Lagrangian velocity autocorrelation in isotropic turbulence

1991 ◽  
Vol 3 (8) ◽  
pp. 1924-1933 ◽  
Author(s):  
Yukio Kaneda ◽  
Toshiyuki Gotoh
Keyword(s):  
Isotropic Turbulence ◽  
Velocity Autocorrelation ◽  
Lagrangian Velocity

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.

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 %.

Diesel Droplet Diffusion in Isotropic Turbulence With Digital Holographic Cinematography

2005 ◽  
Author(s):  
Balaji Gopalan ◽  
Edwin Malkiel ◽  
Jian Sheng ◽  
Joseph Katz
Keyword(s):  
Time Series ◽  
High Speed ◽  
Isotropic Turbulence ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Time History ◽  
Sample Volume ◽  
Velocity Autocorrelation Function ◽  
Digital Cameras ◽  
Velocity Autocorrelation

High-speed in-line digital holographic cinematography was used to investigate the diffusion of droplets in locally isotropic turbulence. Droplets of diesel fuel (0.3–0.9mm diameter, specific gravity of 0.85) were injected into a 37×37×37mm3 sample volume located in the center of a 160-liter tank. The turbulence was generated by 4 spinning grids, located symmetrically in the corners of the tank, and was characterized prior to the experiments. The sample volume was back illuminated with two perpendicular collimated beams of coherent laser light and time series of in-line holograms were recorded with two high-speed digital cameras at 500 frames/sec. Numerical reconstruction generated a time series of high-resolution images of the droplets throughout the sample volume. We developed an algorithm for automatically detecting the droplet trajectories from each view, for matching the two views to obtain the three-dimensional tracks, and for calculating the time history of velocity. We also measured the mean fluid motion using 2-D PIV. The data enabled us to calculate the Lagrangian velocity autocorrelation function.

Turbulent Statistics of Nearly Isotropic Turbulence Generated by Four Rotating Grids and the Mean Falling Velocity of Particle Through Turbulence

2007 ◽  
Author(s):  
Tatsuo Ushijima ◽  
Osami Kitoh
Keyword(s):  
Isotropic Turbulence ◽  
Terminal Velocity ◽  
Mean Velocity ◽  
Velocity Autocorrelation ◽  
Air Turbulence ◽  
Turbulent Statistics ◽  
Experimental Apparatus ◽  
Particle Property ◽  
The Mean ◽  
Lda Measurement

Box air turbulence is experimentally generated in a rectangular box by using four counter-rotating grids installed inside. Turbulence statistics are obtained from one-point measurement of LDA. Nearly isotropic turbulence with zero-mean velocity is realised in the midst of four rotating grids. The dissipation rate is estimated from the Taylor time microscale of velocity autocorrelation obtained from LDA measurement, since Taylor’s frozen turbulence hypothesis is not applicable. From this estimation, the Reynolds number based on the Taylor length microscale becomes about 200 at maximum in the present experimental apparatus. The mean falling velocity of small particle in turbulent flow is measured in the box turbulence. It is found that the mean falling velocity of the inertia particle could be smaller or larger than the terminal velocity, depending on the particle property, if the ratios of particle response time to turbulence time scale are the same.

scholarly journals Particle tracking modeling of sediment-laden jets

2014 ◽  
Vol 39 ◽  
pp. 107-114 ◽  
Author(s):  
S. N. Chan ◽  
J. H. W. Lee
Keyword(s):  
Particle Tracking ◽  
Three Dimensional ◽  
Classical Solutions ◽  
Velocity Autocorrelation Function ◽  
Turbulent Fluctuation ◽  
Velocity Autocorrelation ◽  
Particulate Transport ◽  
Particle Tracking Model ◽  
Lagrangian Velocity ◽  
Tracking Model

Abstract. This paper presents a general model to predict the particulate transport and deposition from a sediment-laden horizontal momentum jet. A three-dimensional (3-D) stochastic particle tracking model is developed based on the governing equation of particle motion. The turbulent velocity fluctuations are modelled by a Lagrangian velocity autocorrelation function that captures the trapping of sediment particles in turbulent eddies, which result in the reduction of settling velocity. Using classical solutions of mean jet velocity, and turbulent fluctuation and dissipation rate profiles derived from computational fluid dynamics calculations of a pure jet, the equation of motion is solved numerically to track the particle movement in the jet flow field. The 3-D particle tracking model predictions of sediment deposition and concentration profiles are in excellent agreement with measured data. The computationally demanding Basset history force is shown to be negligible in the prediction of bottom deposition profiles.

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
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