On the wave and current interaction with a rippled seabed in the coastal ocean bottom boundary layer

2015 ◽  
Vol 120 (7) ◽  
pp. 4595-4624 ◽  
Author(s):  
Aditya R. Nayak ◽  
Cheng Li ◽  
Bobak T. Kiani ◽  
Joseph Katz
Keyword(s):  
Boundary Layer ◽  
Coastal Ocean ◽  
Bottom Boundary Layer ◽  
Ocean Bottom ◽  
Bottom Boundary ◽  
Current Interaction

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.

PIV measurements in the bottom boundary layer of the coastal ocean

2002 ◽  
Vol 33 (6) ◽  
pp. 962-971 ◽  
Author(s):  
W. Nimmo Smith ◽  
P. Atsavapranee ◽  
J. Katz ◽  
T. Osborn
Keyword(s):  
Boundary Layer ◽  
Coastal Ocean ◽  
Bottom Boundary Layer ◽  
Piv Measurements ◽  
Bottom Boundary

scholarly journals Direct measurement of hairpin‐like vortices in the bottom boundary layer of the coastal ocean

2016 ◽  
Vol 43 (3) ◽  
pp. 1175-1183 ◽  
Author(s):  
Edward C. C. Steele ◽  
W. Alex M. Nimmo‐Smith ◽  
Andrey Vlasenko
Keyword(s):  
Boundary Layer ◽  
Direct Measurement ◽  
Coastal Ocean ◽  
Bottom Boundary Layer ◽  
Bottom Boundary

Wave-current interaction within and outside the bottom boundary layer

1993 ◽  
Vol 21 (1-3) ◽  
pp. 41-69 ◽  
Author(s):  
R.L. Soulsby ◽  
L. Hamm ◽  
G. Klopman ◽  
D. Myrhaug ◽  
R.R. Simons ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Bottom Boundary Layer ◽  
Bottom Boundary ◽  
Current Interaction

Global Observations of Ocean-Bottom Subinertial Current Dissipation

2013 ◽  
Vol 43 (2) ◽  
pp. 402-417 ◽  
Author(s):  
Corwin J. Wright ◽  
Robert B. Scott ◽  
Darran Furnival ◽  
Pierre Ailliot ◽  
Franck Vermet
Keyword(s):  
Boundary Layer ◽  
World Ocean ◽  
Deep Ocean ◽  
Ocean Model ◽  
Bottom Boundary Layer ◽  
Ocean Current ◽  
Ocean Bottom ◽  
Bottom Boundary ◽  
Energy Dissipated ◽  
Current Dissipation

Abstract Quadratic bottom boundary layer drag is a potentially significant source of energy dissipation in the deep ocean. This study presents a new estimate of the energy dissipated by this process, using results from the world’s largest archive of ocean current meter time series and focusing strongly upon the potential uncertainties in this calculation. Two methods are used, one based on a simple division of the World Ocean into a series of regular grids and the other based on a more sophisticated analysis using a hierarchical clustering mechanism assisted by estimates from the Hybrid Coordinate Ocean Model (HYCOM) model. From these analyses, the authors estimate a globally integrated bottom boundary layer dissipation of 0.65 ± 0.15 (statistical uncertainty) ± 0.15 (methodological uncertainty) TW.

scholarly journals A NUMERICAL STUDY OF WAVE-CURRENT INTERACTION IN THE BOTTOM BOUNDARY LAYER

2017 ◽  
pp. 17
Author(s):  
Xuan Zhang ◽  
Richard Simons ◽  
Eugeny Buldakov
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Numerical Study ◽  
Bottom Boundary Layer ◽  
Bed Shear Stress ◽  
Bottom Boundary ◽  
Time Histories ◽  
Current Interaction ◽  
Numerical Beach ◽  
Good Agreement

In the present work, a numerical wave-current flume has been developed, based on a standard k-ε model. The numerical flume was 12.86m in length, with a numerical beach at one end of the flume. The Volume of Fluid (VOF) method was used to capture the free surface in the flume. The velocity profile obtained at the test section from the numerical simulation has then been compared with experimental data and good agreement found. Periodic velocities in the bottom boundary layer have been obtained which agree well with the experimental data. The model provides an insight to the changes in bed shear stress time histories that characterise wave current interaction.

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