CiteULike: l-alex's library [1063 articles]

Lagrangian Statistical Theory of Fully Developed Hydrodynamical Turbulence

KP Zybin — 2008-05-03T21:52:26-00:00

Physical Review Letters, Vol. 100, No. 17. (2008)

The Lagrangian velocity structure functions in the inertial range of fully developed fluid turbulence are for the first time derived based on the Navier-Stokes equation. For time much smaller than the correlation time, the structure functions are shown to obey the scaling relations Kn()n. The scaling exponents n are calculated analytically without any fitting parameters. The obtained values are in amazing agreement with the experimental results of the Bodenschatz group. A new relation connecting the Lagrangian structure functions of different orders analogously to the extended self-similarity ansatz is found.

Invariants of the velocity-gradient, rate-of-strain, and rate-of-rotation tensors across the turbulent/nonturbulent interface in jets

Carlos da Silva — 2008-05-03T21:51:57-00:00

Physics of Fluids, Vol. 20, No. 5. (2008)

Kolmogorov 4/5 law, nonlocality, and sweeping decorrelation hypothesis

M Kholmyansky — 2008-04-26T17:48:17-00:00

Physics of Fluids, Vol. 20, No. 4. (2008)

Flow in two-sided lid-driven cavities: non-uniqueness, instabilities, and cellular structures

HC Kuhlmann — 2008-04-17T12:43:25-00:00

Journal of Fluid Mechanics, Vol. 336, No. -1. (2000), pp. 267-299.

Experiments on the flow stability in a double-lid-driven cavity

T Siegmann-Hegerfeld — 2008-04-17T12:28:17-00:00

PAMM, Vol. 5, No. 1. (2005), pp. 551-552.

The stability of the two-dimensional, steady, incompressible flow in a rectangular square cavity is investigated experimentally for the parallel motion of two facing walls. The critical Reynolds numbers for the onset of three-dimensional steady flow, its structure, and the bifurcation diagram of the velocity field, measured by LDV, agree with numerical predictions. It is observed that the wavelength of the selected pattern increases with the Reynolds number. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Flow of pulp fibre suspension and slurries: A review

Heping Cui — 2008-04-07T19:06:29-00:00

International Journal of Multiphase Flow, Vol. 33, No. 9. (September 2007), pp. 921-934.

This paper reviews recent experimental and modeling work on biomass multiphase flow of suspensions and slurries. Problems associated with fibre flows (e.g., fibre flocculation, velocity profiles, flow regimes) have received considerable attention for these processes, involving both liquid-solid and gas-liquid-solid systems. Advanced experimental techniques have been employed in efforts to understand the flows. However, each of these experimental techniques is somewhat limited in its application. In the modelling work, mechanistic models, including those based on CFD, are being developed, but turbulence and interactions among particles and between the particles and fluid have so far limited the success of such models. Future work is needed to improve biomass energy and materials conversion processes.

On the universality of the Kolmogorov constant

Katepalli Sreenivasan — 2008-03-22T23:05:50-00:00

Physics of Fluids, Vol. 7, No. 11. (1995), pp. 2778-2784.

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Universality of the Kolmogorov constant in numerical simulations of turbulence

PK Yeung — 2008-03-22T23:04:31-00:00

Physical Review E, Vol. 56, No. 2. (1997), 1746.

Motivated by a recent survey of experimental data [K. R. Sreenivasan; Phys. Fluids 7 ; 2778 (1995)]; we examine data on the Kolmogorov spectrum constant in numerical simulations of isotropic turbulence; using results both from previous studies and from new direct numerical simulations over a range of Reynolds numbers (up to 240 on the Taylor scale) at grid resolutions up to 512 3 . It is noted that in addition to k -5/3 scaling; identification of a true inertial range requires spectral isotropy in the same wave-number range. The new simulations indicate approximate inertial range behavior at lower wave numbers than previously thought; with proportionality constants C 1 and C in the one- and three-dimensional energy spectra; respectively; about 0.60 and 1.62. The latter suggests C 1 ≈0.53; in excellent agreement with experiments. However; the one- and three-dimensional estimates are not fully consistent; because of departures (due to numerical and statistical limitations) from isotropy of the computed spectra at low wave numbers. The inertial scaling of structure functions in physical space is briefly addressed.

Fractals and Multifractals in Fluid Turbulence

KR Sreenivasan — 2008-03-22T15:07:25-00:00

Annual Review of Fluid Mechanics, Vol. 23, No. 1. (1991), pp. 539-604.

Spatial resolution of the vorticity meter and other hot-wire arrays

J Wyngaard — 2008-03-07T20:16:33-00:00

J. Phys E: Scientific Instruments (1969)

Proper orthogonal decomposition and low-dimensional models for driven cavity flows

W Cazemier — 2008-02-02T09:10:51-00:00

Physics of Fluids, Vol. 10, No. 7. (1998), pp. 1685-1699.

Statistics of passive tracers in three-dimensional magnetohydrodynamic turbulence

Angela Busse — 2008-01-08T21:56:56-00:00

Physics of Plasmas, Vol. 14, No. 12. (2007)

Geometrical properties of the vorticity vector derived using large-eddy simulation

Bing-Chen Wang — 2008-01-05T16:04:19-00:00

Fluid Dynamics Research, Vol. 40, No. 2. (February 2008), pp. 123-154.

In this paper, the geometrical properties of the resolved vorticity vector derived from large-eddy simulation are investigated using a statistical method. Numerical tests have been performed based on a turbulent Couette channel flow using three different dynamic linear and nonlinear subgrid-scale stress models. The geometrical properties of have a significant impact on various physical quantities and processes of the flow. To demonstrate, we examined helicity and helical structure, the attitude of with respect to the eigenframes of the resolved strain rate tensor and negative subgrid-scale stress tensor -[tau]ij, enstrophy generation, and local vortex stretching and compression. It is observed that the presence of the wall has a strong anisotropic influence on the alignment patterns between and the eigenvectors of , and between and the resolved vortex stretching vector. Some interesting wall-limiting geometrical alignment patterns and probability density distributions in the form of Dirac delta functions associated with these alignment patterns are reported. To quantify the subgrid-scale modelling effects, the attitude of with respect to the eigenframe of -[tau]ij is studied, and the geometrical alignment between and the Euler axis is also investigated. The Euler axis and angle for describing the relative rotation between the eigenframes of -[tau]ij and are natural invariants of the rotation matrix, and are found to be effective for characterizing a subgrid-scale stress model and for quantifying the associated subgrid-scale modelling effects on the geometrical properties of .

Comments on “Turbulent Hydrodynamic Line Stretching: Consequences of Isotropy”

Steven Orszag — 2008-01-05T08:16:11-00:00

Physics of Fluids, Vol. 13, No. 8. (1970), pp. 2203-2204.

Efficient Computation and Visualization of Coherent Structures in Fluid Flow Applications Efficient Computation and Visualization of Coherent Structures in Fluid Flow Applications

Christoph Garth — 2008-01-01T13:20:21-00:00

Transactions on Visualization and Computer Graphics, Vol. 13, No. 6. (2007), pp. 1464-1471.

The recently introduced notion of Finite-Time Lyapunov Exponent to characterize Coherent Lagrangian Structures provides a powerful framework for the visualization and analysis of complex technical flows. Its definition is simple and intuitive, and it has a deep theoretical foundation. While the application of this approach seems straightforward in theory, the associated computational cost is essentially prohibitive. Due to the Lagrangian nature of this technique, a huge number of particle paths must be computed to fill the space-time flow domain. In this paper, we propose a novel scheme for the adaptive computation of FTLE fields in two and three dimensions that significantly reduces the number of required particle paths. Furthermore, for three-dimensional flows, we show on several examples that meaningful results can be obtained by restricting the analysis to a well-chosen plane intersecting the flow domain. Finally, we examine some of the visualization aspects of FTLE-based methods and introduce several new variations that help in the analysis of specific aspects of a flow.

Effect of the wall on the velocity autocorrelation function and long-time tail of Brownian motion in a viscous compressible fluid

BU Felderhof — 2008-01-01T09:04:44-00:00

The Journal of Chemical Physics, Vol. 123, No. 18. (2005)

Chemical and biological activity in open flows: A dynamical system approach

Tamas Tel — 2007-12-28T23:54:15-00:00

Physics Reports, Vol. 413, No. 2-3. (July 2005), pp. 91-196.

Chemical and biological processes often take place in fluid flows. Many of them, like environmental or microfluidical ones, generate filamentary patterns which have a fractal structure, due to the presence of chaos in the underlying advection dynamics. In such cases, hydrodynamical stirring strongly couples to the reactivity of the advected species: the outcome of the reaction is then typically different from that of the same reaction taking place in a well-mixed environment. Here we review recent progress in this field, which became possible due to the application of methods taken from dynamical system theory. We place special emphasis on the derivation of effective rate equations which contain singular terms expressing the fact that the reaction takes place on a moving fractal catalyst, on the unstable foliation of the reaction free advection dynamics.

Micromixers—a review

Nam-Trung Nguyen — 2007-12-28T23:53:09-00:00

Journal of Micromechanics and Microengineering, Vol. 15, No. 2. (2005), pp. R1-R16.

This review reports the progress on the recent development of micromixers. The review first presents the different micromixer types and designs. Micromixers in this review are categorized as passive micromixers and active micromixers. Due to the simple fabrication technology and the easy implementation in a complex microfluidic system, passive micromixers will be the focus of this review. Next, the review discusses the operation points of the micromixers based on characteristic dimensionless numbers such as Reynolds number Re, Peclet number Pe, and in dynamic cases the Strouhal number St. The fabrication technologies for different mixer types are also analysed. Quantification techniques for evaluation of the performance of micromixers are discussed. Finally, the review addresses typical applications of micromixers.

Rigid particles suspended in time-dependent flows: irregular versus regular motion, disorder versus order

Andrew Szeri — 2007-12-28T22:51:26-00:00

Journal of Fluid Mechanics Digital Archive, Vol. 237, No. -1. (2006), pp. 33-56.

Suspensions of Rodlike Particles: Literature Review and Data Correlations

E Ganani — 2007-12-28T22:44:35-00:00

Journal of Composite Materials, Vol. 19, No. 3. (1 January 1985), pp. 194-215.

Recent experimental work on the macroscopic rheological properties of suspensions of rodlike particles in Newtonian and non-Newtonian fluids is reviewed. Correlations are proposed for the shear viscosity-shear rate relationship for semi-concentrated and concentrated suspensions. In the former case, shear thinning behavior is found with the slope of the power law region depending upon fiber aspect ratio. For the concen trated systems, the data are substantially independent of volume fraction and aspect ratio and show slight shear thinning. 10.1177/002199838501900301

Eulerian diagnostics for Lagrangian chaos in three-dimensional Navier-Stokes flows

AN Yannacopoulos — 2007-12-28T22:43:11-00:00

Physical Review E, Vol. 57, No. 1. (January 1998), 482.

Based on symmetry considerations; Eulerian quantities are defined which can serve as diagnostics for the regions of the flow where Lagrangian chaos is possible in a three-dimensional Navier-Stokes flow. The applicability of the diagnostics is tested in two model flows which are perturbative solutions of the three-dimensional Navier-Stokes equation: the eccentric Taylor vortex and the (concentric) wavy Taylor vortex.

Increase in regularity by polymer addition during chaotic mixing in two-dimensional flows

CW Leong — 2007-12-25T05:52:23-00:00

Physical Review Letters, Vol. 64, No. 8. (19 February 1990), 874.

Experiments show that the addition of small amounts of polymer to a Newtonian fluid undergoing chaotic advection decreases the amount of chaos; regular or unmixed regions increase in size and squeeze out the regions of chaotic behavior while preserving underlying symmetries. The size of the islands increases with increasing elasticity and rate of stirring. Large effects are present at relatively low Deborah numbers (relaxation time of the fluid to the time scale of the flow).

Refinement of the probability density function model for preferential concentration of aerosol particles in isotropic turbulence

Leonid Zaichik — 2007-11-28T12:08:24-00:00

Physics of Fluids, Vol. 19, No. 11. (2007)

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Evaluation of some proposed forms of Lagrangian velocity correlation coefficient

K Manomaiphiboon — 2007-11-24T08:17:19-00:00

International Journal of Heat and Fluid Flow, Vol. 24, No. 5. (October 2003), pp. 709-712.

This work evaluates four different forms of Lagrangian velocity correlation coefficient for stationary homogeneous turbulence at very large Reynolds numbers through consideration of simple mathematical and physical requirements. It is shown that some of them do not comply well with the requirements and may not be appropriate for use.

Small-scale statistics in high-resolution direct numerical simulation of turbulence: Reynolds number dependence of one-point velocity gradient statistics

T Ishihara — 2007-11-18T22:12:20-00:00

J. Fluid Mech, Vol. 592 (2007), pp. 335-366.

One-point statistics of velocity gradients and Eulerian and Lagrangian accelerations are studied by analysing the data from high-resolution direct numerical simulations (DNS) of turbulence in a periodic box, with up to 40963 grid points. The DNS consist of two series of runs; one is with kmaxη ~ 1 (Series 1) and the other is with kmaxη ~ 2 (Series 2), where kmax is the maximum wavenumber and η the Kolmogorov length scale. The maximum Taylor-microscale Reynolds number Rλ in Series 1 is about 1130, and it is about 675 in Series 2. Particular attention is paid to the possible Reynolds number (Re) dependence of the statistics. The visualization of the intense vorticity regions shows that the turbulence field at high Re consists of clusters of small intense vorticity regions, and their structure is to be distinguished from those of small eddies. The possible dependence on Re of the probability distribution functions of velocity gradients is analysed through the dependence on Rλ of the skewness and flatness factors (S and F). The DNS data suggest that the Rλ dependence of S and F of the longitudinal velocity gradients fit well with a simple power law: S ~ −0.32Rλ0.11 and F ~ 1.14Rλ0.34, in fairly good agreement with previous experimental data. They also suggest that all the fourth-order moments of velocity gradients scale with Rλ similarly to each other at Rλ > 100, in contrast to Rλ < 100. Regarding the statistics of time derivatives, the second-order time derivatives of turbulent velocities are more intermittent than the first-order ones for both the Eulerian and Lagrangian velocities, and the Lagrangian time derivatives of turbulent velocities are more intermittent than the Eulerian time derivatives, as would be expected. The flatness factor of the Lagrangian acceleration is as large as 90 at Rλ ≈ 430. The flatness factors of the Eulerian and Lagrangian accelerations increase with Rλ approximately proportional to RλαE and RλαL, respectively, where αE ≈ 0.5 and αL ≈ 1.0, while those of the second-order time derivatives of the Eulerian and Lagrangian velocities increases approximately proportional to RλβE and RλβL, respectively, where βE ≈ 1.5 and βL ≈ 3.0.

Polymer scaling and dynamics in steady-state sedimentation at infinite P[e-acute]clet number

V Lehtola — 2007-11-10T20:12:07-00:00

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 76, No. 5. (2007)

We consider the static and dynamical behavior of a flexible polymer chain under steady-state sedimentation using analytic arguments and computer simulations. The model system comprises a single coarse-grained polymer chain of N segments, which resides in a Newtonian fluid as described by the Navier-Stokes equations. The chain is driven into nonequilibrium steady state by gravity acting on each segment. The equations of motion for the segments and the Navier-Stokes equations are solved simultaneously using an immersed boundary method, where thermal fluctuations are neglected. To characterize the chain conformation, we consider its radius of gyration RG(N). We find that the presence of gravity explicitly breaks the spatial symmetry leading to anisotropic scaling of the components of RG with N along the direction of gravity RG,|| and perpendicular to it RG,, respectively. We numerically estimate the corresponding anisotropic scaling exponents ||0.79 and 0.45, which differ significantly from the equilibrium scaling exponent e=0.588 in three dimensions. This indicates that on the average, the chain becomes elongated along the sedimentation direction for large enough N. We present a generalization of the Flory scaling argument, which is in good agreement with the numerical results. It also reveals an explicit dependence of the scaling exponents on the Reynolds number. To study the dynamics of the chain, we compute its effective diffusion coefficient D(N), which does not contain Brownian motion. For the range of values of N used here, we find that both the parallel and perpendicular components of D increase with the chain length N, in contrast to the case of thermal diffusion in equilibrium. This is caused by the fluid-driven fluctuations in the internal configuration of the polymer that are magnified as polymer size becomes larger.

Laboratory study of the growth of a turbulent layer of fluid

Stuart Dickinson — 2007-11-07T07:50:27-00:00

Physics of Fluids, Vol. 21, No. 10. (1978), pp. 1698-1701.

An experiment was designed to measure the position of a front separating turbulent and nonturbulent fluid as the front moves away from an oscillating grid located near the plane z=0. The theory predicts D (Kt)1/2, where D is the distance of the front from z=0, t=0 is time at which the oscillation begins, and K is a quantity of the dimensions and character of eddy viscosity, called the ”action” of the idealized plane energy source that replaces the grid in the theoretical model. The experimental results support the theory. Physics of Fluids is copyrighted by The American Institute of Physics. doi:10.1063/1.862110 PACS: 47.25.Cg Additional Information Full Text: [ PDF (215 kB)

Spatially Decaying Turbulence And Its Relation To Mixing Accross Density Interfaces

EJ Hopfinger — 2007-11-07T07:33:59-00:00

J. Fluid Mech, Vol. 78 (1976), pp. 155-175.

Theory of turbulence in a homogeneous fluid induced by an oscillating grid

Robert Long — 2007-11-07T06:54:04-00:00

Physics of Fluids, Vol. 21, No. 10. (1978), pp. 1887-1888.

A theoretical model of steady turbulence caused by an oscillating grid in a box of homogeneous fluid agrees fairly well with observations of root-mean-square velocity and integral length scale. In the unsteady case the depth of the turbulent layer increases as the square root of time. Physics of Fluids is copyrighted by The American Institute of Physics. doi:10.1063/1.862087 PACS: 47.25.Cg Additional Information Full Text: [ PDF (159 kB)

Oscillating-grid turbulence including effects of rotation

SC Dickinson — 2007-11-07T06:50:00-00:00

J. Fluid Mech, Vol. 126 (1983), pp. 315-333.

Experiments were performed to investigate some aspects of turbulence in rotating and non-rotating fluid systems where the turbulence was induced by a horizontal grid oscillating vertically. An earlier theory by the second author made use of a planar source of energy, which appeared to be similar to the energy source of the grid, in determining the characteristics of the turbulence at points some distance away. The simplicity of the theory was in the parameterization of the grid ‘action’ by a single quantity K, with dimensions and characteristics of eddy viscosity. The experimental results provide additional confirmation of the theory in the non-rotating case, and indicate the usefulness of the idealized energy source in the rotating case. In the latter, we measured the propagation of the front separating disturbed and undisturbed fluid, moving along the axis of rotation. The thickness d(t) of the disturbed region increases at first as (Kt)½, as in a non-rotating fluid, until the Rossby number K/Ωd2k becomes of order unity. Beyond this the disturbances are wavelike and rotationally dominated, and the thickness now increases linearly with time, yielding a speed of propagation for the front proportional to the wave speed (KΩ)½. Finally, the disturbances reach the bottom and the vessel is in statistical steady state. Then a region of thickness dk independent of time is found, and it contains motion that resembles ordinary, three-dimensional turbulence. dk [similar] (K/Ω)½ is analogous to the depth of the turbulent Ekman layer H [similar] (K/Ω)½, where K is taken as an eddy viscosity. McEwan constructed a similar rotating experiment, although with a different energy source, and observed vortices parallel to the axis of rotation, provided that the Rossby number was less than a critical value. Our observations and theory indicate that the disappearance of the vortices corresponds to h < dk, where h is the total depth of the fluid. At that point, the whole tank is filled with three-dimensional turbulence.

An experimental test of Corrsin's conjecture and some related ideas

Søren Ott — 2005-06-14T20:00:34-00:00

New Journal of Physics, Vol. 7, No. 1. (June 2005), 142.

Study of two-phase flows in reduced gravity using ground based experiments

S Vasavada — 2007-09-01T13:38:39-00:00

Experiments in Fluids, Vol. 43, No. 1. (July 2007), pp. 53-75.

Turbulent Transport of Material Particles: An Experimental Study of Finite Size Effects

Nauman Qureshi — 2007-10-31T22:14:47-00:00

Physical Review Letters, Vol. 99, No. 18. (2007)

We present experimental Lagrangian statistics of finite sized, neutrally bouyant, particles transported in an isotropic turbulent flow. The particle's diameter is varied over turbulent inertial scales. Finite size effects are shown not to be trivially related to velocity intermittency. The global shape of the particle's acceleration probability density functions is not found to depend significantly on its size while the particle's acceleration variance decreases as it becomes larger in quantitative agreement with the classical k-7/3 scaling for the spectrum of Eulerian pressure fluctuations in the carrier flow.

Unsteady aerodynamic forces estimation on a square cylinder by TR-PIV

D Kurtulus — 2007-03-01T05:56:52-00:00

Experiments in Fluids, Vol. 42, No. 2. (February 2007), pp. 185-196.

Generating topological chaos in lid-driven cavity flow

Mark Stremler — 2007-10-16T20:07:07-00:00

Physics of Fluids, Vol. 19, No. 10. (2007)

Periodic motion of three stirrers in a two-dimensional flow can lead to chaotic transport of the surrounding fluid. For certain stirrer motions, the generation of chaos is guaranteed solely by the topology of that motion and continuity of the fluid. Work in this area has focused largely on using physical rods as stirrers, but the theory also applies when the “stirrers” are passive fluid particles. We demonstrate the occurrence of topological chaos for Stokes flow in a two-dimensional lid-driven cavity without internal rods. This approach to stirring can enhance mixing relative to a “standard” chaos-generating lid-driven cavity flow. ©2007 American Institute of Physics

Particle-fluid interactions in grid-generated turbulence

C Poelma — 2007-10-10T19:09:18-00:00

J. Fluid Mech, Vol. 589 (2007), pp. 315-351.

The effect of small particles on decaying grid-generated turbulence is studied experimentally. Using a two-camera system, instantaneous fluid-phase and particle-phase measurements can be obtained simultaneously. The data obtained with this system are used to study the decay behaviour of the turbulent flow. The role of particle size, particle density and volume load is studied in a number of different cases. These cases are chosen so that the individual role of these parameters can systematically be evaluated. Addition of particles to the flow has significant effects on the decaying turbulence: first, the onset of the turbulent decay appears to shift upstream; second, the flow becomes anisotropic as it develops downstream. The latter is observed as an increase in integral length scale in the vertical direction. The rate at which the flow becomes anisotropic can be predicted using a new parameter: the product of the non-dimensional number density and the Stokes number (referred to as the ‘Stokes load’). This parameter, combining the relevant fluid and particle characteristics, is a measure for the energy redistribution leading to anisotropy. In addition to redistributing energy, the particles also produce turbulence. However, this only becomes evident when the grid-generated turbulence has decayed sufficiently, relatively far downstream of the grid. The turbulence production by particles can also account for the observed decrease in slope of the power spectrum, which leads to a ‘cross-over’ effect. The production of turbulence by the particles can be predicted using a model for the momentum deficit of the particle wakes. The validity of this approach is confirmed using conditional sampling of the fluid velocity field around the particles.

Velocity and temperature derivatives in high- Reynolds-number turbulent flows in the atmospheric surface layer. Part 3. Temperature and joint statistics of temperature and velocity derivatives

G Gulitski — 2007-10-10T19:06:52-00:00

J. Fluid Mech, Vol. 589 (2007), pp. 103-123.

Velocity field of a bluff-body wake

Rong Huang — 2007-10-02T11:16:46-00:00

Journal of Wind Engineering and Industrial Aerodynamics, Vol. 85, No. 1. (March 2000), pp. 31-45.

The characteristics of shear-layer vortex shedding and toroidal wake behind a circular disc are experimentally studied. Five characteristic flow structures, laminar, subcritical, transitional, supercritical, and turbulent modes, are identified in the shear layer evolving from the edge of the disk. The Strouhal numbers of the vortex shedding are about 0.12 and 0.20 in the subcritical and supercritical shear layers, respectively. The Taylor integral length scales of the shed vortices in the subcritical and supercritical shear layers are about one and 0.5 disc diameters, respectively. The flow patterns, recirculation length, as well as turbulence properties are closely related to the characteristic modes of shear-layer structures in different ranges of Reynolds numbers. The measured distributions of Reynolds stresses show that the simple Boussinesq approximation of gradient-type stress model is inappropriate for this flow field. The intensity of turbulence fluctuation superimposed on the vortices dominates the distributions of the Reynolds stresses.

Tomographic particle image velocimetry

G Elsinga — 2007-10-01T20:46:21-00:00

Experiments in Fluids, Vol. 41, No. 6. (1 December 2006), pp. 933-947.

Abstract This paper describes the principles of a novel 3D PIV system based on the illumination, recording and reconstruction of tracer particles within a 3D measurement volume. The technique makes use of several simultaneous views of the illuminated particles and their 3D reconstruction as a light intensity distribution by means of optical tomography. The technique is therefore referred to as tomographic particle image velocimetry (tomographic-PIV). The reconstruction is performed with the MART algorithm, yielding a 3D array of light intensity discretized over voxels. The reconstructed tomogram pair is then analyzed by means of 3D cross-correlation with an iterative multigrid volume deformation technique, returning the three-component velocity vector distribution over the measurement volume. The principles and details of the tomographic algorithm are discussed and a parametric study is carried out by means of a computer-simulated tomographic-PIV procedure. The study focuses on the accuracy of the light intensity field reconstruction process. The simulation also identifies the most important parameters governing the experimental method and the tomographic algorithm parameters, showing their effect on the reconstruction accuracy. A computer simulated experiment of a 3D particle motion field describing a vortex ring demonstrates the capability and potential of the proposed system with four cameras. The capability of the technique in real experimental conditions is assessed with the measurement of the turbulent flow in the near wake of a circular cylinder at Reynolds 2,700.

Holographic particle image velocimetry system for measurements of hairpin vortices in air channel flow

A Svizher — 2007-10-01T20:41:36-00:00

Experiments in Fluids, Vol. 40, No. 5. (26 May 2006), pp. 708-722.

Abstract A holographic particle image velocimetry system for investigating hairpin vortices, artificially generated in a subcritical plane Poiseuille air flow, is presented. The optical setup is a modified version of the hybrid scheme, previously employed in turbulent water flows. Accordingly, separate reconstruction of holograms, successively recorded on the same photoplate, is provided by using two reference beams. The positioning of the photoplate within the image of the sample volume accompanied by special alignment procedures, minimizes the apparent displacement caused by the misalignment of the reconstruction waves. A novel method is employed for detecting in-focus particles. Testing the system with a fixed 5 μm diameter wire, results in a corresponding 3D wire image having a diameter of ≈25 μm. Finally, the instantaneous topology and 3D distribution of the two velocity components associated with the hairpin vortex are presented.

Microscopic particle image velocimetry measurements of transition to turbulence in microscale capillaries

Natrajan — 2007-09-01T13:38:39-00:00

Experiments in Fluids, Vol. 43, No. 1. (July 2007), pp. 1-16.

Dynamic Multiscaling in Turbulence

Rahul Pandit — 2007-09-07T18:39:51-00:00

(6 Sep 2007)

We give an overview of the progress that has been made in recent years in understanding the dynamic multiscaling of homogeneous, isotropic turbulence and related problems. We emphasise the similarity of this problem with the dynamic scaling of time-dependent correlation functions in the vicinity of a critical point in, e.g., a spin system. The universality of dynamic-multiscaling exponents in fluid turbulence is explored by detailed simulations of the GOY shell model for fluid turbulence.

A method for automatic particle tracking in a three-dimensional flow field

R Racca — 2007-10-01T10:04:38-00:00

Exp. Fluids, Vol. 6 (1988), pp. 25-32.

Application of image processing to the analysis of three-dimensional flow fields.

T Chang — 2007-10-01T10:04:17-00:00

Opt. Engng., Vol. 23 (1983), pp. 283-287.

Flow and Turbulence in a Stirred Tank

LA Cutter — 2007-10-01T10:03:59-00:00

AIChE J., Vol. 12 (1966)

A CFD and PTV steady flow investigation in an anatomically accurate abdominal aortic aneurysm

E Boutsianis — 2007-10-01T10:03:16-00:00

(2006)

Pair Dispersion in Turbulence

M Bourgoin — 2007-10-01T10:00:52-00:00

Science, Vol. 311 (2006), pp. 835-838.

An experimental investigation: backwards and forwards relative dispersion in turbulent flow

J Berg — 2007-10-01T10:00:17-00:00

Phys. Rev. E, Vol. 74, No. 1. (2006)

An experimental examination of the large-eddy equilibrium hypothesis

IS Gartshore — 2007-09-29T16:00:19-00:00

J. Fluid Mech., Vol. 24 (1966), pp. 89-98.

Kinetic energy in grid turbulence: comparison between data and theory

Jg Janzen — 2007-09-28T23:35:25-00:00

J. Braz. Soc. Mech. Sci.& Eng., Vol. 25, No. 4. (2003)

The properties of turbulence induced in a viscous fluid by oscillating a grid within it are investigated. Vertical and horizontal components of fluctuating velocities are measured using the Digital Particle Image Velocimetry technique (DPIV). Vertical profiles of turbulent kinetic energy k, obtained from the fluctuating velocities, are presented and compared with theoretical predictions obtained using the k-e turbulence model.