Experimental Investigations of the Flow Uniformity and Jet Development on the Free Jet Calibration Wind Tunnel

Abstract

Results of experimental investigations of the flow uniformity and axisymmetric jet development on the free jet wind calibration tunnel are presented in this paper. At the outlet of calibration tunnel a profiled Witoshinsky nozzle is located, with outlet diameter of D = 145 mm. Flow uniformity measurement for 34 flow regimes was conducted, in the jet cross-section located at horizontal distance of x = 30 mm from the outlet of the nozzle. Velocity profile measurements were performed with Pitot probes. Based on the measurement results for the calibration tunnel, it can be concluded that flow is uniform to within ± 1 % across the test section with radius of 58-60 mm. In addition, development of the jet in the near-field region (0 < s/D < 4.828) is investigated by measurements of mean velocity profile in several streamwise cross-sections for four different regimes. Axisymmetric nature of the jet is proved. It was also shown that velocity profiles in the jet core are uniform, as well as that the jet geometry does not depend on the air flow velocity. This confirms calibration possibilities of this free jet calibration wind tunnel for velocity probes of various types.