The Experts below are selected from a list of 12126 Experts worldwide ranked by ideXlab platform

Pierre Moretto - One of the best experts on this subject based on the ideXlab platform.

  • Walking dynamic similarity induced by a combination of Froude and Strouhal Dimensionless Numbers: Modela-w
    Gait and Posture, 2015
    Co-Authors: David Villeger, Antony Costes, Bruno Watier, Pierre Moretto
    Abstract:

    The aim of this study was to assess the accuracy of a new Dimensionless number associating Froude (Nfr) and Strouhal (Str) called Modela-w to induce walking dynamic similarity among humans of different sizes. Nineteen subjects walked in three experimental conditions: (i) constant speed, (ii) similar speed (Nfr) and (iii) similar speed and similar step frequency (Modela-w). The dynamic similarity was evaluated from scale factors computed with anthropometric, temporal, kinematic and kinetic data and from the decrease of the variability of the parameters expressed in their Dimensionless form. Over a total of 36 dynamic parameters, dynamic similarity from scale factors was met for 11 (mean r = 0.51), 22 (mean r = 0.52) and 30 (mean r = 0.69) parameters in the first, the second and the third experimental conditions, respectively. Modela-w also reduced the variability of the Dimensionless preceding parameters compared to the other experimental conditions. This study shows that the combination of Nfr and Str called Modela-w ensures dynamic similarity between different-sized subjects and allows scientists to impose similar experimental conditions removing all anthropometric effects.

  • Modela-r as a Froude and Strouhal Dimensionless Numbers combination for dynamic similarity in running
    Journal of Biomechanics, 2014
    Co-Authors: David Villeger, Antony Costes, Bruno Watier, Pierre Moretto
    Abstract:

    The aim of this study was to test the hypothesis t hat running at fixed fractions of Froude (Nfr) and Strouhal (Str) Dimensionless numbe rs combinations induce dynamic similarity between humans of different sizes. Ninet een subjects ran in three experimental conditions, i) constant speed, ii) similar speed (N fr) and iii) similar speed and similar step frequency (Nfr and Str combination). In addition to anthropometric data, temporal, kinematic and kinetic parameters were assessed at each stage to measure dynamic similarity informed by dimensional scale factors and by the decrease of Dimensionless mechanical parameter variability. Over a total of 54 dynamic parameters, dynamic similarity from scale factors was met for 16 (mean r = 0.51), 32 (mean r = 0.49) and 52 (mean r = 0.60) parameters in the first, the second and the third experimental conditions, r espectively. The variability of the Dimensionless preceding parameters was lower in the third condition than in the others. This study shows that the combination of Nfr and Str, computed from the Dimensionless energy ratio at the center of gravity (Modela-r) ensures d ynamic similarity between different-sized subjects. The relevance of using similar experiment al conditions to compare mechanical Dimensionless parameters is also proved and will hi ghlight the study of running techniques, or equipment, and will allow the identification of abnormal and pathogenic running patterns. Modela-r may be adapted to study other abilities requiring b ounces in human or animal locomotion or to conduct investigations in comparat ive biomechanics.

  • Dynamic similarity during human running: about Froude and Strouhal Dimensionless Numbers.
    Journal of biomechanics, 2009
    Co-Authors: Nicolas Delattre, Mario A. Lafortune, Pierre Moretto
    Abstract:

    Abstract Dynamic similarity is a widely used concept in the fluid mechanics field, and consists in placing two different-sized systems in equivalent experimental conditions. This enables removal of the effects of size and prediction of the behavior of a full size system from a scale model. The aim of this study was to test whether the Froude number (Nfr) or the Strouhal number (Str) could be used as a criterion for dynamic similarity during running. Fifteen male subjects ran barefoot on a runway in three experimental conditions (i) all subjects ran at the same speed V=3.5 m s−1; (ii) the speed was determined from Nfr; (iii) the stride frequency was determined from Str. Antero-posterior (Fy) and vertical (Fz) ground reaction force components were assessed. The similarity between the subjects was analysed from scale factor sets computed from anthropometric and kinetic data. The use of Str implied strong inter-subject similarity for temporal parameters (mean r=0.96, time to Fz peak, time to Fy braking peak, Fy zero fore–aft shear, time to Fy propulsive peak) while Nfr induced fewer and lower similarities (mean r=0.75, Fy zero fore–aft shear, time to Fy propulsive peak, Fy braking impulse) that only concerned antero-posterior parameters. This study brought experimental evidence that neither Nfr nor Str were sufficient for dynamic similarity during running, but that each of them made its own contribution. These findings suggested that the concomitant use of Nfr and Str should be assessed to induce inter-subject dynamic similarity during running.

Antonio Delgado - One of the best experts on this subject based on the ideXlab platform.

  • numerical simulations of fluid dynamics in carrier structures for catalysis characterization and need for optimization
    Chemical Engineering Science, 2014
    Co-Authors: T Horneber, Cornelia Rauh, Antonio Delgado
    Abstract:

    Abstract 3D fluid dynamic numerical simulations of different structured open-cell foams are presented: a cubic lattice, the tetrakaidecahedron geometry (Kelvin cell geometry), and the diamond structure. The simulations are done with the open-source software OpenFOAM. Beneath the pressure drops of the different structures, which are compared using Dimensionless Numbers such as Reynolds number and Euler number, also the development of velocity and its frequency distribution, as an important parameter for chemical reactions, are evaluated. As a main result, the diamond structure provides good conditions with respect to dwell time distributions for the underlying chemical reaction. All the results give a deep knowledge in terms of the underlying principles and optimization approaches.

  • fluid dynamic characterisation of porous solids in catalytic fixed bed reactors
    Microporous and Mesoporous Materials, 2012
    Co-Authors: T Horneber, Cornelia Rauh, Antonio Delgado
    Abstract:

    Abstract 3D numerical simulations of structured open-cell foams, more precisely the tetrakaidecahedron geometry (Kelvin cell geometry) are presented. The velocity and pressure field for a single cell with varied surface roughness and the whole reactor with the same pore size are calculated in order to show the influence of the surface roughness regarding the pressure drop and the influence of the length of the whole reactor regarding the velocity development, respectively. The numerical results are compared using Dimensionless Numbers such as Reynolds number, Euler number and friction factor.

T Horneber - One of the best experts on this subject based on the ideXlab platform.

  • numerical simulations of fluid dynamics in carrier structures for catalysis characterization and need for optimization
    Chemical Engineering Science, 2014
    Co-Authors: T Horneber, Cornelia Rauh, Antonio Delgado
    Abstract:

    Abstract 3D fluid dynamic numerical simulations of different structured open-cell foams are presented: a cubic lattice, the tetrakaidecahedron geometry (Kelvin cell geometry), and the diamond structure. The simulations are done with the open-source software OpenFOAM. Beneath the pressure drops of the different structures, which are compared using Dimensionless Numbers such as Reynolds number and Euler number, also the development of velocity and its frequency distribution, as an important parameter for chemical reactions, are evaluated. As a main result, the diamond structure provides good conditions with respect to dwell time distributions for the underlying chemical reaction. All the results give a deep knowledge in terms of the underlying principles and optimization approaches.

  • fluid dynamic characterisation of porous solids in catalytic fixed bed reactors
    Microporous and Mesoporous Materials, 2012
    Co-Authors: T Horneber, Cornelia Rauh, Antonio Delgado
    Abstract:

    Abstract 3D numerical simulations of structured open-cell foams, more precisely the tetrakaidecahedron geometry (Kelvin cell geometry) are presented. The velocity and pressure field for a single cell with varied surface roughness and the whole reactor with the same pore size are calculated in order to show the influence of the surface roughness regarding the pressure drop and the influence of the length of the whole reactor regarding the velocity development, respectively. The numerical results are compared using Dimensionless Numbers such as Reynolds number, Euler number and friction factor.

David Villeger - One of the best experts on this subject based on the ideXlab platform.

  • Walking dynamic similarity induced by a combination of Froude and Strouhal Dimensionless Numbers: Modela-w
    Gait and Posture, 2015
    Co-Authors: David Villeger, Antony Costes, Bruno Watier, Pierre Moretto
    Abstract:

    The aim of this study was to assess the accuracy of a new Dimensionless number associating Froude (Nfr) and Strouhal (Str) called Modela-w to induce walking dynamic similarity among humans of different sizes. Nineteen subjects walked in three experimental conditions: (i) constant speed, (ii) similar speed (Nfr) and (iii) similar speed and similar step frequency (Modela-w). The dynamic similarity was evaluated from scale factors computed with anthropometric, temporal, kinematic and kinetic data and from the decrease of the variability of the parameters expressed in their Dimensionless form. Over a total of 36 dynamic parameters, dynamic similarity from scale factors was met for 11 (mean r = 0.51), 22 (mean r = 0.52) and 30 (mean r = 0.69) parameters in the first, the second and the third experimental conditions, respectively. Modela-w also reduced the variability of the Dimensionless preceding parameters compared to the other experimental conditions. This study shows that the combination of Nfr and Str called Modela-w ensures dynamic similarity between different-sized subjects and allows scientists to impose similar experimental conditions removing all anthropometric effects.

  • Modela-r as a Froude and Strouhal Dimensionless Numbers combination for dynamic similarity in running
    Journal of Biomechanics, 2014
    Co-Authors: David Villeger, Antony Costes, Bruno Watier, Pierre Moretto
    Abstract:

    The aim of this study was to test the hypothesis t hat running at fixed fractions of Froude (Nfr) and Strouhal (Str) Dimensionless numbe rs combinations induce dynamic similarity between humans of different sizes. Ninet een subjects ran in three experimental conditions, i) constant speed, ii) similar speed (N fr) and iii) similar speed and similar step frequency (Nfr and Str combination). In addition to anthropometric data, temporal, kinematic and kinetic parameters were assessed at each stage to measure dynamic similarity informed by dimensional scale factors and by the decrease of Dimensionless mechanical parameter variability. Over a total of 54 dynamic parameters, dynamic similarity from scale factors was met for 16 (mean r = 0.51), 32 (mean r = 0.49) and 52 (mean r = 0.60) parameters in the first, the second and the third experimental conditions, r espectively. The variability of the Dimensionless preceding parameters was lower in the third condition than in the others. This study shows that the combination of Nfr and Str, computed from the Dimensionless energy ratio at the center of gravity (Modela-r) ensures d ynamic similarity between different-sized subjects. The relevance of using similar experiment al conditions to compare mechanical Dimensionless parameters is also proved and will hi ghlight the study of running techniques, or equipment, and will allow the identification of abnormal and pathogenic running patterns. Modela-r may be adapted to study other abilities requiring b ounces in human or animal locomotion or to conduct investigations in comparat ive biomechanics.

André B. De Haan - One of the best experts on this subject based on the ideXlab platform.

  • Gas holdup, axial dispersion, and mass transfer studies in bubble columns
    Industrial & Engineering Chemistry Research, 2012
    Co-Authors: Mayank Shah, Anton A. Kiss, Edwin Zondervan, John Van Der Schaaf, André B. De Haan
    Abstract:

    This article presents an extensive study on the gas holdup, axial liquid dispersion, and mass transfer for packed, trayed, and empty bubble columns. Four types of structured packings (Super-Pak, Flexipac, Mellapak, and Gauze) and two types of perforated partition trays (with 25% and 40% tray open area) were used to characterize the packed and trayed bubble columns, respectively. It was observed that the gas holdup and mass transfer characteristics of the packed and trayed bubble columns are superior to those of an empty bubble column, while the axial dispersion coefficients are much lower. This article discusses in detail the effect of the liquid and gas flow rates, liquid-phase viscosity, and type of internals. Additionally, experimental data of the packed, trayed, and empty bubble column are correlated by Dimensionless Numbers. Novel empirical correlations are proposed for the gas holdup, Bodenstein number (for the axial dispersion coefficient), and Stanton number (for the volumetric mass transfer coefficient), as a function of the Froude and Galileo Dimensionless Numbers.