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  • Instabilities of a Baroclinic, Double Diffusive Frontal Zone

    Creator:
    Smyth, W. D.
    Abstract:
    The linear theory of double diffusive interleaving is extended to take account of baroclinic effects. This study goes beyond previous studies by including the possibility of modes with nonzero tilt in the alongfront direction, which allows for advection by the baroclinic frontal flow. This requires that the stability equations be...
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    tempera- Corresponding author address: W. D. Smyth, College of Oce- anic and Atmospheric Sciences, Oregon

  • Instability and Diapycnal Momentum Transport in a Double-Diffusive, Stratified Shear Layer

    Creator:
    Smyth, William D. and Kimura, Satoshi
    Abstract:
    The linear stability of a double-diffusively stratified, inflectional shear flow is investigated. Double-diffusive stratification has little effect on shear instability except when the density ratio R[subscript]ρ is close to unity. Double-diffusive instabilities have significant growth rates and can represent the fastest-growing mode even in the presence of inflectionally unstable shear...
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    -Diffusive, Stratified Shear Layer WILLIAM D. SMYTH AND SATOSHI KIMURA College of Oceanic and Atmospheric

  • Efficiency of Mixing Forced by Unsteady Shear Flow

    Creator:
    Inoue, Ryuichiro and Smyth, William D.
    Abstract:
    The dependence of mixing efficiency on time-varying forcing is studied by direct numerical simulation (DNS) of Kelvin–Helmholtz (KH) instability. Time-dependent forcing fields are designed to reproduce a wavelike oscillation by solving the equations of motion in a tilted coordinate frame and allowing the tilt angle to vary in time. Mixing...
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    Columbia, Canada WILLIAM D. SMYTH College of Oceanic and Atmospheric Science, Oregon State University

  • Effects of Ambient Turbulence on Interleaving at a Baroclinic Front

    Creator:
    Smyth, William D. and Ruddick, Barry
    Abstract:
    In this paper the authors investigate the action of ambient turbulence on thermohaline interleaving using both theory and numerical calculations in combination with observations from Meddy Sharon and the Faroe Front. The highly simplified models of ambient turbulence used previously are improved upon by allowing turbulent diffusivities of momentum, heat,...
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    at a Baroclinic Front WILLIAM D. SMYTH College of Oceanic and Atmospheric Sciences, Oregon State

  • Turbulence and Mixing in Holmboe Waves

    Creator:
    Smyth, W. D. and Winters, K. B.
    Abstract:
    Motivated by the tendency of high-Prandtl-number fluids to form sharp density interfaces, the authors investigate the evolution of Holmboe waves in a stratified shear flow through direct numerical simulation. Like their better-known cousins, Kelvin–Helmholtz waves, Holmboe waves lead the flow to a turbulent state in which rapid irreversible mixing takes...
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    Waves W. D. SMYTH College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis

  • Marginal instability and deep cycle turbulence in the eastern equatorial Pacific Ocean

    Creator:
    Smyth, W. D. and Moum, J. N.
    Abstract:
    Deep cycle mixing in the cold tongue of the equatorial Pacific Ocean is associated with a mean flow regime in which the gradient Richardson number Ri (a ratio of stratification to shear that affects the evolution of turbulence) fluctuates about a critical value near 1/4. This is the state of...
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  • Narrowband Oscillations in the Upper Equatorial Ocean. Part I: Interpretation as Shear Instabilities

    Creator:
    Moum, J. N., Nash, J. D., and Smyth, W. D.
    Abstract:
    Extended measurements of temperature fluctuations that include the turbulence wavenumber band have now been made using rapidly sampled fast thermistors at multiple depths above the core of the Equatorial Undercurrent on the Tropical Atmosphere Ocean (TAO) mooring at 0°, 140°W. These measurements include the signature of narrowband oscillations as well...
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    Ocean. Part I: Interpretation as Shear Instabilities J. N. MOUM, J. D. NASH, AND W. D. SMYTH College

  • Ocean Mixing by Kelvin-Helmholtz Instability

    Creator:
    Smyth, William D. and Moum, James N.
    Abstract:
    Kelvin-Helmholtz (KH) instability, characterized by the distinctive finite-amplitude billows it generates, is an important mechanism in the development of turbulence in the stratified interior of the ocean. In particular, it is often assumed that the onset of turbulence in internal waves begins in this way. Clear recognition of the importance...
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    | Vol. 25, No. 2140 Ocean Mixing by Kelvin-Helmholtz Instability B y W I l l I a M D . S M y t H

  • The Efficiency of Mixing in Turbulent Patches: Inferences from Direct Simulations and Microstructure Observations

    Creator:
    Smyth, W. D., Moum, J. N., and Caldwell, D. R.
    Abstract:
    The time evolution of mixing in turbulent overturns is investigated using a combination of direct numerical simulations (DNS) and microstructure profiles obtained during two field experiments. The focus is on the flux coefficient Γ, the ratio of the turbulent buoyancy flux to the turbulent kinetic energy dissipation rate ϵ. In...
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    Simulations and Microstructure Observations W. D. SMYTH, J. N. MOUM, AND D. R. CALDWELL College of Oceanic

  • Narrowband Oscillations in the Upper Equatorial Ocean. Part II: Properties of Shear Instabilities

    Creator:
    Smyth, W. D., Moum, J. N., and Nash, J. D.
    Abstract:
    Narrowband oscillations observed in the upper equatorial Pacific are interpreted in terms of a random ensemble of shear instability events. Linear perturbation analysis is applied to hourly averaged profiles of velocity and density over a 54-day interval, yielding a total of 337 unstable modes. Composite profiles of mean states and...
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    Ocean. Part II: Properties of Shear Instabilities W. D. SMYTH, J. N. MOUM, AND J. D. NASH College of