Codoni, David

GOLSHAN KOVIJI, Mina

Iovieno, Michele

Ruggiero, Vittorio

Tordella, Daniela

Vanni, Marco

English

David Codoni

Mina Golshan

Vittorio Ruggiero

Michele Iovieno

Marco Vanni

Daniela Tordella

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)

04 August 2020POLITECNICO DI TORINORepository ISTITUZIONALEWater droplets simulation in a warm cloud-like ambient / Codoni, David; GOLSHAN KOVIJI, Mina; Ruggiero, Vittorio;Iovieno, Michele; Vanni, Marco; Tordella, Daniela. - ELETTRONICO. - (2018). ((Intervento presentato al convegnoEUROMECH Colloquium 596:Numerical simulations of flows with particles, bubbles and droplets. tenutosi a Venice, Italynel 9 May – 11 May 2018,.OriginalWater droplets simulation in a warm cloud-like ambientdefault_conf_editorialPublisher:PublishedDOI:Terms of use:openAccessPublisher copyright-(Article begins on next page)This article is made available under terms and conditions as specified in the  corresponding bibliographic description inthe repositoryAvailability:This version is available at: 11583/2725563 since: 2019-02-19T11:12:31ZEUROMECH Colloquium 596:Numerical simulations of flows with particles, bubbles and droplets.EUROMECH Colloquium 596: Numerical simulations of flows with particles, bubbles and droplets.Water droplets simulation in a warm cloud-like ambientDavid CodoniPolitecnico di TorinoMina GolshanPolitecnico di TorinoVittorio RuggieroCINECA-SCAI RomeMichele IovienoPolitecnico di TorinoMarco VanniPolitecnico di TorinoDaniela Tordella∗Politecnico di TorinoSimulations of lukewarm clouds usually assume static and homogeneous conditions on average.However, we are here interested in the unsteady dynamics of the transport through the interface betweencloud and the clear air surrounding it. Clouds in fact are fugitive in nature. If one looks for a fewseconds, they seem to keep the same form. When looking again, after a minute, one finds that aresomewhat changed. Hardly then extended cloud formations can live for more than 2-3 days. Theirspatial structure is in-homogenous with continuous changes associated with a large set of coexistingtimescales.In our numerical simulation, the cloud interface is modeled through two interacting regions at dif-ferent turbulent intensity [1, 2]. Different initial conditions reproduce possible local stable or unstablestratification in density and temperature. Currently, our droplet model includes evaporation, condensa-tion, collision and coalescence. The typical water content, associated to an initial condition where dropsare 30 microns in diameter, leads to an initial number of drops of 1011 in a cloud volume of about 500cubic meters. A computational grid up to 2048x1024x1024 points is used leads to a Taylor’s microscaleReynolds number of 250. The governing equations are NS equations in Boussinesqs approximationcoupled to equations describing the evolution of water drops seen as inertia particles, transported bybackground turbulence and gravity.One aim is the determination of the clustering feature of water droplets inside the shearles turbulentmixing at the clear air – cloud interface. We compute the distrution of the droplet size and comparethe distribution shape with those obtained in a laboratory chamber where turbulent cloud formation isenabled via moist convection [3]. This to deduce information on the possible aerosol/nucleation inputsleading to the local cloud state produced in the simulation.References[1] M. Iovieno, D. Tordella, Small-Scale Anisotropy in Turbulent Shearless Mixing, Physical ReviewLetters, 107(19), 194501, 2011.[2] M. Iovieno, S. Di Savino, L. Gallana, D. Tordella, Mixing of a passive scalar across a thin shearlesslayer: concentration of intermittency on the sides of the turbulent interface, Journal of Turbulence,15(5), pp. 311–334, 2014.[3] K.K.Chandrakar, W. Cantrell, K. Chang, D. Ciocchetto, D. Niedermeier, M. Ovchinnikov, R. A.Shaw, F. Yang, Aerosol indirect effect from turbulence-induced broadening of cloud-droplet sizedistributions, PNAS, 113(50), pp. 14243–14248, 2016.∗Email:daniela.tordella@polito.itFigure 1: DNS of the transient clustering of water droplets across a shearless turbulent mixing. Reλ ∼100, x3 cross mixing direction, L linear scale of the cloud portion under study.2

Water droplets simulation in a warm cloud-like ambient

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Water droplets simulation in a warm cloud-like ambient

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