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

Name: The Solar Course, the Chemic Force, and the Speeding Change of Water
Start: 2011-10-17T08:00:00+02:00
End: 2011-10-21T18:00:00+02:00
Location: NORDITA

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

Nordita lecture room (NORDITA)

Nordita lecture room

NORDITA

Roslagstullsbacken 23

Dhrubaditya Mitra (Asssitant Professor)

Description

→ 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
- 1
  
  Turbulent convection in three, two and one dimensions.
  
  Speaker: G Boffetta
  
  Slides
  
  video
- 2
  
  Energy and enstrophy cascades in large scale atmospheric turbulence
  
  Speaker: E. Lindborg
  
  Slides
  
  video
- 3
  
  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
  
  video
- 4
  
  Computing non-equilibrium stationary states by message-passing?
  
  Speaker: E. Aurell
  
  video
- 5
  
  Rotating Turbulence and return to isotropy.
  
  Speaker: A. Pouquet
  
  Slides
  
  video
- 6
  
  Dynamics of the glassy state of matter
  
  Speaker: I. Procaccia
  
  video
- 7
  
  Pirouette effect in turbulence
  
  Speaker: A. Pumir
  
  video
- 8
  
  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
  
  video
Tuesday 18 October
- 9
  
  Optimization in astrophysics
  
  Speaker: R. Mohayee (AIP, Paris)
- 10
  
  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
- 11
  
  Nelkin scaling for ¨burgulence¨
  
  Speaker: S. Chakraborty (NBI, Copenhagen)
  
  Slides
- 12
  
  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
- 13
  
  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
- 14
  
  On the Evolution of Texts: An Introduction to Stemmatology
  
  Speaker: T Roos
  
  Slides
- 15
  
  Nothing new under the burning sun? Climate and verbs in North-West Semitic
  
  Speaker: O. Wikander
Wednesday 19 October
- 16
  
  Time Scales, Persistence, and Dynamic Multiscaling in Turbulence
  
  Speaker: R. Pandit (IISc, Bangalore)
  
  Slides
- 17
  
  Orientation of non-symmetric particles in axisymmetric random flows
  
  Speaker: D. Vincenzi
  
  Slides
- 18
  
  Navier-Stokes in hyperbolic plane
  
  Speaker: ENS, Lyon Gawedzki
  
  Slides
- 19
  
  Axial dipolar dynamo action in Taylor-Green vortex
  
  Speaker: M-E Brachet
  
  Slides
- 20
  
  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
- 21
  
  Life at high Reynolds number
  
  Speaker: M Jensen
- 22
  
  A Lie-group mean-field theory for turbulent channel and pipe flow
  
  Speaker: Xi Chen
  
  Slides
- 23
  
  Round table discussions
Thursday 20 October
- 24
  
  Structures versus statistics in turbulence, resolution of old quarrel
  
  Speaker: G. Falkovich
- 25
  
  Turbulence in non-integer dimensions by fractal Fourier decimation
  
  Speaker: U. Frisch
  
  Slides
- 26
  
  The tyger phenomenon for the Galerkin truncated Burgers equation.
  
  Speaker: S.S. Ray (Obs Nice)
  
  Slides
- 27
  
  On form and growth
  
  Speaker: J Wettlaufer (NORDITA and Yale)
- 28
  
  Inverse energy cascade in 3d isotropic and homogeneous turbulence
  
  Speaker: L Biferale
  
  Slides
Friday 21 October
- 29
  
  Population dynamics in compressible flows
  
  Speaker: R. Benzi
  
  Slides
- 30
  
  Lagrangian/Eulerian estimate of turbulent breakup of small particles
  
  Speaker: A. Lanotte
  
  Slides
- 31
  
  The size of the region of analyticity of solutions to the two-dimensional Euler equation
  
  Speaker: V. Zheligovsky