The Experts below are selected from a list of 103533 Experts worldwide ranked by ideXlab platform
Alain Arneodo - One of the best experts on this subject based on the ideXlab platform.
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A multifractal formalism for vector-valued random fields based on wavelet analysis: application to Turbulent Velocity and vorticity 3D numerical data
Stochastic Environmental Research and Risk Assessment, 2007Co-Authors: Pierre Kestener, Alain ArneodoAbstract:Extreme atmospheric events are intimately related to the statistics of atmospheric Turbulent velocities. These, in turn, exhibit multifractal scaling, which is determining the nature of the asymptotic behavior of velocities, and whose parameter evaluation is therefore of great interest currently. We combine singular value decomposition techniques and wavelet transform analysis to generalize the multifractal formalism to vector-valued random fields. The so-called Tensorial Wavelet Transform Modulus Maxima (TWTMM) method is calibrated on synthetic self-similar 2D vector-valued multifractal measures and monofractal 3D vector-valued fractional Brownian fields. We report the results of some application of the TWTMM method to Turbulent Velocity and vorticity fields generated by direct numerical simulations of the incompressible Navier–Stokes equations. This study reveals the existence of an intimate relationship \({D_{{\bf v}}(h+1)=D_{\varvec{\omega}}(h)},\) between the singularity spectra of these two vector fields which are found significantly more intermittent than previously estimated from longitudinal and transverse Velocity increment statistics.
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Revealing a lognormal cascading process in Turbulent Velocity statistics with wavelet analysis
Philosophical Transactions of the Royal Society of London. Series A: Mathematical Physical and Engineering Sciences, 1999Co-Authors: Alain Arneodo, Sébastien Manneville, J. F. Muzy, Stéphane G. RouxAbstract:We use the continuous wavelet transform to extract a cascading process from experimental Turbulent Velocity signals. We mainly investigate various statistical quantities such as the singularity spe...
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Experimental Evidence for Anomalous Scale Dependent Cascading Process in Turbulent Velocity Statistics
Applied and Computational Harmonic Analysis, 1999Co-Authors: Alain Arneodo, Sébastien Manneville, J. F. Muzy, Stéphane G. RouxAbstract:Abstract We use a wavelet-based deconvolution method to extract some multiplicative cascading process from experimental Turbulent Velocity signals. We show that at the highest accessible Reynolds numbers, the experimental data do not allow us to discriminate between various phenomenological cascade models recently proposed to account for intermittency and their log-normal approximations. We further report evidence that Velocity fluctuations are not scale invariant but possess more complex self-similarity properties that are likely to depend on the Reynolds number. We comment on the possible asymptotic validity of the multifractal description.
Stéphane G. Roux - One of the best experts on this subject based on the ideXlab platform.
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Comprehensive multifractal analysis of Turbulent Velocity using the wavelet leaders
The European Physical Journal B, 2008Co-Authors: Bruno Lashermes, Patrice Abry, Stéphane G. Roux, Stéphane JaffardAbstract:The multifractal framework relates the scaling properties of turbulence to its local regularity properties through a statistical description as a collection of local singularities. The multifractal properties are moreover linked to the multiplicative cascade process that creates the peculiar properties of turbulence such as intermittency. A comprehensive estimation of the multifractal properties of turbulence from data analysis, using a tool valid for all kind of singularities (including oscillating singularities) and mathematically well-founded, is thus of first importance in order to extract a reliable information on the underlying physical processes. The wavelet leaders yield a new multifractal formalism which meets all these requests. This paper aims at describing it and at applying it to experimental Turbulent Velocity data. After a detailed discussion of the practical use of the wavelet leader based multifractal formalism, the following questions are carefully investigated: (1) What is the dependence of multifractal properties on the Reynolds number? (2) Are oscillating singularities present in Turbulent Velocity data? (3) Which multifractal model does correctly account for the observed multifractal properties? Results from several data set analysis are used to discuss the dependence of the computed multifractal properties on the Reynolds number but also to assess their common or universal component. An exact though partial answer (no oscillating singularities are detected) to the issue of the presence of oscillating singularities is provided for the first time. Eventually an accurate parameterization with cumulant exponents up to order 4 confirms that the log-normal model (with c2 = -0.025±0.002) correctly accounts for the universal multifractal properties of Turbulent Velocity.
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Revealing a lognormal cascading process in Turbulent Velocity statistics with wavelet analysis
Philosophical Transactions of the Royal Society of London. Series A: Mathematical Physical and Engineering Sciences, 1999Co-Authors: Alain Arneodo, Sébastien Manneville, J. F. Muzy, Stéphane G. RouxAbstract:We use the continuous wavelet transform to extract a cascading process from experimental Turbulent Velocity signals. We mainly investigate various statistical quantities such as the singularity spe...
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Experimental Evidence for Anomalous Scale Dependent Cascading Process in Turbulent Velocity Statistics
Applied and Computational Harmonic Analysis, 1999Co-Authors: Alain Arneodo, Sébastien Manneville, J. F. Muzy, Stéphane G. RouxAbstract:Abstract We use a wavelet-based deconvolution method to extract some multiplicative cascading process from experimental Turbulent Velocity signals. We show that at the highest accessible Reynolds numbers, the experimental data do not allow us to discriminate between various phenomenological cascade models recently proposed to account for intermittency and their log-normal approximations. We further report evidence that Velocity fluctuations are not scale invariant but possess more complex self-similarity properties that are likely to depend on the Reynolds number. We comment on the possible asymptotic validity of the multifractal description.
Prasun Dutta - One of the best experts on this subject based on the ideXlab platform.
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visibility moments and power spectrum of turbulence Velocity
Monthly Notices of the Royal Astronomical Society, 2016Co-Authors: Prasun DuttaAbstract:Here we introduce moments of visibility function and discuss how those can be used to estimate the power spectrum of the Turbulent Velocity of external spiral galaxies. We perform numerical simulation to confirm the credibility of this method and found that for galaxies with lower inclination angles it works fine. This is the only method to estimate the power spectrum of the Turbulent Velocity fluctuation in the ISM of the external galaxies.
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effect of Turbulent Velocity on the h i intensity fluctuation power spectrum from spiral galaxies
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: Prasun DuttaAbstract:We use numerical simulations to investigate effect of Turbulent Velocity on the power spectrum of H i intensity from external galaxies when (a) all emission is considered, (b) emission with Velocity range smaller than the Turbulent Velocity dispersion is considered. We found that for case (a) the intensity fluctuation depends directly only on the power spectrum of the column density, whereas for case (b) it depends only on the Turbulent Velocity fluctuation. We discuss the implications of this result in real observations of H i fluctuations.
Shiming Yang - One of the best experts on this subject based on the ideXlab platform.
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MEASUREMENTS OF Turbulent Velocity AND TEMPERATURE FIELDS FOR HIGH RAYLEIGH NUMBER NATURAL CONVECTION IN AN ENCLOSURE
Experimental Thermal and Fluid Science, 1993Co-Authors: Shiming YangAbstract:ABSTRACT An experimental study of the Turbulent Velocity and temperature fields for high Rayleigh number natural convecton in an enclosure was conducted. A water filled test cell with one heated vertical wall and one opposite cooled vertical wall was used. All the other walls were thermally insulated. The cell had an aspect ratio of 1. Velocity measurements were taken at Rayleigh number of 3.0×10 10 based on the height of the vertical walls. In addition to the laminar, transitional and Turbulent flow regions reported in the literature, a region near the corner with two recirculating flow structure was identified. Mean and fluctuating velocities were measured with laser-Doppler anemometer system. Mean and fluctuating temperatures were measured with fine-wire thermocouples. The concurrent measurement measurements of Velocity and temperature provided the much needed experimental data for a better understanding of the underlying physics of Turbulent natural convection in an enclosure.
Paolo Luchini - One of the best experts on this subject based on the ideXlab platform.
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universality of the Turbulent Velocity profile
Physical Review Letters, 2017Co-Authors: Paolo LuchiniAbstract:For nearly a century, the universal logarithmic law of the mean Velocity profile has been a mainstay of Turbulent fluid mechanics and its teaching. Yet many experiments and numerical simulations are not fit exceedingly well by it, and the question whether the logarithmic law is indeed universal keeps turning up in discussion and in writing. Large experiments have been set up in various parts of the world to confirm or deny the logarithmic law and accurately estimate von Karman's constant, the coefficient that governs it. Here, we show that the discrepancy among flows in different (circular or plane) geometries can be ascribed to the effect of the pressure gradient. When this effect is accounted for in the form of a higher-order perturbation, universal agreement emerges beyond doubt and a satisfactorily simple formulation is established.
