Image: Drag coefficient on a sphere vs. Reynolds number - main trends

Description: Drag coefficient Cd for a sphere as a function of Reynolds number Re, as obtained from laboratory experiments. The dark line is for a sphere with a smooth surface, while the lighter-colored line is for the case of a rough surface. The numbers along the line indicate several flow regimes and associated changes in the drag coefficient: 2: attached flow (Stokes flow) and steady separated flow, 3: separated unsteady flow, having a laminar boundary layer upstream of the separation, and producing a vortex street, 4: separated unsteady flow with a laminar boundary layer at upstream side, before flow separation, with downstream of the sphere a chaotic turbulent wake, 5: super-critical separated flow, with a turbulent boundary layer.
Title: Drag coefficient on a sphere vs. Reynolds number - main trends
Credit: Original on NASA GRC Website imported as File:Dragsphere nasa.jpg Vectorized version at File:Drag sphere nasa.svg, further edited here with source data from File:CX SPHERE.png
Author: Original: Anonymous NASA author (editor: Nancy Hall) Vectorization by User:Kraaiennest Edits by Olivier Cleynen
Usage Terms: Public domain
License: Public domain
Attribution Required?: No