TURBULENCE CHARACTERISTICS OF THE NOISE PRODUCING REGION OF AN EXCITED ROUND JET. PART 2. LARGE-SCALE STRUCTURE CHARACTERISTICS.

Experiments were conducted to determine large-scale turbulence characteristics of the noise-producing region of a 3 in. cold excited round jet. The jet was excited by plane acoustic waves with a very high amplitude of excitation (2% of the jet dynamic head), and at Strouhal number of 0. 5. The flow Reynolds number was 2. 8 multiplied by 10**5. The exit boundary layer was artificially tripped to a turbulent state with sandpaper strips. All the data were obtained with single and X-hot-wires and processed in digital form. Large-scale characteristics were determined through the examination of the hot-wire records. The method involved the ensemble-averaging of the records with a conditional criterion based on the frequency of excitation. The results showed a wave-like behavior of the velocity components through the mixing region.