Russian Academy of Sciences

Landau Institute for Theoretical Physics

In Print

Absorption of inertial waves by columnar vortex in rotating turbulence

27 June in 11:30 (short)

N.A. Ivchenko, S.S. Vergeles

In 3D turbulent flows of a rotating system, where the Coriolis force prevails over the inertia in dynamics, formation of the columnar vortices takes place that is observed both experimentally [1] and numerically [2]. They are large-scale coherent flows that are homogeneous along the axis of rotation. Our work is about to build analytical model describing how axisymmetric vortex flow supports itself by absorbing inertial waves. We consider the following pumping mode: inertial waves reach the vortex from the periphery of system, where turbulence is excited. In the limits of short wavelengths and low viscosity we show that quasi-monochromatic wave that enters in the vortex transmits its energy and momentum only in the narrow vicinity of its critical layer [3] formed by an average shear flow. In our model we determine the Reynolds shear stress component averaged over inertial wave ensemble that sets the velocity profile of vortex [4].

[1] D.D. Tumachev, A.A. Levchenko, S.S. Vergeles, S.V. Filatov, Observation of a large stable anticyclone in rotating turbulence, PoF, 36(12), 126620 (2024).
[2] Seshasayanan, K. & Alexakis, A. Condensates in rotating turbulent flows. JFM, 841, 434–462 (2018).
[3] Haynes, P., 2015. Critical Layers. In: G. R. North et al., Encyclopedia of Atmospheric Sciences, 2nd edition, Vol 2.
[4] I.V. Kolokolov, L.L. Ogorodnikov, and S.S. Vergeles, Structure of coherent columnar vortices in three-dimensional rotating turbulent flow, Phys. Rev. Fluids 5, 034604 (2020).

Motion of neutrally buoyant particles in a turbulent fluid

20 June in 12:30 (short)

Masnev N.G.

We investigate analytically and numerically the statistical properties of the dynamics of rigid spherical particles with neutral buoyancy. The particles are placed in a turbulent flow with a strong shear component. As a simple model, we consider the shear flow of an axisymmetric vortex with turbulent fluctuations and calculate the particle distribution from the distance to the vortex center. We present quantitative results obtained within the framework of a point particle model with fluctuations that are correlated in time.

Deformation of crystallites, creep at intergranular boundaries and surface roughness enhancement of polycrystalline copper irradiated by UV nanosecond laser pulse when heated to temperatures below the melting point

18 April in 11:30

N.A. Inogamov

The mechanisms of surface relief formation on bulk copper samples under the influence of UV laser pulses (duration 10 ns, wavelength 355 nm) in the mode of heating to temperatures below the melting temperature have been investigated. It has been experimentally established that during irradiation at energy densities of 0.60-1.05 J/cm2 a characteristic system of protrusions/depressions, the height/depth of which reaches up to 500 nm, is formed on the surface of the samples in local areas near grain boundaries. By methods of optical profilometry, confocal scanning laser microscopy and transmission electron microscopy the deformation nature of the formed relief was established. The thin near-surface layer near grain boundaries shows traces of plastic deformation development: nanoscale twin plates, dislocations and low-angle dislocation boundaries. Molecular dynamic modeling has shown that the main physical reason for the development of the considered relief is the anisotropy of thermal expansion of differently oriented grains (crystallites) during cyclic heating to pre-melt temperatures. It is established that thermomechanical stresses arising in the near-surface layer exceed the yield strength of the material, which leads to irreversible plastic deformation. The amplification of structural changes is shown to increase with both the energy density and the number of pulses. The results obtained are important for understanding the mechanisms of metal structure degradation under cyclic pulse thermomechanical loading and can be used, in particular, to develop methods for increasing the operational durability of metal optics.

Неласов И.В., Манохин С.С., Колобов Ю.Р., Жаховский В.В., Перов Е.А., Петров Ю.В., Хомич Ю.В., Малинский Т.В., Иногамов Н.А., Рогалин В.Е. // ЖЭТФ. – 2025. – Т. 167. – № 6. Zhurnal Experimentalnoi i Teoreticheskoi Fiziki Vol. 167 (6) (2025).

Spatially-resolved dynamics of the amplitude Schmid-Higgs mode in disordered superconductors

21 March in 11:30

I.S. Burmistrov

We investigate the spatially-resolved dynamics of the collective amplitude Schmid-Higgs (SH) mode in disordered s-wave superconductors and fermionic superfluids. By analyzing the analytic structure of the zero-temperature SH susceptibility in the complex frequency plane, we find that when the coherence length greatly exceeds the mean free path: (i) the SH response at fixed wave vectors exhibits late-time oscillations decaying as 1/t2 with frequency 2Δ, where Δ is the superconducting gap; (ii) sub-diffusive oscillations with a dynamical exponent z=4 emerge at late times and large distances; and (iii) spatial oscillations at fixed frequency decay exponentially, with a period that diverges as the frequency approaches 2Δ from above. When the coherence length is comparable to the mean free path, additional exponentially-decaying oscillations at fixed wave vectors appear with frequency above 2Δ. Furthermore, we show that the SH mode induces an extra peak in the third-harmonic generation current at finite wave-vectors. The frequency of this peak is shifted from the conventional resonance at Δ, thereby providing an unambiguous signature of order parameter amplitude dynamics.