Steady-State Cavitating Nozzle Flows With Nucleation

2005 ◽  
Vol 127 (4) ◽  
pp. 770-777 ◽  
Author(s):  
Can F. Delale ◽  
Kohei Okita ◽  
Yoichiro Matsumoto
Keyword(s):  
Steady State ◽  
Bubble Dynamics ◽  
Bubbly Flow ◽  
Bubble Radius ◽  
Stable Solution ◽  
Bubble Nucleation ◽  
Bubble Collapse ◽  
Stable Steady State ◽  
Bubbly Liquid ◽  
Nozzle Flows

Quasi-one-dimensional steady-state cavitating nozzle flows with homogeneous bubble nucleation and nonlinear bubble dynamics are considered using a continuum bubbly liquid flow model. The onset of cavitation is modeled using an improved version of the classical theory of homogeneous nucleation, and the nonlinear dynamics of cavitating bubbles is described by the classical Rayleigh-Plesset equation. Using a polytropic law for the partial gas pressure within the bubble and accounting for the classical damping mechanisms, in a crude manner, by an effective viscosity, stable steady-state solutions with stationary shock waves as well as unstable flashing flow solutions were obtained, similar to the homogeneous bubbly flow solutions given by Wang and Brennen [J. Fluids Eng., 120, 166–170, 1998] and by Delale, Schnerr, and Sauer [J. Fluid Mech., 427, 167–204, 2001]. In particular, reductions in the maximum bubble radius and bubble collapse periods are observed for stable nucleating nozzle flows as compared to the nonnucleating stable solution of Wang and Brennen under similar conditions.

Quasi-one-dimensional steady-state cavitating nozzle flows

2001 ◽  
Vol 427 ◽  
pp. 167-204 ◽  
Author(s):  
C. F. DELALE ◽  
G. H. SCHNERR ◽  
J. SAUER
Keyword(s):  
Dynamical System ◽  
Steady State ◽  
Nonlinear Dynamical System ◽  
Stable Steady State ◽  
Bubbly Liquid ◽  
Nozzle Flow ◽  
Continuous Growth ◽  
One Dimensional ◽  
Bubble Interactions ◽  
Nozzle Flows

Quasi-one-dimensional cavitating nozzle flows are considered by employing a homogeneous bubbly liquid flow model. The nonlinear dynamics of cavitating bubbles is described by a modified Rayleigh–Plesset equation that takes into account bubble/bubble interactions by a local homogeneous mean-field theory and the various damping mechanisms by a damping coefficient, lumping them together in the form of viscous dissipation. The resulting system of quasi-one-dimensional cavitating nozzle flow equations is then uncoupled leading to a nonlinear third-order ordinary differential equation for the flow speed. This equation is then cast into a nonlinear dynamical system of scaled variables which describe deviations of the flow field from its corresponding incompressible single-phase value. The solution of the initial-value problem of this dynamical system can be carried out very accurately, leading to an exact description of the hydrodynamic field for the model considered.A bubbly liquid composed of water vapour–air bubbles in water at 20 °C for two different area variations is considered, and the initial cavitation number is chosen in such a way that cavitation can occur in the nozzle. Results obtained, when bubble/bubble interactions are neglected, show solutions with flow instabilities, similar to the flashing flow solutions found recently by Wang and Brennen. Stable steady-state cavitating nozzle flow solutions, either with continuous growth of bubbles or with growth followed by collapse of bubbles, were obtained when bubble/bubble interactions were considered together with various damping mechanisms.

Steady-State Subcooled Nucleate Boiling on a Downward-Facing Hemispherical Surface

1998 ◽  
Vol 120 (2) ◽  
pp. 365-370 ◽  
Author(s):  
K. H. Haddad ◽  
F. B. Cheung
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Heat Transport ◽  
Bubble Dynamics ◽  
Flow Direction ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
High Heat ◽  
Bubble Nucleation ◽  
High Heat Flux

Steady-state nucleate boiling heat transfer experiments in saturated and subcooled water were conducted. The heating surface was a 0.305 m hemispherical aluminum vessel heated from the inside with water boiling on the outside. It was found that subcooling had very little effect on the nucleate boiling curve in the high heat flux regime where latent heat transport dominated. On the other hand, a relatively large effect of subcooling was observed in the low-heat-flux regime where sensible heat transport was important. Photographic records of the boiling phenomenon and the bubble dynamics indicated that in the high-heat-flux regime, boiling in the bottom center region of the vessel was cyclic in nature with a liquid heating phase, a bubble nucleation and growth phase, a bubble coalescence phase, and a large vapor mass ejection phase. At the same heat flux level, the size of the vapor masses was found to decrease from the bottom center toward the upper edge of the vessel, which was consistent with the increase observed in the critical heat flux in the flow direction along the curved heating surface.

scholarly journals Bubble Nucleation and Growth of Dissolved Gas in Solution Flowing across a Cavitating Nozzle

2015 ◽  
Vol 773-774 ◽  
pp. 304-308 ◽  
Author(s):  
Zhen Hong Ban ◽  
Kok Keong Lau ◽  
Mohd Sharif Azmi
Keyword(s):  
Bubble Dynamics ◽  
Bubbly Flow ◽  
Bubble Formation ◽  
Computational Modelling ◽  
Nucleation And Growth ◽  
Bubble Nucleation ◽  
Supersaturated Solution ◽  
Computational Domain ◽  
Dissolved Gas ◽  
Growth Phenomenon

Computational modelling of dissolved gas bubble formation and growth in supersaturated solution is essential for various engineering applications, including flash vaporisation of petroleum crude oil. The common mathematical modelling of bubbly flow only caters for single liquid and its vapour, which is known as cavitation. This work aims to simulate the bubble nucleation and growth of dissolved CO2 in water across a cavitating nozzle. The dynamics of bubble nucleation and growth phenomenon will be predicted based on the hydrodynamics in the computational domain. The complex interrelated bubble dynamics, mass transfer and hydrodynamics was coupled by using Computational Fluid Dynamics (CFD) and bubble nucleation and growth model. Generally, the bubbles nucleate at the throat of the nozzle and grow along with the flow. Therefore, only the region after the throat of the nozzle has bubbles. This approach is expected to be useful for various types of bubbly flow modelling in supersaturated condition.

Numerical Investigation of Liquid Parameters Effect on the Oscillation of Cavitation Bubble

2014 ◽  
Vol 568-570 ◽  
pp. 1794-1800
Author(s):  
Xiu Mei Liu ◽  
Bei Bei Li ◽  
Wen Hua Li ◽  
Jie He ◽  
Jian Lu ◽  
...  
Keyword(s):  
Surface Tension ◽  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Dynamic Performance ◽  
Bubble Radius ◽  
Gas Content ◽  
Viscous Force ◽  
Bubble Collapse ◽  
Hydraulic Systems ◽  
Increasing Temperature

Cavitation is a common harmful phenomenon in hydraulic transmission systems. It not only damages flow continuity and reduces medium physical performance, but also induces vibration and noise. At the same time, the efficiency of a system is reduced due to cavitation, especially dynamic performance are deteriorated. Applying commercial CFD software FLUENT, the cavitation issuing from the orifice was numerically investigated, reducing the harm. The effect of liquid parameters (such as surface tension, gas content, and the temperature) on the oscillation of bubble is studied numerically. The modified Rayleigh-Plesset equations are presented to describe the oscillation of bubble in different liquids. Employing the finite difference calculus, the behavior of a cavitation bubble in liquids with different physics parameters are obtained. Meanwhile, the numerical results are compared with experiment results. It is observed that the viscous force decreases the growth and collapse of a bubble, making it expand or collapse less violently. And the surface-tension forces stave bubble growth progress and speed up bubble collapse process. On the other hand, both the maximum bubble radius and bubble lifetime increase with increasing temperature. These results can provide theory basis for understanding cavitation bubble dynamics in the hydraulic systems.

Numerical Simulation of Vapor–Bubble Collapse—Heat Transfer and Nonlinear Dynamics Issues

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Jyoti Bhati ◽  
Swapan Paruya ◽  
Subhramaniam Pushpavanam
Keyword(s):  
Heat Transfer ◽  
Nonlinear Dynamics ◽  
Steady State ◽  
Vapor Bubble ◽  
Bubble Radius ◽  
Bubble Collapse ◽  
Large Contribution ◽  
Steady State Analysis ◽  
The Stability ◽  
State Analysis

Abstract In this work, we compute the dynamics of a spherical vapor-bubble in an infinite pool of subcooled water during bubble collapse using our semi-analytical method. The main contribution of this work is to bring out the dynamics of nonmonotonic bubble collapse describing heat transfer characteristics and nonlinear dynamics. The dynamics shows the variation of radius with time for collapsing vapor bubble at different subcooling ΔTsub of 1.40 K to 35 K. The present approach accurately determines the bubble radius decreasing with time and has been compared with our experimental results, the experiment from literature, the other theories, and correlations. As it is noted that the literature lacks steady-state analysis of oscillating bubble collapse, we also report the steady-state analysis and the bifurcation analysis of bubble collapse at a pressure of 1.0 atm to check the stability of bubble collapse. The effect of ΔTsub and initial bubble radius R0 on dynamics of bubble collapse has been analyzed. The collapse of big bubbles involves with the bubble oscillations because of a large contribution of liquid inertia and the collapse of very small bubbles essentially occurs in heat transfer regime.

Complete Convective Condensation Inside Small Diameter Horizontal Tubes

2003 ◽  
Author(s):  
Be´atrice Mederic ◽  
Marc Miscevic ◽  
Vincent Platel ◽  
Pascal Lavieille ◽  
Jean-Louis Joly
Keyword(s):  
Experimental Study ◽  
Bubbly Flow ◽  
Bubble Radius ◽  
Small Diameter ◽  
Bubble Collapse ◽  
Two Phase ◽  
Narrow Channels ◽  
Horizontal Tubes ◽  
Significant Difference ◽  
Convective Condensation

An experimental study of complete convective condensation inside narrow channels is presented in this paper. Two-phase flows patterns and their transition (annular, annular-wavy, slug and bubbly flow) are visualized for the two tube diameters under study. A significant difference is observed for the two sizes of tube. Experimental results of the bubble radius decrease are then determined and compared to a model of bubble collapse in a subcooled and infinite liquid.

Numerical Study on Mass Transfer Effects on Spherical Cavitation Bubble Collapse in an Acoustic Field

2010 ◽  
Author(s):  
Ehsan Samiei ◽  
Mehrzad Shams ◽  
Reza Ebrahimi
Keyword(s):  
Mass Transfer ◽  
Cavitation Bubble ◽  
Bubble Dynamics ◽  
Numerical Study ◽  
Bubble Radius ◽  
Numerical Code ◽  
Bubble Collapse ◽  
Growth Time ◽  
Transfer Effects ◽  
Low Amplitude

A numerical code to simulate mass transfer effects on spherical cavitation bubble collapse in an acoustic pressure domain in quiescent water has been developed. Gilmore equation is used to simulate bubble dynamics, with considering mass diffusion and heat transfer. Bubbles with different initial radii were considered in quiescent infinite water in interaction with sinusoidal shock waves with different magnitudes of amplitude and frequency. Simulations were done in two cases; with and without considering mass transfer. Good agreement with reference data was achieved. For bubbles with small radii in high frequency pressure field with low amplitude, mass transfer causes larger maximum radii and growth time, and more violent resultant collapse. Decreasing pressure frequency or increasing its amplitude causes larger maximum radii, longer collapse time, and more violent collapse. But, in cases with mass transfer because at the last moments of collapse stage a large amount of water vapor is trapped inside the bubble, the collapse will become less violent. For larger bubbles collapse becomes more violent for the cases without mass transfer in all pressure amplitudes and higher frequencies. But decreasing pressure frequency makes the collapse of the bubbles with mass transfer more violent. However, mass transfer effects decreases with increasing initial bubble radius.

scholarly journals Phase transitions from the fifth dimension

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Kaustubh Agashe ◽  
Peizhi Du ◽  
Majid Ekhterachian ◽  
Soubhik Kumar ◽  
Raman Sundrum
Keyword(s):  
Bubble Dynamics ◽  
Effective Field ◽  
Bubble Nucleation ◽  
Thin Wall ◽  
Black Brane ◽  
Composite Higgs ◽  
Fifth Dimension ◽  
Two Phases ◽  
Holographic Description ◽  
The Impact

Abstract We study the cosmological transition of 5D warped compactifications, from the high-temperature black-brane phase to the low-temperature Randall-Sundrum I phase. The transition proceeds via percolation of bubbles of IR-brane nucleating from the black-brane horizon. The violent bubble dynamics can be a powerful source of observable stochastic gravitational waves. While bubble nucleation is non-perturbative in 5D gravity, it is amenable to semiclassical treatment in terms of a “bounce” configuration interpolating between the two phases. We demonstrate how such a bounce configuration can be smooth enough to maintain 5D effective field theory control, and how a simple ansatz for it places a rigorous lower-bound on the transition rate in the thin-wall regime, and gives plausible estimates more generally. When applied to the Hierarchy Problem, the minimal Goldberger-Wise stabilization of the warped throat leads to a slow transition with significant supercooling. We demonstrate that a simple generalization of the Goldberger-Wise potential modifies the IR-brane dynamics so that the transition completes more promptly. Supercooling determines the dilution of any (dark) matter abundances generated before the transition, potentially at odds with data, while the prompter transition resolves such tensions. We discuss the impact of the different possibilities on the strength of the gravitational wave signals. Via AdS/CFT duality the warped transition gives a theoretically tractable holographic description of the 4D Composite Higgs (de)confinement transition. Our generalization of the Goldberger-Wise mechanism is dual to, and concretely models, our earlier proposal in which the composite dynamics is governed by separate UV and IR RG fixed points. The smooth 5D bounce configuration we introduce complements the 4D dilaton/radion dominance derivation presented in our earlier work.

scholarly journals Results of the Marine Ice Sheet Model Intercomparison Project, MISMIP

2012 ◽  
Vol 6 (3) ◽  
pp. 573-588 ◽  
Author(s):  
F. Pattyn ◽  
C. Schoof ◽  
L. Perichon ◽  
R. C. A. Hindmarsh ◽  
E. Bueler ◽  
...  
Keyword(s):  
Steady State ◽  
Adaptive Mesh Refinement ◽  
Ice Sheet ◽  
Adaptive Mesh ◽  
Stable Steady State ◽  
Fixed Grid ◽  
Approximate Analytical Solutions ◽  
Grounding Line ◽  
Intercomparison Project ◽  
Line Positions

Abstract. Predictions of marine ice-sheet behaviour require models that are able to robustly simulate grounding line migration. We present results of an intercomparison exercise for marine ice-sheet models. Verification is effected by comparison with approximate analytical solutions for flux across the grounding line using simplified geometrical configurations (no lateral variations, no effects of lateral buttressing). Unique steady state grounding line positions exist for ice sheets on a downward sloping bed, while hysteresis occurs across an overdeepened bed, and stable steady state grounding line positions only occur on the downward-sloping sections. Models based on the shallow ice approximation, which does not resolve extensional stresses, do not reproduce the approximate analytical results unless appropriate parameterizations for ice flux are imposed at the grounding line. For extensional-stress resolving "shelfy stream" models, differences between model results were mainly due to the choice of spatial discretization. Moving grid methods were found to be the most accurate at capturing grounding line evolution, since they track the grounding line explicitly. Adaptive mesh refinement can further improve accuracy, including fixed grid models that generally perform poorly at coarse resolution. Fixed grid models, with nested grid representations of the grounding line, are able to generate accurate steady state positions, but can be inaccurate over transients. Only one full-Stokes model was included in the intercomparison, and consequently the accuracy of shelfy stream models as approximations of full-Stokes models remains to be determined in detail, especially during transients.

scholarly journals Bubble Dynamics in a Two-Phase Bubbly Mixture

2010 ◽  
Author(s):  
Arvind Jayaprakash ◽  
Sowmitra Singh ◽  
Georges Chahine
Keyword(s):  
Void Fraction ◽  
High Speed ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Discharge Voltage ◽  
Large Bubble ◽  
Water Mixture ◽  
Two Phase ◽  
Mixture Density ◽  
Bubbly Medium

The dynamics of a primary relatively large bubble in a water mixture including very fine bubbles is investigated experimentally and the results are provided to several parallel on-going analytical and numerical approaches. The main/primary bubble is produced by an underwater spark discharge from two concentric electrodes placed in the bubbly medium, which is generated using electrolysis. A grid of thin perpendicular wires is used to generate bubble distributions of varying intensities. The size of the main bubble is controlled by the discharge voltage, the capacitors size, and the pressure imposed in the container. The size and concentration of the fine bubbles can be controlled by the electrolysis voltage, the length, diameter, and type of the wires, and also by the pressure imposed in the container. This enables parametric study of the factors controlling the dynamics of the primary bubble and development of relationships between the bubble characteristic quantities such as maximum bubble radius and bubble period and the characteristics of the surrounding two-phase medium: micro bubble sizes and void fraction. The dynamics of the main bubble and the mixture is observed using high speed video photography. The void fraction/density of the bubbly mixture in the fluid domain is measured as a function of time and space using image analysis of the high speed movies. The interaction between the primary bubble and the bubbly medium is analyzed using both field pressure measurements and high-speed videography. Parameters such as the primary bubble energy and the bubble mixture density (void fraction) are varied, and their effects studied. The experimental data is then compared to simple compressible equations employed for spherical bubbles including a modified Gilmore Equation. Suggestions for improvement of the modeling are then presented.

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