Turbulence Generation in Homogeneous Particle-Laden Flows

The generation of turbulence by uniform uxes of monodisperse spherical particles moving through a uniform owing gas was studied experimentally. Phase velocities, moments, probability density functions, and energy spec-tra were measured within a counter owing particle/gas wind tunnel using phase-discriminating laser velocimetry. Test conditions included particle Reynolds numbers of 106–990, particle volume fractions less than 0.003%, direct rates of dissipation of turbulence by particles less than 4%, and turbulence generation rates suf cient to yield relative turbulence intensities in the range 0.2–5.0%. Velocity records showed that the ow consisted of randomly arriving wake disturbances within a turbulent interwake region and that the particle wake properties corresponded to recent observations of laminarlike turbulent wakes for spheres at intermediate Reynolds numbers in turbulent environments. Probability density functions of velocities were peaked for streamwise velocities due to contributions 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 uc-tuations were roughly correlated in terms of a dimensionless rate of turbulence dissipation factor. Finally, energy spectra exhibited prominent ¡ ¡ 1 and ¡ ¡ 53 power decay regions associated with contributions from mean velocities in particle wakes and particle and interwake turbulence, respectively. Nomenclature CD = sphere drag coef cient D = dissipation factor, e dp