The Relationship between Flux Coefficient and Entrainment Ratio in Density Currents

Wells, Mathew G.; Cenedese, Claudia; Caulfield, C. P.

doi:10.1175/2010jpo4225.1

Cited by 69 publications

(71 citation statements)

References 63 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, a dependence of the entrainment on the Reynolds number was found by Cenedese and Adduce (2008). Wells and Wettlaufer (2005) reproduced the nonrotating results of Ellison and Turner (1959), and Wells (2007) found results similar to Ellison and Turner (1959) in rotating experiments. Nonrotating experiments investigating entrainment and detrainment in a dense current flowing downslope in a stratified fluid were conducted by Baines (2001Baines ( , 2002Baines ( , 2005Baines ( , 2008 for different slope angles.…”

Section: Introductionsupporting

confidence: 76%

“…The oceanic data span five location sites: Mediterranean overflow (Baringer and Price 1997), Denmark Strait , Faroe Bank Channel (Mauritzen et al 2005), Baltic Sea (Arneborg et al 2007), and Lake Ogawara (Dallimore et al 2001); while the laboratory data include both nonrotating (Ellison and Turner 1959;Alavian 1986) and rotating (Cenedese et al 2004;Cenedese and Adduce 2008;Wells 2007) experiments on density driven currents descending a slope. For the majority of the data used, the values of the entrainment parameter, E, Fr, and Re are not ''local'' and ''instantaneous'' measurements, but instead are based on ''integral'' measurements.…”

Section: A New Parameterizationmentioning

confidence: 99%

See 1 more Smart Citation

A New Parameterization for Entrainment in Overflows

Cenedese

Adduce²

2010

Journal of Physical Oceanography

Self Cite

View full text Add to dashboard Cite

Dense overflows entrain surrounding waters at specific locations, for example, sills and constrictions, but also along the descent over the continental slope. The amount of entrainment dictates the final properties of these overflows, and thus is of fundamental importance to the understanding of the formation of deep water masses. Even when resolving the overflows, coarse resolution global circulation and climate models cannot resolve the entrainment processes that are often parameterized. A new empirical parameterization is suggested, obtained using an oceanic and laboratory dataset, which includes two novel aspects. First, the parameterization depends on both the Froude number (Fr) and Reynolds number of the flow. Second, it takes into account subcritical (Fr , 1) entrainment. A weak, but nonzero, entrainment can change the final density and, consequently, the depth and location of important water masses in the open ocean. This is especially true when the dense current follows a long path over the slope in a subcritical regime, as observed in the southern Greenland Deep Western Boundary Current. A streamtube model employing this new parameterization gives results that are more consistent with previous laboratory and oceanographic observations than when a classical parameterization is used. Finally, the new parameterization predictions compare favorably to recent oceanographic measurements of entrainment and turbulent diapycnal mixing rates, using scaling arguments to relate the entrainment ratio to diapycnal diffusivities.

show abstract

Section: Introductionsupporting

confidence: 76%

Section: A New Parameterizationmentioning

confidence: 99%

A New Parameterization for Entrainment in Overflows

Cenedese

Adduce²

2010

Journal of Physical Oceanography

Self Cite

View full text Add to dashboard Cite

show abstract

“…(7) Figure 7 is a reproduction of Fig. 2 by Wells et al (2010) representing an empirical dependence of the entrainment ratio E versus Froude number Fr collected from different field and laboratory experiments. We have added two pairs of extra points in this figure that came from this study (the red and magenta pentagons).…”

Section: Microstructure Estimates Of Entrainmentmentioning

confidence: 99%

Microstructure measurements and estimates of entrainment in the Denmark Strait overflow plume

Пака

Zhurbas²,

Rudels³

et al. 2013

Ocean Sci.

View full text Add to dashboard Cite

Abstract. To examine processes controlling the entrainment of ambient water into the Denmark Strait overflow (DSO) plume / gravity current, measurements of turbulent dissipation rate were carried out by a quasi-free-falling (tethered) microstructure profiler (MSP). The MSP was specifically designed to collect data on dissipation-scale turbulence and fine thermohaline stratification in an ocean layer located as deep as 3500 m. The task was to perform microstructure measurements in the DSO plume in the lower 300 m depth interval including the bottom mixed layer and the interfacial layer below the non-turbulent ambient water. The MSP was attached to a Rosette water sampler rack equipped with a SeaBird CTDO and an RD Instruments lowered acoustic Doppler current profiler (LADCP). At a chosen depth, the MSP was remotely released from the rack to perform measurements in a quasi-free-falling mode.Using the measured vertical profiles of dissipation, the entrainment rate as well as the bottom and interfacial stresses in the DSO plume were estimated at a location 200 km downstream of the sill at depths up to 1771 m. Dissipation-derived estimates of entrainment were found to be much smaller than bulk estimates of entrainment calculated from the downstream change of the mean properties in the plume, suggesting the lateral stirring due to mesoscale eddies rather than diapycnal mixing as the main contributor to entrainment. Dissipation-derived bottom stress estimates are argued to be roughly one third the magnitude of those derived from log velocity profiles. In the interfacial layer, the Ozmidov scale calculated from turbulence dissipation rate and buoyancy frequency was found to be linearly proportional to the overturning scale extracted from conventional CTD data (the Thorpe scale), with a proportionality constant of 0.76, and a correlation coefficient of 0.77.

show abstract

“…Many authors have since tried to validate and extend the determination of E either empirically or based on theoretical modelling (e.g. [2][3][4][5][6][7][8]; see also [9] and references therein). However, there is still significant uncertainty in the accurate quantification and correct parametrization of E [5].…”

Section: Introductionmentioning

confidence: 99%

Small-scale entrainment in inclined gravity currents

2017

View full text Add to dashboard Cite

We investigate the effect of buoyancy on the small-scale aspects of turbulent entrainment by performing direct numerical simulation of a gravity current and a wall jet. In both flows, we detect the turbulent/nonturbulent interface separating turbulent from irrotational ambient flow regions using a range of enstrophy iso-levels spanning many orders of magnitude. Conform to expectation, the relative enstrophy isosurface velocity v n in the viscous superlayer scales with the Kolmogorov velocity for both flow cases. We connect the integral entrainment coefficient E to the small-scale entrainment and observe excellent agreement between the two estimates throughout the viscous superlayer. The contribution of baroclinic torque to v n is negligible, and we show that the primary reason for reduced entrainment in the gravity current as compared to the wall-jet are 1) the reduction of v n relative to the integral velocity scale u T ; and 2) the reduction in the surface area of the isosurfaces.

show abstract

The Relationship between Flux Coefficient and Entrainment Ratio in Density Currents

Cited by 69 publications

References 63 publications

A New Parameterization for Entrainment in Overflows

A New Parameterization for Entrainment in Overflows

Microstructure measurements and estimates of entrainment in the Denmark Strait overflow plume

Small-scale entrainment in inclined gravity currents

Contact Info

Product

Resources

About