Experimental analysis of the breakage of a liquid bridge under microgravity conditions (original) (raw)
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Slender axisymmetric dielectric liquid bridges are made stable by the action of an axial electric field. In this paper, the subsequent dynamics of a slender liquid bridge after turning off the electric field is considered. The evolution in time of the bridge profile is investigated both theoretically and experimentally. A one-dimensional model is used to simulate the dynamic response of the system. Experiments are performed applying an axial electric field to a liquid bridge of 1 mm of diameter, and turning-off the electric field. The evolution of the liquid bridge is recorded using a video camera, and the digitized images are analysed. Good agreement between computations and experiments is found.
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2001 Conference and Exhibit on International Space Station Utilization, 2001
This is a preprint or reprint of a paper intended for presentation at a conference. Because changes may be made before formal publication, this is made available with the understanding that it will not be cited or reproduced without the permission of the author.
European Journal of Mechanics - B/Fluids, 2003
The stability of axisymmetric liquid bridges held between non-equal circular supporting disks, and subjected to an axial acceleration, has been analyzed both theoretically and experimentally. Some characteristics of the breaking process which takes place when the stability limit of minimum volume is reached (mainly the dependence with the disks separation of the volume of the liquid drops resulting after the liquid bridge breakage) have been theoretically studied by using standard asymptotic expansion techniques. From the analysis of the nature of the unstable equilibrium shapes of minimum volume at the stability limit it is concluded that the relative volume of the main drops resulting from the liquid bridge rupture drastically change as the disks separation grows. Theoretical predictions have been experimentally checked by working with very small size liquid bridges (supporting disks being some 1 millimeter in diameter), the agreement between theoretical predictions and experimental results being remarkable.
Study of a liquid bridge subjected to interface shear stresses
Acta Astronautica, 2011
We report on numerical and experimental study of two-phase flows in a tall annulus. The geometry corresponds to a cylindrical liquid column co-axially placed into an outer cylinder with solid walls. The internal column consists of solid supports at the bottom and top, while the central part is a liquid zone filled with viscous liquid and kept in its position by surface tension. Gas enters into the annular duct and entrains initially quiescent liquid. The liquid bridge interface is deformed by gravity and by a co-axial gas flow which is co-and counter directed with respect to gravity. A new experimental set-up including an optical system for precise measurements of the interface displacement has been designed and developed. In the experiments silicone oil 5cSt was used as a test liquid and air as gas. On numerical side the dynamical response of an isothermal liquid bridge to a coaxial gas flow is examined by simulations of the Navier-Stokes equations. The attention is focused on the following points: time-dependent formation of the equilibrium shape of a liquid bridge in gravity conditions and its deformation by a gas flow, simulation of a flow pattern in a liquid/gas system with deformed free surface. The comparison of the numerical and experimental results for the interface deformation exhibits a satisfactory agreement.
Effect of Large Eccentric Rotation on the Stability of Liquid Bridges
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A cylindrical liquid bridge supported between two circular-shaped disks in isorotation is considered. The effect of an offset between the rotation axis and the axis of the two support- ing disks (eccentricity) on the stability of the liq- uid bridge is investigated. In a previous work a numerical method used to determine the stability limit for different values of eccentricity was vali- dated comparing these results with analytical and experimental results for small eccentricity values, recovering the same behavior. In this work we usethenumerical method toextend theanalysisto large values of the eccentricity, finding a change in the bifurcation diagrams. The evolution of sta- ble and unstable shapes for different bifurcation curves is also compared. Keyword: Liquid bridge; Microgravity; Stabil- ity.
Dynamics of nearly unstable axisymmetric liquid bridges
Physics of Fluids, 2011
The dynamics of a noncylindrical, axisymmetric, marginally unstable liquid bridge between two equal disks is analyzed in the inviscid limit. The resulting model allows for the weakly nonlinear description of both the (first stage of) breakage for unstable configurations and the (slow) dynamics for stable configurations. The analysis is made for both slender and short liquid brides. In the former range, the dynamics breaks reflection symmetry on the midplane between the supporting disks and can be described by a standard Duffing equation, while for short bridges reflection symmetry is preserved and the equation is still Duffing-like but exhibiting a quadratic nonlinearity. The asymptotic results compare well with existing experiments.
Chemical Engineering Science, 2001
Deformation and breakup of bridges of Newtonian and non-Newtonian #uids held captive between two disks that are separated from one another at a constant speed are studied computationally. When the liquid bridge is at the incipience of breakup, a thin liquid thread connects two large volumes of #uid that are pendant from and sessile on the top and bottom disks. High viscosity and elasticity are known from experiments to lead to formation of long threads: these are precursors of satellite droplets which are usually unwanted in applications such as ink-jet printing. To investigate the role of shear-thinning in suppressing long threads and to separate the e!ect of elasticity from shear-thinning, the rheology of non-Newtonian #uids is described here by a Carreau model which simply accounts for shear-thinning behavior. When the dynamics is axially symmetric with respect to the common axis of the bridge and the disks, the physics is described by a spatially two-dimensional (2-D) theory. In addition to this fully 2-D theory, a one-dimensional (1-D) theory based on the slender-jet approximation is also developed here. Both the 2-D and 1-D problems are solved by a method of lines employing the "nite element method for spatial discretization and an adaptive "nite di!erence technique for time integration. The computational results show that the limiting bridge length¸B at breakup increases with increasing stretching speed ; for both Newtonian and shear-thinning #uids. However, in the case of high-viscosity bridges, as compared to a Newtonian #uid with viscosity equal to the zero shear-rate viscosity of a shear-thinning #uid, the rate at which¸B of a shear-thinning #uid varies with ; becomes less pronounced as ; increases. Furthermore, in the case of low-viscosity bridges, the axial location along the thread at which the bridge breaks switches from the vicinity of the bottom of the bridge to its top and then back to its bottom again as ; is increased. This switch in the breakup location has important implications in determining the fate of satellite droplets if any are formed. It is also shown that both the shape of the bridge and that of the liquid thread are profoundly a!ected by shear-thinning behavior. 1-D models have of course been previously used but often without direct comparison to experimental measurements or predictions made with exact 2-D models. It is shown here for the "rst time that 1-D models are remarkably accurate at low stretching speeds but fail at high stretching speeds. Furthermore, it is demonstrated that as the bridges thin, the dynamics in the vicinity of the location where the bridge radius is smallest follow scaling laws recently developed by others who have analyzed the local behavior of the governing equations close to pinch-o!.