Fluid
As fluid (from latin fluidus , flowing ' ) are substances which under the influence of shear forces continuously deform , i.e., they flow . The shear modulus of ideal fluids is zero.
In physics, gases and liquids are summarized under the term . Many physical laws apply equally to gases and liquids, because these substances differ in some properties quantitatively (in the order of magnitude of the effect) instead of qualitatively.
The fluid mechanics means any substance as the fluid that a sufficiently slow shear no resistance opposes (finite viscosity ). In this sense, the term includes not only matter in the liquid and gaseous state of aggregation but also plasma , suspensions and aerosols .
Real fluids are divided into
- Newtonian fluids : they can be described by the Navier-Stokes equations ;
- Non-Newtonian fluids : their behavior is more complex and is treated in rheology .
Due to their surface tension , liquids form a free surface . This is not the case with gases.
Viscoelastic materials are a special case of liquids that, under certain circumstances, behave like an elastic solid .
Web links
Individual evidence
- ↑ Fluid. In: Lexicon of Physics. Spektrum Akademischer Verlag, accessed on May 4, 2014 .
- ↑ Guillermo Hauke: An Introduction to Fluid Mechanics and Transport Phenomena . Springer, 2008, ISBN 1-4020-8537-0 , pp. 7 (English, limited preview in Google Book Search).