Measurement of turbulence in an annular jet

An experimental investigation was conducted for an annular jet which consisted of a circular jet and a concentric wake. The annular air jet mixed with quiescent atmospheric air. The jet velocity was kept constant at 137.0 feet per second which corresponds to a Reynolds Number of 73,200. Using the technique of hot-wire anemometry, mean velocities, turbulence intensities and Reynolds stresses were measured in the longitudinal and lateral directions. Two distinct flow regimes, the free stream jet regime and the diffusing jet regime, are observed. In the free stream jet regime, higher turbulence intensity and shear stress occur in the inner region where the annular jet interacts with the wake. In the diffusing jet regime, higher turbulence intensity and higher turbulent shear occur in the outer mixing region where the annular jet interacts with the quiescent air. In both regimes, high turbulence intensities and Reynolds stresses correspond to high velocity gradients. The axial component of turbulence is approximately twice as large as the turbulence components in the lateral directions. The wake turbulence dissipates rapidly, whereas the turbulence caused by the jet mixing is preserved to a large extent --Abstract, page ii