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## Coherent vortex in a spatially restricted two-dimensional turbulent flow in absence of bottom friction.

Physics of Fluids. 2021. Vol. 33. No. 011704. P. 1-6.

We investigate the coherent vortex produced by two-dimensional turbulence excited in a finite box. We establish analytically the mean velocity

profile of the vortex for the case where the bottom friction is negligible and express its characteristics via the parameters of pumping. Our

theoretical predictions are verified and confirmed by direct numerical simulations in the framework of two-dimensional weakly compressible

hydrodynamics with zero boundary conditions.

I.V.Kolokolov, V.V. Lebedev, JETP Letters 2015 Vol. 101 No. 3 P. 181-184

The inverse cascade of two-dimensional turbulence in a restricted domain leads to creating a coherent flow containing a number of system-size vortices. We examine the case of forcing turbulence with zero bottom friction where the final statistically steady state is determined by viscosity. We analytically establish structure of the coherent vortices in the state. ...

Added: October 15, 2016

I.V.Kolokolov, V.V.Lebedev, Journal of Fluid Mechanics 2016 Vol. 809 No. paper R2 P. 1-11

We analyze velocity fluctuations inside coherent vortices generated as a result of the inverse cascade in the two-dimensional ($2d$) turbulence in a finite box. As we demonstrated in \citep{16KL}, the universal velocity profile, established in \citep{14LBFKL}, corresponds to the passive regime of the flow fluctuations. The property enables one to calculate correlation functions of the ...

Added: October 23, 2016

Laurie J., Boffetta G., Falkovich G. et al., Physical Review Letters 2014 Vol. 113 No. 25 P. 254503-1-254503-5

An inverse turbulent cascade in a restricted two-dimensional periodic domain creates a condensate-a pair of coherent system-size vortices. We perform extensive numerical simulations of this system and carry out theoretical analysis based on momentum and energy exchanges between the turbulence and the vortices. We show that the vortices have a universal internal structure independent of ...

Added: October 15, 2016

Kolokolov I., Lebedev V., Письма в Журнал экспериментальной и теоретической физики 2017 Т. 106 № 10 С. 633-636

Two dimensional turbulence has the striking tendency to self-organize into large-scale, coherent structures due to the inverse energy cascade \cite{67Kra,68Lei,69Bat}. Here we theoretically examine the case of a static pumping where the exciting force is independent of time, the case corresponds to the experimental setup of the works . We establish dependence of the large-scale ...

Added: November 12, 2017

I.V.Kolokolov, V.V. Lebedev, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2016 Vol. 93 No. 3 P. 033104-1-033104-7

We discuss the structure and geometrical characteristics of coherent vortices appearing as a result of the inverse cascade in two-dimensional turbulence in a finite box.We demonstrate that the universal velocity profile, established by J. Laurie et al. [Phys. Rev. Lett. 113, 254503 (2014)], corresponds to the passive regime of flow fluctuations.We find the vortex core ...

Added: October 15, 2016

Kolokolov I., Lebedev V., Chertkov M., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2010 Vol. 81 P. 015302R

Two-dimensional turbulence generated in a finite box produces large-scale coherent vortices coexisting with
small-scale fluctuations. We present a rigorous theory explaining the =1/4 scaling in the Vr− law of the
velocity spatial profile within a vortex, where r is the distance from the vortex center. This scaling, consistent
with earlier numerical and laboratory measurements, is universal in ...

Added: February 7, 2017

Slunyaev A., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2020 Vol. 101 Article 062214

A method of windowed spatiotemporal spectral filtering is proposed to segregate different nonlinear wave components and to calculate the surface of free waves. The dynamic kurtosis (i.e., produced by the free wave component) is shown able to contribute essentially to the abnormally large values of the surface displacement kurtosis, according to the direct numerical simulations of realistic sea ...

Added: June 28, 2020

Ilyin A., Kopyev A. V., Sirota V. A. et al., Physics of Fluids 2020 Vol. 32 No. 12 P. 125114

We consider fluctuations of magnetic field excited by external force and advected by isotropic turbulent flow. It appears that non-Gaussian velocity gradient statistics and finite region of pumping force provide the existence of stationary solution. The mean-square magnetic field is calculated for arbitrary velocity gradient statistics. An estimate for possible feedback of magnetic field on ...

Added: December 16, 2020

Kolokolov I., Lebedev V., Chertkov M. et al., Physical Review Letters 2007 Vol. 99 P. 084501-1-084501-4

We report a numerical study, supplemented by phenomenological explanations, of ‘‘energy condensation’’
in forced 2D turbulence in a biperiodic box. Condensation is a finite size effect which occurs after
the standard inverse cascade reaches the size of the system. It leads to the emergence of a coherent vortex
dipole. We show that the time growth of the dipole ...

Added: February 10, 2017

Бузовкин А. Б., Kolokolov I., Lebedev V. et al., JETP Letters (английский перевод Писем в Журнал экспериментальной и теоретической физики) 2020 Vol. 111 No. 8 P. 442-446

We consider the structure of a coherent vortex formed around a solid rotating disc in two-dimensional turbulent flow. We find the average velocity profile of the coherent vortex for different rotation velocities ...

Added: July 15, 2020

Parfenyev V., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2022 Vol. 106 No. 2 Article 025102

It is well known that an inverse turbulent cascade in a finite ($2 \pi \times 2 \pi$) two-dimensional periodic domain leads to the emergence of a system-sized coherent vortex dipole. We report a numerical hyperviscous study of the spatial vorticity profile inside one of the vortices. The exciting force was shortly correlated in time, random ...

Added: August 10, 2022

Ilyin A., Zybin K., Сирота В. А., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2017 Vol. 96 P. 013117-1-013117-8

WeanalyzepassivescalaradvectionbyaturbulentﬂowintheBatchelorregime.Norestrictionsonthevelocity statistics of the ﬂow are assumed. The properties of the scalar are derived from the statistical properties of velocity; analytic expressions for the moments of scalar density are obtained. We show that the scalar statistics can differ signiﬁcantly from that obtained in the frames of the Kraichnan model. ...

Added: October 30, 2019

A. S. Il'yn, Kopyev A. V., Sirota V. A. et al., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2023 Vol. 107 No. 2 Article L023101

We consider the line, surface, and volume elements of fluid in stationary isotropic incompressible stochastic flow in d-dimensional space and investigate the long-time evolution of their statistic properties. We report the discovery of a family of d!−1 stochastical integrals of motion that are universal in the sense that their explicit form does not depend on the statistics of ...

Added: February 23, 2023

Ilyin A., Zybin K., Сирота В. А., EPL 2018 Vol. 121 P. 34002-p1-34002-p6

Statistical moments of magnetic ﬁeld in a viscous range of turbulence are calculated for arbitrary initial conditions. It is shown that the evolution of magnetic ﬁeld in the case of ﬁnite initial distribution in a linear velocity ﬁeld consists of two or three consecutive regimes: exponential growth is followed by exponential decay. This solves the ...

Added: October 30, 2019

Ilyin A., Zybin K., Сирота В. А., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2019 Vol. 99 No. 5 P. 052220-1-052220-6

The impact of turbulent advection in reaction-diffusion systems is investigated for the viscous range of scales. We show that the population size can increase exponentially even in systems with density saturation, at the expense of exponential propagation of the reaction front. Exact expressions for scaling exponents of the density and population size are calculated in ...

Added: October 30, 2019

Nikolay A. Ivchenko, Vergeles S. S., Physics of Fluids 2021 Vol. 33 No. 10 Article 105102

A condensate in two-dimensional turbulence confined to a finite domain was predicted by Kraichnan. The most common spatial form of the condensate is a coherent vortex of radius comparable with the domain size, which is statistically steady over times much longer than its turnover time. The vortices were successively studied during the last four decades, ...

Added: October 14, 2021

I. V. Kolokolov, V. V. Lebedev, M. M. Tumakova, JETP Letters 2023 Vol. 117 No. 2 P. 122-125

We study the correlations of vorticity fluctuations inside a coherent vortex resulting from the inverse energy
cascade in two-dimensional turbulence. The presence of a coherent flow, which is a differential rotation, suppresses small-scale fluctuations of the flow, which are created by an external force, and lead to the fact that
these fluctuations can be considered as non-interacting ...

Added: February 19, 2023

I. V. Kolokolov, V. V. Lebedev, Tumakova M. M., Journal of Experimental and Theoretical Physics 2023 Vol. 136 No. 6 P. 785-794

We investigate fluctuations of vorticity inside a coherent vortex generated by the inverse energy cascade in two-dimensional turbulence. Temporal and spatial correlations can be characterized by the pair correlation function. The interaction of fluctuations leads to a nonzero third moment of vorticity. We analyze the
pair correlation function and the third moment using a model in ...

Added: June 8, 2023

Kolokolov I., Lebedev V., Parfenyev V., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2024 Vol. 109 No. 3 Article 035103

We analytically examine fluctuations of vorticity excited by an external random force in two-dimensional fluid. We develop the perturbation theory enabling one to calculate nonlinear corrections to correlation functions of the flow fluctuations found in the linear approximation. We calculate the correction to the pair correlation function and the triple correlation function. It enables us ...

Added: March 25, 2024

Zybin K., Ilyin A., Сирота В. А. et al., EPL 2020 Vol. 132 P. 24001

Evolution of a stochastically homogeneous magnetic field advected by an incompressible turbulent flow with large magnetic Prandtl numbers is considered at scales smaller than the Kolmogorov viscous scale. It is shown that, despite the unlimited growth of the magnetic field, its feedback on the fluid's dynamics remains negligibly small. ...

Added: December 23, 2020

Kolokolov I., Lebedev V., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2020 Vol. 102 No. 2 P. 1-5

We examine coherent vortices appearing as a result of the inverse cascade of two-dimensional turbulence in a
finite box in the case of pumping with arbitrary correlation time in the quasilinear regime. We demonstrate that
the existence of the vortices depends on the ratio between the values of the bottom friction coefficient α and the
viscous damping of ...

Added: October 6, 2020

Kolokolov I., Kostenko M., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2020 Vol. 101 No. 033108 P. 1-3

We consider two-dimensional turbulence in the presence of a condensate. The nondiagonal correlation
functions of the Lagrangian accelerations are calculated, and it is shown that they have the same universality
properties as the nondiagonal correlation functions of the velocity fluctuations. ...

Added: March 25, 2020

Doludenko A. N., Fortova S. V., Kolokolov I. et al., Annals of Physics 2022 Vol. 447 No. Pt. 2 Article 169072

We examine analytically and numerically the state of a two-dimensional fluid in a finite box appearing as a result of the inverse cascade supported by a permanent pumping. We argue that there are two different states. One of the states is dominated by big coherent vortices with a well-defined mean profile. The other state is ...

Added: December 10, 2022

Ilyin A., Kopyev A. V., Sirota V. A. et al., Physics of Fluids 2021 Vol. 33 No. 7 P. 075105-1-075105-10

Kinematic dynamo in incompressible isotropic turbulent flows with high magnetic Prandtl number is considered. The approach interpreting an arbitrary magnetic field distribution as a superposition of localized perturbations (blobs) is developed. We derive a general relation between stochastic properties of an isolated blob and a stochastically homogenous distribution of magnetic field advected by the same ...

Added: July 20, 2021