While writing a physics report, I obtained a data that for balls of rough surfaces, there is a higher drag force and thus the ball can stay stable at a much smaller angle when put up in an airstream. However, while analyzing this result, I found out that the drag coefficient is not always bigger for rough spheres : it depends on the reynolds number of the flow. I would really like to know whether the flow past a sphere (in my experiment, styrofoam balls) is attached flow (Stokes flow) and steady separated flow, separated unsteady flow, separated unsteady flow with a laminar boundary layer at the upstream side, or post-critical separated flow, with a turbulent boundary layer. Put simply, what is the reynolds number of the air coming out of an air supply? For further information, the air supply used in our lab was SF-9216, PASCO.