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91.
We consider the Navier–Stokes equation on a two-dimensional torus with a random force, white noise in time, and analytic in space, for arbitrary Reynolds number R. We prove probabilistic estimates for the long-time behavior of the solutions that imply bounds for the dissipation scale and energy spectrum as R. 相似文献
92.
93.
P K Karmakar 《Pramana》2007,68(4):631-648
Application of inertia-induced acoustic excitation theory offers a new resonant excitation source channel of acoustic turbulence
in the transonic domain of plasma flow. In bi-ion plasmas like colloidal plasma, two well-defined transonic points exist corresponding
to the parent ion and the dust grain-associated acoustic modes. As usual, the modified ion acoustic mode (also known as dust
ion-acoustic (DIA) wave) dynamics associated with parent ion inertia is excitable for both nanoscale-and micronscale-sized
dust grains. It is found that the so-called (ion) acoustic mode (also known as dust-acoustic (DA) wave) associated with nanoscale
dust grain inertia is indeed resonantly excitable through the active role of weak but finite parent ion inertia. It is interestingly
conjectured that the same excitation physics, as in the case of normal plasma sound mode, operates through the active inertial
role of plasma thermal species. Details of the nonlinear acoustic mode analyses of current interest in transonic domains of
such impure plasmas in hydrodynamic flow are presented.
相似文献
94.
In this work we derive lower bounds for the Hausdorff and fractal dimensions of the global attractor of the Sabra shell model
of turbulence in different regimes of parameters. We show that for a particular choice of the forcing term and for sufficiently
small viscosity term ν, the Sabra shell model has a global attractor of large Hausdorff and fractal dimensions proportional
to log ν −1 for all values of the governing parameter ε, except for ε =1. The obtained lower bounds are sharp, matching the upper bounds
for the dimension of the global attractor obtained in our previous work. Moreover, the complexity of the dynamics of the shell
model increases as the viscosity ν tends to zero, and we describe a precise scenario of successive bifurcations for different
parameters regimes. In the “three-dimensional” regime of parameters this scenario changes when the parameter ε becomes sufficiently
close to 0 or to 1. We also show that in the “two-dimensional” regime of parameters, for a certain non-zero forcing term,
the long-term dynamics of the model becomes trivial for every value of the viscosity.
AMS Subject Classifications: 76F20, 76D05, 35Q30 相似文献
95.
We present a systematic way to compute the scaling exponents of the structure functions of the Kraichnan model of turbulent
advection in a series of powers of ξ, adimensional coupling constant measuring the degree of roughness of the advecting velocity
field. We also investigate the relation between standard and renormalization group improved perturbation theory. The aim is
to shed light on the relation between renormalization group methods and the statistical conservation laws of the Kraichnan
model, also known as zero modes. 相似文献
96.
97.
设计了大气激光通信信道测量系统,利用此系统在不同气象条件下进行了近地视距实验测量并采集了不同天气条件下的实验数据,详细分析讨论了所得实验数据并进行了误差分析.同时实验中获得了大量数据,为进一步完善大气激光信道模型提供了有力的依据. 相似文献
98.
We describe and demonstrate both our newest projection method (fully implicit) for the incompressible Navier-Stokes equations via the finite element method and our newest turbulence model - a somewhat sophisticated nonlinear (cubic) eddy viscosity model that does not employ wall functions or normal distances to walls - the combination providing a method and a model that is each applicable in arbitrary geometry. We demonstrate both via a flow simulation past an automobile-like body at a Reynolds number of 4.3 million. 相似文献
99.
S. Ya. Grinshpon 《代数通讯》2013,41(11):4273-4282
We study primary groups containing proper fully invariant subgroups isomorphie to the group. The admissable sequence of Ulm–Kaplansky invariants for primary groups is introduced. Using these sequences, If-groups are described in the classes of seperable and periodically complete groups. 相似文献
100.
The application of large-eddy simulation (LES) to particle-laden turbulence raises such a fundamental question as whether the LES with a subgrid scale (SGS) model can correctly predict Lagrangian time correlations (LTCs). Most of the currently existing SGS models are constructed based on the energy budget equations. Therefore, they are able to correctly predict energy spectra, but they may not ensure the correct prediction on the LTCs. Previous researches investigated the effect of the SGS modeling on the Eulerian time correlations. This paper is devoted to study the LTCs in LES. A direct numerical simulation (DNS) and the LES with a spectral eddy viscosity model are performed for isotropic turbulence and the LTCs are calculated using the passive vector method. Both a priori and a posteriori tests are carried out. It is observed that the subgrid;scale contributions to the LTCs cannot be simply ignored and the LES overpredicts the LTCs than the DNS. It is concluded from the straining hypothesis that an accurate prediction of enstrophy spectra is most critical to the prediction of the LTCs. 相似文献