The Solar Course, the Chemic Force, and the Speeding Change of Water

17 Oct 2011, 08:00 → 21 Oct 2011, 18:00 Europe/Stockholm

Nordita lecture room (NORDITA)

Dhrubaditya Mitra (Asssitant Professor)

→ link to photos and conference picture (taken by Chi-kwan Chan, Nordita)

→ link to video server with all recordings.

A multidisciplinary program to celebrate the 70th birthday of Uriel Frisch. The principal scientific topics are going to be turbulence, nonlinear dynamics, statistical mechanics, atmospheric and biological applications of nonlinear physics.
A tentative list of themes includes

  (1) Fluid turbulence
  (2) Turbulent dynamo
  (3) Optimal transport and applications
  (4) Biologically inspired problems

Scientific organizing committee:

 Erik Aurell
 Jeremie Bec
 M-E Brachet
 Axel Brandenburg
 Takeshi Matsumoto
 Annick Pouquet
 Andrei Sobolebski
 Zhen-Su She
 Dario Vincenzi
 Massimo Vergassola

Local organizing committee:

 Erik Aurell
 Axel Brandenburg
 Dhrubaditya Mitra

The meeting is sponsored jointly by Nordita, Swedish Research Council, CNRS, and the Astrophysical Dynamo ERC Project

Monday 17 October

09:30 → 10:00 Turbulent convection in three, two and one dimensions.

Speaker: G Boffetta

Slides boffetta.pdf

video http://video.physto.se/NORDITA20111017/Day1_Part1.WMV

10:00 → 10:30 Energy and enstrophy cascades in large scale atmospheric turbulence

Speaker: E. Lindborg

Slides Erik_Lindborg_Nordita2011.pdf

video http://video.physto.se/NORDITA20111017/Day1_Part2.WMV

11:00 → 11:30 Asymptotic stability of heteroclinic cycles

Dynamical systems, equivariant under the action of a non-trivial symmetry group, can possess structurally stable heteroclinic cycles. We consider stability properties of a class of structurally stable heteroclinic cycles in $\R^n$, which we call heteroclinic cycles of type Z. It is well-known that a heteroclinic cycle, that is not asymptotically stable, can attract nevertheless a positive measure set from its neighbourhood. We call such cycles fragmentarily asymptotically stable. Necessary and sufficient conditions for fragmentary asymptotic stability are expressed in terms of eigenvalues and eigenvectors of transition matrices. If all transverse eigenvalues of linearisations near steady states that are involved in the cycle are negative, then the condition for asymptotic stability is that the transition matrices have an eigenvalue larger than one in absolute value. Finally, we discuss bifurcations occurring when the conditions for asymptotic stability or for fragmentary asymptotic stability are broken

Speaker: O. Podvigina

Slides talk.pdf

video http://video.physto.se/NORDITA20111017/Day1_Part3.WMV

11:30 → 12:00 Computing non-equilibrium stationary states by message-passing?

Speaker: E. Aurell

video http://video.physto.se/NORDITA20111017/Day1_Part4.WMV

12:00 → 12:30 Rotating Turbulence and return to isotropy.

Speaker: A. Pouquet

Slides pouquet_STOCKHOLM_shorter.pdf

video http://video.physto.se/NORDITA20111017/Day1_Part5.WMV

14:30 → 15:15 Dynamics of the glassy state of matter

Speaker: I. Procaccia

video http://video.physto.se/NORDITA20111017/Day1_Part6.WMV

15:45 → 16:15 Pirouette effect in turbulence

Speaker: A. Pumir

video http://video.physto.se/NORDITA20111017/Day1_Part7.WMV

16:15 → 16:45 Scaling and Intermittency in fluctuating Alpha-Shear dynamos

We consider mean-field dynamo models with fluctuating \alpha effect, both with and without shear. The \alpha effect is chosen to be Gaussian white noise with zero mean and given covariance. We show analytically that the mean magnetic field does not grow, but, in an infinitely large domain, the mean-squared magnetic field shows exponential growth of the fastest growing mode at a rate proportional to the shear rate, which agrees with earlier numerical results of Yousef et al (2008) and recent analytical treatment by Heinemann et al (2011) who use a method different from ours. In the absence of shear, an incoherent \alpha^2 dynamo may also be possible. We further show by explicit calculation of the growth rate of third and fourth order moments of the magnetic field that the probability density function of the mean magnetic field generated by this dynamo is non-Gaussian.

Speaker: D. Mitra (NORDITA)

Slides talk_dhruba.pdf

video http://video.physto.se/NORDITA20111017/Day1_Part8.WMV

Tuesday 18 October

09:00 → 09:45 Optimization in astrophysics

Speaker: R. Mohayee (AIP, Paris)

09:45 → 10:15 Negative effective magnetic pressure instability

We present the first demonstration of the negative effective magnetic pressure instability in direct numerical simulations of stably stratified, externally forced, isothermal hydromagnetic turbulence in the regime of large plasma beta. By the action of this instability, an initially uniform horizontal magnetic field forms flux concentrations whose scale is large compared to the turbulent scale. We further show that the magnetic energy of these large-scale structures is only weakly dependent on the magnetic Reynolds number, provided its value is large enough for the instability to be excited. Our results support earlier mean-field calculations and analytic work which identified this instability. Applications to the formation of active regions in the Sun are discussed. [Astrophys. J. Lett. 740, L50 (2011) ]

Speaker: A. Brandenburg

Slides FrischFest11.pdf

11:00 → 11:30 Nelkin scaling for ¨burgulence¨

Speaker: S. Chakraborty (NBI, Copenhagen)

Slides UF_bday_Stockholm.pdf

11:30 → 12:00 Relaxation of Galerkin-Truncated Gyrokinetic, and back to Magenticfluids

The gyrokinetic absolute equilibrium will be reviewed. Some numerical results of gyrokinetic simulations will be presented. Two-fluid magneticfluid absolute equilibrium is used to investigate two-fluid effects, effects of various helicities et al. This talk try to bring some new insights into the kinetic and two-fluid effects in magnetized plasma turbulence in fusion device, space and astrophysics.

Speaker: J-Z Zhu

Slides StockholmTalk1.pdf

12:00 → 12:30 Condensates in two dimensional turbulence

We derive and numerically confirm that the saturation of energy condensation in two-dimensional turbulence is governed by the balance between forcing and small-scale dissipation. The time scale of saturation is inversely proportional to the viscosity but the saturation energy level is determined by both viscosity and the forcing scale. It is shown that, because the energy dissipation is proportional to the enstrophy, which itself is a conserved quantity in the ideal case, it is necessary to resolve the enstrophy spectrum to achieve numerical consistency. We also find that the movement of the condensate vortices can be described as Brownian motion of an inertial particle. [arXiv:1109.6937v1]

Speaker: C-K Chan

Slides ck-Condex.pdf

14:30 → 15:30 On the Evolution of Texts: An Introduction to Stemmatology

Speaker: T Roos

Slides stockholm.pdf

15:30 → 16:30 Nothing new under the burning sun? Climate and verbs in North-West Semitic

Speaker: O. Wikander

Wednesday 19 October

09:00 → 09:45 Time Scales, Persistence, and Dynamic Multiscaling in Turbulence

Speaker: R. Pandit (IISc, Bangalore)

Slides stockholm_pandit.pdf

09:45 → 10:15 Orientation of non-symmetric particles in axisymmetric random flows

Speaker: D. Vincenzi

Slides NORDITA.pdf

10:45 → 11:15 Navier-Stokes in hyperbolic plane

Speaker: ENS, Lyon Gawedzki

Slides Stockholm.pdf

11:15 → 11:45 Axial dipolar dynamo action in Taylor-Green vortex

Speaker: M-E Brachet

Slides Talk_Stocholm_2011.pdf

11:45 → 12:15 Role of polymers in the mixing of Rayleigh-Taylor turbulence

The role of polymer additives on Rayleigh-Taylor turbulence is investigated by means of direct numerical simulations (DNS) of Oldroyd-B viscoelastic model. The dynamics of polymer elongations follows adiabatically the self-similar evolution of the turbulent mixing layer and shows the appearance of a strong feedback on the flow which originates a cut off for polymer elongations. The viscoelastic effects on the mixing properties of the flow are twofold. Mixing is appreciably enhanced at large scales (the mixing layer growth-rate is larger than that of the purely Newtonian case) and depleted at small scales (thermal plumes are more coherent with respect to the Newtonian case). The observed speed up of the thermal plumes, together with an increase of the correlations between temperature field and vertical velocity, contributes to a significant enhancement of heat transport. Our findings are consistent with a scenario of drag reduction induced by polymers.

Speaker: A Mazzino

Slides pres-mazzino.pdf

14:30 → 15:00 Life at high Reynolds number

Speaker: M Jensen

15:00 → 15:30 A Lie-group mean-field theory for turbulent channel and pipe flow

Speaker: Xi Chen

Slides Frisch_fest-2011-10-19-final.pdf

16:00 → 17:00 Round table discussions

Thursday 20 October

09:30 → 10:15 Structures versus statistics in turbulence, resolution of old quarrel

Speaker: G. Falkovich

10:45 → 11:30 Turbulence in non-integer dimensions by fractal Fourier decimation

Speaker: U. Frisch

Slides stockholm-stat-mech2D-nearby.pdf

11:30 → 12:00 The tyger phenomenon for the Galerkin truncated Burgers equation.

Speaker: S.S. Ray (Obs Nice)

Slides talk_(1).pdf

12:00 → 12:30 On form and growth

Speaker: J Wettlaufer (NORDITA and Yale)

14:30 → 14:50 Inverse energy cascade in 3d isotropic and homogeneous turbulence

Speaker: L Biferale

Slides hel.pdf

Friday 21 October

09:30 → 10:15 Population dynamics in compressible flows

Speaker: R. Benzi

Slides stoccolma.pdf

10:45 → 11:15 Lagrangian/Eulerian estimate of turbulent breakup of small particles

Speaker: A. Lanotte

Slides lanotte_stokholm.pdf

11:15 → 11:45 The size of the region of analyticity of solutions to the two-dimensional Euler equation

Speaker: V. Zheligovsky