title: Wetting and Spreading of Molten Volcanic Ash in Jet Engines.
abstract: A major hazard to jet engines posed by volcanic ash is linked to the wetting and spreading of molten ash droplets on engine component surfaces. Here, using the sessile drop method, we study the evolution of the wettability and spreading of volcanic ash. We employ rapid temperature changes up to 1040-1450 °C, to replicate the heating conditions experienced by volcanic ash entering an operating jet engine. In this scenario, samples densify as particles coalesce under surface tension until they form a large system-sized droplet (containing remnant gas bubbles and crystals), which subsequently spreads on the surface. The data exhibit a transition from a heterogeneous to a homogeneous wetting regime above 1315 °C as crystals in the drops are dissolved in the melt. We infer that both viscosity and microstructural evolution are key controls on the attainment of equilibrium in the wetting of molten volcanic ash droplets.
authors.affiliation: Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München , Theresienstrasse 41, 80333 Munich, Germany.
authors.forename: Wenjia
authors.identifier: http://orcid.org/0000-0002-5276-5326
authors.initials: W
authors.lastname: Song
authors.affiliation: Earth, Ocean and Ecological Sciences, University of Liverpool , Liverpool, L69 3GP, United Kingdom.
authors.forename: Yan
authors.initials: Y
authors.lastname: Lavallée
authors.affiliation: Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München , Theresienstrasse 41, 80333 Munich, Germany.
authors.forename: Fabian B
authors.initials: FB
authors.lastname: Wadsworth
authors.affiliation: Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München , Theresienstrasse 41, 80333 Munich, Germany.
authors.forename: Kai-Uwe
authors.initials: KU
authors.lastname: Hess
authors.affiliation: Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München , Theresienstrasse 41, 80333 Munich, Germany.
authors.forename: Donald B
authors.initials: DB
authors.lastname: Dingwell