Zeitschriftenartikel: „Cavitation nuclei“

1

d’Agostino, L., T. Pham und S. Green. „Comparison of a Cavitation Susceptibility Meter and Holography for Nuclei Detection in Liquids“. Journal of Fluids Engineering 111, Nr. 2 (01.06.1989): 197–203. http://dx.doi.org/10.1115/1.3243623.

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This work compares the results obtained from a Cavitation Susceptibility Meter (CSM) and from direct holographic observations for the detection of cavitation nuclei in tap water samples. The CSM uses a cavitating venturi tube to measure the concentration of active cavitation nuclei as a function of the pressure at the venturi throat, while the holographic system measures the nuclei concentration size distribution. Microbubbles are used as the dominant type of cavitation nuclei. The data from the two nuclei detection methods are then compared and interpreted in view of the expected dynamic behavior of microbubbles in the CSM venturi throat. Both results show that the concentration of active cavitation nuclei initially increases exponentially with the applied tension, reaches a maximum and remains nearly constant thereafter when few additional nuclei are left to cavitate. In its current configuration the CSM tends to underestimate the concentration of active cavitation nuclei and to overestimate the value of the nuclei critical pressure as a consequence of sensitivity limitations and interference effects between the cavities.

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2

Strasberg, M. „Cavitation nuclei and cavitation noise“. Journal of the Acoustical Society of America 83, S1 (Mai 1988): S39. http://dx.doi.org/10.1121/1.2025338.

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3

d’Agostino, L., und A. J. Acosta. „Separation and Surface Nuclei Effects in a Cavitation Susceptibility Meter“. Journal of Fluids Engineering 113, Nr. 4 (01.12.1991): 695–98. http://dx.doi.org/10.1115/1.2926536.

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This work is concerned with the effects of flow separation and surface nuclei on the operation of a fixed geometry Cavitation Susceptibility Meter (CSM) with laminar flow. Cavitation is induced under controlled conditions at the throat of a glass venturi tube for the measurement of the active nuclei concentration in water samples as a function of the applied tension. Both cavitation and flow velocity are monitored optically by a Laser Doppler Velocimeter. The throat pressure is determined indirectly from the upstream pressure and the local flow velocity. The results show that laminar flow separation and surface nuclei effects are the most stringent operational limitations. Separation in the diffuser increases the minimum attainable throat pressure above the susceptibility of most cavitation nuclei commonly found in technical waters. Surface nuclei can generate extensive sheet or spot cavitation at relatively high tensions even on optically finished glass surfaces. These phenomena are difficult to eliminate and bring therefore into question the practical utility of CSM’s with laminar flow and fixed geometry for the measurement of the dependence of the cavitating nuclei concentration over wide ranges of the applied tension, as required for cavitation studies.

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4

Fu, Qiang, Mengyuan Li, Xiuli Wang, Jianen Yu und Rongsheng Zhu. „Nanoscale bubble study of cavitation inception on a platinum surface using molecular dynamics simulation“. Thermal Science 24, Nr. 5 Part A (2020): 2953–63. http://dx.doi.org/10.2298/tsci180212019f.

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The transient properties of liquid argon cavitation nuclei in platinum surface were studied by means of molecular dynamics simulation. The bubble nucleation, with a certain size and stability on the wall surface, was studied by different tensile distances and different wall wettabilities. Also the parameters of cavitation nuclei development, the system pressure, and the total pressure were analysed. The stability of cavitating nucleus growth is closely related to the metastable degree of the system and the wettability of the wall. The tensile distance of the wall surface has a critical value, and stretching greater than the critical value will induce a greater degree of instability in the system, which is conducive to the growth of the cavitation nucleus. A hydrophobic wall is more conducive to the growth of a cavitation nucleus, which is beneficial to spontaneous growth among cavitated nuclei, whereas a hydrophobic exerts has an inhibitory influence on cavitation nuclei.

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5

Qiang, Fu, Zhang Benying, Zhao Yuanyuan, Zhu Rongsheng, Liu Gang und Li Mengyuan. „The Cavitation Nuclei Transient Characteristics of Lennard-Jones Fluid in Cavitation Inception“. Polish Maritime Research 25, s2 (01.08.2018): 75–84. http://dx.doi.org/10.2478/pomr-2018-0077.

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Abstract In the field of ocean engineering, cavitation is widespread, for the study of cavitation nuclei transient characteristics in cavitation inception, we applied theoretical analysis and molecular dynamics (MD) simulation to study Lennard-Jones (L-J) fluid with different initial cavitation nuclei under the NVT-constant ensemble in this manuscript. The results showed that in cavitation inception, due to the decrease of liquid local pressure, the liquid molecules would enter the cavitation nuclei, which contributed to the growth of cavitation nuclei. By using molecular potential energy, it was found that the molecular potential energy was higher in cavitation nuclei part, while the liquid molecular potential energy changes greatly at the beginning of the cavitation nuclei growth. The density of the liquid and the surface layer changes more obvious, but density of vapor in the bubble changes inconspicuously. With the growth of cavitation nuclei, the RDF peak intensity increased, the peak width narrowed and the first valley moved inner. When cavitation nuclei initial size reduced, the peak intensity reduced, the corresponding rbin increased. With the decrease of the initial cavitation nuclei, the system pressure and total energy achieved a balance longer, and correspondingly, they were smaller. In addition, at the beginning of the cavitation nuclei growth, the total energy and system pressure changed greatly.

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6

d’Agostino, Luca, und S. I. Green. „Simultaneous Cavitation Susceptibility Meter and Holographic Measurements of Nuclei in Liquids“. Journal of Fluids Engineering 114, Nr. 2 (01.06.1992): 261–67. http://dx.doi.org/10.1115/1.2910025.

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Cavitation Susceptibility Meter (CSM) and holographic measurements of cavitation nuclei distributions are compared in this paper. The CSM optically detects cavitation in water samples flowing through a venturi and relates the unstable nuclei concentration to the applied tension in the fluid. A ruby laser holographic system measures the nuclei size distribution directly. Microbubbles have been used as the dominant nuclei source. The data from the two detection schemes are correlated by accounting for the dynamic response of the cavities in the venturi throat. The active nuclei distributions predicted by the holographic data compare favorably with those measured by the CSM. Both detection methods show that the nuclei concentration rises approximately exponentially as the applied tension is increased and then, with further reduction in the pressure, tends to a nearly constant maximum due to the shortage of remaining cavitatable nuclei. The CSM consistently underestimates the concentration of active cavitation nuclei, due to limited electro-optical resolution and mutual interference effects between cavities in the venturi. The good qualitative agreement of the two techniques supports the validity of the data correlation model and clearly indicates that any practical interpretation of measured nuclei size distributions for cavitations predictions is highly dependent of the specific flow conditions. Attempts to cavitate saturated water of the California Institute of Technology Low Turbulence Water Tunnel in the CSM were unsuccessful even at the lowest attainable CSM throat pressures (about −40kPa). This is thought to be due to insufficient throat tension and, at least partially, to the short time available for cavity growth in the CSM.

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7

ITO, Yukio, Makoto YAMADA, Risaburou OBA, Yoshiaki ONISHI und Keiichi IIDAKA. „Cavitation tunnel characterized by stable cavitation-nuclei-distributions.“ Transactions of the Japan Society of Mechanical Engineers Series B 54, Nr. 502 (1988): 1222–25. http://dx.doi.org/10.1299/kikaib.54.1222.

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8

Hall, Timothy L., Alex Duryea und Hedieh Tamaddoni. „Control of cavitation through coalescence of cavitation nuclei“. Journal of the Acoustical Society of America 136, Nr. 4 (Oktober 2014): 2301. http://dx.doi.org/10.1121/1.4900326.

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9

Gindroz, B., und M. L. Billet. „Influence of the Nuclei on the Cavitation Inception for Different Types of Cavitation on Ship Propellers“. Journal of Fluids Engineering 120, Nr. 1 (01.03.1998): 171–78. http://dx.doi.org/10.1115/1.2819643.

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In order to relate nuclei size distributions with inception cavitation in cavitation facilities, a test program was conducted at the Grand Tunnel Hydrodynamique (GTH) of the Bassin d’Essais des Care`nes. The GTH, which has a complete air control system including dissolved gas and nuclei (microbubbles) control, offers the opportunity to answer this question. The tests were conducted on the three 34 mm diameter propellers used by Kuiper (1981), each of these propellers being characterized by a different cavitation type: bubble, sheet and vortex cavitation. The water nuclei content correspond to strong degassed water (maximum tension), low injection of medium size nuclei (medium tension-low content), large injection of medium size nuclei (medium tension-high content) and large injection of large nuclei (minimum tension). By injecting medium size nuclei for a low content and a high content, we can examine the influence of the number of nuclei on the cavitation inception characteristic. During all the tests, the dissolved air content was kept constant. The GTH online Cavitation Nuclei Counter (Centerbody Venturi) was used to measure both the water nuclei distribution and the liquid tension. Comparisons are made with the calibrated Centerbody Venturi, a Phases Doppler Particles Analyzer (PDPA) and Holographic measurements.

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10

Mørch, K. A. „Cavitation inception from bubble nuclei“. Interface Focus 5, Nr. 5 (06.10.2015): 20150006. http://dx.doi.org/10.1098/rsfs.2015.0006.

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The tensile strength of ordinary water such as tap water or seawater is typically well below 1 bar. It is governed by cavitation nuclei in the water, not by the tensile strength of the water itself, which is extremely high. Different models of the nuclei have been suggested over the years, 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 and associated experiments throw new light on the effects of transient pressures on the tensile strength of water, which may be notably reduced or increased by such pressure changes.

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11

Mørch, K. A. „Cavitation Nuclei: Experiments and Theory“. Journal of Hydrodynamics 21, Nr. 2 (April 2009): 176–89. http://dx.doi.org/10.1016/s1001-6058(08)60135-3.

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12

Qiang, Yan. „Effects of properties of silt particles on cavitating flow characteristics in a nozzle“. Modern Physics Letters B 32, Nr. 21 (26.07.2018): 1850242. http://dx.doi.org/10.1142/s0217984918502421.

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To research the effects of properties of silt particles on cavitating flow, silt-laden cavitation flow in one 3D nozzle is simulated. Silt mean diameters are 0.005 mm, 0.007 mm, 0.009 mm, 0.010 mm, 0.012 mm, 0.013 mm, 0.015 mm, 0.020 mm, 0.026 mm, 0.030 mm, 0.035 mm, 0.040 mm, 0.046 mm, 0.050 mm and 0.056 mm. Silt concentrations vary from 1.0% to 10%. To measure the effects of silt particles, vapor contents under pure water cavitation flow and silt-laden cavitation flow conditions are calculated and compared. Results show that silt particles first promote the development of cavitation then inhibit the evolution of cavitation with the increase of silt concentration. Silt particles promotion scope decreases gradually and inhibition span increases constantly with the increase of silt mean diameter. Cavitation nuclei, vortices, slip velocity, virtual mass force and Saffman lift force have a closed relation with the promotion of silt particles. Vortices, viscosity and silt abrasion deeply influence the inhibition of cavitation.

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13

Groß, T. F., und P. F. Pelz. „Diffusion-driven nucleation from surface nuclei in hydrodynamic cavitation“. Journal of Fluid Mechanics 830 (29.09.2017): 138–64. http://dx.doi.org/10.1017/jfm.2017.587.

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Investigations about the role of nuclei and nucleation for the inception and formation of cavitation have been part of cavitation research since Harvey et al. (J. Cell. Physiol., vol. 24 (1), 1944, pp. 1–22) postulated the existence of gas filled crevices on surfaces and particles in liquids. In a supersaturated liquid, surface nuclei produce small gas bubbles due to mass transfer of gas or themselves work as weak spots in the liquid that are necessary for a phase change under technically relevant static pressures. Although various theories and models about nuclei and nucleation have found their way into standard literature, there is a lack of experimentally validated theories that describe the process of diffusion-driven nucleation in hydrodynamic cavitation. In order to close this gap we give new theoretical insights into the physics of this nucleation mechanism at technically relevant low supersaturations validated with extensive experimental results. The nucleation rate, the number of produced bubbles per second, is proportional to the supersaturation of the liquid and shows a nonlinear dependence on the shear rate at the surface nucleus. A model for the Strouhal number as dimensionless nucleation rate is derived allowing the estimation of nucleation rates from surface nuclei in hydrodynamic cavitation. The model provides three asymptotes, being a function of Péclet number, Weber number, the supersaturation of the liquid $\unicode[STIX]{x1D701}$ and gas solubility $\unicode[STIX]{x1D6EC}$ for three different detachment mechanisms, $Sr\propto \unicode[STIX]{x1D701}\unicode[STIX]{x1D6EC}We^{n}Pe^{1/3}$ with $n=1/3,3/4,1$. The theoretical findings are in good agreement with experimental results, leading to a new assessment of the role of diffusion in cavitating flows.

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14

Meyer, R. S., M. L. Billet und J. W. Holl. „Freestream Nuclei and Traveling-Bubble Cavitation“. Journal of Fluids Engineering 114, Nr. 4 (01.12.1992): 672–79. http://dx.doi.org/10.1115/1.2910084.

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Traveling-bubble cavitation inception tests were conducted in a 30.48 cm water tunnel with a Schiebe headform. A computer code was developed to statistically model cavitation inception on a Schiebe headform, consisting of a numerical solution to the Rayleigh-Plesset equation coupled to a set of trajectory equations. Using this code, trajectories and growths were computed for bubbles of varying initial sizes. An initial off-body distance was specified and the bubble was free to follow an off-body trajectory. A Monte Carlo cavitation simulation was performed in which a variety of random processes were modeled. Three different nuclei distributions were specified including one similar to that measured in the water tunnel experiment. The results compared favorably to the experiment. Cavitation inception was shown to be sensitive to nuclei distribution. Off-body effect was also found to be a significant factor in determining whether or not a bubble would cavitate. The effect of off-body trajectories on the critical bubble diameter was examined. The traditional definition of critical diameter based on the minimum pressure coefficient of the body or the measurement of liquid tension was found to be inadequate in defining cavitation inception.

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15

Liu, Zhenhuan, und Christopher E. Brennen. „Cavitation Nuclei Population and Event Rates“. Journal of Fluids Engineering 120, Nr. 4 (01.12.1998): 728–37. http://dx.doi.org/10.1115/1.2820730.

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To model the processes of cavitation inception, noise and damage, it is necessary to generate a model of the cavitation event rate which can then be coupled with the consequences of the individual events to produce a complete synthesis of the phenomenon. In this paper we describe recent efforts to connect the observed event rates to the measured distributions of cavitation nuclei in the oncoming stream. Comparisons are made between the observed event rates and event rates calculated from measured nuclei distributions using an algorithm which includes the dynamics of the nuclei motion and growth. Various complications are explored including the effect of the boundary layer, the relative motion between the nucleus and the liquid, the observable bubble size effect, and the effect of bubble growth on neighboring nuclei. All of these are seen to have important influences on the event rate, and therefore, on cavitation inception and other macroscopic consequences. We demonstrate that it is possible to predict the correct order of magnitude of the event rate when an attempt is made to model the important flow complications.

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Boulon, O., J. P. Franc und J. M. Michel. „Tip Vortex Cavitation on an Oscillating Hydrofoil“. Journal of Fluids Engineering 119, Nr. 4 (01.12.1997): 752–58. http://dx.doi.org/10.1115/1.2819494.

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This paper discusses tests conducted in the hydrodynamic tunnel of the University of Grenoble on a 3D oscillating hydrofoil. Visualization of unsteady tip vortex cavitation indicates a strong influence of the water nuclei content. The investigation was focused on the influence of the oscillation frequency on tip vortex cavitation inception. For very low nuclei content, cavitation inception is strongly delayed as compared to the steady-state results at very small oscillation frequencies. This delay is significantly reduced by nuclei seeding. The results can be explained by assuming that the time required for the inception of cavitation in the tip vortex corresponds to the time necessary for a cavitation nucleus to be captured by the vortex core.

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17

Matsumoto, Y. „Contribution of Homogeneous Condensation Inside Cavitation Nuclei to Cavitation Inception“. Journal of Fluids Engineering 108, Nr. 4 (01.12.1986): 433–37. http://dx.doi.org/10.1115/1.3242600.

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The response of a small gas bubble, so-called cavitation nucleus, to the reduction of ambient pressure is investigated theoretically and experimentally. Numerical results show that the gas mixture inside the bubble expands adiabatically and the temperature of the mixture decreases rapidly at the first stage, however the temperature recovers soon to the surrounding liquid temperature by homogeneous condensation which forms a mist inside the bubble. Consequently, the bubble grows almost isothermally. Experiments have been performed using a hydro-shock tube. The radius of a small bubble has been measured by a light-scattering method whose time resolving power is one micro-second. The experimental results are found to be in good agreement with the numerical results calculated using the ambient pressure change measured in the test section.

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Chatterjee, Dhiman, und Vijay H. Arakeri. „Towards the concept of hydrodynamic cavitation control“. Journal of Fluid Mechanics 332 (Februar 1997): 377–94. http://dx.doi.org/10.1017/s0022112096004223.

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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.

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19

Billet, M. L. „Cavitation Nuclei Measurements With an Optical System“. Journal of Fluids Engineering 108, Nr. 3 (01.09.1986): 366–72. http://dx.doi.org/10.1115/1.3242588.

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Many recent experiments have shown the significance of cavitation nuclei, i.e., gas bubbles and/or particulate; however, progress in making quantitative predictions of cavitation depends upon some knowledge of cavitation nuclei properties such as shape, size distribution and concentration. Thus, research has also been concerned with developing measuring systems that give the statistics of the cavitation nuclei distribution. There are many different systems currently being developed; however, only the accuracy and application of the light-scattering technique initially developed by Keller is addressed in this paper. A model is formulated based on appropriate statistical analysis that defines the accuracy for a given sample size. Very good agreement has been found between microbubble distributions measured with the light-scattering system and with holography. Microbubble distribution data were obtained in the 305 mm water tunnel for different air content levels, tunnel static pressures and several tunnel velocities. These data are compared to nuclei distributions obtained at other facilities.

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20

Mørch, K. A. „Reflections on cavitation nuclei in water“. Physics of Fluids 19, Nr. 7 (Juli 2007): 072104. http://dx.doi.org/10.1063/1.2747210.

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21

Porter, Tyrone M. „Tailoring cavitation nuclei for biomedical applications“. Journal of the Acoustical Society of America 143, Nr. 3 (März 2018): 1861. http://dx.doi.org/10.1121/1.5036104.

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22

Wang, Yi-Chun. „Stability Analysis of One-Dimensional Steady Cavitating Nozzle Flows With Bubble Size Distribution“. Journal of Fluids Engineering 122, Nr. 2 (20.12.1999): 425–30. http://dx.doi.org/10.1115/1.483273.

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A continuum bubbly mixture model coupled to the Rayleigh-Plesset equation for the bubble dynamics is employed to study one-dimensional steady bubbly cavitating flows through a converging-diverging nozzle. A distribution of nuclei sizes is specified upstream of the nozzle, and the upstream cavitation number and nozzle contraction are chosen so that cavitation occurs in the flow. The computational results show very strong interactions between cavitating bubbles and the flow. The bubble size distribution may have significant effects on the flow; it is shown that it reduces the level of fluctuations and therefore reduces the “cavitation loss” compared to a monodisperse distribution. Another interesting interaction effect is that flashing instability occurs as the flow reaches a critical state downstream of the nozzle. A stability analysis is proposed to predict the critical flow variables. Excellent agreement is obtained between the analytical and numerical results for flows of both equal bubble size and multiple bubble sizes. [S0098-2202(00)00702-1]

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Hsiao, Chao-Tsung, und Georges L. Chahine. „Scaling of Tip Vortex Cavitation Inception Noise With a Bubble Dynamics Model Accounting for Nuclei Size Distribution“. Journal of Fluids Engineering 127, Nr. 1 (01.01.2005): 55–65. http://dx.doi.org/10.1115/1.1852476.

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The acoustic pressure generated by cavitation inception in a tip vortex flow was simulated in water containing a realistic bubble nuclei size distribution using a surface-averaged pressure (SAP) spherical bubble dynamics model. The flow field was obtained by the Reynolds-averaged Navier–Stokes computations for three geometrically similar scales of a finite-span elliptic hydrofoil. An “acoustic” criterion, which defines cavitation inception as the flow condition at which the number of acoustical “peaks” above a pre-selected pressure level exceeds a reference number per unit time, was applied to the three scales. It was found that the scaling of cavitation inception depended on the reference values (pressure amplitude and number of peaks) selected. Scaling effects (i.e., deviation from the classical σi∝Re0.4) increase as the reference inception criteria become more stringent (lower threshold pressures and less number of peaks). Larger scales tend to detect more cavitation inception events per unit time than obtained by classical scaling because a relatively larger number of nuclei are excited by the tip vortex at the larger scale due to simultaneous increase of the nuclei capture area and of the size of the vortex core. The average nuclei size in the nuclei distribution was also found to have an important impact on cavitation inception number. Scaling effects (i.e., deviation from classical expressions) become more important as the average nuclei size decreases.

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Jasionowski, Robert, Wojciech Polkowski und Dariusz Zasada. „The Destruction Mechanism of Titanium Subjected to Cavitation Erosion“. Key Engineering Materials 687 (April 2016): 117–22. http://dx.doi.org/10.4028/www.scientific.net/kem.687.117.

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A cavitation erosion is the process based on an impact of pressure pulses on a material’s surface caused by the phenomenon of cavitation. The term cavitation is defined as a phenomenon of formation, growth and disappearance (implosion) of bubbles due to cyclic pressure variations in a liquid. The cavitation initiators are embryos (cavitation nuclei with a size up to 50 μm), located in the water or on wetted surfaces that lead to decreasing of the liquid ability to transfer tensile stresses. The role of embryos is played by micro gas bubbles, fine solid particles, micro-organisms or gas-filled pores on a surface of solid body embedded in a liquid. A rapid pressure drop occurring within the liquid and a presence of cavitational kernel causes rupture the continuity of the liquid and thus lead to the formation of steam-gas mixture areas, a so called cavitation bubbles. A cavitation bubble may be filled with a gas, a vapor or a steam/gas mixture.A course of cavitation depends on a cavitation type. In thepresent work, a mechanism of cavitiational destruction of 99,7 % titaniumtested on vibrational and jet-impact valaboratory stands, is analyzed. Results of thecavitational resistance evaluation of Ti99.7 titanium carried out onvibrational and jet-impact stands have revealed different mechanisms of acavitation destruction caused by various forms of cavitation. It was found thata surface of titanium samples tested on the vibratory stand was covered by verylarge number of microcracks which in a later stage of the research leads to theerosion of the material. The cavitational destruction of Ti samples on the jet-impact stand is initiatedby a plastic straining of subsurface area, which in the further stage leads toan erosion represented by the detachment of whole grains anda formation of deep pits on the material’s surface. Additionally, results of conducted studies have confirmed the fatigue character of the cavitationaldestruction process.

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Ceccio, S., S. Gowing und Y. T. Shen. „The Effects of Salt Water on Bubble Cavitation“. Journal of Fluids Engineering 119, Nr. 1 (01.03.1997): 155–63. http://dx.doi.org/10.1115/1.2819102.

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Experiments were performed to examine differences in bubble cavitation inception, form, and acoustic emission in fresh and salt water. The tests were conducted on an axisymmetric headform known as the ITTC body, and acoustic emission, cavitation bubble size, and cavitation event rates were measured for a variety of cavitation numbers and dissolved air contents at a fixed dynamic head for both fresh and salt water. Differences were detected in the cavitation inception index, cavitation bubble size distribution, and the resulting overall acoustic emission. These differences may be attributed to variations in the freestream nuclei population, and it is hypothesized that the solution of salt reduced the number and size of freestream nuclei. Differences in the overall acoustic emission were attributed to variation in the bubble event rate and average maximum bubble size between the fresh and salt water cavitation.

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Qiang, Fu, Chen Ming, Wang Xiuli, Zhu Rongsheng, Zhang Guoyu und Yu Jianen. „Stability of Air Nucleus in Liquid Water and Cavitation Inception on Marine Engineering“. Polish Maritime Research 25, s3 (01.12.2018): 111–19. http://dx.doi.org/10.2478/pomr-2018-0119.

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Abstract The micro air nucleus widely distributed in the ocean is a necessary condition for the cavitation of hydraulic machinery in seawater. In order to study the stability of air nucleus in seawater and cavitation inception, the computational domain of water molecules with air nucleus was studied using the method of molecular dynamics simulation, and the transient characteristics of air nucleus in liquid water were obtained. The key factors influencing nuclei stability were analyzed. The results showed that air nucleus with a certain mass could maintain the dynamic equilibrium in liquid water. The internal density of air nuclei had a critical value that allowed the nuclei to stably exist in water. The air nuclei mass was the decisive factor in its equilibrium volume in water, and the two were positively correlated. The internal density of air nuclei was negatively correlated with the nuclei radius when the nuclei was stable in water. Liquid surface tension was an important factor affecting the stability of the air nuclei. The larger the initial radius of nuclei, the smaller the water pressure, and the more likely the cavitation occurs.

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Lixin, Bai, Lin Weijun, Deng Jingjun, Li Chao, Xu Delong und Wu Pengfei. „Memory Effect and Redistribution of Cavitation Nuclei“. Physics Procedia 70 (2015): 1048–51. http://dx.doi.org/10.1016/j.phpro.2015.08.223.

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28

MATSUMOTO, Yoichiro, Toshiaki OKUDAIRA, Masayoshi WADA, Hisao ENOMOTO und Yasumasa ICHIKAWA. „Influence of cavitation on the nuclei distribution.“ Transactions of the Japan Society of Mechanical Engineers Series B 51, Nr. 472 (1985): 3844–51. http://dx.doi.org/10.1299/kikaib.51.3844.

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29

Ito, Y., und R. Oba. „A Limited Role of Separation Bubble in Desinent Cavitation“. Journal of Fluids Engineering 107, Nr. 1 (01.03.1985): 121–25. http://dx.doi.org/10.1115/1.3242427.

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In order to clarify whether a separation bubble always plays an important role, the desinence of streamer-cavitation, a kind of attached-cavitation, was carefully investigated in typical internal flows through venturies with and without a 40 μm thin backward facing step under a prescribed cavitation nuclei as well as various hydrodynamic conditions. The following facts have been found: (i) the separation bubble can play an important role in the desinence only when the separation bubble thickness H is larger than the diameter of nucleus dnp that may grow up to a critical one [18], (ii) a marked change takes place in the desinent cavitation number σd due to the step, i.e., σd ≅ |Cps| for H > dnp but σd < |Cps| for H ≦ dnp, (iii) for the cavitation there are two geneses, i.e., the nuclei floating within the separation bubble and the bubble-cloud occurring in the reattachment-region.

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d’Agostino, L., und A. J. Acosta. „A Cavitation Susceptibility Meter With Optical Cavitation Monitoring—Part One: Design Concepts“. Journal of Fluids Engineering 113, Nr. 2 (01.06.1991): 261–69. http://dx.doi.org/10.1115/1.2909490.

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This work is concerned with the design of a Cavitation Susceptibility Meter based on the use of a venturi tube for the measurement of the active cavitation nuclei concentration in water samples as a function of the applied tension. The operation of the Cavitation Susceptibility Meter is analyzed and the main considerations leading to the proposed design are illustrated and critically discussed. The results of this analysis indicate that the operational range is mainly limited by nuclei interference, flow separation and saturation (choking), and suggest to develop a Cavitation Susceptibility Meter where: (a) the flow possesses a laminar potential core throughout the venturi throat section in all operational conditions; (b) the pressure at the venturi throat is determined from the upstream pressure and the local flow velocity; (c) the detection of cavitation and the measurement of the flow velocity are carried out optically by means of a Laser Doppler Velocimeter; (d) a custom-made electronic Signal Processor incorporating a frequency counter is used for real time data generation and temporary storage; (e) a computerized system performs the final acquisition and reduction of the data.

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Luo, Hongying, und Ran Tao. „Prediction of the Cavitation over a Twisted Hydrofoil Considering the Nuclei Fraction Sensitivity at 4000 m Altitude Level“. Water 13, Nr. 14 (13.07.2021): 1938. http://dx.doi.org/10.3390/w13141938.

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Cavitation phenomenon is important in hydraulic turbomachineries. With the construction of pumping stations and hydro power stations on plateau, the influence of nuclei fraction on cavitation becomes important. As a simplified model, a twisted hydrofoil was used in this study to understand the cavitation behaviors on pump impeller blade and turbine runner blade at different altitude levels. The altitudes of 0 m, 1000 m, 2000 m, 3000 m and 4000 m were comparatively studied for simulating the plateau situation. Results show that the cavitation volume proportion fcav increases with the decreasing of cavitation coefficient Cσ. At a specific Cσ, high altitude and few nuclei will cause smaller size of cavitation. The smaller Cσ is, the higher the sensitivity Δfcav is. The larger Cσ is, the higher the relative sensitivity Δfcav* is. On the twisted foil, flow incidence angle increases from the sidewall to mid-span with the decreasing of the local minimum pressure. When Cσ is continually decreasing, the size of cavitation extends in spanwise, streamwise and thickness directions. The cavity is broken by the backward-jet flow when Cσ becomes small. A tail generates and the cavity becomes relatively unstable. This study will provide reference for evaluating the cavitation status of the water pumps and hydroturbines installed on a plateau with high altitude level.

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Soyama, Hitoshi. „Cavitation Characteristics of Ultrapure Water. Behavior of Cavitation Nuclei in Vibratory Erosion Tests.“ Transactions of the Japan Society of Mechanical Engineers Series B 60, Nr. 573 (1994): 1526–31. http://dx.doi.org/10.1299/kikaib.60.1526.

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Tanger, H., und E. A. Weitendorf. „Applicability Tests for the Phase Doppler Anemometer for Cavitation Nuclei Measurements“. Journal of Fluids Engineering 114, Nr. 3 (01.09.1992): 443–49. http://dx.doi.org/10.1115/1.2910051.

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A compromise between a reliable phase-diameter relationship and a good imaging of the control volume is necessary for the application of the PDA-instrument when measuring cavitation nuclei. The phase-diameter relationship for bubbles and particles were investigated theoretically, the imaging of the control volume experimentally. Further PDA-measurements were conducted for Latex spheres of different diameters as scattering objects in water and single air bubbles in transparent plastics. The concentrations and diameters measured by the PDA agreed very well with the results obtained by other methods. An investigation of the scattering from background particles in water was conducted with the PDA in the small HSVA cavitation tunnel. Also, nuclei measurements were performed with a gassing system in the tunnel. In 1972 the ITTC-Cavitation Committee defined specifications for the control of the free air content in routine and research cavitation tests. The tests completed so far show that the PDA-instrument fulfills these specifications for the major part.

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Chahine, G. L., und Y. T. Shen. „Bubble Dynamics and Cavitation Inception in Cavitation Susceptibility Meters“. Journal of Fluids Engineering 108, Nr. 4 (01.12.1986): 444–52. http://dx.doi.org/10.1115/1.3242602.

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To improve the understanding of the scaling effects of nuclei on cavitation inception, bubble dynamics, multibubble interaction effects, and bubble-mean flow interaction in a venturi Cavitation Susceptibility Meter are considered theoretically. The results are compared with classical bubble static equilibrium predictions. In a parallel effort, cavitation susceptibility measurements of ocean and laboratory water were carried out using a venturi device. The measured cavitation inception indices were found to relate to the measured microbubble concentration. The relationship between the measured cavitation inception and bubble concentration and distribution can be explained by using the theoretical predictions. A tentative explanation is given for the observation that the number of cavitation bursting events measured by an acoustic device is sometimes an order of magnitude lower than the number of microbubbles measured by the light scattering detector. The questions addressed here add to the fundamental knowledge needed if the cavitation susceptibility meter is to be used effectively for the measurement of microbubble size distributions.

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Crum, Lawrence A., und Julianna C. Simon. „Nucleation and stabilization of cavitation nuclei in liquids“. Journal of the Acoustical Society of America 143, Nr. 3 (März 2018): 1834. http://dx.doi.org/10.1121/1.5036018.

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Andersen, Anders, und Knud Aage Mørch. „Cavitation nuclei in water exposed to transient pressures“. Journal of Fluid Mechanics 771 (20.04.2015): 424–48. http://dx.doi.org/10.1017/jfm.2015.185.

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A model of skin-stabilized interfacial cavitation nuclei and their response to tensile and compressive stressing is presented. The model is evaluated in relation to experimental tensile strength results for water at rest at the bottom of an open water-filled container at atmospheric pressure and room temperature. These results are obtained by recording the initial growth of cavities generated by a short tensile pulse applied to the bottom of the container. It is found that the cavitation nuclei shift their tensile strength depending on their pressure history. Static pressurization for an extended period of time prior to testing is known to increase the tensile strength of water, but little information is available on how it is affected by compression pulses of short duration. This is addressed by imposing compression pulses of approximately 1 ms duration and a peak intensity of a few bar prior to the tension pulse. The observations are interpreted on the basis of the new model.

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Arora, M., C. D. Ohl und D. Lohse. „Effect of nuclei concentration on cavitation cluster dynamics“. Journal of the Acoustical Society of America 121, Nr. 6 (2007): 3432. http://dx.doi.org/10.1121/1.2722045.

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Ku, Garam, Cheolung Cheong, Ilryong Park und Hanshin Seol. „Numerical Investigation of Tip Vortex Cavitation Inception and Noise of Underwater Propellers of Submarine Using Sequential Eulerian–Lagrangian Approaches“. Applied Sciences 10, Nr. 23 (05.12.2020): 8721. http://dx.doi.org/10.3390/app10238721.

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In this study, the high-fidelity numerical methods are developed to investigate the tip vortex cavitation (TVC) inception and noise of underwater propellers, namely, Model-A and Model-B, which are designed to investigate the effects of sweep angle on cavitation inception and noise. In addition, the entire body of the DARPA Suboff submarine is included to consider the effects of the inflow distortion originating from the boundary layer flow of the submarine body on the cavitating flow of the propellers. The Eulerian approach consisting of Reynolds-averaged Navier–Stokes (RANS) solver and the vortex model is coupled with the Lagrangian approach using the bubble dynamics equations and the acoustic analogy for nuclei initially distributed in inlet flow. First, three-dimensional incompressible unsteady RANS simulations are performed to predict the hydrodynamic flow field driven by underwater propellers installed on a DARPA Suboff submarine body. The Scully vortex model and dissipation vortex model (DVM) are used to regenerate the tip vortex dissipated by artificial numerical damping and low grid resolution around the vortex core center, which is identified by using minimum λ2-criterion in the swirling flow field originating from the propeller blade tip. Then, tip vortex cavitation inception is simulated by applying the bubble dynamics equations to nuclei initially distributed in the inflow region. The volume and location of each nucleus are obtained by solving the bubble dynamics equations on the flow field obtained using the Eulerian method. Finally, the cavitation noise is predicted by modeling each bubble with a point monopole source whose strength is proportional to its volume acceleration. The validity of the present numerical methods is confirmed by comparing the predicted acoustic pressure spectrum with the measured ones.

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Reinhardt, Nina, Kristin Dietz-Laursonn, Marc Janzen, Klaus Radermacher, Christian Bach, Klaus Radermacher und Matias de la Fuente. „Experimental setup for evaluation of cavitation effects in ESWL“. Current Directions in Biomedical Engineering 4, Nr. 1 (01.09.2018): 191–94. http://dx.doi.org/10.1515/cdbme-2018-0047.

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AbstractCavitation is a major fracture mechanism in extracorporeal shock wave lithotripsy (ESWL). However, it can cause tissue trauma and its effects on kidney stones and surrounding tissue are not fully understood. Therefore experimental setups enabling systematic parameter studies are crucial. We developed and evaluated a testing rig comprising three measuring methods in order to examine this mechanism. Our initial evaluation of this setup based on standard components showed promising results. Primary cavitation was displayed by high-speed photography 195 μs after the shock front had passed the focal zone. The effect of different pulse repetition rates (30, 60, 90, 120 SW/min) on the extension of the cavitation area was determined. The lifetime of secondary cavitation was analysed by B-mode ultrasound imaging. In a post processing progress the images showing bubbles were compared to a reference picture for both types of cavitation and the number of pixels that changed colour was counted. Furthermore stone comminution at different pulse repetition rates (30, 60, 90, 120 SW/min) was investigated by fixed-dose fragmentation. We observed an inverse correlation of cavitation and fragmentation. As the pulse repetition rate increases, the area of primary cavitation grows whereas the fragmentation efficiency decreases. B-mode imaging showed that secondary cavitation bubbles persisted between the shocks and can serve as nuclei. The higher the pulse repetition rate is, the more of these nuclei remain and thus facilitate formation of primary cavitation. The experimental setup provides reproducible results regarding the development of primary and secondary cavitation on the one hand and the fragmentation of phantom stones on the other hand. Therefore it can be utilized to further investigate the effect of different boundary conditions and shock wave parameters on cavitation and stone comminution. The impact of different focal sound fields is subject of ongoing research.

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Ku, Garam, Cheolung Cheong und Hanshin Seol. „Numerical Investigation of Tip-Vortex Cavitation Noise of an Elliptic Wing Using Coupled Eulerian-Lagrangian Approaches“. Applied Sciences 10, Nr. 17 (26.08.2020): 5897. http://dx.doi.org/10.3390/app10175897.

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In this study, a numerical methodology is developed to investigate the tip-vortex cavitation of NACA16-020 wings and their flow noise. The numerical method consists of a sequential one-way coupled application of Eulerian and Lagrangian approaches. First, the Eulerian method based on Reynolds-averaged Navier–Stokes equation is applied to predict the single-phase flow field around the wing, with particular emphasis on capturing high-resolution tip-vortex flow structures. Subsequently, the tip-vortex flow field is regenerated by applying the Scully vortex model. Secondly, the Lagrangian approach is applied to predict the tip-vortex cavitation inception and noise of the wing. The initial nuclei are distributed upstream of the wing. The subsequent time-varying size and position of each nucleus are traced by solving spherically symmetric bubble dynamics equations for the nuclei in combination with the flow field predicted from the Eulerian approach. The acoustic pressure at the observer position is computed by modelling each bubble as a point source. The numerical results of the acoustic pressure spectrum are best matched to the measured results when the nuclei number density of freshwater is used. Finally, the current numerical method is applied to the flows of various cavitation numbers. The results reveal that the cavitation inception determined by the predicted acoustic pressure spectrum well matched the experimental result.

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Kooiman, Klazina, Silke Roovers, Simone A. G. Langeveld, Robert T. Kleven, Heleen Dewitte, Meaghan A. O'Reilly, Jean-Michel Escoffre et al. „Ultrasound-Responsive Cavitation Nuclei for Therapy and Drug Delivery“. Ultrasound in Medicine & Biology 46, Nr. 6 (Juni 2020): 1296–325. http://dx.doi.org/10.1016/j.ultrasmedbio.2020.01.002.

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Bai, Lixin, Jingjun Deng, Chao Li, Delong Xu und Weilin Xu. „Acoustic cavitation structures produced by artificial implants of nuclei“. Ultrasonics Sonochemistry 21, Nr. 1 (Januar 2014): 121–28. http://dx.doi.org/10.1016/j.ultsonch.2013.07.011.

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Borkent, Bram M., Stephan Gekle, Andrea Prosperetti und Detlef Lohse. „Nucleation threshold and deactivation mechanisms of nanoscopic cavitation nuclei“. Physics of Fluids 21, Nr. 10 (Oktober 2009): 102003. http://dx.doi.org/10.1063/1.3249602.

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Greenleaf, William J., Mark E. Bolander, Gobinda Sarkar, Mary B. Goldring und James F. Greenleaf. „Artificial Cavitation Nuclei Significantly Enhance Acoustically Induced Cell Transfection“. Ultrasound in Medicine & Biology 24, Nr. 4 (Mai 1998): 587–95. http://dx.doi.org/10.1016/s0301-5629(98)00003-9.

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Barrett, Brian C., Keefe B. Manning, Arnold A. Fontaine, John M. Tarbell und Steven Deutsch. „CHARACTERIZATION OF NUCLEI CONTENT FOR MECHANICAL HEART VALVE CAVITATION“. ASAIO Journal 51, Nr. 2 (März 2005): 9A. http://dx.doi.org/10.1097/00002480-200503000-00035.

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Tsuru, Wakana, Takafumi Konishi, Satoshi Watanabe und Shin-ichi Tsuda. „Observation of inception of sheet cavitation from free nuclei“. Journal of Thermal Science 26, Nr. 3 (06.05.2017): 223–28. http://dx.doi.org/10.1007/s11630-017-0933-8.

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Wienken, W., J. Stiller und A. Keller. „A Method to Predict Cavitation Inception Using Large-Eddy Simulation and its Application to the Flow Past a Square Cylinder“. Journal of Fluids Engineering 128, Nr. 2 (01.03.2006): 316–25. http://dx.doi.org/10.1115/1.2170132.

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A new method to predict traveling bubble cavitation inception is devised. The crux of the method consists in combining the enhanced predictive capabilities of large-eddy-simulation (LES) for flow computation with a simple but carefully designed stability criterion for the cavitation nuclei. For LES a second-order accurate finite element model based on the Galerkin/least-squares method with Runge-Kutta time integration is applied. The incoming nucleus’ spectrum is approximated by a Weibull distribution. Moreover, it is shown that under typical conditions the stability of the nuclei can be evaluated with an algebraic criterion emerging from the Rayleigh-Plesset equation. This criterion can be expressed as modified critical Thoma number and fits well into the LES approach. The method was applied to study cavitation inception in a flow past a square cylinder. A good agreement with experimental results was achieved. Furthermore, the principal advantage over statistical (time-averaged) methods could be clearly demonstrated, even though the spatial resolution and application of the LES were restricted by limited computational resources. As the latter keep on growing, a wider range of applications will become accessible methods for cavitation prediction based on algebraic stability criteria combined with LES.

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Fredlund, Delwyn G., Julian K.-M. Gan, Yun Guan und Neil Richardson. „Suction Measurements on a Saskatchewan Soil Using a Direct-Measurement, High-Range Suction Sensor“. Transportation Research Record: Journal of the Transportation Research Board 1596, Nr. 1 (Januar 1997): 84–92. http://dx.doi.org/10.3141/1596-13.

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A tensiometric-type suction sensor capable of direct measurement of matric suctions greater than 100 kPa has recently been developed. The sensor has been used to measure matric suctions up to 1250 kPa. The sensor makes use of the tensile strength of water for the measurement of matric suction. The cavitation of water in conventional tensiometers occurs at a negative pressure approaching 1 atmosphere because of the presence of cavitation nuclei. In the absence of cavitation nuclei, the tensile strength of water can be on the order of several atmospheres. The direct-measurement, high-range suction sensor has been used for the measurement of matric suction on borehole samples obtained during a soils investigation at a bridge site near the town of Outlook, Saskatchewan, Canada. The method has proven to be fast and simple to use. Matric suction measurements of the samples from the Outlook bridge site are presented, along with an interpretation of the laboratory data.

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Shen, Y. T., und P. E. Dimotakis. „Viscous and Nuclei Effects on Hydrodynamic Loadings and Cavitation of a NACA 66 (MOD) Foil Section“. Journal of Fluids Engineering 111, Nr. 3 (01.09.1989): 306–16. http://dx.doi.org/10.1115/1.3243645.

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A series of experiments has been conducted on a two-dimensional NACA 66 (MOD) foil to examine the effects of viscosity and nuclei on cavitation inception. In this paper the main discussions center on two foil angles having different types of pressure loadings to represent a propeller blade section operating at design and off-design conditions. At one degree design angle of attack the foil experiences a rooftop-type gradually varying pressure distribution. At three degrees off-design angle of attack the foil experiences a sharp suction pressure peak near the leading edge. Cebeci’s viscid/inviscid interactive code is used to compute the viscous scale effects on the development of the boundary layer, lift, drag and pressure distribution on the foil. Chahine’s multibubble interaction code is used to compute the effect of nuclei, test speeds, foil size and foil surface on traveling bubble cavitation. Both computer codes are found to agree satisfactorily with the experimental measurements reported here. Two assumptions commonly used to predict full scale surface cavitation from model tests are examined experimentally and theoretically. The first assumption states that cavitation inception occurs when the static pressure reaches the vapor pressure. On the contrary, the experiments showed that the water flowing over the foil surface sustained significant amounts of tension during inception of midchord bubble cavitation as well as leading edge sheet cavitation. The second assumption states that there is no scale effect on the values of negative minimum pressure coefficient. In the case of a rooftop-type pressure loading, the second assumption is supported by the pressure numerical calculations. However, in the case of a pressure loading with a strong suction peak near the leading edge the value of negative minimum pressure coefficient is as much as 12 to 15 percent lower on a model than at full scale.

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Grundy, Megan, Luca Bau, Claudia Hill, Catherine Paverd, Christophoros Mannaris, James Kwan, Calum Crake, Christian Coviello, Constantin Coussios und Robert Carlisle. „Improved therapeutic antibody delivery to xenograft tumors using cavitation nucleated by gas-entrapping nanoparticles“. Nanomedicine 16, Nr. 1 (Januar 2021): 37–50. http://dx.doi.org/10.2217/nnm-2020-0263.

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Aims: Testing ultrasound-mediated cavitation for enhanced delivery of the therapeutic antibody cetuximab to tumors in a mouse model. Methods: Tumors with strong EGF receptor expression were grown bilaterally. Cetuximab was coadministered intravenously with cavitation nuclei, consisting of either the ultrasound contrast agent Sonovue or gas-stabilizing nanoscale SonoTran Particles. One of the two tumors was exposed to focused ultrasound. Passive acoustic mapping localized and monitored cavitation activity. Both tumors were then excised and cetuximab concentration was quantified. Results: Cavitation increased tumoral cetuximab concentration. When nucleated by Sonovue, a 2.1-fold increase (95% CI 1.3- to 3.4-fold) was measured, whereas SonoTran Particles gave a 3.6-fold increase (95% CI 2.3- to 5.8-fold). Conclusions: Ultrasound-mediated cavitation, especially when nucleated by nanoscale gas-entrapping particles, can noninvasively increase site-specific delivery of therapeutic antibodies to solid tumors.

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