scholarly journals Generation of mode-2 internal waves in a two-dimensional stratification by a mode-1 internal wave

Wave Motion ◽  
2018 ◽  
Vol 83 ◽  
pp. 227-240
Author(s):  
Jianjun Liang ◽  
Tao Du ◽  
Xiaoming Li ◽  
Mingxia He
Keyword(s):  
Internal Wave ◽  
Internal Waves ◽  
Two Dimensional ◽  
Mode 2

scholarly journals Bispectral Analysis of Energy Transfer within the Two-Dimensional Oceanic Internal Wave Field

2005 ◽  
Vol 35 (11) ◽  
pp. 2104-2109 ◽  
Author(s):  
Naoki Furuichi ◽  
Toshiyuki Hibiya ◽  
Yoshihiro Niwa
Keyword(s):  
Internal Wave ◽  
Wave Field ◽  
Internal Waves ◽  
Internal Tide ◽  
Energy Cascade ◽  
Minor Role ◽  
Two Dimensional ◽  
Bispectral Analysis ◽  
Internal Wave Field ◽  
Oceanic Internal Wave

Abstract Bispectral analysis of the numerically reproduced spectral responses of the two-dimensional oceanic internal wave field to the incidence of the low-mode semidiurnal internal tide is performed. At latitudes just equatorward of 30°, the low-mode semidiurnal internal tide dominantly interacts with two high-vertical-wavenumber diurnal (near inertial) internal waves, forming resonant triads of parametric subharmonic instability (PSI) type. As the high-vertical-wavenumber near-inertial energy level is raised by this interaction, the energy cascade to small horizontal and vertical scales is enhanced. Bispectral analysis thus indicates that energy in the low-mode semidiurnal internal tide is not directly transferred to small scales but via the development of high-vertical-wavenumber near-inertial current shear. In contrast, no noticeable energy cascade to high vertical wavenumbers is recognized in the bispectra poleward of ∼30° as well as equatorward of ∼25°. A new finding is that, although PSI is possible equatorward of ∼30°, the efficiency drops sharply as the latitude falls below ∼25°. At all latitudes, another resonant interaction suggestive of induced diffusion is found to occur between the low-mode semidiurnal internal tide and two high-frequency internal waves, although bispectral analysis shows that this interaction plays only a minor role in cascading the low-mode semidiurnal internal tide energy.

The temporal variability of near-inertial internal waves in an internal tide beam

2021 ◽  
Author(s):  
Jonas Löb ◽  
Monika Rhein
Keyword(s):  
Internal Wave ◽  
Internal Waves ◽  
Temporal Variability ◽  
Internal Tide ◽  
Internal Tides ◽  
Inertial Waves ◽  
Energy Fluxes ◽  
Wind Event ◽  
Mode 2 ◽  
Inertial Energy

<p>Low mode internal waves in the stratified ocean are generated by the interaction between barotropic tides and seafloor topography and by the wind field in the near-inertial range. They are crucial for interior mixing and for the oceanic energy pathways, since they carry a large portion of the energy of the entire internal wave field. Long-term observations of energy fluxes of internal waves are sparse. The aim of this work is to study the temporal variability of wind generated low mode near-inertial internal waves inside an internal tide beam emanating from seamounts south of the Azores. For this, 20 months of consecutive mooring observations are used to calculate the mode 1 and mode 2 near-inertial energy fluxes as well as kinetic and potential energies. The gathered time series of near-inertial internal wave energy flux is not steady due to its intermittent forcing and is neither dominated by either mode 1 or mode 2. It shows a peak induced by a distinct strong wind event which is directly linked to wind-power input into the mixed layer north-east of the mooring location, and allows a comparison between the wind event and a background state. Furthermore, indications of non-linear interactions of the near-inertial waves with the internal tides in the form of resonant triad interaction and non-linear self-interaction have been found. This study provides new insights on the relative importance of single wind events and reinforces the assumption of a global non-uniform distribution of near-inertial energy with emphasis in regions where these events occur often and regularly. It furthermore displays its importance to be adequately incorporated into ocean general circulation models and in generating ocean mixing estimates by near-inertial waves as a similarly important component next to the internal tides.</p>

Spectra and Coherence of Wind-Generated Internal Waves

1976 ◽  
Vol 33 (10) ◽  
pp. 2323-2328 ◽  
Author(s):  
R. H. Käse ◽  
C. L. Tang
Keyword(s):  
Energy Density ◽  
Internal Wave ◽  
Internal Waves ◽  
Wind Stress ◽  
Wave Mode ◽  
Wave Number ◽  
Small Scale ◽  
Two Dimensional ◽  
Scale Turbulence ◽  
Main Thermocline

On the basis of a model for an internal wave field that is generated by a randomly varying isotropic wind stress and in which energy is transferred to small-scale turbulence, we derive the two-dimensional energy density function. The coherence scales are determined by the highest order internal wave mode that is not affected by virtual friction in the main thermocline, provided the curl of the wind stress has a white noise wave number spectrum. In general, this mode number scale is increasing monotonically with frequency. As a result of such a frequency dependent mode bandwidth, the vertical coherence drops with increasing frequency.

The limiting form of internal waves

1984 ◽  
Vol 394 (1807) ◽  
pp. 329-344 ◽  
Keyword(s):  
Free Surface ◽  
Internal Wave ◽  
Internal Waves ◽  
Solitary Waves ◽  
The Other ◽  
Stokes Wave ◽  
Internal Solitary Waves ◽  
Two Dimensional ◽  
Extreme Form ◽  
Eddy Formation

The bifurcation of two-dimensional internal solitary waves in a perfect density stratified fluid between horizontal walls under gravity is studied near to a point of incipient eddy formation. It is shown that eddies do not attach to the walls. Moreover, along the bifurcating branch there is always a flow with a singular cusped streamline before the formation of eddies. This flow with the cusped streamline is an example of what we call an internal wave of limiting form, by analogy with the Stokes wave of extreme form in the free surface problem. Two examples are given where the primary density stratification ensures the existence of a limiting wave of depression in one case, and of elevation in the other.

Interference and transmission of spatiotemporally locally forced internal waves in non-uniform stratifications

2019 ◽  
Vol 866 ◽  
pp. 350-368
Author(s):  
Rohit Supekar ◽  
Thomas Peacock
Keyword(s):  
Experimental Study ◽  
Internal Wave ◽  
Group Velocity ◽  
Internal Waves ◽  
Laboratory Experiments ◽  
Model Analysis ◽  
Destructive Interference ◽  
Two Dimensional ◽  
Wave Fields ◽  
Spatiotemporal Localization

Studies of the effects of constructive or destructive interference on the transmission of internal waves through non-uniform stratifications have typically been performed for internal wave fields that are spatiotemporally harmonic. To understand the impacts of spatiotemporal localization, we present a theoretical and experimental study of the transmission of two-dimensional internal waves that are generated by a boundary forcing that is localized in both space and time. The model analysis reveals that sufficient localization leads to the disappearance of transmission peaks and troughs that would otherwise be present for a harmonic forcing. The corresponding laboratory experiments that we perform provide clear demonstration of this effect. Based on the group velocity and angle of propagation of the internal waves, a practical criterion that assesses when the transmission peaks or troughs are evident is obtained.

An analogy between electromagnetic and internal waves

2019 ◽  
Vol 485 (4) ◽  
pp. 428-433
Author(s):  
V. G. Baydulov ◽  
P. A. Lesovskiy
Keyword(s):  
Angular Momentum ◽  
Conservation Laws ◽  
Internal Wave ◽  
Special Relativity ◽  
Internal Waves ◽  
Maxwell Equations ◽  
Wave Equations ◽  
Lagrange Function ◽  
Lorentz Transformations ◽  
Symmetry Transformations

For the symmetry group of internal-wave equations, the mechanical content of invariants and symmetry transformations is determined. The performed comparison makes it possible to construct expressions for analogs of momentum, angular momentum, energy, Lorentz transformations, and other characteristics of special relativity and electro-dynamics. The expressions for the Lagrange function are defined, and the conservation laws are derived. An analogy is drawn both in the case of the absence of sources and currents in the Maxwell equations and in their presence.

Density Wave Measurements in a Rectangular Clarifier

1983 ◽  
Vol 18 (1) ◽  
pp. 129-150 ◽  
Author(s):  
Mark K. Watson ◽  
R.R. Hudgins ◽  
P.L. Silveston
Keyword(s):  
Power Spectrum ◽  
Internal Wave ◽  
Internal Waves ◽  
Wave Motion ◽  
Wave Amplitude ◽  
Suspended Solids ◽  
Small Volume ◽  
Density Wave ◽  
Measure Concentration ◽  
Wave Measurements

Abstract Internal wave motion was studied in a laboratory rectangular, primary clarifier. A photo-extinction device was used as a turbidimeter to measure concentration fluctuations in a small volume within the clarifier as a function of time. The signal from this device was fed to a HP21MX minicomputer and the power spectrum plotted from data records lasting approximately 30 min. Results show large changes of wave amplitude as frequency increases. Two distinct regions occur: one with high amplitudes at frequencies below 0.03 Hz, the second with very small amplitudes appears for frequencies greater than 0.1 Hz. The former is associated with internal waves, the latter with flow-generated turbulence. Depth, velocity in the clarifier and inlet suspended solids influence wave amplitudes and the spectra. A variation with position or orientation of the probe was not detected. Contradictory results were found for the influence of flow contraction baffles on internal wave amplitude.

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