Acceleration of inertial particles settling by gravity in homogeneous turbulence

The acceleration events of inertial particles in turbulence are of importance in a wealth of physical phenomena, e.g., for predicting the interaction and evolution of droplets in atmospheric clouds, which are responsible for large part of the uncertainty in weather forecast. Past experimental investigations have often considered neutrally buoyant particles, neglecting the role of gravity. Recent computational investigations have in fact shown that gravity can profoundly alter the acceleration statistics. However, these studies typically make use of simplifying assumptions such as the point-particle approximation and Stokes drag formulation. We perform Lagrangian Particle Tracking to investigate acceleration statistics of heavy particles in homogeneous turbulence with negligible mean flow and shear. This is generated by two planar jet arrays that produce a homogeneous region much larger than the integral scale, minimizing the influence of boundary conditions. The particles are dilute and smaller than the Kolmogorov scales. We consider different particle types and turbulence Reynolds numbers, which allows us to distinguish between the effects of inertia and gravity on the settling velocity, acceleration variance, and acceleration distributions.