共查询到20条相似文献,搜索用时 15 毫秒
1.
Measurement and phenomenological analyses of intermittency growth in an experimental turbulent pipe flow and numerical turbulence are performed, for which working definitions such as degree, increment, and growth rate of intermittency are introduced with the help of quasiscaling theory. The logarithmic-normal inertial scaling model is extended to quasiscaling as the second-order truncation of the Taylor expansion and is used for studying the intermittency growth problem. The extended self-similarity properties are shown to be not consistent with the monotonicity of the third order local quasiscaling exponent and the nonmonotonic behaviour of the intermittency growth rate as a result of bottleneck. Digestions of the results with scale-dependent multifractals are provided. 相似文献
2.
B. Dubrulle 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):757-771
We develop a new approach to scale symmetry, which takes into account the possible finite cut-offs of the fields or the parameters.
This new symmetry, called finite size scale symmetry: i) includes the traditional self-similarity as a limiting case, when
the cut-offs are set to infinity (infinite size-system); ii) is consistent with the traditional finite size scaling approach
already used in critical phenomena; iii) enables the computation of some of the universal functions appearing in the finite
size scaling formulation; iv) allows scale transformations leaving the cut-offs invariant, like in the traditional renormalization
approach; v) can be formulated to allow for positive or negative fields and parameters; vi) leads to new predictions about
the shape of some distributions in critical phenomena or turbulence which are in very good agreement with the experimental
or numerical findings.
Received 26 January 1999 and Received in final form 25 October 1999 相似文献
3.
O. Chanal B. Chabaud B. Castaing B. Hébral 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):309-317
We analyse experimental velocity measurements on the axis of a low temperature gaseous helium jet. From independent increments
arguments, we reproduce the behaviour of structure functions. We show where this approach fails and how the intermittency
phenomenon is a small correction. The physical arguments under the multiplicative cascade models for this intermittency imply
an acceleration of this cascade close to the dissipative range, which we are able to evidence. This acceleration could be
responsible of the apparent Extended Self Similarity between structure functions of various orders.
Received 13 October 1999 and Received in final form 19 May 2000 相似文献
4.
5.
Bhimsen K. Shivamoggi 《Annals of Physics》2005,317(1):1-23
In this paper we give a formulation of two-dimensional (2D) collisionless magnetohydrodynamic (MHD) turbulence that includes the effects of both electron inertia and electron pressure (or parallel electron compressibility) and is applicable to strongly magnetized collisionless plasmas. We place particular emphasis on the departures from the 2D classical MHD turbulence results produced by the collisionless MHD effects. We investigate the fractal/multi-fractal aspects of spatial intermittency. The fractal model for intermittent collisionless MHD turbulence appears to be able to describe the observed k−1 spectrum in the solar wind. Multi-fractal scaling behaviors in the inertial range are first deduced, and are then extrapolated down to the dissipative microscales. We then consider a parabolic-profile model for the singularity spectrum f (α), as an explicit example of a multi-fractal scenario. These considerations provide considerable insights into the basic mechanisms underlying spatial intermittency in 2D fully developed collisionless MHD turbulence. 相似文献
6.
B. Mazzi F. Okkels J.C. Vassilicos 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):243-251
We present a shell-model of fractal induced turbulence which predicts that structure function scaling exponents decrease in
absolute value as the fractal dimension of the turbulence-inducing fractal object increases. This qualitative prediction is
in agreement with laboratory measurements. Finer details of the fractal induced turbulence statistics and dynamics depend
on the fractal force's phases, i.e. on the detailed construction of the fractal stirrer. In a case of deterministic forcing phases, a critical fractal dimension
exists below which the average rate of inter-scale energy transfer <T
n> is a decreasing function of the wavenumber kn and the structure function scaling exponents take close to Kolmogorov values. Above this critical fractal dimension, <T
n> is an increasing function of kn and the structure function scaling exponents deviate significantly from Kolmogorov values.
Received 25 June 2001 / Received in final form 5 April 2002 Published online 19 July 2002 相似文献
7.
A renormalization group (RG) formulation of the transition to chaotic behavior via intermittency in one-dimesional maps is presented. The known scaling behavior of the length of the laminar regions in the presence of external noise is obtained from the leading relevant eigenvalues of the RG transformation. In addition, the complete spectrum of eigenvalues and corresponding eigenfunctions is found. 相似文献
8.
9.
S. Bottin H. Chaté 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(1):143-155
We argue on general grounds that the transition to turbulence in plane Couette flow is best studied experimentally at a statistical
level. We present such a statistical analysis of experimental data guided by a parallel investigation of a simple coupled
map lattice model for spatiotemporal intermittency. We confirm that this generic type of spatiotemporal chaos is relevant
in the context of plane Couette flow, where the linear stability of the laminar regime at all Reynolds numbers insures the
necessary local subcriticality. Using large ensembles of similar experiments, we show the existence of a well-defined threshold
Reynolds number above which a unique, turbulent, intermittent attractor coexists with the laminar flow. Furthermore, our data
reveals that this transition to spatiotemporal intermittency is discontinuous, i.e. akin to a first-order phase transition.
Received: 10 April 1998 / Revised: 22 June 1998 / Accepted: 24 June 1998 相似文献
10.
Y. Malécot C. Auriault H. Kahalerras Y. Gagne O. Chanal B. Chabaud B. Castaing 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(3):549-561
The velocity increments statistic in various turbulent flows is analysed through the hypothesis that different scales are
linked by a multiplicative process, of which multiplier is infinitely divisible. This generalisation of the Kolmogorov-Obukhov
theory is compatible with the finite Reynolds number value of real flows, thus ensuring safe extrapolation to the infinite
Reynolds limit. It exhibits a estimator universally depending on the Reynolds number of the flow, with the same law either for Direct Numerical Simulations
or experiments, both for transverse and longitudinal increments. As an application of this result, the inverse dependence
is used to define an unbiased value for a Large Eddy Simulation from the resolved scales velocity statistics. However, the exact shape of the multiplicative
process, though independent of the Reynolds number for a given experimental setup, is found to depend significantly on this
setup and on the nature of the increment, longitudinal or transverse. The asymmetry of longitudinal velocity increments probability
density functions exhibits similarly a dependence with the experimental setup, but also systematically depends on the Reynolds
number.
Received 7 January 2000 and Received in final form 17 March 2000 相似文献
11.
M. Buzzicotti H. Aluie L. Biferale J. Brasseur C. Meneveau 《Journal of Turbulence》2018,19(2):167-197
The effects of different filtering strategies on the statistical properties of the resolved-to-subfilter scale (SFS) energy transfer are analysed in forced homogeneous and isotropic turbulence. We carry out a-priori analyses of the statistical characteristics of SFS energy transfer by filtering data obtained from direct numerical simulations with up to 20483 grid points as a function of the filter cutoff scale. In order to quantify the dependence of extreme events and anomalous scaling on the filter, we compare a sharp Fourier Galerkin projector, a Gaussian filter and a novel class of Galerkin projectors with non-sharp spectral filter profiles. Of interest is the importance of Galilean invariance and we confirm that local SFS energy transfer displays intermittency scaling in both skewness and flatness as a function of the cutoff scale. Furthermore, we quantify the robustness of scaling as a function of the filtering type. 相似文献
12.
S. Bajpai M. S. Tirumkudulu 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(3):293-297
An impulsively started turbulent jet injected into quiescent surroundings with a constant inlet velocity has been studied
experimentally. Results show that the jet length increases linearly with the square-root of time, over a wide range of Reynolds
number calculated with respect to the jet diameter. The celerity factor, xf/t U, has been found to be nearly constant at 2.47 throughout with a 5% variance. Here, xf is the jet length, t is the time and U is the jet exit velocity. These results compare favourably with earlier results reported
at lower Reynolds numbers. Finally, we present a simple model based on the integral energy balance of the turbulent boundary
layer equation for an impulsively started turbulent axisymmetric jet. The model predicts a jet length that scales as,
where d is the nozzle diameter and B(≈6.0) is the velocity-decay constant. This gives a celerity factor,
in close agreement with the experiments. 相似文献
13.
Intermittency is a basic feature of fully developed turbulence, for both velocity and passive scalars.
Intermittency is classically characterized by
Eulerian scaling exponent of structure functions. The same approach can
be used in a Lagrangian framework to characterize the temporal
intermittency of the velocity and passive scalar concentration of a an element of fluid advected by a turbulent intermittent
field. Here we focus on
Lagrangian passive scalar scaling exponents, and discuss their possible links
with Eulerian passive scalar and mixed velocity-passive scalar structure functions.
We provide different transformations between these scaling exponents,
associated to different transformations linking space and time scales.
We obtain four new explicit relations.
Experimental data are needed to test these predictions for Lagrangian passive
scalar scaling exponents. 相似文献
14.
S. Aumaître S. Fauve J.F. Pinton 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(3):563-567
We report an experimental study of large scale correlations in the power injected in turbulent swirling flows generated in
the gap between two coaxial rotating disks. We measure the pressure fluctuations on the blades of one disk, as well as the
pressure drop between the leading and the trailing edges of the rotating blades, i.e. the local drag force. Measurements at different positions on one blade and on two successive blades display a correlation
length much larger than the ones usually expected in turbulent flows. The time lag for which the correlation between two points
is maximum, strongly depends on the global flow configuration. These results help us to understand the statistical properties
of the injected power fluctuations in turbulent swirling flows.
Received 2 September 1999 相似文献
15.
16.
Direct numerical simulations (DNS) or experiments for the very high Reynolds (Re) and Péclet (Pe) number flows commonly exceed the resolution possible even when use is made of the most advanced computer capability or most sophisticated diagnostics and physical capabilities of advanced laboratory facilities. In practice use is made of statistical flow data bases developed at the highest Re and Pe levels achievable within the currently available facility limitations. In addition, there is presently no metric to indicate whether and how much of the fully resolved physics of the flow of interest has been captured within the facilities available. In this Letter the authors develop the necessary metric criteria for homogeneous, isotropic and shear layer flows. It is based on establishing a smaller subset of the total range of dynamic scale interactions that will still faithfully reproduce all of the essential, significant, influences of the larger range of scale interactions. The work identifies a minimum significant Re and Pe level that must be obtained by DNS or experiment in order to capture all of the significant dynamic influences in data which is then scaleable to flows of interest. Hereafter this is called the minimum state. Determination of the minimum state is based on finding a minimum scale separation for the energy-containing scales of the flow and scalar fields sufficient to prevent contamination by interaction with the (non-universal) velocity dissipation and scalar diffusivity inertial range scale limits. 相似文献
17.
Persistency of material element deformation in isotropic flows and growth rate of lines and surfaces
J. Duplat E. Villermaux 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):353-361
We explore the consequence of isotropy on the growth of material lines and surfaces in complex flows. We show that the key
parameter is the persistency , defined as the product of a typical stretching rate to its associated coherence time . In particular, we derive the dependence of the net growth rate of both lines and surfaces on . Their growth rates increase strongly with increasing persistencies for small , and then saturate for . Making use of measurements of Girimaji and Pope [1], we estimate the persistency to be of order 1 in isotropic turbulence. We then comment on the evolution of the shape of an initially spherical material
blob. While its length increases, one of its tranverse dimension increases slowly and the other one decreases. This quasi-two-dimensional
deformation leads a final ribbon-shape.
Received 10 November 1999 and Received in final form 14 August 2000 相似文献
18.
H. Willaime J. Maurer F. Moisy P. Tabeling 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):363-369
Turbulence produced in low temperature helium gas flowing over arrays of rectangular- and triangular-shaped blunt obstacles
is investigated experimentally. The set-up allows both low fluctuation rates (down to 8%), and high microscale Reynolds numbers,
(up to 1 150). The forced Kolmogorov equation is found to apply accurately. Similar to another flow configuration (counter
rotating flow case [1]), the analysis of the flatness factor evolution with the Reynolds number reveals a transitional behavior
around 650.
Received 26 August 1999 and Received in final form 28 August 2000 相似文献
19.
A. Bershadskii T. Nakano D. Fukayama T. Gotoh 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(1):95-101
Using results of a direct numerical simulation (DNS) of 3D turbulence we show that the observed generalized scaling (i.e. scaling moments versus moments of different orders) is consistent with a lognormal-like distribution of turbulent energy dissipation fluctuations
with moderate amplitudes for all space scales available in this DNS (beginning from the molecular viscosity scale up to largest ones). Local multifractal thermodynamics has been developed to interpret the data obtained using the generalized scaling, and a new interval
of space scales with inverse cascade of generalized energy has been found between dissipative and inertial intervals of scales
for sufficiently large values of the Reynolds number.
Received 21 July 2000 相似文献
20.
Turbulent Boundary Layer Control via a Streamwise Travelling Wave Induced by an External Force 下载免费PDF全文
Turbulent boundary layer control via a streamwise travelling wave is investigated based on direct numerical simulation of an incompressible turbulent channel flow. The streamwise travelling wave is induced on one side wall of the channel by a spanwise external force, e.g., Lorenz force, which is con~ned in the viscous sublayer. As the control strategy used in this study has never been examined, we pay our attention to its efficiency of drag control. It is revealed that the propagating direction of the travelling wave, i.e., the downstream or upstream propagating direction with respect to the streamwise flow, has an important role on the drag control, leading to a significant drag reduction or enhancement for the parameters considered. The coherent structures of turbulent boundary layer are altered and the underlying mechanisms are analysed. The results obtained provide physical insight into the understanding of turbulent boundary layer control. 相似文献