Measurement of Turbulent Fluxes and Dissipation Rates in the Coastal Bottom Boundary Layer

1997 ◽  
Author(s):  
J. H. Trowbridge ◽  
A. J. Williams
Keyword(s):  
Boundary Layer ◽  
Turbulent Fluxes ◽  
Bottom Boundary Layer ◽  
Bottom Boundary ◽  
Dissipation Rates

On the Structure of Turbulence in the Bottom Boundary Layer of the Coastal Ocean

2005 ◽  
Vol 35 (1) ◽  
pp. 72-93 ◽  
Author(s):  
W. A. M. Nimmo Smith ◽  
J. Katz ◽  
T. R. Osborn
Keyword(s):  
Boundary Layer ◽  
Energy Spectrum ◽  
Coastal Ocean ◽  
Bottom Boundary Layer ◽  
Small Scale ◽  
Shear Stresses ◽  
Weak Turbulence ◽  
Conditional Sampling ◽  
Bottom Boundary ◽  
Dissipation Rates

Abstract Six sets of particle image velocimetry (PIV) data from the bottom boundary layer of the coastal ocean are examined. The data represent periods when the mean currents are higher, of the same order, and much weaker than the wave-induced motions. The Reynolds numbers based on the Taylor microscale (Reλ) are 300–440 for the high, 68–83 for the moderate, and 14–37 for the weak mean currents. The moderate–weak turbulence levels are typical of the calm weather conditions at the LEO-15 site because of the low velocities and limited range of length scales. The energy spectra display substantial anisotropy at moderate to high wavenumbers and have large bumps at the transition from the inertial to the dissipation range. These bumps have been observed in previous laboratory and atmospheric studies and have been attributed to a bottleneck effect. Spatial bandpass-filtered vorticity distributions demonstrate that this anisotropy is associated with formation of small-scale, horizontal vortical layers. Methods for estimating the dissipation rates are compared, including direct estimates based on all of the gradients available from 2D data, estimates based on gradients of one velocity component, and those obtained from curve fitting to the energy spectrum. The estimates based on vertical gradients of horizontal velocity are higher and show better agreement with the direct results than do those based on horizontal gradients of vertical velocity. Because of the anisotropy and low turbulence levels, a −5/3 line-fit to the energy spectrum leads to mixed results and is especially inadequate at moderate to weak turbulence levels. The 2D velocity and vorticity distributions reveal that the flow in the boundary layer at moderate speeds consists of periods of “gusts” dominated by large vortical structures separated by periods of more quiescent flows. The frequency of these gusts increases with Reλ, and they disappear when the currents are weak. Conditional sampling of the data based on vorticity magnitude shows that the anisotropy at small scales persists regardless of vorticity and that most of the variability associated with the gusts occurs at the low-wave-number ends of the spectra. The dissipation rates, being associated with small-scale structures, do not vary substantially with vorticity magnitude. In stark contrast, almost all the contributions to the Reynolds shear stresses, estimated using structure functions, are made by the high- and intermediate-vorticity-magnitude events. During low vorticity periods the shear stresses are essentially zero. Thus, in times with weak mean flow but with wave orbital motion, the Reynolds stresses are very low. Conditional sampling based on phase in the wave orbital cycle does not show any significant trends.

An approach to determine coefficients of logarithmic velocity vertical profile in the bottom boundary layer

2021 ◽  
Author(s):  
Xiaowei Wei ◽  
Yiming Zhang ◽  
Changming Dong ◽  
Meibing Jin ◽  
Changshui Xia
Keyword(s):  
Boundary Layer ◽  
Vertical Profile ◽  
Bottom Boundary Layer ◽  
Bottom Boundary

Internal solitary wave bottom boundary layer dissipation

2021 ◽  
Vol 6 (7) ◽  
Author(s):  
S. Zahedi ◽  
P. Aghsaee ◽  
L. Boegman
Keyword(s):  
Boundary Layer ◽  
Solitary Wave ◽  
Internal Solitary Wave ◽  
Bottom Boundary Layer ◽  
Bottom Boundary

The turbulent bottom boundary layer and its influence on local dynamics over the continental shelf

1988 ◽  
Vol 12 (2) ◽  
pp. 143-172 ◽  
Author(s):  
Richard D. Dewey ◽  
Paul H. Leblond ◽  
William R. Crawford
Keyword(s):  
Boundary Layer ◽  
Continental Shelf ◽  
Bottom Boundary Layer ◽  
Local Dynamics ◽  
Bottom Boundary

Measurements in the bottom boundary layer on the Amazon subaqueous delta

1995 ◽  
Vol 125 (3-4) ◽  
pp. 235-257 ◽  
Author(s):  
D.A. Cacchione ◽  
D.E. Drake ◽  
R.W. Kayen ◽  
R.W. Sternberg ◽  
G.C. Kineke ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Bottom Boundary Layer ◽  
Bottom Boundary
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