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This article continues and generalizes the study "On the Similarity of Quasi-Geostrophic Vortices against the Background of Large-Scale Barotropic Currents" [6] (Oceanology, Zhmur, 2024, in print). In continuation of [6], a similar formulation is considered, but for other types of background currents. In the quasi-geostrophic description for small Rossby numbers, the problem of the evolution of an arbitrarily shaped liquid volume with homogeneous potential vorticity of all vortex core particles in an equidistant background flow—horizontal flow with vertical shear and equidistant flow with barotropic and baroclinic components—is presented. Ultimately, the problem boils down to an integrodifferential equation for the evolution of the vortex core boundary. The study of this equation in dimensionless form makes it possible to find a set of dimensionless parameters that determine the similarity condition of the studied vortices. [ABSTRACT FROM AUTHOR]

The paper proposes a theory of similarity of quasi-geostrophic vortices against the background of large-scale flows. This information is useful when planning laboratory and numerical experiments to study mesoscale and submesoscale vortex dynamics of vortices interacting with currents. Special attention is paid to studying geometric similarity of phenomena. It is revealed that the complete set of dimensionless similarity numbers of baroclinic vortices includes four dimensionless parameters: the dimensionless intensity of the vortex, the geometric similarity of the background flow (the ratio of the relative vorticity to the deformation coefficient of the background flow), the coefficient of horizontal stretching of the vortex core, and the coefficient of vertical oblateness of the vortex core coinciding with the Burger number. To describe the similarity of barotropic vortices against the background of barotropic flows, the number of necessary dimensionless parameters is reduced by one number: the coefficient of vertical oblateness of the vortex core is eliminated from consideration. When studying axisymmetric vortices or vortex structures close to axisymmetric, another geometric parameter of the vortex is eliminated from consideration—the coefficient of horizontal stretching of the vortex core. As a result, the maximum possible set of similarity parameters includes four dimensionless numbers, and the minimum is two. [ABSTRACT FROM AUTHOR]

Based on subsurface mooring observations and HYCOM data, a complete investigation was conducted of the near-inertial waves (NIWs) caused by Typhoon MITAG to the east of Taiwan. HYCOM data were mainly used to reveal the role played by anticyclonic eddies in the propagation of NIWs. The results show that most typhoon-generated NIWs propagate towards negative vorticity, and NIWs near the edge gradually accumulated towards the eddy center and down to 800 m. NIWs propagating through the thermocline to the deep ocean were mainly concentrated in the eddy, and the near-inertial energy flux showed a significant enhancement from 400 to 600 m. Moreover, the downwards propagation of NIWs in the eddy enhanced the kinetic energy of background flow. NIWs outside the anticyclonic eddy dissipated quickly, while inside the eddy, there were high value areas of e-folding time. Dynamic mode decomposition illustrates that the anticyclonic eddy mainly captures higher modes of NIWs, and the state of continuous energy growth of higher modes can be maintained for more than a week. In addition, NIWs can also be carried westwards by the advection of the mean background flow at the eddy’s edge.

Based on the daily Japanese 55-yr reanalysis data, this study analyzes the maintenance mechanism for 53 boreal winter blocking highs around the Ural Mountains (UBHs) during 1958–2018 based on the atmospheric energy budget equations. After decomposing the circulation into background flow, low-frequency anomalies, and high-frequency eddies, it was found that the interaction between the background flow and low-frequency anomalies is conducive to the maintenance of the UBHs. Due to the southwestward gradient in the climatological mean air temperature over the Eurasian continent, it is easy for the air temperature anomalies as well as the wind velocity anomalies in the middle and lower troposphere induced by the UBHs to facilitate the positive conversion of baroclinic energy associated with the background flow into the UBHs. Likewise, the conversion of barotropic energy associated with the background flow is also evident in the upper troposphere, in which the climatological mean westerlies have evident southward gradient to the northwest of Lake Baikal and southwestward gradient over Barents Sea. Note that the conversion of baroclinic energy associated with the background flow is dominant throughout the lifecycle of UBHs, acting as the major contributor to the maintenance of the UBHs. Although transient eddies facilitate maintenance of the UBHs via positive conversion of barotropic energy in the middle and upper troposphere, they hinder the maintenance of UBHs via negative conversion of baroclinic energy in the lower troposphere. The diabatic heating anomalies tend to counteract the local air temperature anomalies in the middle and lower troposphere, which damps the available potential energy of UBHs and acts as a negative contributor to the UBHs. [ABSTRACT FROM AUTHOR]

In order to analyze the effect of the background flow on the sound prediction of fine-scale turbulence noise, the sound spectra from static and flow environments are compared. It turns out that, the two methods can obtain similar predictions not only at 90 deg to the jet axis but also at mid- and high frequencies in other directions. The discrepancies of predictions from the two environments show that the effect of the jet flow on the sound propagation is related to low frequencies in the downstream and upstream directions. It is noted that there is an obvious advantage of computational efficiency for calculating in static environment, compared with that in flow environment. A good agreement is also observed to some extent between the predictions in static environment and measurements of subsonic to supersonic. It is believed that the predictions in static environment could be an effective method to study the propagation of the sound in jet flow and to predict the fine scale turbulence noise accurately in a way as well. [ABSTRACT FROM AUTHOR]

Abstract We study the Propagation and damping properties of Alfvén gravity waves in the presence of the vertical magnetic field in the viscous solar plasma under influence of the background flow by deriving a fourth order dispersion relation in terms of the Doppler shifted frequency. We derive the dispersion relation under WKB and Boussinesq approximation. We study the damping of Alfvén gravity waves for the wave frequencies less than and greater than the Brunt-Väisälä frequency. We find that the Brunt-Väisälä frequency divides the frequency ranges where the weakly or strongly damped oscillations occur. The background flow exhibits a strong effect on weakly damped oscillations and a weak effect on the strongly damped oscillations. We also notice that the damping of both the strong and weakly damped oscillations depend on the Brunt-Väisälä frequency and wave number. The effect of the background flow is also being governed by the Brunt-Väisälä frequency and wave number. We also study the properties of gravity wave mode after filtering the Alfvén wave mode by minimizing the magnetic field and noticed that the background flow shows a very strong effect on the gravity wave mode. [ABSTRACT FROM AUTHOR]

The well-known background flow method for finding bounds for time-averaged characteristics of dynamical systems, proposed by Doering and Constantin (1994, 1995) is a special case of the auxiliary functional method of Chernyshenko et al. (2014). Chernyshenko (2022) proved that bounds obtained by the direct method described by Seis (2015) can be obtained also by the auxiliary functional method and, therefore, by the background flow method when the auxiliary functional is quadratic. This brief note outlines the technique by which the background flow and more generally the auxiliary functional can be obtained when a proof of a bound for infinite time average by the direct method is known, by applying this technique to the case of the bound on the Nusselt number for infinite-Prandtl-number Rayleigh–Bénard convection obtained by Otto and Seis (2011). • Bound on Nusselt number for Rayleigh–Bénard convection is rederived. • Auxiliary functional and background flow for the bound are found. • Recent Otto and Seis approach reduced to background flow method. [ABSTRACT FROM AUTHOR]

We study the effect of background flow on the dissolution and transport of carbon dioxide (CO2) during geological storage in saline aquifers, and include the processes of diffusion, advection, and free convection. We develop a semianalytical model that captures the evolution of the dissolution in the absence of free convection. Using the semianalytical solution, we determine scaling relations for the steady rate of dissolution that follow either [ABSTRACT FROM AUTHOR]

Numerical simulations are used to study laminar vortex ring formation under the influence of background flow. The numerical setup includes a round-headed axisymmetric body with an opening at the posterior end from which a column of fluid is pushed out by a piston. The piston motion is explicitly included into the simulations by using a deforming mesh. A well-developed wake flow behind the body together with a finite-thickness boundary layer outside the opening is taken as the initial flow condition. As the jet is initiated, different vortex evolution behavior is observed depending on the combination of background flow velocity to mean piston velocity ( $$U/U_{p}$$ ) ratio and piston stroke to opening diameter ( $$L_{m}/D$$ ) ratio. For low background flow ( $$U/U_{p} =0.2$$ ) with a short jet ( $$L_{m}/D =6$$ ), a leading vortex ring pinches off from the generating jet, with an increased formation number. For intermediate background flow ( $$U/U_{p} =0.5$$ ) with a short jet ( $$L_{m}/D =6$$ ), a leading vortex ring also pinches off but with a reduced formation number. For intermediate background flow ( $$U/U_{p} =0.5$$ ) with a long jet ( $$L_{m}/D =15$$ ), no vortex ring pinch-off is observed. For high background flow ( $$U/U_{p} =0.75$$ ) with both a short ( $$L_{m}/D =6$$ ) and a long ( $$L_{m}/D =15$$ ) jet, the leading vortex structure is highly deformed with no single central axis of fluid rotation (when viewed in cross-section) as would be expected for a roll-up vortex ring. For $$L_{m}/D =6$$ , the vortex structure becomes isolated as the trailing jet is destroyed by the opposite-signed vorticity of the background flow. For $$L_{m}/D =15$$ , the vortex structure never pinches off from the trailing jet. The underlying mechanism is the interaction between the vorticity layer of the jet and the opposite-signed vorticity layer from the initial wake. This interaction depends on both $$U/U_{p}$$ and $$L_{m}/D$$ . A comparison is also made between the thrust generated by long, continuous jets and jet events constructed from a periodic series of short pulses having the same total mass flux. Force calculations suggest that long, continuous jets maximize thrust generation for a given amount of energy expended in creating the jet flow. The implications of the numerical results are discussed as they pertain to adult squid propulsion, which have been observed to generate long jets without a prominent leading vortex ring. [ABSTRACT FROM AUTHOR]