Wind Tunnel: Flow Around a Cylinder
Objectives:
Investigate and report on the operation of a wind tunnel and flow around a cylinder
by determining the following information at the minimum and maximum flow
settings of the wind tunnel.
 Determine the velocity profile entering the wind tunnel’s test section.
 Measure and illustrate the velocity field downstream of a cylinder.
 Determine the drag force and drag coefficient of flow around a cylinder.
Background:
The CSUS subsonic wind tunnel is illustrated in Fig. 1. Air enters the tunnel through
the inlet section, passes through flow-straightening screens, and accelerates in the
contraction section. Downstream of the contraction is the test section, which is 0.30
m by 0.30 m and 0.50 m long. Downstream of the test section is the diffuser and
finally the blower. An adjustable gap between the diffuser and blower allows the user
to adjust the velocity in the test section. The fan speed and pressure in the blower is
constant, so the flow rate through the blower region is constant. However, the gap is
used to control the velocity of air in the test section.
A 1/8" diameter pitot-static tube is mounted on a vertical traverse mechanism and
oriented to measure the axial velocity. Although any kind of cylindrical object can be
mounted between the side walls, the current one is a circular cylinder, which has a
single static pressure port. The cylinder can be rotated through 360o, so that the
surface pressure can be measured at any angle relative to the mean flow direction.
Both the pitot-static tube and pressure port on the cylinder are located midway
between the two side walls.
Figure 1. Schematic Diagram of Subsonic Wind Tunnel
References:
http://gaia.ecs.csus.edu/~marbacht/windtunnelref.doc
White, F.M., Fluid Mechanics (or other fluids text).
Manometers on pages 26-29 of Cengel and Boles, Thermodynamics.