Homogeneous turbulence generated by uniform fluxes of monodisperse spherical particles moving through a uniform flowing gas was studied. Measurements of phase velocities, moments, probability density functions, temporal power spectra and spatial integral scales were obtained using phase-discriminating laser velocimetry and particle sampling for counterflowing particle/air wind tunnel flows, to supplement earlier findings for particles falling in stagnant water and air. The combined data base involved particle Reynolds numbers of 38-780, particle volume fractions less than 0.01% and rms turbulent fluctuations due to turbulence generation in the range 0.1-10.0% of the mean velocity differences between the particles and the continuous phase. Instantaneous velocity records showed affects of particle wake disturbances in the streamwise direction but were more dominated by inter-wake turbulence in the crosstream direction; peaked probability density functions of streamwise velocities and near Gaussian probability density functions of crosstream velocities supported this behavior. The instantaneous velocity records also showed that particle wake properties corresponded to recent observations of laminar-like turbulent wakes for spheres at intermediate Reynolds numbers in turbulent environments. Streamwise velocity fluctuations were correlated reasonably well by assuming that particle wake properties dominated flow properties using a stochastic theory; in contrast, crosstream velocity fluctuations were mainly dominated by inter-wake turbulence due to the weak direct contribution of the particle wakes to the properties of this flow direction. The temporal power spectra of streamwise and crosstream velocity fluctuations exhibited prominent -1 and -5/3 power decay regions associated with contributions from mean velocities in the particle wakes and from particle-wake and inter-wake turbulence, respectively. Finally, streamwise and crosstream integral scales were crudely correlated as functions of the known dissipation rate of the turbulence kinetic energy of the flow.
|State||Published - 1 Jan 1998|
|Event||36th AIAA Aerospace Sciences Meeting and Exhibit, 1998 - Reno, United States|
Duration: 12 Jan 1998 → 15 Jan 1998
|Conference||36th AIAA Aerospace Sciences Meeting and Exhibit, 1998|
|Period||12/01/98 → 15/01/98|