共查询到20条相似文献,搜索用时 17 毫秒
1.
We study numerically the interaction of four initial superfluid vortex rings in the absence of any dissipation or friction. We find evidence for a cascade of Kelvin waves generated by individual vortex reconnection events which transfers energy to higher and higher wave numbers k. After the vortex reconnections occur, the energy spectrum scales as k(-1) and the curvature spectrum becomes flat. These effects highlight the importance of Kelvin waves and reconnections in the transfer of energy within a turbulent vortex tangle. 相似文献
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In a previous communication (W.J.T. Bos and J.-P. Bertoglio 2006, Phys. Fluids, 18, 031706), a self-consistent Markovian triadic closure was presented. The detailed derivation of this closure is given here, relating it to the Direct Interaction Approximation and Quasi-Normal types of closure. The time-scale needed to obtain a self-consistent closure for both the energy spectrum and the scalar variance spectrum is determined by evaluating the correlation between the velocity and an advected displacement vector-field. The relation between this latter correlation and the velocity–scalar correlation is stressed, suggesting a simplified model of the latter. The resulting closed equations are numerically integrated and results for the energy spectrum, scalar fluctuation spectrum and velocity–displacement correlation spectrum are presented for low, unity and high values of the Schmidt number. 相似文献
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Cobelli P Przadka A Petitjeans P Lagubeau G Pagneux V Maurel A 《Physical review letters》2011,107(21):214503
We present an experimental study on gravity capillary wave turbulence in water. By using space-time resolved Fourier transform profilometry, the behavior of the wave energy density |η(k,ω)|(2) in the 3D (k,ω) space is inspected for various forcing frequency bandwidths and forcing amplitudes. Depending on the bandwidth, the gravity spectral slope is found to be either forcing dependent, as classically observed in laboratory experiments, or forcing independent. In the latter case, the wave spectrum is consistent with the Zakharov-Filonenko cascade predicted within wave turbulence theory. 相似文献
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A. V. Chechkin M. I. Kopp V. V. Yanovsky A. V. Tur 《Journal of Experimental and Theoretical Physics》1998,86(2):357-366
The possible occurrence of a “negative viscosity effect” is studied for Rossby wave and drift wave turbulence. It is assumed
that (i) the space and time scales of the wave field are much smaller than the scales of the mean field, and (ii) the small-scale
field is sufficiently weak, stationary, and maintained by an external source. Such a formulation is fruitful for studying
the effects (characterized by the effective viscosity) of smaller-scale motions upon larger-scale ones. The criteria of large-scale
instability due to the negative effective viscosity are derived for the coherent wave motions as well as for small-scale isotropic
wave turbulence.
Zh. éksp. Teor. Fiz. 113, 646–663 (February 1998)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor. 相似文献
7.
We present a phenomenological model for 2D turbulence in which the energy spectrum obeys a nonlinear fourth-order differential
equation. This equation respects the scaling properties of the original Navier-Stokes equations, and it has both the −5/3
inverse-cascade and the −3 direct-cascade spectra. In addition, our model has Raleigh-Jeans thermodynamic distributions as
exact steady state solutions. We use the model to derive a relation between the direct-cascade and the inverse-cascade Kolmogorov
constants, which is in good qualitative agreement with the laboratory and numerical experiments. We discuss a steady state
solution where both the enstrophy and the energy cascades are present simultaneously, and we discuss it in the context of
the Nastrom-Gage spectrum observed in atmospheric turbulence. We also consider the effect of the bottom friction on the cascade
solutions and show that it leads to an additional decrease and finite-wavenumber cutoffs of the respective cascade spectra,
which agrees with the existing experimental and numerical results.
The text was submitted by the authors in English. 相似文献
8.
Angle-of-arrival fluctuations for wave propagation through non-Kolmogorov turbulence 总被引:1,自引:0,他引:1
Recently the increasing experimental evidences have shown that atmospheric turbulence statistics does not obey Kolmogorov’s power spectrum model in portions of the troposphere and stratosphere. These experiments have prompted the investigations of optical wave propagation through atmospheric turbulence described by non-classical power spectra. In this paper, using an original approach and considering a non-Kolmogorov power spectrum which uses a generalized power law instead of constant standard power law value 11/3 and a generalized amplitude factor instead of constant value 0.033, the variances of the angle-of-arrival fluctuations of the plane and spherical waves are derived in weak turbulence for a horizontal path. The concise closed-form expressions are obtained and used to analyze the influence of spectral power law variation on the angle-of-arrival fluctuations. 相似文献
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We report the observation of the crossover between gravity and capillary wave turbulence on the surface of mercury. The probability density functions of the turbulent wave height are found to be asymmetric and thus non-Gaussian. The surface wave height displays power-law spectra in both regimes. In the capillary region, the exponent is in fair agreement with weak turbulence theory. In the gravity region, it depends on the forcing parameters. This can be related to the finite size of the container. In addition, the scaling of those spectra with the mean energy flux is found in disagreement with weak turbulence theory for both regimes. 相似文献
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Jordan R Josserand C 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(2):1527-1539
We present a statistical equilibrium model of self-organization in a class of focusing, nonintegrable nonlinear Schrodinger (NLS) equations. The theory predicts that the asymptotic-time behavior of the NLS system is characterized by the formation and persistence of a large-scale coherent solitary wave, which minimizes the Hamiltonian given the conserved particle number (L2-norm squared), coupled with small-scale random fluctuations, or radiation. The fluctuations account for the difference between the conserved value of the Hamiltonian and the Hamiltonian of the coherent state. The predictions of the statistical theory are tested against the results of direct numerical simulations of NLS, and excellent qualitative and quantitative agreement is demonstrated. In addition, a careful inspection of the numerical simulations reveals interesting features of the transitory dynamics leading up to the long-time statistical equilibrium state starting from a given initial condition. As time increases, the system investigates smaller and smaller scales, and it appears that at a given intermediate time after the coalescense of the soliton structures has ended, the system is nearly in statistical equilibrium over the modes that it has investigated up to that time. 相似文献
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E. Kartashova 《JETP Letters》2006,83(7):283-287
A model of laminated wave turbulence is presented. This model consists of two coexisting layers—one with continuous wave spectra,
covered by KAM theory and Kolmogorov-like power spectra, and one with discrete wave spectra, covered by discrete classes of
waves and the Clipping method. Some known laboratory experiments and numerical simulations are explained in the frame of this
model.
The text was submitted by the author in English. 相似文献
13.
Darryl D. Holm 《Physics letters. A》1985,108(9):445-447
A hamiltonian formulation using a noncanonical Poisson bracket is presented for a nonlinear fluid system that includes reduced magnetohydrodynamics and the Hasegawa-Mima equation as limiting cases. Nonlinear integral invariants for the system are found to be in the kernel of the noncanonical Poisson bracket. This Poisson bracket is given a Lie algebraic interpretation. 相似文献
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D.P. Dewangan 《Physics letters. A》1977,62(5):303-306
By treating the static field of the atom exactly and using the eikonal wavefunction to bring in the couplings to all remaining atomic states, a simple formula for elastic scattering amplitude is derived. Its usefulness is demonstrated by applying it to electron—hydrogen scattering. 相似文献
16.
The differential elastic scattering cross-sections of intermediate energy antiprotons from Carbon and Aluminum have been analysed to determine parameter values of analytic representations of the optical model, distorted waves; such representations being convenient for use in analyses of non elastic reaction data. 相似文献
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We report the observation of intermittency in gravity-capillary wave turbulence on the surface of mercury. We measure the temporal fluctuations of surface wave amplitude at a given location. We show that the shape of the probability density function of the local slope increments of the surface waves strongly changes across the time scales. The related structure functions and the flatness are found to be power laws of the time scale on more than one decade. The exponents of these power laws increase nonlinearly with the order of the structure function. All these observations show the intermittent nature of the increments of the local slope in wave turbulence. We discuss the possible origin of this intermittency. 相似文献
19.
We derive a simple expression, which gives an approximate value of the Rayleigh wave velocity in an isotropic solid. This approximation is five times better than that given by Viktorov. The velocity equation can be easily inverted in order to obtain an accurate determination of the elastic constants. This procedure can be worthwhile for elastic microanalysis of bulk materials by scanning acoustic microscopy. 相似文献
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The turbulence inner scale plays an important role in investigating the irradiance scintillation index for optical wave propagating through atmospheric turbulence. However, previous expressions of the irradiance scintillation index, which were derived based on the general non-Kolmogorov spectral model, did not consider the influences of finite turbulence inner scale. In this study, based on the generalized exponential spectral model for non-Kolmogorov atmospheric turbulence, theoretical expressions of the irradiance scintillation index are derived for plane and spherical optical waves propagating through weak turbulence. The new expressions have considered the influences of the finite turbulence inner scale and the receiver aperture on the irradiance scintillation index. Numerical simulations are performed to analyze these parameters’ influences. 相似文献