Experiments on Differential Scalar Mixing in Turbulence in a Sheared, Stratified Flow

Jackson, P. Ryan; Rehmann, Chris R.

doi:10.1175/jpo-d-14-0027.1

Cited by 24 publications

(25 citation statements)

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“…Experiments with synthetic surrogate eggs in flowing water were performed in an Odell-Kovasznay style flume [ 25 ], a temperature-controlled recirculatory flume built originally for stratified flow experiments at the University of Illinois [ 26 ]. The flow in the flume is controlled by a disk pump, which runs at different rotation rates resulting in different ranges of flow velocities.…”

Section: Methodsmentioning

confidence: 99%

A Laboratory Investigation of the Suspension, Transport, and Settling of Silver Carp Eggs Using Synthetic Surrogates

et al. 2015

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Asian carp eggs are semi-buoyant and must remain suspended in the water to survive, supported by the turbulence of the flow, until they hatch and develop the ability to swim. Analysis of the transport and dispersal patterns of Asian carp eggs will facilitate the development and implementation of control strategies to target the early life stages. Experimenting with Asian carp eggs is complicated due to practical issues of obtaining eggs in close proximity to experimental facilities and extensive handling of eggs tends to damage them. Herein, we describe laboratory experiments using styrene beads (4.85 mm diameter) as synthetic surrogate eggs to mimic the physical properties of water-hardened silver carp eggs. The first set of experiments was completed in a rectangular vertical column filled with salt water. The salinity of the water was adjusted in an iterative fashion to obtain a close approximation of the fall velocity of the styrene beads to the mean fall velocity of silver carp water-hardened eggs. The terminal fall velocity of synthetic eggs was measured using an image processing method. The second set of experiments was performed in a temperature-controlled recirculatory flume with a sediment bed. The flume was filled with salt water, and synthetic eggs were allowed to drift under different flow conditions. Drifting behavior, suspension conditions, and settling characteristics of synthetic eggs were observed. At high velocities, eggs were suspended and distributed through the water column. Eggs that touched the sediment bed were re-entrained by the flow. Eggs saltated when they touched the bed, especially at moderate velocities and with a relatively flat bed. At lower velocities, some settling of the eggs was observed. With lower velocities and a flat bed, eggs were trapped near the walls of the flume. When bedforms were present, eggs were trapped in the lee of the bedforms in addition to being trapped near the flume walls. Results of this research study provide insights about transport, suspension, and dispersion of silver carp eggs. The knowledge gained from this study is useful to characterize the critical hydrodynamic conditions of the flow at which surrogates for silver carp water-hardened eggs settle out of suspension, and provides insight into how eggs may interact with riverbed sediments and morphology.

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Section: Methodsmentioning

confidence: 99%

A Laboratory Investigation of the Suspension, Transport, and Settling of Silver Carp Eggs Using Synthetic Surrogates

et al. 2015

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“…Indicated regimes at the top only refer to the heat diffusivity. The thick grey line shows the Figure 1: Turbulent diffusivity model based on Bouffard and Boegman (2013) and Jackson and Rehmann (2014). Shown is the diapycnal diffusivity [m 2 s -1 ] of (red) heat and (blue) salt as a function of the turbulence intensity parameter.…”

Section: List Of Figuresmentioning

confidence: 99%

“…Shown is the diapycnal diffusivity [m 2 s -1 ] of (red) heat and (blue) salt as a function of the turbulence intensity parameter. The dashed blue curve corresponds to the salt diffusivity parameterized by Bouffard and Boegman (2013), whereas the solid blue curve is deduced from the heat diffusivity (red) using the diffusivity ratio parameterization of Jackson and Rehmann (2014). Indicated regimes at the top only refer to the heat diffusivity.…”

Section: List Of Figuresmentioning

confidence: 99%

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The Impact of a Variable Mixing Efficiency on the Abyssal Overturning

Lavergne

Madec

Sommer

et al. 2016

Journal of Physical Oceanography

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Manuscript (non-LaTeX) Click here to download Manuscript (non-LaTeX): Full manuscript_mod2.docx ABSTRACT 24In studies of ocean mixing, it is generally assumed that small-scale turbulent overturns lose 15-26 20 % of their energy in eroding the background stratification. Accumulating evidence that this energy fraction, or mixing efficiency R f , significantly varies depending on flow properties 28 challenges this assumption, however. Here, we examine the implications of a varying mixing and including the effect in ocean models. 44 3

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“…It is important to appreciate that Gn is an appropriate nondimensional parameter for any turbulent flow in a stratified fluid, yet is not necessarily equivalent to Re b unless A = 1 and L h , defined rationally for the flow under consideration, is equal to L t . The parameter range Gn ∈ [1, 100] is observed to occur widely in the world's oceans (Gargett et al 1984;Jackson & Rehmann 2014;Salehipour et al 2016), and so it is of geophysical interest to investigate this intermediate range further. This intermediate range is also of particular interest as different dynamical regimes have been identified with different ranges of Gn.…”

Section: Introductionmentioning

confidence: 99%

Robust identification of dynamically distinct regions in stratified turbulence

et al. 2016

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We present a new robust method for identifying three dynamically distinct regions in a stratified turbulent flow, which we characterise as quiescent flow, intermittent layers, and turbulent patches. The method uses the cumulative filtered distribution function of the local density gradient to identify each region. We apply it to data from direct numerical simulations of homogeneous stratified turbulence, with unity Prandtl number, resolved on up to 8192×8192×4096 grid points. In addition to classifying regions consistently with contour plots of potential enstrophy, our method identifies quiescent regions as regions where /νN 2 ∼ O(1), layers as regions where /νN 2 ∼ O(10), and patches as regions where /νN 2 ∼ O(100). Here is the dissipation rate of turbulence kinetic energy, ν is the kinematic viscosity, and N is the (overall) buoyancy frequency. By far the highest local dissipation and mixing rates, and the majority of dissipation and mixing, occur in patch regions, even when patch regions occupy only 5% of the flow volume. We conjecture that treating stratified turbulence as an instantaneous assemblage of these different regions in varying proportions may explain some of the apparently highly scattered flow dynamics and statistics previously reported in the literature.

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Experiments on Differential Scalar Mixing in Turbulence in a Sheared, Stratified Flow

Cited by 24 publications

References 96 publications

A Laboratory Investigation of the Suspension, Transport, and Settling of Silver Carp Eggs Using Synthetic Surrogates

A Laboratory Investigation of the Suspension, Transport, and Settling of Silver Carp Eggs Using Synthetic Surrogates

The Impact of a Variable Mixing Efficiency on the Abyssal Overturning

Robust identification of dynamically distinct regions in stratified turbulence

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