Modulation of turbulence by stationary multiple-particle

Modulation of turbulent flow in an oscillating grid system due to the presence of stationary multiple particles was experimentally investigated using particle image velocimetry (PIV) technique wherein flow field modulation was reported in particle resolved manner. The particle diameter varied in the range ~ 3 to 7 mm (~ 30 to 68 times the single-phase Kolmogorov scale). The PIV velocity fields were obtained at grid Reynolds numbers (Re_g) ranging from 1080 to 10800. The single-phase turbulence fluctuating velocity increased in the inertial subrange region due to the presence of particles. Presence of particles led to enhancement in the flow field isotropy ratio which is completely opposite compared to the results of stationary single-particle case reported in Hoque et al. (2016). The energy spectra exhibited a slope less steep than −5/3 in the presence of particles which indicates the additional turbulence production by the particles in the inertial subrange region. Energy augmentation from large scale to small scale due to particles were discussed by the dissipative spectrum which showed that a reduction of the energy on the small scale and an enhancement of the energy on both large scale and inertial subrange.