The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Ivan Marusic - One of the best experts on this subject based on the ideXlab platform.
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High Reynolds Number wall turbulence
Annual Review of Fluid Mechanics, 2011Co-Authors: Alexander Smits, B. J. Mckeon, Ivan MarusicAbstract:We review wall-bounded turbulent flows, particularly High–Reynolds Number, zero–pressure gradient boundary layers, and fully developed pipe and channel flows. It is apparent that the approach to an asymptotically High–Reynolds Number state is slow, but at a sufficiently High Reynolds Number the log law remains a fundamental part of the mean flow description. With regard to the coherent motions, very-large-scale motions or superstructures exist at all Reynolds Numbers, but they become increasingly important with Reynolds Number in terms of their energy content and their interaction with the smaller scales near the wall. There is accumulating evidence that certain features are flow specific, such as the constants in the log law and the behavior of the very large scales and their interaction with the large scales (consisting of vortex packets). Moreover, the refined attached-eddy hypothesis continues to provide an important theoretical framework for the structure of wall-bounded turbulent flows.
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High–Reynolds Number Wall Turbulence
Annual Review of Fluid Mechanics, 2011Co-Authors: Alexander J. Smits, B. J. Mckeon, Ivan MarusicAbstract:We review wall-bounded turbulent flows, particularly High?Reynolds Number, zero?pressure gradient boundary layers, and fully developed pipe and channel flows. It is apparent that the approach to an asymptotically High?Reynolds Number state is slow, but at a sufficiently High Reynolds Number the log law remains a fundamental part of the mean flow description. With regard to the coherent motions, very-large-scale motions or superstructures exist at all Reynolds Numbers, but they become increasingly important with Reynolds Number in terms of their energy content and their interaction with the smaller scales near the wall. There is accumulating evidence that certain features are flow specific, such as the constants in the log law and the behavior of the very large scales and their interaction with the large scales (consisting of vortex packets). Moreover, the refined attached-eddy hypothesis continues to provide an important theoretical framework for the structure of wall-bounded turbulent flows.
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High Reynolds Number effects in wall turbulence
International Journal of Heat and Fluid Flow, 2010Co-Authors: Ivan Marusic, Romain Mathis, Nicholas HutchinsAbstract:A review of recent advances in the study of High Reynolds Number turbulent boundary layers is given. The emergent regime of very large-scale structures in the logarithmic region and their subsequent influence on the near-wall cycle challenges many of the previously held assumptions regarding scaling of turbulent boundary layers at High Reynolds Numbers. Experimental results are presented to illustrate the superimposition of large-scale energy onto the near-wall cycle, together with an interaction well described by an amplitude modulation effect. Both phenomena are shown to increase in magnitude (as compared to viscous-scaled events) as Reynolds Number increases. These observations lead to a possible model for a statistically representative near-wall velocity signal (giving accurate energy spectra) based on a given filtered velocity signal from the log region of a High Reynolds Number turbulent flow.
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Some predictions of the attached eddy model for a High Reynolds Number boundary layer
Philosophical transactions. Series A Mathematical physical and engineering sciences, 2007Co-Authors: T. B. Nickels, Nicholas Hutchins, Ivan Marusic, S Hafez, Min S ChongAbstract:Many flows of practical interest occur at High Reynolds Number, at which the flow in most of the boundary layer is turbulent, showing apparently random fluctuations in velocity across a wide range of scales. The range of scales over which these fluctuations occur increases with the Reynolds Number and hence High Reynolds Number flows are difficult to compute or predict. In this paper, we discuss the structure of these flows and describe a physical model, based on the attached eddy hypothesis, which makes predictions for the statistical properties of these flows and their variation with Reynolds Number. The predictions are shown to compare well with the results from recent experiments in a new purpose-built High Reynolds Number facility. The model is also shown to provide a clear physical explanation for the trends in the data. The limits of applicability of the model are also discussed.
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Oil film interferometry in High Reynolds Number turbulent boundary layers
2007Co-Authors: Ivan Marusic, Nicholas Hutchins, Jason Monty, Min S ChongAbstract:There is continuing debate regarding the validity of skin friction measurements that are dependent on the functional form of the mean velocity profile, for example, the Clauser chart method. This has brought about the need for independent and direct measures of wall shear stress, tw. Of the independent methods to measure tw, oil film interferometry is the most promising, and it has been extensively used recently at low and moderately High Reynolds Number. The technique uses interferometry to measure the thinning rate of an oil film, which is linearly related to the level of shear stress acting on the oil film. In this paper we report on the use of this technique in a High Reynolds Number boundary layer up to Rq = 50,000. Being an independent measure of tw, the oil film measurement can be used as a means to validate more conventional techniques, such as the Preston tube and Clauser chart at these High Reynolds Numbers. The oil-film measurement is validated by making comparative measurements of tw in a large-scale fully-developed channel flow facility where the skin friction is known from the pressure gradient along the channel
Yoshiyuki Tsuji - One of the best experts on this subject based on the ideXlab platform.
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Further experiments for mean velocity profile of pipe flow at High Reynolds Number
Physics of Fluids, 2018Co-Authors: Noriyuki Furuichi, Yoshiya Terao, Y. Wada, Yoshiyuki TsujiAbstract:This paper reports further experimental results obtained in High Reynolds Number actual flow facility in Japan. The experiments were performed in a pipe flow with water, and the friction Reynolds Number was varied up to Reτ = 5.3 × 104. This High Reynolds Number was achieved by using water as the working fluid and adopting a large-diameter pipe (387 mm) while controlling the flow rate and temperature with High accuracy and precision. The streamwise velocity was measured by laser Doppler velocimetry close to the wall, and the mean velocity profile, called log-law profile U+ = (1/κ) ln(y+) + B, is especially focused. After careful verification of the mean velocity profiles in terms of the flow rate accuracy and an evaluation of the consistency of the present results with those from previously measurements in a smaller pipe (100 mm), it was found that the value of κ asymptotically approaches a constant value of κ = 0.384.This paper reports further experimental results obtained in High Reynolds Number actual flow facility in Japan. The experiments were performed in a pipe flow with water, and the friction Reynolds Number was varied up to Reτ = 5.3 × 104. This High Reynolds Number was achieved by using water as the working fluid and adopting a large-diameter pipe (387 mm) while controlling the flow rate and temperature with High accuracy and precision. The streamwise velocity was measured by laser Doppler velocimetry close to the wall, and the mean velocity profile, called log-law profile U+ = (1/κ) ln(y+) + B, is especially focused. After careful verification of the mean velocity profiles in terms of the flow rate accuracy and an evaluation of the consistency of the present results with those from previously measurements in a smaller pipe (100 mm), it was found that the value of κ asymptotically approaches a constant value of κ = 0.384.
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High Reynolds Number Experimental Facilities for Turbulent Pipe Flow at NMIJ
Springer Proceedings in Physics, 2017Co-Authors: Noriyuki Furuichi, Yoshiya Terao, Yoshiyuki TsujiAbstract:In this paper, we report on High Reynolds Number and Highly accurate experimental facilities for turbulent pipe flow established by the National Metrology Institute of Japan (NMIJ). One of the facilities, called the High Reynolds Number actual flow facility (Hi-Reff), is capable of handling a maximum bulk Reynolds Number of \({Re}_\mathrm{D} = 2.0 \times 10^7\). The most remarkable feature of this facility is its Highly accurate flow rate measurements. The expanded uncertainty of the volumetric flow rate is estimated as 0.040–0.10%. Such a low flow rate measurement uncertainty contributes to extremely accurate estimations of inner-scale variables such as friction velocity. This paper presents the details and advantages provided by this NMIJ facility in relation to turbulent pipe experiments.
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High-Reynolds-Number experiments: the challenge of understanding universality in turbulence
Fluid Dynamics Research, 2009Co-Authors: Yoshiyuki TsujiAbstract:At the 40th anniversary meeting of the Japan Society of Fluid Mechanics, the author presented the results obtained in three High-Reynolds-Number experiments. The results dealt with issues such as the turbulence energy spectrum, the mean velocity profile in the boundary layer and the skin friction coefficient of a flat plate. This publication presents a summary of the first topic, and makes a case for the necessity of High-Reynolds-Number experiments by attempting to answer the question 'Why do we need High-Reynolds-Number experiments?'
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Special issue on High Reynolds Number Experiments
Fluid Dynamics Research, 2009Co-Authors: Yoshiyuki TsujiAbstract:Why do we need High Reynolds Number experiments? This is a question I sometimes ask myself. You may have your own answer to this question, but those people who are doing numerical simulation, theorists and experimentalists should each have their own answer. In this special issue, the leading experts present their new ideas or original experiments in response to this question. Personally, I think that High Reynolds Number experiments are necessary to seek novel physics in turbulence. For instance, we do not have much information about the Lagrangian quantities. You can understand this point by reading the article 'Why we need experiments at High Reynolds Numbers' by Warhaft. High Reynolds Number experiments are also indispensable to reveal the universality of turbulence. One famous example is Kolmogorov's similarity hypothesis; another is the logarithmic velocity profile derived by von Karman. They become clearly satisfied as Reynolds Number increases. But there have been many arguments over these problems even in this century, thus we still have to make an effort to reveal the nature of turbulence. Kolmogorov's idea is based on small scale physics; in this sense, Mouri and Hori's paper 'Vortex tubes in turbulence velocity fields at High Reynolds Numbers' is a contribution to understanding how eddy size is defined and scaled. In contrast to the universality in the small scale limit, the large scale anisotropy effect is a key factor in considering the local isotropic condition even in grid turbulence. This point is discussed by Kurian and Fransson in 'Grid generated turbulence revisited'. The mean velocity profile over a flat plate in a zero-pressure gradient boundary layer is discussed with the help of a composite profile in 'Criteria for assessing experiments in zero pressure gradient boundary layers' by Chauhan et al. Related important physical quantities are computed, and how they are scaled against Reynolds Number is discussed, analyzing the vast experimental database available, which is really interesting. The universal velocity profile is usually discussed through the normalization of the velocity and wall distance with the viscous scales. Therefore, an accurate determination of the wall shear stress is indispensable for this procedure. Zanoun et al tried to measure it by oil film interferometry in the paper 'Refined cf relation for turbulent channels and consequences for High-Re experiments', and Mori et al performed it by using the towing tank in 'Direct total skin-friction measurement of a flat plate in zero-pressure-gradient boundary layers'. In this issue we would like to introduce two new experimental facilities which can help us to tackle unresolved problems in turbulence. Talamelli et al report a response to my initial question. This is systematically mentioned in 'CICLoPE—a response to the need for High Reynolds Number experiments', and they present the excellent new facility which is under construction. Yoshioka et al used the towing wind facility and simulated the Highly complex flow between steady ground and a moving model, which is discussed in 'Measurement of ground effect and boundary-layer transition by towing wind tunnel'. It is a unique experiment. And this facility promises to proceed with High Reynolds Number experiments. Finally, I will introduce the spirit of experiment, which is carved on the plate at Ettore Majorana Centenary, Erice, Italy: ''We experimentalists are not like theorists; the originality of an idea is not for being printed in a paper, but for being shown in the implementation of an original experiment. Patrick M. S. Blackett, London 1962.''
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Shear Stress and Dissipation Intermittency in High-Reynolds-Number Turbulence
IUTAM Symposium on Geometry and Statistics of Turbulence, 2001Co-Authors: Yoshiyuki TsujiAbstract:Energy dissipation and instantaneous shear stress fluctuations are considered for High-Reynolds-Number (up to R λ ≈ 104) turbulent flow field using the concept of maximum norm.
M.s. Howe - One of the best experts on this subject based on the ideXlab platform.
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Stability of High Reynolds Number flow past a circular aperture
Proceedings of the Royal Society of London. Series A: Mathematical Physical and Engineering Sciences, 1999Co-Authors: Sheryl M. Grace, Trevor H. Wood, M.s. HoweAbstract:An analysis is made of the canonical problem of flow at very High Reynolds Number past a circular aperture in a thin rigid wall. The motion is incompressible, and the shear layer over the aperture ...
Thierry Coupez - One of the best experts on this subject based on the ideXlab platform.
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Stabilized finite element method for incompressible flows with High Reynolds Number
Journal of Computational Physics, 2010Co-Authors: Elie Hachem, B. Rivaux, T. Kloczko, Hugues Digonnet, Thierry CoupezAbstract:In the following paper, we discuss the exhaustive use and implementation of stabilization finite element methods for the resolution of the 3D time-dependent incompressible Navier-Stokes equations. The proposed method starts by the use of a finite element variational multiscale (VMS) method, which consists in here of a decomposition for both the velocity and the pressure fields into coarse/resolved scales and fine/unresolved scales. This choice of decomposition is shown to be favorable for simulating flows at High Reynolds Number. We explore the behaviour and accuracy of the proposed approximation on three test cases. First, the lid-driven square cavity at Reynolds Number up to 50,000 is compared with the Highly resolved numerical simulations and second, the lid-driven cubic cavity up to Re=12,000 is compared with the experimental data. Finally, we study the flow over a 2D backward-facing step at Re=42,000. Results show that the present implementation is able to exhibit good stability and accuracy properties for High Reynolds Number flows with unstructured meshes.
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Stabilized nite element method for incompressible ows with High Reynolds Number
2010Co-Authors: Elie Hachem, B. Rivaux, T. Kloczko, Hugues Digonnet, Thierry CoupezAbstract:In the following paper, we discuss the exhaustive use and implementation of stabilization nite element methods for the resolution of the 3D time-dependent incompressible Navier–Stokes equations. The proposed method starts by the use of a nite element variational multiscale (VMS) method, which consists in here of a decomposition for both the velocity and the pressure elds into coarse/resolved scales and ne/unresolved scales. This choice of decomposition is shown to be favorable for simulating ows at High Reynolds Number. We explore the behaviour and accuracy of the proposed approximation on three test cases. First, the lid-driven square cavity at Reynolds Number up to 50,000 is compared with the Highly resolved numerical simulations and second, the lid-driven cubic cavity up to Re = 12,000 is compared with the experimental data. Finally, we study the ow over a 2D backward-facing step at Re = 42,000. Results show that the present implementation is able to exhibit good stability and accuracy properties for High Reynolds Number ows with unstructured meshes.
Naeem Ali - One of the best experts on this subject based on the ideXlab platform.
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Numerical study of hydromagnetic axisymmetric peristaltic flow at High Reynolds Number and wave Number.
Biophysical reviews, 2019Co-Authors: A. H. Hamid, Tariq Javed, Naeem AliAbstract:The computational study of MHD peristaltic motion is investigated for axisymmetric flow problem. The developed model is present in the form of partial differential equations. Then obtained partial differential equations are transferred into stream-vorticity (ψ − ω) form. Then Galerkin Finite element method is used to find the computational results of governing problem. The current study is compared with the existing well-known results at low Reynolds Number and wave Number. It is revealed that the present results are in well agreement with existing results in the literature. So, it is effective for Higher values of Reynolds Number and wave Number. The variations of streamline are present graphically against High Reynolds Number. It concludes that High Reynolds Number and Hartmann Number increase pressure rise per unit wavelength in positive pumping region sharply.