Tag: vortex rings

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Knots and Streaks – Where to Find Them

https://www.researchgate.net/publication/348578523

Knots, upwellings, and streaks form in the wakes of spilling breaking waves. Knots are due to the shedding of intense monopoles, dipoles, tripoles, and quadrupoles (Dommermuth, 2021a,b). Upwellings are due to eddys and vortex rings (Dommermuth, 2021b). Streaks of foam collect in interstitial regions where vorticity of opposite sign connects normal to the free surface (Dommermuth, 2020g). Knots, upwellings, and streaks are visible in Fitzpatrick’s (2014) YouTube video of a North Sea storm. Fitzpatrick’s (2014) video is annotated and comparisons are made to Dommermuth (2020c,g, 2021a,b)’s numerical simulations. The presence of knots in storm seas provides evidence that an inverse energy cascade is present in spilling breaking waves.

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Frequency Downshifting and Inverse Energy Cascades

https://www.researchgate.net/publication/348419601

The occurrence of frequency downshifting and angular spreading under the influence of Benjamin-Feir instabilities and spilling breaking waves is confirmed. Knots and upwellings form on the free surface in the wake of spilling breaking waves. Upwellings are due to vortex rings. Knots are due to intense monopoles, dipoles, tripoles, and quadrupoles. Coherent structures in the ocean and atmosphere resonate with oblique wave modes. Whitecaps indicate that frequency downshifting and angular spreading are occurring-just as windrows and knots indicate the presence of an inverse energy cascade 

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Meandering Flows in the Oceanic and Atmospheric Boundary Layers due to Breaking Ocean Waves

https://www.researchgate.net/publication/344482927

Breaking waves generate meandering currents and winds in the oceanic and atmospheric boundary layers (Dommermuth et al., 2014). Meandering flows are revisited here for five types of breaking waves. Streaming flows are mean flows that include Eulerian and Lagrangian contributions. Meandering flows include both difference (streaming) and sum frequency interactions. Meandering flows, like streaming flows, have Eulerian and Lagrangian contributions. Normal to the free surface, the meandering flows exponentially attenuate away from the free surface with an oscillatory behavior. The magnitudes of the meandering flows agree with Langmuir’s original observations (Langmuir, 1938). The good agreement suggests that the formation of Langmuir circulations is due to meandering flows.… Read more

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Magnetic Induction due to the Effects of Breaking Ocean Waves

https://www.researchgate.net/publication/344482876

Breaking waves generate meandering currents and winds in the oceanic and atmospheric boundary layers. The length scales and frequencies of the meandering currents and winds are respectively longer and higher than those of the underlying ocean waves. The difference in spatial and temporal scales makes it possible to indirectly measure the meandering current in the oceanic boundary layer using the principles of magnetic induction that would otherwise be difficult using more direct methods. Such measurements are desirable to quantify mixing in the oceanic and atmospheric boundary layers due to meandering flows.

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The Generation of Electric Fields by Meandering Flows

https://www.researchgate.net/publication/344787449

Meandering flows are wave driven much like streaming flows. The interaction of the wavy portion of the flow with the vortical portion of the flow gives rise to meandering flows. Meandering flows, like streaming flows, are not turbulent. The nonlinear wave interactions give sum and difference frequencies in meandering flows. The difference frequencies have long been associated with streaming flows in the ocean (Longuet-Higgins, 1953). Meandering flows occur in the atmosphere as well as the ocean. Streaming flows are a subset of meandering flows. Meandering flows are expected to vary over long distances due to nonlinear wave interactions, variations in currents and winds, etc. In the upper ocean, (Dommermuth, 2020d) shows that slow variations of the meandering wind-drift interacting with the earth’s magnetic field induces a magnetic disturbance in the upper ocean and lower atmosphere. Dommermuth (2018b,c,d,e) show how the wind drift affects wave breaking. Here, the effects of variations in the meandering wind drift and meandering wind on the surface charge density are considered. Blanchard (1963); Gathman (1986) show that the surface charge density is due to the electrification of the atmosphere by (1) bubbles bursting on the ocean surface due to the effects of wave breaking and (2) sea spray torn off the crests of waves by wind shear. The variations in surface charge density are expected due to variations in wave breaking and wind shear occurring over long spatial scales due to meandering flows. This paper along with Dommermuth (2020d) provide experimentalists with bases for measuring effects of meandering flows on the magnetic and electric fields in the ocean and atmosphere. Experiments can be performed to confirm the existence of meandering flows and to quantify the mixing of the upper ocean and lower atmosphere. During fair weather the electric field that is generated by the effect of meandering flows on the surface charge density is about 10% of the potential gradient at altitudes 3km above the ocean surface. The effects of the electric disturbance attenuate slowly with altitude at a rate that is very similar to the potential gradient. The frequencies of oscillations are about 0.2-1Hz due to nonlinear sum-frequency wave interactions. During a storm the electric field that is generated by the meandering flows would become increasingly violent with significant energy being radiated within specific frequency bands in an organized manner.