They have observed precisely what happens using a super-fast camera and have made a computer simulation of the process. This shows how the jet is forced upwards, layer by layer, by the surrounding water pressure. The simulation corresponds very closely with observations.
They have also formulated a theoretical model based on this that explains the extremely high speed of the water jet. The researchers are publishing their findings in the renowned journal, Physical Review Letters. These results are not only of academic significance as jets on the impact of an object on a liquid are frequent occurrences in nature and industry.
If one drops a stone into a pond, a very rapid, thin jet of water spouts upwards. This is an everyday phenomenon that occurs frequently in nature and industry. However, the rich and complex dynamics underlying such a system are only revealed if viewed using a high-speed camera. The latter shows how the downward movement of the object is converted into the upward movement of the jet.
A cavity forms behind the object during impact on the water surface. This cavity is subsequently compressed by hydrostatic pressure, which leads to the formation of the jet. In their experiments, FOM PhD candidate Stephan Gekle, José Manuel Gordillo of the University of Seville and Devaraj van der Meer and Detlef Lohse of the University of Twente demonstrate how the wall of the cavity forces the jet upward as it implodes, just like toothpaste being squeezed out of a tube, but many times faster, of course. Incidentally, a jet which is forced downward, deeper into the liquid, is also created at the same time. This second jet is not visible on the surface.
In order to examine the dynamics of the impact in a highly controlled manner, the researchers draw a circular disc through the water surface using a linear motor with a constant speed. Subsequently a high-speed camera is used to take images with a speed of up to 30,000 frames per second.
The formation and constriction of the cavity and the formation of the jet can thus be followed in detail. A computer simulation of the process – which corresponds very closely to the experiment – enables the researchers to study the resulting flow profile. It appears that the jet is forced upward, layer by layer, by the imploding wall. The researchers have formulated a theoretical model to explain the enormous speed of the water jet on the basis of this observation.
Wiebe van der Veen | alfa
Further information:
http://www.utwente.nl/en
Further reports about: > Twente > cavity forces > computer simulation > super-fast camera > surrounding water pressure > water jet > water surface
JILA researchers make coldest quantum gas of molecules
22.02.2019 | National Institute of Standards and Technology (NIST)
(Re)solving the jet/cocoon riddle of a gravitational wave event
22.02.2019 | Max-Planck-Institut für Radioastronomie
An international research team including astronomers from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has combined radio telescopes from five continents to prove the existence of a narrow stream of material, a so-called jet, emerging from the only gravitational wave event involving two neutron stars observed so far. With its high sensitivity and excellent performance, the 100-m radio telescope in Effelsberg played an important role in the observations.
In August 2017, two neutron stars were observed colliding, producing gravitational waves that were detected by the American LIGO and European Virgo detectors....
Up to now, OLEDs have been used exclusively as a novel lighting technology for use in luminaires and lamps. However, flexible organic technology can offer much more: as an active lighting surface, it can be combined with a wide variety of materials, not just to modify but to revolutionize the functionality and design of countless existing products. To exemplify this, the Fraunhofer FEP together with the company EMDE development of light GmbH will be presenting hybrid flexible OLEDs integrated into textile designs within the EU-funded project PI-SCALE for the first time at LOPEC (March 19-21, 2019 in Munich, Germany) as examples of some of the many possible applications.
The Fraunhofer FEP, a provider of research and development services in the field of organic electronics, has long been involved in the development of...
For the first time, an international team of scientists based in Regensburg, Germany, has recorded the orbitals of single molecules in different charge states in a novel type of microscopy. The research findings are published under the title “Mapping orbital changes upon electron transfer with tunneling microscopy on insulators” in the prestigious journal “Nature”.
The building blocks of matter surrounding us are atoms and molecules. The properties of that matter, however, are often not set by these building blocks...
Scientists at the University of Konstanz identify fierce competition between the human immune system and bacterial pathogens
Cell biologists from the University of Konstanz shed light on a recent evolutionary process in the human immune system and publish their findings in the...
Laser physicists have taken snapshots of carbon molecules C₆₀ showing how they transform in intense infrared light
When carbon molecules C₆₀ are exposed to an intense infrared light, they change their ball-like structure to a more elongated version. This has now been...
Anzeige
Anzeige
Global Legal Hackathon at HAW Hamburg
11.02.2019 | Event News
The world of quantum chemistry meets in Heidelberg
30.01.2019 | Event News
16.01.2019 | Event News
JILA researchers make coldest quantum gas of molecules
22.02.2019 | Physics and Astronomy
Understanding high efficiency of deep ultraviolet LEDs
22.02.2019 | Materials Sciences
Russian scientists show changes in the erythrocyte nanostructure under stress
22.02.2019 | Life Sciences