scholarly journals Theory for the coalescence of viscous lenses

2021 ◽  
Vol 928 ◽  
Author(s):  
Walter Tewes ◽  
Michiel A. Hack ◽  
Charu Datt ◽  
Gunnar G. Peng ◽  
Jacco H. Snoeijer
Keyword(s):  
Large Scale ◽  
Thin Sheet ◽  
Matched Asymptotics ◽  
Drop Coalescence ◽  
Liquid Lenses ◽  
Liquid Lens ◽  
Viscous Drops ◽  
Self Similar Solution ◽  
Self Similar ◽  
Bridge Dynamics

Drop coalescence occurs through the rapid growth of a liquid bridge that connects the two drops. At early times after contact, the bridge dynamics is typically self-similar, with details depending on the geometry and viscosity of the liquid. In this paper we analyse the coalescence of two-dimensional viscous drops that float on a quiescent deep pool; such drops are called liquid lenses. The analysis is based on the thin-sheet equations, which were recently shown to accurately capture experiments of liquid lens coalescence. It is found that the bridge dynamics follows a self-similar solution at leading order, but, depending on the large-scale boundary conditions on the drop, significant corrections may arise to this solution. This dynamics is studied in detail using numerical simulations and through matched asymptotics. We show that the liquid lens coalescence can involve a global translation of the drops, a feature that is confirmed experimentally.

Events before droplet splashing on a solid surface

2010 ◽  
Vol 647 ◽  
pp. 163-185 ◽  
Author(s):  
MADHAV MANI ◽  
SHREYAS MANDRE ◽  
MICHAEL P. BRENNER
Keyword(s):  
Surface Tension ◽  
Solid Surface ◽  
Liquid Droplet ◽  
Thin Sheet ◽  
Initial Contact ◽  
Viscous Forces ◽  
Self Similar Solution ◽  
Self Similar ◽  
Physical Effects ◽  
The Impact

A high-velocity (≈1 ms−1) impact between a liquid droplet (≈1 mm) and a solid surface produces a splash. Classical observations traced the origin of this splash to a thin sheet of fluid ejected near the impact point, though the fluid mechanical mechanism leading to the sheet is not known. Mechanisms of sheet formation have heretofore relied on initial contact of the droplet and the surface. In this paper, we theoretically and numerically study the events within the time scale of about 1 μs over which the coupled dynamics between the gas and the droplet becomes important. The droplet initially tries to contact the substrate by either draining gas out of a thin layer or compressing it, with the local behaviour described by a self-similar solution of the governing equations. This similarity solution is not asymptotically consistent: forces that were initially negligible become relevant and dramatically change the behaviour. Depending on the radius and impact velocity of the droplet, we show that the solution is overtaken by initially subdominant physical effects such as the surface tension of the liquid–gas interface or viscous forces in the liquid. At low impact velocities surface tension stops the droplet from impacting the surface, whereas at higher velocities viscous forces become important before surface tension. The ultimate dynamics of the interface once droplet viscosity cannot be neglected is not yet known.

On a self-similar solution for the decay of turbulent bursts

1992 ◽  
Vol 3 (4) ◽  
pp. 319-341 ◽  
Author(s):  
S. P. Hastings ◽  
L. A. Peletier
Keyword(s):  
Asymptotic Behaviour ◽  
Physical Parameter ◽  
Dimensional Analysis ◽  
Existence And Uniqueness ◽  
The Self ◽  
Similar Solution ◽  
Self Similar Solution ◽  
Eigenvalue Parameter ◽  
Self Similar ◽  
Similar Solutions

We discuss the self-similar solutions of the second kind associated with the propagation of turbulent bursts in a fluid at rest. Such solutions involve an eigenvalue parameter μ, which cannot be determined from dimensional analysis. Existence and uniqueness are established and the dependence of μ on a physical parameter λ in the problem is studied: estimates are obtained and the asymptotic behaviour as λ → ∞ is established.

Self-Similar Solution of an RC Transmission Line

1972 ◽  
Vol 40 (3) ◽  
pp. 484-486 ◽  
Author(s):  
K. E. Lonngren ◽  
W. F. Ames ◽  
H. C. S. Hsuan ◽  
I. Alexeff ◽  
William Wing
Keyword(s):  
Transmission Line ◽  
Similar Solution ◽  
Self Similar Solution ◽  
Self Similar

The hydraulics of a stratified fluid flowing through a contraction

1993 ◽  
Vol 251 ◽  
pp. 355-375 ◽  
Author(s):  
Laurence Armi ◽  
Richard Williams
Keyword(s):  
Flow Rate ◽  
Fluid Flows ◽  
Stratified Fluid ◽  
Wave Mode ◽  
Similar Solution ◽  
Constant Density ◽  
Self Similar Solution ◽  
Hydraulic Theory ◽  
Self Similar

The steady hydraulics of a continuously stratified fluid flowing from a stagnant reservoir through a horizontal contraction was studied experimentally and theoretically. As the channel narrows, the flow accelerates through a succession of virtual controls, at each of which the flow passes from sub-critical to supercritical with respect to a particular wave mode. When the narrowest section acts as a control, the flow is asymmetric about the narrowest section, supercritical in the divergent section and self- similar throughout the channel. With increased flow rate a new enclosed self-similar solution was found with level isopycnals and velocity uniform with depth. This flow is only symmetric in the immediate neighbourhood of the narrowest section, and in the divergent section remains supercritical with respect to higher internal modes, has separation isopycnals and splits into one or more jets separated by regions of stagnant, constant-density fluid. Flows which are subcritical with respect to lowest modes can also be asymmetric about the narrowest section for higher internal modes. The experiments are interpreted using steady, inviscid hydraulic theory. Solutions require separation isopycnals and regions of stationary, constant-density fluid in the divergent section.

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