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In this paper, we study the time‐dependent vorticity–velocity–pressure formulation of Stokes problem in two‐ and three‐dimensional domains provided with nonstandard boundary conditions, related to the normal component of the velocity and the tangential components of the vorticity. This problem is discretized by implicit Euler's scheme in time and spectral method in space. We prove an optimal error estimate for the three unknowns. [ABSTRACT FROM AUTHOR]

In this work, the doubly periodic shear layers are employed to underpin the vortex dynamics associated with the perturbed free shear layers using the lattice Boltzmann method with the Bhatnagar–Gross–Krook collision model. The effect of (i) width between shear layers, (ii) modes of perturbation, (iii) the strength of perturbation, and (iv) thickness of a shear layer on roll-up formation, vortex interactions, pairings, and the generation of thin filaments is studied in detail with the evolution kinetic energy, enstrophy, and palinstrophy for Reynolds number, Re = 30 , 000 . The formation of thin vorticity braids and vortex merging causes the production of vorticity gradients and a rise in the palinstrophy. No compelling interplay is observed with corotating or counter-rotating vortices for a minimum separation distance ( S 1 ) between two opposite vorticity strips. The counter-force from each layer creates a jet whose properties differ from those of a single shear layer. However, the evolution of multiple pairs of shear layers produces smaller vortices of lower strength and enhances the growth of palinstrophy and decay of kinetic energy and enstrophy. The rise in the momentum thickness is observed for the interactive flows ( S 2 ≤ S 1 ), while the non-interactive flow ( S 2 > S 1 ) shows constant momentum thickness. The increased perturbation strength quickens the roll-up of shear layer and enhances the growth of palinstrophy. Thick shear layers evolves with dipole-like structures and slows down the decay of kinetic energy and enstrophy compared to thin shear layer flows. It generates family of thin vortex filaments and influences the rapid growth of vorticity gradients and positive Okubo–Weiss-Q-quantity. [ABSTRACT FROM AUTHOR]

Upwelling along the western boundary of the major ocean basin subtropical gyres has been diagnosed in a wide range of ocean models and state estimates. This vertical transport is O(5 × 106) m3 s−1, which is on the same order of magnitude as the downward Ekman pumping across the subtropical gyres and zonally integrated meridional overturning circulation. Two approaches are used here to understand the reason for this upwelling and how it depends on oceanic parameters. First, a kinematic model that imposes a density gradient along the western boundary demonstrates that there must be upwelling with a maximum vertical transport at middepths in order to maintain geostrophic balance in the western boundary current. The second approach considers the vorticity budget near the western boundary in an idealized primitive equation model of the wind- and buoyancy-forced subtropical and subpolar gyres. It is shown that a pressure gradient along the western boundary results in bottom pressure torque that injects vorticity into the fluid. This is balanced on the boundary by lateral viscous fluxes that redistribute this vorticity across the boundary current. The viscous fluxes in the interior are balanced primarily by the vertical stretching of planetary vorticity, giving rise to upwelling within the boundary current. This process is found to be nearly adiabatic. Nonlinear terms and advection of planetary vorticity are also important locally but are not the ultimate drivers of the upwelling. Additional numerical model calculations demonstrate that the upwelling is a nonlocal consequence of buoyancy loss at high latitudes and thus represents an integral component of the meridional overturning circulation in depth space but not in density space. Significance Statement: The purpose of this study is to better understand what is forcing water to upwell along the western boundary at midlatitudes of the major ocean basins. This is a potentially important process since upwelling can bring heat and nutrients closer to the surface, where they can be exchanged with the atmosphere. Also, since ocean currents vary with depth, pathways followed in the upper ocean are different from those found for the deeper ocean, so the amount and location of upwelling influence where these waters go. Idealized numerical models and theory are used to demonstrate that the upwelling is ultimately driven by density changes along the western boundary of the basin that result from heat loss at high latitudes. [ABSTRACT FROM AUTHOR]

In this work, we compare and contrast the phenomenological changes in passive tracer dispersion at asymptotically small to O(1) Rossby numbers using idealized two-dimensional flows generated by a two-vertical-mode model. With increasing flow Rossby numbers, we find that the forward flux of tracer variance increases monotonically and the tracer variance spectra show severe depletion of the tracer field, indicating enhanced stirring of the tracer by higher Rossby number flows. On examining the physical structure of the tracer flux and its connection to strain- and vorticity-dominant regions in the flow, we find that a major share of the tracer flux is located in high-shear, strain-dominant regions between coherent vortices at low Rossby numbers, while at higher Rossby numbers, the tracer flux is primarily located in vorticity-dominant regions that are composed of fragmented bits of vorticity. The tracer field is anticorrelated with the tracer flux, i.e., tracer variance is higher in physical regions where tracer flux is lower and vice versa. Our results highlight multiple anisotropic features of submesoscales that enhance tracer dispersion at O(1) Rossby numbers and emphasize the need to take these into account while developing parameterizations for large-scale models. [ABSTRACT FROM AUTHOR]

This article deals with the error analysis of a Galerkin‐mixed finite element methods for the advection–reaction–diffusion Brinkman flow in porous media. Numerical methods for incompressible miscible flow in porous media have been studied extensively in the last several decades. In practical applications, the lowest‐order Galerkin‐mixed method is the most popular one, where the linear Lagrange element is used for the concentration and the lowest‐order Raviart–Thomas element, the lowest‐order Nédélec edge element and piece‐wise constant discontinuous Galerkin element are used for the velocity, vorticity and pressure, respectively. The existing error estimate of this lowest‐order finite element method is only O(h)$$ O(h) $$ for all variables in spatial direction, which is not optimal for the concentration variable. This paper focuses on a new and optimal error estimate of a linearized backward Euler Galerkin‐mixed FEMs, where the second‐order accuracy for the concentration in spatial directions is established unconditionally. The key to our optimal error analysis is a new negative norm estimate for Nédélec edge element. Moreover, based on the computed numerical concentration, we propose a simple one‐step recovery technique to obtain a new numerical velocity, vorticity and pressure with second‐order accuracy. Numerical experiments are provided to confirm our theoretical analysis. [ABSTRACT FROM AUTHOR]

Previous observations and modeling studies showed that tropical cyclones (TCs) in a sheared environment develop an asymmetric boundary layer (BL). While the relationship between the BL asymmetries and environmental shear has been demonstrated, the exact cause of these BL asymmetries and the phase relationship between them are less well understood. In this study, we examine the dynamical processes leading to the asymmetric structure of the TC BL in a sheared environment using idealized, convection-permitting model simulations. Our results show that the emergence of the BL asymmetries is closely linked to the TC vortex tilt and rainband processes. Specifically, stratiform diabatic processes in the downtilt-left region result in midlevel descending inflow, which brings midtropospheric, low-θE air toward the BL and forms a surface cold pool in the downtilt-left quadrant. This descending inflow also advects high absolute angular momentum inward, redistributing the vertical vorticity and causing a storm-scale tangential wind acceleration within the downtilt-left quadrant. As the BL low-θE air advances inward, it becomes supergradient and decelerates radially, forming BL outflow in the uptilt-left quadrant. The outflow advects positive relative vorticity uptilt, forming an elliptic BL vorticity and circulation structure. As the tilted TC vortex and the accompanying rainband precess cyclonically over time, the above sequence of events and the resultant BL asymmetries also precess cyclonically, maintaining a quasi-stationary configuration relative to the vortex tilt. These results suggest that the primary organizing factor of the boundary layer asymmetries is the tilted vortex structure and not strictly the environmental shear direction. [ABSTRACT FROM AUTHOR]

This study investigated the effect of a mixed obstacle layout on the deflagration mechanism of propane--air premixed gases. Most previous studies focused on a single type of obstacle, changing the shape and number of the obstacles to observe the effect on the flame deflagration characteristics. However, in real explosion accident sites, obstacles are often a mixture of different types. Little literature exists on the deflagration characteristics of hybrid barriers in semiconfined spaces. In this paper, the deflagration characteristics of propane-air premixed gas with a mixed structure of hurdles and square obstacles was studied. First, the effectiveness of numerical simulations was demonstrated by comparing experimental and large eddy simulation (LES) results for the flame dynamics with a single flat plate obstacle. Based on this, the flame behavior for different layouts of square obstacles in a mixed obstacle configuration was further simulated using the large eddy simulation method, focusing on the flame behavior, overpressure characteristics, and flow field structure in the vicinity of the obstacle. The results showed that a mixed obstacle promoted flame evolution more than a single obstacle when the square obstacle was within a critical distance from the ignition source location at the same moment in time. When the flame front crossed the first hurdle-type obstacle, the flame pattern spread in a "cat's paw" pattern to the unburned portion of the tube. In addition, the increased distance of the square obstacle from the ignition source did not allow the peak overpressure and the peak rate of overpressure rise to show a positive feedback mechanism. Finally, the strength of the vorticity in the flow field was positively correlated with the distance of the square obstacle from the ignition source. The results of study provide theoretical for the prevention of explosions. [ABSTRACT FROM AUTHOR]

We revisit Yudovich's well-posedness result for the 2-dimensional Euler equations for an inviscid incompressible fluid on either a sufficiently regular (not necessarily bounded) open set Ω ⊂ R 2 or on the torus Ω = T 2 . We construct global-in-time weak solutions with vorticity in L 1 ∩ L ul p and in L 1 ∩ Y ul Θ , where L ul p and Y ul Θ are suitable uniformly-localized versions of the Lebesgue space L p and of the Yudovich space Y Θ respectively, with no condition at infinity for the growth function Θ . We also provide an explicit modulus of continuity for the velocity depending on the growth function Θ . We prove uniqueness of weak solutions in L 1 ∩ Y ul Θ under the assumption that Θ grows moderately at infinity. In contrast to Yudovich's energy method, we employ a Lagrangian strategy to show uniqueness. Our entire argument relies on elementary real-variable techniques, with no use of either Sobolev spaces, Calderón–Zygmund theory or Littlewood–Paley decomposition, and actually applies not only to the Biot–Savart law, but also to more general operators whose kernels obey some natural structural assumptions. [ABSTRACT FROM AUTHOR]

We show that the winter Beaufort High (BH) index defined by sea level pressure (SLP) has a robust negative trend under the scenarios SSP5‐8.5 and SSP2‐4.5, with a reduction by about 5 hPa and 2 hPa, respectively, by the end of the 21st century. The negative trends in the BH SLP are associated with the changes in the background SLP over the Arctic basin. However, the vorticity of the winter BH tends to intensify under SSP5‐8.5, but shows no robust increase under SSP2‐4.5. The intensification is associated with the enhanced ridge over the Western Arctic. Therefore, it is necessary to take into account the dynamic aspects of the BH, such as vorticity. Based on this assessment, under the most likely emissions scenario, the winter BH is likely to weaken through the 21st century, in terms of SLP, but shows no robust changes in term of vorticity. Plain Language Summary: We used the latest IPCC global climate model outputs to investigate the wintertime changes in the Beaufort High (BH). Under the climate change scenarios, during winter, the sea level pressure (SLP) over the BH region is expected to decrease. The SLP reduction is up to 5 hPa by the end‐of‐the‐century. Thus, the BH seems to become weaker. However, its vorticity tends to increase under SSP5‐8.5, mostly due to the intensification of the ridge over the western North America. Key Points: The Beaufort High (BH) index defined by sea level pressure (SLP) decreases under warming climate scenariosMeanwhile, the BH vorticity tends to intensify due to the change in the ridge over the Western ArcticBesides the SLP, impact studies of the BH on the Arctic Ocean need to consider its dynamics such as vorticity [ABSTRACT FROM AUTHOR]

This study investigates the background rotational influences on the secondary eyewall formation (SEF) in tropical cyclones (TCs) in quiescent f‐plane environments. For given initial structures, simulated vortices tend to experience earlier SEF at lower latitudes. Yet the size of the secondary eyewall does not change monotonically with the latitudes. Specifically, ∼20°N provides the optimal amount of background rotation for the largest secondary eyewall size without considering other environmental forcings. Different background rotation rates affect SEF mainly by modulating the outer‐core convection as well as the wind structures. Specifically, the lower rotation rate causes more outer‐core surface fluxes, thus facilitating the outer rainbands (ORBs) at larger radii. Yet the secondary eyewall does not necessarily form at larger radii at lower latitudes since the transition from the ORBs to secondary eyewall is localized in a region of boundary layer (BL) convergence preceded by accelerated tangential winds. Budget analysis reveals that the differences in the acceleration of outer‐core tangential winds among vortices at different latitudes are dominated by the radial flux of absolute vorticity. Due to the non‐uniform influences of background rotation on the BL inflow and absolute vorticity, the most efficient spin‐up of outer‐core tangential winds is achieved at a medium latitude of 20°N, which leads up to SEF at the largest radii. By comparison, for TCs at lower (higher) latitudes, the lower outer‐core absolute vorticity (radial inflow) limits the acceleration of outer‐core tangential winds, thus placing SEF at smaller radii. Plain Language Summary: Secondary eyewall formation (SEF) and eyewall replacement cycles often cause intensity oscillation and size growth in intense tropical cyclones (TCs). Predicting SEF is difficult, since it is influenced by both internal TC dynamics and external forcings from the environment. In this study, we find the time and location of SEF are sensitive to the background rotation associated with different latitudes in idealized f‐plane simulations. Specifically, SEF tends to occur earlier at lower latitudes as a lower rotational rate facilitates faster organization of outer rainbands. But the largest secondary eyewall occurs under a moderate background rotational rate (∼20°N) facilitated by the fastest accelerations of outer‐core tangential winds. These findings indicate that the background rotation affects SEF by modulating the outer‐core convection and wind structure of TCs, which are expected to enhance the understanding of the interaction between internal and external dynamics of SEF. Key Points: Secondary eyewall formation (SEF) is affected by background rotation rates of different latitudes in idealized f‐plane simulationsLower latitude facilitates earlier SEF and 20°N provides the optimal amount of background rotation for secondary eyewall sizeBackground rotation rates affect SEF by modulating the activities of outer rainbands and the wind structures [ABSTRACT FROM AUTHOR]

The Surface Water and Ocean Topography (SWOT) mission provides a good opportunity to study fine‐scale processes in the global ocean but whether it can detect balanced submesoscale eddies is uncertain due to the "contamination" by unbalanced inertial gravity waves. Here, based on concurrent observations from SWOT and a mooring array in the northwestern Pacific, we successfully captured two submesoscale cyclonic eddies with negative sea level anomalies (SLAs) in spring 2023. We find that the SLA amplitude and equivalent radius of the first (second) eddy are 2.5 cm and 16.0 km (2.0 cm and 18.8 km), respectively. For both eddies, their vertical scales are around 150 m and their horizontal velocities and Rossby numbers exceed 15.0 cm/s and 0.4, respectively. Further analysis suggests that similar submesoscale eddies can commonly occur in the northwestern Pacific and that SWOT is capable to detect larger submesoscale eddies with scales greater than ∼10 km. Plain Language Summary: The Surface Water and Ocean Topography (SWOT) mission measures sea surface heights with a spatial resolution an order of magnitude higher than the prior nadir altimetry missions. However, whether SWOT can detect oceanic submesoscale eddies that play key roles in oceanic energy cycle and vertical material transports, is uncertain. To investigate this issue, we deployed a mooring array beneath a SWOT orbital swath in the northwestern Pacific. Based on the concurrent SWOT and mooring data, we successfully captured two submesoscale cyclonic eddies in spring 2023. Radii of the submesoscale eddies are found to be between 10 and 20 km and their horizontal velocities exceed 15.0 cm/s. The ratio between their vertical relative vorticity and the planetary vorticity exceeds 0.4. Further analysis suggests that similar submesoscale eddies can commonly occur in the northwestern Pacific. This study demonstrates the capability of SWOT to detect submesoscale eddies in the global ocean. Key Points: Two submesoscale cyclonic eddies (SCEs) were observed by SWOT and moorings in the northwestern PacificKinematic and dynamic features of the SCEs were revealedIt is feasible to use SWOT data to detect larger submesoscale eddies in the ocean [ABSTRACT FROM AUTHOR]

A new integrating model has been developed to couple tokamak edge multiscale magnetohydrodynamic (MHD) events and transport simulations, such as edge‐localized mode (ELM) cycles. As a proof of principle, we first start from a set of three‐field two‐fluid model equations, which includes the pressure, current, and vorticity. The equations are separated into the slowly evolving part of the axisymmetric component by taking a time average of the axisymmetric component. The time‐averaged fluxes, which are quadratic in fluctuating quantities, act as driven terms for the time‐averaged axisymmetric quantities that determine the plasma transport, and therefore the large‐scale evolution of the plasma profiles. Then the HL‐2A's ELM cycles are simulated using the model. Good agreements of ELM size and pedestal recovery time have been achieved for the solutions obtained from the coupled simulation compared with experiment. For one ELM cycle simulation, the coupled code can achieve a speedup of a factor of up to 30 over standalone code. [ABSTRACT FROM AUTHOR]

We consider a two-dimensional, two-layer, incompressible, steady flow, with vorticity which is constant in each layer, in an infinite channel with rigid walls. The velocity is continuous across the interface, there is no surface tension or difference in density between the two layers, and the flow is inviscid. Unlike in previous studies, we consider solutions which are localised perturbations rather than periodic or quasi-periodic perturbations of a background shear flow. We rigorously construct a curve of exact solutions and give the leading order terms in an asymptotic expansion. We also give a thorough qualitative description of the fluid particle paths, which can include stagnation points, critical layers, and streamlines which meet the boundary. [ABSTRACT FROM AUTHOR]

Using the experimental and large eddy simulation (LES) methods, the impacts of equivalence ratio and adjacent obstacle blockage ratio on flame propagation, flame moving velocity, and explosion overpressure in a closed obstructed duct are investigated. The results indicate that the developed LES method is able to reproduce the tendency of flame propagation, flame moving velocity, and explosion overpressure of BR = 30%, 50%, 70% and BR = 70%, 50%, 30%. The early flame propagation and flame moving velocity are not affected by the first obstacle. As the explosion flame passes through the three obstacles, the flame acceleration and deceleration occur in sequence due to the decreasing cross-section and vortex-flame interaction, eventually forming three ascending peak flame moving velocity. The higher vorticity magnitude of BR = 70%, 50%, 30% and BR = 30%, 50%, 70% is mainly concentrated in the early stage and later stage of hydrogen explosion, which directly results in the fact that the flame acceleration and rise rate of explosion overpressure of BR = 70%, 50%, 30% is higher than that of BR = 30%, 50%, 70%. Additionally, the maximum value of flame moving velocity and explosion overpressure of BR = 30%, 50%, 70% is higher than that of BR = 70%, 50%, 30%. • Flame propagation and explosion overpressure are experimentally obtained. • LES method is established to predict flame propagation and explosion overpressure. • The velocity vectors and vorticity magnitude are analyzed. [ABSTRACT FROM AUTHOR]

The Gulf Stream, a major ocean current in the North Atlantic ocean is a key component in the global redistribution of heat and is important for marine ecosystems. Based on 27 years (1993–2019) of wind reanalysis and satellite altimetry measurements, we present observational evidence that the path of this freely meandering jet after its separation from the continental slope at Cape Hatteras, aligns with the region of maximum cyclonic vorticity of the wind stress field known as the positive vorticity pool. This synchronicity between the wind stress curl maximum region and the Gulf Stream path is observed at multiple time-scales ranging from months to decades, spanning a distance of 1500 km between 70 and 55W. The wind stress curl in the positive vorticity pool is estimated to drive persistent upward vertical velocities ranging from 5 to 17 cm day−1 over its ~ 400,000 km2 area; this upwelling may supply a steady source of deep nutrients to the Slope Sea region, and can explain as much as a quarter of estimated primary productivity there. [ABSTRACT FROM AUTHOR]

September–November (e.g., autumn) 2023 produced the fewest western North Pacific (WNP) tropical cyclones (TCs) since 1951, likely as a joint response to El Niño and a warm phase of the North Pacific Mode (NPM). Decreases in both TC genesis frequency and two genesis potential indices (GPIs) over the western WNP were likely the result of El Niño-induced and warm NPM-induced negative low-level relative vorticity anomalies. Over the eastern WNP, TC genesis and GPI reductions were also associated with vorticity decreases over the eastern WNP, where the TC-suppressing effect of the warm NPM surpassed the TC-favoring effect of El Niño. The changes in vorticity were further linked to anomalous anticyclones centered over the South China Sea and the midlatitude central North Pacific. A linear combination of the responses to El Niño and a warm NPM can explain the changes in TC genesis and low-level circulation over most of the WNP in 2023, except east of 160°E where other climate modes may have played more of a role. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the nonexistence of the periodic peakon and peakon for a highly nonlinear shallow-water model, which has been recently derived from the full governing equations for two dimensional flow with the Coriolis effect or with constant vorticity, under a larger scaling than the Camassa-Holm (CH) one. Note that the so obtained model not only has CH-type terms, but also exhibits cubic order nonlinearities. Thus it is interesting to study how the higher power nonlinear terms affect the existence of the (periodic) peakon. [ABSTRACT FROM AUTHOR]

Multi-dimensional numerical simulations were performed to study the interactions between shock wave and premixed flame. The three-dimensional (3D) fully-compressible, reactive Navier–Stokes equations were solved using a high-order numerical method on a dynamically adapting mesh. The effect of wall friction on the shock–flame interaction was examined by varying wall boundary condition on sidewall. The simulations agree with previous experiment in terms of flame perturbation and flame evolution. The results show two effects of wall friction on flame–shock interaction: (1) flame stretching and (2) damping of local flame perturbation very close to the no-slip wall. The stretch effect leads to non-uniform development of the perturbated flame and consequently a significantly higher growth rate in both global flame perturbation and averaged pressure in the no-slip case compared to the free-slip case. By contrast, the damping effect locally moderates the flame perturbation in close proximity to the no-slip wall because less vorticity is deposited on this part of flame during shock–flame interaction. Quantitative analysis of vortex dynamics suggests that vorticity generation that is produced by baroclinic torque and enhanced by the dilation term during shock–flame interaction causes a growth of flame perturbation via Richtmyer–Meshkov instability. Nevertheless, the vorticity generation is greatly weakened in close proximity to the no-slip wall by the viscous torque and viscous dissipation terms due to friction. [ABSTRACT FROM AUTHOR]

In this paper, we establish new regularity criteria for the three-dimensional (3D) viscous incompressible magnetohydrodynamic (MHD) equations. It is proved that if the solution of the MHD equations satisfies u 3 ∈ L p (0 , T ; L q ( R 3 )) , j 3 ∈ L r (0 , T ; L s ( R 3 )) , 2 p + 3 q = 13 24 , 72 13 ≤ q ≤ ∞ ; 2 r + 3 s = 2 , 3 2 < s ≤ ∞ or u 3 ∈ L p (0 , T ; L q ( R 3 )) , w 3 ∈ L r (0 , T ; L s ( R 3 )) , 2 p + 3 q = 13 24 , 72 13 ≤ q ≤ ∞ ; 2 r + 3 s = 2 , 3 2 < s ≤ ∞ , then the regularity of the solution on (0, T), where u3, j3 and ω3 are the third component of velocity u, current density ∇ × b and vorticity ∇ × u, respectively. These results give new improvements of regularity theory of weak solutions. [ABSTRACT FROM AUTHOR]

This study introduces new insights into the climatology of South Atlantic (SAt) cyclones by employing a novel cyclone life cycle detection method, the CycloPhaser. Utilizing the minimum relative vorticity series and its derivative at the cyclone centre, the program effectively identifies distinct phases in the cyclone life cycle. Cyclone tracks are obtained through the analysis of relative vorticity at 850 hPa, using the ERA5 dataset. The study identified six main cyclone life cycle patterns from the analysis of 28,458 systems. The predominant cyclone type, accounting for approximately 60% of the analysed systems, exhibited a four‐phase configuration: incipient, intensification, mature and decay. Detailed statistics for each developmental phase and the overall life cycle are presented, offering valuable comparisons and new insights while corroborating previous research findings. Key genesis regions in the SAt are identified, along with track density maps that reveal distinct preferences in cyclone developmental cycle. The main outcome of this study is the demonstration that the automated classification procedure enables the analysis of cyclones' life cycles to be conducted promptly and with low computing costs, facilitating the comprehensive study of cyclone behaviour with high efficiency. [ABSTRACT FROM AUTHOR]

SLNE is the coupled model, that was developed in 2023. SL and NE here are the first two letters from SLAV (Semi-Lagrangian, based on Absolute Vorticity equation) model of the atmosphere and NEMO (Nucleus for European Modelling of the Ocean) ocean model that have been coupled using OASIS3-MCT software. The initial conditions for SLAV and NEMO are specified from an atmospheric and ocean analyses produced in Hydrometcentre of Russia. The 2010–2021 hindcast accuracy study shows, that SLNE has comparable errors to the operational SLAV model on a sub-seasonal time scale. The SLNE model has improved prediction skill of the 2010 heatwave features in comparison to SLAV, that is a motivation for further work to improve the coupled model. [ABSTRACT FROM AUTHOR]

The non-cavitating tip vortex in the near field of an elliptical hydrofoil is studied utilizing tomographic particle image velocimetry. Both the instantaneous and time-averaged flow fields are analyzed to elucidate the flow characteristics of the near-field tip vortex. The tip vortex is mainly formed on the suction side of hydrofoil and exhibits a tube-like shape. The turbulence intensity is at a relatively high level around the hydrofoil tip due to the roll-up process of the separated shear layers from the pressure side. With increasing angle of attack, the initiating position of the tip vortex moves upstream along the hydrofoil outline. In the near field, the axial flow within the tip vortex manifests a jet-like profile at higher angles of attack (α ≥ 10 °), and the majority of the vorticity is contained within the vortex core. A special position is identified during the streamwise evolution of the tip vortex, where the vortex circulation reaches its local maximum for the first time and the tip vortex cavitation is more prone to incept. In the vicinity of this crucial position, the pressure–velocity relation is derived along the vortex centerline by combining the three-dimensional measured velocity fields with the governing equations. It is revealed that the mean static pressure is directly related to the local mean axial velocity, adhering to the form of Bernoulli's equation. Conversely, corresponding pressure fluctuation depends on both the mean and fluctuating parts of the local axial velocity. [ABSTRACT FROM AUTHOR]

In the modified β -plane approximation, we derive exact solutions to the nonlinear governing equations of three-dimensional trapped lee waves influenced by Coriolis forces or Coriolis forces and centripetal forces, respectively. Further, we obtain the dispersion relation and qualitatively analyze the pressure, density, and vorticity in two cases. In this process, we find more accurate representations of solutions caused by the incorporation of a gravitational-correction term and investigate the influence of centripetal forces on trapped lee waves. [ABSTRACT FROM AUTHOR]

In order to ascertain the combined effect of diameter ratio (d/D) and spacing ratio (L/D) on the flow around two tandem circular cylinders, a total of 43 research cases are numerically simulated using a large eddy simulation model in this study, including d/D = 0.2 (L/D = 0.80–6.00), d/D = 0.4 (L/D = 0.80–6.00), and d/D = 0.6 (L/D = 0.90–6.00) at Re = 3900. By systematically analyzing the instantaneous/time-averaged spanwise vorticity contours, the three-dimensional time-averaged Q-criterion iso-surfaces, the spanwise periodicity within the gap, and the Strouhal number (St), eight sub-flow regimes can be identified, namely, non-periodic reattachment-(1), small-scale periodic reattachment, large-scale periodic reattachment, non-periodic reattachment-(2), bi-stable flow, intermittent lock-in co-shedding, subharmonic lock-in co-shedding and no lock-in co-shedding. The occurrence of these sub-flow regimes depends on the combination of d/D and L/D. Besides, with regard to the larger downstream cylinder (DC), there are three possible dominant St values for the DC instantaneous drag coefficient (i.e. StCD-D1, StCD-D2, and StCD-D3). It is quite clear that StCD-D1 has almost the same value as StCL-D1, StCD-D2 is roughly equal to 2StCL-D1, and StCD-D3 is approximately the summation of StCL-D1 and StCL-D2, where StCL-D1 and StCL-D2 denote the primary and secondary dominant St values of the DC instantaneous lift coefficient, respectively. Additionally, various flow statistical parameters are obtained and compared for different combinations of d/D and L/D, such as the velocity, vorticity, St value, spanwise periodicity, force coefficient, base pressure coefficient, reattachment angle, and separation angle. [ABSTRACT FROM AUTHOR]

The canonical shock/isotropic turbulence interaction (SITI) at high shock Mach numbers (Ms) is studied by conducting direct numerical simulation (DNS) for thermally perfect gas (TPG) and calorically perfect gas (CPG). Combining DNS with linear interaction analysis (LIA), the amplification of vorticity variance across the shock wave is studied. It is found that the changes in vortical velocity fluctuation amplitude and turbulent length scales under vibrational excitation have a competitive effect on vorticity amplification. The latter is dominant and leads to the transverse vorticity amplification increasing by 32.2% at Ms = 6.0. Based on the LIA theory, a vorticity amplification model for SITI considering vibrational excitation is established. Furthermore, the impact of vibrational excitation on the downstream vorticity transportation is examined through an analysis of the transport equation. The vibrational excitation strengthens both the vortex stretching and viscous dissipation of streamwise vorticity but only alters the viscous dissipation of transverse vorticity. Then, the vorticity transportations of different turbulent structures for CPG and TPG are compared. The comparison indicates that the increment of vortex stretching for streamwise vorticity variance is sustained by the enhanced turbulent structures corresponding to the stable-node/saddle/saddle, and the rapid decay of transverse vorticity variance for TPG is associated with the enhanced viscous dissipation of the nonfocal turbulent structure. [ABSTRACT FROM AUTHOR]

Film cooling is widely adopted in the thermal protection of modern aerospace engines. The optimization of the film hole is an important issue in thermal designs. In this work, a density-based topology optimization is conducted to obtain a high-performance film cooling hole geometry. Unlike the traditional wall-temperature-based optimization objectives, a novel objective function based on the Q-criteria is proposed by taking the vorticity dynamics and flow mixing into account. Finally, a unique high-performance film hole is obtained, which shows superior performance compared to the standard cylindrical hole, particularly at high blowing ratios. The film cooling effectiveness can be elevated by 51 folds in the case of a high blowing ratio (M = 1.5). Analyses of the vortices and velocity fields suggest that the presence of the additional secondary vortex pair enhances the attachment of cooling air to the wall. [ABSTRACT FROM AUTHOR]

Mechanisms that ultimately lead to the enhanced wall shear stress toward the end of transition to turbulence in a zero-pressure gradient boundary layer are examined for two different transition routes using direct numerical simulations. This paper examines, using a vorticity point of view, late-stage transition mechanisms in roughness induced transition produced by distributed roughness, and a classical transition caused by a large amplitude Tollmien–Schlichting (TS) wave interacting with free stream disturbances adding to the recent insights on discrete roughness induced transition [Suryanarayanan et al., "Roughness induced transition: A vorticity point of view," Phys. Fluids 31(2), 024101 (2019)]. The Reynolds stress is written in terms of vorticity fluxes, and large negative values of the vorticity flux term associated with the correlation of the spanwise velocity and wall-normal vorticity, w ′ ω y ′ ¯ , are observed in the late-stage transition in all cases. A decrease in wall shear stress is observed when near-wall spanwise motion is suppressed, whereas suppression of spanwise motion far away from the wall does not immediately alter wall shear stress; this observation further supports the finding that w ′ ω y ′ ¯ is the dominant term that increases wall shear stress during transition. w ′ ω y ′ ¯ is demonstrated to be correlated with streamwise vorticity near the wall, and this mechanism is illustrated by studying the evolution of a streamwise vortex in a Couette flow. [ABSTRACT FROM AUTHOR]

In this study, we consider the connection of the hydrodynamic force with vortex shedding behind a stationary sphere in an unbounded fluid at several Reynolds numbers, covering the range of critical transition from plane-symmetric to non-symmetric flow. A principal spectrum analysis (PSA) is employed/proposed to obtain the spectral representation (SR) modes for each time-varying force coefficient; this enables us to identify (i) one single characteristic frequency at R e = 300 , 350, and 380, i.e., the fast frequency f V S which represents the frequency of vortex shedding and (ii) two characteristic frequencies at R e = 390 , 400, and 420: one is the first fast frequency f 1 = f V S , representing the frequency of vortex shedding, and the other is the second fast frequency f 2 , representing the frequency of side oscillations of the vortex flow in the transverse flow direction. In the situations of the latter set of Reynolds numbers, the SR modes indicate that not only the strength but also the phase of shed vortex varies slightly at each successive vortex shedding, and most notably, we have identified rotation of the vorticity pattern in the near wake about the central axis. The PSA-SR mode analysis reveals that these three vortex activities all co-operate at the integer multiples of the greatest common-divisor of the two characteristic frequencies ( f 1 , f 2 ). In other words, the intricate subtlety of vortex shedding behind a stationary sphere can well be uncovered through the PSA-SR mode analysis for establishing the close connections between the force coefficients and the vorticity activities behind the sphere. The present work represents a sequel to our previous study: A spectral force representation and its physical implication for vortex shedding past a stationary or an oscillating circular cylinder at low Reynolds numbers [Lu et al., "A spectral force representation and its physical implication for vortex shedding past a stationary or an oscillating circular cylinder at low Reynolds number," Phys. Fluids 35(5), 053606 (2023)], where we initially proposed the PSA-SR analysis to establish the connections between the force coefficients and the vortex shedding of the circular cylinder under pre-, sub-, and normal synchronization. [ABSTRACT FROM AUTHOR]

This study employs numerical simulation to investigate the transient flow and cavitation performance of centrifugal pumps with rough impellers, validating the numerical method with experimental data. Initially, the effect of blade roughness on the external characteristics of centrifugal pumps is examined. Subsequently, the study specifically addresses the impact of roughness on internal flow characteristics during cavitation, including vapor volume distribution, three-dimensional vortex structures, and vorticity distribution in the impeller channel. Furthermore, the influence of blade roughness on local energy loss is analyzed using entropy production theory. Finally, several monitoring points are arranged in the impeller channel to assess pressure pulsation effects. The results show that blade roughness generally reduces the head and efficiency of centrifugal pumps. During the non-cavitation and cavitation incipient stages, roughness marginally increases the head, with a maximum increase in only 0.1%. Impeller roughness causes vacuole collapse and vortex structure enlargement, disrupting the stable flow path within the channel. Blade roughness also escalates energy loss within impeller components, particularly under full cavitation conditions, where the impeller's entropy production accounts for up to 50%. Pressure pulsation results reveal that while blade roughness can slightly suppress cavitation, it also disturbs the flow field pressure. These insights provide guidance and data support for mitigating roughness and cavitation, the two primary instability factors in centrifugal pump operations. [ABSTRACT FROM AUTHOR]

A discontinuous cavitation model (DCM) containing the effects of ambient overpressure, incondensable gas, inertia, viscosity, surface tension, characteristic nuclei size, and characteristic surface speed of cavitation nuclei was proposed based on two approximate local first integrals of the Rayleigh–Plesset equation. Discontinuities caused by sudden cavitation bursting, heterogeneous nuclei distribution, and bubble-induced turbulence can, thus, be roughly represented. It was employed in simulating kinds of cavitation flows. It presented more physical reasonability than the Singhal model (SM) in capturing the vigorous vaporization in the water pool under strong negative ambient pressure. As for hydrodynamic cavitation around the National Advisory Committee for Aeronautics hydrofoil NACA0015, not only large-scale features were obtained as well as the SM, but also, some small-scale structures in the cavitation cloud were presented. For instance, isolated bubbles and their dynamic behaviors, such as inception and collapse, expansion and shrinkage, and breakup and coalescence, were captured. Extra turbulence pulsation, which is correlated with the temporal–spatial distribution of vapor concentration, can also be observed in the cavitation cloud. Moreover, different from the vorticity field obtained by the SM, the surface of the cavitation cloud obtained by the DCM becomes a thick vortex sheet. Moreover, another simulation case with a cavitation number of 0.32 further confirmed its adaptivity in supercavitation flows. Furthermore, by adjusting the parameters (i.e., the fluid density in the phase change layer near the cavitation nucleus) in the DCM, oscillations and waves excited by fierce phase change can be observed in cavitation clouds. [ABSTRACT FROM AUTHOR]

Considering that marine structures are frequently subjected to the combined effects of waves and currents, the wave–current coupling environment largely determines the structural load and the surrounding water–air mixed flow, which is a typical feature of offshore structures, such as ships and offshore platforms. This study focuses on the interaction between a horizontal cylinder and a free surface in a wave–current nonlinear coupled environment using numerical simulations. The numerical method is based on the incompressible Navier–Stokes equation, with the volume-of-fluid method used to capture the free surface. Based on the second-order Stokes wave theory, we studied the impact of wave height and steepness on the cylinder force, vorticity field, free-surface deformation, and spatial–temporal distribution characteristics of entrainment bubbles. The results showed that the wave height and wave steepness have opposite effects on the root mean square (RMS) value of the force and influence the amplitude and period of the force curve. The stretching of the negative vortex led to varying degrees of double-frequency oscillation modes in the force curves. The main sources of bubbles in the wake are the breaking of the free surface and the entrainment caused by the cylinder vortex, and the bubbles caused by the former account for the majority. Compared with the wave height, an increase in wave steepness can cause a more severe interface breaking, resulting in more entrainment bubbles. [ABSTRACT FROM AUTHOR]

An A/B/C-type gas cylinder with various concentrations of SF6 (ranging from 5% to 80% in volume fraction) in the inner cylinder is constructed to investigate the dependence of the interface evolution on the Atwood number. For negative Atwood numbers, secondary vortex pairs emerge at the downstream interface of the outer cylinder following the interaction of a high-pressure triple point with the downstream interface, while a downstream jet is formed due to the generation of a notably higher-pressure zone after the transmitted shock wave traverses the convergence point. The widths and heights of both outer and inner cylinders are analyzed to quantify the interface evolution. The mechanism behind the vorticity evolution is investigated using the vorticity transport equation. The vorticity equation is introduced to investigate the mechanism of vorticity evolution. The dilatation and baroclinic terms play a dominant role in the dynamics of vorticity production. The net circulation can be predicted by linearly summing existing circulation models. Analysis of the area and mean mass fraction histories of the outer and inner cylinders shows that more ambient gas dilutes SF6 and promotes gas mixing as the Atwood number decreases. [ABSTRACT FROM AUTHOR]

In the internal parts of the Zagros collision zone, several deformation phases have been superimposed. The early deformation phase caused the development of a penetrative foliation. The late‐stage deformation phase was preferentially accommodated within shear zones and caused the generation of shear bands, implying a non‐coaxial component of deformation, the end of this stage deformation was marked by the development of kink‐bands. In the vicinity of Zagros suture zone, the kink angle increased from 40° to 60°, and the kink‐bands was converted to chevron folds. In this region, the external (α) and internal (β) angular ratio is α/β ≠ 1 and kink angle increased, and deformation occurred with 10% to 30% volume loss. Farther from the suture zone in the east, α/β = 1; and total volume was constant or increased by 5% to 10%. Kink‐bands kinematic analysis in the study area revealed this structures were sensitive to deformation conditions and components such that, with decreasing distance to the Zagros suture zone, shearing and rotation increased, a high kinematic vorticity dominated, and volume loss occurred during deformation. [ABSTRACT FROM AUTHOR]

As one kind of submesoscale instabilities, symmetric instability (SI) with spatiotemporal scales of O (100) m–O (1) km and O (1) hour exerts significant effects on vertical material transports and forward energy cascade in the ocean. The potential vorticity (PV) is an important conservative parameter controlling quasi‐geostrophic flows, whose budget can be modulated by SI. However, due to the small spatial scale of SI which is hardly resolved by most current observations and regional models, how SI affects the PV budget and how big the effect is remain unclear. In this work, the effect of SI on the PV budget in the surface mixed layer (SML) of the Kuroshio Extension region is quantitatively analyzed based on high‐resolution simulations by applying an existing SI parameterization scheme. Compared with the case without SI effects, negative PV is found to be eliminated in the SML in the SI‐parameterized case. The negative‐PV likelihood in the SI‐parameterized case is decreased by up to 12% due to SI. Analysis of the PV budget indicates that SI contributes to the PV budget mainly by modulating the friction term. The friction term tends to generate negative PV but its magnitude is decreased by 35% due to SI. Apart from the frictional term, both advection and non‐adiabatic terms are also found to be modulated by SI. This work sheds light on the contribution of SI in the PV budget in the ocean mixed layer and suggests a significant role of SI in quasi‐geostrophic PV dynamics. Plain Language Summary: Potential vorticity (PV) is a conservative but dynamically active tracer and an important indicator to characterize instability in the ocean. Traditionally, PV is applied to quasi‐geophysical dynamics, such as large‐scale circulation (O (1,000) km) and mesoscale currents (O (100) km). As the link between meso‐ and micro‐scales, submesoscale symmetric instability with spatial scales of O (100) m–O (1) km contribute to the PV budget, potentially modulating the quasi‐geostrophic dynamics. This work quantitatively evaluates the effect of SI on the PV budget by applying a parameterization scheme. Key Points: The effect of symmetric instability (SI) on potential vorticity is evaluated by applying a parameterization schemeElimination of negative potential vorticities is mainly caused by the friction effect with magnitude decreased by 35%The advection and non‐adiabatic effect are also found to be modulated by SI [ABSTRACT FROM AUTHOR]

In order to obtain a more detailed and comprehensive relationship between the cavitation phenomenon and energy loss, this paper takes an NACA66 hydrofoil as an example to analyze the specific relationship between the cavitation flow field and energy dissipation by using entropy production theory, a ZGB cavitation model, and k-ε turbulence model which were modified by a Filter-Based Density Correction model (FBDCM). The results show that the modified k-ε model can effectively capture the morphology of cavity evolution in the cavitation flow field. The vortex dilatation term contributes the most to the vorticity transport in cavitation flow. The energy loss of the cavitation flow field is primarily composed of turbulent dissipation, which is primarily distributed in the area below the lifted attached cavity and inside the vortex induced by the cloud cavity. The direct dissipation entropy production is predominantly distributed in the area near the stagnation point of the hydrofoil's leading edge and inside the cavity. The wall entropy production is chiefly distributed in the area where the cavity is not covered. The cavitation entropy production mainly occurs on the vapor–liquid interface, and the value is negative, indicating that the vapor–liquid conversion in the cavitation process needs to absorb energy from the flow field. [ABSTRACT FROM AUTHOR]

The solar wind‐magnetosphere‐ionosphere interaction at Jupiter is reproduced numerically adopting the nine‐component magnetohydrodynamic simulation. Calculations take into account the magnetosphere‐ionosphere coupling, Jovian rotation, and Io plasma source. High‐speed rotating plasma inside restricted magnetospheric space causes expansion and contraction of magnetic field, forming super‐rotation at radial distance 20∼30 Rj and co‐rotation breakdown further outside. Field‐perpendicular current that restores co‐rotational delay beyond 30 Rj is connected via field‐aligned current to the main oval in the ionosphere. Inside 20 Rj, there is almost co‐rotation region (deviation from co‐rotation less than 20 km/s). Particularly within 10 Rj, the deviation from co‐rotation is less than 2 km/s. In the nearly co‐rotating region, the Io plasma forms a disk structure through field‐aligned redistribution. The interchange instability occurs near the outer wall of the Io plasma disk, and instability flow develops to vortex. Through this instability, a part of the centrifugal drift current supporting the Io plasma disk is connected to low‐latitude field‐aligned current that generates beads‐like spots on the lower latitude side of the main oval. Resulting interchange instability comes to satisfy the structure of convection and enables further development of vortex. The Coriolis force acting on eastward flow inside the developing vortex makes this flow protrude further outward, forming eastward bending fingers. Inside 10 Rj, Io plasma transport by the interchange instability becomes slower, despite the center of the disk. Io plasma escapes from the inner magnetosphere with a time constant of 20 days if this slow transport is taken into account. Key Points: We numerically reproduce the Jovian solar wind‐magnetosphere‐ionosphere interaction, considering planetary rotation and Io sourceOutward diffusion of Io plasma is facilitated by the interchange instability that occurs as vortex motion obeying the M‐I couplingFingers that develop in the Io plasma disk extend eastward in the region where the Coriolis force acts to accelerate the instability [ABSTRACT FROM AUTHOR]

An oscillating flow past a structure represents a complex, high-dimensional, and nonlinear flow phenomenon, which can lead to the failure of structures due to material fatigue or constraint relaxation. In order to better understand flow-induced vibration (FIV) and coupled flow fields, a numerical simulation of a two-degrees-of-freedom FIV in a cylinder was conducted. Based on the Lagrangian-based dynamic mode decomposition (L-DMD) method, the vorticity field and motion characteristics of a cylinder were decomposed, reconstructed, and predicted. A comparison was made to the traditional Eulerian-based dynamic mode decomposition (E-DMD) method. The research results show that the first-order mode in the stable phase represents the mean flow field, showcasing the slander tail vortex structure during the vortex-shedding period and the average displacement in the in-line direction. The second mode predominantly captures the crossflow displacement, with a frequency of approximately 0.43 Hz, closely matching the corresponding frequency observed in the CFD results. The higher dominant modes mainly capture outward-spreading, smaller-scale vortex structures with detail displacement characteristics. The motion of the cylinder in the in-line direction was accompanied by symmetric vortex structures, while the motion of the cylinder in the crossflow direction was associated with anti-symmetric vortex structures. Additionally, crossflow displacement will cause a symmetrical vortex structure that spreads laterally along the axis behind the cylinder. Finally, when compared with E-DMD, the L-DMD method demonstrates a notable advantage in analyzing the nonlinear characteristics of FIV. [ABSTRACT FROM AUTHOR]

We consider the stability of the global weak solution of the Quantum Euler system in two space dimensions. More precisely, we establish compactness properties of global finite energy weak solution for large initial data provided that these are axisymmetric. The main novelty is that the initial velocity is not necessary irrotational when the density is not vanishing, our main argument is based on the Madelung transform which enables us to prove new Kato estimates on the irrotational part of the velocity. [ABSTRACT FROM AUTHOR]

Distinctive synoptic‐scale (∼1,500 km) flow features are identified within the core of the stratospheric polar‐night vortex at stratopause altitudes (∼50 km). Typically they comprise a train or a complex pattern of transient vortices, each characterized by enhanced values of potential vorticity (PV) and relative vorticity but with a weaker thermal signal. In the MERRA‐2 (and two other) reanalysis fields these cyclone‐like features persist for several days, occur episodically, and form essentially within the core of the polar‐night vortex itself. Their origin is plausibly linked to a form of barotropic instability associated with a radiatively‐induced annular ring of enhanced PV. Moreover, their ubiquity and dynamics carries possible implications for: ‐ the structure of the larger‐scale polar vortex and its preconditioning ahead of a Sudden Stratospheric Warming event; the distribution of trace‐constituents within the core; and the features representation in extended range/seasonal prediction and climate models. Plain Language Summary: In wintertime the earth's stratospheric polar vortex extends from a height of around 15 km to well above 50 km and equatorward to around 30° from the pole. At its edge, winds can be significantly in excess of 100 m s−1 whilst the vortex's core has been viewed as an enclosed containment vessel partially insulated from exterior influences. In contrast it is shown that, within the core, spatially rich patterns of synoptic‐scale (∼1,500 km) cyclone‐like features occur at stratopause altitudes (∼50 km). Their scale and structure indicates that their origin is linked to the large latitudinal temperature gradient that can develop across the polar‐night twilight zone. Their ubiquity suggests that they:‐ could contribute to the well‐mixed distribution of chemical constituents within the vortex's core; influence the overall structure of the polar vortex itself; impact upon the breakdown of the vortex during events of Sudden Stratospheric Warming; and need to be adequately represented in seasonal prediction and climate models. Key Points: Distinctive synoptic‐scale cyclone‐like features are identified within the core of the polar‐night vortex at stratopause altitudesAn account is given of their space‐time character and dynamics, and evidence adduced of their presence in three Reanalysis schemesTheir existence carries possible ramifications for seasonal and climate models and for the structure of the polar vortex itself [ABSTRACT FROM AUTHOR]

We construct in this article the semi-analytic Physics Informed Neural Networks (PINNs), called singular layer PINNs (or sl-PINNs), that are suitable to predict the stiff solutions of plane-parallel flows at a small viscosity. Recalling the boundary layer analysis, we first find the corrector for the problem which describes the singular behavior of the viscous flow inside boundary layers. Then, using the components of the corrector and its curl, we build our new sl-PINN predictions for the velocity and the vorticity by either embedding the explicit expression of the corrector (or its curl) in the structure of PINNs or by training the implicit parts of the corrector (or its curl) together with the PINN predictions. Numerical experiments confirm that our new sl-PINNs produce stable and accurate predicted solutions for the plane-parallel flows at a small viscosity. [ABSTRACT FROM AUTHOR]

The Sonid Zuoqi ductile detachment zone is located at the southeastern margin of the Central Asian orogenic belt (CAOB), striking EW and dipping to the S. The major rock type of the Sonid Zuoqi ductile detachment zone is mylonite derived from granite. The sequence of mylonite features is: (1) S and C foliations of mylonite, and (2) extensional crenulation cleavage (ecc) or C and the kinematic vorticity (Wk) value changed from 0.70 to 0.95 and from 0.37 to 0.69, respectively; the strain type of the mylonites within the Sonid Zuoqi ductile detachment zone is compressional to planar strain. The strong deformation mylonite and Halatu plutons yielded a zircon U‐Pb age of 244 Ma and a zircon (U‐Th)/He age of 214 Ma, respectively. Based on the strain and kinematic vorticity analysis, together with the zircon U‐Pb and zircon (U‐Th)/He ages and the regional tectonic background, the study area experienced three stage evolution: tangential simple‐shear (244 Ma), simple‐shear‐dominated general shear represented by upper crustal extension (224 Ma) and pure–shear–dominated general shear represented by the Halatu pluton doming (214 Ma), which constrained the early Mesozoic NE–SW crustal extension at the southeastern margin of the CAOB. This NE–SW extension probably originated from the post‐orogenic extensional collapse of the CAOB, subsequent exhumation being controlled by the far afield effects of the closure of the Mongol–Okhotsk belt. [ABSTRACT FROM AUTHOR]

In this paper, we present a numerical investigation into the influence of electric and magnetic fields on the dynamics of a suspended liquid film that carries an electric current. A nonuniform magnetic field is considered utilizing a disk-shaped magnet located above the two-dimensional fluid. Electric and magnetic forces exerted on the fluid induce a new dynamical features. We perform a numerical study of the dynamics of such two-dimensional fluid system commonly named Liquid Film Motor. The presence of the nonuniform external magnetic field causes changes in the fluid’s behavior. Specifically, the previously symmetric vortex becomes asymmetric under the influence of the magnetic field. In this dynamic behavior, as the external magnetic field increases, the center of the vortex shifts in a direction perpendicular to the electric current passing through the fluid film. The unique combination of electric and magnetic field allows to manipulate the motion of the vortex without resorting to traditional mechanical methods. This finding implies that the motion of the vortex can be directed and controlled by adjusting the strength of the external magnetic field, without the need for direct contact with the fluid or mechanical tools. [ABSTRACT FROM AUTHOR]

Let M be an oriented three-dimensional Riemannian manifold. We define a notion of vorticity of local sections of the bundle SO ⁢ (M) → M of all its positively oriented orthonormal tangent frames. When M is a space form, we relate the concept to a suitable invariant split pseudo-Riemannian metric on Iso o ⁢ (M) ≅ SO ⁢ (M) : A local section has positive vorticity if and only if it determines a space-like submanifold. In the Euclidean case we find explicit homologically volume maximizing sections using a split special Lagrangian calibration. We introduce the concept of optimal frame vorticity and give an optimal screwed global section for the three-sphere. We prove that it is also homologically volume maximizing (now using a common one-point split calibration). Besides, we show that no optimal section can exist in the Euclidean and hyperbolic cases. [ABSTRACT FROM AUTHOR]

Tropical cyclone (TC) genesis prediction remains a major operational challenge. Using multiple satellite datasets and a state-of-the-art reanalysis dataset, this study identifies developing and non-developing tropical disturbances over the western North Pacific from June to November of 2000–2019 and conducts composite analyses of their water vapor budget components and relevant dynamic–thermodynamic parameters in the Lagrangian framework following three-day disturbance tracks. Both groups of disturbances have a similar initial 850 hPa synoptic-scale relative vorticity, while the water vapor budget of developing disturbances exhibits distinct stage-wise evolution characteristics from non-developing cases. Three days prior to TC genesis, developing cases are already associated with significantly higher total precipitable water (TPW), vertically integrated moisture flux convergence (VIMFC), and precipitation, of which TPW is the most important parameter to differentiate two groups of disturbances. One day later, all the water vapor budget components (i.e., TPW, VIMFC, precipitation, and evaporation) strengthened, linked with the enhancement of the mid-to lower-tropospheric vortices. A negative radial gradient of evaporation occurs, suggesting the beginning of the wind−evaporation feedback. On the day prior to TC genesis, the water vapor budget components, as well as the mid-to lower-tropospheric vortices, continue to intensify, eventually leading to TC genesis. By contrast, non-developing disturbances are associated with a drier environment and weaker VIMFC, precipitation, and evaporation during the three-day evolution. All these factors are not favorable for the intensification of the mid-to lower-tropospheric vortices; thus, the disturbances fail to upgrade to TCs. The results may shed light on TC genesis prediction. [ABSTRACT FROM AUTHOR]

The author has presented results of numerical modeling of the influence of the angle of attack of a thin width-limited plate with a short chord on the velocity field of the internal region of a turbulent boundary layer (TBL) and skin friction. The computations were performed by the large eddy simulation (LES) method at the Reynolds number Reθ = 540 calculated from the velocity on the channel axis and the momentum thickness. Changes in the average and pulsation characteristics of the three-dimensional velocity field under the impact of the wake of the plate and of tip vortices as functions of the angle of attack of the plate in the range ±1° have been analyzed. It has been shown that a determining influence on the formation of the velocity field is exerted by the tip vortices whose vorticity is opposite with the positive and negative angles of attack. The mean value of the skin-friction coefficient decreases by 6% at the positive angle of attack and by 14% at the negative angle with respect to the value of this coefficient in an unperturbed TBL. [ABSTRACT FROM AUTHOR]

Rotation/spin of plasma blob in the edge and SOL regions in the presence of interchange plasma turbulence with a finite ion temperature gradient ( $ \nabla _\perp T_i $ ∇ ⊥ T i ) has been presented. $ \nabla _\perp T_i $ ∇ ⊥ T i destabilizes plasma, but damps the eddies related to the plasma blob by enhanced viscosity, therefore, rotation is important for plasma dynamics as the rotation further stabilizes the blobs. The turbulence has been simulated numerically and results show monopolar vorticity is responsible for blob rotation, but the physics is different in the edge and SOL regions. A radial profile of vorticity, and angular speed of a typical plasma blob have been presented. The role of $ \nabla _\perp T_i $ ∇ ⊥ T i has been identified. [ABSTRACT FROM AUTHOR]

In this paper, we review a recently offered notion of quasi-static evolution of the axial self-gravitating structures at large scales and the criterium to characterize the corresponding evolutionary aspects under the influence of strong curvature regimes. In doing so, we examine the axial source's dynamic and quasi-static behavior within the parameters of various modified gravity theories. We address the formalism of these notions and their possible implications in studying the dissipative and anisotropic configuration. We initiate by considering higher-order curvature gravity. The Palatini formalism of f (R) gravity is also taken into consideration to analyze the behavior of the kinematical as well as the dynamical variables of the proposed problem. The set of invariant velocities is defined to comprehend the concept of quasi-static approximation that enhances the stability of the system in contrast to the dynamic mode. It is identified that vorticity and distinct versions of the structure scalars Y I , Y II and Y KL play an important role in revealing the significant effects of a fluid's anisotropy. As another example of evolution, we check the influence of Palatini-based factors on the shearing motion of the object. A comparison-based study of the physical nature of distinct curvature factors on the propagation of the axial source is exhibited. This provides the intriguing platform to grasp the notion of quasi-static evolution together with the distinct curvature factors at current time scenario. The importance of slowly evolving axially symmetric regimes will be addressed through the distinct modified gravitational context. Finally, we share a list of queries that, we believe, deserve to be addressed in the near future. [ABSTRACT FROM AUTHOR]

The scale-dependent predictability of the devastating 7·20 extreme rainstorm in Zhengzhou, China in 2021 was investigated via ensemble experiments, which were perturbed on different scales using the stochastic kinetic-energy backscatter (SKEB) scheme in the WRF model, with the innermost domain having a 3-km grid spacing. The daily rainfall (RAIN24h) and the cloudburst during 1600–1700 LST (RAIN1h) were considered. Results demonstrated that with larger perturbation scales, the ensemble spread for the rainfall maximum widens and rainfall forecasts become closer to the observations. In ensembles with mesoscale or convective-scale perturbations, RAIN1h loses predictability at scales smaller than 20 km and RAIN24h is predictable for all scales. Whereas in ensembles with synoptic-scale perturbations, the largest scale of predictability loss extends to 60 km for both RAIN1h and RAIN24h. Moreover, the average positional error in forecasting the heaviest rainfall for RAIN24h (RAIN1h) was 400 km (50–60) km. The southerly low-level jet near Zhengzhou was assumed to be directly responsible for the forecast uncertainty of RAIN1h. The rapid intensification in low-level cyclonic vorticity, mid-level divergence, and upward motion concomitant with the jet dynamically facilitated the cloudburst. Further analysis of the divergent, rotational and vertical kinetic spectra and the corresponding error spectra showed that the error kinetic energy at smaller scales grows faster than that at larger scales and saturates more quickly in all experiments. Larger-scale perturbations not only boost larger-scale error growth but are also conducive to error growth at all scales through a downscale cascade, which indicates that improving the accuracy of larger-scale flow forecast may discernibly contributes to the forecast of cloudburst intensity and position. [ABSTRACT FROM AUTHOR]

Tropical cyclones are known to expand to an equilibrium size on the f plane, but the expansion process is not understood. In this study, an analytical model for tropical cyclone outer-size expansion on the f plane is proposed. Conceptually, the storm expands because the imbalance between latent heating and radiative cooling drives a lateral inflow that imports absolute vorticity. Volume-integrated latent heating increases more slowly with size than radiative cooling, and hence, the storm expands toward an equilibrium size. The predicted expansion rate is given by the ratio of the difference in size from its equilibrium value rt,eq to an environmentally determined time scale τrt of 10–15 days. The model is fully predictive if given a constant rt,eq, which can also be estimated environmentally. The model successfully captures the first-order size evolution across a range of numerical simulation experiments in which the potential intensity and f are varied. The model predictions of the dependencies of lateral inflow velocity and expansion rate on latent heating rate are also compared well with numerical simulations. This model provides a useful foundation for understanding storm size dynamics in nature. [ABSTRACT FROM AUTHOR]