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A phenomenological two-fluid model of the (time-reversible) spectrally-truncated 3D Euler equation is proposed. The thermalized small scales are first shown to be quasi-normal. The effective viscosity and thermal diffusion are then determined, using EDQNM closure and Monte-Carlo numerical computations. Finally, the model is validated by comparing its… (More)

- G Krstulovic, P D Mininni, M E Brachet, A Pouquet
- Physical review. E, Statistical, nonlinear, and…
- 2009

The dynamics of the truncated Euler equations with helical initial conditions are studied. Transient energy and helicity cascades leading to Kraichnan helical absolute equilibrium at small scales, including a linear scaling of the relative helicity spectrum are obtained. Strong helicity effects are found using initial data concentrated at high wave numbers.… (More)

- G. Krstulovic, J. Bec
- 2013

A dilute system of reacting particles transported by fluid flows is considered. The particles react as A + A → ∅ with a given rate when they are within a finite radius of interaction. The system is described in terms of the joint n-point number spatial density that it is shown to obey a hierarchy of transport equations. An analytic solution is obtained in… (More)

- J D Gibbon, A Gupta, +6 authors J Stawarz
- Physical review. E
- 2016

It is shown how suitably scaled, order-m moments, D_{m}^{±}, of the Elsässer vorticity fields in three-dimensional magnetohydrodynamics (MHD) can be used to identify three possible regimes for solutions of the MHD equations with magnetic Prandtl number P_{M}=1. These vorticity fields are defined by ω^{±}=curlz^{±}=ω±j, where z^{±} are Elsässer variables,… (More)

- Giorgio Krstulovic, Marc Brachet
- Physical review. E, Statistical, nonlinear, and…
- 2011

The statistical equilibria of the (conservative) dynamics of the Gross-Pitaevskii equation (GPE) with a finite range of spatial Fourier modes are characterized using a new algorithm, based on a stochastically forced Ginzburg-Landau equation (SGLE), that directly generates grand-canonical distributions. The SGLE-generated distributions are validated against… (More)

- Giorgio Krstulovic, Marc Brachet, Enrique Tirapegui
- Physical review. E, Statistical, nonlinear, and…
- 2008

Sound emission produced by the interaction of several vortices in a two-dimensional homogeneous system obeying the nonlinear Schrödinger (NLS) equation is considered. The radiation effect is explicitly computed in terms of assumed vortex motion. The results are applied to a simple test case of two corotating vortices. The prediction is compared to the… (More)

- Giorgio Krstulovic, Marc Brachet
- Physical review letters
- 2011

A new mechanism of thermalization involving a direct energy cascade is obtained in the truncated Gross-Pitaevskii dynamics. A long transient with partial thermalization at small scales is observed before the system reaches equilibrium. Vortices are found to disappear as a prelude to final thermalization. A bottleneck that produces spontaneous effective… (More)

- Giorgio Krstulovic, Marc-Etienne Brachet, Annick Pouquet
- Physical review. E, Statistical, nonlinear, and…
- 2011

We investigate numerically the dynamics of two-dimensional Euler and ideal magnetohydrodynamics (MHD) flows in systems with a finite number of modes, up to 4096(2), for which several quadratic invariants are preserved by the truncation and the statistical equilibria are known. Initial conditions are the Orszag-Tang vortex with a neutral X point centered on… (More)

- Giorgio Krstulovic, Carlos Cartes, Marc Brachet, Enrique Tirapegui
- I. J. Bifurcation and Chaos
- 2009

A short review is given of recent papers on the relaxation to (incompressible) absolute equilibrium. A new algorithm to construct absolute equilibrium of spectrally truncated compressible flows is described. The algorithm uses stochastic processes based on the Clebsch representation of the velocity field to generate density and velocity fields that follow… (More)