  We present an experimental study on the settling velocity of dense
sub-Kolmogorov particles in active-grid-generated turbulence in a wind tunnel.
Using phase Doppler interferometry, we observe that the modifications of the
settling velocity of inertial particles, under homogeneous isotropic turbulence
and dilute conditions $\phi_v\leq O(10)^{-5}$, is controlled by the
Taylor-based Reynolds number $Re_\lambda$ of the carrier flow. On the contrary,
we did not find a strong influence of the ratio between the fluid and gravity
accelerations (i.e., $\gamma\sim(\eta/\tau_\eta^2)/g$) on the particle settling
behavior. Remarkably, our results suggest that the hindering of the settling
velocity (i.e. the measured particle settling velocity is smaller than its
respective one in still fluid conditions) experienced by the particles
increases with the value of $Re_\lambda$, reversing settling enhancement found
under intermediate $Re_\lambda$ conditions. This observation applies to all
particle sizes investigated, and it is consistent with previous experimental
data in the literature. At the highest $Re_\lambda$ studied, $Re_\lambda>600$,
the particle enhancement regime ceases to exist. Our data also show that for
moderate Rouse numbers, the difference between the measured particle settling
velocity and its velocity in still fluid conditions scales linearly with Rouse,
when this difference is normalized by the carrier phase rms fluctuations, i.e.,
$(V_p-V_T)/u\sim -Ro$.
