Distribution of separations and relative velocities of droplets in turbulence EuHIT Funded Project

Team

Gregory Bewley
Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany
Dag Hanstorp
University of Gothenburg, Gothenburg, Sweden
Postdoc Nn
University of Gothenburg, Gothenburg, Sweden

Overview

Research Infrastructure
Max Planck High-Turbulence Facility, Germany
Facilities used
von Karman Flow Apparatus (GTF3)
Project leader
Bernhard Mehlig
University of Gothenburg, Gothenburg, Sweden

Abstract

Turbulent mixing leads to collisions between particles carried by the flow. This process occurs in atmospheric clouds and causes microscopic water droplets to grow. Yet little is known about how turbulence causes collisions, and what their consequences are (fragmentation or coalescence). To answer these questions it is necessary to measure the distribution of relative velocities and separations of nearby droplets in turbulence, on scales on the order of and possibly even smaller than the Kolmogorov length, for as large droplets as possible. The GTF3 facility is unique in that allows us to observe the dynamics of droplets in turbulence at very small scales. Since the relative dynamics of two (or more) droplets depends sensitively on their sizes it is necessary to control the size as precisely as possible. To this end we will install a droplet dispenser based on the technology used in ink-jet printers. We will compare the experimentally determined distribution of separations and relative velocities between droplets with theoretical-model predictions and results of direct numerical simulations.