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1.
Izvestiya, Atmospheric and Oceanic Physics - This paper investigates the stability of a jet flow with a piecewise linear velocity profile in a rotating stratified atmosphere. The linearized set of... 相似文献
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The nonlinear dynamics of long-wave perturbations of the inviscid Kolmogorov flow, which models periodically varying in the horizontal direction oceanic currents, is studied. To describe this dynamics, the Galerkin method with basis functions representing the first three terms in the expansion of spatially periodic perturbations in the trigonometric series is used. The orthogonality conditions for these functions formulate a nonlinear system of partial differential equations for the expansion coefficients. Based on the asymptotic solutions of this system, a linear, quasilinear, and nonlinear stage of perturbation dynamics is identified. It is shown that the time-dependent growth of perturbations during the first two stages is succeeded by the stage of stable nonlinear oscillations. The corresponding oscillations are described by the oscillator equation containing a cubic nonlinearity, which is integrated in terms of elliptic functions. An analytical formula for the period of oscillations is obtained, which determines its dependence on the amplitude of the initial perturbation. Structural features of the field of the stream function of the perturbed flow are described, associated with the formation of closed vortex cells and meandering flow between them. As a supplement, an asymptotic analysis of nonlinear dynamics of long-wave perturbations superimposed on a damped by small viscosity Kolmogorov flow (very large, but finite Reynolds numbers) is made. It is strictly shown that all velocity components of the perturbed flow remain bounded in this case. 相似文献
3.
Geodynamic aspects of the development of offshore oil and gas deposits: Case study of Barents region
Geodynamic aspects of the development of offshore deposits in the Russian sector of Barents region are considered. The main
technogenic geohazards at oil hydrocarbon extraction are shown to be land subsidence and earthquakes. A concept of studying
geodynamic manifestations is substantiated. This concept is based on the evolution of oil-and-gas-producing enterprise with
appropriate portion of geological environment, regarded as a complex open natural-engineering system. The geodynamic situation
at the Shtokman gas-condensate field was simulated using a mathematical model. The model showed some regularities in the deformation
of the fluid-bearing massif because of gas extraction, including the up to 30% volumetric compaction of the production strata,
resulting in a regression deflection (subsidence) of seabed and considerable subhorizontal deformations and displacements
of bottom rock beds. The specific features of gas pipeline laying from the Shtokman field through Murmansk province are discussed,
and the structure of geodynamic monitoring is proposed. Substantiation is given to the need to carry out special geodynamic
studies in the Barents region with the aim to ensure operation geosafety and stability of structures of oil-and-gas facilities
and pipeline transportation of hydrocarbons materials. 相似文献
4.
M. V. Kalashnik O. G. Chkhetiani G. D. Chagelishvili 《Izvestiya Atmospheric and Oceanic Physics》2018,54(4):305-312
Edge baroclinic waves are generated in a geostrophic flow with a vertical shear near a solid surface. The study investigates a new class of baroclinic waves in flows with horizontal and vertical shears and a linear distribution of potential vorticity. It is shown that taking account of the horizontal shear leads to the appearance of new features of wave dynamics. These include the nonmodal growth of energy in the initial stage of development, the time dependence of the vertical wave scale, and the possibility of generation of stationary or blocked waves. The horizontal shear makes the mechanism of generation of baroclinic waves by initial vortex perturbations more efficient. One important feature is associated with vortex paths, which are formed by the superposition of a baroclinic wave on the flow with horizontal shear. 相似文献
5.
The problem of finding optimal perturbations, which are perturbations with a maximum ratio of the final energy to the initial energy, is considered in the Eady model of baroclinic instability. The solution to the problem uses explicit expressions for the energy functional, which are functions of parameters of an initial perturbation. For perturbations with zero potential vorticity, the basic parameters are the amplitudes of the initial buoyancy distributions at the boundaries of the atmospheric layer and a phase shift between these distributions. Dependences of the optimal phase shift and maximum energy ratio on the wave number and time optimization are determined using an analysis for extremum. The parameters of the optimal perturbations are compared with those of the growing normal modes. It is found that only one exponentially growing mode is an optimal perturbation. 相似文献
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7.
M. V. Kalashnik A. F. Nerushev R. V. Ivangorodsky 《Izvestiya Atmospheric and Oceanic Physics》2017,53(2):156-163
Wind-speed distributions in atmospheric upper air jet streams have a horizontal asymmetry: the wind shear on the northern (cyclonic) side of the jet is larger than that on the southern (anticyclonic) side. The paper suggests an explanation of this feature on the basis of the theory of nonlinear geostrophic adjustment. Simple theoretical estimates are obtained for the asymmetry coefficient of the speed profile. It is shown that the asymmetry increases with the Rossby number (with a jet-stream velocity). Results of the statistical analysis of the horizontal asymmetry of jet streams from Earth’s satellite measurements are described. 相似文献
8.
The linear problem of geostrophic adjustment in a rotating stratified medium is generalized to the case of binary mixtures stratified with respect to both the temperature and admixture concentration (such as, for example, saline seawater and humid air). It is shown that, if the initial ageostrophicity is related to the temperature and/or admixture concentration disturbances, the evolution of the fields of these substances may qualitatively differ from the classical solutions of the adjustment problems. For example, in the course of adjustment, jumps in the temperature and salinity may be retained and enhanced, in contrast to those in the velocity, pressure, and buoyancy. The latter are smoothed by the adjustment process and are distributed over relatively spacious areas with horizontal sizes of the order of the Rossby scale. The initial thermal pulse may lead to the development of a temperature disturbance with a significantly greater amplitude and/or opposite sign and to an intensive disturbance in the admixture concentration. 相似文献
9.
The linear hydrodynamic instability of the spatially periodic system of updrafts and downdrafts in a stably stratified atmosphere is studied. Such formulation of the problem is used to simulate the cloud systems observed in the atmosphere, when the zones of updrafts correspond to clouds and those of downdrafts correspond to intercloud intervals. A rather unexpected conclusion was made that the consideration of turbulent viscosity and thermal conductivity of the atmosphere as well as of radiative cooling leads to the instability at the Richardson numbers exceeding the critical value of 1/8 for the nondissipative case. 相似文献
10.
O. G. Chkhetiani M. V. Kalashnik L. Kh. Ingel’ 《Izvestiya Atmospheric and Oceanic Physics》2013,49(2):121-127
The problem of stationary convective flows over a nonuniformly heated wavy surface is studied in the context of a simplified analytical model. It is shown that the horizontally periodic heating of such a surface can lead to a “thermal wind” effect, i.e., the generation of a uniform horizontal flow far from the surface. 相似文献