In physics, a fluid is a substance that continually deforms (flows) under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids. Fluids can be defined as substances that have zero shear modulus or in simpler terms a fluid is a substance which cannot resist any shear force applied to it.

Although the term "fluid" includes both the liquid and gas phases, in common usage, "fluid" is often used as a synonym for "liquid", with no implication that gas could also be present. For example, "brake fluid" is hydraulic oil and will not perform its required incompressible function if there is gas in it. This colloquial usage of the term is also common in medicine and in nutrition ("take plenty of fluids").

Liquids form a free surface (that is, a surface not created by the container) while gases do not. The distinction between solids and fluid is not entirely obvious. The distinction is made by evaluating the viscosity of the substance. Silly Putty can be considered to behave like a solid or a fluid, depending on the time period over which it is observed. It is best described as a viscoelastic fluid. There are many examples of substances proving difficult to classify. A particularly interesting one is pitch, as demonstrated in the pitch drop experiment currently running at the University of Queensland.

A fluid is defined as a substance that continually deforms (flows) under an applied shear stress.

Fluid may also refer to:

See also

Rushes is a 1998 ambient techno album by The Fireman, a duo consisting of Paul McCartney and producer Youth.

Recording

One line of lyrics included in the song "Palo Verde" was taken from an unreleased track of McCartney's, titled "Let Me Love You Always". Similarly, bits from another unreleased song, "Hey Now (What Are You Looking at Me For?)", was used in "Bison", "Auraveda" and "7 a.m.". Both unreleased tracks were recorded at some point during 1995, at McCartney's The Mill studio. In an edition of Club Sandwich magazine, two more songs were mentioned: "Plum Jam" and "Through the Marshes". All of the tracks featured on the album were recorded early 1998.

Release and reception

Better received than predecessor Strawberries Oceans Ships Forest, Rushes is distinguished by not relying so much on McCartney's previous recordings.

Rushes was released in the UK on Hydra on 21 September 1998, while in the US it was released on Capitol on 20 October 1998. The album was also released on double vinyl. Two 12" singles were released from the album, both mixes of "Fluid". The first 12", released on the same day as and with the same name as the album, contains the tracks "Fluid", "Appletree Cinnabar Amber", and an extended version of an album track titled "Bison (Long One)". The second 12" was released in 1999, as a limited edition of 3000, titled Fluid (Nitin Sawhney Remixes), and features three remixes of "Fluid" ("Fluid (Out of Body and Mind Mix)", "Fluid (Out of Body Mix)" and "Fluid (Out of Body with Sitar Mix)") and the album version of "Bison". Like the duo's first album,Rushes was a no-show on the charts and is also no longer in print.