Turbulence Generation in Homogeneous Particle-Laden Flows

Abstract

The generation of turbulence by uniform e uxes of monodisperse spherical particles moving through a uniform e owing gas was studied experimentally. Phase velocities, moments, probability density functions,and energy spectra were measured within a countere owing particle/gas wind tunnel using phase-discriminating laser velocimetry. Test conditions includedparticle Reynolds numbersof 106‐990, particle volume fractions less than 0.003%, direct rates of dissipation of turbulence by particles less than 4%, and turbulence generation rates sufe cient to yield relative turbulence intensities in the range 0.2‐5.0%. Velocity records showed that the e ow consisted of randomly arrivingwake disturbanceswithinaturbulentinterwakeregionandthattheparticlewakepropertiescorresponded to recent observations of laminarlike turbulent wakes for spheres at intermediate Reynolds numbers in turbulent environments. Probabilitydensityfunctionsofvelocities were peaked forstreamwise velocities duetocontributions from mean streamwise velocities in particle wakes but were Gaussian for cross stream velocities that only involve contributions from the turbulence in the wakes. Relative intensities of streamwise and cross stream velocity euctuations were roughly correlated in terms of a dimensionless rate of turbulence dissipation factor. Finally, energy spectra exhibited prominent i 1 and i 5 power decay regions associated with contributions from mean velocities in particle wakes and particle and interwake turbulence, respectively.