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 where Roshko determined the correlation[1] below from experiments on the flow of air around circular cylinders over range Re=50 to 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.