The 70-cm-diameter circular stop sign shown in Figure 3 is mounted on a 2.55-m-high cylindrical pole that has a diameter of 4 cm. Determine the drag force on the structure for a wind with velocity 22.4 m/s blowing normal to the stop sign. How does this force compare with the force exerted if the wind is blowing perpendicular to the stop sign. The ambient air temperature is 20C. 4 cm T STOP 0.70 m 2.55 m APPENDIX Table 10.4: Drag Coefficients of Two-Dimensional Bodies Shape Description Area CD Re R/D CD TDA R Square, LD rounded corners 0 0.02 2.0 0.17 1.2 0.33 2.2 105 1.0 701 iD VD VD Semicircular LD shell 2.3 104 0.3 (turbulent BL) > 2 x 106 Cylinder LD 1.2 (laminar BL) 103 to 2 x 105 B/D CD B 104 D 1.42 0.38 > 104 D 1.1 > 10 D L/D CD 0.5 1.1 1.0 0.93 > 105 2.0 0.83 4.0 0.85 L/D CD 0.75 0.2 1.0 0.2 > 106 2.0 0.1 4.0 0.1 8.0 0.1 w/h CD 1 1.18 5 1.2 wh 120 > 104 10 1.3 20 1.5 2.0 0 10 0.30 74 D 30 0.55 > 104 60 0.80 90 1.15 References: White (2011); Blevins (1984); Cengel and Cimbala (2014). B.1 Water Table B.1: Physical Properties of Water at Standard Sea-Level Pressure Temp Density Dynamic Heat of Saturation Surface Bulk Expansion (C) (kg/m) Viscosity Vaporization Vapor Pressure Tension Modulus Coefficient (kPa) (mN/m) (10 kPa) (10-3 K-1) (mPas) (MJ/kg) 30 40 60 1505222288} 999.8 1.781 2.499 0.611 75.6 2.02 -0.07 1000.0 1.518 2.487 0.872 74.9 2.06 0.160 999.7 1.307 2.476 1.227 74.2 2.10 0.088 999.1 1.139 2.464 1.704 73.5 2.14 0.151 998.2 1.002 2.452 2.337 72.8 2.18 0.207 997.0 0.890 2.440 3.167 72.0 2.22 0.257 995.7 0.798 2.428 4.243 71.2 2.25 0.303 992.2 0.653 2.405 7.378 69.6 2.28 0.385 988.0 0.547 2.381 12.340 67.9 2.29 0.457 983.2 0.466 2.356 19.926 66.2 2.28 0.523 70 977.8 0.404 2.332 31.169 64.4 2.25 0.585 80 971.8 0.354 2.307 47.367 62.6 2.20 0.643 90 965.3 0.315 2.282 70.113 60.8 2.14 0.665 100 958.4 0.282 2.256 101.325 58.9 2.07 0.752 The properties given in Table B.1 are for pure water. Pure water seldom exists in nature, where the density of water can be influenced significantly by salinity, temperature, and other properties through an equation of state. The general dependence of water density on temperature has been found to be approximately parabolic, with a maximum at 4C. However, the temperature corresponding to the maximum density of water changes with increasing salinity, decreasing to about 0C for highly saline systems. To a first-order approximation, density is linearly dependent on salinity over much of the normal range of interest. Note: a. The kinematic viscosity, v, of water at 20C is approximately equal to 1.004 10-6 m/s.