The Dependence of the Time Scale of Relative Lagrangian Motion on the Initial Separation

1998 ◽  
Vol 65 (1) ◽  
pp. 204-208
Author(s):  
J. C. H. Fung
Keyword(s):  
Isotropic Turbulence ◽  
Homogeneous Isotropic Turbulence ◽  
Kinematic Simulation ◽  
Lagrangian Statistics ◽  
Initial Separation ◽  
Velocity Autocorrelation ◽  
Lagrangian Velocity ◽  
Short Time ◽  
Lagrangian Motion ◽  
Statistics Of Turbulence

Kinematic simulation of homogeneous isotropic turbulence are used to compute Lagrangian statistics of turbulence and, in particular, its time scales. The computed pseudo-Lagrangian velocity autocorrelation functions Rˆ11L(l,t) compare well with theory for a small initial separation l and short time t. We also demonstrate the feasibility of using kinematic simulation as a means of constructing Lagrangian statistics.

scholarly journals Lagrangian statistics of particle pairs in homogeneous isotropic turbulence

2005 ◽  
Vol 17 (11) ◽  
pp. 115101 ◽  
Author(s):  
L. Biferale ◽  
G. Boffetta ◽  
A. Celani ◽  
B. J. Devenish ◽  
A. Lanotte ◽  
...  
Keyword(s):  
Isotropic Turbulence ◽  
Homogeneous Isotropic Turbulence ◽  
Lagrangian Statistics ◽  
Particle Pairs

scholarly journals Lagrangian statistics of pressure fluctuation events in homogeneous isotropic turbulence

2019 ◽  
Vol 31 (8) ◽  
pp. 085111 ◽  
Author(s):  
Mehedi Bappy ◽  
Pablo M. Carrica ◽  
Gustavo C. Buscaglia
Keyword(s):  
Pressure Fluctuation ◽  
Isotropic Turbulence ◽  
Homogeneous Isotropic Turbulence ◽  
Lagrangian Statistics

Lagrangian velocity correlations in homogeneous isotropic turbulence

1993 ◽  
Vol 5 (11) ◽  
pp. 2846-2864 ◽  
Author(s):  
Toshiyuki Gotoh ◽  
Robert S. Rogallo ◽  
Jackson R. Herring ◽  
Robert H. Kraichnan
Keyword(s):  
Isotropic Turbulence ◽  
Homogeneous Isotropic Turbulence ◽  
Lagrangian Velocity

A measurement of Lagrangian velocity autocorrelation in approximately isotropic turbulence

1974 ◽  
Vol 62 (2) ◽  
pp. 255-271 ◽  
Author(s):  
D. J. Shlien ◽  
S. Corrsin
Keyword(s):  
Isotropic Turbulence ◽  
Coefficient Function ◽  
Mean Flow ◽  
Velocity Autocorrelation ◽  
Velocity Statistics ◽  
Dispersion Data ◽  
Lagrangian Velocity ◽  
Heated Wire ◽  
Heat Dispersion ◽  
The Mean

By measuring the heat dispersion behind a heated wire stretched across a wind tunnel (Taylor 1921, 1935), the Lagrangian velocity autocorrelation was determined in an approximately isotropic, grid-generated turbulent flow. The techniques were similar to previous ones, but the scatter is less. Assuming self-preservation of the Lagrangian velocity statistics in a form consistent with recent measurements of decay in this flow (Comte-Bellot & Corrsin 1966, 1971), a stationary and an approximately self-preserving form for the dispersion were derived and approximately verified over the range of the experiment.Possibly the most important aspect of this experiment is that data were available in the same flow on the simplest Eulerian velocity autocorrelation in time, the correlation at a fixed spatial point translating with the mean flow (Comte-Bellot & Corrsin 1971). Thus, the Lagrangian velocity autocorrelation coefficient function calculated from the dispersion data could be compared with this corresponding Eulerian function. It was found that the Lagrangian Taylor micro-scale is very much larger than the analogous Eulerian microscale (76 ms compared with 6.2ms), contrary to an estimate of Corrsin (1963). The Lagrangian integral time scale is roughly equal to the Eulerian one, being larger by about 25 %.

Lagrangian statistics from direct numerical simulations of isotropic turbulence

1989 ◽  
Vol 207 ◽  
pp. 531-586 ◽  
Author(s):  
P. K. Yeung ◽  
S. B. Pope
Keyword(s):  
Numerical Simulations ◽  
Isotropic Turbulence ◽  
Reynolds Numbers ◽  
Small Time ◽  
Direct Numerical Simulations ◽  
Time Lags ◽  
Lagrangian Statistics ◽  
Lagrangian Velocity ◽  
Velocity Increments ◽  
Non Gaussian

A comprehensive study is reported of the Lagrangian statistics of velocity, acceleration, dissipation and related quantities, in isotropic turbulence. High-resolution direct numerical simulations are performed on 643 and 1283 grids, resulting in Taylor-scale Reynolds numbers Rλ in the range 38-93. The low-wavenumber modes of the velocity field are forced so that the turbulence is statistically stationary. Using an accurate numerical scheme, of order 4000 fluid particles are tracked through the computed flow field, and hence time series of Lagrangian velocity and velocity gradients are obtained.The results reported include: velocity and acceleration autocorrelations and spectra; probability density functions (p.d.f.'s) and moments of Lagrangian velocity increments; and p.d.f.'s, correlation functions and spectra of dissipation and other velocity-gradient invariants. It is found that the acceleration variance (normalized by the Kolmogorov scales) increases as R½λ - a much stronger dependence than predicted by the refined Kolmogorov hypotheses. At small time lags, the Lagrangian velocity increments are distinctly non-Gaussian with, for example, flatness factors in excess of 10. The enstrophy (vorticity squared) is found to be more intermittent than dissipation, having a standard-deviation-to-mean ratio of about 1.5 (compared to 1.0 for dissipation). The acceleration vector rotates on a timescale about twice the Kolmogorov scale, while the timescales of acceleration magnitude, dissipation and enstrophy appear to scale with the Lagrangian velocity timescale.

Nondiffusive Brownian Motion Studied by Diffusing-Wave Spectroscopy

1989 ◽  
Vol 177 ◽  
Author(s):  
D. J. Pine ◽  
D. A. Weitz ◽  
D. J. Durian ◽  
P. N. Pusey ◽  
R. J. A. Tough
Keyword(s):  
Autocorrelation Function ◽  
Colloidal Particles ◽  
Scattered Light ◽  
Short Time Scale ◽  
Velocity Autocorrelation Function ◽  
Velocity Autocorrelation ◽  
Power Law Decay ◽  
Brownian Particles ◽  
Short Time ◽  
Surrounding Fluid

ABSTRACTOn a short time scale, Brownian particles undergo a transition from initially ballistic trajectories to diffusive motion. Hydrodynamic interactions with the surrounding fluid lead to a complex time dependence of this transition. We directly probe this transition for colloidal particles by measuring the autocorrelation function of multiply scattered light and observe the effects of the slow power-law decay of the velocity autocorrelation function.

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