In
fluid dynamics
In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) an ...
, the Lamb–Oseen vortex models a line
vortex that decays due to
viscosity. This vortex is named after
Horace Lamb and
Carl Wilhelm Oseen
Carl Wilhelm Oseen (17 April 1879 in Lund – 7 November 1944 in Uppsala) was a theoretical physicist in Uppsala and Director of the Nobel Institute for Theoretical Physics in Stockholm.
Life
Oseen was born in Lund, and took a Fil. Kand. degre ...
.
Mathematical description
Oseen looked for a solution for the
Navier–Stokes equations in cylindrical coordinates
with velocity components
of the form
:
where
is the
circulation
Circulation may refer to:
Science and technology
* Atmospheric circulation, the large-scale movement of air
* Circulation (physics), the path integral of the fluid velocity around a closed curve in a fluid flow field
* Circulatory system, a bio ...
of the vortex core. Navier-Stokes equations lead to
:
which, subject to the conditions that it is regular at
and becomes unity as
, leads to
:
where
is the
kinematic viscosity of the fluid. At
, we have a potential vortex with concentrated
vorticity at the
axis; and this vorticity diffuses away as time passes.
The only non-zero vorticity component is in the
direction, given by
:
The
pressure field simply ensures the vortex rotates in the
circumferential direction, providing the
centripetal force
:
where ''ρ'' is the constant density
Generalized Oseen vortex
The generalized Oseen vortex may obtained by looking for solutions of the form
:
that leads to the equation
:
Self-similar solution
In the study of partial differential equations, particularly in fluid dynamics, a self-similar solution is a form of solution which is similar to itself if the independent and dependent variables are appropriately scaled. Self-similar solutions ap ...
exists for the coordinate
, provided
, where
is a constant, in which case
. The solution for
may be written according to Rott (1958)
[Rott, N. (1958). On the viscous core of a line vortex. Zeitschrift für angewandte Mathematik und Physik ZAMP, 9(5-6), 543–553.] as
:
where
is an arbitrary constant. For
, the classical Lamb–Oseen vortex is recovered. The case
corresponds to the axisymmetric
stagnation point flow, where
is a constant. When
,
, a
Burgers vortex is a obtained. For arbitrary
, the solution becomes
, where
is an arbitrary constant. As
,
Burgers vortex is recovered.
See also
* The
Rankine vortex
The Rankine vortex is a simple mathematical model of a vortex in a Viscosity, viscous fluid. It is named after its discoverer, William John Macquorn Rankine.
The vortices observed in nature are usually modelled with an Potential flow#Examples of ...
and
Kaufmann (Scully) vortex are common simplified approximations for a viscous vortex.
References
{{DEFAULTSORT:Lamb-Oseen vortex
Vortices
Equations of fluid dynamics