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Experimental investigation of the aggregation‐disaggregation of colliding volcanic ash particles in turbulent, low‐humidity suspensions
Author(s) -
Del Bello Elisabetta,
Taddeucci Jacopo,
Scarlato Piergiorgio,
Giacalone Emanuele,
Cesaroni Claudio
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl062292
Subject(s) - volcanic ash , suspension (topology) , volcano , turbulence , particle (ecology) , relative humidity , particle aggregation , kinetic energy , particle size , drag , materials science , atmospheric sciences , mineralogy , geology , physics , meteorology , mechanics , nanoparticle , nanotechnology , paleontology , oceanography , mathematics , quantum mechanics , homotopy , pure mathematics , seismology
We present the results of laboratory experiments on the aggregation and disaggregation of colliding volcanic ash particles. Ash particles of different composition and size <90 µm were held in turbulent suspension and filmed in high speed while colliding, aggregating, and disaggregating, forming a growing layer of electrostatically bound particles along a vertical plate. At room conditions and regardless of composition, 60–80% of the colliding particles smaller than 32 µm remained aggregated. In contrast, aggregation of particles larger than 63 µm was negligible, and, when a layer formed, periods when disaggregation (mainly by collisions or drag) exceeded aggregation occurred twice as frequently than for smaller particles. An empirical relationship linking the aggregation index, i.e., the effective fraction of aggregated particles surviving disaggregation, to the mean particle collision kinetic energy is provided. Our results have potential implications on the dynamics of volcanic plumes and ash mobility in the environment.