On wave diffraction of two-dimensional moonpools in a two-layer fluid with finite depth

Xin Xu, Xingyu Song, Xinshu Zhang, Zhiming Yuan

Research output: Contribution to journalArticle

Abstract

This paper studies the wave diffraction problem of two-dimensional moonpools in a two-layer fluid by using domain decomposition scheme and the method of eigenfunction expansion. Wave exciting forces, free surface and internal wave elevations are computed and analyzed for both surface wave and internal wave modes. The present model is validated by comparing a limiting case with a single-layer fluid case. Both piston mode and sloshing mode resonances have been identified and analyzed. It is observed that, compared with the solutions in surface wave mode, the wave exciting forces in internal wave mode are much smaller, and show more peaks and valleys in low-frequency region. As the wave frequency increases, the bandwidth of sloshing mode resonances decreases. Extensive parametric studies have been performed to examine the effects of moonpool geometry and density stratification on the resonant wave motion and exciting forces. It is found that, for twin bodies with deep draft in surface wave mode, the decreasing density ratio has little effects on the sloshing mode resonance frequencies but can somehow suppress the horizontal wave exciting forces and surface wave elevations around piston mode resonance region. In addition, the presence of lower-layer fluid can lead to the reduction of piston mode resonance frequency.
LanguageEnglish
Pages571-586
Number of pages16
JournalOcean Engineering
Volume173
Early online date23 Jan 2019
DOIs
Publication statusPublished - 1 Feb 2019

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Diffraction
Fluids
Liquid sloshing
Surface waves
Pistons
Eigenvalues and eigenfunctions
Decomposition
Bandwidth
Geometry

Keywords

  • moonpool
  • two-layer fluid
  • wave diffraction
  • resonance
  • piston mode
  • sloshing mode

Cite this

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title = "On wave diffraction of two-dimensional moonpools in a two-layer fluid with finite depth",
abstract = "This paper studies the wave diffraction problem of two-dimensional moonpools in a two-layer fluid by using domain decomposition scheme and the method of eigenfunction expansion. Wave exciting forces, free surface and internal wave elevations are computed and analyzed for both surface wave and internal wave modes. The present model is validated by comparing a limiting case with a single-layer fluid case. Both piston mode and sloshing mode resonances have been identified and analyzed. It is observed that, compared with the solutions in surface wave mode, the wave exciting forces in internal wave mode are much smaller, and show more peaks and valleys in low-frequency region. As the wave frequency increases, the bandwidth of sloshing mode resonances decreases. Extensive parametric studies have been performed to examine the effects of moonpool geometry and density stratification on the resonant wave motion and exciting forces. It is found that, for twin bodies with deep draft in surface wave mode, the decreasing density ratio has little effects on the sloshing mode resonance frequencies but can somehow suppress the horizontal wave exciting forces and surface wave elevations around piston mode resonance region. In addition, the presence of lower-layer fluid can lead to the reduction of piston mode resonance frequency.",
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On wave diffraction of two-dimensional moonpools in a two-layer fluid with finite depth. / Xu, Xin; Song, Xingyu; Zhang, Xinshu; Yuan, Zhiming.

In: Ocean Engineering, Vol. 173, 01.02.2019, p. 571-586.

Research output: Contribution to journalArticle

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