Consider \(20{ }^{\circ} \mathrm{C}\) water flowing over a thin, wide, smooth flat plate aligned with the flow. The approach velocity is \(60 \mathrm{~km} / \mathrm{hr}\) and the Reynolds number based on the plate length is \(2 \times 10^{5}\). Calculate the drag per unit width of the plate for each of the velocity profiles listed in Table 9.2. Next calculate the drag coefficient \(C_{D}\) as used in Fig. 9.15. Which velocity profile(s) provide the best estimation of \(C_{D}\) ? Why?

Fig. 9.15

Table 9.2

0.014 0.012 0.010 Turbulent 0.008 0.006 5 x 10 =3103 Completely turbulent 2 x 10-3 1 x 103 5x104 2 x 104 1 x 104 5 x 10-5 0.004 Transitional 2 x 10-5 5 x 10-6 0.002 1 x 10-6 Laminar- Turbulent smooth plate 0 105 106 107 108 109 Re