Experimental Investigation of Airflow at Downstream of Multi Strand Cables

In a vertical wind tunnel، in order to prevent persons or an experimental model from falling، a protective screen should be installed at the end of the nozzle section. Since the air has the maximum velocity at this section، the pressure drop due to the protective screen will be significantly high. On the other hand، as the protective screen is alternatively exposed to dynamic forces due to free fall of the floating persons or the model، the screen wires will experience fatigue. To prevent this، multi strand cables should be used in the manufacturing of these protective screens. In this research work، using the momentum difference method، drag coefficient for the multi strand cables and circular rods has been measured and compared. For this purpose، a hot wire anemometer (HWA) with a one-dimensional probe has been used. Results show that at Reynolds number in proximity of 2 × 103، the drag coefficient for the multi strand cable exceeds that of a circular rod by 16% and that this amount decreases with further increase in Reynolds number. The trend is such that for Reynolds number of 104، the drag coefficients of the multi strand cable and circular rod are almost equal.