Journal ArticleDOI
Measurements of the Small-Scale Structure of Turbulence at Moderate Reynolds Numbers
J. C. Wyngaard,H. Tennekes +1 more
TLDR
In this article, the first two time derivatives of the streamwise velocity fluctuation in a mixing layer are presented, and the probability distributions of squared derivatives are found to be nearly log normal.Abstract:
Measurements of probability densities and distributions, moments, and spectra obtained from the first two time derivatives of the streamwise velocity fluctuation in a mixing layer are presented. Probability distributions of squared derivatives are found to be nearly log normal. The skewness (S) and kurtosis (K) of the first derivative are compared with new atmospheric data at much higher Reynolds numbers. Reynolds-number dependence is indicated, in conflict with universal equilibrium theory. A modified theory using fluctuating dissipation predicts that S and K have power-law behavior with turbulent Reynolds number and are related by S ∝ K3/8, in general agreement with the trends of the limited data available.read more
Citations
More filters
Journal ArticleDOI
Processing of polyurethane/polyester interpenetrating polymer networks by reaction injection molding. Part II: Mixing at high reynolds numbers and impingement pressures
Luu T. Nguyen,Nam P. Suh +1 more
TL;DR: In this paper, the impingement mixing process is analyzed considering the characteristic times of all the mechanisms involved and two models of the mixing phenomenon are postulated; one takes into consideration the energetic nature of the shearing and stretching mechanisms during impingements while the other calls for the statistical variations in the kinetic energy dissipation process.
Journal ArticleDOI
Taylor's hypothesis and spectra of velocity and temperature derivatives in a turbulent shear flow
TL;DR: In this paper, the spectral densities of temporal velocity and temperature derivatives, measured in the atmospheric turbulent boundary layer and on the axis of a turbulent plane jet, are compared with the spectral density of the ratios of these derivatives and of the local longitudinal instantaneous velocity.
Journal ArticleDOI
Recurrence of high concentration values in a diffusing, fluctuating scalar field
TL;DR: In this article, a simple model for estimating the average number of occurrences per unit time η(c 0) that a threshold concentration c 0 is exceeded is proposed, based on the joint probability density of the observed concentration c(t) and its time derivative ċ(t).
Journal ArticleDOI
Vortex gas modeling of turbulent circulation statistics.
TL;DR: The model introduced here borrows ideas from the structural approach to turbulence, whereby turbulent flows are depicted as dilute vortex gases, combined with the standard Obukhov-Kolmogorov phenomenological framework of small-scale intermittency, and is able to reproduce key statistical features of circulation, in close agreement with empirical observations compiled from direct numerical simulations.
Journal ArticleDOI
Tsallis non-extensive statistical mechanics of El Niño southern oscillation index
Marcel Ausloos,Filippo Petroni +1 more
TL;DR: In this article, the shape and tails of partial distribution functions (PDF) for a climatological signal, i.e., the El Nino SOI and the turbulent nature of the ocean-atmosphere variability are linked through a model encompassing Tsallis non-extensive statistics and leading to evolution equations of the Langevin and Fokker-Planck type.
References
More filters
Book
The theory of homogeneous turbulence
TL;DR: In this article, the kinematics of the field of homogeneous turbulence and the universal equilibrium theory of decay of the energy-containing eddies are discussed. But the authors focus on the dynamics of decay and not on the probability distribution of u(x).