Sessile volatile drop evaporation under microgravity

AbstractThe evaporation of sessile drops of various volatile and non-volatile liquids, and their internal flow patterns with or without instabilities have been the subject of many investigations. The current experiment is a preparatory one for a space experiment planned to be installed in the European Drawer Rack 2 (EDR-2) of the International Space Station (ISS), to investigate drop evaporation in weightlessness. In this work, we concentrate on preliminary experimental results for the evaporation of hydrofluoroether (HFE-7100) sessile drops in a sounding rocket that has been performed in the frame of the MASER-14 Sounding Rocket Campaign, providing the science team with the opportunity to test the module and perform the experiment in microgravity for six consecutive minutes. The focus is on the evaporation rate, experimentally observed thermo-capillary instabilities, and the de-pinning process. The experimental results provide evidence for the relationship between thermo-capillary instabilities and the measured critical height of the sessile drop interface. There is also evidence of the effects of microgravity and Earth conditions on the sessile drop evaporation rate, and the shape of the sessile drop interface and its influence on the de-pinning process.

Download Full-text

Heat Transfer and Flow Instabilities in Ethanol Sessile Drops Under Evaporation

2010 14th International Heat Transfer Conference, Volume 3 ◽

10.1115/ihtc14-22185 ◽

2010 ◽

Author(s):

Benjamin Sobac ◽

David Brutin

Keyword(s):

Heat Transfer ◽

Sessile Drop ◽

Scaling Law ◽

Video Recording ◽

Infrared Camera ◽

Theoretical Work ◽

Evaporation Process ◽

Drop Evaporation ◽

Space Resolution ◽

Sessile Drops

Thanks to a recent increase in space resolution and temperature accuracy of infrared camera device, it’s now possible to perform thermal visualizations of sessile drops under evaporation. Using infrared techniques, we can access local thermal motions inside millimetric drops without perturbing the internal mechanisms. In the full paper, we will provide a literature review of experimental, numerical simulation and theoretical work recently perform on sessile drop evaporation. We will also detail the experimental setup which has been elaborated to realize these thermal observations. Using infrared and visible video recording, we can follow respectively the evolution of the motion inside the drop and the drop shape during evaporation. Using a heat fluxmeter placed below the drop, we can analyze the heat transfer between the substrate and the drop. We will completely describe the evaporation process based on a reference experiment and evidence the existence of several phases during this process. Then, we will dwell on the heat flux transferred to the drop during each step of the evaporation process to obtain very important information about the coupling between flow motion and heat transfer coefficient. Finally, we will present the influence of substrate temperature and drop size on the evaporation process which leads us to build a scaling law and better understand drop evaporation process.

Download Full-text

Evaporative self-assembly of soft colloidal monolayers: The role of particle softness on microstructure

Soft Matter ◽

10.1039/d1sm00841b ◽

2021 ◽

Author(s):

Merin Jose ◽

Madivala G Basavaraj ◽

Dillip Kumar Satapathy

Keyword(s):

Self Assembly ◽

Sessile Drop ◽

Drop Evaporation ◽

Microgel Particles ◽

Sessile Drop Evaporation ◽

Sessile Drops

We investigate the sessile drop evaporation aided self-assembly of microgel particles by varying their softness. Evaporation of sessile drops containing amphiphilic microgel particles at suitable concentrations results in uniform monolayer...

Download Full-text

The shape evolution of liquid droplets in miscible environments

Journal of Fluid Mechanics ◽

10.1017/jfm.2018.535 ◽

2018 ◽

Vol 852 ◽

pp. 422-452 ◽

Cited By ~ 2

Author(s):

Daniel J. Walls ◽

Eckart Meiburg ◽

Gerald G. Fuller

Keyword(s):

Sessile Drop ◽

Liquid Droplet ◽

Leading Edge ◽

Numerical Approach ◽

Shape Evolution ◽

Liquid Droplets ◽

Miscible Liquids ◽

Experimental Findings ◽

Sessile Drops ◽

Pendant Drops

Miscible liquids often come into contact with one another in natural and technological situations, commonly as a drop of one liquid present in a second, miscible liquid. The shape of a liquid droplet present in a miscible environment evolves spontaneously in time, in a distinctly different fashion than drops present in immiscible environments, which have been reported previously. We consider drops of two classical types, pendant and sessile, in building upon our prior work with miscible systems. Here we present experimental findings of the shape evolution of pendant drops along with an expanded study of the spreading of sessile drops in miscible environments. We develop scalings considering the diffusion of mass to group volumetric data of the evolving pendant drops and the diffusion of momentum to group leading-edge radial data of the spreading sessile drops. These treatments are effective in obtaining single responses for the measurements of each type of droplet, where the volume of a pendant drop diminishes exponentially in time and the leading-edge radius of a sessile drop grows following a power law of $t^{1/2}$ at long times. A complementary numerical approach to compute the concentration and velocity fields of these systems using a simplified set of governing equations is paired with our experimental findings.

Download Full-text

Numerical computation of wetting angles of Sn–(3−x)Ag–0.5Cu−x(Bi,In) quaternary Pb-free solder alloy systems on Cu substrate

International Journal of Modern Physics C ◽

10.1142/s0129183120501193 ◽

2020 ◽

Vol 31 (09) ◽

pp. 2050119

Author(s):

Ahmet Mustafa Erer ◽

Mukaddes Ökten Turacı

Keyword(s):

Numerical Model ◽

Numerical Computation ◽

Solder Alloy ◽

Empirical Model ◽

Sessile Drop ◽

Sessile Drop Method ◽

Experimental Results ◽

Cu Substrate ◽

Free Solder ◽

Alloy Systems

This paper was aimed to study of the wetting angle ([Formula: see text]) of Sn–Ag–Cu, Sn–([Formula: see text])Ag–0.5Cu–([Formula: see text])Bi and Sn–([Formula: see text])Ag–0.5Cu–([Formula: see text])In ([Formula: see text], 1 and 2 in wt.%) Pb-free solder alloy systems at various temperatures (250, 280 and 310∘C) on Cu substrate in Ar atmosphere. The new Sn–([Formula: see text])Ag–0.5Cu–xBi and Sn–([Formula: see text])Ag–0.5Cu[Formula: see text]([Formula: see text]) In systems, low Ag content quaternary Pb-free solder alloys, were produced by adding 0.5%, 1% and 2% Bi and In separately to the near-eutectic Sn-3[Formula: see text]wt.%Ag–0.5[Formula: see text]wt.%Cu (SAC305) alloy. The wetting angles of new alloys, Sn[Formula: see text]2.5[Formula: see text]wt.%Ag[Formula: see text]0.5[Formula: see text]wt.%Cu[Formula: see text]0.5[Formula: see text]wt.%Bi (SAC-0.5Bi), Sn[Formula: see text]2[Formula: see text]wt.%Ag[Formula: see text]0.5[Formula: see text]wt.%Cu[Formula: see text]1[Formula: see text]wt.%Bi(SAC-1Bi), Sn[Formula: see text]1[Formula: see text]wt.%Ag[Formula: see text]0.5[Formula: see text]wt.%Cu[Formula: see text]2[Formula: see text]wt.%Bi(SAC-2Bi), Sn[Formula: see text]2.5[Formula: see text]wt.%Ag[Formula: see text]0.5[Formula: see text]wt.%Cu[Formula: see text]0.5[Formula: see text]wt.%In (SAC-0.5In), Sn[Formula: see text]2[Formula: see text]wt.%Ag[Formula: see text]0.5[Formula: see text]wt.%Cu[Formula: see text]1[Formula: see text]wt.%In (SAC-1In) and Sn[Formula: see text]1[Formula: see text]wt.%Ag[Formula: see text]0.5[Formula: see text]wt%.Cu[Formula: see text]2[Formula: see text]wt.%In (SAC-2In) were measured by sessile drop method. Experimental results showed that additions of Bi and In separately to SAC305 resulted in a continuous decrease in the [Formula: see text] up to 1[Formula: see text]wt.% above which the [Formula: see text] value was increased and it is appeared that a correlation among the [Formula: see text], alloys compositions and the test temperatures exists which recommended an empirical model to estimate the [Formula: see text] at a given Bi and In content and temperature for a given alloy systems. The numerical model estimates the [Formula: see text] understandably well with the present work.

Download Full-text

Non-isolated drop impact on surfaces

Journal of Fluid Mechanics ◽

10.1017/jfm.2017.755 ◽

2017 ◽

Vol 835 ◽

pp. 24-44 ◽

Cited By ~ 10

Author(s):

Y. Wang ◽

L. Bourouiba

Keyword(s):

Momentum Transfer ◽

Impact Velocity ◽

Solid Surface ◽

Weber Number ◽

Sessile Drop ◽

Impact Force ◽

New Paradigm ◽

Existence Conditions ◽

Secondary Droplets ◽

Sessile Drops

Upon impact on a solid surface, a drop expands into a sheet, a corona, which can rebound, stick or splash and fragment into secondary droplets. Previously, focus has been placed on impacts of single drops on surfaces to understand their splash, rebound or spreading. This is important for spraying, printing, and environmental and health processes such as contamination by pathogen-bearing droplets. However, sessile drops are ubiquitous on most surfaces and their interaction with the impacting drop is largely unknown. We report on the regimes of interactions between an impacting drop and a sessile drop. Combining experiments and theory, we derive the existence conditions for the four regimes of drop–drop interaction identified, and report that a subtle combination of geometry and momentum transfer determines a critical impact force governing their physics. Crescent-moon fragmentation is most efficient at producing and projecting secondary droplets, even when the impacting drop Weber number would not allow for splash to occur on the surface considered if the drop were isolated. We introduce a critical horizontal impact Weber number $We_{c}$ that governs the formation of a sheet from the sessile drop upon collision with the expanding corona of the impacting drop. We also predict and validate important properties of the crescent-moon fragmentation: the extension of its sheet base and the ligaments surrounding its base. Finally, our results suggest a new paradigm: impacts on most surfaces can make a splash of a new kind – a crescent-moon – for any impact velocity when neighbouring sessile drops are present.

Download Full-text