Water drop impact on a water-surface - (2)

fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics of fluids ( liquids, gases, and plasmas) and the forces on them. It has applications in a wide range of disciplines, including mechanical, aerospace, civil, chemical and ...

, a splash is a sudden disturbance to the otherwise quiescent free surface of a liquid (usually

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

). The disturbance is typically caused by a solid object suddenly hitting the surface, although splashes can occur in which moving liquid supplies the energy. This use of the word is

onomatopoeic Onomatopoeia is the process of creating a word that phonetically imitates, resembles, or suggests the sound that it describes. Such a word itself is also called an onomatopoeia. Common onomatopoeias include animal noises such as ''oink'', ''m ...

; in the past, the term "plash" has also been used. Splash also happens when a liquid

droplet A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces. A drop may form when liquid accumulates at the lower end of a tube or other surface boundary, producing a hanging drop called a pendant ...

impacts on a liquid or a solid surface; in this case, a symmetric ''corona'' (resembling a coronet) is usually formed as shown in

Harold Edgerton Harold Eugene "Doc" Edgerton (April 6, 1903 – January 4, 1990), also known as Papa Flash, was an American scientist and researcher, a professor of electrical engineering at the Massachusetts Institute of Technology. He is largely credited with ...

's famous milk splash photography, as

milk Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modulat ...

is opaque. Historically, Worthington (1908) was the first one who systematically investigated the splash dynamics using photographs. Splashes are characterized by transient ballistic flow, and are governed by the

Reynolds number In fluid mechanics, the Reynolds number () is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. At low Reynolds numbers, flows tend to be dom ...

and the

Weber number The Weber number (We) is a dimensionless number in fluid mechanics that is often useful in analysing fluid flows where there is an interface between two different fluids, especially for multiphase flows with strongly curved surfaces. It is named ...

. In the image of a brick splashing into water, one can identify freely moving airborne water droplets, a phenomenon typical of high Reynolds number flows; the intricate non-spherical shapes of the droplets show that the Weber number is high. Also seen are entrained air bubbles in the body of the water, and an expanding ring of disturbance propagating away from the impact site.

Sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class ...

is said to splash if hit sufficiently hard (see dry quicksand) and sometimes the impact of a

meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the original object ...

is referred to as splashing, if small bits of ejecta are formed. Physicist

Lei Xu Lei Xu, alternatively Lei Pu or Lei Bo, (died 209) was a military officer and rebel who was mainly active in the 200s in China. Initially loyal to warlord Yuan Shu, Lei Xu abandoned his master when the latter's regime collapsed, becoming an i ...

and coworkers at the

University of Chicago The University of Chicago (UChicago, Chicago, U of C, or UChi) is a private research university in Chicago, Illinois. Its main campus is located in Chicago's Hyde Park neighborhood. The University of Chicago is consistently ranked among the b ...

discovered that the splash due to the impact of a small drop of

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

onto a dry solid surface could be suppressed by reducing the pressure below a specific threshold. For drops of diameter 3.4 mm falling through air, this pressure was about 20 kilopascals, or 0.2

atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A ...

. A plate made of a hard material on which a stream of liquid is designed to fall is called a "splash plate". It may serve to protect the ground from

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is d ...

by falling water, such as beneath an

artificial waterfall An artificial waterfall is a water feature or fountain which imitates a natural waterfall. Artificial waterfalls have long been featured in traditional Japanese gardens, where they can serve to highlight a scene or to provide focus. The clas ...

or water outlet in soft ground. Splash plates are also part of spray nozzles, such as in irrigation sprinkler systems.

References

{{Reflist Fluid dynamics

See also

References