Settling velocity of inertial particles in turbulent flows with different characteristics

Inertial particles are ubiquitous in both environmental and industrial flows. This study focuses on sub-Kolmogorov inertial particles advected in a turbulent air flow. Phase Doppler Particle Analyzer measurements of inertial droplets were taken in homogeneous isotropic turbulence with a wide range of Taylor microscale Reynolds numbers and integral length scales. The study explores a wide range of flow Reynolds number, Rouse number and volume fractions. Three types of isotropic and homogeneous turbulence were tested by means of a passive grid and an active grid used in two different configurations. The settling velocity of the inertial particles were also investigated in a turbulent/ non-turbulent interface. The use of different grid allows us to create turbulent flow with similar Reynolds number and turbulent intensity but significantly different integral length scale.

We find that the integral length scale has a strong influence on the settling velocity enhancement over the entire range of Stokes number studied.