Particle-Generated Isotropic Turbulence in the Final-Decay Period

Isotropic turbulence generated by uniform fluxes of mono- and poly-disperse particle moving through gases was studied theoretically and experimentally. Measurements involved mean and rms fluctuating velocities, velocity PDF's, energy spectra, and integral and Taylor length scales. Particle-generated turbulence proved to be isotropic turbulence in the final-decay period that had several unusual features compared to conventional isotropic turbulence in the initial-decay period: rates of dissipation of turbulence kinetic energy were enhanced, ratios of integral/Taylor length scales were unusually large, and ratios of integral/Taylor length scales decreased with increasing turbulence Reynolds number, which is just opposite to conventional isotropic turbulence in the initial-decay period. Finally, the properties of the energy spectra of isotropic turbulence in the final-decay period yielded an effective correlation between the rates of turbulence production by the stirring action of the dispersed particles and the relative turbulence intensities of the particle-generated turbulence.