Tordella, Daniela

English

PORTO Publications Open Repository TOrino

Turbulence &
Clouds
Turbulence Mixing and the study of
Clouds
D.Tordella, M.Iovieno, S.Scarsoglio,
F.De Santi, S.Di Savino
in collaboration with
Z.Warhaft (Cornell Univ.), J.Riley (U.Washington),
R.Kerr (U.Warwick)
Venturefest 2012, Oxford
Turbulence &
Clouds
William Turner, “Study of Clouds”, about 1830
(Tate Gallery, London)
Turbulence &
Clouds
Motivation: Cloud entrainment
Isolated cumulous:
Entrainment throughout
the cloud depth: from
above, sides and at the
base.
Effects of gravity vary
Stratocumulous:
Entrainment mainly from
the top
Turbulence &
Clouds
Field Data
All turbulence measurements in
a stratocumulous are consistent
with laboratory experiments
(data from Siebert at al., 2009)
Turbulence &
Clouds
Field Data
Small Cumulous
Settling parameter vs. Stokes number
Upward diagonals:
dissipation rate [m2/s3]
Downward diagonals:
droplet diameters [µm]
N.B: these are averaged
values
Sv = νtνη =
St
Fr , St ≈ d2ε1/2 and Sv ≈ d2ε−1/4
Turbulence &
Clouds
Laboratory experiments
Settling particle velocity enhancement/reduction in turbulence with
gravity
Alesida et al, JFM 468 (2002)
Davila - Hunt, JFM 440 (2001)
Kawanasi-Shiozaki, J.Hydr.Eng. 134 (2008)
Lazaro-Lasheras, Phys.Fluids 1 (1989)
Murray JGR 75 (1970)
Nielsen, J.Sed.Petr. 35 (1993)
Tooby et al, JGR 82 (1977)
Wang - Maxey JFM 256 (1993)
...
Acceleration of inertial particles: Bodenschatz, Xu, Mordant, Ayyalasomayajula, Qureshi, ...
Clustering: Shaw, collins, Bec, Vassilicos, Hunt, ...
Turbulence &
Clouds
Particle diameter effect
Red : g+
Blue : g0
Black : g-
Squares: TT interface,
Circles: TN interface
Inset: particle size distri-
bution
No gravity ⇒ small &
large particles transported
the same way
Turbulence &
Clouds
Shear
from Shaw, ARFM 35 (2003)
Real clouds:
sharp interfaces
and shear
Shear is important!
Turbulence &
Clouds
What can simulations tell
http://www.polito.it/philofluid
Entrainment
Turbulence &
Clouds
Entrainment -Interface
1
0
0.2
0.4
0.6
0.8
θ
Turbulence &
Clouds
Entrainment
Energy/velocity field:
Turbulence &
Clouds
John Constable, “Study of Clouds”, about 1820
(University of Oxford, Ashmolean museum)
Turbulence &
Clouds
Conclusions
• gravity is very important in droplet distribution
• mixing is affected by large scales
• we are beginning to understand the mechanics of entrainment, but
need to know more about:
– evaporation
– shear
– convection
• rain making must understand droplet distribution and
how it changes with time
• global warming⇔ droplet size distribution
(absorbtion/reflection of light)
Interdisciplinary holistic approach is necessary!


Turbulence Mixing and the Study of Clouds, VentureFest 2012, , Building a Better Economy, June 19 2012, Said Business School, Oxford (UK)

TORDELLA, Daniela

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

04 August 2020POLITECNICO DI TORINORepository ISTITUZIONALETurbulence Mixing and the Study of Clouds, VentureFest 2012, , Building a Better Economy, June 19 2012, SaidBusiness School, Oxford (UK) / Tordella D.. - STAMPA. - Building a Better Economy(2012), pp. 65-65. ((Interventopresentato al convegno VentureFest 2012 tenutosi a Said Business School, Oxford (UK) nel June 19, 2012.OriginalTurbulence Mixing and the Study of Clouds, VentureFest 2012, , Building a Better Economy, June 192012, Said Business School, Oxford (UK)Publisher: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: 11583/2503406 since:Turbulence &CloudsTurbulence Mixing and the study ofCloudsD.Tordella, M.Iovieno, S.Scarsoglio,F.De Santi, S.Di Savinoin collaboration withZ.Warhaft (Cornell Univ.), J.Riley (U.Washington),R.Kerr (U.Warwick)Venturefest 2012, OxfordTurbulence &CloudsWilliam Turner, “Study of Clouds”, about 1830(Tate Gallery, London)Turbulence &CloudsMotivation: Cloud entrainmentIsolated cumulous:Entrainment throughoutthe cloud depth: fromabove, sides and at thebase.Effects of gravity varyStratocumulous:Entrainment mainly fromthe topTurbulence &CloudsField DataAll turbulence measurements ina stratocumulous are consistentwith laboratory experiments(data from Siebert at al., 2009)Turbulence &CloudsField DataSmall CumulousSettling parameter vs. Stokes numberUpward diagonals:dissipation rate [m2/s3]Downward diagonals:droplet diameters [µm]N.B: these are averagedvaluesSv = νtνη =StFr , St ≈ d2ε1/2 and Sv ≈ d2ε−1/4Turbulence &CloudsLaboratory experimentsSettling particle velocity enhancement/reduction in turbulence withgravityAlesida et al, JFM 468 (2002)Davila - Hunt, JFM 440 (2001)Kawanasi-Shiozaki, J.Hydr.Eng. 134 (2008)Lazaro-Lasheras, Phys.Fluids 1 (1989)Murray JGR 75 (1970)Nielsen, J.Sed.Petr. 35 (1993)Tooby et al, JGR 82 (1977)Wang - Maxey JFM 256 (1993)...Acceleration of inertial particles: Bodenschatz, Xu, Mordant, Ayyalasomayajula, Qureshi, ...Clustering: Shaw, collins, Bec, Vassilicos, Hunt, ...Turbulence &CloudsParticle diameter effectRed : g+Blue : g0Black : g-Squares: TT interface,Circles: TN interfaceInset: particle size distri-butionNo gravity ⇒ small &large particles transportedthe same wayTurbulence &CloudsShearfrom Shaw, ARFM 35 (2003)Real clouds:sharp interfacesand shearShear is important!Turbulence &CloudsWhat can simulations tellhttp://www.polito.it/philofluidEntrainmentTurbulence &CloudsEntrainment -Interface100.20.40.60.8θTurbulence &CloudsEntrainmentEnergy/velocity field:Turbulence &CloudsJohn Constable, “Study of Clouds”, about 1820(University of Oxford, Ashmolean museum)Turbulence &CloudsConclusions• gravity is very important in droplet distribution• mixing is affected by large scales• we are beginning to understand the mechanics of entrainment, butneed to know more about:– evaporation– shear– convection• rain making must understand droplet distribution andhow it changes with time• global warming⇔ droplet size distribution(absorbtion/reflection of light)Interdisciplinary holistic approach is necessary!

https://iris.polito.it/retrieve/handle/11583/2503406/58396/pres_nuvole.pdf

Turbulence Mixing and the Study of Clouds, VentureFest 2012, , Building a Better Economy, June 19 2012, Said Business School, Oxford (UK)

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