Entrainment at multi-scales across the turbulent/non-turbulent interface in an axisymmetric jet

Abstract

We consider the scaling of the mass flux and entrainment velocity across the turbulent/non-turbulent interface (TNTI) in the far field of an axisymmetric jet at high Reynolds number. Time-resolved, simultaneous multi-scale particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) are used to identify and track the TNTI, and directly measure the local entrainment velocity along it. Application of box-counting and spatial-filtering methods, with filter sizes spanning over two decades in length, show that the mean length of the TNTI exhibits a power-law behaviour with a fractal dimension . More importantly, we invoke a multi-scale methodology to confirm that the mean mass fl..