Modulation of fluid temperature fluctuations by inertial particles in turbulence

We investigate the effect of the thermal two-way coupling between the fluid temperature field and point-like particles on the temperature statistics in homogeneous and isotropic steady turbulence by means of direct numerical simulations (DNS). Results show that, on average, particles dissipate the variance of the temperature fluctuations modulating the fluid temperature gradients. The temperature gradient normalized Probability Density Functions (PDF) collapse to a single curve for all Stokes and thermal Stokes numbers. On the other hand, the normalized PDF of the fluid temperature-particle temperature increments, which cause the thermal dissipation, shows a strong dependence on the thermal Stokes number. Inertial particles preferentially cluster in the region of sharp fluid temperature variation and easily cross these thin temperature gradient sheets causing large heat fluxes. The impact of the particle thermal feedback across the scales of the flow is examined through the fluid temperature and particle temperature Eulerian structure functions