抄録
An experimental investigation into a turbulent jet issuing from a round sharp-edged orifice plate into essentially unbounded surroundings is presented. The Reynolds number, based on the initial diameter and velocity of the jet, is 68,000. Particle Image Velocimetry (PIV) was applied for planar measurements of the instantaneous velocity field of the jet. Both the axial and radial components of the mean and RMS velocities were obtained. The mean velocity decay along the centreline and the jet half-velocity radius were derived from the mean data. Comparison of present and previous measurements suggests that high initial turbulence intensity lead to reduced decay and spread of the mean flow field in the orifice jet. Results also show that self-similarity of the mean flow is approximately established early in the transition region while no self-similar turbulence occurs even at 30 exit diameters downstream from the orifice plate.
