PIV investigations on optical magnification and small-scales in the near field of an orifice jet

Among turbulent jets, the orifice jet is still far from being fully understood especially due to the phenomenon of “vena contracta”, which takes place in the near field. In this work, the attention is focused to large-scale statistics (mean field and higher statistical moments of the velocity) and to small-scale statistics (velocity derivative statistical moments) of such a jet, with a special focus onto the effect of optical magnification on particle image velocimetry measurements. In order to investigate this effect on the measurements, framed areas of different size have been considered by changing the magnification factor through the object plane distance. The obtained results show that a limit on the choice of this parameter exists for a proper description of both small and large scales.