Ricerc@Sapienza

Direct Numerical Simulations (DNS) of a bubbly laden homogeneous shear flow has beencarried out using the Exact Regularised Point Particle method (ERRP) as inter-phase mo-mentum coupling approach. The aim of the study consists in addressing the modulationof shear turbulence and the bubble clustering geometry in presence of different inter-phasemomentum coupling conditions. Suspensions with different combinations of void fractionand Kolmogorov-based Stokes number, in the dilute regime, have been addressed. Bubblessuppress the turbulent kinetic energy and turbulent dissipation as well. Turbulent modula-tion occurs via the direct change of the Reynolds shear stress. In fact, the bubble energysource is proved to be negligible in the scale-by-scale turbulent energy budget. The bubbleclustering, in agreement with the literature, occurs in the form of thin elongated structures.The clusters are aligned with principal strain direction of the mean flow, as usual in shearflows. The bubble clustering and turbulent modification are strictly related: both increasewith the Stokes number and are independent of the void fraction. The data show that theturbulent modification is disadvantaged when the bubble distribution is homogeneous (i.e.small Stokes number). Finally, the small scale bubble clustering is slightly reduced by two-way coupling effects even though the clustering anisotropy still persists at small scales asit occurs for inertial particles.