Fluid Mechanics – 2
A 5.0-cm diameter sphere (density: 10 kg/m3) is suspended at a stationary state by a jet of air
exiting a pipe (only the end portion of the pipe is shown). The sphere’s drag coefficient is 𝐶𝐷 =
𝐹𝑑
0.5 (𝐶𝐷 = 1/2𝜌𝑈
; A: sphere’s projection area). Answer the following questions:
2𝐴
1. (70%) determine the reading of the pressure gage (friction and gravity can be neglected for the
flow between the pressure gage and the pipe exit; g=9.8 m/s2; volume of sphere with a
𝜋
diameter of D is given by 𝑉 = 6 𝐷3 .
2. (30%) sketch the pressure distribution on the sphere’s surface and a few streamlines near the
sphere. Identify the key features of your sketch and explain why these features are
qualitatively consistent with the drag coefficient given above.
Spring 2015