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Experimental determination of droplet collision rates in turbulence

Bordás, Róbert and Roloff, Christoph and Thévenin, Dominique and Shaw, R. A. (2013) Experimental determination of droplet collision rates in turbulence. New Journal of Physics, 15 (4), pp. 1-31. Institute of Physics (IOP) Publishing. doi: 10.1088/1367-2630/15/4/045010. ISSN 1367-2630.

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Official URL: http://iopscience.iop.org/1367-2630/15/4/045010/pdf/1367-2630_15_4_045010.pdf


Inter-particle collisions in turbulent flows are of central importance for many engineering applications and environmental processes. For instance, collision and coalescence is the mechanism for warm rain initiation in cumulus clouds, a still poorly understood issue. This work presents measurements of droplet–droplet interactions in a laboratory turbulent flow, allowing reproducibility and control over initial and boundary conditions. The measured two-phase flow reproduces conditions relevant to cumulus clouds. The turbulent flow and the droplet size distribution are well characterized, and independently the collision rate is measured. Two independent experimental approaches for determining the collision rate are compared with each other: (i) a highmagnification shadowgraphy setup is employed, applying a deformation threshold as collision indicator. This technique has been specifically adapted to measure droplet collision probability in dispersed two-phase flows. (ii) Corresponding results are compared for the first time with a particle tracking approach, post-processing high-speed shadowgraphy image sequences. Using the measured turbulence and droplet properties, the turbulent collision kernel can be calculated for comparison. The two independent measurements deliver comparable orders of magnitude for the collision probability, highlighting the quality of the measurement process, even if the comparison between both measurement techniques is still associated with a large uncertainty. Comparisons with recently published theoretical predictions show reasonable agreement. The theoretical collision rates accounting for collision efficiency are noticeably closer to the measured values than those accounting only for transport.

Item URL in elib:https://elib.dlr.de/82188/
Document Type:Article
Additional Information:Published online: 17 April 2013, Paper 045010
Title:Experimental determination of droplet collision rates in turbulence
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Bordás, RóbertInstitute of Fluid Dynamics and Thermodynamics, Otto-von-Guericke-University Magdeburg, GermanyUNSPECIFIED
Roloff, ChristophInstitute of Fluid Dynamics and Thermodynamics, Otto-von-Guericke-University Magdeburg, GermanyUNSPECIFIED
Thévenin, DominiqueInstitute of Fluid Dynamics and Thermodynamics, Otto-von-Guericke-University Magdeburg, GermanyUNSPECIFIED
Shaw, R. A.Michigan Technological University, 1400 Townsend Drive, Houghton,UNSPECIFIED
Journal or Publication Title:New Journal of Physics
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In ISI Web of Science:Yes
DOI :10.1088/1367-2630/15/4/045010
Page Range:pp. 1-31
Publisher:Institute of Physics (IOP) Publishing
Keywords:laboratory turbulent flow, post-processing high-speed, collision probability, measurement process
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Aircraft Research (old)
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Simulation & Validation (old)
Location: Göttingen
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Experimental Methods
Deposited By: Micknaus, Ilka
Deposited On:27 May 2013 16:11
Last Modified:08 Mar 2018 18:47

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