Turbulence-particle interactions under surface gravity waves

Mostafa Bakhoday Paskyabi

doi:10.1007/s10236-016-0989-0

Mostafa Bakhoday Paskyabi

Open Access

https://doi.org/10.1007/s10236-016-0989-0

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Abstract

Abstract The dispersion and transport of single inertial particles through an oscillatory turbulent aquatic environment are examined numerically by a Lagrangian particle tracking model using a series of idealised test cases. The turbulent mixing is incorporated into the Lagrangian model by the means of a stochastic scheme in which the inhomogeneous turbulent quantities are governed by a one-dimensional k- ε turbulence closure scheme. This vertical mixing model is further modified to include the effects of surface gravity waves including Coriolis-Stokes forcing, wave breaking, and Langmuir circulations. To simplify the complex interactions between the deterministic and the stochastic phases of flow, we assume a time-invariant turbulent flow field and exclude the hydrodynamic biases due to the effects of ambient mean current. The numerical results show that the inertial particles acquire perturbed oscillations traced out as time-varying sinking/rising orbits in the vicinity of the sea surface under linear and cnoidal waves and acquire a non-looping single arc superimposed with the high-frequency fluctuations beneath the nonlinear solitary waves. Furthermore, we briefly summarise some recipes through the course of this paper on the implementation of the stochastic particle tracking models to realistically describe the drift and suspension of inertial particles throughout the water column.

Highlights

The suspension and drift of buoyant particles, such as oil spills and biological matters, within an oscillatory turbulent fluid are frequently observed phenomena in a number of geophysical and offshore engineering applications (Murray 1970; Fowler and Knauer 1986; Wilson 2000; Ross 2010; Drivdal et al 2014)
We assume that waves and wind field propagate in the same direction, and the Coriolis parameter is set for the latitude of 63◦
We study the motions of inertial particles for homogeneous and non-homogeneous turbulent flows under various wind and wave forcing conditions

Summary

Introduction

The suspension and drift of buoyant particles, such as oil spills and biological matters, within an oscillatory turbulent fluid are frequently observed phenomena in a number of geophysical and offshore engineering applications (Murray 1970; Fowler and Knauer 1986; Wilson 2000; Ross 2010; Drivdal et al 2014). I.e., bubbles, exhibit strong tendency to trap in the high vorticity regions near the air-sea interface, heavy inertial particles (with diameter > 200 μm) sink to the deep ocean due to their tendency to accumulate in the regions of high strain rate and low vorticity. They have the ability to absorb and carry carbon into the water column (Noh et al 2006; Fowler and Knauer 1986). The detailed knowledge of mechanisms controlling the transformation of water parcels subjected to wave and turbulent forces is essential to better understand the exchange physical, chemical, and biological processes (such as the global carbon cycle and pollutant distribution) across the air-sea boundary and throughout the water column.

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