 86.3%, and 81.4% for visual examination, DIAGNOdent, and radiography, respectively. Moreover, the specificity was 100%, 71.4%, and 100% for visual obser- vation, DIAGNOdent, and radiography, respectively in the enamel. The Kappa index for inter-examiner correlation was 0.7 and 0.8 for visual examination and radiog- raphy, respectively. The ICC (Intraclass Correlation was 0.98 for the values read by DIAGNOdent.Conclusion: Visual examination is rendered as the first choice in the diagnosis of in- cipient caries. In suspicious cases, radiography and laser DIAGNOdent can be used as adjunct procedures.

Computation of Cavitating Flow in a Francis Hydroturbine

Science.gov (United States)

Leonard, Daniel; Lindau, Jay

2013-11-01

In an effort to improve cavitation characteristics at off-design conditions, a steady, periodic, multiphase, RANS CFD study of an actual Francis hydroturbine was conducted and compared to experimental results. It is well-known that operating hydroturbines at off-design conditions usually results in the formation of large-scale vaporous cavities. These cavities, and their subsequent collapse, reduce efficiency and cause damage and wear to surfaces. The conventional hydro community has expressed interest in increasing their turbine's operating ranges, improving their efficiencies, and reducing damage and wear to critical turbine components. In this work, mixing planes were used to couple rotating and stationary stages of the turbine which have non-multiple periodicity, and provide a coupled solution for the stay vanes, wicket gates, runner blades, and draft tube. The mixture approach is used to simulate the multiphase flow dynamics, and cavitation models were employed to govern the mass transfer between liquid and gas phases. The solution is compared with experimental results across a range of cavitation numbers which display all the major cavitation features in the machine. Unsteady computations are necessary to capture inherently unsteady cavitation phenomena, such as the precessing vortex rope, and the shedding of bubbles from the wicket gates and their subsequent impingement upon the leading edge of the runner blades. To display these features, preliminary unsteady simulations of the full machine are also presented.

Study on vortex cavitation in a compact fast reactor. Effects of system pressure on inception condition

International Nuclear Information System (INIS)

Hiroyuki Sato; Toshiki Ezure; Hideki Kamide

2005-01-01

A compact sodium reactor is designed as a commercialized fast reactor cycle system. A 1/10 scaled water experiment was performed to optimize flow in an upper plenum of the reactor vessel, because of high flow velocity resulted from the compacted vessel. In the experiment, vortex cavitation was found at the hot leg inlet because of high velocity in the hot leg pipe (9.4m/s in the design). To evaluate cavitation inception condition of the commercialized reactor, we use the cavitation number k in order to consider the difference of system pressures (0.1MPa in the experiment and 0.3MPa in the design). The minimum pressure at the vortex center will depend on vortex core radius (size of forced vortex region). It is related to axial velocity gradient and fluid viscosity in theory of the Burger's stretched vortex model. We carried out a basic water experiment to investigate the influence of system pressure and fluid viscosity on the vortex cavitation. The cavitation number at the inception of vortex cavitation slightly increased according to the increase of the system pressure. It means that the vortex cavitation occurs easily under higher pressure condition as compared with the similar condition of cavitation number with lower pressure. However the increase was less than 30% when the system pressure was varied from 0.1 to 0.3MPa. The influence of fluid viscosity was examined by change of fluid temperature. Velocity distribution around the vortex was also measured to see the structure of vortex. (authors)

Interactions of inertial cavitation bubbles with stratum corneum lipid bilayers during low-frequency sonophoresis.

Science.gov (United States)

Tezel, Ahmet; Mitragotri, Samir

2003-12-01

Interactions of acoustic cavitation bubbles with biological tissues play an important role in biomedical applications of ultrasound. Acoustic cavitation plays a particularly important role in enhancing transdermal transport of macromolecules, thereby offering a noninvasive mode of drug delivery (sonophoresis). Ultrasound-enhanced transdermal transport is mediated by inertial cavitation, where collapses of cavitation bubbles microscopically disrupt the lipid bilayers of the stratum corneum. In this study, we describe a theoretical analysis of the interactions of cavitation bubbles with the stratum corneum lipid bilayers. Three modes of bubble-stratum corneum interactions including shock wave emission, microjet penetration into the stratum corneum, and impact of microjet on the stratum corneum are considered. By relating the mechanical effects of these events on the stratum corneum structure, the relationship between the number of cavitation events and collapse pressures with experimentally measured increase in skin permeability was established. Theoretical predictions were compared to experimentally measured parameters of cavitation events.

Cavitation erosion in sodium flow, sodium cavitation tunnel testing

International Nuclear Information System (INIS)

Courbiere, Pierre.

1981-04-01

The high-volume sodium flows present in fast neutron reactors are liable to induce cavitation phenomena in various portion of the sodium lines and pumps. The absence of sufficient data in this area led the C.E.A. to undertake an erosion research program in cavitating sodium flow. This paper discusses the considerations leading to the definition and execution of sodium cavitation erosion tests, and reviews the tests run with 400 0 C sodium on various steel grades: 316, 316 L, 316 Ti (Z8CNDT17-12), Poral (Z3CND18-12), 304 L and LN2 - clad 316 L (Ni coating-clad 316 L). Acoustic detection and signal processing methods were used with an instrument package designed and implemented at the Cadarache Nuclear Research Center

Numerical and experimental research on unsteady cavitating flow around NACA 2412 hydrofoil

International Nuclear Information System (INIS)

Sedlář, M; Komárek, M; Rudolf, P; Kozák, J; Huzlík, R

2015-01-01

This work deals with the numerical and experimental investigation of unsteady cavitating flow around a prismatic NACA 2412 hydrofoil. The main attention is focussed on the dependence of cavitation dynamics on the cavitation number at high incidence angles. The experimental research is carried out in the cavitation water tunnel the rectangular test section of which has inner dimensions 150×150×500 mm. Currently tested hydrofoils have a chord length of 120 mm and are equipped with pressure transducers at the leading edge and on the suction side. The PVDF hydrophone enables to measure high-frequency pressure pulses behind the hydrofoil trailing edge. The visualizations are based on two simultaneous high-speed cameras, recording the hydrofoil from the top and from one side. A comprehensive CFD analysis has been done with the ANSYS CFX package for a wide range of flow regimes. Different turbulence models including SAS-SST and Reynolds-stress models have been tested to capture highly unsteady phenomena on the hydrofoil. The numerical simulations show, that the dominant frequency of the cavity oscillation depends on the cavitation number and that there is a certain range of this number in which the 'resonance' effect can be reached. In such regime the amplitudes of the pressure pulses on the suction side of the hydrofoil dramatically increase. The calculated results have been verified by both the visualizations and the pressure measurements carried out at the hydrofoil incidence angle of 8 degrees

Hydrodynamic cavitation in microsystems. II. Simulations and optical observations

Science.gov (United States)

Medrano, M.; Pellone, C.; Zermatten, P. J.; Ayela, F.

2012-04-01

Numerical calculations in the single liquid phase and optical observations in the two-phase cavitating flow regime have been performed on microdiaphragms and microventuris fed with deionized water. Simulations have confirmed the influence of the shape of the shrinkage upon the contraction of the jet, and so on the localisation of possible cavitating area downstream. Observations of cavitating flow patterns through hybrid silicon-pyrex microdevices have been performed either via a laser excitation with a pulse duration of 6 ns, or with the help of a high-speed camera. Recorded snapshots and movies are presented. Concerning microdiaphragms, it is confirmed that very high shear rates downstream the diaphragms are the cause of bubbly flows. Concerning microventuris, a gaseous cavity forms on a boundary downstream the throat. As a consequence of a microsystem instability, the cavity displays a high frequency pulsation. Low values Strouhal numbers are associated to such a sheet cavitation. Moreover, when the intensity of the cavitating flow is reduced, there is a mismatch between the frequency of the pulsation of the cavity and the frequency of shedded clouds downstream the channel. That may be the consequence of viscous effects limiting the impingement of a re-entrant liquid jet on the attached cavity.

Cavitation Inception Scale Effects. 1. Nuclei Distributions in Natural Waters. 2. Cavitation Inception in a Turbulent Shear Flow.

Science.gov (United States)

1987-05-01

cavitation is pressure-controlled. The term hydrodynamic cavitation is some- times used to stress the dominant role of dynamic pressure in the cavitation...Diffraction Pattern of Opaque and Transparent Objects with Coherent Back- ground," Optica Acta, 11, 183-193. Peterson, F.B. (1972), " Hydrodynamic Cavitation and

Ablation of benign prostatic hyperplasia using microbubble-mediated ultrasound cavitation.

Science.gov (United States)

Li, Tao; Liu, Zheng

2010-04-01

Benign prostatic hyperplasia (BPH) is a world-wide common disease in elderly male patients. A number of invasive physiotherapies have been used to replace prostatectomy. In this article we report our hypothesis of using microbubbles-mediated ultrasound cavitation effects to ablate prostatic tissues. Microbubble ultrasound contrast agent is widely used contrast media in ultrasonography, yet it is also found to act as cavitation nuclei or enhancer. Once excited by a high peak pressure ultrasound pulse, the mechanical effects, like shock wave and microstream, released from cavitation could produce a series of bioeffects, contributing to sonoporation, microvascular rupture and hematoma. BPH is known to have hyperplastic neovasculature and this make it possible to be disrupted by the physical effects of cavitation under existing microbubbles in circulation. Mechanical ablation of prostatic capillary or small vessels could result in pathological alterations such as thrombosis, micro-circulation blockage, prostatic necrosis and atrophia. Thereupon it could effectively treat BPH by nontraumatic ways. (c) 2009 Elsevier Ltd. All rights reserved.

Cavitation problems in sodium valves

International Nuclear Information System (INIS)

Elie, X.

1976-01-01

Cavitation poses few problems for sodium valves, in spite of the fact that the loops are not pressurized. This is no doubt due to the low flow velocities in the pipes. For auxiliary loop valves we are attempting to standardize performances with respect to cavitation. For economic reasons cavitation thresholds are approached with large diameter valves. (author)

Comparative study of incompressible and isothermal compressible flow solvers for cavitating flow dynamics

Energy Technology Data Exchange (ETDEWEB)

Park, Sun Ho [Korea Maritime and Ocean University, Busan (Korea, Republic of); Rhee, Shin Hyung [Seoul National University, Seoul (Korea, Republic of)

2015-08-15

Incompressible flow solvers are generally used for numerical analysis of cavitating flows, but with limitations in handling compressibility effects on vapor phase. To study compressibility effects on vapor phase and cavity interface, pressure-based incompressible and isothermal compressible flow solvers based on a cell-centered finite volume method were developed using the OpenFOAM libraries. To validate the solvers, cavitating flow around a hemispherical head-form body was simulated and validated against the experimental data. The cavity shedding behavior, length of a re-entrant jet, drag history, and the Strouhal number were compared between the two solvers. The results confirmed that computations of the cavitating flow including compressibility effects improved the reproduction of cavitation dynamics.

Research on Cavitation Regions of Upstream Pumping Mechanical Seal Based on Dynamic Mesh Technique

Directory of Open Access Journals (Sweden)

Huilong Chen

2014-08-01

Full Text Available In order to study the cavitation area of the Upstream Pumping Mechanical Seal, three-dimensional microgap inner flow field of the Upstream Pumping Mechanical Seal was simulated with multiphase flow cavitation model and dynamic mesh technique based on hydrodynamic lubrication theory. Furthermore, the simulated result was compared with the experimental data. The results show that the simulated result with the Zwart-Gerber-Belamri cavitation model was much closer to the experimental data. The area of cavitation inception mainly occurred at the concave side of the spiral groove and surrounding region without spiral grooves, which was nearly covered by the inner diameter to roots of grooves; in addition, the region near the surface of the stationary ring was primary cavitation location. The area of cavitation has little relationship with the medium pressure; however, it became larger following increasing rotating speed in the range of researched operating conditions. Moreover the boundary of cavitated area was transformed from smooth to rough, which occurred in similar film thickness. When cavitation number was decreasing, which was conducive to improving the lubrication performance of sealed auxiliary, it made the sealing stability decline.

Numerical and experimental investigations on cavitation erosion

Science.gov (United States)

Fortes Patella, R.; Archer, A.; Flageul, C.

2012-11-01

A method is proposed to predict cavitation damage from cavitating flow simulations. For this purpose, a numerical process coupling cavitating flow simulations and erosion models was developed and applied to a two-dimensional (2D) hydrofoil tested at TUD (Darmstadt University of Technology, Germany) [1] and to a NACA 65012 tested at LMH-EPFL (Lausanne Polytechnic School) [2]. Cavitation erosion tests (pitting tests) were carried out and a 3D laser profilometry was used to analyze surfaces damaged by cavitation [3]. The method allows evaluating the pit characteristics, and mainly the volume damage rates. The paper describes the developed erosion model, the technique of cavitation damage measurement and presents some comparisons between experimental results and numerical damage predictions. The extent of cavitation erosion was correctly estimated in both hydrofoil geometries. The simulated qualitative influence of flow velocity, sigma value and gas content on cavitation damage agreed well with experimental observations.

A study on tip leakage vortex dynamics and cavitation in axial-flow pump

Energy Technology Data Exchange (ETDEWEB)

Shi, Lei; Zhang, Desheng; Jin, Yongxin; Shi, Weidong [Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013 (China); Esch, B P M van, E-mail: zds@ujs.edu.cn [Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB (Netherlands)

2017-06-15

The tip leakage flows and related cavitation in the tip region of an axial-flow pump were investigated in detail using the numerical and experimental methods. The numerical results of the pump model performance were in good agreement with experimental data. The flow structures in the tip clearance were clarified clearly with detailed data involving the axial velocity and turbulent kinetic energy. When depicting the feature of vortex core, the advanced vortex identification method λ {sub 2}-criterion was used. Simultaneously, the minimum tension criterion was also applied to predict the cavitation inception for different flow rates and it is consistent with the distributions of vorticity and pressure in the vortex core. The roll-up process of TLV is highly three-dimensional and the entrainment would follow different paths. Then, both the numerical and experimental approaches show the cavitation patterns for different cavitation conditions, and it also finds that slight cavitation would promote the development of tip leakage vortex (TLV) while the TLV seems to be eliminated for a low cavitation number, especially before a specific location of blade tip due to the blade loading change induced by cavitation possibly. (paper)

Cavitation nucleation in gelatin: Experiment and mechanism.

Science.gov (United States)

Kang, Wonmo; Adnan, Ashfaq; O'Shaughnessy, Thomas; Bagchi, Amit

2018-02-01

Dynamic cavitation in soft materials is becoming increasingly relevant due to emerging medical implications such as the potential of cavitation-induced brain injury or cavitation created by therapeutic medical devices. However, the current understanding of dynamic cavitation in soft materials is still very limited, mainly due to lack of robust experimental techniques. To experimentally characterize cavitation nucleation under dynamic loading, we utilize a recently developed experimental instrument, the integrated drop tower system. This technique allows quantitative measurements of the critical acceleration (a cr ) that corresponds to cavitation nucleation while concurrently visualizing time evolution of cavitation. Our experimental results reveal that a cr increases with increasing concentration of gelatin in pure water. Interestingly, we have observed the distinctive transition from a sharp increase (pure water to 1% gelatin) to a much slower rate of increase (∼10× slower) between 1% and 7.5% gelatin. Theoretical cavitation criterion predicts the general trend of increasing a cr , but fails to explain the transition rates. As a likely mechanism, we consider concentration-dependent material properties and non-spherical cavitation nucleation sites, represented by pre-existing bubbles in gels, due to possible interplay between gelatin molecules and nucleation sites. This analysis shows that cavitation nucleation is very sensitive to the initial configuration of a bubble, i.e., a non-spherical bubble can significantly increase a cr . This conclusion matches well with the experimentally observed liquid-to-gel transition in the critical acceleration for cavitation nucleation. From a medical standpoint, understanding dynamic cavitation within soft materials, i.e., tissues, is important as there are both potential injury implications (blast-induced cavitation within the brain) as well as treatments utilizing the phenomena (lithotripsy). In this regard, the main

Numerical simulation of cryogenic cavitating flow by an extended transport-based cavitation model with thermal effects

Science.gov (United States)

Zhang, Shaofeng; Li, Xiaojun; Zhu, Zuchao

2018-06-01

Thermodynamic effects on cryogenic cavitating flow is important to the accuracy of numerical simulations mainly because cryogenic fluids are thermo-sensitive, and the vapour saturation pressure is strongly dependent on the local temperature. The present study analyses the thermal cavitating flows in liquid nitrogen around a 2D hydrofoil. Thermal effects were considered using the RNG k-ε turbulence model with a modified turbulent eddy viscosity and the mass transfer homogenous cavitation model coupled with energy equation. In the cavitation model process, the saturated vapour pressure is modified based on the Clausius-Clapron equation. The convection heat transfer approach is also considered to extend the Zwart-Gerber-Belamri model. The predicted pressure and temperature inside the cavity under cryogenic conditions show that the modified Zwart-Gerber-Belamri model is in agreement with the experimental data of Hord et al. in NASA, especially in the thermal field. The thermal effect significantly affects the cavitation dynamics during phase-change process, which could delay or suppress the occurrence and development of cavitation behaviour. Based on the modified Zwart-Gerber-Belamri model proposed in this paper, better prediction of the cryogenic cavitation is attainable.

Experimental investigation of a cavitating backward-facing step flow

International Nuclear Information System (INIS)

Maurice, G; Djeridi, H; Barre, S

2014-01-01

The present study is the first part of global experimental work which is intended to produce a refined database of liquid and vapor phases and to improve CFD modeling of turbulent cavitating flows which can occur in rocket engine turbo-pump inducers. The purpose of the present experimental study is to get a better understanding of the dynamics of the liquid phase in a cavitating backward facing step flow and provide a refined database for the physical analysis of interaction between turbulence and cavitation. The backward facing step flow provides us a well-known test case to compare vortex dynamics and a realistic industrial configuration such as backflow in turbo machinery. Experiments were conducted in the hydrodynamic tunnel of CREMHyG at Grenoble,which was especially designed to study cavitating shear flows at high Reynolds numbers. To highlight the liquid phase topology and dynamics such as large vortex structures, free shear layer instability, reattachment wall interaction and reverse flow, the flow is characterized by Laser Induced Fluoresence Particles Image Velocimetry (PIV-LIF) measurements techniques and by Laser Doppler Velocimetry (LDV) techniques using spectral analysis to characterize the vortex shedding dynamics. The liquid phase was analyzed at different cavitation levels corresponding to 1% to 45% of void ratio range inside the shear layer, recirculation area and reattachment zone. The mean and fluctuating liquid velocities are clearly modified by the vapor phase and the scale of the vortical structures tends to be smaller inducing a destructuration of turbulence by cavitation

Attached cavitation at a small diameter ultrasonic horn tip

Science.gov (United States)

Žnidarčič, Anton; Mettin, Robert; Cairós, Carlos; Dular, Matevž

2014-02-01

Ultrasonic horn transducers are frequently used in applications of acoustic cavitation in liquids, for instance, for cell disruption or sonochemical reactions. They are operated typically in the frequency range up to about 50 kHz and have tip diameters from some mm to several cm. It has been observed that if the horn tip is sufficiently small and driven at high amplitude, cavitation is very strong, and the tip can be covered entirely by the gas/vapor phase for longer time intervals. A peculiar dynamics of the attached cavity can emerge with expansion and collapse at a self-generated frequency in the subharmonic range, i.e., below the acoustic driving frequency. Here, we present a systematic study of the cavitation dynamics in water at a 20 kHz horn tip of 3 mm diameter. The system was investigated by high-speed imaging with simultaneous recording of the acoustic emissions. Measurements were performed under variation of acoustic power, air saturation, viscosity, surface tension, and temperature of the liquid. Our findings show that the liquid properties play no significant role in the dynamics of the attached cavitation at the small ultrasonic horn. Also the variation of the experimental geometry, within a certain range, did not change the dynamics. We believe that the main two reasons for the peculiar dynamics of cavitation on a small ultrasonic horn are the higher energy density on a small tip and the inability of the big tip to "wash" away the gaseous bubbles. Calculation of the somewhat adapted Strouhal number revealed that, similar to the hydrodynamic cavitation, values which are relatively low characterize slow cavitation structure dynamics. In cases where the cavitation follows the driving frequency this value lies much higher - probably at Str > 20. In the spirit to distinguish the observed phenomenon with other cavitation dynamics at ultrasonic transducer surfaces, we suggest to term the observed phenomenon of attached cavities partly covering the full horn

The influence of surface roughness on cloud cavitation flow around hydrofoils

Science.gov (United States)

Hao, Jiafeng; Zhang, Mindi; Huang, Xu

2018-02-01

The aim of this study is to investigate experimentally the effect of surface roughness on cloud cavitation around Clark-Y hydrofoils. High-speed video and particle image velocimetry (PIV) were used to obtain cavitation patterns images (Prog. Aerosp. Sci. 37: 551-581, 2001), as well as velocity and vorticity fields. Results are presented for cloud cavitating conditions around a Clark-Y hydrofoil fixed at angle of attack of α =8{°} for moderate Reynolds number of Re=5.6 × 105. The results show that roughness had a great influence on the pattern, velocity and vorticity distribution of cloud cavitation. For cavitating flow around a smooth hydrofoil (A) and a rough hydrofoil (B), cloud cavitation occurred in the form of finger-like cavities and attached subulate cavities, respectively. The period of cloud cavitation around hydrofoil A was shorter than for hydrofoil B. Surface roughness had a great influence on the process of cloud cavitation. The development of cloud cavitation around hydrofoil A consisted of two stages: (1) Attached cavities developed along the surface to the trailing edge; (2) A reentrant jet developed, resulting in shedding and collapse of cluster bubbles or vortex structure. Meanwhile, its development for hydrofoil B included three stages: (1) Attached cavities developed along the surface to the trailing edge, with accumulation and rotation of bubbles at the trailing edge of the hydrofoil affecting the flow field; (2) Development of a reentrant jet resulted in the first shedding of cavities. Interaction and movement of flows from the pressure side and suction side brought liquid water from the pressure side to the suction side of the hydrofoil, finally forming a reentrant jet. The jet kept moving along the surface to the leading edge of the hydrofoil, resulting in large-scale shedding of cloud bubbles. Several vortices appeared and dissipated during the process; (3) Cavities grew and shed again.

Numerical Modeling of Cavitating Venturi: A Flow Control Element of Propulsion System

Science.gov (United States)

Majumdar, Alok; Saxon, Jeff (Technical Monitor)

2002-01-01

In a propulsion system, the propellant flow and mixture ratio could be controlled either by variable area flow control valves or by passive flow control elements such as cavitating venturies. Cavitating venturies maintain constant propellant flowrate for fixed inlet conditions (pressure and temperature) and wide range of outlet pressures, thereby maintain constant, engine thrust and mixture ratio. The flowrate through the venturi reaches a constant value and becomes independent of outlet pressure when the pressure at throat becomes equal to vapor pressure. In order to develop a numerical model of propulsion system, it is necessary to model cavitating venturies in propellant feed systems. This paper presents a finite volume model of flow network of a cavitating venturi. The venturi was discretized into a number of control volumes and mass, momentum and energy conservation equations in each control volume are simultaneously solved to calculate one-dimensional pressure, density, and flowrate and temperature distribution. The numerical model predicts cavitations at the throat when outlet pressure was gradually reduced. Once cavitation starts, with further reduction of downstream pressure, no change in flowrate is found. The numerical predictions have been compared with test data and empirical equation based on Bernoulli's equation.

Cavitation characteristics of multihole diesel-fuel nozzles in high-speed oil flows. Diesel kikan yo nenryo tako nozzle no abura cavitation tokusei

Energy Technology Data Exchange (ETDEWEB)

Yokota, M. (Shimonoseki Univ. of Fisheris, Yamaguchi (Japan)); Ito, Y. (Hachinohe Inst. of Tech., Aomori (Japan)); Aoki, H. (Xexel-Gleason U.S.A. Inc., New York (U.S.A))

1991-07-25

Recently, since higher velocity and higher pressure are required for diesel injection systems, cavitation behaviors in high velocity oil flows are strongly interested in such as 100 to 500 m/s for oil flow velocity and less than the cavitation factor {sigma} of 0.01. In this paper, oil cavitation characteristics at the injection part of multihole nozzles, especially on the flow characteristics, were studied systematically using fuel injection multihole nozzles for an actual use. As a result, it was clarified that subcavitation area (sub C), transition area, and supercavitation area (SC) could be existing in C{sub d}-{sigma} relation, which was similar to that specified cavitation conditions could be exisiting in the actual working area of multihole nozzles. And it was also clarified that flow coefficient C{sub d} relied on Reynolds number R{sub e} in the transition of {sigma}{ge}{sigma}{sub cr} and in {sub C} area, and mainly relied on {sigma} in SC area of {sigma}<{sigma}{sub cr}. Moreover, it was also confirmed that such tendency was similar to the one of the two-dimensional contraction of an area. 22 refs., 10 figs., 1 tab.

Detection of cavitation in hydraulic turbines

Science.gov (United States)

Escaler, Xavier; Egusquiza, Eduard; Farhat, Mohamed; Avellan, François; Coussirat, Miguel

2006-05-01

An experimental investigation has been carried out in order to evaluate the detection of cavitation in actual hydraulic turbines. The methodology is based on the analysis of structural vibrations, acoustic emissions and hydrodynamic pressures measured in the machine. The proposed techniques have been checked in real prototypes suffering from different types of cavitation. In particular, one Kaplan, two Francis and one Pump-Turbine have been investigated in the field. Additionally, one Francis located in a laboratory has also been tested. First, a brief description of the general features of cavitation phenomenon is given as well as of the main types of cavitation occurring in hydraulic turbines. The work presented here is focused on the most important ones which are the leading edge cavitation due to its erosive power, the bubble cavitation because it affects the machine performance and the draft tube swirl that limits the operation stability. Cavitation detection is based on the previous understanding of the cavity dynamics and its location inside the machine. This knowledge has been gained from flow visualisations and measurements in laboratory devices such as a high-speed cavitation tunnel and a reduced scale turbine test rig. The main techniques are the study of the high frequency spectral content of the signals and of their amplitude demodulation for a given frequency band. Moreover, low frequency spectral content can also be used in certain cases. The results obtained for the various types of cavitation found in the selected machines are presented and discussed in detail in the paper. Conclusions are drawn about the best sensor, measuring location, signal processing and analysis for each type of cavitation, which serve to validate and to improve the detection techniques.

Improvement of residual stress in stainless steel by cavitating jet; Cavitation funryu ni yoru stainless ko no zanryu oryoku kaizen

Energy Technology Data Exchange (ETDEWEB)

Soyama, H.; Saka, M. [Tohoku Univ., Sendai (Japan)] Park, J. [Kyung Nam Junior College, Pusan (Korea, Republic of). Dept. Vehicle Eng.] Abe, H. [Tohoku Univ., Sendai (Japan)

1998-08-15

In order to strengthen materials, the improvement of residual stress in stainless steel by using a cavitating jet was investigated. In case of cavitating jet, the cavitation intensity can be controlled by hydraulic parameters such as upstream pressure and downstream pressure. In general, cavitation produces damage on hydraulic machinery. However, at the initial stage of cavitation erosion process, plastic deformation takes place on the material surface, then it is possible to do peening without damage considering the cavitation intensity and the exposure time. In order to evidence the suitable condition on the improvement of residual stress by the cavitating jet, the residual stress in SUS304 and SUS316 was examined. The three normal stresses in different directions were measured by X-ray diffraction method, then the principal stresses were calculated. Both principal stresses were changed from tension to compression within 10 seconds by the cavitating jet. The compressive stress resulted by the cavitating jet was saturated after a certain time. It was concluded that the cavitating jet improved the residual stress in stainless steel SUS316 as well as SUS304. 24 refs., 9 figs.

Application of hydrodynamic cavitation to improve the biodegradability of mature landfill leachate.

Science.gov (United States)

Bis, M; Montusiewicz, A; Ozonek, J; Pasieczna-Patkowska, S

2015-09-01

In this study, the application of hydrodynamic cavitation to improve the biodegradability of mature landfill leachate was investigated. Three configurations of cavitation device were examined and operational parameters of the process were selected. The study indicated that the orifice plate with a 3/10mm diameter conical concentric hole, characterized by the cavitation number of 0.033, is a reasonable choice to ensure the enhanced biodegradability of mature leachate. Using such a configuration and maintaining 30 recirculation passes through the cavitation zone at inlet pressure of 7 bar, the highest increase of biodegradability index (BI) of approximately 22% occurred, i.e., from the value of 0.046 to 0.056. The FT-IR/PAS analysis confirmed a degradation of refractory compounds that typically prevail in mature leachate. An evaluation of energy efficiency was made in terms of the actual consumed energy measured by using the Kyoritsu KEW6310 Power Quality Tester. A cavitational yield of 9.8 mg COD kJ(-1) was obtained for the optimum configuration and 30 recirculation passes. Regarding energy efficiency, the application of 10 cavitation cycles appeared to be the most profitable. This was due to an almost threefold higher cavitational yield of 27.5 mg COD kJ(-1). However, the preferable option should be selected by considering a satisfactory effect in the biodegradability enhancement. Copyright © 2015 Elsevier B.V. All rights reserved.

Spatiotemporal evolution of cavitation dynamics exhibited by flowing microbubbles during ultrasound exposure.

Science.gov (United States)

Choi, James J; Coussios, Constantin-C

2012-11-01

Ultrasound and microbubble-based therapies utilize cavitation to generate bioeffects, yet cavitation dynamics during individual pulses and across consecutive pulses remain poorly understood under physiologically relevant flow conditions. SonoVue(®) microbubbles were made to flow (fluid velocity: 10-40 mm/s) through a vessel in a tissue-mimicking material and were exposed to ultrasound [frequency: 0.5 MHz, peak-rarefactional pressure (PRP): 150-1200 kPa, pulse length: 1-100,000 cycles, pulse repetition frequency (PRF): 1-50 Hz, number of pulses: 10-250]. Radiated emissions were captured on a linear array, and passive acoustic mapping was used to spatiotemporally resolve cavitation events. At low PRPs, stable cavitation was maintained throughout several pulses, thus generating a steady rise in energy with low upstream spatial bias within the focal volume. At high PRPs, inertial cavitation was concentrated in the first 6.3 ± 1.3 ms of a pulse, followed by an energy reduction and high upstream bias. Multiple pulses at PRFs below a flow-dependent critical rate (PRF(crit)) produced predictable and consistent cavitation dynamics. Above the PRF(crit), energy generated was unpredictable and spatially biased. In conclusion, key parameters in microbubble-seeded flow conditions were matched with specific types, magnitudes, distributions, and durations of cavitation; this may help in understanding empirically observed in vivo phenomena and guide future pulse sequence designs.

Some Cavitation Properties of Liquids

Directory of Open Access Journals (Sweden)

K. D. Efremova

2016-01-01

Full Text Available Cavitation properties of liquid must be taken into consideration in the engineering design of hydraulic machines and hydro devices when there is a possibility that in their operation an absolute pressure in the liquid drops below atmospheric one, and for a certain time the liquid is in depression state. Cold boiling, which occurs at a comparatively low temperature under a reduced absolute pressure within or on the surface of the liquid is regarded as hydrostatic cavitation if the liquid is stationary or as hydrodynamic cavitation, if the liquid falls into conditions when in the flow cross-section there is a sharply increasing dynamic pressure and a dropping absolute pressure.In accordance with the theory of cavitation, the first phase of cavitation occurs when the absolute pressure of the degassed liquid drops to the saturated vapour pressure, and the air dissolved in the liquid, leaving the intermolecular space, is converted into micro-bubbles of combined air and becomes a generator of cavitation “nuclei”. A quantitative estimate of the minimum allowable absolute pressure in a real, fully or partially degassed liquid at which a hydrostatic cavitation occurs is of practical interest.Since the pressure of saturated vapour of a liquid is, to a certain extent, related to the forces of intermolecular interaction, it is necessary to have information on the cavitation properties of technical solutions, including air solution in a liquid, as a solute may weaken intermolecular bonds and affect the pressure value of the saturated solvent vapour. In the experiment to carry out vacuum degassing of liquids was used a hydraulic air driven vacuum pump.The paper presents hydrostatic and hydrodynamic degassing liquid processes used in the experiment.The experimental studies of the cavitation properties of technical liquids (sea and distilled water, saturated NaCl solution, and pure glycerol and as a 49/51% solution in water, mineral oil and jet fuel enabled

Fracture of elastomers by cavitation

KAUST Repository

Hamdi, Adel

2014-01-01

Cavitation phenomenon is studied in rubber-like materials by combining experimental, theoretical and numerical approaches. Specific tests are carried out on a Styrene Butadiene Rubber to point out main characteristics of cavitation phenomenon. Hydrostatic depression is numerically modelled using finite element method. Numerical results are compared to Ball\\'s and Hou & Abeyaratne\\'s models with regard to cavity nucleation in the material. Both models well fit experimental observations suggesting that the cavitation nucleation in elastomers depends on the confinement degree of the specimen. Finally, critical hydrostatic pressure and critical global deformation are proved to govern cavitation nucleation in the studied material. Critical loadings are identified by comparing experimental and numerical load-displacement curves. © 2013 Elsevier Ltd.

Kidney stone erosion by micro scale hydrodynamic cavitation and consequent kidney stone treatment.

Science.gov (United States)

Perk, Osman Yavuz; Şeşen, Muhsincan; Gozuacik, Devrim; Koşar, Ali

2012-09-01

The objective of this study is to reveal the potential of micro scale hydrodynamic bubbly cavitation for the use of kidney stone treatment. Hydrodynamically generated cavitating bubbles were targeted to the surfaces of 18 kidney stone samples made of calcium oxalate, and their destructive effects were exploited in order to remove kidney stones in in vitro experiments. Phosphate buffered saline (PBS) solution was used as the working fluid under bubbly cavitating conditions in a 0.75 cm long micro probe of 147 μm inner diameter at 9790 kPa pressure. The surface of calcium oxalate type kidney stones were exposed to bubbly cavitation at room temperature for 5 to 30 min. The eroded kidney stones were visually analyzed with a high speed CCD camera and using SEM (scanning electron microscopy) techniques. The experiments showed that at a cavitation number of 0.017, hydrodynamic bubbly cavitation device could successfully erode stones with an erosion rate of 0.31 mg/min. It was also observed that the targeted application of the erosion with micro scale hydrodynamic cavitation may even cause the fracture of the kidney stones within a short time of 30 min. The proposed treatment method has proven to be an efficient instrument for destroying kidney stones.

Acoustic methods for cavitation mapping in biomedical applications

Science.gov (United States)

Wan, M.; Xu, S.; Ding, T.; Hu, H.; Liu, R.; Bai, C.; Lu, S.

2015-12-01

In recent years, cavitation is increasingly utilized in a wide range of applications in biomedical field. Monitoring the spatial-temporal evolution of cavitation bubbles is of great significance for efficiency and safety in biomedical applications. In this paper, several acoustic methods for cavitation mapping proposed or modified on the basis of existing work will be presented. The proposed novel ultrasound line-by-line/plane-by-plane method can depict cavitation bubbles distribution with high spatial and temporal resolution and may be developed as a potential standard 2D/3D cavitation field mapping method. The modified ultrafast active cavitation mapping based upon plane wave transmission and reception as well as bubble wavelet and pulse inversion technique can apparently enhance the cavitation to tissue ratio in tissue and further assist in monitoring the cavitation mediated therapy with good spatial and temporal resolution. The methods presented in this paper will be a foundation to promote the research and development of cavitation imaging in non-transparent medium.

An experimental investigation of artificial supercavitation generated by air injection behind disk-shaped cavitators

Directory of Open Access Journals (Sweden)

Byoung-Kwon Ahn

2017-03-01

Full Text Available In this paper, we investigated physical characteristics of an artificial supercavity generated behind an axisymmetric cavitator. Experiments for the same model were carried out at two different cavitation tunnels of the Chungnam National University and the University of Minnesota, and the results were compared and verified with each other. We measured pressures inside the cavity and observed the cavity formation by using a high-speed camera. Cavitation parameters were evaluated in considering blockage effects of the tunnel, and gravitational effects on supercavity dimensions were examined. Cavity dimensions corresponding to the unbounded cavitation number were compared. In addition, we investigated how artificial supercavitation develops according to the combination of injection positions and direction.

Degradation of organic wastewater by hydrodynamic cavitation combined with acoustic cavitation.

Science.gov (United States)

Yi, Chunhai; Lu, Qianqian; Wang, Yun; Wang, Yixuan; Yang, Bolun

2018-05-01

In this paper, the decomposition of Rhodamine B (RhB) by hydrodynamic cavitation (HC), acoustic cavitation (AC) and the combination of these individual methods (HAC) have been investigated. The degradation of 20 L RhB aqueous solution was carried out in a self-designed HAC reactor, where hydrodynamic cavitation and acoustic cavitation could take place in the same space simultaneously. The effects of initial concentration, inlet pressure, solution temperature and ultrasonic power were studied and discussed. Obvious synergies were found in the HAC process. The combined method achieved the best conversion, and the synergistic effect in HAC was even up to 119% with the ultrasonic power of 220 W in a treatment time of 30 min. The time-independent synergistic factor based on rate constant was introduced and the maximum value reached 40% in the HAC system. Besides, the hybrid HAC method showed great superiority in energy efficiency at lower ultrasonic power (88-176 W). Therefore, HAC technology can be visualized as a promising method for wastewater treatment with good scale-up possibilities. Copyright © 2018 Elsevier B.V. All rights reserved.

Bulk coolant cavitation in LMFBR containment loading following a whole-core explosion

International Nuclear Information System (INIS)

Jones, A.V.

1977-01-01

An LMFBR core undergoing an explosion transmits energy to the containment in a series of pressure waves and the containment loading is determined by their cumulative effect. These pressure waves are modified by their interaction with the coolant through which they propagate. It is necessary to model both the induction of bulk cavitation by tension waves and the interaction of pressure waves with cavitated liquid in realistic containment loading calculations. This paper sets out the progress which has been achieved in such modelling and first indications for the effect of bulk coolant cavitation in LMFBR containment loading. Conclusions may be briefly summarised: 1) Bulk cavitation must be included in realistic containment loading calculations. 2) Phenomenological models of cavitated liquid without memory are inappropriate. The best approach is to model bubble dynamics directly, including at least momentum conservation and surface tension. 3) The containment loading resulting from a given explosion is sensitive to the state of preparation of the coolant. The number density of nucleation sites should therfore accompany the results of model tests. (Auth.)

Study of physical and biological factors involved in the disruption of E. coli by hydrodynamic cavitation.

Science.gov (United States)

Balasundaram, B; Harrison, S T L

2006-01-01

Hydrodynamic cavitation results in flow restriction in a flow system causing rapid pressure fluctuations and significant fluid forces. These can be harnessed to mediate microbial cell damage. Hydrodynamic cavitation was studied for the partial disruption of E. coli and selective release of specific proteins relative to the total soluble protein. The effects of the cavitation number, the number of passes, and the specific growth rate of E. coli on the release of periplasmic and cytoplasmic proteins were studied. At the optimum cavitation number of 0.17 for this experimental configuration, 48% of the total soluble protein, 88% of acid phosphatase, and 67% of beta-galactosidase were released by hydrodynamic cavitation in comparison with the maximum release attained using multiple passes through the French Press. The higher release of the acid phosphatase over the total soluble protein suggested preferred release of periplasmic compounds. This was supported by SDS-PAGE analysis. The absence of micronization of cell material resulting in the potential for ease of solid-liquid separation downstream of the cell disruption operation was confirmed by TEM microscopy. E. coli cells cultivated at a higher specific growth rate (0.36 h(-1)) were more easily disrupted than slower grown cells (0.11 h(-1)). The specific activity of the enzyme of interest released by hydrodynamic cavitation, defined as the units of enzyme in solution per milligram of total soluble protein, was greater than that obtained on release by the French Press, high-pressure homogenization, osmotic shock, and EDTA treatment. The selectivity offered indicates the potential of enzyme release by hydrodynamic cavitation to ease the purification in the subsequent downstream processing.

Stochastic-field cavitation model

International Nuclear Information System (INIS)

Dumond, J.; Magagnato, F.; Class, A.

2013-01-01

Nonlinear phenomena can often be well described using probability density functions (pdf) and pdf transport models. Traditionally, the simulation of pdf transport requires Monte-Carlo codes based on Lagrangian “particles” or prescribed pdf assumptions including binning techniques. Recently, in the field of combustion, a novel formulation called the stochastic-field method solving pdf transport based on Eulerian fields has been proposed which eliminates the necessity to mix Eulerian and Lagrangian techniques or prescribed pdf assumptions. In the present work, for the first time the stochastic-field method is applied to multi-phase flow and, in particular, to cavitating flow. To validate the proposed stochastic-field cavitation model, two applications are considered. First, sheet cavitation is simulated in a Venturi-type nozzle. The second application is an innovative fluidic diode which exhibits coolant flashing. Agreement with experimental results is obtained for both applications with a fixed set of model constants. The stochastic-field cavitation model captures the wide range of pdf shapes present at different locations

Stochastic-field cavitation model

Science.gov (United States)

Dumond, J.; Magagnato, F.; Class, A.

2013-07-01

Nonlinear phenomena can often be well described using probability density functions (pdf) and pdf transport models. Traditionally, the simulation of pdf transport requires Monte-Carlo codes based on Lagrangian "particles" or prescribed pdf assumptions including binning techniques. Recently, in the field of combustion, a novel formulation called the stochastic-field method solving pdf transport based on Eulerian fields has been proposed which eliminates the necessity to mix Eulerian and Lagrangian techniques or prescribed pdf assumptions. In the present work, for the first time the stochastic-field method is applied to multi-phase flow and, in particular, to cavitating flow. To validate the proposed stochastic-field cavitation model, two applications are considered. First, sheet cavitation is simulated in a Venturi-type nozzle. The second application is an innovative fluidic diode which exhibits coolant flashing. Agreement with experimental results is obtained for both applications with a fixed set of model constants. The stochastic-field cavitation model captures the wide range of pdf shapes present at different locations.

Laser-nucleated acoustic cavitation in focused ultrasound.

Science.gov (United States)

Gerold, Bjoern; Kotopoulis, Spiros; McDougall, Craig; McGloin, David; Postema, Michiel; Prentice, Paul

2011-04-01

Acoustic cavitation can occur in therapeutic applications of high-amplitude focused ultrasound. Studying acoustic cavitation has been challenging, because the onset of nucleation is unpredictable. We hypothesized that acoustic cavitation can be forced to occur at a specific location using a laser to nucleate a microcavity in a pre-established ultrasound field. In this paper we describe a scientific instrument that is dedicated to this outcome, combining a focused ultrasound transducer with a pulsed laser. We present high-speed photographic observations of laser-induced cavitation and laser-nucleated acoustic cavitation, at frame rates of 0.5×10(6) frames per second, from laser pulses of energy above and below the optical breakdown threshold, respectively. Acoustic recordings demonstrated inertial cavitation can be controllably introduced to the ultrasound focus. This technique will contribute to the understanding of cavitation evolution in focused ultrasound including for potential therapeutic applications. © 2011 American Institute of Physics

Cavitation nuclei measurements - A review

International Nuclear Information System (INIS)

Billet, M.L.

1985-01-01

The measurement of cavitation nuclei has been the goal of many cavitation research laboratories and has resulted in the development of many methods. Two significantly different approaches have been developed. One is to measure the particulate-microbubble distribution by utilizing acoustical, electrical or optical methods. The other approach measures a liquid tension and a rate of cavitation events for a liquid in order to establish a cavitation susceptibility. Comparisons between various methods indicate that most methods are capable of giving an indication of the nuclei distribution. Measurements obtained in the ocean environment indicate an average of three bubbles per cubic centimeter are present; whereas, water tunnel bubble distributions vary from much less than one to over a hundred per cubic centimeter

Towards the concept of hydrodynamic cavitation control

Science.gov (United States)

Chatterjee, Dhiman; Arakeri, Vijay H.

1997-02-01

A careful study of the existing literature available in the field of cavitation reveals the potential of ultrasonics as a tool for controlling and, if possible, eliminating certain types of hydrodynamic cavitation through the manipulation of nuclei size present in a flow. A glass venturi is taken to be an ideal device to study the cavitation phenomenon at its throat and its potential control. A piezoelectric transducer, driven at the crystal resonant frequency, is used to generate an acoustic pressure field and is termed an ‘ultrasonic nuclei manipulator (UNM)’. Electrolysis bubbles serve as artificial nuclei to produce travelling bubble cavitation at the venturi throat in the absence of a UNM but this cavitation is completely eliminated when a UNM is operative. This is made possible because the nuclei, which pass through the acoustic field first, cavitate, collapse violently and perhaps fragment and go into dissolution before reaching the venturi throat. Thus, the potential nuclei for travelling bubble cavitation at the venturi throat seem to be systematically destroyed through acoustic cavitation near the UNM. From the solution to the bubble dynamics equation, it has been shown that the potential energy of a bubble at its maximum radius due to an acoustic field is negligible compared to that for the hydrodynamic field. Hence, even though the control of hydrodynamic macro cavitation achieved in this way is at the expense of acoustic micro cavitation, it can still be considered to be a significant gain. These are some of the first results in this direction.

International Symposium of Cavitation and Multiphase Flow (ISCM 2014)

International Nuclear Information System (INIS)

Wu, Yulin

2015-01-01

The International Symposium on Cavitation and Multiphase Flow (ISCM 2014) was held in Beijing, China during 18th-21st October, 2014, which was jointly organized by Tsinghua University, Beijing, China and Jiangsu University, Zhenjiang, China. The co-organizer was the State Key Laboratory of Hydroscience and Engineering, Beijing, China. Cavitation and multiphase flow is one of paramount topics of fluid mechanics with many engineering applications covering a broad range of topics, e.g. hydraulic machinery, biomedical engineering, chemical and process industry. In order to improve the performances of engineering facilities (e.g. hydraulic turbines) and to accelerate the development of techniques for medical treatment of serious diseases (e.g. tumors), it is essential to improve our understanding of cavitation and Multiphase Flow. For example, the present development towards the advanced hydrodynamic systems (e.g. space engine, propeller, hydraulic machinery system) often requires that the systems run under cavitating conditions and the risk of cavitation erosion needs to be controlled. The purpose of the ISCM 2014 was to discuss the state-of-the-art cavitation and multiphase flow research and their up-to-date applications, and to foster discussion and exchange of knowledge, and to provide an opportunity for the researchers, engineers and graduate students to report their latest outputs in these fields. Furthermore, the participants were also encouraged to present their work in progress with short lead time and discuss the encountered problems. ISCM 2014 covers all aspects of cavitation and Multiphase Flow, e.g. both fundamental and applied research with a focus on physical insights, numerical modelling and applications in engineering. Some specific topics are: Cavitating and Multiphase Flow in hydroturbines, pumps, propellers etc. Numerical simulation techniques Cavitation and multiphase flow erosion and anti-erosion techniques Measurement techniques for cavitation and

Tip-leakage cavitation in the clearance of a 2D hydrofoil with fillets: high-speed visualization and PIV/PTV measurements

Science.gov (United States)

Zapryagaev, Ivan I.; Timoshevskiy, Mikhail V.; Pervunin, Konstantin S.

2017-09-01

Tip-clearance cavitation is one of the most aggressive forms of cavitation as it can cause surface erosion of hydraulic machinery elements and, as a result, their fatigue damage and disturb designed operating conditions. At present, the literature lacks for detailed experimental data on the inception and development of this type of cavitation at various flow conditions. In the paper, a tip-leakage cavitation occurring in the clearance between an end face of a 2D hydrofoil (a scaled-down model of guide vanes (GV) of a Francis turbine) and a transparent wall of the test section was studied. The experiments were carried out for different cavitating regimes on the cavitation number and two attack angles of 3° and 9°, with the gap size (tip clearance width) varied in the range from 0.4 to 0.8 mm. In order to determine the cavitation inception conditions and investigate the dynamics of the tip-leakage cavitation, a high-speed visualization was applied. A modified PIV/PTV technique with a diverging laser beam instead of a laser light sheet was used to measure the mean velocity distributions within the gap. It was shown that the cavitation pattern on the suction side of the GV model impacts the dynamics of the leakage flow in the gap but does not affect the sheet cavity formed close to the foil leading edge in the clearance as well as its size and dynamics. When the gap size is increased, the tip-leakage cavitation initiates at higher cavitation numbers or, in other words, conditions for the cavitation occurrence become more favorable.

Diagnostic Value of Conventional and Digital Radiography for Detection of Cavitated and Non-Cavitated Proximal Caries

Directory of Open Access Journals (Sweden)

Mahdieh Dehghani

2017-02-01

Full Text Available Objectives: This study aimed to assess the diagnostic value of conventional and digital radiography for detection of cavitated and non-cavitated proximal caries.Materials and Methods: Fifty extracted human premolars and molars were mounted in a silicone block. Charge-coupled device (CCD and photostimulable phosphor plate (PSP receptors and intra-oral films were exposed with 60 and 70 kVp with parallel technique. Two observers interpreted the radiographs twice with a two-week interval using a 5-point scale. Teeth were then serially sectioned in mesiodistal direction and evaluated under a stereomicroscope (gold standard. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were calculated.Results: Sensitivity of all three receptors for detection of enamel lesions was low (5.5-44.4% but it was higher for dentin lesions (42.8-62.8%; PSP with 70 kVp and 0.03s exposure time had the highest sensitivity for enamel lesions, but the difference among receptors was not statistically significant (P>0.05. Sensitivity of all three receptors for detection of non-cavitated lesions was lower than that for cavitated lesions; PSP with 60 kVp and 0.07s exposure time had higher sensitivity and lower patient radiation dose for detection of cavitated and non-cavitated lesions, but the difference was not significant (P>0.05.Conclusions: Digital radiography using PSP receptor with 70 kVp is recommended to detect initial enamel caries. For detection of non-cavitated and cavitated dentin caries, PSP with 60 kVp is more appropriate. Change in kVp did not affect the diagnostic accuracy for detection of caries, and type of receptor was a more important factor.Keywords: Dental Caries; Diagnostic Imaging; Radiography, Dental, Digital

Cavitation and multiphase flow forum - 1985

International Nuclear Information System (INIS)

Hoyt, J.W.; Furuya, O.

1985-01-01

This book presents the papers given at a conference on fluid flow. Topics considered at the conference included cavitation inception, bubble growth, cavitation noise, holography, axial flow pumps, vortices, cavitation erosion, two-phase flow in nozzles, coal slurry valves, hopper flows of granular materials, helium bubble transport in a closed vertical duct, and a numerical model for flow in a venturi scrubber

Performance and cavitation characteristics of bi-directional hydrofoils

Science.gov (United States)

Nedyalkov, Ivaylo; Wosnik, Martin

2013-11-01

Tidal turbines extract energy from flows which reverse direction. One way to address this bi-directionality in horizontal axis turbines that avoid the use of complex and maintenance-intensive yaw or blade pitch mechanisms, is to design bi-directional blades which perform (equally) well in either flow direction. A large number of proposed hydrofoil designs were investigated using numerical simulations. Selected candidate foils were also tested (at various speeds and angles of attack) in the High-Speed Cavitation Tunnel (HICaT) at the University of New Hampshire. Lift and drag were measured using a force balance, and cavitation inception and desinence were recorded. Experimental and numerical results were compared, and the foils were compared to each other and to reference foils. Bi-directional hydrofoils may provide a feasible solution to the problem of reversing flow direction, when their performance and cavitation characteristics are comparable to those for unidirectional foils, and the penalty in decreased energy production is outweighed by the cost reduction due to lower complexity and respectively lower installation and maintenance costs.

Incipient Fault Detection for Rolling Element Bearings under Varying Speed Conditions.

Science.gov (United States)

Xue, Lang; Li, Naipeng; Lei, Yaguo; Li, Ningbo

2017-06-20

Varying speed conditions bring a huge challenge to incipient fault detection of rolling element bearings because both the change of speed and faults could lead to the amplitude fluctuation of vibration signals. Effective detection methods need to be developed to eliminate the influence of speed variation. This paper proposes an incipient fault detection method for bearings under varying speed conditions. Firstly, relative residual (RR) features are extracted, which are insensitive to the varying speed conditions and are able to reflect the degradation trend of bearings. Then, a health indicator named selected negative log-likelihood probability (SNLLP) is constructed to fuse a feature set including RR features and non-dimensional features. Finally, based on the constructed SNLLP health indicator, a novel alarm trigger mechanism is designed to detect the incipient fault. The proposed method is demonstrated using vibration signals from bearing tests and industrial wind turbines. The results verify the effectiveness of the proposed method for incipient fault detection of rolling element bearings under varying speed conditions.

Analysis of cavitation effect for water purifier using electrolysis

Science.gov (United States)

Shin, Dong Ho; Ko, Han Seo; Lee, Seung Ho

2015-11-01

Water is a limited and vital resource, so it should not be wasted by pollution. A development of new water purification technology is urgent nowadays since the original and biological treatments are not sufficient. The microbubble-aided method was investigated for removal of algal in this study since it overcomes demerits of the existing purification technologies. Thus, the cavitation effect in a venturi-type tube using the electrolysis was analyzed. Ruthenium-coated titanium plates were used as electrodes. Optimum electrode interval and applied power were determined for the electrolysis. Then, the optimized electrodes were installed in the venturi-type tube for generating cavitation. The cavitation effect could be enhanced without any byproduct by the bubbly flow induced by the electrolysis. The optimum mass flow rate and current were determined for the cavitation with the electrolysis. Finally, the visualization techniques were used to count the cell number of algal and microbubbles for the confirmation of the performance. As a result, the energy saving and high efficient water purifier was fabricated in this study. This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Korean government (MEST) (No. 2013R1A2A2A01068653).

Reflections on cavitation nuclei in water

DEFF Research Database (Denmark)

Mørch, Knud Aage

2007-01-01

to explaining why the tensile strength of water varies so dramatically between the experiments reported. A model for calculation of the critical pressure of skin-covered free gas bubbles as well as that of interfacial gaseous nuclei covered by a skin is presented. This model is able to bridge the apparently......The origin of cavitation bubbles, cavitation nuclei, has been a subject of debate since the early years of cavitation research. This paper presents an analysis of a representative selection of experimental investigations of cavitation inception and the tensile strength of water. At atmospheric...... pressure, the possibility of stabilization of free gas bubbles by a skin has been documented, but only within a range of bubble sizes that makes them responsible for tensile strengths up to about 1.5 bar, and values reaching almost 300 bar have been measured. However, cavitation nuclei can also be harbored...

Experimental measurements of the cavitating flow after horizontal water entry

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Thang Tat; Thai, Nguyen Quang; Phuong, Truong Thi [Institute of Mechanics (IMECH), Vietnam Academy of Science and Technology (VAST), 264—Doi Can, Ba Dinh, Hanoi (Viet Nam); Hai, Duong Ngoc, E-mail: ntthang@imech.vast.vn, E-mail: dnhai@vast.vn, E-mail: nqthai@imech.vast.vn, E-mail: ttphuong@imech.vast.vn [Graduate University of Science and Technology (GUST), VAST, 18—Hoang Quoc Viet, Cau Giay, Hanoi (Viet Nam)

2017-10-15

Water-entry cavitating flow is of considerable importance in underwater high-speed applications. That is because of the drag-reduction effect that concerns the presence of a cavity around moving objects. Though the study of the flow has long been carried out, little data are documented in literature so far. Besides, currently, in the case of unsteady flow, experimental measurements of some flow parameters such as the cavity pressure still encounter difficulties. Hence continuing research efforts are of important significance. The objective of this study is to investigate experimentally the unsteady cavitating flow after the horizontal water entry of projectiles. An experimental apparatus has been developed. Qualitative and quantitative optical visualizations of the flow have been carried out by using high-speed videography. Digital image processing has been applied to analyzing the recorded flow images. Based on the known correlations between the ellipsoidal super-cavity’s size and the corresponding cavitation number, the cavity pressure has been measured by utilizing the data of image processing. A comparison between the partial- and super-cavitating flow regimes is reported. The received results can be useful for the design of high-speed underwater projectiles. (paper)

Nucleation and cavitation in parahydrogen

International Nuclear Information System (INIS)

Pi, Martí; Barranco, Manuel; Navarro, Jesús; Ancilotto, Francesco

2012-01-01

Highlights: ► We have constructed a density functional (DF) for parahydrogen between 14 and 32 K. ► The experimental equation of state and the surface tension are well reproduced. ► We have investigated nucleation and cavitations processes in the metastable phase. ► We have obtained the electron bubble explosion within the capillary model. - Abstract: We have used a density functional approach to investigate thermal homogeneous nucleation and cavitation in parahydrogen. The effect of electrons as seeds of heterogeneous cavitation in liquid parahydrogen is also discussed within the capillary model.

Cavitation occurrence around ultrasonic dental scalers.

Science.gov (United States)

Felver, Bernhard; King, David C; Lea, Simon C; Price, Gareth J; Damien Walmsley, A

2009-06-01

Ultrasonic scalers are used in dentistry to remove calculus and other contaminants from teeth. One mechanism which may assist in the cleaning is cavitation generated in cooling water around the scaler. The vibratory motion of three designs of scaler tip in a water bath has been characterised by laser vibrometry, and compared with the spatial distribution of cavitation around the scaler tips observed using sonochemiluminescence from a luminol solution. The type of cavitation was confirmed by acoustic emission analysed by a 'Cavimeter' supplied by NPL. A node/antinode vibration pattern was observed, with the maximum displacement of each type of tip occurring at the free end. High levels of cavitation activity occurred in areas surrounding the vibration antinodes, although minimal levels were observed at the free end of the tip. There was also good correlation between vibration amplitude and sonochemiluminescence at other points along the scaler tip. 'Cavimeter' analysis correlated well with luminol observations, suggesting the presence of primarily transient cavitation.

The acoustic detection of cavitation in pumps

International Nuclear Information System (INIS)

Macleod, I.D.; Gray, B.S.; Taylor, C.G.

1978-01-01

A programme was initiated to develop a reliable technique for detecting the onset of acoustic noise from cavitation in a pump and to relate this to cavitation inception data, since significant noise from collapse of vapour bubbles arising from such cavitation would reduce the sensitivity of a noise detection system for boiling of sodium in fast breeder reactors. Factors affecting the detection of cavitation are discussed. The instrumentation and techniques of frequency analysis and pulse detection are described. Two examples are then given of the application of acoustic detection techniques under controlled conditions. It is concluded that acoustic detection can be a reliable method for detecting inception of cavitation in a pump and the required conditions are stated. (U.K.)

Cavitation control on a 2D hydrofoil through a continuous tangential injection of liquid: Experimental study

Science.gov (United States)

Timoshevskiy, M. V.; Zapryagaev, I. I.; Pervunin, K. S.; Markovich, D. M.

2016-10-01

In the paper, the possibility of active control of a cavitating flow over a 2D hydrofoil that replicates a scaled-down model of high-pressure hydroturbine guide vane (GV) was tested. The flow manipulation was implemented by a continuous tangential liquid injection at different flow rates through a spanwise slot in the foil surface. In experiments, the hydrofoil was placed in the test channel at the attack angle of 9°. Different cavitation conditions were reached by varying the cavitation number and injection velocity. In order to study time dynamics and spatial patterns of partial cavities, high-speed imaging was employed. A PIV method was used to measure the mean and fluctuating velocity fields over the hydrofoil. Hydroacoustic measurements were carried out by means of a pressure transducer to identify spectral characteristics of the cavitating flow. It was found that the present control technique is able to modify the partial cavity pattern (or even totally suppress cavitation) in case of stable sheet cavitation and change the amplitude of pressure pulsations at unsteady regimes. The injection technique makes it also possible to significantly influence the spatial distributions of the mean velocity and its turbulent fluctuations over the GV section for non-cavitating flow and sheet cavitation.

Kaplan turbine tip vortex cavitation - analysis and prevention

Science.gov (United States)

Motycak, L.; Skotak, A.; Kupcik, R.

2012-11-01

The work is focused on one type of Kaplan turbine runner cavitation - a tip vortex cavitation. For detailed description of the tip vortex, the CFD analysis is used. On the basis of this analysis it is possible to estimate the intensity of cavitating vortex core, danger of possible blade surface and runner chamber cavitation pitting. In the paper, the ways how to avoid the pitting effect of the tip vortex are described. In order to prevent the blade surface against pitting, the following possibilities as the change of geometry of the runner blade, dimension of tip clearance and finally the installation of the anti-cavitation lips are discussed. The knowledge of the shape and intensity of the tip vortex helps to design the anti-cavitation lips more sophistically. After all, the results of the model tests of the Kaplan runner with or without anti-cavitation lips and the results of the CFD analysis are compared.

Incipient Fault Detection for Rolling Element Bearings under Varying Speed Conditions

Directory of Open Access Journals (Sweden)

Lang Xue

2017-06-01

Full Text Available Varying speed conditions bring a huge challenge to incipient fault detection of rolling element bearings because both the change of speed and faults could lead to the amplitude fluctuation of vibration signals. Effective detection methods need to be developed to eliminate the influence of speed variation. This paper proposes an incipient fault detection method for bearings under varying speed conditions. Firstly, relative residual (RR features are extracted, which are insensitive to the varying speed conditions and are able to reflect the degradation trend of bearings. Then, a health indicator named selected negative log-likelihood probability (SNLLP is constructed to fuse a feature set including RR features and non-dimensional features. Finally, based on the constructed SNLLP health indicator, a novel alarm trigger mechanism is designed to detect the incipient fault. The proposed method is demonstrated using vibration signals from bearing tests and industrial wind turbines. The results verify the effectiveness of the proposed method for incipient fault detection of rolling element bearings under varying speed conditions.

Cavitation inception from bubble nuclei

DEFF Research Database (Denmark)

Mørch, Knud Aage

2015-01-01

, and experimental investigations of bubbles and cavitation inception have been presented. These results suggest that cavitation nuclei in equilibrium are gaseous voids in the water, stabilized by a skin which allows diffusion balance between gas inside the void and gas in solution in the surrounding liquid....... The cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure-time history of the water. A recent model...

Enhancing the aggressive intensity of hydrodynamic cavitation through a Venturi tube by increasing the pressure in the region where the bubbles collapse

Science.gov (United States)

Soyama, H.; Hoshino, J.

2016-04-01

In this paper, we used a Venturi tube for generating hydrodynamic cavitation, and in order to obtain the optimum conditions for this to be used in chemical processes, the relationship between the aggressive intensity of the cavitation and the downstream pressure where the cavitation bubbles collapse was investigated. The acoustic power and the luminescence induced by the bubbles collapsing were investigated under various cavitating conditions, and the relationships between these and the cavitation number, which depends on the upstream pressure, the downstream pressure at the throat of the tube and the vapor pressure of the test water, was found. It was shown that the optimum downstream pressure, i.e., the pressure in the region where the bubbles collapse, increased the aggressive intensity by a factor of about 100 compared to atmospheric pressure without the need to increase the input power. Although the optimum downstream pressure varied with the upstream pressure, the cavitation number giving the optimum conditions was constant for all upstream pressures.

Enhancing the aggressive intensity of hydrodynamic cavitation through a Venturi tube by increasing the pressure in the region where the bubbles collapse

Directory of Open Access Journals (Sweden)

H. Soyama

2016-04-01

Full Text Available In this paper, we used a Venturi tube for generating hydrodynamic cavitation, and in order to obtain the optimum conditions for this to be used in chemical processes, the relationship between the aggressive intensity of the cavitation and the downstream pressure where the cavitation bubbles collapse was investigated. The acoustic power and the luminescence induced by the bubbles collapsing were investigated under various cavitating conditions, and the relationships between these and the cavitation number, which depends on the upstream pressure, the downstream pressure at the throat of the tube and the vapor pressure of the test water, was found. It was shown that the optimum downstream pressure, i.e., the pressure in the region where the bubbles collapse, increased the aggressive intensity by a factor of about 100 compared to atmospheric pressure without the need to increase the input power. Although the optimum downstream pressure varied with the upstream pressure, the cavitation number giving the optimum conditions was constant for all upstream pressures.

FOREWORD: International Symposium of Cavitation and Multiphase Flow (ISCM 2014)

Science.gov (United States)

Wu, Yulin

2015-01-01

The International Symposium on Cavitation and Multiphase Flow (ISCM 2014) was held in Beijing, China during 18th-21st October, 2014, which was jointly organized by Tsinghua University, Beijing, China and Jiangsu University, Zhenjiang, China. The co-organizer was the State Key Laboratory of Hydroscience and Engineering, Beijing, China. Cavitation and multiphase flow is one of paramount topics of fluid mechanics with many engineering applications covering a broad range of topics, e.g. hydraulic machinery, biomedical engineering, chemical and process industry. In order to improve the performances of engineering facilities (e.g. hydraulic turbines) and to accelerate the development of techniques for medical treatment of serious diseases (e.g. tumors), it is essential to improve our understanding of cavitation and Multiphase Flow. For example, the present development towards the advanced hydrodynamic systems (e.g. space engine, propeller, hydraulic machinery system) often requires that the systems run under cavitating conditions and the risk of cavitation erosion needs to be controlled. The purpose of the ISCM 2014 was to discuss the state-of-the-art cavitation and multiphase flow research and their up-to-date applications, and to foster discussion and exchange of knowledge, and to provide an opportunity for the researchers, engineers and graduate students to report their latest outputs in these fields. Furthermore, the participants were also encouraged to present their work in progress with short lead time and discuss the encountered problems. ISCM 2014 covers all aspects of cavitation and Multiphase Flow, e.g. both fundamental and applied research with a focus on physical insights, numerical modelling and applications in engineering. Some specific topics are: Cavitating and Multiphase Flow in hydroturbines, pumps, propellers etc. Numerical simulation techniques Cavitation and multiphase flow erosion and anti-erosion techniques Measurement techniques for cavitation and

Cavitation occurrence around ultrasonic dental scalers

OpenAIRE

Felver, Bernhard; King, David C; Lea, Simon C; Price, Gareth J; Damien Walmsley, A

2009-01-01

Ultrasonic scalers are used in dentistry to remove calculus and other contaminants from teeth. One mechanism which may assist in the cleaning is cavitation generated in cooling water around the scaler. The vibratory motion of three designs of scaler tip in a water bath has been characterised by laser vibrometry, and compared with the spatial distribution of cavitation around the scaler tips observed using sonochemiluminescence from a luminol solution. The type of cavitation was confirmed by a...

Advanced experimental and numerical techniques for cavitation erosion prediction

CERN Document Server

Chahine, Georges; Franc, Jean-Pierre; Karimi, Ayat

2014-01-01

This book provides a comprehensive treatment of the cavitation erosion phenomenon and state-of-the-art research in the field. It is divided into two parts. Part 1 consists of seven chapters, offering a wide range of computational and experimental approaches to cavitation erosion. It includes a general introduction to cavitation and cavitation erosion, a detailed description of facilities and measurement techniques commonly used in cavitation erosion studies, an extensive presentation of various stages of cavitation damage (including incubation and mass loss), and insights into the contribution of computational methods to the analysis of both fluid and material behavior. The proposed approach is based on a detailed description of impact loads generated by collapsing cavitation bubbles and a physical analysis of the material response to these loads. Part 2 is devoted to a selection of nine papers presented at the International Workshop on Advanced Experimental and Numerical Techniques for Cavitation Erosion (Gr...

The role of cavitation in liposome formation.

Science.gov (United States)

Richardson, Eric S; Pitt, William G; Woodbury, Dixon J

2007-12-15

Liposome size is a vital parameter of many quantitative biophysical studies. Sonication, or exposure to ultrasound, is used widely to manufacture artificial liposomes, yet little is known about the mechanism by which liposomes are affected by ultrasound. Cavitation, or the oscillation of small gas bubbles in a pressure-varying field, has been shown to be responsible for many biophysical effects of ultrasound on cells. In this study, we correlate the presence and type of cavitation with a decrease in liposome size. Aqueous lipid suspensions surrounding a hydrophone were exposed to various intensities of ultrasound and hydrostatic pressures before measuring their size distribution with dynamic light scattering. As expected, increasing ultrasound intensity at atmospheric pressure decreased the average liposome diameter. The presence of collapse cavitation was manifested in the acoustic spectrum at high ultrasonic intensities. Increasing hydrostatic pressure was shown to inhibit the presence of collapse cavitation. Collapse cavitation, however, did not correlate with decreases in liposome size, as changes in size still occurred when collapse cavitation was inhibited either by lowering ultrasound intensity or by increasing static pressure. We propose a mechanism whereby stable cavitation, another type of cavitation present in sound fields, causes fluid shearing of liposomes and reduction of liposome size. A mathematical model was developed based on the Rayleigh-Plesset equation of bubble dynamics and principles of acoustic microstreaming to estimate the shear field magnitude around an oscillating bubble. This model predicts the ultrasound intensities and pressures needed to create shear fields sufficient to cause liposome size change, and correlates well with our experimental data.

Hydrodynamic cavitation characteristics of an orifice system and its effects on CRUD-like SiC deposition

International Nuclear Information System (INIS)

Kim, Seong Man; Bang, In Cheol

2016-01-01

Highlights: • CRUD-like SiC deposition was prepared for examining the erosion test in the cavitation field. • We investigated the comparison between swirl flow and common flow on cavitation. • Magnitude of shock pressure was investigated at low cavitation number. - Abstract: In a nuclear power plant, chalk river unidentified deposit (CRUD) is known as a deposit that is composed of corrosion and oxidation materials. It has a porous structure, which combines with boron that is injected into the coolant for controlling power levels. The buildup of corrosion products on the fuel cladding surface has proven to be particularly significant for both BWRs and PWRs. The high temperature of the cladding surface attracts impurities and chemical additives in the reactor coolant that deposit on the fuel rod surface in a process. The deposits on a fuel rod, known as CRUD, can be tenacious, insulative compounds capable of increasing the local clad temperature and accelerating clad corrosion—sometimes to the point of fuel failure. The deposition of CRUD on fuel cladding surfaces causes uneven heating of the reactor core. The situation is exacerbated by boron, which is added to the coolant to control power levels. However, boron becomes concentrated and is deposited within thick CRUD deposits. Ultrasonic mechanisms were developed but they have limitations for decontamination. In this experiment, a decontamination test was conducted using a sample sheet that was composed of SiC/water nanofluids. In addition, it was exposed to swirl flow and common flow for checking enhanced cavitation. It is measured by a pressure film, as shock pressure is associated with cavitation number. As a pressure film is wetted easily in water, it was injected into a holder. In the experiment, the maximum shock pressure was obtained during swirl flow at a low cavitation number. This indicates that pressure was concentrated on the pressure film. Consequently, cavitation can get rid of CRUD layers

Experimental Study of Cavitation in Laminar Flow

OpenAIRE

Croci , Kilian; Ravelet , Florent; ROBINET , Jean-Christophe; Danlos , Amélie

2017-01-01

An experimental setup has been especially developed in order to observe cavitation in laminar flows. Experiments have been carried out with a silicon oil of viscosity υ = 100cSt passing through a Venturi-type geometry with 18°/8° convergent/divergent angles respectively. The range of Reynolds numbers at the inlet section is between 350 and 1000. Two dynamic regimes are identified. They are characterized by two critical Reynolds numbers, induced by major hydrodynamic changes in the flow, in ad...

Actual status of sodium cavitation studies in Japan

International Nuclear Information System (INIS)

Yamamoto, K.; Kamiyama, S.; Hashimoto, H.; Mochizuki, K.; Nakai, Y.; Ishibashi, E.; Tamaoki, T.

1976-01-01

A cavitation test has been conducted on some components of the fast experimental reactor JOYO. Design is in progress for the fast proto-type reactor MONJU. Deliberate consideration has been taken against cavitation as this reactor will be operated under severer service conditions than that of JOYO. A cavitation test of entrance nozzles of MONJU fuel subassemblies was performed in water. In order to obtain design data a program of cavitation tests is planned

A critical pressure based panel method for prediction of unsteady loading of marine propellers under cavitation

International Nuclear Information System (INIS)

Liu, P.; Bose, N.; Colbourne, B.

2002-01-01

A simple numerical procedure is established and implemented into a time domain panel method to predict hydrodynamic performance of marine propellers with sheet cavitation. This paper describes the numerical formulations and procedures to construct this integration. Predicted hydrodynamic loads were compared with both a previous numerical model and experimental measurements for a propeller in steady flow. The current method gives a substantial improvement in thrust and torque coefficient prediction over a previous numerical method at low cavitation numbers of less than 2.0, where severe cavitation occurs. Predicted pressure coefficient distributions are also presented. (author)

Treatment of cyanide containing wastewater using cavitation based approach.

Science.gov (United States)

Jawale, Rajashree H; Gogate, Parag R; Pandit, Aniruddha B

2014-07-01

Industrial wastewater streams containing high concentrations of biorefractory materials like cyanides should ideally be treated at source. In the present work, degradation of potassium ferrocyanide (K4Fe(CN)6) as a model pollutant has been investigated using cavitational reactors with possible intensification studies using different approaches. Effect of different operating parameters such as initial concentration, temperature and pH on the extent of degradation using acoustic cavitation has been investigated. For the case of hydrodynamic cavitation, flow characteristics of cavitating device (venturi) have been established initially followed by the effect of inlet pressure and pH on the extent of degradation. Under the optimized set of operating parameters, the addition of hydrogen peroxide (ratio of K4Fe(CN)6:H2O2 varied from 1:1 to 1:30 mol basis) as process intensifying approach has been investigated. The present work has conclusively established that under the set of optimized operating parameters, cavitation can be effectively used for degradation of potassium ferrocyanide. The comparative study of hydrodynamic cavitation and acoustic cavitation suggested that hydrodynamic cavitation is more energy efficient and gives higher degradation as compared to acoustic cavitation for equivalent power/energy dissipation. The present work is the first one to report comparison of cavitation based treatment schemes for degradation of cyanide containing wastewaters. Copyright © 2014 Elsevier B.V. All rights reserved.

Study of formation mechanism of incipient melting in thixo-cast Al–Si–Cu–Mg alloys

Energy Technology Data Exchange (ETDEWEB)

Du, Kang, E-mail: du126kang@126.com; Zhu, Qiang, E-mail: zhu.qiang@grinm.com; Li, Daquan, E-mail: lidaquan@grinm.com; Zhang, Fan, E-mail: sk_zf@163.com

2015-08-15

Mechanical properties of thixo-cast Al–Si–Cu–Mg alloys can be enhanced by T61 heat treatment. Copper and magnesium atoms in aluminum matrix can form homogeneously distributed precipitations after solution and aging treatment which harden the alloys. However, microsegregation of these alloying elements could form numerous tiny multi-compound phases during solidification. These phases could cause incipient melting defects in subsequent heat treatment process and degrade the macro-mechanical properties of productions. This study is to present heterogeneous distribution of Cu, Si, and Mg elements and formation of incipient melting defects (pores). In this study, incipient melting pores that occurred during solution treatment at various temperatures, even lower than common melting points of various intermetallic phases, were identified, in terms of a method of investigating the same surface area in the samples before and after solution treatment in a vacuum environment. The results also show that the incipient melting mostly originates at the clusters with fine intermetallic particles while also some at the edge of block-like Al{sub 2}Cu. The fine particles were determined being Al{sub 2}Cu, Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} and Al{sub 8}Mg{sub 3}FeSi{sub 2}. Tendency of the incipient melting decreases with decreases of the width of the clusters. The formation mechanism of incipient melting pores in solution treatment process was discussed using both the Fick law and the LSW theory. Finally, a criterion of solution treatment to avoid incipient melting pores for the thixo-cast alloys is proposed. - Highlights: • In-situ comparison technique was used to analysis the change of eutectic phases. • The ralationship between eutectic phase size and incipient melting was studied. • Teat treatment criterion for higher incipient melting resistance was proposed.

Study of formation mechanism of incipient melting in thixo-cast Al–Si–Cu–Mg alloys

International Nuclear Information System (INIS)

Du, Kang; Zhu, Qiang; Li, Daquan; Zhang, Fan

2015-01-01

Mechanical properties of thixo-cast Al–Si–Cu–Mg alloys can be enhanced by T61 heat treatment. Copper and magnesium atoms in aluminum matrix can form homogeneously distributed precipitations after solution and aging treatment which harden the alloys. However, microsegregation of these alloying elements could form numerous tiny multi-compound phases during solidification. These phases could cause incipient melting defects in subsequent heat treatment process and degrade the macro-mechanical properties of productions. This study is to present heterogeneous distribution of Cu, Si, and Mg elements and formation of incipient melting defects (pores). In this study, incipient melting pores that occurred during solution treatment at various temperatures, even lower than common melting points of various intermetallic phases, were identified, in terms of a method of investigating the same surface area in the samples before and after solution treatment in a vacuum environment. The results also show that the incipient melting mostly originates at the clusters with fine intermetallic particles while also some at the edge of block-like Al 2 Cu. The fine particles were determined being Al 2 Cu, Al 5 Cu 2 Mg 8 Si 6 and Al 8 Mg 3 FeSi 2 . Tendency of the incipient melting decreases with decreases of the width of the clusters. The formation mechanism of incipient melting pores in solution treatment process was discussed using both the Fick law and the LSW theory. Finally, a criterion of solution treatment to avoid incipient melting pores for the thixo-cast alloys is proposed. - Highlights: • In-situ comparison technique was used to analysis the change of eutectic phases. • The ralationship between eutectic phase size and incipient melting was studied. • Teat treatment criterion for higher incipient melting resistance was proposed

A new concept for stainless steels ranking upon the resistance to cavitation erosion

Science.gov (United States)

Bordeasu, I.; Popoviciu, M. O.; Salcianu, L. C.; Ghera, C.; Micu, L. M.; Badarau, R.; Iosif, A.; Pirvulescu, L. D.; Podoleanu, C. E.

2017-01-01

In present, the ranking of materials as their resistance to cavitation erosion is obtained by using laboratory tests finalized with the characteristic curves mean depth erosion against time MDE(t) and mean depth erosion rate against time MDER(t). In some previous papers, Bordeasu and co-workers give procedures to establish exponential equation representing the curves, with minimum scatter of the experimental obtained results. For a given material, both exponential equations MDE(t) and MDER(t) have the same values for the parameters of scale and for the shape one. For the ranking of materials is sometimes important to establish single figure. Till now in Timisoara Polytechnic University Cavitation Laboratory were used three such numbers: the stable value of the curve MDER(t), the resistance to cavitation erosion (Rcav ≡ 1/MDERstable) and the normalized cavitation resistance Rns which is the rate between vs = MDERstable for the analyzed material and vse= MDERse the mean depth erosion rate for the steel OH12NDL (Rns = vs/vse ). OH12NDL is a material used for manufacturing the blades of numerous Kaplan turbines in Romania for which both cavitation erosion laboratory tests and field measurements of cavitation erosions are available. In the present paper we recommend a new method for ranking the materials upon cavitation erosion resistance. This method uses the scale and shape parameters of the exponential equations which represents the characteristic cavitation erosion curves. Till now the method was applied only for stainless steels. The experimental results show that the scale parameter represents an excellent method for ranking the stainless steels. In the future this kind of ranking will be tested also for other materials especially for bronzes used for manufacturing ship propellers.

Regulating Ultrasound Cavitation in order to Induce Reproducible Sonoporation

Science.gov (United States)

Mestas, J.-L.; Alberti, L.; El Maalouf, J.; Béra, J.-C.; Gilles, B.

2010-03-01

Sonoporation would be linked to cavitation, which generally appears to be a non reproducible and unstationary phenomenon. In order to obtain an acceptable trade-off between cell mortality and transfection, a regulated cavitation generator based on an acoustical cavitation measurement was developed and tested. The medium to be sonicated is placed in a sample tray. This tray is immersed in in degassed water and positioned above the face of a flat ultrasonic transducer (frequency: 445 kHz; intensity range: 0.08-1.09 W/cm2). This technical configuration was admitted to be conducive to standing-wave generation through reflection at the air/medium interface in the well thus enhancing the cavitation phenomenon. Laterally to the transducer, a homemade hydrophone was oriented to receive the acoustical signal from the bubbles. From this spectral signal recorded at intervals of 5 ms, a cavitation index was calculated as the mean of the cavitation spectrum integration in a logarithmic scale, and the excitation power is automatically corrected. The device generates stable and reproducible cavitation level for a wide range of cavitation setpoint from stable cavitation condition up to full-developed inertial cavitation. For the ultrasound intensity range used, the time delay of the response is lower than 200 ms. The cavitation regulation device was evaluated in terms of chemical bubble collapse effect. Hydroxyl radical production was measured on terephthalic acid solutions. In open loop, the results present a great variability whatever the excitation power. On the contrary the closed loop allows a great reproducibility. This device was implemented for study of sonodynamic effect. The regulation provides more reproducible results independent of cell medium and experimental conditions (temperature, pressure). Other applications of this regulated cavitation device concern internalization of different particles (Quantum Dot) molecules (SiRNA) or plasmids (GFP, DsRed) into different

Observations on Rotating Cavitation and Cavitation Surge From The Development of the Fastrac Engine Turbopump

Science.gov (United States)

Zoladz, Thomas F.; Turner, James E. (Technical Monitor)

2000-01-01

The effects of rotating cavitation and cavitation surges on the Fastrac Engine Turbopump are described in a viewgraph presentation format. The bent inducer blade dilemma and observations of unsteady data and oscillation components are discussed. The pump-feed system stability modeling assessment is outlined. Recommendations are made urging further investigation.

Seasonality of cavitation and frost fatigue in Acer mono Maxim.

Science.gov (United States)

Zhang, Wen; Feng, Feng; Tyree, Melvin T

2017-12-08

Although cavitation is common in plants, it is unknown whether the cavitation resistance of xylem is seasonally constant or variable. We tested the changes in cavitation resistance of Acer mono before and after a controlled cavitation-refilling and freeze-thaw cycles for a whole year. Cavitation resistance was determined from 'vulnerability curves' showing the percent loss of conductivity versus xylem tension. Cavitation fatigue was defined as a reduction of cavitation resistance following a cavitation-refilling cycle, whereas frost fatigue was caused by a freeze-thaw cycle. A. mono developed seasonal changes in native embolisms; values were relatively high during winter but relatively low and constant throughout the growing season. Cavitation fatigue occurred and changed seasonally during the 12-month cycle; the greatest fatigue response occurred during summer and the weakest during winter, and the transitions occurred during spring and autumn. A. mono was highly resistant to frost damage during the relatively mild winter months; however, a quite different situation occurred during the growing season, as the seasonal trend of frost fatigue was strikingly similar to that of cavitation fatigue. Seasonality changes in cavitation resistance may be caused by seasonal changes in the mechanical properties of the pit membranes. © 2017 John Wiley & Sons Ltd.

Cavitation damage of ceramics

International Nuclear Information System (INIS)

Kovalenko, V.I.; Marinin, V.G.

1988-01-01

Consideration is given to results of investigation of ceramic material damage under the effect of cavitation field on their surface, formed in water under the face of exponential concentrator, connected with ultrasonic generator UZY-3-0.4. Amplitude of vibrations of concentrator face (30+-2)x10 -6 m, frequency-21 kHz. It was established that ceramics resistance to cavitation effect correlated with the product of critical of stress intensity factor and material hardness

Energy Efficiency for Biodiesel Production by Combining Two Orifices in Hydrodynamic Cavitation Reactor

OpenAIRE

Mahlinda, Mahlinda; Djafar, Fitriana

2014-01-01

Research of energy efficiency for biodiesel production process by combining two orifices on  hydrodynamic cavitation reactor had been carried out. The aim of this reseach was to studied effect of the number of orifices toward increasing temperature without using external energy source to produce biodiesel that generated by cavitation effects on orifices. The results of preliminary research showed by combining two orifices arranged in series can produce the highest thermal energy reached 48oC....

Shear viscosity, cavitation and hydrodynamics at LHC

International Nuclear Information System (INIS)

Bhatt, Jitesh R.; Mishra, Hiranmaya; Sreekanth, V.

2011-01-01

We study evolution of quark-gluon matter in the ultrarelativistic heavy-ion collisions within the frame work of relativistic second-order viscous hydrodynamics. In particular, by using the various prescriptions of a temperature-dependent shear viscosity to the entropy ratio, we show that the hydrodynamic description of the relativistic fluid becomes invalid due to the phenomenon of cavitation. For most of the initial conditions relevant for LHC, the cavitation sets in very early stage. The cavitation in this case is entirely driven by the large values of shear viscosity. Moreover we also demonstrate that the conformal terms used in equations of the relativistic dissipative hydrodynamic can influence the cavitation time.

Measuring Cavitation with Synchrotron X-Rays

Science.gov (United States)

Duke, Daniel; Kastengren, Alan; Powell, Chris; X-Ray Fuel Spray Group, Energy Systems Division Team

2012-11-01

Cavitation plays an important role in the formation of sprays from small nozzles such as those found in fuel injection systems. A sharp-edged inlet from the sac into the nozzle of a diesel fuel injector is shown to inititate a strong sheet-like cavitation along the boundary layer of the nozzle throat, which is difficult to measure and can lead to acoustic damage. To investigate this phenomenon, a diagnostic technique capable of mapping the density field of the nozzle through regions of intense cavitation is required. Available visible-light techniques are limited to qualitative observations of the outer extent of cavitation zones. However, brilliant X-rays from a synchrotron source have negligible refraction and are capable of penetrating the full extent of cavitation zones. We present the early results of a novel application of line-of-sight, time-resolved X-ray radiography on a cavitating model nozzle. Experiments were conducted at Sector 7-BM of the Advanced Photon Source. Density and vapor distribution are measured from the quantitative absorption of monochromatic X-rays. The density field can then be tomographically reconstructed from the projections. The density is then validated against a range of compressible and incompressible numerical simulations. This research was performed at the 7-BM beamline of the Advanced Photon Source. We acknowledge the support of the U.S. Department of Energy under Contract No. DE-AC02-06CH11357 and the DOE Vehicle Technologies Program (DOE-EERE).

Drag Reducing and Cavitation Resistant Coatings

Energy Technology Data Exchange (ETDEWEB)

Pease, Leonard F.

2016-12-28

Client, Green Building Systems (GBS), presented PNNL a coating reported to reduce drag and prevent cavitation damage on marine vessels, turbines and pumps. The composition of the coating remains proprietary but has as constituents including silicon oxides, aliphatic carbon chains, and fluorine rich particles. The coating is spray applied to surfaces. Prior GBS testing and experiments suggest reduction of both drag and cavitation on industrial scale propellers, but the underlying mechanism for these effects remains unclear. Yet, the application is compelling because even modest reductions in drag to marine vessels and cavitation to propellers and turbines present a significant economic and environmental opportunity. To discern among possible mechanisms, PNNL considered possible mechanisms with the client, executed multiple experiments, and completed one theoretical analysis (see appendix). The remainder of this report first considers image analysis to gain insight into drag reduction mechanisms and then exposes the coating to cavitation to explore its response to an intensely cavitating environment. Although further efforts may be warranted to confirm mechanisms, this report presents a first investigation into these coatings within the scope and resources of the technology assistance program (TAP).

Laser-induced cavitation based micropump

NARCIS (Netherlands)

Dijkink, R.J.; Ohl, C.D.

2008-01-01

Lab-on-a-chip devices are in strong demand as versatile and robust pumping techniques. Here, we present a cavitation based technique, which is able to pump a volume of 4000 m3 within 75 s against an estimated pressure head of 3 bar. The single cavitation event is created by focusing a laser pulse in

Characterization of Axial Inducer Cavitation Instabilities via High Speed Video Recordings

Science.gov (United States)

Arellano, Patrick; Peneda, Marinelle; Ferguson, Thomas; Zoladz, Thomas

2011-01-01

Sub-scale water tests were undertaken to assess the viability of utilizing high resolution, high frame-rate digital video recordings of a liquid rocket engine turbopump axial inducer to characterize cavitation instabilities. These high speed video (HSV) images of various cavitation phenomena, including higher order cavitation, rotating cavitation, alternating blade cavitation, and asymmetric cavitation, as well as non-cavitating flows for comparison, were recorded from various orientations through an acrylic tunnel using one and two cameras at digital recording rates ranging from 6,000 to 15,700 frames per second. The physical characteristics of these cavitation forms, including the mechanisms that define the cavitation frequency, were identified. Additionally, these images showed how the cavitation forms changed and transitioned from one type (tip vortex) to another (sheet cavitation) as the inducer boundary conditions (inlet pressures) were changed. Image processing techniques were developed which tracked the formation and collapse of cavitating fluid in a specified target area, both in the temporal and frequency domains, in order to characterize the cavitation instability frequency. The accuracy of the analysis techniques was found to be very dependent on target size for higher order cavitation, but much less so for the other phenomena. Tunnel-mounted piezoelectric, dynamic pressure transducers were present throughout these tests and were used as references in correlating the results obtained by image processing. Results showed good agreement between image processing and dynamic pressure spectral data. The test set-up, test program, and test results including H-Q and suction performance, dynamic environment and cavitation characterization, and image processing techniques and results will be discussed.

Comparison of Different Mathematical Models of Cavitation

Directory of Open Access Journals (Sweden)

Dorota HOMA

2014-12-01

Full Text Available Cavitation occurs during the flow when local pressure drops to the saturation pressure according to the temperature of the flow. It includes both evaporation and condensation of the vapor bubbles, which occur alternately with high frequency. Cavitation can be very dangerous, especially for pumps, because it leads to break of flow continuity, noise, vibration, erosion of blades and change in pump’s characteristics. Therefore it is very important for pump designers and users to avoid working in cavitation conditions. Simulation of flow can be very useful in that and can indicate if there is risk of cavitating flow occurrence. As this is a multiphase flow and quite complicated phenomena, there are a few mathematical models describing it. The aim of this paper is to make a short review of them and describe their approach to model cavitation. It is desirable to know differences between them to model this phenomenon properly.

Kaplan turbine tip vortex cavitation – analysis and prevention

International Nuclear Information System (INIS)

Motycak, L; Skotak, A; Kupcik, R

2012-01-01

The work is focused on one type of Kaplan turbine runner cavitation – a tip vortex cavitation. For detailed description of the tip vortex, the CFD analysis is used. On the basis of this analysis it is possible to estimate the intensity of cavitating vortex core, danger of possible blade surface and runner chamber cavitation pitting. In the paper, the ways how to avoid the pitting effect of the tip vortex are described. In order to prevent the blade surface against pitting, the following possibilities as the change of geometry of the runner blade, dimension of tip clearance and finally the installation of the anti-cavitation lips are discussed. The knowledge of the shape and intensity of the tip vortex helps to design the anti-cavitation lips more sophistically. After all, the results of the model tests of the Kaplan runner with or without anti-cavitation lips and the results of the CFD analysis are compared.

Effects of cavitation on performance of automotive torque converter

Directory of Open Access Journals (Sweden)

Jaewon Ju

2016-06-01

Full Text Available Cavitation is a phenomenon whereby vapor bubbles of a flowing liquid are formed in a local region where the pressure of the liquid is below its vapor pressure. It is well known that cavitation in torque converters occurs frequently when a car with an automatic transmission makes an abrupt start. Cavitation is closely related to a performance drop and noise generation at a specific operating condition in a car and a torque converter itself. This study addressed the relation between cavitation and performance in an automotive torque converter in a quantitative and qualitative manner using numerical simulations. The cavitation was calculated at various operating conditions using a commercial flow solver with the homogeneous cavitation model, and the torque converter performance was compared with the experimental data. Numerical results well match to the data and indicate that the cavitation causes significant performance drop, as the pump speed increases or both speed ratio and reference pressure decrease.

Contributions to some cavitation problems in turbomachinery

OpenAIRE

Arakeri, VH

1999-01-01

In the present article, three problems associated with cavitation in turbomachinery are discussed. The first one deals with the potential application of recent understanding in cavitation inception to similar problems in turbomachinery. The second considers the thermodynamic effects in developed cavitation. This has relevance to turbopump operation using fluids other than water. Old correlations to predict the above effect are summarized and a new correlation is proposed. Lastly, the possible...

Modeling of hydrodynamic cavitation reactors: a unified approach

NARCIS (Netherlands)

Moholkar, V.S.; Pandit, A.B.

2001-01-01

An attempt has been made to present a unified theoretical model for the cavitating flow in a hydrodynamic cavitation reactor using the nonlinear continuum mixture model for two-phase flow as the basis. This model has been used to describe the radial motion of bubble in the cavitating flow in two

International symposium on cavitation and multiphase flow noise - 1986

International Nuclear Information System (INIS)

Arndt, R.E.A.; Billet, M.L.; Blake, W.K.

1986-01-01

This book presents the papers given at a symposium on multiphase flow and cavitation. Topics considered at the conference included the development of a cavitation-free sodium pump for a breeder reactor, the stochastic behavior (randomness) of acoustic pressure pulses in the near-subcavitating range, cavitation monitoring of two axial-flow hydroturbines, and noise generated by cavitation in orifice plates with some gaseous effects

Pressurized air injection in an axial hydro-turbine model for the mitigation of tip leakage cavitation

Science.gov (United States)

Rivetti, A.; Angulo, M.; Lucino, C.; Liscia, S.

2015-12-01

Tip leakage vortex cavitation in axial hydro-turbines may cause erosion, noise and vibration. Damage due to cavitation can be found at the tip of the runner blades on the low pressure side and the discharge ring. In some cases, the erosion follows an oscillatory pattern that is related to the number of guide vanes. That might suggest that a relationship exists between the flow through the guide vanes and the tip vortex cavitating core that induces this kind of erosion. On the other hand, it is known that air injection has a beneficial effect on reducing the damage by cavitation. In this paper, a methodology to identify the interaction between guide vanes and tip vortex cavitation is presented and the effect of air injection in reducing this particular kind of erosion was studied over a range of operating conditions on a Kaplan scale model. It was found that air injection, at the expense of slightly reducing the efficiency of the turbine, mitigates the erosive potential of tip leakage cavitation, attenuates the interaction between the flow through the guide vanes and the tip vortex and decreases the level of vibration of the structural components.

Experimental investigation of cavitation induced air release

Science.gov (United States)

Kowalski, Karoline; Pollak, Stefan; Hussong, Jeanette

Variations in cross-sectional areas may lead to pressure drops below a critical value, such that cavitation and air release are provoked in hydraulic systems. Due to a relatively slow dissolution of gas bubbles, the performance of hydraulic systems will be affected on long time scales by the gas phase. Therefore predictions of air production rates are desirable to describe the system characteristics. Existing investigations on generic geometries such as micro-orifice flows show an outgassing process due to hydrodynamic cavitation which takes place on time scales far shorter than diffusion processes. The aim of the present investigation is to find a correlation between global, hydrodynamic flow characteristics and cavitation induced undissolved gas fractions generated behind generic flow constrictions such as an orifice or venturi tube. Experimental investigations are realised in a cavitation channel that enables an independent adjustment of the pressure level upstream and downstream of the orifice. Released air fractions are determined by means of shadowgraphy imaging. First results indicate that an increased cavitation activity leads to a rapid increase in undissolved gas volume only in the choking regime. The frequency distribution of generated gas bubble size seems to depend only indirectly on the cavitation intensity driven by an increase of downstream coalescence events due to a more densely populated bubbly flow.

Controlling cavitation-based image contrast in focused ultrasound histotripsy surgery.

Science.gov (United States)

Allen, Steven P; Hall, Timothy L; Cain, Charles A; Hernandez-Garcia, Luis

2015-01-01

To develop MRI feedback for cavitation-based, focused ultrasound, tissue erosion surgery (histotripsy), we investigate image contrast generated by transient cavitation events. Changes in GRE image intensity are observed while balanced pairs of field gradients are varied in the presence of an acoustically driven cavitation event. The amplitude of the acoustic pulse and the timing between a cavitation event and the start of these gradient waveforms are also varied. The magnitudes and phases of the cavitation site are compared with those of control images. An echo-planar sequence is used to evaluate histotripsy lesions in ex vivo tissue. Cavitation events in water cause localized attenuation when acoustic pulses exceed a pressure threshold. Attenuation increases with increasing gradient amplitude and gradient lobe separation times and is isotropic with gradient direction. This attenuation also depends upon the relative timing between the cavitation event and the start of the balanced gradients. These factors can be used to control the appearance of attenuation while imaging ex vivo tissue. By controlling the timing between cavitation events and the imaging gradients, MR images can be made alternately sensitive or insensitive to cavitation. During therapy, these images can be used to isolate contrast generated by cavitation. © 2014 Wiley Periodicals, Inc.

Cavitation propagation in water under tension

Science.gov (United States)

Noblin, Xavier; Yip Cheung Sang, Yann; Pellegrin, Mathieu; Materials and Complex Fluids Team

2012-11-01

Cavitation appears when pressure decreases below vapor pressure, generating vapor bubbles. It can be obtain in dynamical ways (acoustic, hydraulic) but also in quasi-static conditions. This later case is often observed in nature, in trees, or during the ejection of ferns spores. We study the cavitation bubbles nucleation dynamics and its propagation in a confined microfabricated media. This later is an ordered array of microcavities made in hydrogel filled with water. When the system is put into dry air, it dehydrates, water leaves the cavities and tension (negative pressure) builds in the cavities. This can be sustained up to a critical pressure (of order -20 MPa), then cavitation bubbles appear. We follow the dynamics using ultra high speed imaging. Events with several bubbles cavitating in a few microseconds could be observed along neighboring cells, showing a propagation phenomenon that we discuss. ANR CAVISOFT 2010-JCJC-0407 01.

Control of acoustic cavitation with application to lithotripsy

Science.gov (United States)

Bailey, Michael Rollins

Control of acoustic cavitation, which is sound-induced growth and collapse of bubbles, is the subject of this dissertation. Application is to extracorporeal shock wave lithotripsy (ESWL), used to treat kidney stones. Cavitation is thought to help comminute stones yet may damage tissue. Can cavitation be controlled? The acoustic source in a widely used clinical lithotripter is an electrical spark at the near focus of an underwater ellipsoidal reflector. To control cavitation, we used rigid reflectors, pressure release reflectors, and pairs of reflectors aligned to have a common focus and a controlled delay between sparks. Cavitation was measured with aluminum foil, which was placed along the axis at the far focus of the reflector(s). Collapsing bubbles pitted the foil. Pit depth measured with a profilometer provided a relative measure of cavitation intensity. Cavitation was also measured with a focused hydrophone, which detected the pressure pulse radiated in bubble collapse. Acoustic pressure signals produced by the reflectors were measured with a PVdF membrane hydrophone, digitally recorded, and input into a numerical version of the Gilmore equation (F. R. Gilmore, 'The growth or collapse of a spherical bubble in a viscous compressible liquid,' Rep#26-4, California Institute of Technology, Pasadena (1952), pp.1-40.). Maximum pressure produced in a spherical bubble was calculated and employed as a relative measure of collapse intensity. Experimental and numerical results demonstrate cavitation can be controlled by an appropriately delayed auxiliary pressure pulse. When two rigid-reflector pulses are used, a long interpulse delay (150-200 μs) of the second pulse 'kicks' the collapsing bubble and intensifies cavitation. Foil pit depth and computed pressure three times single pulse values were obtained. Conversely, a short delay (ESWL.

RANS computations of tip vortex cavitation

Science.gov (United States)

Decaix, Jean; Balarac, Guillaume; Dreyer, Matthieu; Farhat, Mohamed; Münch, Cécile

2015-12-01

The present study is related to the development of the tip vortex cavitation in Kaplan turbines. The investigation is carried out on a simplified test case consisting of a NACA0009 blade with a gap between the blade tip and the side wall. Computations with and without cavitation are performed using a R ANS modelling and a transport equation for the liquid volume fraction. Compared with experimental data, the R ANS computations turn out to be able to capture accurately the development of the tip vortex. The simulations have also highlighted the influence of cavitation on the tip vortex trajectory.

Promotion of Cultural Heritage in Batangas and Cavite

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Dr. Dexter R. Buted

2014-06-01

Full Text Available – The study aimed to identify the commonly visited cultural heritage sites in Batangas and Cavite; to assess the cultural heritage sites in Batangas and Cavite in terms of physical, social and economic aspects; and to determine existing promotional patterns of Batangas and Cavite. Descriptive type of research was utilized in the study. Results showed that the most visited cultural heritage attraction in Taal, Batangas was Basilica of St. Martin de Tours while in Maragondon, Cavite the most visited was Andres Bonifacio Trial House . Blogs, Websites and Facebook are mostly used by the municipality of Taal in promoting their cultural heritage sites. While Cavite sticks to always using leaflets/flyers, brochures as their promotional materials. Cultural heritage sites in both Taal and Maragondon were perceived to have positive results in the assessments based on different aspects such as physical, social and economic aspects. The promotional materials of Taal and Maragondon are often used. A proposed plan of action was made to promote cultural attraction in Maragondon, Cavite and Taal, Batangas.

Assessment of a turbulence model for numerical predictions of sheet-cavitating flows in centrifugal pumps

Energy Technology Data Exchange (ETDEWEB)

Liu, Houlin; Wang, Yong; Liu, Dongxi; Yuan, Shouqi; Wang, Jian [Jiangsu University, Zhenjiang (China)

2013-09-15

Various approaches have been developed for numerical predictions of unsteady cavitating turbulent flows. To verify the influence of a turbulence model on the simulation of unsteady attached sheet-cavitating flows in centrifugal pumps, two modified RNG k-ε models (DCM and FBM) are implemented in ANSYS-CFX 13.0 by second development technology, so as to compare three widespread turbulence models in the same platform. The simulation has been executed and compared to experimental results for three different flow coefficients. For four operating conditions, qualitative comparisons are carried out between experimental and numerical cavitation patterns, which are visualized by a high-speed camera and depicted as isosurfaces of vapor volume fraction α{sub v} = 0.1, respectively. The comparison results indicate that, for the development of the sheet attached cavities on the suction side of the impeller blades, the numerical results with different turbulence models are very close to each other and overestimate the experiment ones slightly. However, compared to the cavitation performance experimental curves, the numerical results have obvious difference: the prediction precision with the FBM is higher than the other two turbulence models. In addition, the loading distributions around the blade section at midspan are analyzed in detail. The research results suggest that, for numerical prediction of cavitating flows in centrifugal pumps, the turbulence model has little influence on the development of cavitation bubbles, but the advanced turbulence model can significantly improve the prediction precision of head coefficients and critical cavitation numbers.

The Impact of Manifold-to-Orifice Turning Angle on Sharp-Edge Orifice Flow Characteristics in both Cavitation and Non-Cavitation Turbulent Flow Regimes (Preprint)

Science.gov (United States)

2007-06-01

varies as the cavitation number is lowered. The third is supercavitation where the vapor pocket attachment has moved to the orifice exit and beyond but...the flow still acts as attached. For this study only the 90 degree orifice angle configuration experienced supercavitation . For all other angles

RANS simulation of cavitation and hull pressure fluctuation for marine propeller operating behind-hull condition

Science.gov (United States)

Paik, Kwang-Jun; Park, Hyung-Gil; Seo, Jongsoo

2013-12-01

Simulations of cavitation flow and hull pressure fluctuation for a marine propeller operating behind a hull using the unsteady Reynolds-Averaged Navier-Stokes equations (RANS) are presented. A full hull body submerged under the free surface is modeled in the computational domain to simulate directly the wake field of the ship at the propeller plane. Simulations are performed in design and ballast draught conditions to study the effect of cavitation number. And two propellers with slightly different geometry are simulated to validate the detectability of the numerical simulation. All simulations are performed using a commercial CFD software FLUENT. Cavitation patterns of the simulations show good agreement with the experimental results carried out in Samsung CAvitation Tunnel (SCAT). The simulation results for the hull pressure fluctuation induced by a propeller are also compared with the experimental results showing good agreement in the tendency and amplitude, especially, for the first blade frequency.

Counterbalancing the use of ultrasound contrast agents by a cavitation-regulated system.

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Desjouy, C; Fouqueray, M; Lo, C W; Muleki Seya, P; Lee, J L; Bera, J C; Chen, W S; Inserra, C

2015-09-01

The stochastic behavior of cavitation can lead to major problems of initiation and maintenance of cavitation during sonication, responsible of poor reproducibility of US-induced bioeffects in the context of sonoporation for instance. To overcome these disadvantages, the injection of ultrasound contrast agents as cavitation nuclei ensures fast initiation and lower acoustic intensities required for cavitation activity. More recently, regulated-cavitation devices based on the real-time modulation of the applied acoustic intensity have shown their potential to maintain a stable cavitation state during an ultrasonic shot, in continuous or pulsed wave conditions. In this paper is investigated the interest, in terms of cavitation activity, of using such regulated-cavitation device or injecting ultrasound contrast agents in the sonicated medium. When using fixed applied acoustic intensity, results showed that introducing ultrasound contrast agents increases reproducibility of cavitation activity (coefficient of variation 62% and 22% without and with UCA, respectively). Moreover, the use of the regulated-cavitation device ensures a given cavitation activity (coefficient of variation less 0.4% in presence of UCAs or not). This highlights the interest of controlling cavitation over time to free cavitation-based application from the use of UCAs. Interestingly, during a one minute sonication, while ultrasound contrast agents progressively disappear, the regulated-cavitation device counterbalance their destruction to sustain a stable inertial cavitation activity. Copyright © 2015 Elsevier B.V. All rights reserved.

Cavitation for improved sludge conversion into biogas

Science.gov (United States)

Stoop, A. H.; Bakker, T. W.; Kramer, H. J. M.

2015-12-01

In several studies the beneficial influence of pre-treatment of waste activated sludge with cavitation on the biogas production was demonstrated. It is however, still not fully certain whether this effect should be mainly contributed to an increase in conversion rate of organics into biogas by anaerobic bacteria, and how much cavitation increases the total biogas yield. An increase in yield is only the case if cavitation can further disrupt otherwise inaccessible cell membrane structures and long chain organic molecules. In this study the influence of hydrodynamic cavitation on sludge that was already digested for 30 days was investigated. The total biogas yield could indeed be increased. The effect of the backpressure behind the venturi tube on the yield could not yet be established.

Cavitation studies in microgravity

Science.gov (United States)

Kobel, Philippe; Obreschkow, Danail; Farhat, Mohamed; Dorsaz, Nicolas; de Bosset, Aurele

The hydrodynamic cavitation phenomenon is a major source of erosion for many industrial systems such as cryogenic pumps for rocket propulsion, fast ship propellers, hydraulic pipelines and turbines. Erosive processes are associated with liquid jets and shockwaves emission fol-lowing the cavity collapse. Yet, fundamental understanding of these processes requires further cavitation studies inside various geometries of liquid volumes, as the bubble dynamics strongly depends the surrounding pressure field. To this end, microgravity represents a unique platform to produce spherical fluid geometries and remove the hydrostatic pressure gradient induced by gravity. The goal of our first experiment (flown on ESA's parabolic flight campaigns 2005 and 2006) was to study single bubble dynamics inside large spherical water drops (having a radius between 8 and 13 mm) produced in microgravity. The water drops were created by a micro-pump that smoothly expelled the liquid through a custom-designed injector tube. Then, the cavitation bubble was generated through a fast electrical discharge between two electrodes immersed in the liquid from above. High-speed imaging allowed to analyze the implications of isolated finite volumes and spherical free surfaces on bubble evolution, liquid jets formation and shock wave dynamics. Of particular interest are the following results: (A) Bubble lifetimes are shorter than in extended liquid volumes, which could be explain by deriving novel corrective terms to the Rayleigh-Plesset equation. (B) Transient crowds of micro-bubbles (smaller than 1mm) appeared at the instants of shockwaves emission. A comparison between high-speed visualizations and 3D N-particle simulations of a shock front inside a liquid sphere reveals that focus zones within the drop lead to a significantly increased density of induced cavitation. Considering shock wave crossing and focusing may hence prove crucially useful to understand the important process of cavitation erosion

Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems

OpenAIRE

Ferrari, A.

2017-01-01

Cavitation is the transition from a liquid to a vapour phase, due to a drop in pressure to the level of the vapour tension of the fluid. Two kinds of cavitation have been reviewed here: acoustic cavitation and hydrodynamic cavitation. As acoustic cavitation in engineering systems is related to the propagation of waves through a region subjected to liquid vaporization, the available expressions of the sound speed are discussed. One of the main effects of hydrodynamic cavitation in the nozzles ...

Inertial cavitation threshold of nested microbubbles.

Science.gov (United States)

Wallace, N; Dicker, S; Lewin, Peter; Wrenn, S P

2015-04-01

Cavitation of ultrasound contrast agents (UCAs) promotes both beneficial and detrimental bioeffects in vivo (Radhakrishnan et al., 2013) [1]. The ability to determine the inertial cavitation threshold of UCA microbubbles has potential application in contrast imaging, development of therapeutic agents, and evaluation of localized effects on the body (Ammi et al., 2006) [2]. This study evaluates a novel UCA and its inertial cavitation behavior as determined by a home built cavitation detection system. Two 2.25 MHz transducers are placed at a 90° angle to one another where one transducer is driven by a high voltage pulser and the other transducer receives the signal from the oscillating microbubble. The sample chamber is placed in the overlap of the focal region of the two transducers where the microbubbles are exposed to a pulser signal consisting of 600 pulse trains per experiment at a pulse repetition frequency of 5 Hz where each train has four pulses of four cycles. The formulation being analyzed is comprised of an SF6 microbubble coated by a DSPC PEG-3000 monolayer nested within a poly-lactic acid (PLA) spherical shell. The effect of varying shell diameters and microbubble concentration on cavitation threshold profile for peak negative pressures ranging from 50 kPa to 2 MPa are presented and discussed in this paper. The nesting shell decreases inertial cavitation events from 97.96% for an un-nested microbubble to 19.09% for the same microbubbles nested within a 2.53 μm shell. As shell diameter decreases, the percentage of inertially cavitating microbubbles also decreases. For nesting formulations with average outer capsule diameters of 20.52, 14.95, 9.95, 5.55, 2.53, and 1.95 μm, the percentage of sample destroyed at 1 MPa was 51.02, 38.94, 33.25, 25.27, 19.09, and 5.37% respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

Prevention of Pressure Oscillations in Modeling a Cavitating Acoustic Fluid

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B. Klenow

2010-01-01

Full Text Available Cavitation effects play an important role in the UNDEX loading of a structure. For far-field UNDEX, the structural loading is affected by the formation of local and bulk cavitation regions, and the pressure pulses resulting from the closure of the cavitation regions. A common approach to numerically modeling cavitation in far-field underwater explosions is Cavitating Acoustic Finite Elements (CAFE and more recently Cavitating Acoustic Spectral Elements (CASE. Treatment of cavitation in this manner causes spurious pressure oscillations which must be treated by a numerical damping scheme. The focus of this paper is to investigate the severity of these oscillations on the structural response and a possible improvement to CAFE, based on the original Boris and Book Flux-Corrected Transport algorithm on structured meshes [6], to limit oscillations without the energy loss associated with the current damping schemes.

Diagnosing non-cavitated lesions in epidemiological studies: practical and scientific considerations.

Science.gov (United States)

Carvalho, Joana Christina; Mestrinho, Heliana Dantas

2014-01-01

Over the last decade, there has been growing interest in diagnosing non-cavitated lesions in epidemiological studies involving large numbers of preschool children, schoolchildren and young adults. In this context, assessment of lesions characteristics indicating whether or not there is ongoing mineral loss is also considered relevant. The reasoning sustained by these studies is that diagnosis of the caries process limited to the cavitated level is no longer in accordance with current state-of-the-art knowledge in cariology. This paper highlights one topic of the lecture entitled "Caries Process: Evolving Evidence and Understanding," presented at the 18th Congress of the Brazilian Association for Oral Health Promotion (Associação Brasileira de Odontologia de Promoção de Saúde - ABOPREV) in April 2013. In the framework of epidemiological studies, the interest in diagnosing active and inactive non-cavitated lesions was elucidated. However, relevant questions associated with the diagnosis of non-cavitated lesions that might raise concerns among researchers and health administrators were not addressed. The present paper aims to bring these questions into discussion. The contribution of this discussion in terms of developing the understanding of caries decline is analyzed by using data from a caries trends study of Brazilian preschool children residing in the Federal District of Brazil as an example. The inclusion of active and inactive non-cavitated lesions in the diagnosis of the caries process allowed us to demonstrate that, in Brazilian 1- to 5-year-old children, caries prevalence decreased significantly from 1996 to 2006, simultaneously with a reduction in the rate of caries progression.

Application of Hydrodynamic Cavitation for Food and Bioprocessing

Science.gov (United States)

Gogate, Parag R.

Hydrodynamic cavitation can be simply generated by the alterations in the flow field in high speed/high pressure devices and also by passage of the liquid through a constriction such as orifice plate, venturi, or throttling valve. Hydrodynamic cavitation results in the formation of local hot spots, release of highly reactive free radicals, and enhanced mass transfer rates due to turbulence generated as a result of liquid circulation currents. These conditions can be suitably applied for intensification of different bioprocessing applications in an energy-efficient manner as compared to conventionally used ultrasound-based reactors. The current chapter aims at highlighting different aspects related to hydrodynamic cavitation, including the theoretical aspects for optimization of operating parameters, reactor designs, and overview of applications relevant to food and bioprocessing. Some case studies highlighting the comparison of hydrodynamic cavitation and acoustic cavitation reactors will also be discussed.

Experimental investigation of cavitation induced air release

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Kowalski Karoline

2017-01-01

Full Text Available Variations in cross-sectional areas may lead to pressure drops below a critical value, such that cavitation and air release are provoked in hydraulic systems. Due to a relatively slow dissolution of gas bubbles, the performance of hydraulic systems will be affected on long time scales by the gas phase. Therefore predictions of air production rates are desirable to describe the system characteristics. Existing investigations on generic geometries such as micro-orifice flows show an outgassing process due to hydrodynamic cavitation which takes place on time scales far shorter than diffusion processes. The aim of the present investigation is to find a correlation between global, hydrodynamic flow characteristics and cavitation induced undissolved gas fractions generated behind generic flow constrictions such as an orifice or venturi tube. Experimental investigations are realised in a cavitation channel that enables an independent adjustment of the pressure level upstream and downstream of the orifice. Released air fractions are determined by means of shadowgraphy imaging. First results indicate that an increased cavitation activity leads to a rapid increase in undissolved gas volume only in the choking regime. The frequency distribution of generated gas bubble size seems to depend only indirectly on the cavitation intensity driven by an increase of downstream coalescence events due to a more densely populated bubbly flow.

Hydrodynamic cavitation kills prostate cells and ablates benign prostatic hyperplasia tissue.

Science.gov (United States)

Itah, Zeynep; Oral, Ozlem; Perk, Osman Yavuz; Sesen, Muhsincan; Demir, Ebru; Erbil, Secil; Dogan-Ekici, A Isin; Ekici, Sinan; Kosar, Ali; Gozuacik, Devrim

2013-11-01

Hydrodynamic cavitation is a physical phenomenon characterized by vaporization and bubble formation in liquids under low local pressures, and their implosion following their release to a higher pressure environment. Collapse of the bubbles releases high energy and may cause damage to exposed surfaces. We recently designed a set-up to exploit the destructive nature of hydrodynamic cavitation for biomedical purposes. We have previously shown that hydrodynamic cavitation could kill leukemia cells and erode kidney stones. In this study, we analyzed the effects of cavitation on prostate cells and benign prostatic hyperplasia (BPH) tissue. We showed that hydrodynamic cavitation could kill prostate cells in a pressure- and time-dependent manner. Cavitation did not lead to programmed cell death, i.e. classical apoptosis or autophagy activation. Following the application of cavitation, we observed no prominent DNA damage and cells did not arrest in the cell cycle. Hence, we concluded that cavitation forces directly damaged the cells, leading to their pulverization. Upon application to BPH tissues from patients, cavitation could lead to a significant level of tissue destruction. Therefore similar to ultrasonic cavitation, we propose that hydrodynamic cavitation has the potential to be exploited and developed as an approach for the ablation of aberrant pathological tissues, including BPH.

Use of hydrodynamic cavitation in (waste)water treatment.

Science.gov (United States)

Dular, Matevž; Griessler-Bulc, Tjaša; Gutierrez-Aguirre, Ion; Heath, Ester; Kosjek, Tina; Krivograd Klemenčič, Aleksandra; Oder, Martina; Petkovšek, Martin; Rački, Nejc; Ravnikar, Maja; Šarc, Andrej; Širok, Brane; Zupanc, Mojca; Žitnik, Miha; Kompare, Boris

2016-03-01

The use of acoustic cavitation for water and wastewater treatment (cleaning) is a well known procedure. Yet, the use of hydrodynamic cavitation as a sole technique or in combination with other techniques such as ultrasound has only recently been suggested and employed. In the first part of this paper a general overview of techniques that employ hydrodynamic cavitation for cleaning of water and wastewater is presented. In the second part of the paper the focus is on our own most recent work using hydrodynamic cavitation for removal of pharmaceuticals (clofibric acid, ibuprofen, ketoprofen, naproxen, diclofenac, carbamazepine), toxic cyanobacteria (Microcystis aeruginosa), green microalgae (Chlorella vulgaris), bacteria (Legionella pneumophila) and viruses (Rotavirus) from water and wastewater. As will be shown, hydrodynamic cavitation, like acoustic, can manifest itself in many different forms each having its own distinctive properties and mechanisms. This was until now neglected, which eventually led to poor performance of the technique. We will show that a different type of hydrodynamic cavitation (different removal mechanism) is required for successful removal of different pollutants. The path to use hydrodynamic cavitation as a routine water cleaning method is still long, but recent results have already shown great potential for optimisation, which could lead to a low energy tool for water and wastewater cleaning. Copyright © 2015 Elsevier B.V. All rights reserved.

Suppression of Fatigue Crack Propagation of Duralumin by Cavitation Peening

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Hitoshi Soyama

2015-08-01

Full Text Available It was demonstrated in the present paper that cavitation peening which is one of the mechanical surface modification technique can suppress fatigue crack propagation in duralumin. The impacts produced when cavitation bubble collapses can be utilised for the mechanical surface modification technique in the same way as laser peening and shot peening, which is called “cavitation peening”. Cavitation peening employing a cavitating jet in water was used to treat the specimen made of duralumin Japanese Industrial Standards JIS A2017-T3. After introducing a notch, fatigue test was conducted by a load-controlled plate bending fatigue tester, which has been originally developed. The fatigue crack propagation behavior was evaluated and the relationship between the fatigue crack propagation rate versus stress intensity factor range was obtained. From the results, the fatigue crack propagation rate was drastically reduced by cavitation peening and the fatigue life of duralumin plate was extended 4.2 times by cavitation peening. In addition, the fatigue crack propagation can be suppressed by 88% in the stable crack propagation stage by cavitation peening.

Robust Fault Diagnosis Design for Linear Multiagent Systems with Incipient Faults

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Jingping Xia

2015-01-01

Full Text Available The design of a robust fault estimation observer is studied for linear multiagent systems subject to incipient faults. By considering the fact that incipient faults are in low-frequency domain, the fault estimation of such faults is proposed for discrete-time multiagent systems based on finite-frequency technique. Moreover, using the decomposition design, an equivalent conclusion is given. Simulation results of a numerical example are presented to demonstrate the effectiveness of the proposed techniques.

Sound source location in cavitating tip vortices

International Nuclear Information System (INIS)

Higuchi, H.; Taghavi, R.; Arndt, R.E.A.

1985-01-01

Utilizing an array of three hydrophones, individual cavitation bursts in a tip vortex could be located. Theoretically, four hydrophones are necessary. Hence the data from three hydrophones are supplemented with photographic observation of the cavitating tip vortex. The cavitation sound sources are found to be localized to within one base chord length from the hydrofoil tip. This appears to correspond to the region of initial tip vortex roll-up. A more extensive study with a four sensor array is now in progress

Trans-Stent B-Mode Ultrasound and Passive Cavitation Imaging.

Science.gov (United States)

Haworth, Kevin J; Raymond, Jason L; Radhakrishnan, Kirthi; Moody, Melanie R; Huang, Shao-Ling; Peng, Tao; Shekhar, Himanshu; Klegerman, Melvin E; Kim, Hyunggun; McPherson, David D; Holland, Christy K

2016-02-01

Angioplasty and stenting of a stenosed artery enable acute restoration of blood flow. However, restenosis or a lack of re-endothelization can subsequently occur depending on the stent type. Cavitation-mediated drug delivery is a potential therapy for these conditions, but requires that particular types of cavitation be induced by ultrasound insonation. Because of the heterogeneity of tissue and stochastic nature of cavitation, feedback mechanisms are needed to determine whether the sustained bubble activity is induced. The objective of this study was to determine the feasibility of passive cavitation imaging through a metal stent in a flow phantom and an animal model. In this study, an endovascular stent was deployed in a flow phantom and in porcine femoral arteries. Fluorophore-labeled echogenic liposomes, a theragnostic ultrasound contrast agent, were injected proximal to the stent. Cavitation images were obtained by passively recording and beamforming the acoustic emissions from echogenic liposomes insonified with a low-frequency (500 kHz) transducer. In vitro experiments revealed that the signal-to-noise ratio for detecting stable cavitation activity through the stent was greater than 8 dB. The stent did not significantly reduce the signal-to-noise ratio. Trans-stent cavitation activity was also detected in vivo via passive cavitation imaging when echogenic liposomes were insonified by the 500-kHz transducer. When stable cavitation was detected, delivery of the fluorophore into the arterial wall was observed. Increased echogenicity within the stent was also observed when echogenic liposomes were administered. Thus, both B-mode ultrasound imaging and cavitation imaging are feasible in the presence of an endovascular stent in vivo. Demonstration of this capability supports future studies to monitor restenosis with contrast-enhanced ultrasound and pursue image-guided ultrasound-mediated drug delivery to inhibit restenosis. Copyright © 2016 World Federation for

Vortex cavitation and oscillation in a double-suction volute pump

International Nuclear Information System (INIS)

Sato, T; Nagahara, T; Tanaka, K; Fuchiwaki, M; Shimizu, F

2010-01-01

In recent years, Computational Fluid Dynamics (CFD) codes have been utilized actively in the early part of the product development cycle. Numerical analysis models have also been developed rapidly and have added cavitation flow analysis functions peculiar to hydraulic machines, in which the flow analysis has been developed remarkably with high-precision and high-reliability. On the other hand, it is well known that three kinds of cavitation, such as vortex cavitation, reverse flow cavitation and cloud cavitation appear in a double-suction volute pump. We have much interest in a relationship among the cavitating flows, pump oscillation and noise. In this study, full 3D numerical simulations have been performed using a commercial code inside the pump from the inlet of suction duct to the outlet of delivery duct. The numerical model is based on a combination of multiphase flow equations with the truncated version of the Rayleigh-Plesset model predicting the complicated growth and collapse process of cavity bubbles. This study highlights especially the mechanism of vortex cavitation occurrence from the end of the suction duct in the pump and pump oscillation which causes cavitation noise from the pump. The experimental investigations have also been performed on the cavitating flow with flow visualization to evaluate the numerical results.

Control of hydrodynamic cavitation using ultrasonic

Science.gov (United States)

Chatterjee, Dhiman; Arakeri, Vijay H.

2003-11-01

Hydrodynamic cavitation is known to have many harmful effects like surface damage and generation of noise. We investigated the use of ultrasonics to control traveling bubble cavitation. Ultrasonic pressure field, produced by a piezoelectric crystal, was applied to modify the nuclei size distribution. Effects of continuous-wave (CW) and pulsed excitations were studied. At low dissolved gas content the CW-mode performed better than the pulsed one, whereas for high gas content the pulsed one was more effective. The dominant mechanisms were Bjerknes force and rectified diffusion in these two cases. Simultaneous excitation by two crystals in CW and pulsed modes was seen to control cavitation better.

Cavitation erosion in a 400 deg. C sodium flow

International Nuclear Information System (INIS)

Courbiere, P.

2002-01-01

This paper presents the results of cavitation erosion tests conducted in the Cavitation Tunnel at the Cadarache Nuclear Research Center. The CANASTA system was used for acoustic monitoring of cavitation noise during the experiments. Comparative results are also presented for sodium and water tests. (author)

Highly effective degradation of selected groups of organic compounds by cavitation based AOPs under basic pH conditions.

Science.gov (United States)

Gągol, Michał; Przyjazny, Andrzej; Boczkaj, Grzegorz

2018-07-01

Cavitation has become on the most often applied methods in a number of industrial technologies. In the case of oxidation of organic pollutants occurring in the aqueous medium, cavitation forms the basis of numerous advanced oxidation processes (AOPs). This paper presents the results of investigations on the efficiency of oxidation of the following groups of organic compounds: organosulfur, nitro derivatives of benzene, BTEX, and phenol and its derivatives in a basic model effluent using hydrodynamic and acoustic cavitation combined with external oxidants, i.e., hydrogen peroxide, ozone and peroxone. The studies revealed that the combination of cavitation with additional oxidants allows 100% oxidation of the investigated model compounds. However, individual treatments differed with respect to the rate of degradation. Hydrodynamic cavitation aided by peroxone was found to be the most effective treatment (100% oxidation of all the investigated compounds in 60 min). When using hydrodynamic and acoustic cavitation alone, the effectiveness of oxidation was diversified. Under these conditions, nitro derivatives of benzene and phenol and its derivatives were found to be resistant to oxidation. In addition, hydrodynamic cavitation was found to be more effective in degradation of model compounds than acoustic cavitation. The results of investigations presented in this paper compare favorably with the investigations on degradation of organic contaminants using AOPs under conditions of basic pH published thus far. Copyright © 2018 Elsevier B.V. All rights reserved.

Physical and numerical investigation of the flow induced vibration of the hydrofoil

Science.gov (United States)

Wu, Q.; Wang, G. Y.; Huang, B.

2016-11-01

The objective of this paper is to investigate the flow induced vibration of a flexible hydrofoil in cavitating flows via combined experimental and numerical studies. The experiments are presented for the modified NACA66 hydrofoil made of POM Polyacetate in the closed-loop cavitation tunnel at Beijing Institute of Technology. The high-speed camera and the single point Laser Doppler Vibrometer are applied to analyze the transient flow structures and the corresponding structural vibration characteristics. The hybrid coupled fluid structure interaction model is conducted to couple the incompressible and unsteady Reynolds Averaged Navier-Stokes solver with a simplified two-degree-of-freedom structural model. The k-ω SST turbulence model with the turbulence viscosity correction and the Zwart cavitation model are introduced to the present simulations. The results showed that with the decreasing of the cavitation number, the cavitating flows display incipient cavitation, sheet cavitation, cloud cavitation and supercavitation. The vibration magnitude increases dramatically for the cloud cavitation and decline for the supercavitation. The cloud cavitation development strongly affects the vibration response, which is corresponding to the periodically developing and shedding of the large-scale cloud cavity. The main frequency of the vibration amplitude is accordance with the cavity shedding frequency and other two frequencies of the vibration amplitude are corresponding to the natural frequencies of the bending and twisting modes.

Analysis of cavitation behaviour in a centrifugal pump

International Nuclear Information System (INIS)

He, M; Zhou, L J; Guo, Q; Fu, L P; Wang, Z W

2012-01-01

Cavitation is a well-known problem in centrifugal pumps, causing serious damage and substantial head losses. However, the reason for the sudden head drop in cavitation curves is not fully understood. In this paper, the transient three-dimensional cavitating flow field in a centrifugal pump was calculated using RNG k-ε turbulence model and Rayleigh Plesset cavitation model. The NPSH-H curve and the cavitation development in the whole passage were predicted. The blade loading and energy transfer are analyzed for various cavitation conditions. The results show that the existing of the cavities changes the load distribution on blades. With the decrease of NPSH the loads on blades tend to increases in the rear part but decreases in the front part. If NPSH is not so low, sometimes the overall torque may increase slightly, thus the head may also increase slightly. But if the NPSH become low and reach a threshold value, the overall torque will also decrease. At the same time, the energy dissipation in the vortices increases greatly because of the growth of the cavities. These two reasons make the head drop rapidly.

Mitigation of tip vortex cavitation by means of air injection on a Kaplan turbine scale model

International Nuclear Information System (INIS)

Rivetti, A; Angulo, M; Lucino, C; Liscia, S

2014-01-01

Kaplan turbines operating at full-load conditions may undergo excessive vibration, noise and cavitation. In such cases, damage by erosion associated to tip vortex cavitation can be observed at the discharge ring. This phenomenon involves design features such as (1) overhang of guide vanes; (2) blade profile; (3) gap increasing size with blade opening; (4) suction head; (5) operation point; and (6) discharge ring stiffness, among others. Tip vortex cavitation may cause erosion at the discharge ring and draft tube inlet following a wavy pattern, in which the number of vanes can be clearly identified. Injection of pressurized air above the runner blade centerline was tested as a mean to mitigate discharge ring cavitation damage on a scale model. Air entrance was observed by means of a high-speed camera in order to track the air trajectory toward its mergence with the tip vortex cavitation core. Post-processing of acceleration signals shows that the level of vibration and the RSI frequency amplitude decrease proportionally with air flow rate injected. These findings reveal the potential mitigating effect of air injection in preventing cavitation damage and will be useful in further tests to be performed on prototype, aiming at determining the optimum air flow rate, size and distribution of the injectors

Mitigation of tip vortex cavitation by means of air injection on a Kaplan turbine scale model

Science.gov (United States)

Rivetti, A.; Angulo, M.; Lucino, C.; Liscia, S.

2014-03-01

Kaplan turbines operating at full-load conditions may undergo excessive vibration, noise and cavitation. In such cases, damage by erosion associated to tip vortex cavitation can be observed at the discharge ring. This phenomenon involves design features such as (1) overhang of guide vanes; (2) blade profile; (3) gap increasing size with blade opening; (4) suction head; (5) operation point; and (6) discharge ring stiffness, among others. Tip vortex cavitation may cause erosion at the discharge ring and draft tube inlet following a wavy pattern, in which the number of vanes can be clearly identified. Injection of pressurized air above the runner blade centerline was tested as a mean to mitigate discharge ring cavitation damage on a scale model. Air entrance was observed by means of a high-speed camera in order to track the air trajectory toward its mergence with the tip vortex cavitation core. Post-processing of acceleration signals shows that the level of vibration and the RSI frequency amplitude decrease proportionally with air flow rate injected. These findings reveal the potential mitigating effect of air injection in preventing cavitation damage and will be useful in further tests to be performed on prototype, aiming at determining the optimum air flow rate, size and distribution of the injectors.

Relationship between cavitation and loss of echogenicity from ultrasound contrast agents

International Nuclear Information System (INIS)

Radhakrishnan, Kirthi; Kopechek, Jonathan A; Raymond, Jason L; Bader, Kenneth B; Haworth, Kevin J; Holland, Christy K; Huang, Shao-Ling; McPherson, David D

2013-01-01

Ultrasound contrast agents (UCAs) have the potential to nucleate cavitation and promote both beneficial and deleterious bioeffects in vivo. Previous studies have elucidated the pulse-duration-dependent pressure amplitude threshold for rapid loss of echogenicity due to UCA fragmentation. Previous studies have demonstrated that UCA fragmentation was concomitant with inertial cavitation. The purpose of this study was to evaluate the relationship between stable and inertial cavitation thresholds and loss of echogenicity of UCAs as a function of pulse duration. Determining the relationship between cavitation thresholds and loss of echogenicity of UCAs would enable monitoring of cavitation based upon the onscreen echogenicity in clinical applications. Two lipid-shelled UCAs, echogenic liposomes (ELIP) and Definity®, were insonified by a clinical ultrasound scanner in duplex spectral Doppler mode at four pulse durations (‘sample volumes’) in both a static system and a flow system. Cavitation emissions from the UCAs insonified by Doppler pulses were recorded using a passive cavitation detection system and stable and inertial cavitation thresholds ascertained. Loss of echogenicity from ELIP and Definity® was assessed within regions of interest on B-mode images. A numerical model based on UCA rupture predicted the functional form of the loss of echogenicity from ELIP and Definity®. Stable and inertial cavitation thresholds were found to have a weak dependence on pulse duration. Stable cavitation thresholds were lower than inertial cavitation thresholds. The power of cavitation emissions was an exponential function of the loss of echogenicity over the investigated range of acoustic pressures. Both ELIP and Definity® lost more than 80% echogenicity before the onset of stable or inertial cavitation. Once this level of echogenicity loss occurred, both stable and inertial cavitation were detected in the physiologic flow phantom. These results imply that stable and

Relationship between cavitation and loss of echogenicity from ultrasound contrast agents.

Science.gov (United States)

Radhakrishnan, Kirthi; Bader, Kenneth B; Haworth, Kevin J; Kopechek, Jonathan A; Raymond, Jason L; Huang, Shao-Ling; McPherson, David D; Holland, Christy K

2013-09-21

Ultrasound contrast agents (UCAs) have the potential to nucleate cavitation and promote both beneficial and deleterious bioeffects in vivo. Previous studies have elucidated the pulse-duration-dependent pressure amplitude threshold for rapid loss of echogenicity due to UCA fragmentation. Previous studies have demonstrated that UCA fragmentation was concomitant with inertial cavitation. The purpose of this study was to evaluate the relationship between stable and inertial cavitation thresholds and loss of echogenicity of UCAs as a function of pulse duration. Determining the relationship between cavitation thresholds and loss of echogenicity of UCAs would enable monitoring of cavitation based upon the onscreen echogenicity in clinical applications. Two lipid-shelled UCAs, echogenic liposomes (ELIP) and Definity®, were insonified by a clinical ultrasound scanner in duplex spectral Doppler mode at four pulse durations ('sample volumes') in both a static system and a flow system. Cavitation emissions from the UCAs insonified by Doppler pulses were recorded using a passive cavitation detection system and stable and inertial cavitation thresholds ascertained. Loss of echogenicity from ELIP and Definity® was assessed within regions of interest on B-mode images. A numerical model based on UCA rupture predicted the functional form of the loss of echogenicity from ELIP and Definity®. Stable and inertial cavitation thresholds were found to have a weak dependence on pulse duration. Stable cavitation thresholds were lower than inertial cavitation thresholds. The power of cavitation emissions was an exponential function of the loss of echogenicity over the investigated range of acoustic pressures. Both ELIP and Definity® lost more than 80% echogenicity before the onset of stable or inertial cavitation. Once this level of echogenicity loss occurred, both stable and inertial cavitation were detected in the physiologic flow phantom. These results imply that stable and inertial

Relationship between cavitation and loss of echogenicity from ultrasound contrast agents

Science.gov (United States)

Radhakrishnan, Kirthi; Bader, Kenneth B.; Haworth, Kevin J.; Kopechek, Jonathan A.; Raymond, Jason L.; Huang, Shao-Ling; McPherson, David D.; Holland, Christy K.

2013-09-01

Ultrasound contrast agents (UCAs) have the potential to nucleate cavitation and promote both beneficial and deleterious bioeffects in vivo. Previous studies have elucidated the pulse-duration-dependent pressure amplitude threshold for rapid loss of echogenicity due to UCA fragmentation. Previous studies have demonstrated that UCA fragmentation was concomitant with inertial cavitation. The purpose of this study was to evaluate the relationship between stable and inertial cavitation thresholds and loss of echogenicity of UCAs as a function of pulse duration. Determining the relationship between cavitation thresholds and loss of echogenicity of UCAs would enable monitoring of cavitation based upon the onscreen echogenicity in clinical applications. Two lipid-shelled UCAs, echogenic liposomes (ELIP) and Definity®, were insonified by a clinical ultrasound scanner in duplex spectral Doppler mode at four pulse durations (‘sample volumes’) in both a static system and a flow system. Cavitation emissions from the UCAs insonified by Doppler pulses were recorded using a passive cavitation detection system and stable and inertial cavitation thresholds ascertained. Loss of echogenicity from ELIP and Definity® was assessed within regions of interest on B-mode images. A numerical model based on UCA rupture predicted the functional form of the loss of echogenicity from ELIP and Definity®. Stable and inertial cavitation thresholds were found to have a weak dependence on pulse duration. Stable cavitation thresholds were lower than inertial cavitation thresholds. The power of cavitation emissions was an exponential function of the loss of echogenicity over the investigated range of acoustic pressures. Both ELIP and Definity® lost more than 80% echogenicity before the onset of stable or inertial cavitation. Once this level of echogenicity loss occurred, both stable and inertial cavitation were detected in the physiologic flow phantom. These results imply that stable and

Cavitational Hydrothermal Oxidation: A New Remediation Process - Final Report

Energy Technology Data Exchange (ETDEWEB)

Suslick, K. S.

2001-07-05

During the past year, we have continued to make substantial scientific progress on our understanding of cavitation phenomena in aqueous media and applications of cavitation to remediation processes. Our efforts have focused on three separate areas: sonoluminescence as a probe of conditions created during cavitational collapse in aqueous media, the use of cavitation for remediation of contaminated water, and an addition of the use of ultrasound in the synthesis of novel heterogeneous catalysts for hydrodehalogenation of halocarbons under mild conditions.

RANS simulation of cavitation and hull pressure fluctuation for marine propeller operating behind-hull condition

Directory of Open Access Journals (Sweden)

Kwang-Jun Paik

2013-12-01

Full Text Available Simulations of cavitation flow and hull pressure fluctuation for a marine propeller operating behind a hull using the unsteady Reynolds-Averaged Navier-Stokes equations (RANS are presented. A full hull body submerged under the free surface is modeled in the computational domain to simulate directly the wake field of the ship at the propeller plane. Simulations are performed in design and ballast draught conditions to study the effect of cavitation number. And two propellers with slightly different geometry are simulated to validate the detectability of the numerical simulation. All simulations are performed using a commercial CFD software FLUENT. Cavitation patterns of the simulations show good agreement with the experimental results carried out in Samsung CAvitation Tunnel (SCAT. The simulation results for the hull pressure fluctuation induced by a propeller are also compared with the experimental results showing good agreement in the tendency and amplitude, especially, for the first blade frequency.

Cavitational hydrothermal oxidation: A new remediation process. 1998 annual progress report

International Nuclear Information System (INIS)

Suslick, K.S.

1998-01-01

'The primary goal is to develop a quantitative understanding of cavitation phenomena in aqueous media and the development of applications of cavitation to remediation processes. Efforts have focused on three separate areas: sonoluminescence as a probe of conditions created during cavitational collapse in aqueous media, the use of cavitation for remediation of contaminated water, and an addition of the use of ultrasound in the synthesis of novel heterogeneous catalysts for hydrodehalogenation of halocarbons under mild conditions. This report summarizes work after one year of a three year project. In order to gain further understanding of the conditions present during cavitation, the author has continued his studies of sonoluminescence. He has made recent breakthroughs in the use of emission spectroscopy for temperature and pressure measurement of cavitation events, which he expects to publish shortly. He has been able to measure for the first time the temperature of cavitation in water during multi-bubble cavitation in the presence of aromatic hydrocarbons. The emission from excited states of C 2 in water gives temperatures that are consistent with adiabatic compressional heating, with maximum temperatures of 4,300 K. Prior measurements of cavitation temperatures in low vapor pressure nonaqueous media gave somewhat higher temperatures of 5,000 K. This work lays permanently to rest exotic mechanisms for cavitational chemistry, at least for cavitation fields.'

Cavitational hydrothermal oxidation: A new remediation process. 1998 annual progress report

Energy Technology Data Exchange (ETDEWEB)

Suslick, K.S.

1998-06-01

'The primary goal is to develop a quantitative understanding of cavitation phenomena in aqueous media and the development of applications of cavitation to remediation processes. Efforts have focused on three separate areas: sonoluminescence as a probe of conditions created during cavitational collapse in aqueous media, the use of cavitation for remediation of contaminated water, and an addition of the use of ultrasound in the synthesis of novel heterogeneous catalysts for hydrodehalogenation of halocarbons under mild conditions. This report summarizes work after one year of a three year project. In order to gain further understanding of the conditions present during cavitation, the author has continued his studies of sonoluminescence. He has made recent breakthroughs in the use of emission spectroscopy for temperature and pressure measurement of cavitation events, which he expects to publish shortly. He has been able to measure for the first time the temperature of cavitation in water during multi-bubble cavitation in the presence of aromatic hydrocarbons. The emission from excited states of C{sub 2} in water gives temperatures that are consistent with adiabatic compressional heating, with maximum temperatures of 4,300 K. Prior measurements of cavitation temperatures in low vapor pressure nonaqueous media gave somewhat higher temperatures of 5,000 K. This work lays permanently to rest exotic mechanisms for cavitational chemistry, at least for cavitation fields.'

Hydrodynamic cavitation in Stokes flow of anisotropic fluids

OpenAIRE

Stieger, Tillmann; Agha, Hakam; Schoen, Martin; Mazza, Marco G.; Sengupta, Anupam

2017-01-01

Cavitation, the nucleation of vapour in liquids, is ubiquitous in fluid dynamics, and is often implicated in a myriad of industrial and biomedical applications. Although extensively studied in isotropic liquids, corresponding investigations in anisotropic liquids are largely lacking. Here, by combining liquid crystal microfluidic experiments, nonequilibrium molecular dynamics simulations and theoretical arguments, we report flow-induced cavitation in an anisotropic fluid. The cavitation domai...

Experience with control valve cavitation problems and their solutions

International Nuclear Information System (INIS)

Ozol, J.

1988-01-01

Pressure reduction in control valves can induce cavitation, which has three effects on the control valve. Firstly, it modifies or changes the hydraulic performance of the control valve. Since control valves are designed for noncavitating conditions, the result is usually reduced stability of the control valve or, in extreme cavitating conditions known as supercavitation, the valve may limit the flow rate and thus be undersized. Secondly, cavitation can cause material damage to valve parts, trim, or valve body, or erodes downstream piping; consequently, the valve or piping leaks. Thirdly, cavitation causes noise and vibration, which may cause major damage or destruction to equipment such as valve positioners, actuators, pipe supports and sometimes to other downstream valves. The purpose of this paper is twofold: (1) It describes the I.S.A. valve sizing equations and how they relate to cavitation. (2) It describes experiences with these three problems, and discusses corrective actions and practical approaches to their solution. This paper discusses thirteen cavitation experiences

Travelling Bubble Cavitation and Resulting Noise.

Science.gov (United States)

1981-03-02

pp. 22-26, 1968. 16. Il’ichev, V. I. "Statistical Model of the Onset of Hydrodynamic Cavitation Noise," Sixth All-Union Acoustic Conference...Collected Papers, Moscow, 1968. 17. Lyamshev, L. M. "On the Theory of Hydrodynamic Cavitation Noise," Soviet Physics-Acoustics, Vol. 15, pp. 494-498, 1970. 18

Incipient motion of gravel and coal beds

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

2. 1Department of Civil Engineering, Indian Institute of Technology, ... the particle size distribution curve following the relationship by Christensen .... where f = friction factor, ρ = mass density of fluid, and V = mean velocity of flow. .... for the incipient motion of gravel and coal beds have been represented by simple empirical.

Stabilizing in vitro ultrasound-mediated gene transfection by regulating cavitation.

Science.gov (United States)

Lo, Chia-Wen; Desjouy, Cyril; Chen, Shing-Ru; Lee, Jyun-Lin; Inserra, Claude; Béra, Jean-Christophe; Chen, Wen-Shiang

2014-03-01

It is well known that acoustic cavitation can facilitate the inward transport of genetic materials across cell membranes (sonoporation). However, partially due to the unstationary behavior of the initiation and leveling of cavitation, the sonoporation effect is usually unstable, especially in low intensity conditions. A system which is able to regulate the cavitation level during sonication by modulating the applied acoustic intensity with a feedback loop is implemented and its effect on in vitro gene transfection is tested. The regulated system provided better time stability and reproducibility of the cavitation levels than the unregulated conditions. Cultured hepatoma cells (BNL) mixed with 10 μg luciferase plasmids are exposed to 1-MHz pulsed ultrasound with or without cavitation regulation, and the gene transfection efficiency and cell viability are subsequently assessed. Experimental results show that for all exposure intensities (low, medium, and high), stable and intensity dependent, although not higher, gene expression could be achieved in the regulated cavitation system than the unregulated conditions. The cavitation regulation system provides a better control of cavitation and its bioeffect which are crucial important for clinical applications of ultrasound-mediated gene transfection. Copyright © 2013 Elsevier B.V. All rights reserved.

Development of a custom-made "smart-sphere" to assess incipient entrainment by rolling

Science.gov (United States)

Valyrakis, Manousos; Kitsikoudis, Vasileios; Alexakis, Athanasios; Trinder, Jon

2017-04-01

The most widely applied criterion for sediment incipient motion in engineering applications is the time- and space-averaged approach of critical Shields shear stress. Nonetheless, in the recent years published research has highlighted the importance of turbulence fluctuations in sediment incipient motion and its stochastic character. The present experimental study investigates statistically the link of the response of a "smart-pebble" to hydrodynamics in near-critical flow conditions and discusses how such a device can be utilized in engineering design. A set of specifically designed fluvial experiments monitoring the entrainment conditions for a "smart-pebble", were carried out in a tilting, recirculating flume in turbulent flow conditions while three-dimensional flow measurements were obtained with an acoustic Doppler velocimeter. The "smart-pebble" employed herein is a custom-made instrumented sphere with 7 cm diameter, which has a number of sensors embedded within its waterproof 3D-printed plastic shell. Specifically, the "smart-pebble" is equipped with miniaturized, off the shelf, low-cost, three-dimensional acceleration, orientation and angular displacement sensors. A 3D-printed local micro topography of known geometry was installed in the flume's test section and the "smart-pebble" was placed there in order to facilitate the analysis. Every time the "smart-sphere" is displaced by the flow a downstream located pin blocks its full entrainment. This allows for continuous recording of the entrainment events due to the passage of energetic events, after which the "smart-pebble" returns to its resting pocket. The "smart-pebble" device under such a configuration allows the recording of normally indiscernible (with the naked eye) vibrations, twitching motions, and full entrainments for the studied particle, allowing its analysis from a Langrangian framework. During the incipient motion experiments the retrieved data are stored in an internal memory unit or

Incipient toxicity of lithium to freshwater organisms representing a salmonid habitat

International Nuclear Information System (INIS)

Emery, R.; Klopfer, D.C.; Skalski, J.R.

1981-07-01

Because the eventual development of fusion power reactors could increase the mining, use and disposal of lithium five-fold by the year 2000, potential effects from unusual amounts of lithium in aquatic environments were investigated. Freshwater oganisms representing a Pacific Northwest salmonid habitat were exposed to elevated conentrations of lithium. Nine parameters were used to determine the incipient toxicity of lithium to rainbow trout (Salmo gairdneri), insect larvae (Chironomus sp.), and Columbia River periphyton. All three groups of biota were incipiently sensitive to lithium at concentrations ranging between 0.1 and 1 mg/L. These results correspond with the incipient toxicity of beryllium, a chemically similar component of fusion reactor cores. A maximum lithium concentration of 0.01 mg/L occurs naturally in most freshwater environments (beryllium is rarer). Therefore, a concentration range of 0.01 to 0.1 mg/L may be regarded as approaching toxic concentrations when assessing the hazards of lithium in freshwaters

Power cavitation-guided blood-brain barrier opening with focused ultrasound and microbubbles

Science.gov (United States)

Burgess, M. T.; Apostolakis, I.; Konofagou, E. E.

2018-03-01

Image-guided monitoring of microbubble-based focused ultrasound (FUS) therapies relies on the accurate localization of FUS-stimulated microbubble activity (i.e. acoustic cavitation). Passive cavitation imaging with ultrasound arrays can achieve this, but with insufficient spatial resolution. In this study, we address this limitation and perform high-resolution monitoring of acoustic cavitation-mediated blood-brain barrier (BBB) opening with a new technique called power cavitation imaging. By synchronizing the FUS transmit and passive receive acquisition, high-resolution passive cavitation imaging was achieved by using delay and sum beamforming with absolute time delays. Since the axial image resolution is now dependent on the duration of the received acoustic cavitation emission, short pulses of FUS were used to limit its duration. Image sets were acquired at high-frame rates for calculation of power cavitation images analogous to power Doppler imaging. Power cavitation imaging displays the mean intensity of acoustic cavitation over time and was correlated with areas of acoustic cavitation-induced BBB opening. Power cavitation-guided BBB opening with FUS could constitute a standalone system that may not require MRI guidance during the procedure. The same technique can be used for other acoustic cavitation-based FUS therapies, for both safety and guidance.

Solution to valve failures at Braidwood induced by service water cavitation

International Nuclear Information System (INIS)

Ozol, J.; Schipiour, B.K.; Wix, J.E.

1994-01-01

Control valves throttle fluid from a high pressure to a lower pressure. On water systems, this throttling process may be accompanied by cavitation, which induces valve noise, vibration, and material damage. Extensive and significant caviation erosion has been experienced the last 10 years in most service water control valve bodies, downstream flanges, and reducers at Braidwood Station. There have been 40 different and distinct cavitation-induced failures in the service water system at Braidwood Station. These failures have created significant costs and continue to be a lingering source of operational maintenance costs to the Commonwealth Edison Company, which is incurring significant financial losses. It should be noted that almost all service water control valves experience some cavitation effects. Cavitation and cavitation damage are complex and elusive phenomena for which no single, simple analytical model exists. The purpose of this paper is to explain features of service water control valve cavitation failures and some of the solutions used by Commonwealth Edison at their six nuclear stations. The paper discusses the following: (1) Braidwood's history of erosion from cavitation; (2) Erosion-corrosion considerations; (3) The Instrument Society of America's valve sizing equations and how they relate to cavitation; (4) Methods to eliminate cavitation; (5) Corrective actions and practical approaches used by Commonwealth Edison to eliminate cavitation

Forces and moments on a slender, cavitating body

Energy Technology Data Exchange (ETDEWEB)

Hailey, C.E.; Clark, E.L.; Buffington, R.J.

1988-01-01

Recently a numerical code has been developed at Sandia National Laboratories to predict the pitching moment, normal force, and axial force of a slender, supercavitating shape. The potential flow about the body and cavity is calculated using an axial distribution of source/sink elements. The cavity surface is assumed to be a constant pressure streamline, extending beyond the base of the model. Slender body approximation is used to model the crossflow for small angles of attack. A significant extension of previous work in cavitation flow is the inclusion of laminar and turbulent boundary layer solutions on the body. Predictions with this code, for axial force at zero angle of attack, show good agreement with experiments. There are virtually no published data availble with which to benchmark the pitching moment and normal force predictions. An experiment was designed to measure forces and moments on a supercavitation shape. The primary reason for the test was to obtain much needed data to benchmark the hydrodynamic force and moment predictions. Since the numerical prediction is for super cavitating shapes at very small cavitation numbers, the experiment was designed to be a ventilated cavity test. This paper describes the experimental procedure used to measure the pitching moment, axial and normal forces, and base pressure on a slender body with a ventilated cavity. Limited results are presented for pitching moment and normal force. 5 refs., 7 figs.

Enhancement of heat and mass transfer by cavitation

International Nuclear Information System (INIS)

Zhang, Y N; Du, X Z; Xian, H Z; Zhang, Y N

2015-01-01

In this paper, a brief summary of effects of cavitation on the heat and mass transfer are given. The fundamental studies of cavitation bubbles, including its nonlinearity, rectified heat and mass diffusion, are initially introduced. Then selected topics of cavitation enhanced heat and mass transfer were discussed in details including whales stranding caused by active sonar activity, pool boiling heat transfer, oscillating heat pipe and high intensity focused ultrasound treatment

Cellular High-Energy Cavitation Trauma - Description of a Novel In Vitro Trauma Model in Three Different Cell Types.

Science.gov (United States)

Cao, Yuli; Risling, Mårten; Malm, Elisabeth; Sondén, Anders; Bolling, Magnus Frödin; Sköld, Mattias K

2016-01-01

The mechanisms involved in traumatic brain injury have yet to be fully characterized. One mechanism that, especially in high-energy trauma, could be of importance is cavitation. Cavitation can be described as a process of vaporization, bubble generation, and bubble implosion as a result of a decrease and subsequent increase in pressure. Cavitation as an injury mechanism is difficult to visualize and model due to its short duration and limited spatial distribution. One strategy to analyze the cellular response of cavitation is to employ suitable in vitro models. The flyer-plate model is an in vitro high-energy trauma model that includes cavitation as a trauma mechanism. A copper fragment is accelerated by means of a laser, hits the bottom of a cell culture well causing cavitation, and shock waves inside the well and cell medium. We have found the flyer-plate model to be efficient, reproducible, and easy to control. In this study, we have used the model to analyze the cellular response to microcavitation in SH-SY5Y neuroblastoma, Caco-2, and C6 glioma cell lines. Mitotic activity in neuroblastoma and glioma was investigated with BrdU staining, and cell numbers were calculated using automated time-lapse imaging. We found variations between cell types and between different zones surrounding the lesion with these methods. It was also shown that the injured cell cultures released S-100B in a dose-dependent manner. Using gene expression microarray, a number of gene families of potential interest were found to be strongly, but differently regulated in neuroblastoma and glioma at 24 h post trauma. The data from the gene expression arrays may be used to identify new candidates for biomarkers in cavitation trauma. We conclude that our model is useful for studies of trauma in vitro and that it could be applied in future treatment studies.

Metal of cavitation erosion of a hydrodynamic reactor

Science.gov (United States)

Zakirzakov, A. G.; Brand, A. E.; Petryakov, V. A.; Gordievskaya, E. F.

2017-02-01

Cavitation erosion is a major cause of the petroleum equipment hydraulic erosion, which leads to the metal weight loss of the equipment and its breakdown, which can be followed by the full stop of the plant or company work. The probability of the metal weight loss and equipment failure can be reduced by the use of special protective coatings or rivets, made of the sacrificial metals, the use of which significantly increases the service life and the production equipment reliability. The article investigates the cavitation erosion effect, occurred under the condition of the advanced hydrodynamic cavitation on the hydrodynamic cavitation reactor. This article presents the results of the experiments and recommendations for increasing the operational resource.

Cavitation instability in bulk metallic glasses

Directory of Open Access Journals (Sweden)

Dai L.H.

2015-01-01

Full Text Available Recent experiments have shown that fracture surfaces of bulk metallic glasses (BMGs usually exhibit an intriguing nanoscale corrugation like fractographic feature mediated by nanoscale void formation. We attribute the onset of this nanoscale corrugation to TTZs (tension transformation zones mediated cavitation. In our recent study, the spall experiments of Zr-based BMG using a single-stage light gas gun were performed. To uncover the mechanisms of the spallation damage nucleation and evolution, the samples were designed to be subjected to dynamic tensile loadings of identical amplitude but with different durations by making use of the multi-stress pulse and the double-flyer techniques. It is clearly revealed that the macroscopic spall fracture in BMGs originates from the nucleation, growth and coalescence of micro-voids. Then, a microvoid nucleation model of BMGs based on free volume theory is proposed, which indicates that the nucleation of microvoids at the early stage of spallation in BMGs is resulted from diffusion and coalescence of free volume. Furthermore, a theoretical model of void growth in BMGs undergoing remote dynamic hydrostatic tension is developed. The critical condition of cavitation instability is obtained. It is found that dynamic void growth in BMGs can be well controlled by a dimensionless inertial number characterizing the competition between intrinsic and extrinsic time scales. To unveil the atomic-level mechanism of cavitation, a systematic molecular dynamics (MD simulation of spallation behaviour of a binary metallic glass with different impact velocities was performed. It is found that micro-void nucleation is determined TTZs while the growth is controlled by shear transformation zones (STZs at atomic scale.

Correlating Inertial Acoustic Cavitation Emissions with Material Erosion Resistance

Science.gov (United States)

Ibanez, I.; Hodnett, M.; Zeqiri, B.; Frota, M. N.

The standard ASTM G32-10 concerns the hydrodynamic cavitation erosion resistance of materials by subjecting them to acoustic cavitation generated by a sonotrode. The work reported extends this technique by detecting and monitoring the ultrasonic cavitation, considered responsible for the erosion process, specifically for coupons of aluminium-bronze alloy. The study uses a 65 mm diameter variant of NPL's cavitation sensor, which detects broadband acoustic emissions, and logs acoustic signals generated in the MHz frequency range, using NPL's Cavimeter. Cavitation readings were made throughout the exposure duration, which was carried out at discrete intervals (900 to 3600 s), allowing periodic mass measurements to be made to assess erosion loss under a strict protocol. Cavitation measurements and erosion were compared for different separations of the sonotrode tip from the material under test. The maximum variation associated with measurement of cavitation level was between 2.2% and 3.3% when the separation (λ) between the transducer horn and the specimen increased from 0.5 to 1.0 mm, for a transducer (sonotrode) displacement amplitude of 43.5 μm. Experiments conducted at the same transducer displacement amplitude show that the mass loss of the specimen -a measure of erosion- was 67.0 mg (λ = 0.5 mm) and 66.0 mg (λ = 1.0 mm).

Detecting cavitation in vivo from shock-wave therapy devices

Science.gov (United States)

Matula, Thomas J.; Yu, Jinfei; Bailey, Michael R.

2005-04-01

Extracorporeal shock-wave therapy (ESWT) has been used as a treatment for plantar faciitis, lateral epicondylitis, shoulder tendonitis, non-unions, and other indications where conservative treatments have been unsuccessful. However, in many areas, the efficacy of SW treatment has not been well established, and the mechanism of action, particularly the role of cavitation, is not well understood. Research indicates cavitation plays an important role in other ultrasound therapies, such as lithotripsy and focused ultrasound surgery, and in some instances, cavitation has been used as a means to monitor or detect a biological effect. Although ESWT can generate cavitation easily in vitro, it is unknown whether or not cavitation is a significant factor in vivo. The purpose of this investigation is to use diagnostic ultrasound to detect and monitor cavitation generated by ESWT devices in vivo. Diagnostic images are collected at various times during and after treatment. The images are then post-processed with image-processing algorithms to enhance the contrast between bubbles and surrounding tissue. The ultimate goal of this research is to utilize cavitation as a means for optimizing shock wave parameters such as amplitude and pulse repetition frequency. [Work supported by APL internal funds and NIH DK43881 and DK55674.

Synchrotron x-ray imaging of acoustic cavitation bubbles induced by acoustic excitation

International Nuclear Information System (INIS)

Jung, Sung Yong; Park, Han Wook; Park, Sung Ho; Lee, Sang Joon

2017-01-01

The cavitation induced by acoustic excitation has been widely applied in various biomedical applications because cavitation bubbles can enhance the exchanges of mass and energy. In order to minimize the hazardous effects of the induced cavitation, it is essential to understand the spatial distribution of cavitation bubbles. The spatial distribution of cavitation bubbles visualized by the synchrotron x-ray imaging technique is compared to that obtained with a conventional x-ray tube. Cavitation bubbles with high density in the region close to the tip of the probe are visualized using the synchrotron x-ray imaging technique, however, the spatial distribution of cavitation bubbles in the whole ultrasound field is not detected. In this study, the effects of the ultrasound power of acoustic excitation and working medium on the shape and density of the induced cavitation bubbles are examined. As a result, the synchrotron x-ray imaging technique is useful for visualizing spatial distributions of cavitation bubbles, and it could be used for optimizing the operation conditions of acoustic cavitation. (paper)

On the effect of cross sectional shape on incipient motion and deposition of sediments in fixed bed channels

Directory of Open Access Journals (Sweden)

Safari Mir-Jafar-Sadegh

2014-03-01

Full Text Available The condition of incipient motion and deposition are of the essential issues for the study of sediment transport. This phenomenon is of great importance to hydraulic engineers for designing sewers, drainage, as well as other rigid boundary channels. This is a study carried out with the objectives of describing the effect of cross-sectional shape on incipient motion and deposition of particles in rigid boundary channels. In this research work, the experimental data given by Loveless (1992 and Mohammadi (2005 are used. On the basis of the critical velocity approach, a new incipient motion equation for a V-shaped bottom channel and incipient deposition of sediment particles equations for rigid boundary channels having circular, rectangular, and U-shaped cross sections are obtained. New equations were compared to the other incipient motion equations. The result shows that the cross-sectional shape is an important factor for defining the minimum velocity for no-deposit particles. This study also distinguishes incipient motion of particles from incipient deposition for particles. The results may be useful for designing fixed bed channels with a limited deposition condition.

Numerical analysis of the effects of radiation heat transfer and ionization energy loss on the cavitation Bubble's dynamics

Science.gov (United States)

Mahdi, M.; Ebrahimi, R.; Shams, M.

2011-06-01

A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with the experimental data and a good correspondence was observed. The dynamics of hydrofoil cavitation bubble were also investigated. It was concluded that the thermal radiation heat transfer rate strongly depended on the cavitation number, initial bubble radius and hydrofoil angle of attack.

VibroCav : Hydrodynamic Vibration and Cavitation Technology

NARCIS (Netherlands)

Bakker, T.W.

2012-01-01

Vibration and cavitation can be generated in many ways and serve many useful purposes. This study describes physical aspects of useful vibration and cavitation for a broad spectrum of applications at atmospheric or elevated pressures. After a review of available devices, hydrodynamic

Numerical investigation of tip clearance cavitation in Kaplan runners

Science.gov (United States)

Nikiforova, K.; Semenov, G.; Kuznetsov, I.; Spiridonov, E.

2016-11-01

There is a gap between the Kaplan runner blade and the shroud that makes for a special kind of cavitation: cavitation in the tip leakage flow. Two types of cavitation caused by the presence of clearance gap are known: tip vortex cavitation that appears at the core of the rolled up vortex on the blade suction side and tip clearance cavitation that appears precisely in the gap between the blade tip edge and the shroud. In the context of this work numerical investigation of the model Kaplan runner has been performed taking into account variable tip clearance for several cavitation regimes. The focus is put on investigation of structure and origination of mechanism of cavitation in the tip leakage flow. Calculations have been performed with the help of 3-D unsteady numerical model for two-phase medium. Modeling of turbulent flow in this work has been carried out using full equations of Navier-Stokes averaged by Reynolds with correction for streamline curvature and system rotation. For description of this medium (liquid-vapor) simplification of Euler approach is used; it is based on the model of interpenetrating continuums, within the bounds of this two- phase medium considered as a quasi-homogeneous mixture with the common velocity field and continuous distribution of density for both phases. As a result, engineering techniques for calculation of cavitation conditioned by existence of tip clearance in model turbine runner have been developed. The detailed visualization of the flow was carried out and vortex structure on the suction side of the blade was reproduced. The range of frequency with maximum value of pulsation was assigned and maximum energy frequency was defined; it is based on spectral analysis of the obtained data. Comparison between numerical computation results and experimental data has been also performed. The location of cavitation zone has a good agreement with experiment for all analyzed regimes.

Incipient and overt diabetic nephropathy in African Americans with NIDDM.

Science.gov (United States)

Dasmahapatra, A; Bale, A; Raghuwanshi, M P; Reddi, A; Byrne, W; Suarez, S; Nash, F; Varagiannis, E; Skurnick, J H

1994-04-01

OBJECTIVE--To determine the prevalence of incipient and overt nephropathy in African-American subjects with non-insulin-dependent diabetes mellitus (NIDDM) attending a hospital clinic. Contributory factors, such as blood pressure (BP), duration and age at onset of diabetes, hyperglycemia, hyperlipidemia, and body mass index (BMI) also were evaluated. RESEARCH DESIGN AND METHODS--We recruited 116 African-American subjects with NIDDM for this cross-sectional, descriptive, and analytical study. BP, BMI, 24-h urine albumin excretion, creatinine clearance, serum creatinine, lipids, and GHb levels were measured. Albumin excretion rate (AER) was calculated, and subjects were divided into three groups: no nephropathy (AER 200 micrograms/min). Frequency of hypertension and nephropathy was analyzed by chi 2 testing, group means were compared using analysis of variance, and linear correlations were performed between AER and other variables. Multiple regression analysis was used to examine the association of these variables while controlling for the effects of other variables. RESULTS--Increased AER was present in 50% of our subjects; 31% had incipient and 19% had overt nephropathy. Hypertension was present in 72.4%; nephropathy, particularly overt nephropathy, was significantly more prevalent in the hypertensive group. Mean BP and diastolic blood pressure (dBP) were higher in the groups with incipient and overt nephropathy, and systolic blood pressure (sBP) was increased in overt nephropathy. Men with either form of nephropathy had higher sBP, dBP, and mean BP, whereas only women with overt nephropathy had increased sBP and mean BP. Subjects with incipient or overt nephropathy had a longer duration of diabetes, and those with overt nephropathy had a younger age at onset of diabetes. By multiple regression analysis, AER correlated with younger age at diabetes onset, but not with diabetes duration. No correlation with age, lipid levels, or GHb was noted. BMI correlated with AER

Ultrasound-enhanced thrombolysis using Definity as a cavitation nucleation agent.

Science.gov (United States)

Datta, Saurabh; Coussios, Constantin-C; Ammi, Azzdine Y; Mast, T Douglas; de Courten-Myers, Gabrielle M; Holland, Christy K

2008-09-01

Ultrasound has been shown previously to act synergistically with a thrombolytic agent, such as recombinant tissue plasminogen activator (rt-PA) to accelerate thrombolysis. In this in vitro study, a commercial contrast agent, Definity, was used to promote and sustain the nucleation of cavitation during pulsed ultrasound exposure at 120 kHz. Ultraharmonic signals, broadband emissions and harmonics of the fundamental were measured acoustically by using a focused hydrophone as a passive cavitation detector and used to quantify the level of cavitation activity. Human whole blood clots suspended in human plasma were exposed to a combination of rt-PA, Definity and ultrasound at a range of ultrasound peak-to-peak pressure amplitudes, which were selected to expose clots to various degrees of cavitation activity. Thrombolytic efficacy was determined by measuring clot mass loss before and after the treatment and correlated with the degree of cavitation activity. The penetration depth of rt-PA and plasminogen was also evaluated in the presence of cavitating microbubbles using a dual-antibody fluorescence imaging technique. The largest mass loss (26.2%) was observed for clots treated with 120-kHz ultrasound (0.32-MPa peak-to-peak pressure amplitude), rt-PA and stable cavitation nucleated by Definity. A significant correlation was observed between mass loss and ultraharmonic signals (r = 0.85, p cavitation activity. Stable cavitation activity plays an important role in enhancement of thrombolysis and can be monitored to evaluate the efficacy of thrombolytic treatment.

Numerical simulation of cavitation flow characteristic on Pelton turbine bucket surface

Science.gov (United States)

Zeng, C. J.; Xiao, Y. X.; Zhu, W.; Yao, Y. Y.; Wang, Z. W.

2015-01-01

The internal flow in the rotating bucket of Pelton turbine is free water sheet flow with moving boundary. The runner operates under atmospheric and the cavitation in the bucket is still a controversial problem. While more and more field practice proved that there exists cavitation in the Pelton turbine bucket and the cavitation erosion may occur at the worst which will damage the bucket. So a well prediction about the cavitation flow on the bucket surface of Pelton turbine and the followed cavitation erosion characteristic can effectively guide the optimization of Pelton runner bucket and the stable operation of unit. This paper will investigate the appropriate numerical model and method for the unsteady 3D water-air-vapour multiphase cavitation flow which may occur on the Pelton bucket surface. The computational domain will include the nozzle pipe flow, semi-free surface jet and runner domain. Via comparing the numerical results of different turbulence, cavity and multiphase models, this paper will determine the suitable numerical model and method for the simulation of cavitation on the Pelton bucket surface. In order to investigate the conditions corresponding to the cavitation phenomena on the bucket surface, this paper will adopt the suitable model to simulate the various operational conditions of different water head and needle travel. Then, the characteristics of cavitation flow the development process of cavitation will be analysed in in great detail.

Numerical simulation of cavitation flow characteristic on Pelton turbine bucket surface

International Nuclear Information System (INIS)

Zeng, C J; Xiao, Y X; Zhu, W; Yao, Y Y; Wang, Z W

2015-01-01

The internal flow in the rotating bucket of Pelton turbine is free water sheet flow with moving boundary. The runner operates under atmospheric and the cavitation in the bucket is still a controversial problem. While more and more field practice proved that there exists cavitation in the Pelton turbine bucket and the cavitation erosion may occur at the worst which will damage the bucket. So a well prediction about the cavitation flow on the bucket surface of Pelton turbine and the followed cavitation erosion characteristic can effectively guide the optimization of Pelton runner bucket and the stable operation of unit. This paper will investigate the appropriate numerical model and method for the unsteady 3D water-air-vapour multiphase cavitation flow which may occur on the Pelton bucket surface. The computational domain will include the nozzle pipe flow, semi-free surface jet and runner domain. Via comparing the numerical results of different turbulence, cavity and multiphase models, this paper will determine the suitable numerical model and method for the simulation of cavitation on the Pelton bucket surface. In order to investigate the conditions corresponding to the cavitation phenomena on the bucket surface, this paper will adopt the suitable model to simulate the various operational conditions of different water head and needle travel. Then, the characteristics of cavitation flow the development process of cavitation will be analysed in in great detail

Biomedical device prototype based on small scale hydrodynamic cavitation

Science.gov (United States)

Ghorbani, Morteza; Sozer, Canberk; Alcan, Gokhan; Unel, Mustafa; Ekici, Sinan; Uvet, Huseyin; Koşar, Ali

2018-03-01

This study presents a biomedical device prototype based on small scale hydrodynamic cavitation. The application of small scale hydrodynamic cavitation and its integration to a biomedical device prototype is offered as an important alternative to other techniques, such as ultrasound therapy, and thus constitutes a local, cheap, and energy-efficient solution, for urinary stone therapy and abnormal tissue ablation (e.g., benign prostate hyperplasia (BPH)). The destructive nature of bubbly, cavitating, flows was exploited, and the potential of the prototype was assessed and characterized. Bubbles generated in a small flow restrictive element (micro-orifice) based on hydrodynamic cavitation were utilized for this purpose. The small bubbly, cavitating, flow generator (micro-orifice) was fitted to a small flexible probe, which was actuated with a micromanipulator using fine control. This probe also houses an imaging device for visualization so that the emerging cavitating flow could be locally targeted to the desired spot. In this study, the feasibility of this alternative treatment method and its integration to a device prototype were successfully accomplished.

Biomedical device prototype based on small scale hydrodynamic cavitation

Directory of Open Access Journals (Sweden)

Morteza Ghorbani

2018-03-01

Full Text Available This study presents a biomedical device prototype based on small scale hydrodynamic cavitation. The application of small scale hydrodynamic cavitation and its integration to a biomedical device prototype is offered as an important alternative to other techniques, such as ultrasound therapy, and thus constitutes a local, cheap, and energy-efficient solution, for urinary stone therapy and abnormal tissue ablation (e.g., benign prostate hyperplasia (BPH. The destructive nature of bubbly, cavitating, flows was exploited, and the potential of the prototype was assessed and characterized. Bubbles generated in a small flow restrictive element (micro-orifice based on hydrodynamic cavitation were utilized for this purpose. The small bubbly, cavitating, flow generator (micro-orifice was fitted to a small flexible probe, which was actuated with a micromanipulator using fine control. This probe also houses an imaging device for visualization so that the emerging cavitating flow could be locally targeted to the desired spot. In this study, the feasibility of this alternative treatment method and its integration to a device prototype were successfully accomplished.

Assessment of cavitation in artificial approximal dental lesions with near-IR imaging

Science.gov (United States)

Simon, Jacob C.; Darling, Cynthia L.; Fried, Daniel

2017-02-01

Bitewing radiography is still considered state-of-the-art diagnostic technology for assessing cavitation within approximal carious dental lesions, even though radiographs cannot resolve cavitated surfaces but instead are used to measure lesion depth in order to predict cavitation. Clinicians need new technologies capable of determining whether approximal carious lesions have become cavitated because not all lesions progress to cavitation. Assessing lesion cavitation from near-infrared (NIR) imaging methods holds great potential due to the high transparency of enamel in the NIR region from λ=1300-1700-nm, which allows direct visualization and quantified measurements of enamel demineralization. The objective of this study was to measure the change in lesion appearance between non-cavitated and cavitated lesions in artificially generated lesions using NIR imaging modalities (two-dimensional) at λ=1300-nm and λ=1450-nm and cross-polarization optical coherence tomography (CP-OCT) (thee-dimensional) λ=1300-nm. Extracted human posterior teeth with sound proximal surfaces were chosen for this study and imaged before and after artificial lesions were made. A high speed dental hand piece was used to create artificial cavitated proximal lesions in sound samples and imaged. The cavitated artificial lesions were then filled with hydroxyapatite powder to simulate non-cavitated proximal lesions.

Cavitation-aided grain refinement in aluminium alloys

NARCIS (Netherlands)

Atamanenko, T.V.

2010-01-01

This thesis deals with grain refinement under the influence of ultrasonic-driven cavitation in aluminium casting processes. Three major goals of this research were: (1) to identify the mechanism of the cavitation-aided grain refinement at different stages of solidification; (2) to reveal the

Numerical and experimental study of a hydrodynamic cavitation tube

Science.gov (United States)

Hu, H.; Finch, J. A.; Zhou, Z.; Xu, Z.

1998-08-01

A numerical analysis of hydrodynamics in a cavitation tube used for activating fine particle flotation is described. Using numerical procedures developed for solving the turbulent k-ɛ model with boundary fitted coordinates, the stream function, vorticity, velocity, and pressure distributions in a cavitation tube were calculated. The calculated pressure distribution was found to be in excellent agreement with experimental results. The requirement of a pressure drop below approximately 10 m water for cavitation to occur was observed experimentally and confirmed by the model. The use of the numerical procedures for cavitation tube design is discussed briefly.

Cavitation Erosion of Nodular Cast Iron − Microstructural Effects

Directory of Open Access Journals (Sweden)

Orłowicz A.W.

2017-12-01

Full Text Available The paper deals with susceptibility of nodular cast iron with ferritic-pearlitic matrix on cavitation erosion. Cavitation tests were carried out with the use of a cavitation erosion vibratory apparatus employing a vibration exciter operated at frequency of 20 kHz. The study allowed to determine the sequence of subsequent stages in which microstructure of cast iron in superficial regions is subject to degradation. The first features to be damaged are graphite precipitates. The ferritic matrix of the alloy turned out to be definitely less resistant to cavitation erosion compared to the pearlitic matrix component.

Evaluation of a shock wave induced cavitation activity both in vitro and in vivo

International Nuclear Information System (INIS)

Tu Juan; Matula, Thomas J; Bailey, Michael R; Crum, Lawrence A

2007-01-01

This study evaluated the cavitation activity induced by shock wave (SW) pulses, both in vitro and in vivo, based on the area measurements of echogenic regions observed in B-mode ultrasound images. Residual cavitation bubble clouds induced by SW pulses were detected as echogenic regions in B-mode images. The temporal evolution of residual bubble clouds, generated by SWs with varying lithotripter charging voltage and pulse repetition frequency (PRF), was analyzed by measuring the time-varying behaviors of the echogenic region areas recorded in B-mode images. The results showed that (1) the area of SW-induced echogenic regions enlarged with increased SW pulse number; (2) echogenic regions in the B-mode images dissipated gradually after ceasing the SWs, which indicated the dissolution of the cavitation bubbles; and (3) larger echogenic regions were generated with higher charging voltage or PRF

Study of cavitation in hydro turbines. A review

Energy Technology Data Exchange (ETDEWEB)

Kumar, Pardeep; Saini, R.P. [Alternate Hydro Energy Centre, Indian Institute of Technology, Roorkee 247667 (India)

2010-01-15

Reaction turbines basically Francis turbines and propeller/Kaplan turbines are suitable for medium and low head hydropower sites. The management of the small hydropower plants is an important factor, for achieving higher efficiency of hydro turbines with time. Turbines show declined performance after few years of operation, as they get severely damaged due to various reasons. One of the important reasons is erosive wear of the turbines due to cavitation. Reaction turbines, however are more prone to cavitation especially Francis turbines where a zone in the operating range is seriously affected by cavitation and considered as forbidden zone. Cavitation is a phenomenon which manifests itself in the pitting of the metallic surfaces of turbine parts because of the formation of cavities. In the present paper, studies undertaken in this field by several investigators have been discussed extensively. Based on literature survey various aspects related to cavitation in hydro turbines, different causes for the declined performance and efficiency of the hydro turbines and suitable remedial measures suggested by various investigators have been discussed. (author)

Ultrafast cavitation induced by an X-ray laser in water drops

Science.gov (United States)

Stan, Claudiu; Willmott, Philip; Stone, Howard; Koglin, Jason; Liang, Mengning; Aquila, Andrew; Robinson, Joseph; Gumerlock, Karl; Blaj, Gabriel; Sierra, Raymond; Boutet, Sebastien; Guillet, Serge; Curtis, Robin; Vetter, Sharon; Loos, Henrik; Turner, James; Decker, Franz-Josef

2016-11-01

Cavitation in pure water is determined by an intrinsic heterogeneous cavitation mechanism, which prevents in general the experimental generation of large tensions (negative pressures) in bulk liquid water. We developed an ultrafast decompression technique, based on the reflection of shock waves generated by an X-ray laser inside liquid drops, to stretch liquids to large negative pressures in a few nanoseconds. Using this method, we observed cavitation in liquid water at pressures below -100 MPa. These large tensions exceed significantly those achieved previously, mainly due to the ultrafast decompression. The decompression induced by shock waves generated by an X-ray laser is rapid enough to continue to stretch the liquid phase after the heterogeneous cavitation occurs in water, despite the rapid growth of cavitation nanobubbles. We developed a nucleation-and-growth hydrodynamic cavitation model that explains our results and estimates the concentration of heterogeneous cavitation nuclei in water.

Transition of cavitating flow to supercavitation within Venturi nozzle - hysteresis investigation

Science.gov (United States)

Jiří, Kozák; Pavel, Rudolf; Rostislav, Huzlík; Martin, Hudec; Radomír, Chovanec; Ondřej, Urban; Blahoslav, Maršálek; Eliška, Maršálková; František, Pochylý; David, Štefan

Cavitation is usually considered as undesirable phenomena. On the other hand, it can be utilized in many applications. One of the technical applications is using cavitation in water treatment, where hydrodynamic cavitation seems to be effective way how to reduce cyanobacteria within large bulks of water. The main scope of this paper is investigation of the cavitation within Venturi nozzle during the transition from fully developed cavitation to supercavitation regime and vice versa. Dynamics of cavitation was investigated using experimental data of pressure pulsations and analysis of high speed videos, where FFT of the pixel intensity and Proper Orthogonal Decomposition (POD) of the records were done to identify dominant frequencies connected with the presence of cavitation. The methodology of the high speed (HS) records semiautomated analysis using the FFT was described. Obtained results were correlated and above that the possible presence of hysteresis was discussed.

Modelling cavitating flow around underwater missiles

Directory of Open Access Journals (Sweden)

Fabien Petitpas

2011-12-01

Full Text Available The diffuse interface model of Saurel et al. (2008 is used for the computation of compressible cavitating flows around underwater missiles. Such systems use gas injection and natural cavitation to reduce drag effects. Consequently material interfaces appear separating liquid and gas. These interfaces may have a really complex dynamics such that only a few formulations are able to predict their evolution. Contrarily to front tracking or interface reconstruction method the interfaces are computed as diffused numerical zones, that are captured in a routinely manner, as is done usually with gas dynamics solvers for shocks and contact discontinuity. With the present approach, a single set of partial differential equations is solved everywhere, with a single numerical scheme. This leads to very efficient solvers. The algorithm derived in Saurel et al. (2009 is used to compute cavitation pockets around solid bodies. It is first validated against experiments done in cavitation tunnel at CNU. Then it is used to compute flows around high speed underwater systems (Shkval-like missile. Performance data are then computed showing method ability to predict forces acting on the system.

Twin boundary cavitation in aged type 304 stainless steel

International Nuclear Information System (INIS)

Sikka, V.K.; Swindeman, R.W.; Brinkman, C.R.

1975-10-01

A transition from grain to twin boundary cavitation was observed in aged-and-creep-tested type 304 stainless steel. Evidence of twin boundary cavitation has also been observed for unaged material under certain test conditions. This same behavior was also found in aged type 316 stainless steel. Several possible reasons have been suggested for the absence of frequently observed grain boundary cavitation

Cavitational Hydrothermal Oxidation: A New Remediation Process - Final Report; FINAL

International Nuclear Information System (INIS)

Suslick, K. S.

2001-01-01

During the past year, we have continued to make substantial scientific progress on our understanding of cavitation phenomena in aqueous media and applications of cavitation to remediation processes. Our efforts have focused on three separate areas: sonoluminescence as a probe of conditions created during cavitational collapse in aqueous media, the use of cavitation for remediation of contaminated water, and an addition of the use of ultrasound in the synthesis of novel heterogeneous catalysts for hydrodehalogenation of halocarbons under mild conditions

Stress corrosion cracking mitigation by ultrasound induced cavitation technique

Energy Technology Data Exchange (ETDEWEB)

Fong, C.; Lee, Y.C. [Industrial Technology Research Inst., Taiwan (China); Yeh, T.K. [National Tsing Hua Univ., Taiwan (China)

2014-07-01

Cavitation is usually considered as a damaging mechanism under erosion corrosion condition. However, if used appropriately, cavitation can be applied as a peening technique for surface stress modification process. The aim of surface stress modification is to alter the stress state of processed surface through direct or indirect thermo-mechanical treatments to reduce cracking problems initiated from surface. Ultrasonic devices are used to generate cavitation bubbles which when collapse will produce high intensity shock waves and high velocity micro-jet streams. The cavitation impact when properly controlled will create plastically deformed compressive layers in nearby surfaces and minimize cracking susceptibility in corrosive environments. This study is to investigate the effectiveness of Ultrasound Induced Cavitation (UIC) technique in surface stress improvement. Ultrasonic cavitation treatment of SS304 stainless steel under pure water is carried out with different controlling parameters. The cavitation impact on SS304 surface is measured in terms of surface roughness, surface strain, hardness, and microstructural characteristics. The in-depth residual stress distribution and crack mitigation effect are also evaluated. Test result indicates ultrasound induced cavitation treatment only has minor effect on surface physical characteristics. The extent of compressive stress produced on top surface exceeds the yield strength and can reach a depth above 150 μm. The maximum surface strain measured is generally below 20%, which is not considered detrimental to accelerate crack initiation. Stress corrosion verification tests show UIC treatment is capable in preventing environmental assisted cracking of stainless steels in severely corrosive conditions. In view of the test results, UIC technique has demonstrated to be a low cost, low contaminating, and effective surface stress improvement technology. (author)

Stress corrosion cracking mitigation by ultrasound induced cavitation technique

International Nuclear Information System (INIS)

Fong, C.; Lee, Y.C.; Yeh, T.K.

2014-01-01

Cavitation is usually considered as a damaging mechanism under erosion corrosion condition. However, if used appropriately, cavitation can be applied as a peening technique for surface stress modification process. The aim of surface stress modification is to alter the stress state of processed surface through direct or indirect thermo-mechanical treatments to reduce cracking problems initiated from surface. Ultrasonic devices are used to generate cavitation bubbles which when collapse will produce high intensity shock waves and high velocity micro-jet streams. The cavitation impact when properly controlled will create plastically deformed compressive layers in nearby surfaces and minimize cracking susceptibility in corrosive environments. This study is to investigate the effectiveness of Ultrasound Induced Cavitation (UIC) technique in surface stress improvement. Ultrasonic cavitation treatment of SS304 stainless steel under pure water is carried out with different controlling parameters. The cavitation impact on SS304 surface is measured in terms of surface roughness, surface strain, hardness, and microstructural characteristics. The in-depth residual stress distribution and crack mitigation effect are also evaluated. Test result indicates ultrasound induced cavitation treatment only has minor effect on surface physical characteristics. The extent of compressive stress produced on top surface exceeds the yield strength and can reach a depth above 150 μm. The maximum surface strain measured is generally below 20%, which is not considered detrimental to accelerate crack initiation. Stress corrosion verification tests show UIC treatment is capable in preventing environmental assisted cracking of stainless steels in severely corrosive conditions. In view of the test results, UIC technique has demonstrated to be a low cost, low contaminating, and effective surface stress improvement technology. (author)

Cavitation damage prediction for the JSNS mercury target vessel

Energy Technology Data Exchange (ETDEWEB)

Naoe, Takashi, E-mail: naoe.takashi@jaea.go.jp; Kogawa, Hiroyuki; Wakui, Takashi; Haga, Katsuhiro; Teshigawara, Makoto; Kinoshita, Hidetaka; Takada, Hiroshi; Futakawa, Masatoshi

2016-01-15

The liquid mercury target system for the Japan Spallation Neutron Source (JSNS) at the Materials and Life science experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC) is designed to produce pulsed neutrons. The mercury target vessel in this system, which is made of type 316L stainless steel, is damaged by pressure wave-induced cavitation due to proton beam bombardment. Currently, cavitation damage is considered to be the dominant factor influencing the service life of the target vessel rather than radiation damage. In this study, cavitation damage to the interior surface of the target vessel was predicted on the basis of accumulated damage data from off-beam and on-beam experiments. The predicted damage was compared with the damage observed in a used target vessel. Furthermore, the effect of injecting gas microbubbles on cavitation damage was predicted through the measurement of the acoustic vibration of the target vessel. It was shown that the predicted depth of cavitation damage is reasonably coincident with the observed results. Moreover, it was confirmed that the injection of gas microbubbles had an effect on cavitation damage.

Deformation-induced martensite and resistance to cavitation erosion

International Nuclear Information System (INIS)

Richman, R.H.

1995-01-01

Exposure to cavitating liquids can induce surface transformation in metastable alloys, notably the 18Cr-8Ni class of stainless steels. The question of whether such transformation contributes to erosion resistance has not been resolved. To address that issue, two metastable stainless steels (Types 301 and 304L) and a near-equiatomic NiTi alloy were subjected to cavitation. Magnetic measurements during and after cavitation erosion indicate that substantial reversion of deformation-induced martensite occurs in the highly deformed surface layers of the stainless steels. Thus, cyclic formation and reversion of martensite is deduced to be a non-trivial energy-adsorption mechanism in those steels. The extreme case of cyclic induction and essentially complete reversion of martensite is illustrated by superelastic NiTi, which is extraordinarily resistant to cavitation damage. (orig.)

Controlling the cavitation phenomenon of evolution on a butterfly valve

International Nuclear Information System (INIS)

Baran, G; Safta, C A; Catana, I; Magheti, I; Savu, M

2010-01-01

Development of the phenomenon of cavitation in cavitation behavior requires knowledge of both plant and equipment working in the facility. This paper presents a diagram of cavitational behavior for a butterfly valve with a diameter of 100 mm at various openings, which was experimentally built. We proposed seven stages of evolution of the phenomenon of cavitation in the case of a butterfly valve. All these phases are characterized by pressure drop, noise and vibration at various flow rates and flow sections through the valve. The level of noise and vibration for the seven stages of development of the phenomenon of cavitation were measured simultaneously. The experimental measurements were comprised in a knowledge database used in training of a neural network of a neural flow controller that maintains flow rate constantly in the facility by changing the opening butterfly valve. A fuzzy position controller is used to access the valve open. This is the method proposed to provide operational supervision outside the cavitation for a butterfly valve.

Controlling the cavitation phenomenon of evolution on a butterfly valve

Energy Technology Data Exchange (ETDEWEB)

Baran, G; Safta, C A [Department of Hydraulic and Hydraulic Machineries, University Politehnica of Bucharest, 313 Splaiul Independentei, Bucharest, 060042 (Romania); Catana, I [Department of Control and Computer Science, University Politehnica of Bucharest (Romania); Magheti, I; Savu, M, E-mail: baran_gheorghe@yahoo.co.u [Department of Mechanical Engineering, University Politehnica of Bucharest (Romania)

2010-08-15

Development of the phenomenon of cavitation in cavitation behavior requires knowledge of both plant and equipment working in the facility. This paper presents a diagram of cavitational behavior for a butterfly valve with a diameter of 100 mm at various openings, which was experimentally built. We proposed seven stages of evolution of the phenomenon of cavitation in the case of a butterfly valve. All these phases are characterized by pressure drop, noise and vibration at various flow rates and flow sections through the valve. The level of noise and vibration for the seven stages of development of the phenomenon of cavitation were measured simultaneously. The experimental measurements were comprised in a knowledge database used in training of a neural network of a neural flow controller that maintains flow rate constantly in the facility by changing the opening butterfly valve. A fuzzy position controller is used to access the valve open. This is the method proposed to provide operational supervision outside the cavitation for a butterfly valve.

An experimental investigation of hydrodynamic cavitation in micro-Venturis

Science.gov (United States)

Mishra, Chandan; Peles, Yoav

2006-10-01

The existence of hydrodynamic cavitation in the flow of de-ionized water through micro-Venturis has been witnessed in the form of traveling bubble cavitation and fully developed streamer bubble/supercavitation, and their mechanisms have been discussed. High-speed photography and flow visualization disclose inchoate cavitation bubbles emerging downstream from the micro-Venturi throat and the presence of a single streamer bubble/supercavity, which is equidistant from the micro device walls. The supercavity initiates inside the diffuser section and extends until the microchannel exit and proceeds to bifurcate the incoming flow. This article strives to provide numerical data and experimental details of hydrodynamic cavitation taking place within micro-Venturis.

Photoacoustic cavitation for theranostics: mechanism, current progress and applications

International Nuclear Information System (INIS)

Feng, Y; Qin, D; Wan, M

2015-01-01

As an emerging cavitation technology, photoacoustic cavitation (PAC) means the formation of bubbles in liquids using focused laser and pre-established ultrasound synchronously. Its significant advantages include the decreased threshold of each modality and the precise location of cavitation determined by the focused laser. In this paper, a brief review of PAC is presented, including the physical mechanism description, the classic experimental technology, the representative results in variety of media, and its applications in biomedical imaging and therapy. Moreover, some preliminary results of PAC in perfluoropentane (PFP) liquid and PFP droplets investigated by passive cavitation detection (PCD) in our group are also presented. (paper)

Long-time cavitation threshold of silica water mixture under acoustic drive

Science.gov (United States)

Bussonniére, Adrien; Liu, Qingxia; Tsai, Peichun Amy

2017-11-01

The low cavitation threshold of water observed experimentally has been attributed to the presence of pre-existing tiny bubbles stabilized by impurities. However, the origin and stability of these cavitation nuclei remain unresolved. We therefore investigate the long-time cavitation evolution of water seeded with micron-sized silica particles under the influences of several parameters. Experimentally, cavitation is induced by a High Intensity Focused Ultrasound and subsequently detected by monitoring the backscattered sound. Degassed or aerated solutions of different concentrations are subjected to acoustic pulses (with the amplitude ranging from 0.1 to 1.7 MPa and a fixed repetition frequency between 0.1 and 6.5 Hz). The cavitation threshold was measured by fitting the cavitation probability curve, averaged over 1000 pulses. Surprisingly, our results shown that the cavitation threshold stabilizes at a reproducible value after a few thousand pulses. Moreover, this long-time threshold was found to decrease with increasing particle concentration, pulse period, and initial oxygen level. In contrast to the depletion of nuclei expected under long acoustic cavitation, the results suggest stabilized nuclei population depending on concentration, oxygen level, and driving period.

Transition of cavitating flow to supercavitation within Venturi nozzle – hysteresis investigation

OpenAIRE

Jiří Kozák; Pavel Rudolf; Rostislav Huzlík; Martin Hudec; Radomír Chovanec; Ondřej Urban; Blahoslav Maršálek; Eliška Maršálková; František Pochylý; David Štefan

2017-01-01

Cavitation is usually considered as undesirable phenomena. On the other hand, it can be utilized in many applications. One of the technical applications is using cavitation in water treatment, where hydrodynamic cavitation seems to be effective way how to reduce cyanobacteria within large bulks of water. The main scope of this paper is investigation of the cavitation within Venturi nozzle during the transition from fully developed cavitation to supercavitation regime and vice versa. Dynamics ...

Prediction of incipient flow boiling from a uniformly heated surface

International Nuclear Information System (INIS)

Yin, S.T.; Abdelmessih, A.H.

1977-01-01

This study was undertaken to investigate the phenomenon of liquid superheat during incipient boiling in a uniformly heated forced convection channel. Experimental data were obtained using Freon 11 as the test medium. Based on existing theories, an analytical method was developed for predicting the point of termination of nucleate boiling, observed during a decreasing heat flux process with a nucleation activated surface. The method may also be used to predict the point of boiling incipience, observed during an increasing heat flux process with a non-activated surface; this point does not appear to have been treated analytically in previous work. It can be shown that some of the existing models are special cases of the present formulation

Effect of cavitation in high-pressure direct injection

Science.gov (United States)

Aboulhasanzadeh, Bahman; Johnsen, Eric

2015-11-01

As we move toward higher pressures for Gasoline Direct Injection and Diesel Direct Injection, cavitation has become an important issue. To better understand the effect of cavitation on the nozzle flow and primary atomization, we use a high-order accurate Discontinuous Galerkin approach using multi-GPU parallelism to simulate the compressible flow inside and outside the nozzle. Phase change is included using the six-equations model. We investigate the effect of nozzle geometry on cavitation inside the injector and on primary atomization outside the nozzle.

Ultrasound-induced inertial cavitation from gas-stabilizing nanoparticles.

Science.gov (United States)

Kwan, J J; Graham, S; Myers, R; Carlisle, R; Stride, E; Coussios, C C

2015-08-01

The understanding of cavitation from nanoparticles has been hindered by the inability to control nanobubble size. We present a method to manufacture nanoparticles with a tunable single hemispherical depression (nanocups) of mean diameter 90, 260, or 650 nm entrapping a nanobubble. A modified Rayleigh-Plesset crevice model predicts the inertial cavitation threshold as a function of cavity size and frequency, and is verified experimentally. The ability to tune cavitation nanonuclei and predict their behavior will be useful for applications ranging from cancer therapy to ultrasonic cleaning.

Background nuclei measurements and implications for cavitation inception in hydrodynamic test facilities

Science.gov (United States)

Venning, J. A.; Khoo, M. T.; Pearce, B. W.; Brandner, P. A.

2018-04-01

Water susceptibility and background nuclei content in a water tunnel are investigated using a cavitation susceptibility meter. The measured cumulative histogram of nuclei concentration against critical pressure shows a power law dependence over a large range of concentrations and pressures. These results show that the water strength is not characterised by a single tension but is susceptible to `all' tensions depending on the relevant timescale. This background nuclei population is invariant to tunnel conditions showing that it is stabilised against dissolution. Consideration of a practical cavitating flow about a sphere shows that although background nuclei may be activated, their numbers are so few compared with other sources that they are insignificant for this case.

Cavitation erosion behavior of Hastelloy C-276 nickel-based alloy

Energy Technology Data Exchange (ETDEWEB)

Li, Zhen [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100039 (China); Han, Jiesheng; Lu, Jinjun [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Chen, Jianmin, E-mail: chenjm@lzb.ac.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2015-01-15

Highlights: • Cavitation erosion behavior of Hastelloy C-276 was studied by ultrasonic apparatus. • The cavitation-induced precipitates formed in the eroded surface for Hastelloy C-276. • The selective cavitation erosion was found in Hastelloy C-276 alloy. - Abstract: The cavitation erosion behavior of Hastelloy C-276 alloy was investigated using an ultrasonic vibratory apparatus and compared with that of 316L stainless steel. The mean depth of erosion (MDE) and erosion rate (ER) curves vs. test time were attained for Hastelloy C-276 alloy. Morphology and microstructure evolution of the eroded surface were observed by scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) and the predominant erosion mechanism was also discussed. The results show that the MDE is about 1/6 times lower than that of the stainless steel after 9 h of testing. The incubation period of Hastelloy C-276 alloy is about 3 times longer than that of 316L stainless steel. The cavitation-induced nanometer-scaled precipitates were found in the local zones of the eroded surface for Hastelloy C-276. The selective cavitation erosion was found in Hastelloy C-276 alloy. The formation of nanometer-scaled precipitates in the eroded surface may play a significant role in the cavitation erosion resistance of Hastelloy C-276.

Cavitation erosion behavior of Hastelloy C-276 nickel-based alloy

International Nuclear Information System (INIS)

Li, Zhen; Han, Jiesheng; Lu, Jinjun; Chen, Jianmin

2015-01-01

Highlights: • Cavitation erosion behavior of Hastelloy C-276 was studied by ultrasonic apparatus. • The cavitation-induced precipitates formed in the eroded surface for Hastelloy C-276. • The selective cavitation erosion was found in Hastelloy C-276 alloy. - Abstract: The cavitation erosion behavior of Hastelloy C-276 alloy was investigated using an ultrasonic vibratory apparatus and compared with that of 316L stainless steel. The mean depth of erosion (MDE) and erosion rate (ER) curves vs. test time were attained for Hastelloy C-276 alloy. Morphology and microstructure evolution of the eroded surface were observed by scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) and the predominant erosion mechanism was also discussed. The results show that the MDE is about 1/6 times lower than that of the stainless steel after 9 h of testing. The incubation period of Hastelloy C-276 alloy is about 3 times longer than that of 316L stainless steel. The cavitation-induced nanometer-scaled precipitates were found in the local zones of the eroded surface for Hastelloy C-276. The selective cavitation erosion was found in Hastelloy C-276 alloy. The formation of nanometer-scaled precipitates in the eroded surface may play a significant role in the cavitation erosion resistance of Hastelloy C-276

Characterization of acoustic cavitation in water and molten aluminum alloy.

Science.gov (United States)

Komarov, Sergey; Oda, Kazuhiro; Ishiwata, Yasuo; Dezhkunov, Nikolay

2013-03-01

High-intensive ultrasonic vibrations have been recognized as an attractive tool for refining the grain structure of metals in casting technology. However, the practical application of ultrasonics in this area remains rather limited. One of the reasons is a lack of data needed to optimize the ultrasonic treatment conditions, particularly those concerning characteristics of cavitation zone in molten aluminum. The main aim of the present study was to investigate the intensity and spectral characteristics of cavitation noise generated during radiation of ultrasonic waves into water and molten aluminum alloys, and to establish a measure for evaluating the cavitation intensity. The measurements were performed by using a high temperature cavitometer capable of measuring the level of cavitation noise within five frequency bands from 0.01 to 10MHz. The effect of cavitation treatment was verified by applying high-intense ultrasonic vibrations to a DC caster to refine the primary silicon grains of a model Al-17Si alloy. It was found that the level of high frequency noise components is the most adequate parameter for evaluating the cavitation intensity. Based on this finding, it was concluded that implosions of cavitation bubbles play a decisive role in refinement of the alloy structure. Copyright © 2012 Elsevier B.V. All rights reserved.

Cavitation problems in mixing devices of SNR-300 fuel elements

International Nuclear Information System (INIS)

Benemann, A.

1976-01-01

Because of a complex flow path within the mixing device developed for the fuel elements of the SNR-300, in order to determine the minimum allowable interval to the beginning of cavitation, experimental tests with the original geometry are necessary. These conclusions show that for cavitation values CV>=1,3 - in the model and prototype - no cavitation zones can form. For reactor conditions a maximum velocity of Vsub(max)=4,7m/sec is therefore allowable in the free annular space of the compensator unit which corresponds to a massflow of M=22,5kg/sec. A cavitation value of CV=1,5 can be figured for the 120% load factor (M=20,4kg/sec,T=560 0 C). The mixing device developed is free of cavitation under the present conditions in the SNR-300. The condition of the fully developed cavitation is evidenced by a white noise with frequencies of at least 2.000 - 300.000cps and a signal/noise ratio S/R>40dB. The pressure amplitudes dependent on frequency are propagated in the streaming fluid and are severely damped by the locally existing two-phase flow. The unstable range at the beginning of cavitation is characterized by frequencies of about f=15.000cps

Influence of fluid viscosity on vortex cavitation at a suction pipe inlet

International Nuclear Information System (INIS)

Ezure, Toshiki; Ito, Kei; Kamide, Hideki; Kameyama, Yuri; Kunugi, Tomoaki

2016-01-01

Cavitation is a highly important issue in various fluid machineries. In the design of an advanced loop-type sodium-cooled fast reactor in Japan, vortex cavitation is also a significant issue for the integrity of the reactor structure. Thus, an evaluation method for vortex cavitation is required. In this study, vortex cavitation at a single suction pipe inlet was studied under several different viscosity conditions including its transient behavior. The intermittent occurrence behaviors of vortex cavitation were grasped by visualization measurements. The experimental results showed that the influence of the kinematic viscosity was obvious under a high kinematic viscosity. However, the influence became smaller with decreasing kinematic viscosity. From these results, the non-dimensional circulation, which was defined as the ratio of the local circulation to the kinematic viscosity, was deduced as an evaluation parameter to estimate the influence of the kinematic viscosity. Cavitation factors at transition points from continuous occurrence to intermittent occurrences were also evaluated as representative points where vortex cavitation occurs. Then, the occurrences of vortex cavitation were expressed as a relation between the cavitation factor at transition points and the non-dimensional circulation. As a result, it was clarified that the cavitation factor at transition points increased linearly in relatively small non-dimensional circulation, while it was nearly constant in relatively large non-dimensional circulation. (author)

Real-Time Two-Dimensional Imaging of Microbubble Cavitation

NARCIS (Netherlands)

Vignon, F.; Shi, W.T.; Powers, J.E.; Liu, J.; Drvol, L.; Lof, J.; Everbach, C.; Gao, S.; Xie, F.; Porter, T.

2011-01-01

Ultrasound cavitation of microbubble contrast agents has a potentialfor therapeutic applications, including sonothrombolysis in acute ischemic stroke. For safety, efficacy, and reproducibility of treatment, it is critical to evaluate the cavitation state (e.g. stable versus inertial forms of

Study on Effects of The Shape of Cavitator on Supercavitation Flow Field Characteristics

Science.gov (United States)

Wang, Rui; Dang, Jianjun; Yao, Zhong

2018-03-01

The cavitator is the key part of the nose of the vehicle to induce the formation of supercavity, which has an important influence in the cavity formation rate, cavity shape and cavity stability. To study the influence of the shape on the supercavitation flew field characteristics, the cavity characteristics and the resistance characteristics of different shapes of cavitator under different working conditions are obtained by combining technical methods of numerical simulation and experimental research in water tunnel. The simulation results are contrast and analyzed with the test results. The analysis results show that : in terms of the cavity size, the inverted-conic cavitator can form the biggest cavity size, followed by the disk cavitator, and the truncated-conic cavitator is the least; in terms of the cavity formation speed, the inverted-conic cavitator has the fastest cavity formation speed, then is the truncated-conic cavitator, and the disk cavitator is the least; in terms of the drag characteristic, the truncated-conic cavitator has the maximum coefficient, disk cavitator is the next, the inverted-conic cavitator is the minimal. The research conclusion can provide reference and basis for the head shape design of supercavitating underwater ordnance and the design of hydrodynamic layout.

Large eddy simulation of cavitating flows

Science.gov (United States)

Gnanaskandan, Aswin; Mahesh, Krishnan

2014-11-01

Large eddy simulation on unstructured grids is used to study hydrodynamic cavitation. The multiphase medium is represented using a homogeneous equilibrium model that assumes thermal equilibrium between the liquid and the vapor phase. Surface tension effects are ignored and the governing equations are the compressible Navier Stokes equations for the liquid/vapor mixture along with a transport equation for the vapor mass fraction. A characteristic-based filtering scheme is developed to handle shocks and material discontinuities in non-ideal gases and mixtures. A TVD filter is applied as a corrector step in a predictor-corrector approach with the predictor scheme being non-dissipative and symmetric. The method is validated for canonical one dimensional flows and leading edge cavitation over a hydrofoil, and applied to study sheet to cloud cavitation over a wedge. This work is supported by the Office of Naval Research.

PIV in the two phases of hydrodynamic cavitation in a venturi type section

Science.gov (United States)

Fuzier, Sylvie; Coudert, Sébastien; Coutier Delgosha, Olivier

2012-11-01

The presence of cavitation can affect the performance of turbomachinery. Attached sheet cavities on the blades induce modifications of flow dynamics and turbulence properties. This phenomenon is studied here in a configuration of 2D flow in a venturi type section. Images of the bubbles as well as of the light emitted by fluorescent particles placed in the liquid are recorded simultaneously. Velocities of the bubbles and of the liquid phase are obtained by PIV. The slip velocity is analyzed function of the number of cavitation and other physical parameters. Different levels of turbulence are correlated with different bubble structures in the dipahasic cavity.

Statistical characteristics of mechanical heart valve cavitation in accelerated testing.

Science.gov (United States)

Wu, Changfu; Hwang, Ned H C; Lin, Yu-Kweng M

2004-07-01

Cavitation damage has been observed on mechanical heart valves (MHVs) undergoing accelerated testing. Cavitation itself can be modeled as a stochastic process, as it varies from beat to beat of the testing machine. This in-vitro study was undertaken to investigate the statistical characteristics of MHV cavitation. A 25-mm St. Jude Medical bileaflet MHV (SJM 25) was tested in an accelerated tester at various pulse rates, ranging from 300 to 1,000 bpm, with stepwise increments of 100 bpm. A miniature pressure transducer was placed near a leaflet tip on the inflow side of the valve, to monitor regional transient pressure fluctuations at instants of valve closure. The pressure trace associated with each beat was passed through a 70 kHz high-pass digital filter to extract the high-frequency oscillation (HFO) components resulting from the collapse of cavitation bubbles. Three intensity-related measures were calculated for each HFO burst: its time span; its local root-mean-square (LRMS) value; and the area enveloped by the absolute value of the HFO pressure trace and the time axis, referred to as cavitation impulse. These were treated as stochastic processes, of which the first-order probability density functions (PDFs) were estimated for each test rate. Both the LRMS value and cavitation impulse were log-normal distributed, and the time span was normal distributed. These distribution laws were consistent at different test rates. The present investigation was directed at understanding MHV cavitation as a stochastic process. The results provide a basis for establishing further the statistical relationship between cavitation intensity and time-evolving cavitation damage on MHV surfaces. These data are required to assess and compare the performance of MHVs of different designs.

Nondestructive evaluation of incipient decay in hardwood logs

Science.gov (United States)

Xiping Wang; Jan Wiedenbeck; Robert J. Ross; John W. Forsman; John R. Erickson; Crystal Pilon; Brian K. Brashaw

2005-01-01

Decay can cause significant damage to high-value hardwood timber. New nondestructive evaluation (NDE) technologies are urgently needed to effectively detect incipient decay in hardwood timber at the earliest possible stage. Currently, the primary means of inspecting timber relies on visual assessment criteria. When visual inspections are used exclusively, they provide...

Control of superplastic cavitation by hydrostatic pressure

International Nuclear Information System (INIS)

Bampton, C.C.; Ghosh, A.K.; Hamilton, C.H.; Mahoney, M.W.; Raj, R.

1983-01-01

It has been shown that the application of hydrostatic gas pressures during superplastic deformation of fine grained 7475 Al can prevent the intergranular cavitation normally encountered at atmospheric pressure. A critical ratio of hydrostatic pressure to flow stress may be defined for each superplastic forming condition above which virtually no cavitation occurs. In deformation conditions where intergranular cavitation plays a significant part in final tensile rupture, superplastic ductility may be improved by the application of hydrostatic pressures. Similarly, detrimental effects of large superplastic strains on service properties may be reduced or eliminated by the application of suitable hydrostatic pressures during superplastic forming. In this case, superplastically formed material may have the same design allowables as conventional 7475 Al sheet

Computation and analysis of cavitating flow in Francis-class hydraulic turbines

Science.gov (United States)

Leonard, Daniel J.

Hydropower is the most proven renewable energy technology, supplying the world with 16% of its electricity. Conventional hydropower generates a vast majority of that percentage. Although a mature technology, hydroelectric generation shows great promise for expansion through new dams and plants in developing hydro countries. Moreover, in developed hydro countries, such as the United States, installing generating units in existing dams and the modern refurbishment of existing plants can greatly expand generating capabilities with little to no further impact on the environment. In addition, modern computational technology and fluid dynamics expertise has led to substantial improvements in modern turbine design and performance. Cavitation has always presented a problem in hydroturbines, causing performance breakdown, erosion, damage, vibration, and noise. While modern turbines are usually designed to be cavitation-free at their best efficiency point, due to the variable demand of the energy market it is fairly common to operate at off-design conditions. Here, cavitation and its deleterious effects are unavoidable, and hence, cavitation is a limiting factor on the design and operation of these turbines. Multiphase Computational Fluid Dynamics (CFD) has been used in recent years to model cavitating flow for a large range of problems, including turbomachinery. However, CFD of cavitating flow in hydroturbines is still in its infancy. This dissertation presents steady-periodic Reynolds-averaged Navier-Stokes simulations of a cavitating Francis-class hydroturbine at model and prototype scales. Computational results of the reduced-scale model and full-scale prototype, undergoing performance breakdown, are compared with empirical model data and prototype performance estimations based on standard industry scalings from the model data. Mesh convergence of the simulations is also displayed. Comparisons are made between the scales to display that cavitation performance breakdown

Comparison of cavitation bubbles evolution in viscous media

Directory of Open Access Journals (Sweden)

Jasikova Darina

2018-01-01

Full Text Available There have been tried many types of liquids with different ranges of viscosity values that have been tested to form a single cavitation bubble. The purpose of these experiments was to observe the behaviour of cavitation bubbles in media with different ranges of absorbance. The most of the method was based on spark to induced superheat limit of liquid. Here we used arrangement of the laser-induced breakdown (LIB method. There were described the set cavitation setting that affects the size bubble in media with different absorbance. We visualized the cavitation bubble with a 60 kHz high speed camera. We used here shadowgraphy setup for the bubble visualization. There were observed time development and bubble extinction in various media, where the size of the bubble in the silicone oil was extremely small, due to the absorbance size of silicon oil.

Transition of cavitating flow to supercavitation within Venturi nozzle – hysteresis investigation

Directory of Open Access Journals (Sweden)

Jiří Kozák

2017-01-01

Full Text Available Cavitation is usually considered as undesirable phenomena. On the other hand, it can be utilized in many applications. One of the technical applications is using cavitation in water treatment, where hydrodynamic cavitation seems to be effective way how to reduce cyanobacteria within large bulks of water. The main scope of this paper is investigation of the cavitation within Venturi nozzle during the transition from fully developed cavitation to supercavitation regime and vice versa. Dynamics of cavitation was investigated using experimental data of pressure pulsations and analysis of high speed videos, where FFT of the pixel intensity and Proper Orthogonal Decomposition (POD of the records were done to identify dominant frequencies connected with the presence of cavitation. The methodology of the high speed (HS records semiautomated analysis using the FFT was described. Obtained results were correlated and above that the possible presence of hysteresis was discussed.

Characterization and modification of cavitation pattern in shock wave lithotripsy

Science.gov (United States)

Arora, Manish; Ohl, Claus Dieter; Liebler, Marko

2004-01-01

The temporal and spatial dynamics of cavitation bubble cloud growth and collapse in extracorporeal shock wave lithotripsy (ESWL) is studied experimentally. The first objective is obtaining reproducible cloud patterns experimentally and comparing them with FDTD-calculations. Second, we describe a method to modify the cavitation pattern by timing two consecutive pressure waves at variable delays. It is found that the spatial and temporal dynamics of the cavitation bubble can be varied in large ranges. The ability to control cavitation dynamics allows discussing strategies for improvement of medical and biological applications of shock waves such as cell membrane poration and stone fragmentation.

Cold fusion reaction ignition at cavitation effect on deuterium-containing media

International Nuclear Information System (INIS)

Lipson, A.G.; Deryagin, B.V.; Klyuev, V.A.

1992-01-01

A possibility to induce 'cold' nuclear fusion reactions in the process of ultrasound cavitation in heavy water is studied. Nonstationary neutron emission is detected under cavitation in D 2 O on titanium vibrator which has the tracks of cavitation erosion (the vibrator ran in D 2 O to 20 hours). Maximum excess over background (12σ) was recorded under cavitation impact on the suspension of LaNi 5 D x dispersed particle in D 2 O

Theoretical model for cavitation erosion prediction in centrifugal pump impeller

International Nuclear Information System (INIS)

Rayan, M.A.; Mahgob, M.M.; Mostafa, N.H.

1990-01-01

Cavitation is known to have great effects on pump hydraulic and mechanical characteristics. These effects are mainly described by deviation in pump performance, increasing vibration and noise level as well as erosion of blade and casing materials. In the present work, only the hydrodynamic aspect of cavitation was considered. The efforts were directed toward the study of cavitation inception, cavity mechanics and material erosion in order to clarify the macrohydrodynamic aspects of cavitation erosive wear in real machines. As a result of this study, it was found that cavitation damage can be predicted from model data. The obtained theoretical results show good agreement with the experimental results obtained in this investigation and with results of some other investigations. The application of the findings of this work will help the design engineer in predicting the erosion rate, according to the different operating conditions. (author)

Excitation of cavitation bubbles in low-temperature liquid nitrogen

Science.gov (United States)

Sasaki, Koichi; Harada, Shingo

2017-06-01

We excited a cavitation bubble by irradiating a Nd:YAG laser pulse onto a titanium target that was installed in liquid nitrogen at a temperature below the boiling point. To our knowledge, this is the first experiment in which a cavitation bubble has been successfully excited in liquid nitrogen. We compared the cavitation bubble in liquid nitrogen with that in water on the basis of an equation reported by Florschuetz and Chao [J. Heat Transfer 87, 209 (1965)].

Observations and Measurements on Unsteady Cloud Cavitation Flow Structures

International Nuclear Information System (INIS)

Gu, L X; Yan, G J; Huang, B

2015-01-01

The objectives of this paper are to investigate the unsteady structures and hydrodynamics of cavitating flows. Experimental results are presented for a Clark-Y hydrofoil, which is fixed at α=0°, 5° and 8°. The high-speed video camera and Particle Image Velocimetry (PIV) are applied to investigate the transient flow structures. The dynamic measurement system is used to record the dynamic characteristics. The cloud cavitation exhibits noticeable unsteady characteristics. For the case of α=0°, there exit strong interactions between the attached cavity and the re-entrant flow. While for the case of α=8°, the re-entrant flow is relatively thin and the interaction between the cavity and re-entrant flow is limited. The results also present that the periodic collapse and shedding of the large-scale cloud cavitation, which leads to substantial increase of turbulent velocity fluctuations in the cavity region. Experimental evidence indicates that the hydrodynamics are clearly affected by the cavitating flow structures, the amplitude of load fluctuation are much higher for the cloud cavitating cases. (paper)

Observations and Measurements on Unsteady Cloud Cavitation Flow Structures

Science.gov (United States)

Gu, L. X.; Yan, G. J.; Huang, B.

2015-12-01

The objectives of this paper are to investigate the unsteady structures and hydrodynamics of cavitating flows. Experimental results are presented for a Clark-Y hydrofoil, which is fixed at α=0°, 5° and 8°. The high-speed video camera and Particle Image Velocimetry (PIV) are applied to investigate the transient flow structures. The dynamic measurement system is used to record the dynamic characteristics. The cloud cavitation exhibits noticeable unsteady characteristics. For the case of α=0°, there exit strong interactions between the attached cavity and the re-entrant flow. While for the case of α=8°, the re-entrant flow is relatively thin and the interaction between the cavity and re-entrant flow is limited. The results also present that the periodic collapse and shedding of the large-scale cloud cavitation, which leads to substantial increase of turbulent velocity fluctuations in the cavity region. Experimental evidence indicates that the hydrodynamics are clearly affected by the cavitating flow structures, the amplitude of load fluctuation are much higher for the cloud cavitating cases.

Cavitation research from an intetrnational perspective

International Nuclear Information System (INIS)

Arndt, R E A

2012-01-01

This paper reviews some current research at the Saint Anthony Falls Laboratory from the perspective of the experience gained from cooperative research in other laboratories that the author has had the opportunity to participate in for several decades. Examples are drawn from the author's experience with collaborative efforts in China, Germany, Japan, Netherlands, Norway, and the US. Emphasis is placed on the progress in our understanding of the physics of cavitation as influenced by water quality, i.e. the strength of the water as influenced by the concentration of free and dissolved gas and complex fluid dynamic factors such as turbulence. The shift from experimental research to studies involving an integrated experimental/numerical approach is also underscored. Examples are drawn from early studies of inception and acoustics, vortex cavitation and more recent research on sheet/cloud cavitation and supercavitation. Some thoughts on new directions are also presented.

Influence of microparticle size on cavitation noise during ultrasonic vibration

Directory of Open Access Journals (Sweden)

H. Ge

2015-09-01

Full Text Available The cavitation noise in the ultrasonic vibration system was found to be influenced by the size of microparticles added in water. The SiO2 microparticles with the diameter smaller than 100 μm reduced the cavitation noise, and the reason was attributed to the constrained oscillation of the cavitation bubbles, which were stabilized by the microparticles.

Cavitation in holographic sQGP

Energy Technology Data Exchange (ETDEWEB)

Klimek, Aleksandra [Department of Physics, University of Warsaw (Poland); Leblond, Louis [Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada); Sinha, Aninda, E-mail: asinha@cts.iisc.ernet.in [Centre for High Energy Physics, Indian Institute of Science, C.V. Raman Avenue, Bangalore 560012 (India)

2011-06-27

We study the possibility of cavitation in the non-conformal N=2{sup *}SU(N) theory which is a mass deformation of N=4SU(N) Yang-Mills theory. The second order transport coefficients are known from the numerical work using AdS/CFT by Buchel and collaborators. Using these and the approach of Rajagopal and Tripuraneni, we investigate the flow equations in a (1+1)-dimensional boost invariant set up. We find that the string theory model does not exhibit cavitation before phase transition is reached. We give a semi-analytic explanation of this finding.

Numerical investigation on cavitation in pressure relief valve for coal liquefaction

International Nuclear Information System (INIS)

Ou, G F; Li, W Z; Xiao, D H; Zheng, Z J; Dou, H S; Wang, C

2015-01-01

The pressure relief valve for regulating the level of the high-pressure separator works under a pressure difference up to 15 MPa in the temperature of 415 °C. Severe cavitation erosion and particle impact lead to the valve disc's mass loss. In this paper, three-dimensional turbulent cavitating flows in the pressure relief valve are numerically simulated to reveal the mechanism of mass loss at valve disc. The RNG k-ε turbulence model and the mixture model with a mass transfer for cavitation are employed to simulate the cavitating flow in the pressure relief valve. The result shows that there is phase change in the pressure relief process and cavitation bubbles would be transported by high-velocity backflow to the head of valve disc. For the local pressure higher than the saturated vapor pressure, the bubbles collapse at the head of disc and cavitation erosion is formed at the head of the disc. By comparing the cases of opening of 40%, 50%, and 60%, backflow velocity and cavitation region in front of the disc decrease with the opening increase. Therefore, during the actual operation, the pressure relief valve should be kept to a relatively large opening

Mechanisms of mechanical heart valve cavitation: investigation using a tilting disk valve model.

Science.gov (United States)

He, Z; Xi, B; Zhu, K; Hwang, N H

2001-09-01

The induction of mechanical heart valve (MHV) cavitation was investigated using a 27 mm Medtronic Hall (MH27) tilting disk valve. The MH27 valve was mounted in the mitral position of a simulating pulse flow system, and stroboscopic lighting used to visualize cavitation bubbles on the occluder inflow surface at the instant of valve closure. MHV cavitation was monitored using a digital camera with 0.04 mm/pixel resolution sufficient to render the tiny bubbles clearly visible on the computer monitor screen. Cavitation on MH27 valve was classified as five types according to the time, site and shape of the cavitation bubbles. Valve cavitation occurred at the instant of occluder impact with the valve seat at closing. The impact motion was subdivided into three temporal phases: (i) squeezing flow; (ii) elastic collision; and (iii) leaflet rebound. MHV cavitation caused by vortices was found to be initiated by the squeezing jet and/or by the transvalvular leakage jets. By using a tension wave which swept across the occluder surface immediately upon elastic impact, nuclei in the vortex core were expanded to form cavitation bubbles. Analysis of the shape and location of the cavitation bubbles permitted a better understanding of MHV cavitation mechanisms, based on the fluid dynamics of jet vortex and tension wave propagations.

Recent developments in cavitation mechanisms a guide for scientists and engineers

CERN Document Server

Washio, Seiichi

2014-01-01

How does cavitation start? Presently, the nucleus theory provides the answer to this fundamental question. However the idea of nuclei contains inaccuracies that cannot be rationalized. Recent Developments in Cavitation Mechanisms discusses the uncertainties surrounding the nucleus theory, and proposes another theory of cavitation mechanism. Characteristically, the new theory is based on recent discoveries of cavity generation phenomena in separating flows. This book consists of chapters that introduce topics such as unsoundness of cavitation nuclei, and phenomena of cavity generation on walls

Pump cavitation and inducer design

International Nuclear Information System (INIS)

Heslenfeld, M.W.; Hes, M. de

2002-01-01

Details of past work on sodium pump development and cavitation studies executed mainly for SNR 300 were reported earlier. Among the requirements for large sodium pumps are long life (200000 hours up to 300000 hours) and small size of impeller and pump, fully meeting the process and design criteria. These criteria are the required 'Q, H, r characteristics' in combination with a low NPSH value and the avoidance of cavitation damage to the pump. The pump designer has to develop a sound hydraulic combination consisting of suction arrangement, impeller design and diffuser. On the other hand the designer is free to choose an optimal pump speed. The pump speed in its turn influences the rotor dynamic pump design and the pump drive. The introduction of the inducer as an integral part of the pump design is based on following advantages: no tip cavitation; (possible) cavitation bubbles move to the open centre due to centrifugal forces on the fluid; the head of the inducer improves the inlet conditions of the impeller. The aim of an inducer is the increase in the suction specific speed (SA value) of a pump whereby the inducer functions as a pressure source improving the impeller inlet conditions. With inducer-impeller combinations values up to SA=15000 are realistic. With the use of an inducer the overall pump sizes can be reduced with Ca. 30%. Pumps commonly available have SA values up to a maximum of ca. 10000. A development programme was executed for SNR 300 in order to reach an increase of the suction specific speed of the impeller from SA 8200 to SA 11000. Further studies to optimize pumps design for the follow up line introduced the 'inducer acting as a pre-impeller' development. This programme was executed in the period 1979-1981. At the FDO premises a scale 1 2.8 inducer impeller combination with a suction specific speed SA=15000 was developed, constructed and tested at the water test rig. This water test rig is equipped with a perspex pipe allowing also visualisation

Study on unsteady tip leakage vortex cavitation in an axial-flow pump using an improved filter-based model

Energy Technology Data Exchange (ETDEWEB)

Zhang, Desheng; Shi, Lei; Zhao, Ruijie; Shi, Weidong; Pan, Qiang [Jiangsu University, Zhenjiang (China); Esch, B. P. [Eindhoven University of Technology, Eindhoven (Netherlands)

2017-02-15

The aim of the present investigation is to simulate and analyze the tip leakage flow structure and instantaneous evolution of tip vortex cavitation in a scaled axial-flow pump model. The improved filter-based turbulence model based on the density correction and a homogeneous cavitation model were used for implementing this work. The results show that when entering into the tip clearance, the backward flow separates from the blade tip near the pressure side, resulting in the generation of a corner vortex with high magnitude of turbulence kinetic energy. Then, at the exit of the tip clearance, the leakage jets would re-attach on the blade tip wall. Moreover, the maximum swirling strength method was employed in identifying the TLV core and a counter-rotating induced vortex near the end-wall successfully. The three dimensional cavitation patterns and in-plain cavitation structures obtained by the improved numerical method agree well with the experimental results. At the sheet cavitation trailing edge in the tip region, the perpendicular cavitation cloud induced by TLV sheds and migrates toward the pressure side of the neighboring blade. During its migration, it breaks down abruptly and generates a large number of smallscale cavities, leading to severe degradation of the pump performance, which is similar with the phenomenon observed by Tan et al.

Numerical analysis of the effects of radiation heat transfer and ionization energy loss on the cavitation Bubble's dynamics

International Nuclear Information System (INIS)

Mahdi, M.; Ebrahimi, R.; Shams, M.

2011-01-01

A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with the experimental data and a good correspondence was observed. The dynamics of hydrofoil cavitation bubble were also investigated. It was concluded that the thermal radiation heat transfer rate strongly depended on the cavitation number, initial bubble radius and hydrofoil angle of attack. -- Highlights: → Heat transfer and ionization energy losses were analyzed in the cavitation bubble. → Radiation of hydrodynamic bubble was approximately equal to the black body. → Radiation heat transfer did not affect the bubble dynamic. → Conduction decreased the bubble pressure and increased the bubble temperature. → Ionization decreased the temperature and increased the pressure in the bubble.

A cavitation model based on Eulerian stochastic fields

Science.gov (United States)

Magagnato, F.; Dumond, J.

2013-12-01

Non-linear phenomena can often be described using probability density functions (pdf) and pdf transport models. Traditionally the simulation of pdf transport requires Monte-Carlo codes based on Lagrangian "particles" or prescribed pdf assumptions including binning techniques. Recently, in the field of combustion, a novel formulation called the stochastic-field method solving pdf transport based on Eulerian fields has been proposed which eliminates the necessity to mix Eulerian and Lagrangian techniques or prescribed pdf assumptions. In the present work, for the first time the stochastic-field method is applied to multi-phase flow and in particular to cavitating flow. To validate the proposed stochastic-field cavitation model, two applications are considered. Firstly, sheet cavitation is simulated in a Venturi-type nozzle. The second application is an innovative fluidic diode which exhibits coolant flashing. Agreement with experimental results is obtained for both applications with a fixed set of model constants. The stochastic-field cavitation model captures the wide range of pdf shapes present at different locations.

Correlation between microbubble-induced acoustic cavitation and hemolysis in vitro

International Nuclear Information System (INIS)

Zhang Chun-Bing; Liu Zheng; Guo Xia-Sheng; Zhang Dong

2011-01-01

Microbubbles promise to enhance the efficiency of ultrasound-mediated drug delivery and gene therapy by taking advantage of artificial cavitation nuclei. The purpose of this study is to examine the ultrasound-induced hemolysis in the application of drug delivery in the presence of microbubbles. To achieve this goal, human red blood cells mixed with microbubbles were exposed to 1-MHz pulsed ultrasound. The hemolysis level was measured by a flow cytometry, and the cavitation dose was detected by a passive cavitation detecting system. The results demonstrate that larger cavitation dose would be generated with the increase of acoustic pressure, which might give rise to the enhancement of hemolysis. Besides the experimental observations, the acoustic pressure dependence of the radial oscillation of microbubble was theoretically estimated. The comparison between the experimental and calculation results indicates that the hemolysis should be highly correlated to the acoustic cavitation. (classical areas of phenomenology)

The making of a cavitation children's book

Science.gov (United States)

Henry de Frahan, Marc; Patterson, Brandon; Lazar, Erika

2016-11-01

Engaging young children in science is particularly important to future scientific endeavors. From thunderstorms to the waterpark, children are constantly exposed to the wonders of fluid dynamics. Among fluid phenomena, bubbles have always fascinated children. Yet some of the most exciting aspects of bubbles, such as cavitation, are scarcely known to non-experts. To introduce cavitation to a five year old audience, we wrote "Brooke Bubble Breaks Things", a children's book about the adventures of a cavitation bubble learning about all the things she could break. In this talk, we discuss how a children's book is made by walking through the steps involved in creating the book from concept to publication. We focus on strategies for successfully communicating a technical message while balancing entertainment and fidelity to nature. To provide parents, teachers, and young inquiring minds with a detailed explanation of the physics and applications of cavitation, we also created a website with detailed explanations, animations, and links to further information. We aim to convince the fluids community that writing picture books is an intellectually stimulating and fun way of communicating fluids principles and applications to children. ArtsEngine Microgrant at the University of Michigan.

Role of cavitation in high-speed droplet impact problems

Science.gov (United States)

Kondo, Tomoki; Ando, Keita

2014-11-01

High-speed droplet impact is found in physical cleaning using liquid jets, but its mechanisms for particle removal from target surfaces are yet unclear. In this study, we explore the possibility of having cavitation inside the droplet. The pressure evolution within a droplet colliding with a flat surface of deformable materials is determined by multicomponent Euler equations. Dynamics of cavitation bubbles heterogeneously nucleated from preexisting nuclei are determined from Rayleigh-Plesset calculations according to the pressure evolution within the droplet in one-way-coupling manner. The simulation shows that cavitation indeed occurs due to tension that arises from the water hammer shock reflection at the droplet interface. The role of cavitation including pressure emission from its collapse is to be discussed based on the one-way-coupling computations.

Localized Tissue Surrogate Deformation due to Controlled Single Bubble Cavitation

Science.gov (United States)

2014-08-27

studies using ultrasound shock waves also support cavitation induced damage, e.g. hemorrhage and cellular membrane poration 26-28. In addition...SECURITY CLASSIFICATION OF: Cavitation -induced shock wave, as might occur in the head during exposure to blast waves, was investigated as a possible...damage mechanism for soft brain tissues. A novel experimental scheme was developed to visualize and control single bubble cavitation and its

A parametrical study of disinfection with hydrodynamic cavitation.

Science.gov (United States)

Arrojo, S; Benito, Y; Tarifa, A Martínez

2008-07-01

The physical and chemical conditions generated by cavitation bubbles can be used to destroy microorganisms and disinfect wastewater. The effect of different cavitation chamber designs and diverse operational parameters on the inactivation rate of Escherichia coli have been studied and used to understand the mechanisms involved in cell disruption.

Cavitational hydrothermal oxidation: A new remediation process. Annual progress report, September 1996 - August 1997

International Nuclear Information System (INIS)

Suslick, K.S.

1997-01-01

'During the past year, the authors have continued to make substantial scientific progress on the understanding of cavitation phenomena in aqueous media and applications of cavitation to remediation processes. The efforts have focused on three separate areas: sonoluminescence as a probe of conditions created during cavitational collapse in aqueous media, the use of cavitation for remediation of contaminated water, and an addition of the use of ultrasound in the synthesis of novel heterogeneous catalysts for hydrodehalogenation of halocarbons under mild conditions. In order to gain further understanding of the conditions present during cavitation, the author has continued his studies of sonoluminescence. He has made recent breakthroughs in the use of emission spectroscopy for temperature and pressure measurement of cavitation events, which he expects to publish shortly. He has been able to measure for the first time the temperature of cavitation in water during multi-bubble cavitation in the presence of aromatic hydrocarbons. The emission from excited states of C 2 in water gives temperatures that are consistent with adiabatic compressional heating, with maximum temperatures of 4,300 K. Prior measurements of cavitation temperatures in low vapor pressure nonaqueous media gave somewhat higher temperatures of 5,000 K. This work lays permanently to rest exotic mechanisms for cavitational chemistry, at least for cavitation fields.'

Computational fluid dynamic modelling of cavitation

Science.gov (United States)

Deshpande, Manish; Feng, Jinzhang; Merkle, Charles L.

1993-01-01

Models in sheet cavitation in cryogenic fluids are developed for use in Euler and Navier-Stokes codes. The models are based upon earlier potential-flow models but enable the cavity inception point, length, and shape to be determined as part of the computation. In the present paper, numerical solutions are compared with experimental measurements for both pressure distribution and cavity length. Comparisons between models are also presented. The CFD model provides a relatively simple modification to an existing code to enable cavitation performance predictions to be included. The analysis also has the added ability of incorporating thermodynamic effects of cryogenic fluids into the analysis. Extensions of the current two-dimensional steady state analysis to three-dimensions and/or time-dependent flows are, in principle, straightforward although geometrical issues become more complicated. Linearized models, however offer promise of providing effective cavitation modeling in three-dimensions. This analysis presents good potential for improved understanding of many phenomena associated with cavity flows.

Cavitation erosion prediction on Francis turbines

Energy Technology Data Exchange (ETDEWEB)

Bourdon, P.; Farhat, M.; Simoneau, R.; Lavigne, P. [Hydro-Quebec, Montreal, PQ (Canada); Pereira, F.; Dupont, P.; Avellan, F.; Caron, J.F. [IMHEF/EPFL, (France); Dorey, J.M.; Archer, A. [Electricite de France (EDF), 92 - Clamart (France). Dir. des Etudes et Recherches; and others

1997-12-31

On-board aggressiveness measurement methods were tested on a severely eroded prototype blade of a 266 MW Francis turbine: pressure, pit counting, DECER electrochemical and vibration measurements. The test program provided understanding of the heterogeneous erosion distribution of the prototype blades and quantitative data for comparison in subsequent tests on the model of the machine. Model tests and flow analysis were also performed, to detect cavitation on a Francis turbine model. The results are compared to those obtained on the prototype measurements. The model used for that study is built on the basis of a geometrical recovery of one of the most eroded blade of the prototype. Different methods were investigated to predict cavitation erosion on Francis turbines from model. They are based on measurement of pitting, pressure fluctuations and acceleration. The methods proposed are suitable to measure cavitation aggressiveness on model and on prototype, and that the level on the model is several orders of magnitude smaller than on the prototype. (author) 18 refs.

Principles and effects of acoustic cavitation - A review

Directory of Open Access Journals (Sweden)

Corina GÂMBUŢEANU

2013-12-01

Full Text Available In the recent years, food industry has shown a real interest in ultrasound use because of its effect on physical, biochemical and microbial properties of food systems. In order to better understand how the acoustic cavity effects could be best applied in food industry, a review on acoustic cavitation and its effects was done. The present paper describes in detail the basic principles underlying the effects of ultrasounds on food processing applications. It also provides theoretical background on acoustic cavitation and ultrasound production method. Moreover, harnessing mechanic, optic, chemical and biological effects of acoustic cavitation in food industry were briefly highlighted.

Efficient inactivation of MS-2 virus in water by hydrodynamic cavitation.

Science.gov (United States)

Kosel, Janez; Gutiérrez-Aguirre, Ion; Rački, Nejc; Dreo, Tanja; Ravnikar, Maja; Dular, Matevž

2017-11-01

The aim of this study was to accurately quantify the impact of hydrodynamic cavitation on the infectivity of bacteriophage MS2, a norovirus surrogate, and to develop a small scale reactor for testing the effect of hydrodynamic cavitation on human enteric viruses, which cannot be easily prepared in large quantities. For this purpose, 3 mL scale and 1 L scale reactors were constructed and tested. Both devices were efficient in generating hydrodynamic cavitation and in reducing the infectivity of MS2 virus. Furthermore, they reached more than 4 logs reductions of viral infectivity, thus confirming the scalability of hydrodynamic cavitation for this particular application. As for the mechanism of page inactivation, we suspect that cavitation generated OH - radicals formed an advanced oxidation process, which could have damaged the host's recognition receptors located on the surface of the bacteriophage. Additional damage could arise from the high shear forces inside the cavity. Moreover, the effectiveness of the cavitation was higher for suspensions containing low initial viral titers that are in similar concentration to the ones found in real water samples. According to this, cavitation generators could prove to be a useful tool for treating virus-contaminated wastewaters in the future. Copyright © 2017 Elsevier Ltd. All rights reserved.

Cavitation Erosion of Cermet-Coated Aluminium Bronzes.

Science.gov (United States)

Mitelea, Ion; Oancă, Octavian; Bordeaşu, Ilare; Crăciunescu, Corneliu M

2016-03-17

The cavitation erosion resistance of CuAl10Ni5Fe2.5Mn1 following plasma spraying with Al₂O₃·30(Ni 20 Al) powder and laser re-melting was analyzed in view of possible improvements of the lifetime of components used in hydraulic environments. The cavitation erosion resistance was substantially improved compared with the one of the base material. The thickness of the re-melted layer was in the range of several hundred micrometers, with a surface microhardness increasing from 250 to 420 HV 0.2. Compositional, structural, and microstructural explorations showed that the microstructure of the re-melted and homogenized layer, consisting of a cubic Al₂O₃ matrix with dispersed Ni-based solid solution is associated with the hardness increase and consequently with the improvement of the cavitation erosion resistance.

Observations of the Dynamics and Acoustics of Travelling Bubble Cavitation

Science.gov (United States)

1990-06-25

Bubbles 6.1 Introduction The detailed relationship between the collapse mechanism of hydrodynamic cavitation bubbles and the resulting noise generation is...Contribution to 11th International Towing Tank Conference. Il’ichev, V. I. 1968. Statistical Model of the Onset of Hydrodynamic Cavitation Noise. Soviet...On the Theory of Hydrodynamic Cavitation Noise. Soviet Physics-Acoustics, Vol. 15, pp. 494-498. Marboe, M. L., Billet, M. L. and Thompson, D. E. 1986

Cavitational synthesis of nanostructured inorganic materials for enhanced heterogeneous catalysis

Science.gov (United States)

Krausz, Ivo Michael

The synthesis of nanostructured inorganic materials by hydrodynamic cavitation processing was investigated. The goal of this work was to develop a general synthesis technique for nanostructured materials with a control over crystallite size in the 1--20 nm range. Materials with crystallite sizes in this range have shown enhanced catalytic activity compared to materials with larger crystallite sizes. Several supported and unsupported inorganic materials were studied to understand the effects of cavitation on crystallite size. Cavitation processing of calcium fluoride resulted in more spherical particles, attached to one another by melted necks. This work produced the first evidence of shock wave heating of nanostructured materials by hydrodynamic cavitation processing. Hydrodynamic cavitation synthesis of various catalytic support materials indicated that their phase composition and purity could be controlled by adjustment of the processing parameters. Zirconia/alumina supports synthesized using hydro-dynamic cavitation and calcined to 1368 K retained a high purity cubic zirconia phase, whereas classically prepared samples showed a phase transformation to monoclinic zirconia. Similarly, the synthesis of alumina resulted in materials with varying Bohmite and Bayerite contents as a function of the process parameters. High temperature calcination resulted in stable alumina supports with varying amounts of delta-, and theta-alumina. Synthesis studies of palladium and silver showed modest variations in crystallite size as a function of cavitation process parameters. Calcination resulted in larger grain materials, indicating a disappearance of intergrain boundaries. Based on these results, a new synthesis method was studied involving controlled agglomeration of small silver crystallites by hydrodynamic cavitation processing, followed by deposition on alumina. The optimal pH, concentration, and processing time for controlling the silver crystallite size in the cavitation

Numerical investigations on cavitating flows with thermodynamic effects in a diffuser-type centrifugal pump

International Nuclear Information System (INIS)

Xuelin, Tang Xue; Liyuan, Bian; Fujun, Wang; Xiaoqin, Lin; Man, Hao

2013-01-01

A cavitation model with thermodynamic effects for cavitating flows in a diffuser-type centrifugal pump is developed based on the bubble two-phase flow model. The proposed cavitation model includes mass, momentum, and energy transportations according to the thermodynamic mechanism of cavitation. Numerical simulations are conducted inside the entire passage of the centrifugal pump by using the proposed cavitation model and the renormalization group-based k - ε turbulent model coupled with the energy transportation equation. By using the commercial computational fluid dynamics software FLUENT 6.3, we have shown that the predicted performance characteristics of the pump, as well as the pressure, vapor, and density distributions in the impeller, agree well with that calculated by the full cavitation model. Simulation results show that cavitation initially occurs slightly behind the inlet of the blade suction surface, i.e., the area with maximum vapor concentration and minimum pressure. The predicted temperature field shows that the reduction in temperature restrains the growth of cavitating bubbles. Therefore, the thermodynamic effect should be treated as a necessary factor in cavitation models. Comparison results validate the efficiency and accuracy of the numerical technique in simulating cavitation flows in centrifugal pumps.

Numerical investigation of cavitation flow in journal bearing geometry

Science.gov (United States)

Riedel, M.; Schmidt, M.; Stücke, P.

2013-04-01

The appearance of cavitation is still a problem in technical and industrial applications. Especially in automotive internal combustion engines, hydrodynamic journal bearings are used due to their favourable wearing quality and operating characteristics. Cavitation flows inside the bearings reduces the load capacity and leads to a risk of material damages. Therefore an understanding of the complex flow phenomena inside the bearing is necessary for the design development of hydrodynamic journal bearings. Experimental investigations in the fluid domain of the journal bearing are difficult to realize founded by the small dimensions of the bearing. In the recent years more and more the advantages of the computational fluid dynamics (CFD) are used to investigate the detail of the cavitation flows. The analysis in the paper is carried out in a two-step approach. At first an experimental investigation of journal bearing including cavitation is selected from the literature. The complex numerical model validated with the experimental measured data. In a second step, typically design parameters, such as a groove and feed hole, which are necessary to distribute the oil supply across the gap were added into the model. The paper reflects on the influence of the used design parameters and the variation of the additional supply flow rate through the feed hole regarding to cavitation effects in the bearing. Detailed pictures of the three-dimensional flow structures and the cavitation regions inside the flow film of the bearing are presented.

Numerical investigation of cavitation flow in journal bearing geometry

Directory of Open Access Journals (Sweden)

Stücke P.

2013-04-01

Full Text Available The appearance of cavitation is still a problem in technical and industrial applications. Especially in automotive internal combustion engines, hydrodynamic journal bearings are used due to their favourable wearing quality and operating characteristics. Cavitation flows inside the bearings reduces the load capacity and leads to a risk of material damages. Therefore an understanding of the complex flow phenomena inside the bearing is necessary for the design development of hydrodynamic journal bearings. Experimental investigations in the fluid domain of the journal bearing are difficult to realize founded by the small dimensions of the bearing. In the recent years more and more the advantages of the computational fluid dynamics (CFD are used to investigate the detail of the cavitation flows. The analysis in the paper is carried out in a two-step approach. At first an experimental investigation of journal bearing including cavitation is selected from the literature. The complex numerical model validated with the experimental measured data. In a second step, typically design parameters, such as a groove and feed hole, which are necessary to distribute the oil supply across the gap were added into the model. The paper reflects on the influence of the used design parameters and the variation of the additional supply flow rate through the feed hole regarding to cavitation effects in the bearing. Detailed pictures of the three-dimensional flow structures and the cavitation regions inside the flow film of the bearing are presented.

Investigation of the Methane Hydrate Formation by Cavitation Jet

Science.gov (United States)

Morita, H.; Nagao, J.

2015-12-01

Methane hydrate (hereafter called "MH") is crystalline solid compound consisting of hydrogen-bonded water molecules forming cages and methane gas molecules enclosed in the cage. When using MH as an energy resource, MH is dissociated to methane gas and water and collect only the methane gas. The optimum MH production method was the "depressurization method". Here, the production of MH means dissociating MH in the geologic layers and collecting the resultant methane gas by production systems. In the production of MH by depressurization method, MH regeneration was consider to important problem for the flow assurance of MH production system. Therefore, it is necessary to clarify the effect of flow phenomena in the pipeline on hydrate regeneration. Cavitation is one of the flow phenomena which was considered a cause of MH regeneration. Large quantity of microbubbles are produced by cavitation in a moment, therefore, it is considered to promote MH formation. In order to verify the possible of MH regeneration by cavitation, it is necessary to detailed understanding the condition of MH formation by cavitation. As a part of a Japanese National hydrate research program (MH21, funded by METI), we performed a study on MH formation using by cavitation. The primary objective of this study is to demonstrate the formation MH by using cavitation in the various temperature and pressure condition, and to clarify the condition of MH formation by using observation results.

Cavitation simulation and NPSH prediction of a double suction centrifugal pump

International Nuclear Information System (INIS)

Li, P; Huang, Y F; Li, J

2012-01-01

This paper illustrates the flow field numerical analysis of the double-suction centrifugal pump. For the study of the cavitation flow inside the double-suction centrifugal pump, the professional pump/motor simulation software PumpLinx and its Full Cavitation Model has been employed. According to the PumpLinx calculation result and the Cavitation damage index, the cavitation position, level and the cavitation characteristics of the double-suction centrifugal pump has been predicted. For the further objective, the simulation of the flow field in the double-suction centrifugal pump under different inlet conditions has been carried out. By the result analysis, NPSHr has been predicted; the reliability of the results has been verified by comparing with the experimental data. At the same time, this practice can provide guidance for the optimal design of double-suction pump.

Size effects on cavitation instabilities

DEFF Research Database (Denmark)

Niordson, Christian Frithiof; Tvergaard, Viggo

2006-01-01

growth is here analyzed for such cases. A finite strain generalization of a higher order strain gradient plasticity theory is applied for a power-law hardening material, and the numerical analyses are carried out for an axisymmetric unit cell containing a spherical void. In the range of high stress...... triaxiality, where cavitation instabilities are predicted by conventional plasticity theory, such instabilities are also found for the nonlocal theory, but the effects of gradient hardening delay the onset of the instability. Furthermore, in some cases the cavitation stress reaches a maximum and then decays...... as the void grows to a size well above the characteristic material length....

Analogy of water as compared to sodium in cavitation

International Nuclear Information System (INIS)

Bisci, R.; Courbiere, P.

1976-01-01

After outlining the major aspects of the cavitation research and test program undertaken by the CEA(3) (survey of the parameters defining the onset of cavitation in water and sodium flow, and the consequences of operation under sustained cavitating conditions on sodium reactor structural components), this paper describes the test and measuring equipment that has been developed for such studies. The results of the initial tests in water and in sodium using a thin 20 mm dia.orifices plate, are then presented. Except for uncertainties about the measurements themselves, the cavitation threshold values in cold water and in sodium at temperatures above 400 0 C has shown rather good concordance. Testing is currently in progress to confirm these findings. (1) EEC engineer assigned to DRNR/SEDC, (2) CEA engineer (DRNR/STRS), (3) French Atomic Energy Commision. (author)

Birefringence and incipient plastic deformation in elastically overdriven [100] CaF2 under shock compression

Science.gov (United States)

Li, Y.; Zhou, X. M.; Cai, Y.; Liu, C. L.; Luo, S. N.

2018-04-01

[100] CaF2 single crystals are shock-compressed via symmetric planar impact, and the flyer plate-target interface velocity histories are measured with a laser displacement interferometry. The shock loading is slightly above the Hugoniot elastic limit to investigate incipient plasticity and its kinetics, and its effects on optical properties and deformation inhomogeneity. Fringe patterns demonstrate different features in modulation of fringe amplitude, including birefringence and complicated modulations. The birefringence is attributed to local lattice rotation accompanying incipient plasticity. Spatially resolved measurements show inhomogeneity in deformation, birefringence, and fringe pattern evolutions, most likely caused by the inhomogeneity associated with lattice rotation and dislocation slip. Transiently overdriven elastic states are observed, and the incubation time for incipient plasticity decreases inversely with increasing overdrive by the elastic shock.

Detection of the incipient oxidation of coal by petrographic techniques

CSIR Research Space (South Africa)

Kruszewska, KJ

1996-05-01

Full Text Available Two petrographic methods, namely long-wave fluorescence intensity measurements and a vitrinite elasticity index were developed and used to detect incipient oxidation in coals subjected to simulated weathering conditions. The two methods are based...

Cavitational hydrothermal oxidation: A new remediation process. Annual progress report, September 1996--August 1997

Energy Technology Data Exchange (ETDEWEB)

Suslick, K.S.

1997-11-21

'During the past year, the authors have continued to make substantial scientific progress on the understanding of cavitation phenomena in aqueous media and applications of cavitation to remediation processes. The efforts have focused on three separate areas: sonoluminescence as a probe of conditions created during cavitational collapse in aqueous media, the use of cavitation for remediation of contaminated water, and an addition of the use of ultrasound in the synthesis of novel heterogeneous catalysts for hydrodehalogenation of halocarbons under mild conditions. In order to gain further understanding of the conditions present during cavitation, the author has continued his studies of sonoluminescence. He has made recent breakthroughs in the use of emission spectroscopy for temperature and pressure measurement of cavitation events, which he expects to publish shortly. He has been able to measure for the first time the temperature of cavitation in water during multi-bubble cavitation in the presence of aromatic hydrocarbons. The emission from excited states of C{sub 2} in water gives temperatures that are consistent with adiabatic compressional heating, with maximum temperatures of 4,300 K. Prior measurements of cavitation temperatures in low vapor pressure nonaqueous media gave somewhat higher temperatures of 5,000 K. This work lays permanently to rest exotic mechanisms for cavitational chemistry, at least for cavitation fields.'

Study about the influence of cavitation on the dynamic characteristics for the sliding bearing

International Nuclear Information System (INIS)

Zhai, L M; Luo, Y Y; Wang, Z W

2015-01-01

Sliding bearings are employed to support the rotor system and limit the vibration amplitude. In high speed rotor system, cavitation often occurs in the oil film and affects the dynamic characteristics of the sliding bearing greatly. In this paper, numerical method is adopted to simulate the cavitation in the oil film with homogeneous two-phase mixture flow using Singhal-et-al cavitation model in the commercial code FLUENT-solver. Cases without cavitation model were also calculated at the same time. Many computations with different frequency ratios were conducted. Then the rotor dynamic characteristics of the sliding bearing were retrieved. The results show that the cavitation has great influences on the pressure distribution in the oil film. As the rotational speed or whirling speed of the journal increases, the cavitation will become prominent. The dynamic coefficients of the bearing such as stiffness and damping with cavitation model considered are quite different from that without cavitation. So it is worth to pay attention to and do further study about the cavitation in the sliding bearing in the high speed rotor system

Developing countries and incipient industrialization: a case study of ...

African Journals Online (AJOL)

Botswana's small and large towns offer good examples of incipient industrialization and enterprise clustering in a developing economy. Using data from Lobatse, a small industrial centre in Botswana, this brief paper shows that clustering in developing countries does not necessarily induce high inter-firm relationships as is ...

Single-transducer dual-frequency ultrasound generation to enhance acoustic cavitation.

Science.gov (United States)

Liu, Hao-Li; Hsieh, Chao-Ming

2009-03-01

Dual- or multiple-frequency ultrasound stimulation is capable of effectively enhancing the acoustic cavitation effect over single-frequency ultrasound. Potential application of this sonoreactor design has been widely proposed such as on sonoluminescence, sonochemistry enhancement, and transdermal drug release enhancement. All currently available sonoreactor designs employed multiple piezoelectric transducers for generating single-frequency ultrasonic waves separately and then these waves were mixed and interfered in solutions. The purpose of this research is to propose a novel design of generating dual-frequency ultrasonic waves with single piezoelectric elements, thereby enhancing acoustic cavitation. Macroscopic bubbles were detected optically, and they were quantified at either a single-frequency or for different frequency combinations for determining their efficiency for enhancing acoustic cavitation. Visible bubbles were optically detected and hydrogen peroxide was measured to quantify acoustic cavitation. Test water samples with different gas concentrations and different power levels were used to determine the efficacy of enhancing acoustic cavitation of this design. The spectrum obtained from the backscattered signals was also recorded and examined to confirm the occurrence of stable cavitation. The results confirmed that single-element dual-frequency ultrasound stimulation can enhance acoustic cavitation. Under certain testing conditions, the generation of bubbles can be enhanced up to a level of five times higher than the generation of bubbles in single-frequency stimulation, and can increase the hydrogen peroxide production up to an increase of one fold. This design may serve as a useful alternative for future sonoreactor design owing to its simplicity to produce dual- or multiple-frequency ultrasound.

Three-dimensional numerical simulations of turbulent cavitating flow in a rectangular channel

Science.gov (United States)

Iben, Uwe; Makhnov, Andrei; Schmidt, Alexander

2018-05-01

Cavitation is a phenomenon of formation of bubbles (cavities) in liquid as a result of pressure drop. Cavitation plays an important role in a wide range of applications. For example, cavitation is one of the key problems of design and manufacturing of pumps, hydraulic turbines, ship's propellers, etc. Special attention is paid to cavitation erosion and to performance degradation of hydraulic devices (noise, fluctuations of the mass flow rate, etc.) caused by the formation of a two-phase system with an increased compressibility. Therefore, development of a model to predict cavitation inception and collapse of cavities in high-speed turbulent flows is an important fundamental and applied task. To test the algorithm three-dimensional simulations of turbulent flow of a cavitating liquid in a rectangular channel have been conducted. The obtained results demonstrate the efficiency and robustness of the formulated model and the algorithm.

Software System for Finding the Incipient Faults in Power Transformers

Directory of Open Access Journals (Sweden)

Nikolina Petkova

2015-05-01

Full Text Available In this paper a new software system for finding of incipient faultsis presented.An experiment is made with real measurement of partial discharge(PD that appeared in power transformer. The software system usesacquisition data to define the real state of this transformer. One of the most important criteria for the power transformer’s state is the presence of partial discharges. The wave propagation caused by partial discharge depends on scheme of the winding and construction of the power equipment. In all cases, the PD source had a specific position so the wave measured from the PD –coupling device had a specific waveform. The waveform is different when PDcoupling device is put on a specific place. The waveform and the time of propagation are criteria for the localization of the source of incipient faults in the volume of power transformer.

Rayleigh-Plesset equation of the bubble stable cavitation in water: A nonequilibrium all-atom molecular dynamics simulation study

Science.gov (United States)

Man, Viet Hoang; Li, Mai Suan; Derreumaux, Philippe; Nguyen, Phuong H.

2018-03-01

The Rayleigh-Plesset (RP) equation was derived from the first principles to describe the bubble cavitation in liquids in terms of macroscopic hydrodynamics. A number of nonequilibrium molecular dynamics studies have been carried out to validate this equation in describing the bubble inertial cavitation, but their results are contradictory and the applicability of the RP equation still remains to be examined, especially for the stable cavitation. In this work, we carry out nonequilibrium all-atom simulation to validate the applicability of the RP equation in the description of the stable cavitation of nano-sized bubbles in water. We show that although microscopic effects are not explicitly included, this equation still describes the dynamics of subnano-bubbles quite well as long as the contributions of various terms including inertial, surface tension, and viscosity are correctly taken into account. These terms are directly and inversely proportional to the amplitude and period of the cavitation, respectively. Thus, their contributions to the RP equation depend on these two parameters. This may explain the discrepancy between the current results obtained using different parameters. Finally, the accuracy of the RP equation in the current mathematical modeling studies of the ultrasound-induced blood-brain-barrier experiments is discussed in some detail.

Performance characterisation of a passive cavitation detector optimised for subharmonic periodic shock waves from acoustic cavitation in MHz and sub-MHz ultrasound.

Science.gov (United States)

Johansen, Kristoffer; Song, Jae Hee; Prentice, Paul

2018-05-01

We describe the design, construction and characterisation of a broadband passive cavitation detector, with the specific aim of detecting low frequency components of periodic shock waves, with high sensitivity. A finite element model is used to guide selection of matching and backing layers for the shock wave passive cavitation detector (swPCD), and the performance is evaluated against a commercially available device. Validation of the model, and characterisation of the swPCD is achieved through experimental detection of laser-plasma bubble collapse shock waves. The final swPCD design is 20 dB more sensitive to the subharmonic component, from acoustic cavitation driven at 220 kHz, than the comparable commercial device. This work may be significant for monitoring cavitation in medical applications, where sensitive detection is critical, and higher frequencies are more readily absorbed by tissue. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Hydrodynamic cavitation: a bottom-up approach to liquid aeration

NARCIS (Netherlands)

Raut, J.S.; Stoyanov, S.D.; Duggal, C.; Pelan, E.G.; Arnaudov, L.N.; Naik, V.M.

2012-01-01

We report the use of hydrodynamic cavitation as a novel, bottom-up method for continuous creation of foams comprising of air microbubbles in aqueous systems containing surface active ingredients, like proteins or particles. The hydrodynamic cavitation was created using a converging-diverging nozzle.

Cavitation Erosion of Cermet-Coated Aluminium Bronzes

Directory of Open Access Journals (Sweden)

Ion Mitelea

2016-03-01

Full Text Available The cavitation erosion resistance of CuAl10Ni5Fe2.5Mn1 following plasma spraying with Al2O3·30(Ni20Al powder and laser re-melting was analyzed in view of possible improvements of the lifetime of components used in hydraulic environments. The cavitation erosion resistance was substantially improved compared with the one of the base material. The thickness of the re-melted layer was in the range of several hundred micrometers, with a surface microhardness increasing from 250 to 420 HV 0.2. Compositional, structural, and microstructural explorations showed that the microstructure of the re-melted and homogenized layer, consisting of a cubic Al2O3 matrix with dispersed Ni-based solid solution is associated with the hardness increase and consequently with the improvement of the cavitation erosion resistance.

Mathematical Investigation of the Cavitation Phenomenon in the Nozzle with Partially Surface Wetting

Directory of Open Access Journals (Sweden)

Jablonská Jana

2015-12-01

Full Text Available Partially surface wetting has a great influence on friction losses in the fluid flow in both the pipeline system and the complex shape of hydraulic elements. In many hydraulic elements (valves, pump impellers, cavitation is generated, which significantly changes the hydraulic flow parameters, so the last part of the article is devoted to the mathematical solution of this phenomena and evaluates the impact of wall wetting on the size and shape of the cavitation area which appears in the nozzle and in small gaps at special conditions. If the cavitation appears e. g. near the wall of pipes, the blades of turbine or a pump, then it destroys the material surface. On the basis of this physical experiment (nozzle, a two-dimensional (2D mathematical cavitation model of Schnerr-Sauer was made and calculated shape and size of the cavitation region was compared with the experiment. Later this verified model of cavitation was used for cavitation research flow with partial surface wetting. The pressure drop and the size of the cavitation area as it flows from partially surface wetting theory was tested depending on the adhesion coefficient.

An Experimental Study of Cavitation Detection in a Centrifugal Pump Using Envelope Analysis

Science.gov (United States)

Tan, Chek Zin; Leong, M. Salman

Cavitation represents one of the most common faults in pumps and could potentially lead to a series of failure in mechanical seal, impeller, bearing, shaft, motor, etc. In this work, an experimental rig was setup to investigate cavitation detection using vibration envelope analysis method, and measured parameters included sound, pressure and flow rate for feasibility of cavitation detection. The experiment testing included 3 operating points of the centrifugal pump (B.E.P, 90% of B.E.P and 80% of B.E.P). Suction pressure of the centrifugal pump was decreased gradually until the inception point of cavitation. Vibration measurements were undertaken at various locations including casing, bearing, suction and discharge flange of the centrifugal pump. Comparisons of envelope spectrums under cavitating and non-cavitating conditions were presented. Envelope analysis was proven useful in detecting cavitation over the 3 testing conditions. During the normal operating condition, vibration peak synchronous to rotational speed was more pronounced. It was however during cavitation condition, the half order sub-harmonic vibration component was clearly evident in the envelope spectrums undertaken at all measurement locations except at the pump bearing. The possible explanation of the strong sub-harmonic (½ of BPF) during cavitation existence in the centrifugal pump was due to insufficient time for the bubbles to collapse completely before the end of the single cycle.

Decolourization of Rhodamine B: A swirling jet-induced cavitation combined with NaOCl.

Science.gov (United States)

Mancuso, Giuseppe; Langone, Michela; Laezza, Marco; Andreottola, Gianni

2016-09-01

A hydrodynamic cavitation reactor (Ecowirl) based on swirling jet-induced cavitation has been used in order to allow the degradation of a waste dye aqueous solution (Rhodamine B, RhB). Cavitation generated by Ecowirl reactor was directly compared with cavitation generated by using multiple hole orifice plates. The effects of operating conditions and parameters such as pressure, pH of dye solution, initial concentration of RhB and geometry of the cavitating devices on the degradation rate of RhB were discussed. In similar operative conditions, higher extents of degradation (ED) were obtained using Ecowirl reactor rather than orifice plate. An increase in the ED from 8.6% to 14.7% was observed moving from hole orifice plates to Ecowirl reactor. Intensification in ED of RhB by using hydrodynamic cavitation in presence of NaOCl as additive has been studied. It was found that the decolourization was most efficient for the combination of hydrodynamic cavitation and chemical oxidation as compared to chemical oxidation and hydrodynamic cavitation alone. The value of ED of 83.4% was reached in 37min using Ecowirl combined with NaOCl (4.0mgL(-1)) as compared to the 100min needed by only mixing NaOCl at the same concentration. At last, the energetic consumptions of the cavitation devices have been evaluated. Increasing the ED and reducing the treatment time, Ecowirl reactor resulted to be more energy efficient as compared to hole orifice plates, Venturi and other swirling jet-induced cavitation devices, as reported in literature. Copyright © 2016 Elsevier B.V. All rights reserved.

Acute and long-term effect of antihypertensive treatment on exercise-induced albuminuria in incipient diabetic nephropathy

DEFF Research Database (Denmark)

Christensen, Cramer; Mogensen, C E

1986-01-01

. In the acute study, using placebo/metoprolol 10 mg i.v. in patients with normal UAE, the maximal SBP at 600 kpm/min was reduced by 17 mmHg +/- 10 (SD) (2p less than 1.0%) and the maximal SBP at 600 kpm/min in the patients with incipient nephropathy was reduced by 15 mmHg +/- 11 (SD) (2p less than 1.......0%). However, no difference was observed in UAE, in patients with normal UAE or those with incipient nephropathy. Five of the patients with incipient nephropathy were followed with repeated exercise tests before and during 2.6 years of antihypertensive treatment, using metoprolol 200 mg/24 h and subsequently...

Fault prediction for nonlinear stochastic system with incipient faults based on particle filter and nonlinear regression.

Science.gov (United States)

Ding, Bo; Fang, Huajing

2017-05-01

This paper is concerned with the fault prediction for the nonlinear stochastic system with incipient faults. Based on the particle filter and the reasonable assumption about the incipient faults, the modified fault estimation algorithm is proposed, and the system state is estimated simultaneously. According to the modified fault estimation, an intuitive fault detection strategy is introduced. Once each of the incipient fault is detected, the parameters of which are identified by a nonlinear regression method. Then, based on the estimated parameters, the future fault signal can be predicted. Finally, the effectiveness of the proposed method is verified by the simulations of the Three-tank system. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Analysis on transient hydrodynamic characteristics of cavitation process for reactor coolant pump

International Nuclear Information System (INIS)

Wang Xiuli; Wang Peng; Yuan Shouqi; Zhu Rongsheng; Fu Qiang

2014-01-01

The reactor coolant pump hydrodynamic characteristics at different cavitation conditions were studied by using flow field analysis software ANSYS CFX, and the corresponding data were processed and analyzed by using Morlet wavelet transform and fast Fourier transform. The results show that gas content presents the law of exponential function with the pressure reduction or time increase. In the cavitation primary condition, the pulsation frequency of head for the reactor coolant pump is mainly low frequency, and the main frequency of pressure pulsation is still rotation frequency while the effect of the pressure pulsation caused by cavitation on main frequency is not obvious. With the development of cavitation, the pressure fluctuation induced by cavitation becomes more serious especially for the main frequency, secondary frequency and pulsating amplitude while the head pulsation frequency is given priority to low frequency pulse. Under serious cavitation condition, the head pulsation frequency is given priority to irregular changes of pulse high frequency, and also contains almost regular changes of low frequency. (authors)

The acceleration of solid particles subjected to cavitation nucleation

DEFF Research Database (Denmark)

Borkent, B.M.; Arora, M.; Ohl, C.-D.

2008-01-01

The cavity -particle dynamics at cavitation inception on the surface of spherical particles suspended in water and exposed to a strong tensile stress wave is experimentally studied with high-speed photography. Particles, which serve as nucleation sites for cavitation bubbles, are set into a fast...

Effect of hydrodynamic cavitation on zooplankton: A tool for disinfection

Digital Repository Service at National Institute of Oceanography (India)

Sawant, S.S.; Anil, A.C.; Venkat, K.; Gaonkar, C.; Kolwalkar, J.; Khandeparker, L.; Desai, D.V.; Mahulkar, A.V.; Ranade, V.V.; Pandit, A.B.

by individual oscillating cavity, cell wall strength and geometrical and operating parameters of cavitation device. Theoretical model for quantifying the cavitationally generated turbulent shear and extent of microbial disinfection has been developed...

Hydrodynamic cavitation: from theory towards a new experimental approach

Science.gov (United States)

Lucia, Umberto; Gervino, Gianpiero

2009-09-01

Hydrodynamic cavitation is analysed by a global thermodynamics principle following an approach based on the maximum irreversible entropy variation that has already given promising results for open systems and has been successfully applied in specific engineering problems. In this paper we present a new phenomenological method to evaluate the conditions inducing cavitation. We think this method could be useful in the design of turbo-machineries and related technologies: it represents both an original physical approach to cavitation and an economical saving in planning because the theoretical analysis could allow engineers to reduce the experimental tests and the costs of the design process.

The efficiency of a new hydrodynamic cavitation pilot system on Artemia salina cysts and natural population of copepods and bacteria under controlled mesocosm conditions.

Science.gov (United States)

Cvetković, Martina; Grego, Mateja; Turk, Valentina

2016-04-15

A study of the efficiency of hydrodynamic cavitation and separation was carried out to evaluate an innovative, environmentally safe and acceptable system for ballast water treatment for reducing the risk of introducing non-native species worldwide. Mesocosm experiments were performed to assess the morphological changes and viability of zooplankton (copepods), Artemia salina cysts, and the growth potential of marine bacteria after the hydrodynamic cavitation treatment with a different number of cycles. Our preliminary results confirmed the significant efficiency of the treatment since more than 98% of the copepods and A. salina cysts were damaged, in comparison with the initial population. The efficiency increased with the number of the hydrodynamic cavitation cycles, or in combination with a separation technique for cysts. There was also a significant decrease in bacterial abundance and growth rate, compared to the initial number and growth potential. Copyright © 2015 Elsevier Ltd. All rights reserved.

Turbulence and Cavitation Suppression by Quaternary Ammonium Salt Additives.

Science.gov (United States)

Naseri, Homa; Trickett, Kieran; Mitroglou, Nicholas; Karathanassis, Ioannis; Koukouvinis, Phoevos; Gavaises, Manolis; Barbour, Robert; Diamond, Dale; Rogers, Sarah E; Santini, Maurizio; Wang, Jin

2018-05-16

We identify the physical mechanism through which newly developed quaternary ammonium salt (QAS) deposit control additives (DCAs) affect the rheological properties of cavitating turbulent flows, resulting in an increase in the volumetric efficiency of clean injectors fuelled with diesel or biodiesel fuels. Quaternary ammonium surfactants with appropriate counterions can be very effective in reducing the turbulent drag in aqueous solutions, however, less is known about the effect of such surfactants in oil-based solvents or in cavitating flow conditions. Small-angle neutron scattering (SANS) investigations show that in traditional DCA fuel compositions only reverse spherical micelles form, whereas reverse cylindrical micelles are detected by blending the fuel with the QAS additive. Moreover, experiments utilising X-ray micro computed tomography (micro-CT) in nozzle replicas, quantify that in cavitation regions the liquid fraction is increased in the presence of the QAS additive. Furthermore, high-flux X-ray phase contrast imaging (XPCI) measurements identify a flow stabilization effect in the region of vortex cavitation by the QAS additive. The effect of the formation of cylindrical micelles is reproduced with computational fluid dynamics (CFD) simulations by including viscoelastic characteristics for the flow. It is demonstrated that viscoelasticity can reduce turbulence and suppress cavitation, and subsequently increase the injector's volumetric efficiency.

Cavitational micro-particles: plasma formation mechanisms

International Nuclear Information System (INIS)

Bica, Ioan

2005-01-01

Cavitational micro-particles are a class to which the micro-spheres, the micro-tubes and the octopus-shaped micro-particles belong. The cavitational micro-particles (micro-spheres, micro-tubes and octopus-shaped micro-particles) at an environmental pressure. The micro-spheres, the micro-tubes and the ligaments of the octopus-shaped micro-particles are produced in the argon plasma and are formed of vapors with low values of the molar concentration in comparison with the molar density of the gas and vapor mixture, the first one on the unstable and the last two on the stable movement of the vapors. The ligaments of the octopus-shaped micro-particles are open at the top for well-chosen values of the sub-cooling of the vapor and gas cylinders. The nitrogen in the air favors the formation of pores in the wall of the micro-spheres. In this paper we present the cavitational micro-particles, their production in the plasma and some mechanisms for their formation in the plasma. (author)

Estimation of flows cavitation by similarity test: application to the couple water/liquid sodium

International Nuclear Information System (INIS)

Espanet, Laurent

2000-01-01

In many industrial flows, it is necessary to perform a similarity test to assess the cavitation intensity. The similarity laws must take into account the physical properties of the two fluids and especially the surface tension. To obtain such laws, a continuous description of the two-phase flow has been used. The non linear model of Cahn and Hilliard allows to obtain the equations of motion for these fluids, and non-dimensional conditions yield to the similarity laws. This method has been checked experimentally by achieving two different flows through a diaphragm. When respecting the similarity laws, the comparison of these flows allows to validate the transposition laws and to determine their associated tolerance. At last, the number of dusts and particles is an important parameter for cavitation inception threshold since it leads to the number of bubbles. Using the Laplace theory, it is shown that for each value of flow rate, it exists an upper bound value for the bubble density, which allows to establish a similarity law concerning this number of bubbles. (author) [fr

Multiple incipient sensor faults diagnosis with application to high-speed railway traction devices.

Science.gov (United States)

Wu, Yunkai; Jiang, Bin; Lu, Ningyun; Yang, Hao; Zhou, Yang

2017-03-01

This paper deals with the problem of incipient fault diagnosis for a class of Lipschitz nonlinear systems with sensor biases and explores further results of total measurable fault information residual (ToMFIR). Firstly, state and output transformations are introduced to transform the original system into two subsystems. The first subsystem is subject to system disturbances and free from sensor faults, while the second subsystem contains sensor faults but without any system disturbances. Sensor faults in the second subsystem are then formed as actuator faults by using a pseudo-actuator based approach. Since the effects of system disturbances on the residual are completely decoupled, multiple incipient sensor faults can be detected by constructing ToMFIR, and the fault detectability condition is then derived for discriminating the detectable incipient sensor faults. Further, a sliding-mode observers (SMOs) based fault isolation scheme is designed to guarantee accurate isolation of multiple sensor faults. Finally, simulation results conducted on a CRH2 high-speed railway traction device are given to demonstrate the effectiveness of the proposed approach. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Relationship between cavitation and loss of echogenicity from ultrasound contrast agents

OpenAIRE

Radhakrishnan, Kirthi; Bader, Kenneth B; Haworth, Kevin J; Kopechek, Jonathan A; Raymond, Jason L; Huang, Shao-Ling; McPherson, David D; Holland, Christy K

2013-01-01

Ultrasound contrast agents (UCAs) have the potential to nucleate cavitation and promote both beneficial and deleterious bioeffects in vivo. Previous studies have elucidated the pulse-duration dependent pressure amplitude threshold for rapid loss of echogenicity due to UCA fragmentation. Previous studies have demonstrated that UCA fragmentation was concomitant with inertial cavitation. The purpose of this study was to evaluate the relationship between stable and inertial cavitation thresholds ...

Optimization of centrifugal pump cavitation performance based on CFD

International Nuclear Information System (INIS)

Xie, S F; Wang, Y; Liu, Z C; Zhu, Z T; Ning, C; Zhao, L F

2015-01-01

In order to further improve the cavitation performance of a centrifugal pump, slots on impeller blade near inlet were studied and six groups of hydraulic model were designed. Base on cavitating flow feature inside a centrifugal pump, bubble growth and implosion are calculated from the Rayleigh-Plesset equation which describes the dynamic behavior of spherical bubble and RNG κ-ε model was employed to simulate and analyze the internal two-phase flow of the model pump under the same conditions. The simulation results show that slots on blade near inlet could improve the cavitation performance and cavitation performance improvement of the second group was more obvious. Under the same conditions, the pressure on the back of blade near inlet was higher than the pressure on the back of unmodified blade near inlet, and energy distribution in the flow channel between the two blades was more uniform with a small change of head

The Role of Cavitation in Liposome Formation

OpenAIRE

Richardson, Eric S.; Pitt, William G.; Woodbury, Dixon J.

2007-01-01

Liposome size is a vital parameter of many quantitative biophysical studies. Sonication, or exposure to ultrasound, is used widely to manufacture artificial liposomes, yet little is known about the mechanism by which liposomes are affected by ultrasound. Cavitation, or the oscillation of small gas bubbles in a pressure-varying field, has been shown to be responsible for many biophysical effects of ultrasound on cells. In this study, we correlate the presence and type of cavitation with a decr...

Probability of cavitation for single ultrasound pulses applied to tissues and tissue-mimicking materials.

Science.gov (United States)

Maxwell, Adam D; Cain, Charles A; Hall, Timothy L; Fowlkes, J Brian; Xu, Zhen

2013-03-01

In this study, the negative pressure values at which inertial cavitation consistently occurs in response to a single, two-cycle, focused ultrasound pulse were measured in several media relevant to cavitation-based ultrasound therapy. The pulse was focused into a chamber containing one of the media, which included liquids, tissue-mimicking materials, and ex vivo canine tissue. Focal waveforms were measured by two separate techniques using a fiber-optic hydrophone. Inertial cavitation was identified by high-speed photography in optically transparent media and an acoustic passive cavitation detector. The probability of cavitation (P(cav)) for a single pulse as a function of peak negative pressure (p(-)) followed a sigmoid curve, with the probability approaching one when the pressure amplitude was sufficient. The statistical threshold (defined as P(cav) = 0.5) was between p(-) = 26 and 30 MPa in all samples with high water content but varied between p(-) = 13.7 and >36 MPa in other media. A model for radial cavitation bubble dynamics was employed to evaluate the behavior of cavitation nuclei at these pressure levels. A single bubble nucleus with an inertial cavitation threshold of p(-) = 28.2 megapascals was estimated to have a 2.5 nm radius in distilled water. These data may be valuable for cavitation-based ultrasound therapy to predict the likelihood of cavitation at various pressure levels and dimensions of cavitation-induced lesions in tissue. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Investigation of cavitating flows by X-ray and optical imaging

Science.gov (United States)

Coutier-Delgosha, Olivier; Fuzier, Sylvie; Khlifa, Ilyass; Fezzaa, Kamel

2015-11-01

Hydrodynamic cavitation is the partial vaporization of high speed liquid flows. The turbulent, compressible and unsteady character of these flows makes their study unusually complex and challenging. Instabilities generated by the occurrence of cavitation have been investigated in the last years in the LML laboratory by various non-intrusive measurements including X-ray imaging (to obtain the fields of void fraction and velocity in both phases), and PIV with fluorescent particles (to obtain the velocity fields in both phases). It has been shown that cavitation is characterized by significant slip velocities between liquid and vapor, especially in the re-entrant jet area and the cavity wake. This results suggests some possible improvements in the numerical models currently used for CFD of cavitating flows. Professor at Arts et Metiers ParisTech, Director of the LML laboratory.

Numerical analysis of the effects of radiation heat transfer and ionization energy loss on the cavitation Bubble's dynamics

Energy Technology Data Exchange (ETDEWEB)

Mahdi, M. [Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of); Ebrahimi, R. [Faculty of Aerospace Engineering, K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of); Shams, M., E-mail: shams@kntu.ac.ir [Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Pardis St., Molla-Sadra Ave, Vanak. Sq., P.O. Box: 19395-1999, Tehran (Iran, Islamic Republic of)

2011-06-13

A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with the experimental data and a good correspondence was observed. The dynamics of hydrofoil cavitation bubble were also investigated. It was concluded that the thermal radiation heat transfer rate strongly depended on the cavitation number, initial bubble radius and hydrofoil angle of attack. -- Highlights: → Heat transfer and ionization energy losses were analyzed in the cavitation bubble. → Radiation of hydrodynamic bubble was approximately equal to the black body. → Radiation heat transfer did not affect the bubble dynamic. → Conduction decreased the bubble pressure and increased the bubble temperature. → Ionization decreased the temperature and increased the pressure in the bubble.

Research on the induction motor current signature for centrifugal pump at cavitation condition

Directory of Open Access Journals (Sweden)

Yin Luo

2015-11-01

Full Text Available Cavitation is a major undesirable phenomenon for centrifugal pump because it can cause hydraulic performance deterioration, pump damage by pitting and material erosion, and structural vibration and noise. Cavitation can appear within the entire range of the operating conditions; therefore, it must be prevented by all means. Sensorless monitoring technology based on motor current signature analysis is non-intrusive and economic for monitoring motor-driven equipment. Thus, this technology is suitable for centrifugal pump systems. The motor current signature for centrifugal pump load at the cavitation condition is the basis of this technology. However, systematic research is lacking on sensorless monitoring technology based on motor current signature. As a result, the tentative exploration for motor current signature at cavitation load was conducted in this study. The results show that the stator current is still a sinusoidal alternating current strictly to the law of sine. Moreover, the root mean square of the current fluctuates because of different flow regimes in the cavitation progress and decreases because vapor density is smaller than water density when cavitation is fully formed. For the stator current spectrum, the noise level, noise distribution, rotation speed, and vane pass frequency components show features in the cavitation process. These indicator indexes change according to the stage of cavitation development. Thus, the motor current signature analysis is found to be a feasible and cost-effective method for the stages of cavitation condition.

Oxidation of alkylarenes to the corresponding acids using aqueous potassium permanganate by hydrodynamic cavitation.

Science.gov (United States)

Ambulgekar, G V; Samant, S D; Pandit, A B

2004-05-01

Oxidation of toluene using aqueous potassium permanganate was studied under heterogeneous condition in the presence of hydrodynamic cavitation and compared with the results of the reaction under acoustic cavitation. Various parameters, such as quantity of potassium permanganate, toluene to aqueous phase ratio, reaction time and cavitation parameters such as orifice plate, and pump discharge pressure were optimized. The reaction was found to be considerably accelerated at ambient temperature in the presence of cavitation. On comparison, it was found that when 1 kJ of energy was passed to the reaction mixture in the case of acoustic cavitation, the product obtained was 4.63 x 10(-6) mol, whereas when 1 kJ of energy was passed to the reaction mixture in the case of hydrodynamic cavitation the product obtained was 2.70 x 10(-5) mol. Hence, about six times more product would be obtained in the case of hydrodynamic cavitation than in the case of acoustic cavitation at same energy dissipation. It has been observed that further optimization is possible.

Interstitial Matrix Prevents Therapeutic Ultrasound From Causing Inertial Cavitation in Tumescent Subcutaneous Tissue.

Science.gov (United States)

Koulakis, John P; Rouch, Joshua; Huynh, Nhan; Dubrovsky, Genia; Dunn, James C Y; Putterman, Seth

2018-01-01

We search for cavitation in tumescent subcutaneous tissue of a live pig under application of pulsed, 1-MHz ultrasound at 8 W cm -2 spatial peak and pulse-averaged intensity. We find no evidence of broadband acoustic emission indicative of inertial cavitation. These acoustic parameters are representative of those used in external-ultrasound-assisted lipoplasty and in physical therapy and our null result brings into question the role of cavitation in those applications. A comparison of broadband acoustic emission from a suspension of ultrasound contrast agent in bulk water with a suspension injected subcutaneously indicates that the interstitial matrix suppresses cavitation and provides an additional mechanism behind the apparent lack of in-vivo cavitation to supplement the absence of nuclei explanation offered in the literature. We also find a short-lived cavitation signal in normal, non-tumesced tissue that disappears after the first pulse, consistent with cavitation nuclei depletion in vivo. Copyright © 2018 World Federation for Ultrasound in Medicine and Biology. Published by Elsevier Inc. All rights reserved.

Observation of a cavitation cloud in tissue using correlation between ultrafast ultrasound images.

Science.gov (United States)

Prieur, Fabrice; Zorgani, Ali; Catheline, Stefan; Souchon, Rémi; Mestas, Jean-Louis; Lafond, Maxime; Lafon, Cyril

2015-07-01

The local application of ultrasound is known to improve drug intake by tumors. Cavitating bubbles are one of the contributing effects. A setup in which two ultrasound transducers are placed confocally is used to generate cavitation in ex vivo tissue. As the transducers emit a series of short excitation bursts, the evolution of the cavitation activity is monitored using an ultrafast ultrasound imaging system. The frame rate of the system is several thousands of images per second, which provides several tens of images between consecutive excitation bursts. Using the correlation between consecutive images for speckle tracking, a decorrelation of the imaging signal appears due to the creation, fast movement, and dissolution of the bubbles in the cavitation cloud. By analyzing this area of decorrelation, the cavitation cloud can be localized and the spatial extent of the cavitation activity characterized.

Effects of Hydrodynamic Cavitation of a Restriction Orifice on Crud-like Deposits

International Nuclear Information System (INIS)

Kim, Seong Man; Lee, Seung Won; Park, Sung Dae; Kang, Sarah; Seo, Han; Bang, In Cheol

2011-01-01

Axial Offset Anomaly (AOA) referring to an unexpected neutron flux depression is also known as Crud Induced Power Shift (CIPS). Fuel assemblies removed from an AOA core has shown a thick porous deposition layer of crud on fuel clad surface. The deposition layer was induced by precipitation reactions of both boron species and crud during sub-cooled nucleate boiling. Therefore, to resolve the AOA issues, a fuel cleaning technology using ultrasonic cavitation has been developed by EPRI and applied to the domestic NPPs by KNF. However, the performance of crud removal during maintenance of NPPs is known to be not enough. Hydrodynamic cavitation is the process of vaporization, bubble generation and bubble implosion which occurs in a flowing liquid as a result of decrease and subsequent increase in pressure. Hydrodynamic cavitation generates shock pressure of a few tens MPa due to bubble collapse like the cavitation generated by Ultrasonics. It is well known that the cavitation can erode the metal surface. The idea of the current study is that such energetic cavitation bubble collapses could help to remove the crud from the fuel assembly. Therefore, the current study first investigates effects of hydrodynamic cavitation occurred from a single hole orifice fundamentally

Effects of Hydrodynamic Cavitation of a Restriction Orifice on Crud-like Deposits

Energy Technology Data Exchange (ETDEWEB)

Kim, Seong Man; Lee, Seung Won; Park, Sung Dae; Kang, Sarah; Seo, Han; Bang, In Cheol [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

2011-10-15

Axial Offset Anomaly (AOA) referring to an unexpected neutron flux depression is also known as Crud Induced Power Shift (CIPS). Fuel assemblies removed from an AOA core has shown a thick porous deposition layer of crud on fuel clad surface. The deposition layer was induced by precipitation reactions of both boron species and crud during sub-cooled nucleate boiling. Therefore, to resolve the AOA issues, a fuel cleaning technology using ultrasonic cavitation has been developed by EPRI and applied to the domestic NPPs by KNF. However, the performance of crud removal during maintenance of NPPs is known to be not enough. Hydrodynamic cavitation is the process of vaporization, bubble generation and bubble implosion which occurs in a flowing liquid as a result of decrease and subsequent increase in pressure. Hydrodynamic cavitation generates shock pressure of a few tens MPa due to bubble collapse like the cavitation generated by Ultrasonics. It is well known that the cavitation can erode the metal surface. The idea of the current study is that such energetic cavitation bubble collapses could help to remove the crud from the fuel assembly. Therefore, the current study first investigates effects of hydrodynamic cavitation occurred from a single hole orifice fundamentally

Effect of hydrodynamic cavitation in the tissue erosion by pulsed high-intensity focused ultrasound (pHIFU)

Science.gov (United States)

Zhou, Yufeng; Gao, Xiaobin Wilson

2016-09-01

High-intensity focused ultrasound (HIFU) is emerging as an effective therapeutic modality in clinics. Besides the thermal ablation, tissue disintegration is also possible because of the interaction between the distorted HIFU bursts and either bubble cloud or boiling bubble. Hydrodynamic cavitation is another type of cavitation and has been employed widely in industry, but its role in mechanical erosion to tissue is not clearly known. In this study, the bubble dynamics immediately after the termination of HIFU exposure in the transparent gel phantom was captured by high-speed photography, from which the bubble displacement towards the transducer and the changes of bubble size was quantitatively determined. The characteristics of hydrodynamic cavitation due to the release of the acoustic radiation force and relaxation of compressed surrounding medium were found to associate with the number of pulses delivered and HIFU parameters (i.e. pulse duration and pulse repetition frequency). Because of the initial big bubble (~1 mm), large bubble expansion (up to 1.76 folds), and quick bubble motion (up to ~1 m s-1) hydrodynamic cavitation is significant after HIFU exposure and may lead to mechanical erosion. The shielding effect of residual tiny bubbles would reduce the acoustic energy delivered to the pre-existing bubble at the focus and, subsequently, the hydrodynamic cavitation effect. Tadpole shape of mechanical erosion in ex vivo porcine kidney samples was similar to the contour of bubble dynamics in the gel. Liquefied tissue was observed to emit towards the transducer through the punctured tissue after HIFU exposure in the sonography. In summary, the release of HIFU exposure-induced hydrodynamic cavitation produces significant bubble expansion and motion, which may be another important mechanism of tissue erosion. Understanding its mechanism and optimizing the outcome would broaden and enhance HIFU applications.

Effect of hydrodynamic cavitation in the tissue erosion by pulsed high-intensity focused ultrasound (pHIFU).

Science.gov (United States)

Zhou, Yufeng; Gao, Xiaobin Wilson

2016-09-21

High-intensity focused ultrasound (HIFU) is emerging as an effective therapeutic modality in clinics. Besides the thermal ablation, tissue disintegration is also possible because of the interaction between the distorted HIFU bursts and either bubble cloud or boiling bubble. Hydrodynamic cavitation is another type of cavitation and has been employed widely in industry, but its role in mechanical erosion to tissue is not clearly known. In this study, the bubble dynamics immediately after the termination of HIFU exposure in the transparent gel phantom was captured by high-speed photography, from which the bubble displacement towards the transducer and the changes of bubble size was quantitatively determined. The characteristics of hydrodynamic cavitation due to the release of the acoustic radiation force and relaxation of compressed surrounding medium were found to associate with the number of pulses delivered and HIFU parameters (i.e. pulse duration and pulse repetition frequency). Because of the initial big bubble (~1 mm), large bubble expansion (up to 1.76 folds), and quick bubble motion (up to ~1 m s -1 ) hydrodynamic cavitation is significant after HIFU exposure and may lead to mechanical erosion. The shielding effect of residual tiny bubbles would reduce the acoustic energy delivered to the pre-existing bubble at the focus and, subsequently, the hydrodynamic cavitation effect. Tadpole shape of mechanical erosion in ex vivo porcine kidney samples was similar to the contour of bubble dynamics in the gel. Liquefied tissue was observed to emit towards the transducer through the punctured tissue after HIFU exposure in the sonography. In summary, the release of HIFU exposure-induced hydrodynamic cavitation produces significant bubble expansion and motion, which may be another important mechanism of tissue erosion. Understanding its mechanism and optimizing the outcome would broaden and enhance HIFU applications.

PREFACE: 9th International Symposium on Cavitation (CAV2015)

Science.gov (United States)

Farhat, M.; Müller, A.

2015-12-01

It is our pleasure and privilege to welcome all the participants of the 9th International Symposium on Cavitation (CAV2015) to Lausanne. Since its initiation in 1986 in Sendai, Japan, the CAV symposium has grown to become the world's foremost event dedicated to cavitation. Hosted by EPFL (Ecole Polytechnique Fédérale de Lausanne) and staged at the SwissTech Convention Center, CAV2015 is a unique opportunity to exchange with leading scientists and industry experts about the latest advances in theoretical modelling, numerical simulation and experimentation related to cavitation phenomena with a special emphasis on practical applications. The topics covered by CAV2015 include cavitation in ¬fluid machinery and fuel systems, bubble dynamics, cavitation erosion, advanced numerical simulation, sonochemistery, biomedicine and experimental techniques. CAV2015 will also host an exhibition of leading providers of state of the art measurement equipment, including high-speed imaging systems, non-intrusive velocimetry, pressure sensors, as well as numerical solvers. We have accepted over 190 papers, which will be presented in four parallel sessions. The proceedings will appear in the open access Journal of Physics: Conference Series (JPCS), which is part of the IOP Conference Series. All published papers are fully citable and upon publication will be free to download in perpetuity. We would like to thank all the reviewers for their great help during the selection process. We will also propose six plenary speakers to highlight cavitation issues in different fields. Finally, we would like to warmly thank our sponsors for their valuable support and the local Organizing Committee for the efforts in setting up this important event. We look forward to seeing you in Lausanne!

Cavitation erosion mechanism of titanium alloy radiation rods in aluminum melt.

Science.gov (United States)

Dong, Fang; Li, Xiaoqian; Zhang, Lihua; Ma, Liyong; Li, Ruiqing

2016-07-01

Ultrasound radiation rods play a key role in introducing ultrasonic to the grain refinement of large-size cast aluminum ingots (with diameter over 800 mm), but the severe cavitation corrosion of radiation rods limit the wide application of ultrasonic in the metallurgy field. In this paper, the cavitation erosion of Ti alloy radiation rod (TARR) in the semi-continuous direct-chill casting of 7050 Al alloy was investigated using a 20 kHz ultrasonic vibrator. The macro/micro characterization of Ti alloy was performed using an optical digital microscopy and a scanning electron microscopy, respectively. The results indicated that the cavitation erosion and the chemical reaction play different roles throughout different corrosion periods. Meanwhile, the relationship between mass-loss and time during cavitation erosion was measured and analyzed. According to the rate of mass-loss to time, the whole cavitation erosion process was divided into four individual periods and the mechanism in each period was studied accordingly. Copyright © 2015 Elsevier B.V. All rights reserved.

Cavitation erosion of silver plated coating at different temperatures and pressures

Energy Technology Data Exchange (ETDEWEB)

Hattori, Shuji; Motoi, Yoshihiro [Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fuku-shi, Fukui 910-8507 (Japan); Kikuta, Kengo; Tomaru, Hiroshi [IHI Corperation, TOYOSU IHI BUILDING, 1-1, Toyosu 3-chome, Koto-ku, Tokyo 1358710 (Japan)

2014-04-11

Cavitation often occurs in inducer pumps used for space rockets. Silver plated coating on the inducer liner faces the damage of cavitation. Therefore, it is important to study about the cavitation erosion resistance for silver plated coating at several operating conditions in the inducer pumps. In this study, the cavitation erosion tests were carried for silver plated coating in deionized water and ethanol at several liquid temperatures (273K–400K) and pressures (0.10MPa–0.48MPa). The mass loss rate is evaluated in terms of thermodynamic parameter Σ proposed by Brennen [9], suppression pressure p–p{sub v} (p{sub v}: saturated vapor pressure) and acoustic impedance ρc (ρ: density and c: sound speed). Cavitation bubble behaviors depending on the thermodynamic effect and the liquid type were observed by high speed video camera. The mass loss rate is formulated by thermodynamic parameter Σ, suppression pressure p–p{sub v} and acoustic impedance ρc.

Dynamics of Cavitation Clouds within a High-Intensity Focused Ultrasonic Beam

Science.gov (United States)

2012-03-01

the cloud size. I. INTRODUCTION High-intensity focused ultrasound (HIFU), along with the associated cavitation , is used in a variety of fields. The...Article 3. DATES COVERED (From - To) March 2012- May 2012 4. TITLE AND SUBTITLE Dynamics of Cavitation Clouds within a High-Intensity Focused...in initially quiescent water. The resulting pressure field and behavior of the cavitation bubbles are measured using high-speed digital in-line

Root resistance to cavitation is accurately measured using a centrifuge technique.

Science.gov (United States)

Pratt, R B; MacKinnon, E D; Venturas, M D; Crous, C J; Jacobsen, A L

2015-02-01

Plants transport water under negative pressure and this makes their xylem vulnerable to cavitation. Among plant organs, root xylem is often highly vulnerable to cavitation due to water stress. The use of centrifuge methods to study organs, such as roots, that have long vessels are hypothesized to produce erroneous estimates of cavitation resistance due to the presence of open vessels through measured samples. The assumption that roots have long vessels may be premature since data for root vessel length are sparse; moreover, recent studies have not supported the existence of a long-vessel artifact for stems when a standard centrifuge technique was used. We examined resistance to cavitation estimated using a standard centrifuge technique and compared these values with native embolism measurements for roots of seven woody species grown in a common garden. For one species we also measured vulnerability using single-vessel air injection. We found excellent agreement between root native embolism and the levels of embolism measured using a centrifuge technique, and with air-seeding estimates from single-vessel injection. Estimates of cavitation resistance measured from centrifuge curves were biologically meaningful and were correlated with field minimum water potentials, vessel diameter (VD), maximum xylem-specific conductivity (Ksmax) and vessel length. Roots did not have unusually long vessels compared with stems; moreover, root vessel length was not correlated to VD or to the vessel length of stems. These results suggest that root cavitation resistance can be accurately and efficiently measured using a standard centrifuge method and that roots are highly vulnerable to cavitation. The role of root cavitation resistance in determining drought tolerance of woody species deserves further study, particularly in the context of climate change. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Incipient cognition solves the spatial reciprocity conundrum of cooperation.

Directory of Open Access Journals (Sweden)

Jeromos Vukov

Full Text Available BACKGROUND: From the simplest living organisms to human societies, cooperation among individuals emerges as a paradox difficult to explain and describe mathematically, although very often observed in reality. Evolutionary game theory offers an excellent toolbar to investigate this issue. Spatial structure has been one of the first mechanisms promoting cooperation; however, alone it only opens a narrow window of viability. METHODOLOGY/PRINCIPAL FINDINGS: Here we equip individuals with incipient cognitive abilities, and investigate the evolution of cooperation in a spatial world where retaliation, forgiveness, treason and mutualism may coexist, as individuals engage in Prisoner's Dilemma games. In the model, individuals are able to distinguish their partners and act towards them based on previous interactions. We show how the simplest level of cognition, alone, can lead to the emergence of cooperation. CONCLUSIONS/SIGNIFICANCE: Despite the incipient nature of the individuals' cognitive abilities, cooperation emerges for unprecedented values of the temptation to cheat, being also robust to invasion by cheaters, errors in decision making and inaccuracy of imitation, features akin to many species, including humans.

A Brief Discussion Regarding Types of Cavitation in Squeeze Film Dampers and Cavitation Effects

Directory of Open Access Journals (Sweden)

Laurentiu MORARU

2017-03-01

Full Text Available Squeeze film dampers (SFD are probably the most used shaft control devices in aircraft jet engines; SFDs consist in oil films, elastic elements and various antirotational devices that tune the stiffness and damping of the shafts’ supports and consequently adjust the lateral dynamics of the shaft. Fluid layers in SFDs are usually thin, hence the modeling can often be done using the Reynolds’ theory,; however, some of the main features of the film, namely the behavior of the fluid in the divergent, negative squeeze area, where discontinuities may appear in the liquid, are still subject to intense research. This paper will discuss some aspects regarding the types of cavitation that appear in squeeze film dampers and some of the effects of cavitation on the SFDs.

Cavitation erosion tests of high tensile stainless steels for the Techno-Superliner (TSL-F) hulls; Techno superliner (TSL-F) sentai kozoyo kokyodo stainless ko no cavitation erosion

Energy Technology Data Exchange (ETDEWEB)

Matsuo, M.; Ito, H.; Shibasaki, K. [NKK Corp., Tokyo (Japan); Mizuta, A.; Sugimoto, H. [Kawasaki Heavy Industries, Ltd., Kobe (Japan); Tomono, Y. [Hitachi Zosen Corp., Osaka (Japan)

1996-12-31

Investigations were given by using the magnetostrictive vibration method and the high-speed fluid testing method on cavitation erosion resistance of high-tensile stainless steels thought to have high applicability to submerged hull structures of Techno-Supeliner (TSL-L). The investigations revealed that these steels have nearly equivalent resistance to even SUS 304 or 15-5PH steel which is thought to have the highest cavitation erosion resistance among the conventional materials used customarily. An experiment using both materials provided a result different quantitatively but similar qualitatively in relative merits between the materials. Correlation between both materials was presented. A cavitation erosion experiment using a 1/6 scale model of the actual TSL-F was carried out to measure the amount of cavitation erosion generated on wing surfaces. Results from the experiment were used to attempt estimation of cavitation erosion amount at the level of the actual TSL-F. 21 refs., 12 figs., 3 tabs.

Cavitation erosion tests of high tensile stainless steels for the Techno-Superliner (TSL-F) hulls; Techno superliner (TSL-F) sentai kozoyo kokyodo stainless ko no cavitation erosion

Energy Technology Data Exchange (ETDEWEB)

Matsuo, M; Ito, H; Shibasaki, K [NKK Corp., Tokyo (Japan); Mizuta, A; Sugimoto, H [Kawasaki Heavy Industries, Ltd., Kobe (Japan); Tomono, Y [Hitachi Zosen Corp., Osaka (Japan)

1997-12-31

Investigations were given by using the magnetostrictive vibration method and the high-speed fluid testing method on cavitation erosion resistance of high-tensile stainless steels thought to have high applicability to submerged hull structures of Techno-Supeliner (TSL-L). The investigations revealed that these steels have nearly equivalent resistance to even SUS 304 or 15-5PH steel which is thought to have the highest cavitation erosion resistance among the conventional materials used customarily. An experiment using both materials provided a result different quantitatively but similar qualitatively in relative merits between the materials. Correlation between both materials was presented. A cavitation erosion experiment using a 1/6 scale model of the actual TSL-F was carried out to measure the amount of cavitation erosion generated on wing surfaces. Results from the experiment were used to attempt estimation of cavitation erosion amount at the level of the actual TSL-F. 21 refs., 12 figs., 3 tabs.

Cavitation-based hydro-fracturing simulator

Science.gov (United States)

Wang, Jy-An John; Wang, Hong; Ren, Fei; Cox, Thomas S.

2016-11-22

An apparatus 300 for simulating a pulsed pressure induced cavitation technique (PPCT) from a pressurized working fluid (F) provides laboratory research and development for enhanced geothermal systems (EGS), oil, and gas wells. A pump 304 is configured to deliver a pressurized working fluid (F) to a control valve 306, which produces a pulsed pressure wave in a test chamber 308. The pulsed pressure wave parameters are defined by the pump 304 pressure and control valve 306 cycle rate. When a working fluid (F) and a rock specimen 312 are included in the apparatus, the pulsed pressure wave causes cavitation to occur at the surface of the specimen 312, thus initiating an extensive network of fracturing surfaces and micro fissures, which are examined by researchers.

Numerical analysis of cavitating flow characteristics in impeller of residual heat removal pump

NARCIS (Netherlands)

Hong, Feng; Yuan, Jianping; Zhou, Banglun

2016-01-01

In order to investigate internal cavitating flow characteristics of the impeller in residual heat removal pumps, the three-dimensional cavitating flow in a residual heat removal model pump is numerically calculated by using the homogeneous mixture cavitation model based on the Rayleigh-Plesset

Mathematical Modelling of Fluid Flow in Cone and Cavitation Formation

Directory of Open Access Journals (Sweden)

Milada KOZUBKOVÁ

2011-06-01

Full Text Available Problem of cavitation is the undesirable phenomena occuring in the fluid flow in many hydraulic application (pumps, turbines, valves, etc.. Therefore this is in the focus of interest using experimental and mathematical methods. Based on cavitation modelling in Laval nozzle results and experience [1], [2], [4], following problem described as the water flow at the outlet from turbine blade wheel was solved. Primarily the problem is simplified into modelling of water flow in cone. Profiles of axial, radial and tangential velocity are defined on inlet zone. The value of pressure is defined on the outlet. Boundary conditions were defined by main investigator of the grant project – Energy Institute, Victor Kaplan’s Department of Fluid Engineering, Faculty of Mechanical Engineering, Brno University of Technology. The value of air volume was insignificant. Cavitation was solved by Singhal model of cavitation.

Nanoparticle dispersion in liquid metals by electromagnetically induced acoustic cavitation

International Nuclear Information System (INIS)

Kaldre, Imants; Bojarevičs, Andris; Grants, Ilmārs; Beinerts, Toms; Kalvāns, Matīss; Milgrāvis, Mikus; Gerbeth, Gunter

2016-01-01

Aim of this study is to investigate experimentally the effect of magnetically induced cavitation applied for the purpose of nanoparticle dispersion in liquid metals. The oscillating magnetic force due to the azimuthal induction currents and the axial magnetic field excites power ultrasound in the sample. If the fields are sufficiently high then it is possible to achieve the acoustic cavitation threshold in liquid metals. Cavitation bubble collapses are known to create microscale jets with a potential to break nanoparticle agglomerates and disperse them. The samples are solidified under the contactless ultrasonic treatment and later analyzed by electron microscopy and energy-dispersive X-ray spectroscopy (EDX). It is observed that SiC nanoparticles are dispersed in an aluminum magnesium alloy, whereas in tin the same particles remain agglomerated in micron-sized clusters despite a more intense cavitation.

Ultrasound cavitation versus cryolipolysis for non-invasive body contouring.

Science.gov (United States)

Mahmoud ELdesoky, Mohamed Taher; Mohamed Abutaleb, Enas ELsayed; Mohamed Mousa, Gihan Samir

2015-08-24

The demand for non-surgical and non-invasive devices is continuous and increasing. Such devices have gradually gained ground in the reduction of localised fat and the improvement of body contouring. The study aimed to compare the effects of ultrasound cavitation and cryolipolysis on localised abdominal fat. In total, 60 participants with a body mass index (BMI) over 30 kg/m 2 , whose age ranged between 25 and 45 years, were included. The participants were randomly assigned to three groups of 20 each, using ultrasound cavitation and diet, cryolipolysis and diet, and diet only (the control group), respectively. Measures were bodyweight, BMI, waist circumference and suprailiac skinfold were measured at the beginning of the study and 2 months later. The three groups showed significant improvements in all measured variables after 2 months. There was no statistically significant difference in bodyweight or in BMI among the groups after treatment. However, the groups using ultrasound cavitation and cryolipolysis showed better post-treatment improvement than the diet-only group in waist circumference and suprailiac skinfold. There was no statistically significant difference post-treatment between the cavitation and cryolipolysis groups in waist circumference or suprailiac skinfold. Both ultrasound cavitation and cryolipolysis are safe and effective for the reduction of abdominal fat thickness and for abdominal contouring. © 2015 The Australasian College of Dermatologists.

Degradation of reactive orange 4 dye using hydrodynamic cavitation based hybrid techniques.

Science.gov (United States)

Gore, Mohan M; Saharan, Virendra Kumar; Pinjari, Dipak V; Chavan, Prakash V; Pandit, Aniruddha B

2014-05-01

In the present work, degradation of reactive orange 4 dye (RO4) has been investigated using hydrodynamic cavitation (HC) and in combination with other AOP's. In the hybrid techniques, combination of hydrodynamic cavitation and other oxidizing agents such as H2O2 and ozone have been used to get the enhanced degradation efficiency through HC device. The hydrodynamic cavitation was first optimized in terms of different operating parameters such as operating inlet pressure, cavitation number and pH of the operating medium to get the maximum degradation of RO4. Following the optimization of HC parameters, the degradation of RO4 was carried out using the combination of HC with H2O2 and ozone. It has been found that the efficiency of the HC can be improved significantly by combining it with H2O2 and ozone. The mineralization rate of RO4 increases considerably with 14.67% mineralization taking place using HC alone increases to 31.90% by combining it with H2O2 and further increases to 76.25% through the combination of HC and ozone. The synergetic coefficient of greater than one for the hybrid processes of HC+H2O2 and HC+Ozone has suggested that the combination of HC with other oxidizing agents is better than the individual processes for the degradation of dye effluent containing RO4. The combination of HC with ozone proves to be the most energy efficient method for the degradation of RO4 as compared to HC alone and the hybrid process of HC and H2O2. Copyright © 2013 Elsevier B.V. All rights reserved.

Interactions of Inertial Cavitation Bubbles with Stratum Corneum Lipid Bilayers during Low-Frequency Sonophoresis

OpenAIRE

Tezel, Ahmet; Mitragotri, Samir

2003-01-01

Interactions of acoustic cavitation bubbles with biological tissues play an important role in biomedical applications of ultrasound. Acoustic cavitation plays a particularly important role in enhancing transdermal transport of macromolecules, thereby offering a noninvasive mode of drug delivery (sonophoresis). Ultrasound-enhanced transdermal transport is mediated by inertial cavitation, where collapses of cavitation bubbles microscopically disrupt the lipid bilayers of the stratum corneum. In...

Radiation induced cavitation: A possible phenomenon in liquid targets?

Energy Technology Data Exchange (ETDEWEB)

West, C.D.

1998-07-01

The proposed design of a new, short-pulse spallation neutron source includes a liquid mercury target irradiated with a 1 GeV proton beam. This paper explores the possibility that cavitation bubbles may be formed in the mercury and briefly discusses some design features that could avoid harmful effects should cavitation take place.

Radiation induced cavitation: A possible phenomenon in liquid targets?

International Nuclear Information System (INIS)

West, C.D.

1998-01-01

The proposed design of a new, short-pulse spallation neutron source includes a liquid mercury target irradiated with a 1 GeV proton beam. This paper explores the possibility that cavitation bubbles may be formed in the mercury and briefly discusses some design features that could avoid harmful effects should cavitation take place

Radiographic display of carious lesions and cavitation in approximal surfaces

DEFF Research Database (Denmark)

Wenzel, Ann

2014-01-01

cavitation in approximal surfaces. Nonetheless, there are several drawbacks with CBCT, such as radiation dose, costs and imaging artefacts. Therefore, CBCT cannot be advocated at current as a primary radiographic examination with the aim of diagnosing cavitated carious lesions. Conclusions. Bitewing...

Acoustic cavitation in 1-butyl-3-methylimidazolium bis(triflluoromethyl-sulfonyl)imide based ionic liquid.

Science.gov (United States)

Merouani, Slimane; Hamdaoui, Oualid; Haddad, Boumediene

2018-03-01

In this work, a comparison between the temperatures/pressures within acoustic cavitation bubble in an imidazolium-based room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium bis(triflluoromethyl-sulfonyl)imide ([BMIM][NTf 2 ]), and in water has been made for a wide range of cavitation parameters including frequency (140-1000kHz), acoustic intensity (0.5-1Wcm -2 ), liquid temperature (20-50°C) and external static pressure (0.7-1.5atm). The used cavitation model takes into account the liquid compressibility as well as the surface tension and the viscosity of the medium. It was found that the bubble temperatures and pressures were always much higher in the ionic liquid compared to those predicted in water. The valuable effect of [BMIM][NTf 2 ] on the bubble temperature was more pronounced at higher acoustic intensity and liquid temperature and lower frequency and external static pressure. However, confrontation between the predicted and the experimental estimated temperatures in ionic liquids showed an opposite trend as the temperatures measured in some pure ionic liquids are of the same order as those observed in water. The injection of liquid droplets into cavitation bubbles, the pyrolysis of ionic liquids at the bubble-solution interface as well as the lower number of collapsing bubbles in the ionic liquid may be the responsible for the lower measured bubble temperatures in ionic liquids, as compared with water. Copyright © 2017 Elsevier B.V. All rights reserved.

Cavitation and primary atomization in real injectors at low injection pressure condition

Science.gov (United States)

Dumouchel, Christophe; Leboucher, Nicolas; Lisiecki, Denis

2013-06-01

This experimental work investigates the influence of the geometry of GDI devices on primary atomization processes under low injection pressure and reduced back pressure. These pressure conditions ensure cavitating flows and observable atomization processes. Measurements include mass flux, structure velocity from high-speed visualizations and spray characterization with a laser diffraction technique. Super-cavitation regime and cavitation string, which have their own influence on the mass flux, develop independently in different injector regions. These regimes impact the flow pattern in the orifice and the subsequent atomization process. A possible interaction between cavitation string and super-cavitation is found to promote a hydraulic-flip-like regime and to deteriorate atomization quality. As far as the geometry of the injector is concerned, the profile of the orifice inlet and the roughness of the sac volume region are found to be important geometrical characteristics.

Study on cavitation effect of mechanical seals with laser-textured porous surface

Science.gov (United States)

Liu, T.; Chen, H. l.; Liu, Y. H.; Wang, Q.; Liu, Z. B.; Hou, D. H.

2012-11-01

Study on the mechanisms underlying generation of hydrodynamic pressure effect associated with laser-textured porous surface on mechanical seal, is the key to seal and lubricant properties. The theory model of mechanical seals with laser-textured porous surface (LES-MS) based on cavitation model was established. The LST-MS was calculated and analyzed by using Fluent software with full cavitation model and non-cavitation model and film thickness was predicted by the dynamic mesh technique. The results indicate that the effect of hydrodynamic pressure and cavitation are the important reasons to generate liquid film opening force on LST-MS; Cavitation effect can enhance hydrodynamic pressure effect of LST-MS; The thickness of liquid film could be well predicted with the method of dynamic mesh technique on Fluent and it becomes larger as the increasing of shaft speed and the decreasing of pressure.

Study on cavitation effect of mechanical seals with laser-textured porous surface

International Nuclear Information System (INIS)

Liu, T; Chen, H l; Liu, Y H; Wang, Q; Liu, Z B; Hou, D H

2012-01-01

Study on the mechanisms underlying generation of hydrodynamic pressure effect associated with laser-textured porous surface on mechanical seal, is the key to seal and lubricant properties. The theory model of mechanical seals with laser-textured porous surface (LES-MS) based on cavitation model was established. The LST-MS was calculated and analyzed by using Fluent software with full cavitation model and non-cavitation model and film thickness was predicted by the dynamic mesh technique. The results indicate that the effect of hydrodynamic pressure and cavitation are the important reasons to generate liquid film opening force on LST-MS; Cavitation effect can enhance hydrodynamic pressure effect of LST-MS; The thickness of liquid film could be well predicted with the method of dynamic mesh technique on Fluent and it becomes larger as the increasing of shaft speed and the decreasing of pressure.

Homogenization-assisted cavitation hybrid rotation extraction and macroporous resin enrichment of dihydroquercetin from Larix gmelinii.

Science.gov (United States)

Xia, Yu; Wang, Yinhang; Li, Wei; Ma, Chunhui; Liu, Shouxin

2017-12-01

Cavitation hybrid rotation, which was and is still looked upon as an unavoidable nuisance in the flow systems, for extraction processing intensification of active chemical compounds from natural products. In this study, a homogenization-assisted cavitation hybrid rotation extraction method was applied to extract dihydroquercetin (DHQ) from larch (Larix gmelinii) wood root. The extraction parameters were optimized in single factor experiments with the DHQ extraction yields as the response values. The optimum conditions were as follows: number of extractions, three; ethanol volume fraction for the extraction, 60%; liquid-solid ratio for homogenization, 10mL/g; homogenization time, 8min; liquid-solid ratio for cavitation extraction, 9mL/g, and cavitation extraction time, 35min. Under these conditions, the DHQ content in extract was 4.50±0.02mg/g, and the extraction efficiency was higher than those of traditional techniques. Cavitation can be effectively used to improve the extraction rate by increasing the mass transfer rates and possible rupture of cell wall due to formation of microcavities leading to higher product yields with reduced processing time and solvent consumption. After the extraction process, macroporous resin column chromatography was used to concentrate and purify the DHQ. Three resins were selected from fifteen macroporous resins for further investigation of their performance. Among these resins, AB-8 resin exhibited relatively better adsorption capacities and desorption ratios for DHQ. The ethanol volume fraction of the solutions for sample loading and desorption, and flow rates for loading and desorption were optimized for the macroporous resin column chromatography. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of antihypertensive treatment on progression of incipient diabetic nephropathy

DEFF Research Database (Denmark)

Christensen, Cramer; Mogensen, C E

1985-01-01

of urinary albumin excretion before and during 2.6 years +/- 1.0 (SD) of treatment. The blood pressure was depressed by the treatment (systolic blood pressure from 135 mm Hg +/- 8.6 to 124 mm Hg +/- 6.2, NS; mean blood pressure from 107 mm Hg +/- 7.6 to 97 mm Hg +/- 3.4, 2p less than 0.05; diastolic blood......The aim of the study was to clarify whether antihypertensive treatment with a selective beta blocker would have an effect on the progression rate of kidney disease in patients with incipient diabetic nephropathy. Six male patients with juvenile-onset diabetes with incipient nephropathy (urinary...... albumin excretion above 15 micrograms/min and total protein excretion below 0.5 g/24 hr) were treated with metoprolol (200 mg daily). At the start of the antihypertensive treatment the mean age was 32 years +/- 4.2 (SD). The patients were followed a mean 5.4 years +/- 3.1 (SD) with repeated measurements...

Early diagnosis of incipient caries based on non-invasive lasers

Science.gov (United States)

Velescu, A.; Todea, C.; Vitez, B.

2016-03-01

AIM: The aim of this study is to detect incipient caries and enamel demineralization using laser fluorescence.This serves only as an auxilary aid to identify and to monitor the development of these lesions. MATERIALS AND METHODS: 6 patients were involved in this study, three females and three male. Each patient underwent a professional cleaning, visual examination of the oral cavity, and then direct inspection using DiagnoCam and DIAGNOdent. After data recording each patient was submitted to retro-alveolar X-ray on teeth that were detected with enamel lesions. All data was collected and analyzed statistically. RESULTS: Of 36 areas considered in clinically healthy, 24 carious surfaces were found using laser fluorescence, a totally non-invasive method for detecting incipient carious lesions compared with the radiographic examination. CONCLUSIONS: This method has good applicability for patients because it improves treatment plan by early detection of caries and involves less fear for anxious patients and children.

Compressible cavitation with stochastic field method

Science.gov (United States)

Class, Andreas; Dumond, Julien

2012-11-01

Non-linear phenomena can often be well described using probability density functions (pdf) and pdf transport models. Traditionally the simulation of pdf transport requires Monte-Carlo codes based on Lagrange particles or prescribed pdf assumptions including binning techniques. Recently, in the field of combustion, a novel formulation called the stochastic field method solving pdf transport based on Euler fields has been proposed which eliminates the necessity to mix Euler and Lagrange techniques or prescribed pdf assumptions. In the present work, part of the PhD Design and analysis of a Passive Outflow Reducer relying on cavitation, a first application of the stochastic field method to multi-phase flow and in particular to cavitating flow is presented. The application considered is a nozzle subjected to high velocity flow so that sheet cavitation is observed near the nozzle surface in the divergent section. It is demonstrated that the stochastic field formulation captures the wide range of pdf shapes present at different locations. The method is compatible with finite-volume codes where all existing physical models available for Lagrange techniques, presumed pdf or binning methods can be easily extended to the stochastic field formulation.

Determination and microscopic study of incipient defects in irradiated power reactor fuel rods. Final report

International Nuclear Information System (INIS)

Pasupathi, V.; Perrin, J.S.; Roberts, E.

1978-05-01

This report presents the results of nondestructive and destructive examinations carried out on the Point Beach-1 (PWR) and Dresden-3 (BWR) candidate fuel rods selected for the study of pellet-clad interaction (PCI) induced incipient defects. In addition, the report includes results of examination of sections from Oskarshamn-1 (BWR) fuel rods. Eddy current examination of Point Beach-1 rods showed indications of possible incipient defects in the fuel rods. The profilometry and the gamma scan data also indicated that the source of the eddy current indications may be incipient defects. No failed rods or rods with incipient failure were found in the sample from Point Beach-1. Despite the lack of success in finding incipient defects and filed rods, the mechanism for fuel rod failures in Point Beach-1 is postulated to be PCI-related, with high startup rates and fuel handling being the key elements. Nine out of the 10 candidate fuel rods from Dresden-3 (BWR) were failed, and all the failed rods had leaked water so that the initial mechanism was observed. Examination of clad inner surfaces of the specimens from failed and unfailed rods showed fuel deposits of widely varying appearance. The deposits were found to contain uranium, cesium, and tellurium. Transmission electron microscopy of clad specimens showed evidence of microscopic strain. Metallographic examination of fuel pellets from the peak transient power location showed extensive grain boundary separation and axial movement of the fuel indicative of rapid release of fission products. Examination of Oskarshamn clad specimens did not show any stress corrosion crack (SCC) type defects. The defects found in the examinations appear to be related to secondary hydriding. The clad inner surface of the Oskarshamn specimens also showed uranium-rich deposits of varying features

Analysis of hydrodynamical pressure of cavitation flow on the boundary surface

International Nuclear Information System (INIS)

Volin, V.E.; Donchenko, E.G.; Chepajkin, G.A.; Lunatsi, E.D.; Chernishov, P.S.; Shvartser, A.L.

1976-01-01

This paper substantiates the necessity of receiving test data for creation of the methods of cavitation impact impulses on the hydraulic machines and hydraulic structures. The paper describes the methodics of experimental research of intensity of impact cavitation impulses on the elements of flowing canals at different regimes of operation; the method of determining the expected erosion in flowing canals; the method of measuring the parameters of cavitation impacts on the wall of flowing canals with the use of easily damaged varnished coverings, piezo-electric pressure transducers and amplitude and spectrum analysators. The form of a separate cavitation impact is established, the sequence of impact frequency is determined and the amplitude spectra of impacts are obtained. The analysis of test results is given

Research on axial thrust of the waterjet pump based on CFD under cavitation conditions

International Nuclear Information System (INIS)

Shen, Z H; Pan, Z Y

2015-01-01

Based on RANS equations, performance of a contra-rotating axial-flow waterjet pump without hydrodynamic cavitation state had been obtained combined with shear stress transport turbulence model. Its cavitation hydrodynamic performance was calculated and analysed with mixture homogeneous flow cavitation model based on Rayleigh-Plesset equations. The results shows that the cavitation causes axial thrust of waterjet pump to drop. Furthermore, axial thrust and head cavitation characteristic curve is similar. However, the drop point of the axial thrust is postponed by 5.1% comparing with one of head, and the critical point of the axial thrust is postponed by 2.6%

Research on axial thrust of the waterjet pump based on CFD under cavitation conditions

Science.gov (United States)

Shen, Z. H.; Pan, Z. Y.

2015-01-01

Based on RANS equations, performance of a contra-rotating axial-flow waterjet pump without hydrodynamic cavitation state had been obtained combined with shear stress transport turbulence model. Its cavitation hydrodynamic performance was calculated and analysed with mixture homogeneous flow cavitation model based on Rayleigh-Plesset equations. The results shows that the cavitation causes axial thrust of waterjet pump to drop. Furthermore, axial thrust and head cavitation characteristic curve is similar. However, the drop point of the axial thrust is postponed by 5.1% comparing with one of head, and the critical point of the axial thrust is postponed by 2.6%.

URANS simulations of the tip-leakage cavitating flow with verification and validation procedures

Science.gov (United States)

Cheng, Huai-yu; Long, Xin-ping; Liang, Yun-zhi; Long, Yun; Ji, Bin

2018-04-01

In the present paper, the Vortex Identified Zwart-Gerber-Belamri (VIZGB) cavitation model coupled with the SST-CC turbulence model is used to investigate the unsteady tip-leakage cavitating flow induced by a NACA0009 hydrofoil. A qualitative comparison between the numerical and experimental results is made. In order to quantitatively evaluate the reliability of the numerical data, the verification and validation (V&V) procedures are used in the present paper. Errors of numerical results are estimated with seven error estimators based on the Richardson extrapolation method. It is shown that though a strict validation cannot be achieved, a reasonable prediction of the gross characteristics of the tip-leakage cavitating flow can be obtained. Based on the numerical results, the influence of the cavitation on the tip-leakage vortex (TLV) is discussed, which indicates that the cavitation accelerates the fusion of the TLV and the tip-separation vortex (TSV). Moreover, the trajectory of the TLV, when the cavitation occurs, is close to the side wall.

Cavitation behavior observed in three monoleaflet mechanical heart valves under accelerated testing conditions.

Science.gov (United States)

Lo, Chi-Wen; Liu, Jia-Shing; Li, Chi-Pei; Lu, Po-Chien; Hwang, Ned H

2008-01-01

Accelerated testing provides a substantial amount of data on mechanical heart valve durability in a short period of time, but such conditions may not accurately reflect in vivo performance. Cavitation, which occurs during mechanical heart valve closure when local flow field pressure decreases below vapor pressure, is thought to play a role in valve damage under accelerated conditions. The underlying flow dynamics and mechanisms behind cavitation bubble formation are poorly understood. Under physiologic conditions, random perivalvular cavitation is difficult to capture. We applied accelerated testing at a pulse rate of 600 bpm and transvalvular pressure of 120 mm Hg, with synchronized videographs and high-frequency pressure measurements, to study cavitation of the Medtronic Hall Standard (MHS), Medtronic Hall D-16 (MHD), and Omni Carbon (OC) valves. Results showed cavitation bubbles between 340 and 360 micros after leaflet/housing impact of the MHS, MHD, and OC valves, intensified by significant leaflet rebound. Squeeze flow, Venturi, and water hammer effects each contributed to cavitation, depending on valve design.

Pressure Transient Model of Water-Hydraulic Pipelines with Cavitation

Directory of Open Access Journals (Sweden)

Dan Jiang

2018-03-01

Full Text Available Transient pressure investigation of water-hydraulic pipelines is a challenge in the fluid transmission field, since the flow continuity equation and momentum equation are partial differential, and the vaporous cavitation has high dynamics; the frictional force caused by fluid viscosity is especially uncertain. In this study, due to the different transient pressure dynamics in upstream and downstream pipelines, the finite difference method (FDM is adopted to handle pressure transients with and without cavitation, as well as steady friction and frequency-dependent unsteady friction. Different from the traditional method of characteristics (MOC, the FDM is advantageous in terms of the simple and convenient computation. Furthermore, the mechanism of cavitation growth and collapse are captured both upstream and downstream of the water-hydraulic pipeline, i.e., the cavitation start time, the end time, the duration, the maximum volume, and the corresponding time points. By referring to the experimental results of two previous works, the comparative simulation results of two computation methods are verified in experimental water-hydraulic pipelines, which indicates that the finite difference method shows better data consistency than the MOC.

Incipient multiple fault diagnosis in real time with applications to large-scale systems

International Nuclear Information System (INIS)

Chung, H.Y.; Bien, Z.; Park, J.H.; Seon, P.H.

1994-01-01

By using a modified signed directed graph (SDG) together with the distributed artificial neutral networks and a knowledge-based system, a method of incipient multi-fault diagnosis is presented for large-scale physical systems with complex pipes and instrumentations such as valves, actuators, sensors, and controllers. The proposed method is designed so as to (1) make a real-time incipient fault diagnosis possible for large-scale systems, (2) perform the fault diagnosis not only in the steady-state case but also in the transient case as well by using a concept of fault propagation time, which is newly adopted in the SDG model, (3) provide with highly reliable diagnosis results and explanation capability of faults diagnosed as in an expert system, and (4) diagnose the pipe damage such as leaking, break, or throttling. This method is applied for diagnosis of a pressurizer in the Kori Nuclear Power Plant (NPP) unit 2 in Korea under a transient condition, and its result is reported to show satisfactory performance of the method for the incipient multi-fault diagnosis of such a large-scale system in a real-time manner

Numerical investigation of the inertial cavitation threshold under multi-frequency ultrasound.

Science.gov (United States)

Suo, Dingjie; Govind, Bala; Zhang, Shengqi; Jing, Yun

2018-03-01

Through the introduction of multi-frequency sonication in High Intensity Focused Ultrasound (HIFU), enhancement of efficiency has been noted in several applications including thrombolysis, tissue ablation, sonochemistry, and sonoluminescence. One key experimental observation is that multi-frequency ultrasound can help lower the inertial cavitation threshold, thereby improving the power efficiency. However, this has not been well corroborated by the theory. In this paper, a numerical investigation on the inertial cavitation threshold of microbubbles (MBs) under multi-frequency ultrasound irradiation is conducted. The relationships between the cavitation threshold and MB size at various frequencies and in different media are investigated. The results of single-, dual and triple frequency sonication show reduced inertial cavitation thresholds by introducing additional frequencies which is consistent with previous experimental work. In addition, no significant difference is observed between dual frequency sonication with various frequency differences. This study, not only reaffirms the benefit of using multi-frequency ultrasound for various applications, but also provides a possible route for optimizing ultrasound excitations for initiating inertial cavitation. Copyright © 2017 Elsevier B.V. All rights reserved.

Cavitational boiling of liquids

International Nuclear Information System (INIS)

Kostyuk, V.V.; Berlin, I.I.; Borisov, N.N.; Karpyshev, A.V.

1986-01-01

Transition boiling is a term usually denoting the segment of boiling curve 1-2, where the heat flux, q, decreases as the temperature head, ΔT/sub w/=T/sub w/-T/sub s/, increases. Transition boiling is the subject of numerous papers. Whereas most researchers have studied transition boiling of saturated liquids the authors studied for many years transition boiling of liquids subcooled to the saturation temperature. At high values of subcooling, ΔT/sub sub/=T/sub s/-T/sub 1/, an anomalous dependence of the heat flux density on the temperature head was detected. Unlike a conventional boiling curve, where a single heat flux maximum occurs, another maximum is seen in the transition boiling segment, the boiling being accompanied by strong noise. The authors refer to this kind of boiling as cavitational. This process is largely similar to noisy boiling of helium-II. This article reports experimental findings for cavitational boiling of water, ethanol, freon-113 and noisy boiling of helium-II

One-way-coupling simulation of cavitation accompanied by high-speed droplet impact

Energy Technology Data Exchange (ETDEWEB)

Kondo, Tomoki; Ando, Keita, E-mail: kando@mech.keio.ac.jp [Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)

2016-03-15

Erosion due to high-speed droplet impact is a crucial issue in industrial applications. The erosion is caused by the water-hammer loading on material surfaces and possibly by the reloading from collapsing cavitation bubbles that appear within the droplet. Here, we simulate the dynamics of cavitation bubbles accompanied by high-speed droplet impact against a deformable wall in order to see whether the bubble collapse is violent enough to give rise to cavitation erosion on the wall. The evolution of pressure waves in a single water (or gelatin) droplet to collide with a deformable wall at speed up to 110 m/s is inferred from simulations of multicomponent Euler flow where phase changes are not permitted. Then, we examine the dynamics of cavitation bubbles nucleated from micron/submicron-sized gas bubble nuclei that are supposed to exist inside the droplet. For simplicity, we perform Rayleigh–Plesset-type calculations in a one-way-coupling manner, namely, the bubble dynamics are determined according to the pressure variation obtained from the Euler flow simulation. In the simulation, the preexisting bubble nuclei whose size is either micron or submicron show large growth to submillimeters because tension inside the droplet is obtained through interaction of the pressure waves and the droplet interface; this supports the possibility of having cavitation due to the droplet impact. It is also found, in particular, for the case of cavitation arising from very small nuclei such as nanobubbles, that radiated pressure from the cavitation bubble collapse can overwhelm the water-hammer pressure directly created by the impact. Hence, cavitation may need to be accounted for when it comes to discussing erosion in the droplet impact problem.

Combined treatment technology based on synergism between hydrodynamic cavitation and advanced oxidation processes.

Science.gov (United States)

Gogate, Parag R; Patil, Pankaj N

2015-07-01

The present work highlights the novel approach of combination of hydrodynamic cavitation and advanced oxidation processes for wastewater treatment. The initial part of the work concentrates on the critical analysis of the literature related to the combined approaches based on hydrodynamic cavitation followed by a case study of triazophos degradation using different approaches. The analysis of different combinations based on hydrodynamic cavitation with the Fenton chemistry, advanced Fenton chemistry, ozonation, photocatalytic oxidation, and use of hydrogen peroxide has been highlighted with recommendations for important design parameters. Subsequently degradation of triazophos pesticide in aqueous solution (20 ppm solution of commercially available triazophos pesticide) has been investigated using hydrodynamic cavitation and ozonation operated individually and in combination for the first time. Effect of different operating parameters like inlet pressure (1-8 bar) and initial pH (2.5-8) have been investigated initially. The effect of addition of Fenton's reagent at different loadings on the extent of degradation has also been investigated. The combined method of hydrodynamic cavitation and ozone has been studied using two approaches of injecting ozone in the solution tank and at the orifice (at the flow rate of 0.576 g/h and 1.95 g/h). About 50% degradation of triazophos was achieved by hydrodynamic cavitation alone under optimized operating parameters. About 80% degradation of triazophos was achieved by combination of hydrodynamic cavitation and Fenton's reagent whereas complete degradation was achieved using combination of hydrodynamic cavitation and ozonation. TOC removal of 96% was also obtained for the combination of ozone and hydrodynamic cavitation making it the best treatment strategy for removal of triazophos. Copyright © 2014 Elsevier B.V. All rights reserved.

Development of an Acoustic Localization Method for Cavitation Experiments in Reverberant Environments

Science.gov (United States)

Ranjeva, Minna; Thompson, Lee; Perlitz, Daniel; Bonness, William; Capone, Dean; Elbing, Brian

2011-11-01

Cavitation is a major concern for the US Navy since it can cause ship damage and produce unwanted noise. The ability to precisely locate cavitation onset in laboratory scale experiments is essential for proper design that will minimize this undesired phenomenon. Measuring the cavitation onset is more accurately determined acoustically than visually. However, if other parts of the model begin to cavitate prior to the component of interest the acoustic data is contaminated with spurious noise. Consequently, cavitation onset is widely determined by optically locating the event of interest. The current research effort aims at developing an acoustic localization scheme for reverberant environments such as water tunnels. Currently cavitation bubbles are being induced in a static water tank with a laser, allowing the localization techniques to be refined with the bubble at a known location. The source is located with the use of acoustic data collected with hydrophones and analyzed using signal processing techniques. To verify the accuracy of the acoustic scheme, the events are simultaneously monitored visually with the use of a high speed camera. Once refined testing will be conducted in a water tunnel. This research was sponsored by the Naval Engineering Education Center (NEEC).

Fundamental study on cavitation erosion in liquid metal. Effect of liquid parameter on cavitation erosion in liquid metals (Joint research)

International Nuclear Information System (INIS)

Hattori, Shuji; Kurachi, Hiroaki; Inoue, Fumitaka; Watashi, Katsumi; Tsukimori, Kazuyuki; Yada, Hiroki; Hashimoto, Takashi

2009-02-01

Cavitation erosion, which possibly occurs on the surfaces of fluid machineries and components contacting flowing liquid and causes sponge-like damage on the material surface, is important problem, since it may become the cause of performance deduction, life shortening, noise, vibration of mechanical components and moreover failure of machine. Research on cavitation erosion in liquid metal is very important to confirm the safety of fast breeder reactor using sodium coolant and to avoid serious damage of the target vessel of spallation neutron source containing liquid-mercury. But the research on cavitation erosion in liquid metal has been hardly performed because of its specially in comparison with that in water. In this study, a cavitation erosion test apparatus was developed to carry out the erosion tests in low-temperature liquid metals. Cavitation erosion tests were carried out in liquid lead-bismuth alloy and in deionized water. We discuss the effect of liquid parameters and temperature effects on the erosion rate. We reach to the following conclusions. The erosion rate was evaluated in terms of a relative temperature which was defind as the percentage between freezing and boiling points. At 14degC relative temperature, the erosion rate is 10 times in lead-bismuth alloy, and 2 to 5 times in sodium, compared with that in deionized water. At 14degC relative temperature, the erosion rate can be evaluated in terms of the following parameter. 1 / (1/ρ L /C L +1/ρ S C S )√ρ L . Where ρ is the material density and c is the velocity of sound, L and S denote liquid and solid. In the relative temperature between 14 and 30degC, the temperature dependence on the erosion rate is due to the increase in vapor pressure. (author)

Biodiesel production through hydrodynamic cavitation and performance testing

Energy Technology Data Exchange (ETDEWEB)

Pal, Amit; Verma, Ashish; Kachhwaha, S.S.; Maji, S. [Department of Mechanical Engineering, Delhi College of Engineering, Bawana Road, Delhi 110042 (India)

2010-03-15

This paper presents the details of development of a biodiesel production test rig based on hydrodynamic cavitation followed by results of experimental investigation carried out on a four cylinder, direct injection water cooled diesel engine operating on diesel and biodiesel blend of Citrullus colocyntis (Thumba) oil. The experiment covers a wide range of engine rpm. Results show that biodiesel of Thumba oil produced through hydrodynamic cavitation technique can be used as an alternative fuel with better performance and lower emissions compared to diesel. The most significant conclusions are that (1) Biodiesel production through hydrodynamic cavitation technique seems to be a simple, efficient, time saving, eco-friendly and industrially viable process. (2) 30% biodiesel blend of Thumba oil shows relatively higher brake power, brake thermal efficiency, reduced bsfc and smoke opacity with favourable p-{theta} diagram as compared to diesel. (author)

Cavitation erosion resistance of diamond-like carbon coating on stainless steel

Energy Technology Data Exchange (ETDEWEB)

Cheng, Feng; Jiang, Shuyun, E-mail: jiangshy@seu.edu.cn

2014-02-15

Two diamond-like carbon (DLC) coatings are prepared on stainless steel 304 by cathodic arc plasma deposition technology at different substrate bias voltages and arc currents (−200 V/80 A, labeled DLC-1, and −100 V/60 A, labeled DLC-2). Cavitation tests are performed by using a rotating-disk test rig to explore the cavitation erosion resistance of the DLC coating. The mass losses, surface morphologies, chemical compositions and the phase constituents of the specimens after cavitation tests are examined by using digital balance, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The results indicate that the DLC-2 coatings can elongate the incubation period of stainless steel, leading to an excellent cavitation erosion resistance as compared to the untreated stainless steel specimens. After duration of 100 h cavitation test, serious damaged surfaces and plenty of scratches can be observed on the surfaces of the stainless steel specimens, while only a few grooves and tiny pits are observed on the DLC-2 coatings. It is concluded that, decreasing micro defects and increasing adhesion can reduce the delamination of DLC coating, and the erosion continues in the stainless steel substrate after DLC coating failure, and the eroded surface of the substrate is subjected to the combined action from cavitation erosion and slurry erosion.

Cavitation Nuclei: Experiments and Theory

DEFF Research Database (Denmark)

Mørch, Knud Aage

2009-01-01

The Swedish astrophysicist and Nobel Prize winner Hannes Alfven said: Theories come and go - the experiment is here forever. Often a theory, which we set up to describe an observed physical phenomenon, suffers from the lack of knowledge of decisive parameters, and therefore at best the theory...... becomes insufficient. Contrary, the experiment always reveals nature itself, though at prevailing experimental conditions. With essential parameters being out of control and even maybe unidentified, apparently similar experiments may deviate way beyond our expectations. However, these discrepancies offer...... us a chance to reflect on the character of the unknown parameters. In this way non-concordant experimental results may hold the key to the development of better theories - and to new experiments for the testing of their validity. Cavitation and cavitation nuclei are phenomena of that character....

The Specialist Committee on Cavitation Induced Pressures, Final Report and Recommendations to the 23rd ITTC

DEFF Research Database (Denmark)

Friesch, J.; Kim, K.-H.; Andersen, Poul

2002-01-01

General Technical Conclusions Propeller-excited hull pressure fluctuations are strongly influenced by intermittence of sheet cavitation, the dynamics of tip vortex cavitation, and the statistical properties of the cavitation. On modern propellers, tip vortex cavitation may be even more important ...

Determination of acoustic characteristics of pipe cavitation

International Nuclear Information System (INIS)

Loof, J.-P. de; Leducq, Daniel

1979-01-01

The subject of this report is an experimental investigation of cavitation as a source of noise within the audible and dangerous frequency ranges for industrial plant and equipment. The first results showed the noise-generating process to be comparable to that of a shock wave developing immediately after the cavitation area, propagating at very close to flow velocity and dying-down after a length equivalent to two or three diameters. Most of the energy is concentrated in the low-frequency range of the spectrum (i.e. up to 200 Hz) [fr

Cavitation performance improvement of high specific speed mixed-flow pump

International Nuclear Information System (INIS)

Chen, T; Sun, Y B; Wu, D Z; Wang, L Q

2012-01-01

Cavitation performance improvement of large hydraulic machinery such as pump and turbine has been a hot topic for decades. During the design process of the pumps, in order to minimize size, weight and cost centrifugal and mixed-flow pump impellers are required to operate at the highest possible rotational speed. The rotational speed is limited by the phenomenon of cavitation. The hydraulic model of high-speed mixed-flow pump with large flow rate and high pumping head, which was designed based on the traditional method, always involves poor cavitation performance. In this paper, on the basis of the same hydraulic design parameters, two hydraulic models of high-speed mixed-flow pump were designed by using different methods, in order to investigate the cavitation and hydraulic performance of the two models, the method of computational fluid dynamics (CFD) was adopted for internal flow simulation of the high specific speed mixed-flow pump. Based on the results of numerical simulation, the influences of impeller parameters and three-dimensional configuration on pressure distribution of the blades' suction surfaces were analyzed. The numerical simulation results shows a better pressure distribution and lower pressure drop around the leading edge of the improved model. The research results could provide references to the design and optimization of the anti-cavitation blade.

Gauging the likelihood of stable cavitation from ultrasound contrast agents.

Science.gov (United States)

Bader, Kenneth B; Holland, Christy K

2013-01-07

The mechanical index (MI) was formulated to gauge the likelihood of adverse bioeffects from inertial cavitation. However, the MI formulation did not consider bubble activity from stable cavitation. This type of bubble activity can be readily nucleated from ultrasound contrast agents (UCAs) and has the potential to promote beneficial bioeffects. Here, the presence of stable cavitation is determined numerically by tracking the onset of subharmonic oscillations within a population of bubbles for frequencies up to 7 MHz and peak rarefactional pressures up to 3 MPa. In addition, the acoustic pressure rupture threshold of an UCA population was determined using the Marmottant model. The threshold for subharmonic emissions of optimally sized bubbles was found to be lower than the inertial cavitation threshold for all frequencies studied. The rupture thresholds of optimally sized UCAs were found to be lower than the threshold for subharmonic emissions for either single cycle or steady state acoustic excitations. Because the thresholds of both subharmonic emissions and UCA rupture are linearly dependent on frequency, an index of the form I(CAV) = P(r)/f (where P(r) is the peak rarefactional pressure in MPa and f is the frequency in MHz) was derived to gauge the likelihood of subharmonic emissions due to stable cavitation activity nucleated from UCAs.

Hydrodynamic cavitation as a novel approach for delignification of wheat straw for paper manufacturing.

Science.gov (United States)

Badve, Mandar P; Gogate, Parag R; Pandit, Aniruddha B; Csoka, Levente

2014-01-01

The present work deals with application of hydrodynamic cavitation for intensification of delignification of wheat straw as an essential step in the paper manufacturing process. Wheat straw was first treated with potassium hydroxide (KOH) for 48 h and subsequently alkali treated wheat straw was subjected to hydrodynamic cavitation. Hydrodynamic cavitation reactor used in the work is basically a stator and rotor assembly, where the rotor is provided with indentations and cavitational events are expected to occur on the surface of rotor as well as within the indentations. It has been observed that treatment of alkali treated wheat straw in hydrodynamic cavitation reactor for 10-15 min increases the tensile index of the synthesized paper sheets to about 50-55%, which is sufficient for paper board manufacture. The final mechanical properties of the paper can be effectively managed by controlling the processing parameters as well as the cavitational parameters. It has also been established that hydrodynamic cavitation proves to be an effective method over other standard digestion techniques of delignification in terms of electrical energy requirements as well as the required time for processing. Overall, the work is first of its kind application of hydrodynamic cavitation for enhancing the effectiveness of delignification and presents novel results of significant interest to the paper and pulp industry opening an entirely new area of application of cavitational reactors. Copyright © 2013 Elsevier B.V. All rights reserved.

A Novel Event-Based Incipient Slip Detection Using Dynamic Active-Pixel Vision Sensor (DAVIS).

Science.gov (United States)

Rigi, Amin; Baghaei Naeini, Fariborz; Makris, Dimitrios; Zweiri, Yahya

2018-01-24

In this paper, a novel approach to detect incipient slip based on the contact area between a transparent silicone medium and different objects using a neuromorphic event-based vision sensor (DAVIS) is proposed. Event-based algorithms are developed to detect incipient slip, slip, stress distribution and object vibration. Thirty-seven experiments were performed on five objects with different sizes, shapes, materials and weights to compare precision and response time of the proposed approach. The proposed approach is validated by using a high speed constitutional camera (1000 FPS). The results indicate that the sensor can detect incipient slippage with an average of 44.1 ms latency in unstructured environment for various objects. It is worth mentioning that the experiments were conducted in an uncontrolled experimental environment, therefore adding high noise levels that affected results significantly. However, eleven of the experiments had a detection latency below 10 ms which shows the capability of this method. The results are very promising and show a high potential of the sensor being used for manipulation applications especially in dynamic environments.

Modeling cavitation in a rapidly changing pressure field - application to a small ultrasonic horn.

Science.gov (United States)

Žnidarčič, Anton; Mettin, Robert; Dular, Matevž

2015-01-01

Ultrasonic horn transducers are frequently used in applications of acoustic cavitation in liquids. It has been observed that if the horn tip is sufficiently small and driven at high amplitude, cavitation is very strong, and the tip can be covered entirely by the gas/vapor phase for longer time intervals. A peculiar dynamics of the attached cavity can emerge with expansion and collapse at a self-generated frequency in the subharmonic range, i.e. below the acoustic driving frequency. The term "acoustic supercavitation" was proposed for this type of cavitation Žnidarčič et al. (2014) [1]. We tested several established hydrodynamic cavitation models on this problem, but none of them was able to correctly predict the flow features. As a specific characteristic of such acoustic cavitation problems lies in the rapidly changing driving pressures, we present an improved approach to cavitation modeling, which does not neglect the second derivatives in the Rayleigh-Plesset equation. Comparison with measurements of acoustic supercavitation at an ultrasonic horn of 20kHz frequency revealed a good agreement in terms of cavity dynamics, cavity volume and emitted pressure pulsations. The newly developed cavitation model is particularly suited for simulation of cavitating flow in highly fluctuating driving pressure fields. Copyright © 2014 Elsevier B.V. All rights reserved.

Dynamics and noise emission of laser induced cavitation bubbles in a vortical flow field

Science.gov (United States)

Oweis, Ghanem F.; Choi, Jaehyug; Ceccio, Steven L.

2004-03-01

The sound produced by the collapse of discrete cavitation bubbles was examined. Laser-generated cavitation bubbles were produced in both a quiescent and a vortical flow. The sound produced by the collapse of the cavitation bubbles was recorded, and its spectral content was determined. It was found that the risetime of the sound pulse produced by the collapse of single, spherical cavitation bubbles in quiescent fluid exceeded that of the slew rate of the hydrophone, which is consistent with previously published results. It was found that, as collapsing bubbles were deformed by the vortical flow, the acoustic impulse of the bubbles was reduced. Collapsing nonspherical bubbles often created a sound pulse with a risetime that exceeded that of the hydrophone slew rate, although the acoustic impulse created by the bubbles was influenced largely by the degree to which the bubbles became nonspherical before collapse. The noise produced by the slow growth of cavitation bubbles in the vortex core was not detectable. These results have implications for the interpretation of hydrodynamic cavitation noise produced by vortex cavitation.

On the mechanism of explosive eruption of mount erebus volcano: the dynamics of the rupture structure in a cavitating layer

International Nuclear Information System (INIS)

Bol'shakova, E S; Kedrinskiy, V K

2016-01-01

This paper presents the results of an experimental simulation of rupture development in heavily cavitating magma melt flow in volcanic conduits and its effect on the structure of explosive volcanic eruptions. The dynamics of the state of a layer of distilled water (similar in the density of cavitation nuclei to magma melt) under shock-wave loading was studied. The experiments were performed using electromagnetic hydrodynamic shock tubes (EM HST) with maximum capacitor bank energy of up to 100 J and 5 kJ. It was found that the topology of the rupture formed on the membrane surface did not change during its development. Empirical estimates were obtained for the proportion of the capacitor bank energy expended in the development of the rupture and the characteristic time of its existence. The study revealed a number of fundamentally new physical effects in the cavity dynamics in a cavitating medium: a cavitation “boundary layer” is formed on the surface of the quasi-empty rupture, which is transformed into a cluster of high energy density upon closure of the flow. (paper)

Cavitating flow during water hammer using a generalized interface vaporous cavitation model

Science.gov (United States)

Sadafi, Mohamadhosein; Riasi, Alireza; Nourbakhsh, Seyed Ahmad

2012-10-01

In a transient flow simulation, column separation may occur when the calculated pressure head decreases to the saturated vapor pressure head in a computational grid. Abrupt valve closure or pump failure can result in a fast transient flow with column separation, potentially causing problems such as pipe failure, hydraulic equipment damage, cavitation or corrosion. This paper reports a numerical study of water hammer with column separation in a simple reservoir-pipeline-valve system and pumping station. The governing equations for two-phase transient flow in pipes are solved based on the method of characteristics (MOC) using a generalized interface vaporous cavitating model (GIVCM). The numerical results were compared with the experimental data for validation purposes, and the comparison indicated that the GIVCM describes the experimental results more accurately than the discrete vapor cavity model (DVCM). In particular, the GIVCM correlated better with the experimental data than the DVCM in terms of timing and pressure magnitude. The effects of geometric and hydraulic parameters on flow behavior in a pumping station with column separation were also investigated in this study.

Relationship between thrombolysis efficiency induced by pulsed focused ultrasound and cavitation bubble size

International Nuclear Information System (INIS)

Xu, S; Liu, X; Wang, S; Wan, M

2015-01-01

In this study, the relationship between the efficiency of pulsed focused ultrasound (FUS)-induced thrombolysis and the size distribution of cavitation bubbles has been studied. Firstly, the thrombolysis efficiency, evaluated by degree of mechanical fragmentation was investigated with varying duty cycle. Secondly, the size distribution of cavitation bubbles after the 1st, 10 3 th and 10 5 th pulse during experiments for various duty cycles was studied. It was revealed that the thrombolysis efficiency was highest when the cavitation bubble size distribution was centred around linear resonance radius of the emission frequency of the FUS transducer. Therefore, in cavitation enhanced therapeutic applications, the essential of using a pulsed FUS may be controlling the size distribution of cavitation nuclei within an active size range so as to increase the treatment efficiency. (paper)

Stress intensity factor at the tip of cladding incipient crack in RIA-simulating experiments for high-burnup PWR fuels

International Nuclear Information System (INIS)

Udagawa, Yutaka; Suzuki, Motoe; Sugiyama, Tomoyuki; Fuketa, Toyoshi

2009-01-01

RIA-simulating experiments for high-burnup PWR fuels have been performed in the NSRR, and the stress intensity factor K 1 at the tip of cladding incipient crack has been evaluated in order to investigate its validity as a PCMI failure threshold under RIA conditions. An incipient crack depth was determined by observation of metallographs. The maximum hydride-rim thickness in the cladding of the test fuel rod was regarded as the incipient crack depth in each test case. Hoop stress in the cladding periphery during the pulse power transient was calculated by the RANNS code. K 1 was calculated based on crack depth and hoop stress. According to the RANNS calculation, PCMI failure cases can be divided into two groups: failure in the elastic phase and failure in the plastic phase. In the former case, elastic deformation was predominant around the incipient crack at failure time. K 1 is available only in this case. In the latter, plastic deformation was predominant around the incipient crack at failure time. Failure in the elastic phase never occurred when K 1 was less than 17 MPa m 1/2 . For failure in the plastic phase, the plastic hoop strain of the cladding periphery at failure time clearly showed a tendency to decrease with incipient crack depth. The combination of K 1 , for failure in the elastic phase, and plastic hoop strain at failure, for failure in the plastic phase, can be an effective index of PCMI failure under RIA conditions. (author)

Laser-enhanced cavitation during high intensity focused ultrasound: An in vivo study

OpenAIRE

Cui, Huizhong; Zhang, Ti; Yang, Xinmai

2013-01-01

Laser-enhanced cavitation during high intensity focused ultrasound (HIFU) was studied in vivo using a small animal model. Laser light was employed to illuminate the sample concurrently with HIFU radiation. The resulting cavitation was detected with a passive cavitation detector. The in vivo measurements were made under different combinations of HIFU treatment depths, laser wavelengths, and HIFU durations. The results demonstrated that concurrent light illumination during HIFU has the potentia...

Development of turbopump cavitation performance test facility and the test of inducer performance

International Nuclear Information System (INIS)

Sohn, Dong Kee; Kim, Chun Tak; Yoon, Min Soo; Cha, Bong Jun; Kim, Jin Han; Yang, Soo Seok

2001-01-01

A performance test facility for turbopump inducer cavitation was developed and the inducer cavitation performance tests were performed. Major components of the performance test facility are driving unit, test section, piping, water tank, and data acquisition and control system. The maximum of testing capability of this facility are as follows: flow rate - 30kg/s; pressure - 13 bar, rotational speed - 10,000rpm. This cavitation test facility is characterized by the booster pump installed at the outlet of the pump that extends the flow rate range, and by the pressure control system that makes the line pressure down to vapor pressure. The vacuum pump is used for removing the dissolved air in the water as well as the line pressure. Performance tests were carried out and preliminary data of test model inducer were obtained. The cavitation performance test and cavitation bubble flow visualization were also made. This facility is originally designed for turbopump inducer performance test and cavitation test. However it can be applied to the pump impeller performance test in the future with little modification

Detection of cavitation inception by acoustic technique in centrifugal pumps for nuclear application

International Nuclear Information System (INIS)

Prakash, V.; Prabhakar, R.; Rao, A.S.L.K.; Kale, R.D.

1994-01-01

The primary centrifugal pumps in a pool type reactor like the proposed Prototype Fast Breeder Reactor (PFBR) are required to operate at low values of available net positive suction head due to the limited submergence available in the pool. Pump hydraulics are designed to ensure that there is no cavitation or only minimum cavitation in the pump impeller in order to minimise long term erosion damage. Rigorous cavitation tests are usually carried out during development and final testing phase and a promising cavitation detection technique lies in acoustic noise measurements on the pump. As part of PFBR pump development programme, cavitation noise measurements were initially carried out on an experimental sodium pump in a water rig to establish detection procedures. Recently cavitation noise measurements were carried out on a 1/3 scale model impeller of PFBR pump along with visual observation of impeller passages to establish a correlation between visual and acoustic technique. Accelerometer responding to structure borne noise seems to give the best result. (author). 4 refs., 6 figs

A Numerical Study of Cavitation Inception in Complex Flow Fields

Science.gov (United States)

2007-12-01

report describes DYNAFLOW’s efforts over the past three years to develop and apply innovative methods to study and model the cavitation inception in...Marjollet, Fréchou, D., Fruman, D.H., Karimi, A., Kueny, J.L., Michel, J.M., La Cavitation. Mécanismes Physiques et Aspects Industrielles

Incipient ferroelectric properties of NaTaO.sub.3./sub

Czech Academy of Sciences Publication Activity Database

Kamba, Stanislav; Goian, Veronica; Bovtun, Viktor; Nuzhnyy, Dmitry; Kempa, Martin; Spreitzer, M.; König, J.; Suvorov, D.

2012-01-01

Roč. 426, SI (2012), s. 206-214 ISSN 0015-0193 R&D Projects: GA ČR(CZ) GA202/09/0682 Institutional research plan: CEZ:AV0Z10100520 Keywords : incipient ferroelectricity * infrared and THz spectroscopy * phonons * microwave ceramics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.415, year: 2012

Improved detection of incipient anomalies via multivariate memory monitoring charts: Application to an air flow heating system

KAUST Repository

Harrou, Fouzi

2016-08-11

Detecting anomalies is important for reliable operation of several engineering systems. Multivariate statistical monitoring charts are an efficient tool for checking the quality of a process by identifying abnormalities. Principal component analysis (PCA) was shown effective in monitoring processes with highly correlated data. Traditional PCA-based methods, nevertheless, often are relatively inefficient at detecting incipient anomalies. Here, we propose a statistical approach that exploits the advantages of PCA and those of multivariate memory monitoring schemes, like the multivariate cumulative sum (MCUSUM) and multivariate exponentially weighted moving average (MEWMA) monitoring schemes to better detect incipient anomalies. Memory monitoring charts are sensitive to incipient anomalies in process mean, which significantly improve the performance of PCA method and enlarge its profitability, and to utilize these improvements in various applications. The performance of PCA-based MEWMA and MCUSUM control techniques are demonstrated and compared with traditional PCA-based monitoring methods. Using practical data gathered from a heating air-flow system, we demonstrate the greater sensitivity and efficiency of the developed method over the traditional PCA-based methods. Results indicate that the proposed techniques have potential for detecting incipient anomalies in multivariate data. © 2016 Elsevier Ltd

Tanscranial Threshold of Inertial Cavitation Induced by Diagnosticc Ultrasound and Microbubbles

NARCIS (Netherlands)

Liu, J.; Gao, S.; Porter, T.R.; Everbach, C; Shi, W.; Vignon, F.; Powers, J.; Lof, J.; Turner, J.; Xie, F.

2011-01-01

Background: Inertial cavitation may cause hazardous bioeffects whileusing ultrasound and microbubble mediated thrombolysis. The purposeof this study was to investigate the influence of ultrasound pulselength and temporal bone on inertial cavitation thresholds within the brain utilizing transtemporal

Hydrodynamic Cavitation-Assisted Synthesis of Nanocalcite

Directory of Open Access Journals (Sweden)

Shirish H. Sonawane

2010-01-01

Full Text Available A systematic study was made on the synthesis of nanocalcite using a hydrodynamic cavitation reactor. The effects of various parameters such as diameter and geometry of orifice, CO2 flow rate, and Ca(OH2 concentration were investigated. It was observed that the orifice diameter and its geometry had significant effect on the carbonation process. The reaction rate was significantly faster than that observed in a conventional carbonation process. The particle size was significantly affected by the reactor geometry. The results showed that an orifice with 5 holes of 1 mm size resulted in the particle size reduction to 37 nm. The experimental investigation reveals that hydrodynamic cavitation may be more energy efficient.

Visualization of ultrasound induced cavitation bubbles using the synchrotron x-ray Analyzer Based Imaging technique

International Nuclear Information System (INIS)

Izadifar, Zahra; Izadifar, Mohammad; Izadifar, Zohreh; Chapman, Dean; Belev, George

2014-01-01

Observing cavitation bubbles deep within tissue is very difficult. The development of a method for probing cavitation, irrespective of its location in tissues, would improve the efficiency and application of ultrasound in the clinic. A synchrotron x-ray imaging technique, which is capable of detecting cavitation bubbles induced in water by a sonochemistry system, is reported here; this could possibly be extended to the study of therapeutic ultrasound in tissues. The two different x-ray imaging techniques of Analyzer Based Imaging (ABI) and phase contrast imaging (PCI) were examined in order to detect ultrasound induced cavitation bubbles. Cavitation was not observed by PCI, however it was detectable with ABI. Acoustic cavitation was imaged at six different acoustic power levels and six different locations through the acoustic beam in water at a fixed power level. The results indicate the potential utility of this technique for cavitation studies in tissues, but it is time consuming. This may be improved by optimizing the imaging method. (paper)

Visualization of ultrasound induced cavitation bubbles using the synchrotron x-ray Analyzer Based Imaging technique.

Science.gov (United States)

Izadifar, Zahra; Belev, George; Izadifar, Mohammad; Izadifar, Zohreh; Chapman, Dean