  Particles suspended in turbulent flows are affected by the turbulence and at
the same time act back on the flow. The resulting coupling can give rise to
rich variability in their dynamics. Here we report experimental results from an
investigation of finite-sized buoyant spheres in turbulence. We find that even
a marginal reduction in the particle's density from that of the fluid can
result in strong modification of its dynamics. In contrast to classical spatial
filtering arguments and predictions of particle models, we find that the
particle acceleration variance increases with size. We trace this reversed
trend back to the growing contribution from wake-induced forces, unaccounted
for in current particle models in turbulence. Our findings highlight the need
for improved multi-physics based models that account for particle wake effects
for a faithful representation of buoyant-sphere dynamics in turbulence.
