Numerical Analysis of Bubble Behavior with Thermocapillary Flows in an Open Cylindrical Container (original) (raw)

Migration of Bubbles Under the Combined Action of Thermocapillary and Gravity

2007

Numerical computations of the motion of one bubble under the effect of thermocapillary and gravity presented. In the simulations we used Immersed Front Tracking method for multi-fluid flows. The material properties of the drop/bubble fluid and the ambient fluid are different and surface tension depends on the temperature. Simulations were made with constant Marangoni, Reynolds and Capillary number, different dynamic version of the Bond numbers which include gravity. Different gravitational force significantly changes the motion of the bubble in the domain, which presented in the text in detail.

Thermocapillary bubble migration at high Reynolds and Marangoni numbers under low gravity

Journal of Colloid and Interface Science, 1996

Prandtl number ( Eq. [ 3 ] ) . Since a characteristic bubble The thermocapillary migration of single bubbles at high Reyvelocity cannot be determined a priori, the velocity U 0 nolds and Marangoni numbers has been investigated. Experiments derived from the tangential stress balance at the free suron the transient behavior of moving bubbles with Marangoni numface is used for scaling the migration velocity in Eqs. [1] bers up to Mg Å 2500 were carried out in the Bremen drop tower. and [ 2 ] : After a long heating period, a sufficiently linear temperature gradient was established with paraffin liquids. For 4.74 s of strongly reduced gravity the speed of the bubble migration was observed Here, s denotes the surface tension, h the dynamic viscosity, Key Words: thermocapillary bubble dynamic; low gravity experin the kinematic viscosity, a the temperature diffusivity, R ments; high Reynolds and Marangoni numbers.

Numerical study of thermocapillary migration of a bubble in a channel with an obstruction

Physics of Fluids, 2019

Fully resolved numerical simulations are used to examine the thermocapillary motion of a two- and three-dimensional fully deformable bubble in a channel with an obstruction. A front-tracking/finite volume method is used to solve the Navier-Stokes equations coupled with the energy conservation equation. The results show that, for a fixed obstruction and channel size, the influence coefficient α, defined as the ratio of arrival time in channels with and without an obstruction, increases with increasing Marangoni (Ma) number for both two- and three-dimensional flows, whereas an increase in the Reynolds (Re) number leads to an increase in the influence coefficient in two-dimensional flows but a decrease in three-dimensional flows. Moreover, a change in the Capillary (Ca) number does not have a visible effect on the thermocapillary motion if the width of the narrow part of the channel is larger than the bubble diameter. Results for both two- and three-dimensional flows show that the infl...

Analysis of bubble growth on a hot plate during decompression in microgravity

International Journal of Thermal Sciences, 2016

The focus of the present work is the modeling of bubble growth on a hot plate during decompression (depressurization) of a volatile liquid at temperatures close to saturation and in the presence of dissolved gas. In particular, this work presents an organized attempt to analyze data obtained from an experiment under microgravity conditions. In this respect, a bubble growth mathematical model is developed and solved at three stages, all realistic under certain conditions but of increasing physical and mathematical complexity: At the first stage, the temperature variation both in time and space is ignored leading to a new semi analytical solution for the bubble growth problem. At the second stage, the assumption of spatial uniformity of temperature is relaxed and instead a steady linear temperature profile is assumed in the liquid surrounding the bubble from base to apex. The semi analytical solution is extended to account for the two dimensionality of the problem. As the predictions of the above models are not in agreement with the experimental data, at the third stage an inverse heat transfer problem is set up. The third stage model considers an arbitrary average bubble temperature time profile and it is solved numerically using a specifically designed numerical technique. The unknown bubble temperature temporal profile is estimated by matching theoretical and experimental bubble growth curves. A discussion follows on the physical mechanisms that may explain the evolution of the average bubble temperature in time.

An analysis of Bubble Migration in Horizontal Thermo-Capillarity Using the VOF Modeling

Applied Sciences

Due to various engineering applications, spontaneous bubble movement on the heated surface has brought huge attention. This work numerically studied the bubble migration driven by the thermo-capillary force under the temperature gradients perpendicular to the gravity direction. This problem is constructed in a two-dimensional domain, and the volume of fluid (VOF) method is adopted to capture the properties of the bubble interface between the vapor and the liquid. One still vapor bubble is initially positioned at the center of the liquid domain, and the temperature gradient is applied to two side walls. The results show that the bubble with a size greater than the capillary length can only oscillate near the initial position even with a larger temperature gradient. The deformation of the bubble such as spheroid and spherical cap can be found around this regime. However, the movement of the bubble with a size smaller than the capillary length is significant under a higher temperature ...

Characteristics of bubble behavior in microgravity conditions

CHARACTERISTICS OF BUBBLE BEHAVIOR IN MICROGRAVITY CONDITIONS Thilanka Munasinghe The main objective of this thesis is to study the characteristics of bubbles in pool boiling under microgravity conditions with and without the influence of a magnetic field. In order to create microgravity conditions, the parabolic path of an aircraft was used for a period of 20-30 seconds, during

THERMOCAPILLARY MIGRATION OF BUBBLES AT LARGE REYNOLDS NUMBERS

International Journal of Multiphase Flow, 1998

AbstractÐThe thermocapillary movement of bubbles has been investigated for large Reynolds numbers. A numerical analysis of the¯ow ®eld around a bubble has been carried out for arbitrary Marangoni (Ma) numbers. For small Ma the¯ow ®eld has been calculated using a matched asymptotic procedure. A comparison is made of the nondimensional bubble velocity and the temperature gradient at the bubble surface, calculated numerically, with analytical results for large and small values of Ma, and with numerical results obtained previously. The expansion for large Ma has also been proposed by . For Maw1 the presence of both the thermal boundary layer and the wake impose limitations in the numerical calculations. The calculations have been carried out for values of Ma signi®cantly larger than those previously obtained. #

Numerical investigation of the role of heat transfer in bubble dynamics

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems, 2017

Bubble dynamics is generally described by the well-known Rayleigh-Plesset (R-P) equation in which the bubblepressure (or equivalently the bubble density) is predefined by assuming a polytropic gas equation of state with common assumptions to include either isothermal or adiabatic bubble behaviour. The present study examines the applicability of this assumption by assuming that the bubble density obeys the ideal gas equation of state, while the heat exchange with the surrounding liquid is estimated as part of the numerical solution. The numerical model employed includes the solution of the Navier-Stokes equations along with the energy equation, while the liquid- gas interface is tracked using the Volume of Fluid (VOF) methodology; phase-change mechanism is assumed to be insignificant compared to bubble heat transfer mechanism. To assess the effect of heat transfer and gas equation of state on bubble behaviour, simulations are also performed for the same initial conditions by using a ...