Cylindrical coordinate system

A cylindrical coordinate system is a three-dimensional coordinate system that specifies point positions around a main axis (a chosen directed line) and an auxiliary axis (a reference ray). The three cylindrical coordinates are: the point perpendicular distance $ρ$ from the main axis; the point signed distance z along the main axis from a chosen origin; and the plane angle $φ$ of the point projection on a reference plane (passing through the origin and perpendicular to the main axis)

The main axis is variously called the cylindrical or longitudinal axis. The auxiliary axis is called the polar axis, which lies in the reference plane, starting at the origin, and pointing in the reference direction. Other directions perpendicular to the longitudinal axis are called radial lines.

The distance from the axis may be called the radial distance or radius, while the angular coordinate is sometimes referred to as the angular position or as the azimuth. The radius and the azimuth are together called the polar coordinates, as they correspond to a two-dimensional polar coordinate system in the plane through the point, parallel to the reference plane. The third coordinate may be called the height or altitude (if the reference plane is considered horizontal), longitudinal position,^[1] or axial position.^[2]

Cylindrical coordinates are useful in connection with objects and phenomena that have some rotational symmetry about the longitudinal axis, such as water flow in a straight pipe with round cross-section, heat distribution in a metal cylinder, electromagnetic fields produced by an electric current in a long, straight wire, accretion disks in astronomy, and so on.

They are sometimes called cylindrical polar coordinates^[3] or polar cylindrical coordinates,^[4] and are sometimes used to specify the position of stars in a galaxy (galactocentric cylindrical polar coordinates).^[5]

^ Krafft, C.; Volokitin, A. S. (1 January 2002). "Resonant electron beam interaction with several lower hybrid waves". Physics of Plasmas. 9 (6): 2786–2797. Bibcode:2002PhPl....9.2786K. doi:10.1063/1.1465420. ISSN 1089-7674. Archived from the original on 14 April 2013. Retrieved 9 February 2013. ...in cylindrical coordinates $(r, θ, z)$ ... and $Z = v bz t$ is the longitudinal position...
^ Groisman, Alexander; Steinberg, Victor (1997). "Solitary Vortex Pairs in Viscoelastic Couette Flow". Physical Review Letters. 78 (8): 1460–1463. arXiv:patt-sol/9610008. Bibcode:1997PhRvL..78.1460G. doi:10.1103/PhysRevLett.78.1460. S2CID 54814721. ...where $r$ , $θ$ , and $z$ are cylindrical coordinates ... as a function of axial position...
^ Szymanski, J. E. (1989). Basic Mathematics for Electronic Engineers: models and applications. Tutorial Guides in Electronic Engineering (no. 16). Taylor & Francis. p. 170. ISBN 978-0-278-00068-1.
^ Nunn, Robert H. (1989). Intermediate Fluid Mechanics. Taylor & Francis. p. 3. ISBN 978-0-89116-647-4.
^ Sparke, Linda Siobhan; Gallagher, John Sill (2007). Galaxies in the Universe: An Introduction (2nd ed.). Cambridge University Press. p. 37. ISBN 978-0-521-85593-8.

[1] Krafft, C.; Volokitin, A. S. (1 January 2002). "Resonant electron beam interaction with several lower hybrid waves". Physics of Plasmas. 9 (6): 2786–2797. Bibcode:2002PhPl....9.2786K. doi:10.1063/1.1465420. ISSN 1089-7674. Archived from the original on 14 April 2013. Retrieved 9 February 2013. ...in cylindrical coordinates $(r, θ, z)$ ... and $Z = v bz t$ is the longitudinal position...

[2] Groisman, Alexander; Steinberg, Victor (1997). "Solitary Vortex Pairs in Viscoelastic Couette Flow". Physical Review Letters. 78 (8): 1460–1463. arXiv:patt-sol/9610008. Bibcode:1997PhRvL..78.1460G. doi:10.1103/PhysRevLett.78.1460. S2CID 54814721. ...where $r$ , $θ$ , and $z$ are cylindrical coordinates ... as a function of axial position...

[3] Szymanski, J. E. (1989). Basic Mathematics for Electronic Engineers: models and applications. Tutorial Guides in Electronic Engineering (no. 16). Taylor & Francis. p. 170. ISBN 978-0-278-00068-1.

[4] Nunn, Robert H. (1989). Intermediate Fluid Mechanics. Taylor & Francis. p. 3. ISBN 978-0-89116-647-4.

[5] Sparke, Linda Siobhan; Gallagher, John Sill (2007). Galaxies in the Universe: An Introduction (2nd ed.). Cambridge University Press. p. 37. ISBN 978-0-521-85593-8.

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