Archimedes number

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Physical key figure
Surname Archimedes number
Formula symbol
dimension dimensionless
definition
Density difference between the body and the fluid
Acceleration due to gravity
characteristic length of the body
Density of the fluid
kinematic viscosity
Named after Archimedes
scope of application Buoyancy of bodies

The Archimedes number ( symbol :) is a dimensionless number , named after the ancient scholar Archimedes . It can be interpreted as the ratio of lift force to friction force and is defined as

.

The incoming sizes are

  • the difference between the density of the body and the density of the fluid
  • the acceleration of gravity , on earth
  • the volume calculated from the characteristic length of the body
  • the kinematic viscosity of the fluid , which differs from the dynamic viscosity by the factor .

Other definition

An alternative definition of the Archimedes number, which can be interpreted as the ratio of buoyancy force to inertia force or between free and forced convection , is identical to the definition of the Richardson number and reads:

.

It is

  • the isobaric expansion coefficient
  • the driving temperature difference
  • the ambient speed
  • : Grass yard number
  • : Reynolds number .

Individual evidence

  1. Repetition of technical thermodynamics : Achim Dittmann, Teubner study books, mechanical engineering ISBN 3-519-06354-9
  2. Hanel, Bernd M., Raumlufströmung, Müller Verlag Heidelberg, 1994 pp. 31 + 72
  3. VDI 6019 sheet 1, Beuth Verlag Berlin, 2006 p. 37 ff