# Curl

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## curl

*Maths*a vector quantity associated with a vector field that is the vector product of the operator ∇ and a vector function

**, where ∇ =**

*A***∂/∂**

*i**x*+

**∂/∂b**

*j**y*+

**∂/∂**

*k**z,*,

*i***, and**

*j***being unit vectors. Usually written curl**

*k***, rot**

*A*

*A*## Curl

of a vector field A, the vector characteristic of a “rotating component” of field A. The curl is represented by the symbol rot A. It can be interpreted in the following manner: Let A be the velocity field of a fluid flow. At a given point of the flow we place a small wheel with blades and orient its axis in the direction of rot A at that point. Then the angular velocity of the wheel’s rotation from the action of the current will be maximum, and its value will equal (| rot A |)/2. If the field A has the coordinates *P(x*, y, *z), Q(x, y, z*), and *R(x, y, z)*, then the curl has the coordinates

E. G. POZNIAK

## curl

[kərl] (forestry)

A block of timber cut from a crotch for cutting into veneers.

(materials)

A defect of paper caused by unequal alteration in the dimensions of the top and underside of the sheet.

(mathematics)

The curl of a vector function is a vector which is formally the cross product of the del operator and the vector. Also known as rotation (rot).

## curl

A winding, swirling, or circling in the grain of wood, usually obtained from the crotch or fork of a tree; also see

**fiddleback**.## Curl

**(1)**A programming environment for developing rich Internet applications (RIAs) from Curl, Inc., Cambridge, MA (www.curl.com). Conceived at MIT, Curl combines HTML markup with an object-oriented programming language. The user's machine requires the Curl runtime engine and browser plug-in for execution. The first Curl implementation was released in 2002. See RIA.

**(2)**(cURL) A command line utility for executing functions with URL-oriented protocols such as FTP and HTTP. Pronounced "

**C**-URL," there are versions for Unix, Linux, Windows, Mac and other operating systems. For more information, visit http://curl.haxx.se.