Focusing of mode-2 internal solitary-like waves: an unexpected extreme internal wave

2021 ◽  
Author(s):  
Nicolas Castro-Folker ◽  
Christopher Subich ◽  
Marek Stastna
Keyword(s):  
Internal Wave ◽  
Numerical Simulations ◽  
Mode 2 ◽  
Resolution Requirements

<p>We report on numerical simulations of stratified adjustment that yield radially propagating mode-2 waves. The initial inward propagating mode-2 wave increases in amplitude, but it does not lead to significant overturning even during the period of self-interaction near the origin. However, post-focusing, the pycnocline thins and secondary waves propagate into an environment that is very different from the undisturbed stratification. These resulting waves break, and create intrusions above and below the thinned pycnocline. While most experimental realizations of extreme internal solitary-like waves use a rectangular geometry, it should be possible to realize this situation experimentally. We discuss the resolution requirements of this situation, as well as irreversible mixing.</p>

scholarly journals Resolution requirements for numerical simulations of transition

1989 ◽  
Vol 4 (2) ◽  
pp. 197-217 ◽  
Author(s):  
Thomas A. Zang ◽  
Steven E. Krist ◽  
M. Yousuff Hussaini
Keyword(s):  
Numerical Simulations ◽  
Resolution Requirements

scholarly journals Numerical simulations of internal wave generation by convection in water

2015 ◽  
Vol 91 (6) ◽  
Author(s):  
Daniel Lecoanet ◽  
Michael Le Bars ◽  
Keaton J. Burns ◽  
Geoffrey M. Vasil ◽  
Benjamin P. Brown ◽  
...  
Keyword(s):  
Internal Wave ◽  
Numerical Simulations ◽  
Wave Generation ◽  
Internal Wave Generation

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>

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 Simulations of nonlinear harmonic generation by an internal wave beam incident on a pycnocline

2014 ◽  
Vol 21 (4) ◽  
pp. 855-868 ◽  
Author(s):  
S. Wunsch ◽  
H. Ku ◽  
I. Delwiche ◽  
R. Awadallah
Keyword(s):  
Internal Wave ◽  
Numerical Simulations ◽  
Harmonic Generation ◽  
Nonlinear Theory ◽  
Wave Beam ◽  
Incidence Angle ◽  
Nonlinear Refraction ◽  
Weakly Nonlinear ◽  
Weakly Nonlinear Theory ◽  
Nonlinear Harmonic Generation

Abstract. Internal wave beams generated by oceanic tidal flows propagate upward and interact with the increasing stratification found at the pycnocline. The nonlinear generation of harmonic modes by internal wave beams incident on a pycnocline has recently been demonstrated by laboratory experiments and numerical simulations. In these previous studies, the harmonic modes were trapped within the pycnocline because their frequencies exceeded that of the stratified fluid below. Here, two-dimensional numerical simulations are used to explore the effect of incidence angle on harmonic generation at a thin pycnocline. At incidence angles less than 30 degrees (typical of oceanic beams), the lowest harmonic mode freely radiates in the form of an internal wave beam rather than being trapped within the pycnocline. The results indicate that nonlinear refraction is the primary mechanism for harmonic generation at incidence angles exceeding 30 degrees, but that interaction of the incident and reflected beams is more important at smaller incidence angles. The simulations are compared to weakly nonlinear theory based on refraction at the pycnocline. The results yield good agreement for trapped harmonics, but weakly nonlinear theory substantially underpredicts the amplitude of the radiated harmonics.

Internal wave excitation from stratified flow over a thin barrier

1998 ◽  
Vol 377 ◽  
pp. 223-252 ◽  
Author(s):  
BRUCE R. SUTHERLAND ◽  
PAUL F. LINDEN
Keyword(s):  
Internal Wave ◽  
Numerical Simulations ◽  
Internal Waves ◽  
Wavelet Transforms ◽  
Large Amplitude ◽  
Internal Gravity Waves ◽  
Wave Excitation ◽  
Mean Flow ◽  
Propagating Waves ◽  
The Waves

We perform laboratory experiments in a recirculating shear flow tank of non-uniform salt-stratified water to examine the excitation of internal gravity waves (IGW) in the wake of a tall, thin vertical barrier. The purpose of this study is to characterize and quantify the coupling between coherent structures shed in the wake and internal waves that radiate from the mixing region into the deep, stationary fluid. In agreement with numerical simulations, large-amplitude internal waves are generated when the mixing region is weakly stratified and the deep fluid is sufficiently strongly stratified. If the mixing region is unstratified, weak but continuous internal wave excitation occurs. In all cases, the tilt of the phase lines of propagating waves lies within a narrow range. Assuming the waves are spanwise uniform, their amplitude in space and time is measured non-intrusively using a recently developed ‘synthetic schlieren’ technique. Using wavelet transforms to measure consistently the width and duration of the observed wavepackets, the Reynolds stress is measured and, in particular, we estimate that when large-amplitude internal wave excitation occurs, approximately 7% of the average momentum across the shear depth and over the extent of the wavepacket is lost due to transport away from the mixing region by the waves.We propose that internal waves may act back upon the mean flow modifying it so that the excitation of waves of that frequency is enhanced. A narrow frequency spectrum of large-amplitude waves is observed because the feedback is largest for waves with phase tilt in a range near 45°. Numerical simulations and analytic theories are presented to further quantify this theory.

Numerical simulation of the dynamics of turbulent boundary layers: perspectives of a transition simulator

1991 ◽  
Vol 336 (1641) ◽  
pp. 95-102 ◽  
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Boundary Layers ◽  
Turbulent Boundary Layers ◽  
Simulation Methodology ◽  
Resolution Requirements

The current and prospective capabilities of numerical simulations of turbulent boundary layers are discussed. The stringent resolution requirements for resolving instantaneous structures and dynamics (rather than just for producing statistics) are emphasized. Improvements and alternatives to the prevailing simulation methodology are proposed.

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