Transcript What is the Reynolds number?

Looking at the microworld with
the naked eye
Can the slow motion of something very tiny be similar
to a quicker motion of something considerably larger?
Maciej Lisicki
Maria Ekiel - Jeżewska
What does it mean 'similar'?
Identical shape is not enough...
http://www.tukan-webdesign.de/krusenstern2/Krusens%20neu%20als%20Taste%20m.Schatt400x383.jpg
http://www.mmszczecin.pl/8307/2007/9/20/klub-czytelnika-zaprasza?category=interwencje
Reynolds number
UL
Re

 ,
U
L
L
ρ, μ
Density and viscosity of the liquid
Flow velocity
Characteristic size
U
Flow similarity principle
Two flows having the same Reynolds
numbers have the same character.
UL
Re

Low viscosity,
little size,
low velocities
=
High viscosity,
big size,
high velocity
Low viscosity + little objects
Welcome to the microworld!
Rhodobacter
BACTERIA IN WATER
Howard Berg’s Laboratory
E. coli
High viscosity + large objects
MACROWORLD
MICROWORLD
Re
Flows with similar Reynolds numbers
are similar!
Instead of looking at swimming
microobjects, we can observe large
bodies but in a Very Viscous Liquid!