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In
fluid mechanics , the Roshko number (Ro ) is a
dimensionless number describing oscillating flow mechanisms. It is named after the American Professor of Aeronautics
Anatol Roshko . It is defined as
R
o
=
f
L
2
ν
=
S
t
R
e
{\displaystyle \mathrm {Ro} ={fL^{2} \over \nu }=\mathrm {St} \,\mathrm {Re} }
S
t
=
f
L
U
,
{\displaystyle \mathrm {St} ={fL \over U},}
R
e
=
U
L
ν
{\displaystyle \mathrm {Re} ={UL \over \nu }}
where
Correlations
Roshko determined the correlation
[1] below from experiments on the flow of air around circular cylinders over range Re=50 to Re=2000:
R
o
=
0.212
R
e
−
4.5
{\displaystyle \mathrm {Ro} =0.212\mathrm {Re} -4.5}
valid over [ 50 <= Re < 200]
R
o
=
0.212
R
e
−
2.7
{\displaystyle \mathrm {Ro} =0.212\mathrm {Re} -2.7}
valid over [200 <= Re < 2000]
Ormières and Provansal
[2] investigated vortex shedding in the wake of a sphere and found a relationship between Re and Ro in the range 280 < Re < 360.
Notes
^ Roshko (1952) Figures 9 and 10
^ Ormières and Provansal (1999), Figure 5
References