High-resolution particle image velocimetry (PIV) was used to study the flow characteristics in the nearfield of a turbulent round water jet issuing from a circular nozzle. Mean velocity, velocity gradient, turbulence intensity, Reynolds stress and other turbulence statistics are investigated over a range of jet Reynolds number Re (based on jet exit velocity and equivalent nozzle diameter) varying from 531 to 13500. The distribution of parameters of different Reynolds numbers and different height sections was studied. The velocity measurements reveal that all exit jet profiles in the near-field closely approximate a single peak shape, and they show strict self-similarity. Compare turbulence intensity, Reynolds stress with different Reynolds number jet, the self-similarity is shown along jet path when Reynolds number is low, and the self-similarity is shown after the turbulence is fully developed when Reynolds number is high. The shapes of Reynolds stress of high Reynolds number jet change from double peak to single peak along jet path, and the shapes are always single peak at low Reynolds numbers. This critical Reynolds number is about 2000. In addition, the turbulence statistics can be used to correct the coefficients of the turbulence equation and large eddy simulation.

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