scholarly journals Reply to “Comment on ‘Using an ADCP to Estimate Turbulent Kinetic Energy Dissipation Rate in Sheltered Coastal Waters’”

2017 ◽  
Vol 34 (6) ◽  
pp. 1391-1392
Author(s):  
A. D. Greene ◽  
P. J. Hendricks ◽  
M. C. Gregg

AbstractThis note is a comment in response to Gargett, who argues that a large-eddy estimate of turbulent dissipation rate using a horizontal length scale with a vertical velocity estimate, as in Greene et al., is a dubious approximation if the energy-containing eddies are anisotropic. A simulation of Langmuir cells and associated turbulence is used to support Gargett’s conclusions. This rebuttal reviews the approaches taken by Greene et al. and cites several instances of flawed reasoning by Gargett. This includes using Langmuir simulations to support the primary conclusion of Gargett, which seems unconnected to Greene et al.’s data and ignores a vast body of work on simulating Kelvin–Helmholtz instabilities, widely considered to be the dominant mechanism producing stratified turbulence.

2015 ◽  
Vol 56 (5) ◽  
Author(s):  
Guus Bertens ◽  
Dennis van der Voort ◽  
Humberto Bocanegra-Evans ◽  
Willem van de Water

2017 ◽  
Vol 34 (6) ◽  
pp. 1387-1390 ◽  
Author(s):  
Ann E. Gargett

AbstractGreene et al. revisit the suggestion that the turbulent kinetic energy dissipation rate could be estimated through a “large-eddy estimate,” employing acoustic measurements of velocity fields associated with the largest energy-containing scales of ocean turbulence. While the large-eddy estimate as originally proposed used vertical velocity and a vertical eddy length scale, Greene et al. chose instead to substitute a horizontal length scale for the latter. This comment argues that combining a horizontal scale for length with a vertical velocity scale produces a large-eddy estimate of the dissipation rate that is accurate only if the energy-containing eddies are isotropic, and that this condition is highly unlikely in naturally occurring ocean turbulence, subject as it is to influences of stratification, vertical shear, and/or the presence of horizontal boundaries. The problem is documented using data from a large-eddy simulation of Langmuir supercells.


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