Cross Cylindrical Flow: Measuring Pressure Distribution and Estimating Drag Coefficients

1. Measuring the pressure distribution around a cylinder

1. Remove the top cover of the test section of a wind tunnel, and mount a clean, aluminum cylinder (d = 4 in) with 24 built-in ports on a turntable (Figure 3). Install the cylinder so that port zero is facing upstream (Figure 4a).
2. Replace the top cover, and connect the 24 pressure tubes labeled 0 - 23 to the corresponding ports on the manometer panel. The manometer panel should be filled with colored oil but marked in water in. graduations (Figure 5).
3. Turn on the wind tunnel and run it at 60 mph. Record all 24 pressure measurements by reading the manometer. At this airspeed, the Reynolds number is 1.78 x 10⁵. The expected flow pattern is shown in Figure 2d.
4. Once all measurements have been recorded, turn off the wind tunnel and tape two strings (d = 1 mm) vertically on the cylinder to create the disturbed cylinder. Tape one string between ports 3 and 4 (θ = 52.5°) and the other between ports 20 and 21 (θ = 307.5°). Make sure the ports nearby are not blocked by the tape, as shown in Figure 4b.
5. Turn on the wind tunnel, and repeat step 3. Record all pressure measurements.

Figure 3. Gage pressure measurement layout of cross cylindrical flow.

Figure 4. Setup of the cylinder in the wind tunnel (pressure ports are in the middle of the cylinder).

Figure 5. Manometer panel.