In
fluid dynamics
In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids – liquids and gases. It has several subdisciplines, including (the study of air and other gases in motion ...
, the reyn is a British unit of
dynamic viscosity
Viscosity is a measure of a fluid's rate-dependent resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for example, syrup h ...
,
named in honour of
Osbourne Reynolds, for whom the
Reynolds number
In fluid dynamics, the Reynolds number () is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between Inertia, inertial and viscous forces. At low Reynolds numbers, flows tend to ...
is also named.
[Juvinal, Robert C. & Marshek, Kurt M.; ''Fundamentals of machine component design''. 2nd ed., 1991, pp. 480, ]
Conversions
By definition,
:1 reyn = 1 lb
f s in
−2.
It follows that the relation between the reyn and the
poise is approximately
:1 reyn = 6.89476 × 10
4 P.
In
SI units, viscosity is expressed in newton-seconds per square meter, or equivalently in
pascal-seconds. The conversion factor between the two is approximately
:1 reyn = 6890 Pa s.
References
External links
ReynHistory of the unit
Fluid dynamics
Units of dynamic viscosity
{{Fluiddynamics-stub