Periodic Wake behind a Circular Cylinder

The features of periodic wakes behind a circular cylinder in the range of 40 ) is obtained as follows: λ^ = 3.25 + 220/R, 40 (R) and the Roshko's formula for S (R), that the critical Reynolds number at which the vortex streets begin to form is about 64 and that the vortex streets do not develop in the range of the Reynolds number lower than this critical value