4.

A new design of telecommunications tower is modelled as a 5m diameter

perfectly smooth sphere on top of a vertical perfectly smooth cylinder, 30m high

and 2m diameter. It has to withstand an aerodynamic force imposed by a 100

km/h wind. For air take the density to be 1.20 kg/m³ and the kinematic viscosity

to be 1.5 x 10-5 m²/s.

a) Estimate at 100km/h the aerodynamic drag force acting on the sphere.

[7 marks]

b) Estimate at 100km/h the aerodynamic drag force acting on the cylinder.

[7 marks]

c) Estimate the bending moment at the base of the tower.

[5 marks]

d) Discuss why these results should only be regarded as an estimate of the

influence of drag on the real tower.

[6 marks]

Ref: ME20214G74-2