Numerical Simulation of the Interaction Between Two Bubbles Rising in the Water

2010 ◽  
Author(s):  
Ren-qing Zhu ◽  
Yan-cheng Li ◽  
Yong-yan Ni ◽  
Pei-tao Zhang
Keyword(s):  
Bubble Diameter ◽  
Separation Distance ◽  
Bubble Deformation ◽  
Vof Model ◽  
Merging Process ◽  
History Of ◽  
Fluent Software ◽  
Movement And Deformation ◽  
Two Bubbles ◽  
Velocity History

Based on the VOF model, the rising movement and deformation of two bubbles placed horizontally or vertically with separation distance under the action of the buoyancy are simulated by using FLUENT software. The effects of distance between two bubbles on deformation, coalescence, rising velocity and path are considered. The bubble deformation is monitored and the change of velocity with time is analyzed. The influence of bubble diameter on rising and merging are discussed and the velocity history of bubble is obtained in rising and merging process. The results show that: The distance has great effect on the interaction between two bubbles in rising and merging process, the smaller the bubble spacing is, the stronger the interaction between bubbles is, and the larger the bubble diameter is, the larger the affected area is. The two bubbles placed vertically attract each other in rising process. The upper bubble has accelerative effect on the speed of lower bubble. The two bubbles placed horizontally in water attract and exclude each other periodically.

scholarly journals Verification of CFD tool for simulation of cavitating flows in hydraulic systems

2017 ◽  
Vol 19 (5) ◽  
pp. 653-665 ◽  
Author(s):  
Agnieszka Niedźwiedzka ◽  
Seweryn Lipiński ◽  
Sebastian Kornet
Keyword(s):  
Statistical Analysis ◽  
Volume Fraction ◽  
Correlation Coefficients ◽  
Hydraulic Systems ◽  
Computer Methods ◽  
Main Challenge ◽  
Cavitation Intensity ◽  
History Of ◽  
Fluent Software ◽  
Verification Process

Cavitation is an undesirable phenomenon in hydraulic systems, as it causes erosion and noise. The main difficulty in cavitation prediction when using Fluent software is lack of an openly accessible tool for implementation of a freely chosen homogeneous cavitation model. In this paper the main challenge is to make such a tool, user defined function (UDF). The second challenge is to use a qualitative method in the assessment of the results of verification process. Three cavitation models are verified in Fluent 14.5: Singhal et al., Schnerr & Sauer and Zwart et al. The verification is based on the benchmark example from the Cavitation Modeling tutorial. Three methods of the algorithms verification are used: analysis of the convergence history of volume fraction, comparison of vapour volume fractions and statistical analysis of these data. The original achievements are not only the verified codes but also statistical analysis based on the computer methods of image analysis performed using two correlation coefficients: the first based on the cavitation intensity, and the second based on the changes of the cloud shape. The results of the analyses do not give any reasons to reject the UDFs. The appendix contains the analysed codes (available with the online version of this paper).

Thermocapillary migration of bubbles: convective effects at low Péclet number

2001 ◽  
Vol 443 ◽  
pp. 377-401 ◽  
Author(s):  
A. M. LESHANSKY ◽  
O. M. LAVRENTEVA ◽  
A. NIR
Keyword(s):  
Peclet Number ◽  
Large Time ◽  
Sufficient Conditions ◽  
Steady Motion ◽  
Separation Distance ◽  
Péclet Number ◽  
Thermocapillary Migration ◽  
Initial Separation ◽  
The Individual ◽  
Two Bubbles

The effect of a weak convective heat transfer on the thermocapillary interaction of two bubbles migrating in an externally imposed temperature gradient is examined. It is shown that, for short and moderate separation distances, the corrections to the individual migration velocities of the bubbles are of O(Pe), where Pe is Péclet number. For separation distances larger than O(Pe−1/2) the correction is of O(Pe2) as previously found for an isolated drop. The perturbations to the bubble velocities have opposite signs: the motion of the leading bubble is enhanced while the motion of the trailing one is retarded. A newly found feature is that equal-sized bubbles, which otherwise would move with equal velocities, acquire a relative motion apart from each other under the influence of convection. For slightly unequal bubbles there are three different regimes of large-time asymptotic behaviour: attraction up to the collision, infinite growth of the separation distance, and a steady migration with equal velocities, the steady motion separation distance being a function of the parameters of the problem. Sufficient conditions for the realization of each regime are given in terms of the Péclet number, initial separation and radii ratio.

scholarly journals Unsteady Effects During Resistance Tests on a Ship Model in a Towing Tank

2008 ◽  
Vol 52 (04) ◽  
pp. 263-273
Author(s):  
Lawrence J. Doctors ◽  
Alexander H. Day ◽  
David Clelland
Keyword(s):  
Wave Resistance ◽  
Excellent Correlation ◽  
Experiment Data ◽  
Towing Tank ◽  
Ship Model ◽  
History Of ◽  
Rate Of Decay ◽  
Unsteady Effects ◽  
Velocity History ◽  
Resistance Tests

It is known that there are oscillations in the wave resistance during the constant-velocity phase of a towing-tank resistance test on a ship model. In this work, the unsteady thin-ship resistance theory has been applied to this case. The results have been compared with experiment data obtained using a towing carriage the velocity history of which can be programmed. It is demonstrated here that generally excellent correlation exists between the theory and the experiments. In particular, one can predict the influence of Froude number, rate of acceleration, and type of smoothing of the acceleration on the characteristics of the oscillations. These characteristics include the amplitude, rate of decay, frequency, and phasing of the oscillations in the curve of wave resistance versus time.

Cavitation Bubble Collapse Near a Heated Wall and Its Effect on the Heat Transfer

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Bin Liu ◽  
Jun Cai ◽  
Xiulan Huai ◽  
Fengchao Li
Keyword(s):  
Heat Transfer ◽  
Cavitation Bubble ◽  
Stokes Equations ◽  
Saturated Vapor ◽  
Bubble Diameter ◽  
Bubble Radius ◽  
Heated Wall ◽  
Bubble Collapse ◽  
Flow State ◽  
Vof Model

In the present work, a numerical investigation on the mechanism of heat transfer enhancement by a cavitation bubble collapsing near a heated wall has been presented. The Navier–Stokes equations and volume of fluid (VOF) model are employed to predict the flow state and capture the liquid-gas interface. The model was validated by comparing with the experimental data. The results show that the microjet violently impinges on the heated wall after the bubble collapses completely. In the meantime, the thickness of the thermal boundary layer and the wall temperature decrease significantly within the active scope of the microjet. The fresh low-temperature liquid and the impingement brought by the microjet should be responsible for the heat transfer reinforcement between the heated wall and the liquid. In addition, it is found that the impingement width of the microjet on the heated wall always keeps 20% of the bubble diameter. And, the enhancement degree of heat transfer significantly depends on such factors as stand-off distance, saturated vapor pressure, and initial bubble radius.

The Change of Velocity and Pressure of Micro Bubble in Multi-Phases Flow in Mesoscopic Scale

2014 ◽  
Vol 722 ◽  
pp. 97-100 ◽  
Author(s):  
Zai Shuai Ling ◽  
Wei Long ◽  
Zhang Yong Wu
Keyword(s):  
Bubble Velocity ◽  
Dissolution Mechanism ◽  
Flow State ◽  
Mesoscopic Scale ◽  
Vof Model ◽  
Key Factor ◽  
Micro Bubble ◽  
Fluent Software ◽  
Bubble Rising ◽  
Pressure Changes

The dissolution mechanism of air and formation mechanism of bubble in the scopic-scale,and the change rule of the velocity and pressure of bubble in the rising process,made the theoretical analysis and explanation. Be based on VOF model,with the help of Fluent software,For the single bubble rising in the water by numerical simulation;The results show that liquid phase flow state is a key factor affecting the speed of the bubbles rise;Pressure difference is the main reason cause the jets and bubbles deformation.Through the above process in the rising process of the bubble velocity and pressure changes, and a detailed analysis of inquiry, the pressure and velocity of the bubble rising process show up more realistic.

scholarly journals Interactions between gas–liquid mass transfer and bubble behaviours

2019 ◽  
Vol 6 (5) ◽  
pp. 190136 ◽  
Author(s):  
Xin Li ◽  
Weiwen Wang ◽  
Pan Zhang ◽  
Jianlong Li ◽  
Guanghui Chen
Keyword(s):  
Mass Transfer ◽  
Bubble Diameter ◽  
Water System ◽  
Mass Transfer Process ◽  
Liquid Mass ◽  
Fluid Field ◽  
Vof Model ◽  
Liquid Mass Transfer ◽  
The Relationship ◽  
Two Sides

Interactions between gas–liquid mass transfer and bubble behaviours were investigated to improve the understanding of the relationship between the two sides. The CO 2 /N 2 -water system was applied to study the bubble behaviours based on the volume-of-fluid (VOF) model. The mass transfer conditions were taken into consideration when the fluid field was analysed. The bubble behaviours were compared with and without mass transfer. The results show that the absolute slopes of the curves for mass fraction inside the single rising bubbles, with diameters from 3 to 6 mm, decrease from 0.09325 to 0.02818. It means that small single bubbles have higher mass transfer efficiency. The daughter bubbles of cutting behaviour and initial side-by-side bubbles of coalescence behaviour also perform better than the initial large bubbles and coalesced bubbles, respectively. The bubble behaviours affect the mass transfer process. However, the latter also reacts upon the former. The critical intervals between the side-by-side bubbles decrease from 2.0 to 0.9 mm when the bubble diameter changes from 3 to 7 mm. For the coalescence behaviour without mass transfer, the critical intervals are larger because there is no influence of concentration around the bubbles on the bubble motion. The coalescence of cut daughter bubbles is also influenced by the concentration. It was suggested that the interaction between the gas–liquid mass transfer and bubble behaviours cannot be ignored.

scholarly journals Interaction between two spherical bubbles rising in a viscous liquid

2011 ◽  
Vol 673 ◽  
pp. 406-431 ◽  
Author(s):  
YANNICK HALLEZ ◽  
DOMINIQUE LEGENDRE
Keyword(s):  
Stokes Equations ◽  
Bubble Diameter ◽  
Bubble Radius ◽  
Three Dimensional ◽  
Potential Effect ◽  
Navier Stokes ◽  
General Description ◽  
Wake Effect ◽  
Spherical Bubbles ◽  
Two Bubbles

The three-dimensional flow around two spherical bubbles moving in a viscous fluid is studied numerically by solving the full Navier–Stokes equations. The study considers the interaction between two bubbles for moderate Reynolds numbers (50 ≤ Re ≤ 500, Re being based on the bubble diameter) and for positions described by the separation S (2.5 ≤ S ≤ 10, S being the distance between the bubble centres normalised by the bubble radius) and the angle θ (0° ≤ θ ≤ 90°) formed between the centreline and the direction perpendicular to the direction of the motion. We provide a general description of the interaction extending the results obtained for two bubbles moving side by side (θ = 0°) by Legendre, Magnaudet & Mougin (J. Fluid Mech., vol. 497, 2003, p. 133) and for two bubbles moving in line (θ = 90°) by Yuan & Prosperetti J. Fluid Mech., vol. 278, 1994, p. 325). Simple models based on physical arguments are given for the drag and lift forces experienced by each bubble. The interaction is the combination of three effects: a potential effect, a viscous correction (Moore's correction) and a significant wake effect observed on both the drag and the transverse forces of the second bubble when located in the wake of the first one.

scholarly journals Frontal and tilted PDV probes for measuring velocity history of laser-shock induced calibrated particles

2014 ◽  
Vol 500 (14) ◽  
pp. 142022 ◽  
Author(s):  
G Prudhomme ◽  
P Mercier ◽  
L Berthe ◽  
J Bénier ◽  
P-A Frugier
Keyword(s):  
Laser Shock ◽  
History Of ◽  
Velocity History
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