Golfball dimples cause the drag drop (see Figure 12.4 and the illustration for Problem 12.7) to occur

Golfball €œdimples€ cause the drag drop (see Figure 12.4 and the illustration for Problem 12.7) to occur at a lower Reynolds number. The table below gives the drag coefficient for a rough sphere as a function of the Reynolds number. Plot the drag for a 1.65-in.-diameter sphere as a function of velocity. Show several comparison points for a smooth sphere.

Figure 12.4

Data From Problem 12.7

The drag coefficient for a smooth sphere is shown below. Determine the speed at the critical Reynolds number for a 42-mm-diameter sphere in air.

Transcribed Image Text:

Re · 10¬4 7.5 10 15 20 25 0.22 Cp 0.48 0.38 0.12 0.10 200 100 OD Spheres 50 | }D Infinite plates 20 Circular disk and square plates 10 Sphere Strokes drag Cn= 24/Re CD Infinite plates 0.5 0.2 Circular disks and square plates 0.1 0.05 0.02 0.1 0.2 0.5 1 2 5 10 20 50 200 1000 10,000 100,000 1,000,000 Reynolds number = pvDlu 2.