scholarly journals EVOLUTION OF INTERFACIAL WAVES ALONG AN UNSTEADY SALT WEDGE

1984 ◽  
Vol 1 (19) ◽  
pp. 198
Author(s):  
Wataru Nakano ◽  
Isao Yakuwa
Keyword(s):  
Wave Breaking ◽  
Ultrasonic Method ◽  
Power Spectra ◽  
Field Measurements ◽  
Nonlinear Property ◽  
Interfacial Waves ◽  
Salt Wedge ◽  
Diffusion Pattern

Field measurements of the receding salt wedge were made at the mouth of the Ishikari River in October 1981. The gradually growing interfacial waves and the diffusion pattern of salinity are visualized by the Ultrasonic Method. The evolution mechanisms of waves are analysed in detail by calculating the power spectra of wave records. It is pointed out that the wave breaking, the wave-eddy interaction and the nonlinearity of waves are factors dominating the evolution. The nonlinear property of interfacial waves is studied further by watertank experiments.

Wave-Follower Field Measurements of the Wind-Input Spectral Function. Part III: Parameterization of the Wind-Input Enhancement due to Wave Breaking

2007 ◽  
Vol 37 (11) ◽  
pp. 2764-2775 ◽  
Author(s):  
Alexander V. Babanin ◽  
Michael L. Banner ◽  
Ian R. Young ◽  
Mark A. Donelan
Keyword(s):  
Energy Flux ◽  
Water Waves ◽  
Wave Breaking ◽  
Field Measurements ◽  
Mean Value ◽  
Breaking Wave ◽  
Strong Wind ◽  
Local Wave ◽  
Wind Input ◽  
The Waves

Abstract This is the third in a series of papers describing wave-follower observations of the aerodynamic coupling between wind and waves on a large shallow lake during the Australian Shallow Water Experiment (AUSWEX). It focuses on the long-standing problem of the aerodynamic consequences of wave breaking on the wind–wave coupling. Direct field measurements are reported of the influence of wave breaking on the wave-induced pressure in the airflow over water waves, and hence the energy flux to the waves. The level of forcing, measured by the ratio of wind speed to the speed of the dominant (spectral peak) waves, covered the range of 3–7. The propagation speeds of the dominant waves were limited by the water depth and the waves were correspondingly steep. These measurements allowed an assessment of the magnitude of any breaking-induced enhancement operative for these field conditions and provided a basis for parameterizing the effect. Overall, appreciable levels of wave breaking occurred for the strong wind forcing conditions that prevailed during the observational period. Associated with these breaking wave events, a significant phase shift is observed in the local wave-coherent surface pressure. This produced an enhanced wave-coherent energy flux from the wind to the waves with a mean value of 2 times the corresponding energy flux to the nonbreaking waves. It is proposed that the breaking-induced enhancement of the wind input to the waves can be parameterized by the sum of the nonbreaking input and the contribution due to the breaking probability.

scholarly journals The Effects of the Internal Flow Structure on SPM Entrapment in the Rotterdam Waterway

2010 ◽  
Vol 40 (11) ◽  
pp. 2357-2380 ◽  
Author(s):  
Michel A. J. de Nijs ◽  
Johan C. Winterwerp ◽  
Julie D. Pietrzak
Keyword(s):  
Abrupt Change ◽  
Tidal Flow ◽  
Three Dimensional ◽  
Internal Flow ◽  
Field Measurements ◽  
High Water ◽  
Transport Pathways ◽  
Salt Wedge ◽  
Suspended Particulate ◽  
Bed Stress

Abstract Field measurements are presented, which are the first to quantify the processes influencing the entrapment of suspended particulate matter (SPM) at the limit of saltwater intrusion in the Rotterdam Waterway. The estuarine turbidity maximum (ETM) is shown to be maintained by the trapping of fluvial SPM at the head of the salt wedge. The trapping process is associated with the raining out of fluvial SPM from the upper, fresher part of the water column, into the layer below the pycnocline. The dominant mechanisms responsible are baroclinic shear flows and the abrupt change in turbulent mixing characteristics due to damping of turbulence at the pycnocline. This view contrasts with the assumption of landward transport of marine SPM by asymmetries in bed stress. The SPM transport capacity of the tidal flow is not fully utilized in the ETM, and the ETM is independent of a bed-based supply of mud. This is explained by regular exchange of part of the ETM with harbor basins, which act as efficient sinks, and that the Rotterdam Waterway is not a complete fluvial SPM trap. The supply of SPM by the freshwater discharge ensures that the ETM is maintained over time. Hence, the ETM is an advective phenomenon. Relative motion between SPM and saltwater occurs because of lags introduced by resuspension. Moreover, SPM that lags behind the salt wedge after high water slack (HWS) is eventually recollected at the head. Hence, SPM follows complex transport pathways and the mechanisms involved in trapping and transport of SPM are inherently three-dimensional.

scholarly journals Mountain-Wave Turbulence in the Presence of Directional Wind Shear over the Rocky Mountains

2018 ◽  
Vol 75 (4) ◽  
pp. 1285-1305 ◽  
Author(s):  
Maria-Vittoria Guarino ◽  
Miguel A. C. Teixeira ◽  
Teddie L. Keller ◽  
Robert D. Sharman
Keyword(s):  
Rocky Mountains ◽  
Wave Breaking ◽  
Wind Shear ◽  
Shear Flows ◽  
Atmospheric Stability ◽  
Power Spectra ◽  
Wave Turbulence ◽  
Background Wind ◽  
Critical Levels ◽  
Mountain Wave

Abstract Mountain-wave turbulence in the presence of directional wind shear over the Rocky Mountains in Colorado is investigated. Pilot reports (PIREPs) are used to select cases in which moderate or severe turbulence encounters were reported in combination with significant directional wind shear in the upstream sounding from Grand Junction, Colorado (GJT). For a selected case, semi-idealized numerical simulations are carried out using the WRF-ARW atmospheric model, initialized with the GJT atmospheric sounding and a realistic but truncated orography profile. To isolate the role of directional wind shear in causing wave breaking, sensitivity tests are performed to exclude the variation of the atmospheric stability with height, the speed shear, and the mountain amplitude as dominant wave breaking mechanisms. Significant downwind transport of instabilities is detected in horizontal flow cross sections, resulting in mountain-wave-induced turbulence occurring at large horizontal distances from the first wave breaking point (and from the orography that generates the waves). The existence of an asymptotic wake, as predicted by Shutts for directional shear flows, is hypothesized to be responsible for this downwind transport. Critical levels induced by directional wind shear are further studied by taking 2D power spectra of the magnitude of the horizontal velocity perturbation field. In these spectra, a rotation of the most energetic wave modes with the background wind, as well as perpendicularity between the background wind vector and the wavenumber vector of those modes at critical levels, can be found, which is consistent with the mechanism expected to lead to wave breaking in directional shear flows.

scholarly journals Characterizing Wave Shape Evolution on an Ebb-Tidal Shoal

2019 ◽  
Vol 7 (10) ◽  
pp. 367 ◽  
Author(s):  
Floris de Wit ◽  
Marion Tissier ◽  
Ad Reniers
Keyword(s):  
Wave Breaking ◽  
Field Measurements ◽  
Tidal Currents ◽  
Wave Shape ◽  
Spatial Gradients ◽  
Nonlinear Energy Transfer ◽  
Waves And Currents ◽  
Wave Induced ◽  
Local Parameters ◽  
Nonlinear Energy

Field measurements of waves and currents were obtained at ten locations on an ebb-tidal shoal seaward of Ameland Inlet for a six-week period. These measurements were used to investigate the evolution of the near-bed velocity skewness and asymmetry, as these are important drivers for wave-induced sediment tranport. Wave shape parameters were compared to traditionally used parameterizations to quantify their performance in a dynamic area with waves and tidal currents coming in from different directions over a highly variable bathymetry. Spatially and temporally averaged, these parameterizations compared very well to observed wave shape. However, significant scatter was observed. The largest deviations from the parameterization were observed at the shallowest locations, where the contribution of wave-induced sediment transport was expected to be the largest. This paper shows that this scatter was caused by differences in wave-breaking, nonlinear energy transfer rate, and spatial gradients in tidal currents. Therefore, it is proposed to include the prior evolution of the wave before reaching a location in future parameterizations in numerical modeling instead of only using local parameters to predict wave shape.

Field measurements and scaling of ocean surface wave-breaking statistics

2013 ◽  
Vol 40 (12) ◽  
pp. 3074-3079 ◽  
Author(s):  
Peter Sutherland ◽  
W. Kendall Melville
Keyword(s):  
Surface Wave ◽  
Wave Breaking ◽  
Field Measurements ◽  
Ocean Surface ◽  
Ocean Surface Wave

scholarly journals Advection of the Salt Wedge and Evolution of the Internal Flow Structure in the Rotterdam Waterway

2011 ◽  
Vol 41 (1) ◽  
pp. 3-27 ◽  
Author(s):  
Michel A. J. de Nijs ◽  
Julie D. Pietrzak ◽  
Johan C. Winterwerp
Keyword(s):  
Turbulent Mixing ◽  
Internal Flow ◽  
Field Measurements ◽  
Tidal Asymmetry ◽  
Exchange Flow ◽  
Salt Wedge ◽  
Slack Water ◽  
Measuring Period ◽  
Wedge Structure ◽  
Internal Tidal Asymmetry

Abstract An analysis of field measurements recorded over a tidal cycle in the Rotterdam Waterway is presented. These measurements are the first to elucidate the processes influencing the along-channel current structure and the excursion of the salt wedge in this estuary. The salt wedge structure remained stable throughout the measuring period. The velocity measurements indicate decoupling effects between the layers and that bed-generated turbulence is confined below the pycnocline. The barotropic M4 overtide structure is imposed at the mouth of the estuary, and the generation of M4 overtides within the estuary is found to be relatively small. Internal tidal asymmetry does not make a significant contribution to the M4 velocity frequency band. Instead, the combination of barotropic and baroclinic forcing, in conjunction with the suppression of turbulence at the interface, provides the main explanation for the time dependence and mean structure of the flow in the Rotterdam Waterway. This gives rise to the observed differences in the length of the flood and ebb, in the magnitudes of the flood and ebb velocities, in the length of the slack water periods, and in the timing of the onset of slack water at the surface and near the bed. It results in the formation of distinct exchange flow profiles at the head of the salt wedge around slack water and the creation of maximal velocities at the pycnocline during flood. Advection governs the displacement and structure of the salt wedge since turbulent mixing is suppressed. The tidal displacement of the salt wedge controls the height of the pycnocline above the bed at a particular site. Hence, it controls the height to which bed-generated turbulence can protrude into the water column. Consequently, the authors find asymmetries in the structure of the internal flow, turbulent mixing, and bed stresses that are not related to classical internal tidal asymmetry.

scholarly journals Using wavelet spectrum analysis to resolve breaking events in the wind wave time series

2004 ◽  
Vol 22 (10) ◽  
pp. 3335-3345 ◽  
Author(s):  
P. C. Liu ◽  
A. V. Babanin
Keyword(s):  
Time Series ◽  
Spectrum Analysis ◽  
Wave Breaking ◽  
Field Measurements ◽  
Finite Depth ◽  
Breaking Waves ◽  
Wavelet Spectrum ◽  
New Approach ◽  
Equivalent Wave

Abstract. This paper presents the development of a new approach, based on wavelet spectrum analysis, for the detection of breaking waves in a time series of surface wave fluctuations. The approach is shown to be capable of producing equivalent wave breaking statistics as field measurements based on detection of whitecaps at a fixed point of observation. This wavelet-based approach is applicable to both deep water and finite depth environments. Based on applications of this approach to the analysis of available field data, a novel classification of wave breaking processes that consists of incipient, developing, and subsiding phases is proposed.

scholarly journals STUDIES ON SALT WEDGE BY ULTRASONIC METHOD

1966 ◽  
Vol 1 (10) ◽  
pp. 79
Author(s):  
Hisao Fukushima ◽  
Masakazu Kashiwamura ◽  
Isao Yakuwa
Keyword(s):  
Ultrasonic Method ◽  
Salt Wedge ◽  
Layer Flow

This paper presents some observational results on salt wedges obtained by the ultrasonic method at the mouth of the Ishikari River, with a description of some studies on the two-layer flow developed by the authors.

Surface and interfacial waves in a strongly stratified upper ocean

2020 ◽  
Author(s):  
Johannes Gemmrich ◽  
Adam Monahan
Keyword(s):  
Surface Wave ◽  
Wave Field ◽  
Wave Breaking ◽  
Density Ratio ◽  
Initial Surface ◽  
Spectral Change ◽  
Interfacial Waves ◽  
Interfacial Wave ◽  
Time Step ◽  
Surface Wave Field

AbstractIn an idealized two-layer fluid, surface waves can generate waves at the internal interface through class 3 resonant triads in which all waves are propagating in the same direction. The triads are restricted to wavenumbers above a critical value kcrit that depends on the density ratio R between the two layers, and their depths. We perform numerical simulations to analyze the evolution of a surface wave field, initially specified by a Pierson-Moskowitz type spectrum, for R = 0:97 (representing a realistic lower a bound for oceanic stratification). At high initial steepness and peak wavenumber kp ≪ kcrit, the energy increases in the spectral tail; as a parameterization of resulting wave breaking, at each time step individual waves with a steepness greater than the limiting Stokes steepness are removed. The energy change of the surface wave field is a combination of energy transfer to the interfacial waves, spectral downshift, and wave breaking dissipation. At wavenumbers ≳ 0:6kp there is a net loss of energy, with the greatest dissipation at ≈ 1:3kp. The maximum gain occurs at ≈ 0:5kp. The onset of the spectral change shows a strong threshold behaviour with respect to the the initial wave steepness. For steep initial waves the integrated energy dissipation can reach > 30% of the initial energy, and only ≈ 1% of the initial surface wave energy is transferred to the interfacial wave field. The spectral change could be expressed as an additional dissipation source term, and coupled ocean/wave models should include additional mixing associated with the interfacial waves and enhanced wave breaking turbulence.

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