Preferential concentration of cloud-like droplets at various TKE dissipation rates EuHIT Funded Project


Anna Górska
University of Warsaw, Warsaw, Poland
Katarzyna Karpińska
University of Warsaw, Warsaw, Poland
Wojciech Kumala
University of Warsaw, Warsaw, Poland
Maciej Marek Mielczarek
University of Warsaw, Warsaw, Poland
Jakub Nowak
University of Warsaw, Warsaw, Poland


Research Infrastructure
Barrel of Ilmenau, Germany
Facilities used
Barrel of Ilmenau (BOI)
Project leader
Szymon Piotr Malinowski
University of Warsaw, Warsaw, Poland


The goal of the project is to experimentally characterize spatial distributions of droplets in conditions close to those existing in natural clouds. There is ambiguity concerning importance of droplet clustering in nature: numerical simulations in synthetic turbulence indicate existence of preferential concentration, while in-situ measurements from the aircraft do not confirm these results (see review by Devenish et al., 2012). Laboratory measurements of this effect in the range of parameters characteristic for cloud interior (see Vaillancourt and Yau, 2000) are not documented. We plan to reproduce a stationary, thermally-driven turbulence of TKE dissipation rate in the range characteristic for cloud interior inside the measurement volume of the Barrel of Ilmenau. We will use non-evaporating oil droplets of known diameter range as analogs of cloud droplets. Droplet diameters and number densities (and consequently the mass loading) will be similar to those in natural clouds. Non-evaporating oil allows to neglect condensation/evaporation effects in thermally driven turbulence, which in case of water droplets would be different than those in natural clouds. We will perform high-resolution laser sheet photography in a narrow sheet of light to characterize droplet spatial distribution in 2-D plane. We will use particle-imaging velocimetry in a wider sheet of light to characterize droplet motion and turbulence in the course of measurements.