Experimental investigation into Lagrangian statistics of droplets in homogeneous isotropic turbulence

¹ New Cornerstone Science Laboratory, Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of MoE, Department of Energy and Power Engineering, Tsinghua University - 100084 Beijing, China
² Department of Applied Physics and Science Education, Eindhoven University of Technology - 5600 MB Eindhoven, The Netherlands
³ Department of Engineering Mechanics, School of Aerospace Engineering, Tsinghua University - 100084 Beijing, China

Received: 3 December 2025
Accepted: 4 February 2026

Abstract

We experimentally investigate the Lagrangian dynamics of finite-sized, neutrally buoyant droplets in homogeneous isotropic turbulence. The droplet size follows a log-normal distribution whose average value decreases with increasing Reynolds number, reflecting enhanced turbulent breakup. While size-conditioned velocity and acceleration statistics show only weak finite-size dependence, temporal measures reveal clear size-dependent dynamics: larger droplets exhibit longer Lagrangian velocity integral times and an extended ballistic regime in their mean squared displacement. These findings indicate that though droplets exhibit mild deformation and internal circulation, they behave similarly to finite-size rigid particles in terms of Lagrangian dynamics. Our study opens the way to study droplet-laden turbulence and droplet-flow interactions.