Abstract
Simultaneous measurements of instantaneous axial velocity and concentration are performed in axisymmetric jet diffusion fields. The CO2 jets are issued into the nearly homogeneous and isotropic, freely decaying region of regular and fractal grid turbulence to investigate the influence of mainstream turbulence on the jet diffusion field. The composite probe consisting of two concentration-sensitive I-type hot-wire probes is used. For both flows, the mesh Reynolds number based on the grid mesh size and the mainstream velocity is 6,000 and the jet Reynolds number based on the nozzle diameter (3 mm) and the relative velocity between mainstream and jet exit velocity is 5,000. The results show that the growth of half widths of the mean velocity and mean concentration, axial turbulent mass flux, and eddy diffusivity are significantly increased under the influence of strong mainstream turbulence generated by the fractal grid.
