The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform

Jan Dusek - One of the best experts on this subject based on the ideXlab platform.

  • a single Oblate Spheroid settling in unbounded ambient fluid a benchmark for simulations in steady and unsteady wake regimes
    International Journal of Multiphase Flow, 2021
    Co-Authors: M Moriche, Markus Uhlmann, Jan Dusek
    Abstract:

    Abstract We have performed spectral/spectral-element simulations of a single Oblate Spheroid with small geometrical aspect ratio settling in an unbounded ambient fluid, for a range of Galileo numbers covering the various regimes of motion (steady vertical, steady oblique, vertical periodic and chaotic). The high-fidelity data provided includes particle quantities (statistics in the chaotic case), as well as flow profiles and pressure maps. The reference data can be used as an additional benchmark for other numerical approaches, where a careful grid convergence study for a specific target parameter point is often useful. We further describe an extension of a specific immersed boundary method (Uhlmann, J. Comput. Phys, 209(2):448–476, 2005) to enable the tracking of non-spherical particles. Finally, the reference cases are computed with this immersed boundary method at various spatial and temporal resolutions, and grid convergence is discussed over the various regimes of Spheroidal particle motion. The cross-validation results can serve as a guideline for the design of simulations with the aid of similar non-conforming methods, involving Spheroidal particles with Galileo numbers of O ( 100 ) .

M Moriche - One of the best experts on this subject based on the ideXlab platform.

  • a single Oblate Spheroid settling in unbounded ambient fluid a benchmark for simulations in steady and unsteady wake regimes
    International Journal of Multiphase Flow, 2021
    Co-Authors: M Moriche, Markus Uhlmann, Jan Dusek
    Abstract:

    Abstract We have performed spectral/spectral-element simulations of a single Oblate Spheroid with small geometrical aspect ratio settling in an unbounded ambient fluid, for a range of Galileo numbers covering the various regimes of motion (steady vertical, steady oblique, vertical periodic and chaotic). The high-fidelity data provided includes particle quantities (statistics in the chaotic case), as well as flow profiles and pressure maps. The reference data can be used as an additional benchmark for other numerical approaches, where a careful grid convergence study for a specific target parameter point is often useful. We further describe an extension of a specific immersed boundary method (Uhlmann, J. Comput. Phys, 209(2):448–476, 2005) to enable the tracking of non-spherical particles. Finally, the reference cases are computed with this immersed boundary method at various spatial and temporal resolutions, and grid convergence is discussed over the various regimes of Spheroidal particle motion. The cross-validation results can serve as a guideline for the design of simulations with the aid of similar non-conforming methods, involving Spheroidal particles with Galileo numbers of O ( 100 ) .

Edward Bormashenko - One of the best experts on this subject based on the ideXlab platform.

P. Bénard - One of the best experts on this subject based on the ideXlab platform.

  • an Oblate Spheroid geopotential approximation for global meteorology
    Quarterly Journal of the Royal Meteorological Society, 2014
    Co-Authors: P. Bénard
    Abstract:

    The spherical geopotential approximation used in most meteorological global models assumes a spherical shape for the Earth and its geopotential field. Consequently, the deviation of the geoid surface from a sphere, and the observed meridional variations of the apparent gravity are not represented. These two errors are small but their effect on medium or long-term forecasts is debated because they are systematic and might have cumulative effects. Various formulations with Spheroidal iso-geopotential surfaces have been proposed recently, but none of them combines the advantages of an accurate description for the geopotential field and of horizontal/vertical orthogonal coordinate surfaces. This article proposes a Spheroidal coordinate system which meets these two requirements. The transformation and metric factors are defined analytically. The coordinate system is defined as an approximation of orthogonal horizontal/vertical coordinates in which the vertical lines are not exactly orthogonal to true horizontal surfaces. The consequences of this deviation from orthogonality are quantified and upper bounds for the resulting errors are obtained mathematically, i.e. independently of any arbitrary numerical process. The precision of the coordinate can be made as large as desired by raising the truncation of the Taylor series used to approach its exact value, and it is shown that, in practice, truncation values in the range 5 to 8 are appropriate for global numerical weather prediction.

  • An Oblate‐Spheroid geopotential approximation for global meteorology
    Quarterly Journal of the Royal Meteorological Society, 2013
    Co-Authors: P. Bénard
    Abstract:

    The spherical geopotential approximation used in most meteorological global models assumes a spherical shape for the Earth and its geopotential field. Consequently, the deviation of the geoid surface from a sphere, and the observed meridional variations of the apparent gravity are not represented. These two errors are small but their effect on medium or long-term forecasts is debated because they are systematic and might have cumulative effects. Various formulations with Spheroidal iso-geopotential surfaces have been proposed recently, but none of them combines the advantages of an accurate description for the geopotential field and of horizontal/vertical orthogonal coordinate surfaces. This article proposes a Spheroidal coordinate system which meets these two requirements. The transformation and metric factors are defined analytically. The coordinate system is defined as an approximation of orthogonal horizontal/vertical coordinates in which the vertical lines are not exactly orthogonal to true horizontal surfaces. The consequences of this deviation from orthogonality are quantified and upper bounds for the resulting errors are obtained mathematically, i.e. independently of any arbitrary numerical process. The precision of the coordinate can be made as large as desired by raising the truncation of the Taylor series used to approach its exact value, and it is shown that, in practice, truncation values in the range 5 to 8 are appropriate for global numerical weather prediction.

Markus Uhlmann - One of the best experts on this subject based on the ideXlab platform.

  • a single Oblate Spheroid settling in unbounded ambient fluid a benchmark for simulations in steady and unsteady wake regimes
    International Journal of Multiphase Flow, 2021
    Co-Authors: M Moriche, Markus Uhlmann, Jan Dusek
    Abstract:

    Abstract We have performed spectral/spectral-element simulations of a single Oblate Spheroid with small geometrical aspect ratio settling in an unbounded ambient fluid, for a range of Galileo numbers covering the various regimes of motion (steady vertical, steady oblique, vertical periodic and chaotic). The high-fidelity data provided includes particle quantities (statistics in the chaotic case), as well as flow profiles and pressure maps. The reference data can be used as an additional benchmark for other numerical approaches, where a careful grid convergence study for a specific target parameter point is often useful. We further describe an extension of a specific immersed boundary method (Uhlmann, J. Comput. Phys, 209(2):448–476, 2005) to enable the tracking of non-spherical particles. Finally, the reference cases are computed with this immersed boundary method at various spatial and temporal resolutions, and grid convergence is discussed over the various regimes of Spheroidal particle motion. The cross-validation results can serve as a guideline for the design of simulations with the aid of similar non-conforming methods, involving Spheroidal particles with Galileo numbers of O ( 100 ) .