Engineers discover method to create upward water fountain in deep water
Fountain created by lasers, Marangoni Effect is the cause

Date:
January 18, 2022
Source:
University of Houston
Summary:
Engineers have discovered that they can actually move deep water
and create upward fountains by shining laser beams on the water's
surface.

The finding, credited to the Marangoni effect, has potential to
impact fluid dynamics in many applications.



FULL STORY ==========================================================================
A pair of University of Houston engineers has discovered that they can
create upward fountains in water by shining laser beams on the water's
surface. Jiming Bao, professor of electrical and computer engineering
at UH, and his postdoctoral student Feng Lin, attribute the finding to
a phenomenon known as the Marangoni effect, which causes convection and explains the behavior of water when differences in surface tension exist.


========================================================================== Though first described in the 1860's, the Marangoni effect is still
having its way with science.

"Scientifically no one has predicted or imagined this kind of upward deformation before," reports Bao in Materials Today Physics. "It is
well known that an outward Marangoni convection from a low surface
tension region will make the free surface of a liquid depressed. Here,
we report that this established perception is only valid for thin liquid
films. Using surface laser heating, we show that in deep liquids a laser
beam pulls up the fluid above the free surface generating fountains with different shapes." Here's a Marangoni visual: Sprinkle a bunch of pepper
into a bowl of water.

Then squeeze one drop of liquid detergent (dishwashing, laundry, even a
chip of soap or toothpaste) into the middle of the same bowl and watch as
the pepper disburses, scattering quickly to the sides of the bowl. That
simple experiment illustrates the Marangoni effect, which appears in
many applications of fluid dynamics.

In the most recent incarnation, the Marangoni effect's laser-induced
liquid fountains have potential to impact applications involving liquids
or soft matters such as lithography and 3D printing, heat transfer and
mass transport, crystal growth and alloy welding, dynamic grating and
spatial light modulation and microfluidics and adaptive optics.

Inspired by his previous work, the successful simulation of inward surface depression in a shallow liquid, Bao increased the depth of ferrofluid
in the current simulation. Ferrofluid is a so-called "magic" liquid and
is best known for its astonishing surface spikes generated by a magnet.

"Understanding the distinct surface deformation in liquids with different depths helps unravel the dynamics of the surface deformation process,"
said Bao.

Bao used a low-power (<1 W) continuous-wave laser beam to create a
non-uniform surface temperature field to induce the Marangoni effect. To understand the distinct deformations between deep and shallow liquids, he varied the liquid layer thickness while keeping the laser beam the same.

The laser fountains and the depth-dependent transition from surface
indentation to laser fountain have never been reported in literature,
probably because they are not anticipated by any existing theory.

"We emphasize that there have been numerous attempts to understand the Marangoni flow-driven surface deformation, but no existing theory can
predict the deformation patterns of a liquid with an arbitrary depth in
a straightforward manner," said Bao.

========================================================================== Story Source: Materials provided by University_of_Houston. Original
written by Laurie Fickman. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Feng Lin, Aamir Nasir Quraishy, Tian Tong, Runjia Li, Guang Yang,
Mohammadjavad Mohebinia, Yi Qiu, Talari Vishal, Junyi Zhao, Wei
Zhang, Hong Zhong, Hang Zhang, Zhongchen Chen, Chaofu Zhou, Xin
Tong, Peng Yu, Jonathan Hu, Suchuan Dong, Dong Liu, Zhiming Wang,
John R. Schaibley, Jiming Bao. Marangoni convection-driven laser
fountains on free surfaces of liquids. Materials Today Physics,
2021; 21: 100558 DOI: 10.1016/ j.mtphys.2021.100558 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220118184648.htm

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