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Of all publications in the section: 11
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Article
Vulfson A., Borodin O. Physics of Fluids. 2018. Vol. 30. No. 9. P. 095103-1-095103-10.

The stochastic ensemble of convective thermals (vortices), forming the fine structure of a turbulent convective atmospheric layer, is considered. The proposed ensemble model assumes all thermals in the mixed-layer to have the same determinate buoyancies and considers them as solid spheres of variable volumes. The values of radii and vertical velocities of the thermals are assumed random. The motion of the stochastic system of convective vortices is described by the nonlinear Langevin equation with a linear drift coefficient and a random force, whose structure is known for a system of Brownian particles. The probability density of the thermal ensemble in velocity phase space is shown to satisfy an associated K-form of the Fokker-Planck equation with variable coefficients. Maxwell velocity distribution of convective thermals is constructed as a steady-state solution of a simplified Fokker- Planck equation. The obtained Maxwell velocity distribution is shown to give a good approximation of experimental distributions in a turbulent convective mixed-layer.

Added: Oct 30, 2018
Article
Kolokolov I., Lebedev V., Doludenko A. et al. 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.

Added: Jan 20, 2021
Article
Ivanov S., Kamchatnov A.M. Physics of Fluids. 2019. Vol. 31.

We consider evolution of wave pulses with formation of dispersive shock waves in framework of fully nonlinear shallow-water equations. Situations of initial elevations or initial dips on the water surface are treated, and motion of the dispersive shock edges is studied within the Whitham theory of modulations. Simple analytical formulas are obtained for asymptotic stage of evolution of initially localized pulses. Analytical results are confirmed by exact numerical solutions of the fully nonlinear shallow-water equations.

Added: Feb 4, 2021
Article
Kamchatnov Anatoly M., Ivanov S. K. Physics of Fluids. 2020. Vol. 32.

The nonlinear dynamics of pulses in a two-temperature collisionless plasma with the formation of dispersion shock waves is studied. An analytical description is given for an arbitrary form of an initial disturbance with a smooth enough density profile on a uniform density background. For large time after the wave breaking moment, dispersive shock waves are formed. Motion of their edges is studied in the framework of Gurevich–Pitaevskii theory and Whitham theory of modulations. The analytical results are compared with the numerical solution.

Added: Feb 4, 2021
Article
O.E. Kurkina, A.A. Kurkin, T. Soomere et al. Physics of Fluids. 2011. Vol. 23. No. 11. P. 116602-1-13-116602-13.

We address a specific but possible situation in natural water bodies when the three-layer stratification has a symmetric nature, with equal depths of the uppermost and the lowermost layers. In such case, the coefficients at the leading nonlinear terms of the modified Korteweg-de Vries (mKdV) equation vanish simultaneously. It is shown that in such cases there exists a specific balance between the leading nonlinear and dispersive terms. An extension to the mKdV equation is derived by means of combination of a sequence of asymptotic methods. The resulting equation contains a cubic and a quintic nonlinearity of the same magnitude and possesses solitary wave solutions of different polarity. The properties of smaller solutions resemble those for the solutions of the mKdV equation whereas the height of the taller solutions is limited and they become table-like. It is demonstrated numerically that the collisions of solitary wave solutions to the resulting equation are weakly inelastic: the basic properties of the counterparts experience very limited changes but the interactions are certainly accompanied by a certain level of radiation of small-amplitude waves.

Added: Nov 6, 2012
Article
Осипов А., Уваров А., Vinnichenko N. A. Physics of Fluids. 2006. Vol. 18. No. 10. P. 105-106.
Added: Oct 30, 2010
Article
Pelinovsky E., Maderich V., Талипова Т. Г. et al. Physics of Fluids. 2010. No. 22. P. 076602.
Added: Feb 20, 2011
Article
Pelinovsky E., Talipova T., Terletska K. et al. Physics of Fluids. 2013. No. 25. P. 032110.

Internal solitary wave transformation over the bottom step: loss of energy.

Added: Nov 23, 2013
Article
Klein M., Clauss G., Slunyaev A. Physics of Fluids. 2017. Vol. 29. P. 047103-1-047103-17.

The investigation of dynamics of intense solitary wave groups of collinear surface waves is performed by means of numerical simulations of the Euler equations and laboratory experiments. The processes of solitary wave generation, reflection from a wall and collisions are considered. Steep solitary wave groups with characteristic steepness up to kAcr ~ 0.3 (where k is the dominant wavenumber, and Acr is the crest amplitude) are concerned. They approximately restore the structure after the interactions. In the course of the interaction with the wall and collisions the maximum amplitude of the wave crests is shown to enhance up to 2.5 times. A standing-wave-like structure occurs in the vicinity of the wall, with certain locations of nodes and antinodes regardless the particular phase of the reflecting wave group. A strong asymmetry of the maximal wave groups due to an anomalous set-up is shown in situations of collisions of solitons with different frequencies of the carrier. In some situations of head-on collisions the amplitude of the highest wave is larger than in overtaking collisions of the same solitons. The discovered effects in interactions of intense wave groups are important in the context of mechanisms and manifestations of oceanic rogue waves.

Added: Feb 14, 2019
Article
Ilyin A., Kopyev A., Sirota V. 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 velocity shows that, for wide range of parameters, stationarity without feedback would take place even in the case of intensive pumping of magnetic field.

Added: Dec 16, 2020
Article
Kolokolov I., Lebedev V., Chertkov M. Physics of Fluids. 2007. Vol. 19. P. 101703-1-101703-4.
Passive scalar turbulence forced steadily is characterized by the velocity correlation scale L, injection scale l, and diffusive scale rd. The scales are well separated if the diffusivity is small, rdl ,L, and one normally says that effects of diffusion are confined to smaller scales, rrd. However, if the velocity is single scale, one finds that a weak dependence of the scalar correlations on the molecular diffusivity persists to even larger scales, e.g., lrrd (E. Balkovsky et al., Pis’ma Zh. Eksp. Teor. Fiz. 61, 1012 1995 JETP Lett. 61, 1049 1995). We consider the case of L l and report a counterintuitive result, namely the emergence of a new range of large scales, L rl2 / rd, where the diffusivity shows a strong effect on scalar correlations.
Added: Feb 10, 2017