PIV measurement of near shear layer of a circular jet

Abstract

The shear layer (SL) of a turbulent jet is studied by using Particle Image Velocimetry (PIV) up to distance 0.2 nozzle diameters in axial × radial plane. The jet is generated by circular nozzle at Reynolds numbers 1.1·105 to 1.1·106. This range covers the transition from laminar instable SL to turbulent SL. The observed average velocity profiles are fitted by using Michalke function. This function describes both: the shear layer of tanh profile and the boundary layer formed inside the nozzle at the same time. In the second part of this contribution we show the fluctuations, their anisotropy and length-scale observing doubling in the wavelength at the transition.