Effects of initial amplitude and pycnocline thickness on the evolution of mode-2 internal solitary waves

M.H. Cheng, C.M. Hsieh, R.R. Hwang, J.R.C. Hsu

    Research output: Contribution to journalArticle

    3 Citations (Scopus)

    Abstract

    Numerical simulations are performed to investigate the effects of the initial amplitude and pycnocline thickness on the evolutions of convex mode-2 internal solitary waves propagating on the flat bottom. A finite volume method based on a Cartesian grid system is adopted to solve the Navier-Stokes equations using the improved delayed detached eddy simulation turbulent closure model. Mode-2 internal solitary waves (ISWs) are found to become stable at t = 15 s after lifting a vertical sluice gate by a gravity collapse mechanism. Numerical results from three cases of pycnocline thickness reveal the following: (1) the occurrence of a smooth mode-2 ISW when the wave amplitude is small; (2) the PacMan phenomenon for large amplitude waves; and (3) pseudo vortex shedding in the case of very large amplitudes. In general, basic wave properties (wave amplitude, wave speed, vorticity, and wave energy) increase as the wave amplitude increases for a specific value of the pycnocline thickness. Moreover, the pycnocline thickness chiefly determines the core size of a convex mode-2 ISW, while the step depth (that generates an initial wave amplitude) and offset in pycnocline govern the waveform type during its propagation on the flat bottom.

    Original languageEnglish
    Article number042101
    JournalPhysics of Fluids
    Volume30
    Issue number4
    DOIs
    Publication statusPublished - 1 Apr 2018

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    solitary waves
    vortex shedding
    finite volume method
    Navier-Stokes equation
    vorticity
    closures
    waveforms
    simulation
    grids
    occurrences
    vortices
    gravitation
    propagation

    Cite this

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    title = "Effects of initial amplitude and pycnocline thickness on the evolution of mode-2 internal solitary waves",
    abstract = "Numerical simulations are performed to investigate the effects of the initial amplitude and pycnocline thickness on the evolutions of convex mode-2 internal solitary waves propagating on the flat bottom. A finite volume method based on a Cartesian grid system is adopted to solve the Navier-Stokes equations using the improved delayed detached eddy simulation turbulent closure model. Mode-2 internal solitary waves (ISWs) are found to become stable at t = 15 s after lifting a vertical sluice gate by a gravity collapse mechanism. Numerical results from three cases of pycnocline thickness reveal the following: (1) the occurrence of a smooth mode-2 ISW when the wave amplitude is small; (2) the PacMan phenomenon for large amplitude waves; and (3) pseudo vortex shedding in the case of very large amplitudes. In general, basic wave properties (wave amplitude, wave speed, vorticity, and wave energy) increase as the wave amplitude increases for a specific value of the pycnocline thickness. Moreover, the pycnocline thickness chiefly determines the core size of a convex mode-2 ISW, while the step depth (that generates an initial wave amplitude) and offset in pycnocline govern the waveform type during its propagation on the flat bottom.",
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    Effects of initial amplitude and pycnocline thickness on the evolution of mode-2 internal solitary waves. / Cheng, M.H.; Hsieh, C.M.; Hwang, R.R.; Hsu, J.R.C.

    In: Physics of Fluids, Vol. 30, No. 4, 042101, 01.04.2018.

    Research output: Contribution to journalArticle

    TY - JOUR

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    AU - Hsieh, C.M.

    AU - Hwang, R.R.

    AU - Hsu, J.R.C.

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