Download Geophysical Turbulence Program

GTP: Geophysical Turbulence
Program
and
TNT: Turbulence Numerics Team
IMAGe Advisory board
Boulder, January 26, 2009
1
Geophysical Turbulence Program
• GTP has been in existence almost since the beginning of NCAR
(Deardorff, Gilman, Herring, Leith, Lilly, Lorenz, McWilliams, Orszag, Patterson, Thompson, …)
History: see Herring, in IUTAM Symposium, Kerr & Kimura Eds, Kluwer (2000)
•
40+ members across all divisions and labs at NCAR + a few external universities
(CU, Dartmouth, LANL, Nagoya, Penn State, UCLA, Warwick)
•
GTP, @ $50k, is ~ 10% of the GTP+TNT combined budgets
Imperative: cross-cutting research with outreach
• Support research on turbulent flows in a variety of contexts, with
focused topics drawing on GTP seed funds
• Short-term (3-day) visitors, with a ``monthly’’ seminar program
• Long-term visitors, for one week [to one year, very rarely possible]
• Workshops [and schools, 2 in 20 years]
•
For the last two years: small partial support for graduate students
URGENCY: TO INVOLVE THE YOUNGER GENERATION
2
Peter Sullivan (ESSL/MMM - GTP):
Boundary layers
``The atmospheric and oceanic boundary layers may
be the most crucial ingredients in hurricane dynamics
despite their small vertical extent’’ (K. Emanuel, 2004)
SST
.
..
Cold water hurricane wake generated by ocean
turbulence and surface wave effects
.
Large eddy simulations and
.
..
modeling of turbulent flows
Storm track
and of boundary layers in
complex geophysical flows,
High wind atmospheric PBL 25m/s
with multi-scale dynamics
and physical processes.
Transition wave - turbulence
Breaking waves, spray, bubbles, turbulence?
3
Joe Tribbia (ESSL-CGD & GTP), with Jim McWilliams (UCLA-GTP)
Pathway to dissipation in the atmosphere and ocean
Thermal / mechanical driving on
planetary scale
Thin instabilities (baroclinic, frontal) drive
inertial cascades to non-rotational scales
Further instabilities (K-H, convective)
needed to get to 3D isotropic turbulence
and dissipation, and transport processes
No complete GFD simulation to date. It
must span a 2D range from 106 m
to 10-100m
(3D Turbulence), waves and anisotropy (rotation and/or stratification and/or magnetic fields
4
and/or bottom topography …)
GTP possible mission statement
• The Geophysical Turbulence Program at NCAR
investigates nonlinear multi-scale eddy-wave
interactions for a wide range of geophysical and
astrophysical flows. It also develops, analyzes
and validates analytical and phenomenological
models, numerical methods and experiments as
tools for UCAR and for the university community,
here and abroad.
• Retreat + meeting of GTP to be organized in 2009
(Joe Tribbia)
• To be followed by a meeting of a small advisory
board (as per the request of the NCAR review panel many years ago …)
5
GTP seminars in 2007 and/or 2008
J. Baerenzung (NCAR): Spectral modeling of utrbulent fluids
G. Boffetta (LANL): Two-dimensional turbulence.
C. Bustamante (U. Warwick): Singularities of the Euler equations.
P. Hamlington (U. Mich.:, Reynolds stress anisotropy and vorticity alignment.
S. Heinz (U. Wyoming): Unified stochastic and deterministic turbulence models (07).
J. Liu (CSU): Characteristic methods for fluid transport problems.
D. Stanescu (U. Wyoming): Discontinuous Galerkin methods (07).
A. Tuck (NOAA): A molecular view of vorticity and turbulence.
V. Uritsky (U. Calgary): Self-organized criticality.
…
… MHD (W-C Müller, W-H Matthaeus, …)
6
GTP visitors and graduate students - 07 &/or 08
M-E Brachet, ENS-Paris: codes with symmetries in MHD, RK4 and Euler flow with helicity.
J.F. Cossette (grad. student, U. Montreal, with Piotr Smolarkiewicz): Semi-Lagrangian schemes.
M. Damron (grad. student, U. Arizona, with Larry Winter): a non-Markovian model of rill erosion.
J. Finnigan (Commonwealth Scient.): Canopy turbulence in roughness sub-layers
D. Jarecka (grad. student, U. Warsaw, with Wojciech Grabowski): Impact of entrainment and
mixing on cloud dynamics and microphysics.
H. Jonker, U. Delft: A refined view of vertical transport by cumulus convection.
P. Ortiz, U. Granada: Coupled dynamics of boundary layers & evolutionary landforms like dunes.
Z. Piotrowski, U. Warsaw: Numerical realizability of thermal convection.
L-P Wang, U. Delaware: Turbulent collision-coalescence of cloud droplets and impact on warm
rain initiation.
7
Collision-coalescence processes
in cloud microphysics
Wang, Franklin, Ayama & Grabowski - ESSL/MMM-GTP
• PDF of angle of
approach of colliding
droplets: dominance of
inward relative motion
due to turbulence
•
Solid line: model with turbulence
black dots: Direct Numerical
Simulation (DNS)
8
GTP/TNT workshops
08 Theme of year: 3-wks Summer School & 3 wkshps (K. Julien @CU, CISL-EOL-ESSL-RAL)
* Theory and modeling of Geophysical Turbulence: LANL (B. Wingate) + Wisconsin (L. Smith)
* Petascale computing for Geophysical Turbulence: CORA (J. Werne) + UCLA (B. Stevens)
* Observations and sensors: RAL (L. Cornman) + EOL (S. Oncley) + ESSL (R. Lenschow)
(J. Fernando [AZ] in charge of the Observation week of the summer school)
No magnetic field in TOY-08 …
2009?: Turbulent mixing in the upper ocean & boundary layers (W. Large, ESSL-CGD)
2010: Rotating stratified flows (V. Zeitlin, Paris et al.)
Past workshops:
• Turbulence and Dynamos at Petaspeed (2007)
• Turbulence and Scalar Transport in Roughness Sub-layers (2006)
• Modeling MHD turbulence with applications to planetary and stellar dynamos (2006)
• Theme of the Year (TOY-06) on Multi-scale modeling (one workshop sponsored)
• Coherent Structures in the Atmosphere and Ocean (2005)
• Atmospheric Turbulence and Mesoscale Meteorology (2005)
• Cumulus Parameterization in the Context of Turbulence Studies (2004)
9
A sample of GTP-supported research [1]
• G. Branstator (ESSL-CGD) & J. Berner (now in MMM): distinct signatures
of nonlinearity in climate dynamics
• W. Grabowski (ESSL-MMM): Parameterization of small-scale and
micro-scale processes in models resolving larger scales
• J. Herring (ESSL-MMM): Stratified turbulence
• R. Lenschow (ESSL-MMM): Analysis of C-HATS experiment
(Horizontal Array Turbulence Studies, + Oceans, Canopies, Anisotropy)
• C-H Moeng (ESSL-MMM) with J. McWilliams (UCLA), R. Rotunno
(MMM), P. Sullivan (MMM) & J. Weil (CIRES/CU) : Evaluation of twodimensional Planetary Boundary Layer (PBL) models using Large Eddy
Simulations (LES)
10
Passive versus active scalar in the dry
PBL using LES in a large domain 10002X128 or 502km X 6km
Peter Sullivan, ESSL-MMM -& GTP:
(comparable to a field campaign)
Passive scalar is at large scales
Dynamically active scalar is at
the velocity scale (depth of PBL)
11
A sample of GTP-supported research [2]
• M. Rast (CU): Convection + ionisation in the solar convection
zone
• P. Sullivan (ESSL-MMM) et al.: wind-wave interactions;
• J. Tribbia (ESSL-CGD): Multi-scale and climate
New!
• J. Berner (ESSL-MMM) et al.: stochastic parametrization for
numerical weather prediction (NWP) with flow-dependent
formulation of unresolved processes
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Stochastic parameterization
of spectral backscatter for
NWP and climate model-error
 Stream function perturbations with a
prescribed kinetic energy spectrum:
J. Berner, A. Fournier, S-Y. Ha, J. Hacker & C. Snyder
 Successfully applied to probabilistic NWP
(ECMWF pseudo-spectral model) by Shutts
(2005), and Berner et al. (2009).
Ongoing: Implementation into WRF
limited-area ensemble model using 2D
planar Fourier analysis.
Preliminary Result:
the Brier score of u is improved (shown is
score for events 0 < u < (p), where (p) is
climatological standard deviation at
13
pressure p), but more samples are needed.
Action item for GTP
Commonality of issues in fundamental multi-scale dynamics for
the Earth’s atmosphere and ocean, and for solar and solarterrestrial physics
• Request for a quadrupling of the funds (50k
– Create a GTP Post-doctoral fellow
– Create a GTP Graduate student position
– Create a sabbatical GTP visitor
200k):
The over-arching goal is to investigate and model turbulent
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flows in weather, climate, solar physics and space weather
Action item for GTP
Commonality of issues in fundamental multi-scale dynamics for the Earth’s
atmosphere and ocean, and for solar and solar-terrestrial physics
• Request for a quadrupling of the funds (50k
– Create a GTP Post-doctoral fellow
– Create a GTP Graduate student position
– Create a sabbatical GTP visitor
200k):
Decision making process: annual meeting of GTP members
(+)
The over-arching goal is to investigate and model turbulent flows in
weather, climate, solar physics and space weather
15

And now, the Turbulence Numerics Team
16
Aimé Fournier
Project Sc. @1 FTE
Pablo Mininni
Scientist 1 @ 0.25
AP @ 0.6
QuickTime™ and a
decompressor
are needed to see t his picture.

Duane Rosenberg,
Software Eng. III,
@ 1 FTE
TNT Team yesterday
Core of 2.85 FTE
Julien Baerenzung,
Post-doc, 1 FTE
(until June 2009)
Ed Lee, GRA, 0.5 FTE
(until January 22, 2009)
17
+ 1 GRA + 1 post-doc
75% at Buenos Aires
Aimé Fournier
Project Sc. @1 FTE
40% deputy director of ESSL
Pablo Mininni
Scientist 1 @ 0.25
AP @ 0.6
QuickTime™ and a
decompressor
are needed to see t his picture.

Duane Rosenberg,
Software Eng. III,
@ 1 FTE
TNT Team yesterday
Core of 2.85 FTE
Julien Baerenzung,
Post-doc
(until June 2009)
Ed Lee, GRA, 0.5 FTE
(until January 22, 2009)
18
+ 1 GRA + 1 post-doc
At some point in June 2009:
Core of 1.85 FTE
No GRA and no post-doc
Two NSF gants submitted in 2008
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Imperative
•
Investigate the basic properties of multi-scale flows
•
Exploit their commonality - multi-scale interactions,
nonlinear phenomena, geophysical turbulence, eddies and waves
* Analyze data and implement a variety of turbulence models
•
•
Seed the applications for the Earth and beyond:
atmosphere, ocean, PBL, solar physics and space weather
To that effect, develop, test and make available a suite
of tools and data sets @ petascale and beyond
(computing, and also accessing, visualizing, analyzing & sharing the data)
20
Imperative
•
Investigate the basic properties of multi-scale flows
At the highest possible Reynolds number(s)
•
Exploit their commonality - multi-scale interactions,
nonlinear phenomena, geophysical turbulence, eddies and waves
* Analyze data and implement a variety of turbulence models
•
•
Seed the applications for the Earth and beyond:
atmosphere, ocean, PBL, solar physics and space weather
To that effect, develop, test and make available a suite
of tools and data sets @ petascale and beyond
(computing, and also accessing, visualizing, analyzing & sharing the data)
21
Basic research by way of two large runs
done at NCAR with GHOST on 15363 points,
thanks to BTS and ASD allocations
I. 2006: Magnetohydrodynamics
(MHD), without rotation
•
R ~ 1700
GHOST
First evidence of a dual direct
energy cascade: isotropic k-3/2 at
large scale, anisotropic k-2 weak
turbulence at small scale in the
highest-ever Reynolds MHD run
•
First numerical evidence of
rolling up of vorticity & current sheets

Pablo Mininni et al.
22
Going beyond, with the help of symmetries
• First evidence of lack of universality in decaying MHD
without a uniform magnetic field (20483 equiv. grid):
Taylor-Green flow, 3 runs, 3 different energy spectra
Collision of two current sheets
(viz.: VAPOR, CISL)
Ed Lee et al.
Phys. Rev. E 2008/12
kaleidoscope
23
MAYTAG
Going beyond, with the help of symmetries
• First evidence of lack of universality in decaying MHD
without a uniform magnetic field (20483 equiv. grid):
Taylor-Green flow, 3 runs, 3 different energy spectra
Ed Lee et al., in preparation
Collision of two current sheets
(viz.: VAPOR, CISL)
Ed
Phys.Lee
Rev.etEal.2008/12
kaleidoscope
24
MAYTAG
Going beyond [2]
Developing, testing, or using models for fluid & MHD turbulence:
* Chollet-Lesieur model
* Lagrangian averaged model (D. Holm, …)
* Spectral model based on EDQNM (two-point turbulence closure)
^ with eddy viscosity incorporating helical terms
^ with eddy noise incorporating phase information
^ for any energy spectrum
(Julien Baerenzung et al.)
Applications to Navier-Stokes (including rotation) and MHD
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Second large run at NCAR
II. 2008: Rotation with helical
forcing, without magnetic field
•
R ~ 1100 , Ro = 0.05
GHOST
First evidence of a non-intermittent
and non-Kolmogorovian direct energy
cascade at low Rossby number,
governed by the direct cascade of
helicity (h+e=4), together with an
inverse cascade of energy
•
First evidence of the persistence of
strong cyclonic events in rotating
turbulence in the presence of
helicity, together with strongly
turbulent columnar structures


Pablo Mininni et al.
Vorticity magnitude (zoom), above a threshold
26
Second large run at NCAR
II. In 2009:
* Analysis and
modeling of
the large run
with rotation
and helical forcing
R ~ 1100 , Ro = 0.05
• Parametric study
using the model TBD
Thanks to a special
CISL 5 mo. post-doc
allocation for JB
27

Closer look of vorticity magnitude, above a threshold: cohabitation
Going beyond: Modeling of rotating flows
Model: Eddy viscosity
and eddy noise with
variable index energy
spectrum

Tests on non-helical
flows down to Rossby
numbers of 0.02

Fig.: Build-up of
anisotropy over time
Julien Baerenzung et al., in
preparation
QuickTime™ and a
decompressor
are needed to see this picture.
Taylor-Green flow
GHOST + X
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Adaptive Mesh
Refinement
2D-Navier-Stokes
Aimé Fournier et al., 2008
•
Decay for long times
(incompressible)
•
Formation of dipolar vortex
structures
•
Gain in the number of
degrees of freedom (~ 4) with
AMR, compared to an
equivalent pseudo-spectral
code (periodic boundary
conditions)
GASPAR
29
Spectral AMR

The need for accuracy
in adaptive mesh
refinement, when looking
at max. norms (Fig.: current
in 2D-MHD reconnection)
Duane Rosenberg et al (2007)
Also: Development of optimized Schwarz
preconditioning, in collaboration with Amik
St Cyr
New: Implementation of a conservative energy
scheme (AF +DR)
30
GASPAR
Available TNT tools
• GASpAR: High-order adaptive Mesh Refinement code for turbulent
flow, and a PDE framework for adaptive mesh solutions
* Future: Boussinesq equations, 3D-MHD, Planetary Boundary Layer
• GHOST: Primary production pseudo-spectral code for turbulent flows
Modular numerics and physics: 2D/ 3D; compressibility; (Hall)-MHD; rotation
* Plans: * Stratification, and implementation of (several) LES
* Upgrade for petascale and beyond (today: up to ~ 4000 proc.)
^^^^^^^^^^
•
Other code: MAYTAG: MAgnetohYdrodynamics TAylor-Green code with
enforced symmetries leading to a gain of 32 in CPU / storage
Code developed in F’08 by M-E Brachet (ENS Paris)
31
Available high Reynolds number
numerical data sets
(runs performed at NCAR, NERSC and Pittsburgh)
• Navier-Stokes:
^ Taylor-Green (TG) flows, 20483 grids
^ ABC flows, 20483 grids
• Navier-Stokes with rotation: ABC, decay,15363 grid
• MHD:
^ 10243 forced dynamo runs;
^ 15363 grid, decaying flow;
^ 20483 equivalent grids with imposed TG symmetries
Taylor Reynolds numbers of 1100 or above
32
New research directions
1- Basic research in rotating turbulent flows (in progress):
Numerical simulations, phenomenological approach, and
spectral modeling (with helicity and with eddy noise)
2 - Stratified turbulent flows (GHOST)
(with/without rotation, boundaries, passive tracer; & numerical adaptivity)
Potential targeted applications to the stable planetary boundary layer
(with Peter Sullivan, ESSL; & Rod Frechlich, RAL)
and to aircraft safety (with Larry Cornman, RAL)
3 - Bottom topography using non-uniform mesh (GASPAR)
33
New needs: Action items for TNT
1- Basic research in rotating turbulent flows (in progress): Numerical simulations,
phenomenological approach, and spectral modeling
2 - Stratified turbulent flows (with/without rotation, boundaries, passive tracer;
and numerical adaptivity). Potential targeted applications to the stable planetary
boundary layer and to aircraft safety (with ESSl and RAL)
3 - Bottom topography, using mesh adaptivity
A- Tools for the community (GASPAR, GHOST), going to petascale and beyond
B- High-Reynolds number data sets for the community, and how to handle these data sets
• A- Sustain the TNT team at its present level
• B- Recruit in TNT a Scientist 1 or Scientist 2
in weather/climate turbulence and its modeling
C- Obtain substantial computer resources including in the team
34
TNT collaborations at NCAR, past and present:
Tom Bogdan (now at NOAA), Paul Charbonneau (now at Montreal), John Clyne (CISL),
Larry Cornman (RAL), Rod Frehlich (RAL and CU), Jack Herring (emeritus, ESSL-M3),
Han-Li Liu (ESSL-HAO), Alan Norton (CISL), Amik St Cyr (IMAGE-CISL),
Peter Sullivan (ESSL-MMM), Joe Tribbia (ESSL-CGD), …
TNT collaborations outside NCAR, past and present:
A. Alexakis (Paris), F. Baer (U. Md), A. Bhattacharjee (UNH), M-E Brachet (Paris),
B. Breech (U Del.), M. Bustamante (Dublin), V. Carbone (Calabria),
C. Cartes (Santiago), S. Cowley (UCLA), P. Dmitruk (Buenos Aires),
P. Fisher (Argonne), S. Galtier (Orsay), K. Germaschewski (UNH), J. Graham (Lindau),
D. Holm (Imperial, LANL), G. Krstulovic (Paris), D. Lathrop (U. Md), W-H Matthaeus
(Bartol), D. Montgomery (Dartmouth), C-S Ng (Alaska), J-F Pinton (Lyon), H. Politano
(Nice), Y. Ponty (Nice), J. Toomre (CU), M. Rast (CU), R. Reddy (PSC), J. Riley (U.
Washington), M. Taylor (Sandia), L. Turner (Cornell), V. Uristsky (Calgary),
H.
Wang (U. Md), …
35
Publications with reviewers, 2007-2009
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[1]
Alexakis, A., P. D. Mininni, A. Pouquet, 2007: Turbulent cascades, transfer, and scale interactions in
magnetohydrodynamics. New J. Phys., 9, 298, doi: 10.1088/1367-2630/9/8/298.
Baerenzung, J., H. Politano, Y. Ponty, A. G. Pouquet, 2008: Spectral modeling of turbulent flows and the role of helicity.
Phys. Rev. E, 77, 046303, doi: 10.1103/PhysRevE.77.0463033
J. Baerenzung, H. Politano, Y. Ponty and A. Pouquet,, `Spectral Modeling of Magnetohydrodynamic Turbulent Flows,'’
Phys. Rev. E 78, 026310 (2008).
Carbone, V., A. G. Pouquet, 2008: An introduction to fluid and MHD turbulence for astrophysical flows: Theory,
observational and numerical data and modeling. Invited set of Lectures EEC School on Astrophysical Plasmas, L Vlahos
and P Cargill, Ed., Springer-Verlag, 69-131
Carlos Cartes, Miguel D. Bustamante, Annick Pouquet, Marc E. Brachet,Generalized Eulerian-Lagrangian description of
Navier-Stokes and resistive MHD dynamics,'' Fluid Dyn. Res, 41, 011404 (2009).
Clyne, J., P. Mininni, A. Norton, M. Rast, 2007: Interactive desktop analysis of high resolution simulations: Applications to
turbulent plume dynamics and current sheet formation. New J. Phys., 9, 301, doi: 10.1088/1367-2630/9/8/301.
Cowley, S., J.-F. Pinton, A. Pouquet, 2007: Focus on magnetohydrodynamics and the dynamo problem. New J. Phys., 9,
E04, doi: 10.1088/1367-2630/9/8/E04
A. Fournier, D. Rosenberg and A. Pouquet, ``Dynamically adaptive spectral-element simulations of 2D incompressible
Navier-Stokes vortex decays,'' to appear, GAFD, Special issue `` Vortex dynamics from quantum to geophysical scales,'’
Guest Editors: C. Barenghi, D. Dritschel and A. Gilbert (2008).
Graham Pietarila, J., D. D. Holm, P. Mininni, A. G. Pouquet, 2008: Three regularization models of the Navier-Stokes
equations. Phys. Fluids, 20, 035107, doi: 10.1063/1.2880275.
Graham Pietarila, J., D. Holm, P. Mininni, A. G. Pouquet, 2008: Highly turbulent solutions of the Lagrangian-averaged
Navier-Stokes alpha model and their large-eddy-simulation potential. Phys. Rev. E, 75, 056310, doi:
10.1103/PhysRevE.76.056310.
•
J. Pietarila Graham, P.D. Mininni, and A. Pouquet, The Lagrangian-averaged model for magnetohydrodynamic turbulence and the absence of
bottleneck, Phys. Rev. E, to appear (2009).
•
E. Lee, M.E. Brachet, A. Pouquet, P.D. Mininni and D. Rosenberg,``A paradigmatic flow for small-scale
magnetohydrodynamics,'’ Phys. Rev. E 78, 066401 (2008).
Matthaeus, W. H., A. G. Pouquet, P. Mininni, P. Dmitruk, B. Breech, 2008: Rapid directional alignment of velocity and
magnetic field in magnetohydrodynamic turbulence. Physical Review Letters, 100, 085003, doi:
10.1103/PhysRevLett.100.085003.
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[2]
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P.D. Mininni, A. Alexakis and A. Pouquet, Scale interactions and scaling laws in rotating flows at moderate Rossby
numbers and large Reynolds numbers,'' Phys. Fluids 21, 015108 (2009).
P.D. Mininni and A. Pouquet, ``Helicity cascades in rotating turbulence,'' to appear, Phys. Fluids (2009), arxiv:0809.0869.
Mininni, P., A. Alexakis, A. G. Pouquet, 2008: Non-local interactions in hydrodynamic turbulence at high Reynolds
numbers: The slow emergence of scaling laws. Phys. Rev. E, 77, 036306, doi: 10.1103/PhysRevE.77.036306.
Mininni, P., A. G. Pouquet, 2008: Energy spectra stemming from interactions of Alfven waves and turbulent eddies.
Physical Review Letters, 99, 254502, doi: 10.1103/PhysRevLett.99.254502.
Mininni, P. D., D. C. Montgomery, L. Turner, 2007: Hydrodynamic and magnetohydrodynamic computations inside a
rotating sphere. New J. Phys., 9, 303, doi: 10.1088/1367-2630/9/8/303
.Mininni, P. D., 2007: Inverse cascades and alpha effect at a low magnetic Prandtl number. Phys. Rev. E, 76, 026316, doi:
10.1103/PhysRevE.76.026316.1
Mininni, P., A.. Alexakis, A. Pouquet, 2007: Energy transfer in Hall-MHD turbulence, cascades, backscatter and dynamo
action. J. Plasma Phys., 73, 377-401, doi: 10.1017/S0022377806004624.1
Mininni, P., A. Alexakis, A. G. Pouquet, 2008: Scale interactions in hydrodynamic turbulence at large Reynold numbers.
IUTAM Book Series: IUTAM Symp. Comput. Phys. And New Perspectives in Turb., Kaneda, Y, Eds., Springer-Verlag, 4,
125-130, doi: 978 1-4020-6471-5.
P.D. Mininni, E. Lee, A. Norton, and J. Clyne, Flow visualization and field line advection in computational fluid dynamics:
application to magnetic fields and turbulent flows, New J. Phys. 10(12), 125007/1-23 (2008).
P. Mininni, P. Sullivan and A. Pouquet,``Two examples from geophysical and astrophysical turbulence on modeling
disparate scale interactions,'’ Summer school on mathematics in geophysics, Roger Temam and Joe Tribbia Eds.,
Springer Verlag, to appear (2009).
C. S. Ng, D. Rosenberg, K. Germaschewski, A. Pouquet and A. Bhattacharjee,``A comparison of spectral element and
finite difference simulations with adaptive mesh refinement for the MHD island coalescence instability problem,'’ to appear,
Astrophys. J. Suppl. (2009).
Yannick Ponty, Pablo D. Mininni, Jean-Philipe Laval, Alexandros Alexakis, Julien Baerenzung,Francois Daviaud,
Berengere Dubrulle, Jean-Fran cois Pinton, Helene Politano and Annick Pouquet, ``Linear and non linear features of the
Taylor-Green Dynamos,'’ Comptes Rendus de l'Academie des Sciences (Paris), 9, 749 (2008).
Ponty, Y., P. D. Mininni, J.-F. Pinton, H. Politano, A. Pouquet, 2007: Dynamo action at low magnetic Prandtl numbers:
Mean flow versus fully turbulent motions. New J. Phys., 9, 296, doi: 10.1088/1367-2630/9/8/296.3
Pouquet, A. G., A. Alexakis, P. Mininni, D. Montgomery, 2008: Dynamics of the small scales in magnetohydrodynamic
turbulence. IUTAM Book Series: IUTAM Symp. Comput. Phys. And New Perspectives in Turb., Kaneda, Y, Eds., SpringerVerlag, 4, 305-312, doi: 978 1-4020-6471-5.
Rosenberg, D., A. Pouquet, P. D. Mininni, 2007: Adaptive mesh refinement with spectral accuracy for MHD in two space
dimensions. New J. Phys., 9, 304, doi: 10.1088/1367-2630/9/8/304
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Wang, H., J. J. Tribbia, F. Baer, A. Fournier, M. A. Taylor, 2007: A spectral element version of CAM2. Mon. Wea. Rev., 135,
3825-3840.
Thanks to the team!
And thank you all for your attention
38
39
As an example: Summary of the GTP workshop on
Turbulence & Scalar Transport in Roughness Sub-layers (RSLs)
Jielun Sun et al., ESSL-MMM
• Types of roughness elements considered include:
–
–
–
–
–
Vegetated canopies
Urban and suburban environments
Underwater plant communities
Ocean waves
Wind farms
• Although there are similarities, profound differences in
turbulence structures are found among these RSLs depending
on rigidity and porosity of roughness elements
– Over-ocean RSLs are strongly affected by speed and direction of
swell and can impact the entire PBL.
– Imprint of urban geometry greatly impacts turbulence structures in
RSL due to building shapes and distributions.
– Underwater RSLs due to aquatic vegetation can fill entire channel
depth.

Past, present & future experiments: e.g., HATS, O-HATS, C-HATS, A-HATS
(Horizontal Array Turbulence Studies, + Oceans, Canopies, Anisotropy)
40