Influence of molecular structure of alcohol-water mixtures on bubble behaviour and bubble surface mobility

Basařová, Pavlína; Pišlová, J.; Mills, John; Orvalho, Sandra

doi:10.1016/j.ces.2018.07.008

Cited by 26 publications

(20 citation statements)

References 33 publications

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“…Furthermore, the discrepancies could be caused by the unknown hydrodynamic boundary conditions at the bubble surface. As reported recently, the bubble surface in the considered system can be partially or even completely slip (Basarová et al, 2018).…”

supporting

confidence: 52%

Effects of gravity level on bubble detachment, rise, and bouncing with a free surface

Suñol

González-Cinca

2019

International Journal of Multiphase Flow

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Bubble detachment, rise, and bouncing upon impact with a free surface is studied experimentally in variable gravity conditions. Previous investigations focused on the effects of fluid properties such as viscosity or surface tension on the rise and bouncing dynamics. Gravity force is a crucial factor in the detachment, rise and bouncing processes. However, the effect of different gravity levels has never been studied experimentally. In this paper we analyze the role of gravity in the detachment, rise velocity and bouncing motion of millimetric bubbles colliding with a free surface. Single air bubbles in ethanol are detached from a nozzle by the buoyancy force. After reaching a terminal velocity, the rising bubble interacts with the free surface in a bouncing process prior to coalescence. The equivalent bubble diameter at detachment decreases as the gravity level increases, in agreement with the theoretical prediction. An expression for the terminal velocity as a function of gravity is proposed. The terminal velocity is found to increase with the gravity level, although bubbles are smaller at higher values of gravity. The bouncing process has been modelled by a damped oscillator, in which the free surface acts as an elastic membrane. An expression for the frequency of bouncing as a function of gravity has been obtained, showing a good agreement with the experimental results. The motion of the bubble during the bouncing process can be approximated by an underdamped oscillator even if viscosity is negligible. Therefore, viscosity is not the main responsible for damping, which is probably due to energy transfer from the bubble to the fluid in the form of vortex and surface waves generation.

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supporting

confidence: 52%

Effects of gravity level on bubble detachment, rise, and bouncing with a free surface

Suñol

González-Cinca

2019

International Journal of Multiphase Flow

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“…Sathe et al [4] used the discrete wavelet transform algorithm to reconstruct the PIV flow field distribution around the bubble, which reduced the interference signal during the PIV flow field acquisition process and further obtained the flow field characteristics like phase drift velocity. Basarova et al [5] experimentally investigated the ascending motion behavior of spherical bubbles in different concentrations of water ethanol and water propanol and obtained characteristic values such as bubble rising velocity and bubble size, which proved the effect of the concentration of the two solutions on the liquid properties and the gas-liquid interface. Maldonado et al [6] experimentally studied a single bubble of 2.5 mm diameter rises in different liquids.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of Bubble Rising and Coalescence Characteristics under Flow Pulsation Based on Particle Method

Chen

Zhang

Guo

et al. 2019

Science and Technology of Nuclear Installations

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Two-phase flow instability may occur in nuclear reactor systems, which is often accompanied by periodic fluctuation in fluid flow rate. In this study, bubble rising and coalescence characteristics under inlet flow pulsation condition are analyzed based on the MPS-MAFL method. To begin with, the single bubble rising behavior under flow pulsation condition was simulated. The simulation results show that the bubble shape and rising velocity fluctuate periodically as same as the inlet flow rate. Additionally, the bubble pairs’ coalescence behavior under flow pulsation condition was simulated and compared with static condition results. It is found that the coalescence time of bubble pairs slightly increased under the pulsation condition, and then the bubbles will continue to pulsate with almost the same period as the inlet flow rate after coalescence. In view of these facts, this study could offer theory support and method basis to a better understanding of the two-phase flow configuration under flow pulsation condition.

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“…The value of the propanol mole fraction corresponding to this critical concentration lies between 0.07 (determined by the surface tension isotherms [6]) and 0.1 (based on mass spectroscopy and X-ray diffraction [5]). The result is a significant drop in surface tension, significant mixing volume and heat, and a change in bubble surface mobility [7]. Very strong hydrogen bonds also lead to multiple increase in viscosity [6,8,9].…”

Section: Introductionmentioning

confidence: 99%

“…In the case of aqueous solutions of alcohols, it was found that the drag coefficient varied in relation to alcohol concentrations [7]. Alcohol molecules present in solutions with very low propanol concentrations (x P ≤ 0.005) diffuse onto the phase interface relatively fast and the solutions behave as surfactant solutions.…”

Section: Introductionmentioning

confidence: 99%

“…The shear stress that the liquid exerts on the bubble surface can be reduced, allowing the gradient of the surface tension to be equalized. As a result, there is facilitation of alcohol molecules desorbing from the phase interface, consequently reducing the drag force [7]. Transitioning to the subsequent region is significant and relates to micro-aggregate formation.…”

Section: Introductionmentioning

confidence: 99%

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Bubble Rise Velocity and Surface Mobility in Aqueous Solutions of Sodium Dodecyl Sulphate and n-Propanol

2019

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Aqueous solutions of simple alcohols exhibit many anomalies, one of which is a change in the mobility of the bubble surface. This work aimed to determine the effect of the presence of another surface-active agent on bubble rise velocity and bubble surface mobility. The motion of the spherical bubble in an aqueous solution of n-propanol and sodium dodecyl sulphate (SDS) was monitored by a high-speed camera. At low alcohol concentrations (xP < 0.01), both the propanol and SDS molecules behaved as surfactants, the surface tension decreased and the bubble surface was immobile. The effect of the SDS diminished with increasing alcohol concentrations. In solutions with a high propanol content (xP > 0.1), the SDS molecules did not adsorb to the phase interface and thus, the surface tension of the solution was not reduced with the addition of SDS. Due to the rapid desorption of propanol molecules from the bottom of the bubble, a surface tension gradient was not formed. The drag coefficient can be calculated using formulas for the mobile surface of a spherical bubble.

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Influence of molecular structure of alcohol-water mixtures on bubble behaviour and bubble surface mobility

Cited by 26 publications

References 33 publications

Effects of gravity level on bubble detachment, rise, and bouncing with a free surface

Effects of gravity level on bubble detachment, rise, and bouncing with a free surface

Numerical Study of Bubble Rising and Coalescence Characteristics under Flow Pulsation Based on Particle Method

Bubble Rise Velocity and Surface Mobility in Aqueous Solutions of Sodium Dodecyl Sulphate and n-Propanol

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