DOI: 10.1615/TSFP5
TURBULENCE MEASUREMENTS IN A QUASI-TWO DIMENSIONAL JET IN A SLOT CHANNEL
ABSTRACT
Turbulent structure of a jet spreading in a narrow channel is studied experimentally by using PIV. A wide range of the Reynolds number, defined on the basis of the mean flow rate velocity and a hydraulic diameter of rectangular nozzle, was covered (from 500 up to 50,000). External low-amplitude forcing of inlet velocity was performed to study the influence of large-scale vorticies developing in the jet shear layer on the flow structure. On the basis of the special measurements with a high spatial resolution the one-dimensional spatial spectra were calculated for initial and far regions of the jet. Two typical spectrum slopes were clearly observed: -3 slope in the low wave number region and -1 slope in the high wavenumber region.
Spatial distributions of the statistical moments of velocity fluctuations up to the third-order were obtained. It is demonstrated, that the forcing affects significantly the flows with low and moderate Re leading to greater values of the moments in the near-nozzle region of the jet.
For the case, corresponding to Re = 20,000, terms of the mean momentum and turbulent kinetic energy (TKE) budget equations were estimated for a far region of the jet. For the axial mean momentum, convection and mean pressure gradient mainly contribute to the balance equation, while for TKE the effect of the convection was found to be rather small.