Measuring Turbulent Flows

1. Measure the width of the slit, W, and record this value in table 1.
2. Set the hot-wire anemometer at a distance from the exit equal to x = 1.5W along the centerline. Record this streamwise position in table 2. The centerline is the origin of the spanwise coordinate (y = 0).
3. Start the data acquisition program for traversing the jet. Set the sample rate at 500 Hz for a total of 5000 samples (i.e. 10s of data).
4. Record the current spanwise position of the hot-wire in table 3.
5. Acquire data.
6. The data acquisition system will calculate the average velocity and turbulence intensity of that dataset using equations (1) and (4).
7. Record those two values in table 3.
8. Move the hotwire to the next (positive) spanwise position ( mm).
9. Repeat steps 5 to 8 until there is not any noticeable change on both the average velocity and the turbulence intensity.
10. Move the hot-wire back to the centerline.
11. Move the hotwire to the next (negative) spanwise position ( mm).
12. Acquire data.
13. The data acquisition system will calculate the average velocity and turbulence intensity of that dataset using equations (1) and (4).
14. Record those two values in table 3.
15. Repeat steps 11 to 14 until there is not any noticeable change on both the average velocity and the turbulence intensity.
16. Move the hot-wire back to the centerline of the jet.
17. Move the hot-wire along the centerline of the jet in the downstream direction to a new position (e.g. x = 3W).
18. Repeat steps 4 to 17 for as many streamwise positions as wanted (e.g. x = 1.5W, 3W, 6W, 9W).

Table 1 . Basic parameters for experimental study.

Parameter	Value
Slit width (W)	19.05 mm
Air density (r)	1.2 kg/m3
Transducer calibration constant (m_p)	76.75 Pa/V
Calibration constant A	5.40369 V2
Calibration constant B	2.30234 V2(m/s)-0.65

Figure 4. Flow control in the flow system. The stack on top of the plenum serves the purpose of diverting flow from the jet slit allowing to control the jet ' s exit velocity. Please click here to view a larger version of this figure.