Interwake turbulence properties of homogeneous dilute particle-laden flows

The properties of turbulence generated by uniform fluxes of monodisperse sp herical particles moving through a uniform flowing gas were studied experim entally, emphasizing the properties of the region surrounding individual wa ke disturbances, i.e., the turbulent interwake region. Mean and fluctuating values, probability density functions, and energy spectra of streamwise an d cross-stream velocities were measured within a counterflowing particle/ai r wind tunnel using particle wake discriminating laser velocimetry. Test co nditions included nearly monodisperse glass spheres having diameters of 0.5 -2.2 mm, particle Reynolds numbers of 106-990, mean particle spacings of 13 -208 mm, particle volume fractions less than 0.003%, direct rates of dissip ation of turbulence by particles less than 4%, and turbulence generation ra tes sufficient to yield streamwise relative turbulence intensities in the r ange 0.2-1.5%. The turbulent interwake region was homogeneous and nearly is otropic with probability density functions that are well approximated by Ga ussian functions. Relative turbulence intensities were correlated effective ly based on an analogy to the properties of isotropic grid-generated turbul ence by scaling with the mean particle spacing normalized by the particle w ake momentum diameter. For present turbulence generation conditions the tur bulent interwake region had turbulence Reynolds numbers of 0.4-3.5 and was in the final decay period where vortical regions fill the turbulent interwa ke region but are sparse. This implies enhanced rates of dissipation of tur bulent kinetic energy and decreasing macroscale/microscale ratios of the tu rbulence with increasing Reynolds numbers, as opposed to increasing ratios with increasing Reynolds numbers typical of conventional fully developed is otropic turbulence.