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In this article, I suggest that our current relation to the sociopolitical future is one where we are blocked from changing our view of what that future is or could be. In this sense, we are trapped in a time loop wherein the challenges before us are continuously met with social and political solutions designed for futures past, old futures. These past possible futures are ones that failed to solve the problems they were offered to address. As such, there is no growth, change, or redemption that could activate a new future; there is only the rehearsal of the old ones: failed futures from the past. What's more, this process of defuturing also relies on a winnowing of the past such that only those pasts that align with our present are allowed to be brought forward. I argue that, to reactivate our future, we also need to reactivate our pasts. I am thinking of those pasts that we do not seek or do not want but that nevertheless come to us. These are the multiple and competing pasts that swirl with present and future as in a vortex, denying any one past the privilege of guiding, directing, or foreclosing the future. It is only by facing this vortex and reopening the past that we can re‐open the future and escape the time loop of our ever‐receding horizon. [ABSTRACT FROM AUTHOR]

In this article, we study the vortex formation in spin-1 spin--orbit coupling rotating Bose--Einstein condensates. Numerical results are obtained by solving the spinor Gross--Pitaevskii equation. We mainly focus on the influences of external magnetic fields on vortex structures and dynamics properties. With the increase in magnetic field strength, the populations of magnetic components j = ±1 reach the identical value. For the density profile, the three components present identical density structures, and the size of condensates is nearly the same. In addition, some related physical quantities, such as the time taken for the arrival of a steady population and root-mean-square size, kinetic energy, and total angular momentum, are calculated. The results show that these quantities decrease as the magnetic field strength increases. Moreover, we also investigate the time evolution of angular momentum. It is seen that the dynamic behavior of the magnetic components j = ±1 is exactly consistent, and the total angular momentum reduces in the presence of the strong magnetic field. This reflects the fact that the introduction of the strong magnetic field makes it difficult to rotate the condensate, and thus, it is disadvantageous for generating more vortices. [ABSTRACT FROM AUTHOR]

The operation of marine vessels with high efficiency provides a great contribution within the scope of the International Maritime Organization and the sustainable development goals. In terms of the propulsion system, selecting the appropriate propeller is critical to effectively use the engine power installed in marine vessels because the biggest energy losses during transmission occur on the propeller and ship hull. Increasing propeller efficiencies above a certain level is quite a challenge by simply changing the number of blades, pitch, or propeller type. Therefore, various energy-saving device applications, such as propeller boss cap fins (PBCFs), are performed on the ship propeller. The effects of National Advisory Committee for Aeronautics 4415 profile PBCFs which have a different position and pitch angle integrated into the E698 model propeller have been investigated to describe efficiency, vortex, and pressure distributions based on the KRISO very large crude carrier 2 designed hull in this study. The E698 model propeller has been created by the 3D software and the validation has been performed by the computational fluid dynamic solver software based on the reference values of the propeller. The effect of four PBCF applications which have different pitches and positions on the model propeller has been revealed in terms of the efficiency, pressure distributions, and vortexes. Although P45-R45 and P45-R90 PBCF applications are quite close to the E698 propeller in terms of efficiency, no significant efficiency increase has been observed. In addition, the efficiency has decreased considerably in P90-R45 and P90-R90 applications. PBCFs application with P45-R90 has provided superiority to the base model in terms of pressure distributions and vortex formation. However, any improvement has not been achieved in the remaining three designs. Therefore, PBCF applications should be applied quite elaborately based on propeller types. [ABSTRACT FROM AUTHOR]

Optical elements based on nanomaterials are becoming major avenues to satisfy the technological requirements of compact, lightweight, and tunable elements of the emerging terahertz (THz) field. A new generation of diffractive components integrating specific geometry with additional features (flexibility, stretchability, rotation, and other approaches for tuning properties) extends the functionality of wavefront control. Here, an innovative approach is demonstrated to control the THz wavefront via a layered composition of spiral zone plates (SZPs) with tunable mutual orientation and scaling. As a proof of concept, the SZP is designed using Laguerre‐Gauss mode analysis with further fabrication and experimental characterization of the resultant vortex beams. For each single SZP, a flexible element is proposed based on a thin film of single‐walled carbon nanotubes deposited on a stretchable substrate. Thus, this diffraction element can be tuned not only by rotation (along the azimuthal direction), but also by its stretching (in the radial direction). The spatial tuning of the developed SZPs (spiral zone plates) opens up an efficient, convenient, and highly customizable approach for the manipulation of vortex beams. [ABSTRACT FROM AUTHOR]

Facing an increasingly hostile ecological environment, the imperative for advancing hydrogen fuel cell vehicles has become more pronounced. This paper establishes a three-dimensional computational fluid dynamics model of a Roots-type hydrogen circulating pump by utilizing the generalized type line equation of the Roots rotor. Delving deep into the intricate interplay of backflow phenomena on the internal flow dynamics and operational efficiency of the Roots-type hydrogen circulation pump across various scenarios. The results reveal that mass flow rate and velocity vary continuously and with the same pulsation frequency as rotation angle or time during a complete rotation cycle. As the rotational speed increases, the number of backflow occurrences decreases, the frequency of backflow currents in the rotor basin decreases, and the temperature rise in both the suction and exhaust chambers decreases. It becomes evident that the rotational speed wields a more profound influence on the Roots pump's performance than temperature: the volumetric and isentropic efficiencies of the Roots-type hydrogen circulating pump decrease by 3.5% and 4.6%, respectively, with increasing temperature, while the volumetric and isentropic efficiencies of the pump increase by 32.6% and 24.0%, respectively, with increasing rotational speed. • The numerical simulation of hydrogen circulation pump using dynamic mesh technique. • Focus on the occurrence and impacts of backflow of hydrogen circulation pumps. • The influence of backflow on internal flow characteristics at different speeds and temperatures. • The general link between return frequency and flow pulsation is discussed in detail. [ABSTRACT FROM AUTHOR]

Fully resolved direct numerical simulations are used to quantify the effect of evolving heat, due to idealized smoldering processes, on the aerodynamic forces of a spherical particle, representing an idealized fixed-shape firebrand particle. Firebrand particles are small glowing particles that are generated in fires and can be transferred long distances by the wind and create new spot fires. Understanding the transport of firebrands is of great importance in fire science. The simulations are performed at a Reynolds number of 500, relevant for a wide range of firebrand size and wind velocity combinations. The spatiotemporal variation of temperature over the surface of the particle is obtained using a detailed surface energy balance analysis. The firebrand particle is assumed to have the thermal and material properties of pine needles and has a Biot number larger than unity, which means that the particle undergoes notable internal temperature gradients. The results indicate that the buoyancy-induced flow around the particle significantly modifies the trailing vortices and produces two non-interacting tunnel-shaped plumes in the wake of the sphere as the particle's Richardson number increases. As a result, the particle's drag and lift coefficients show large deviations from those of a non-heated particle and an isothermal particle. The increased surface temperatures result in an increase in the drag force while inducing a negative lift. The significant variations seen in the aerodynamic forces as a function of the particle's instantaneous temperature indicate that the influence of the transient thermal conditions of firebrands should be considered in the prediction of the particles' trajectory and landing spots. [ABSTRACT FROM AUTHOR]

In proceeding with the advanced development of small unmanned aerial vehicles (UAVs), which are small flying machines, understanding the flight of insects is important because UAVs that use flight are attracting attention. The figure-eight trajectory of the wing tips is often observed in the flight of insects. In this study, we investigated the more efficient figure-eight motion patterns in generating lift during the hovering motion and the relationship between figure-eight motion and Reynolds number. For this purpose, we compared the ratios of the cycle-averaged lift coefficient to the power coefficient generated from each motion by varying the elevation motion angle, which is the rotational motion that represents the figure-eight motion, and the Reynolds number. The result showed that the motion with a smaller initial phase of the elevation motion angle ( φ e 0 ≤ 90 ° ) could generate lift more efficiently at all Reynolds numbers. In addition, the figure-eight motion was more effective when the Reynolds number was low. [ABSTRACT FROM AUTHOR]

One of the factors significantly influencing the flow structures and vortices formed on delta wings is the shape of the leading edge. This study examined the impact of needle vortex generators, inspired by owl wings, on the flow characteristics over a slender delta wing with a sweep angle of 65° to improve its aerodynamic performance. These nature-inspired vortex generators were designed to apply no additional flow blockage or drag force. Flow visualization tests were conducted in a smoke tunnel to gain deeper insights into the effects of the vortex generators on the flow physics over the delta wing. The experiments were performed at three angles of attack of 10°, 15°, and 20° and a flow velocity of 2.6 m/s on two delta wings, with and without needle vortex generators at the leading edge and a Reynolds number of Re = 2.6 × 10 4 . Flow visualization was conducted on six longitudinal sections, six transverse sections, one-floor surface section, and one leading edge section at three different angles of attack. In addition, the investigation involved assessing the vortex breakdown location and wake region. The formation of the vortices and the effects of the needle vortex generators on the temporal and instantaneous flow structures and vortices were also investigated. The results suggested that the use of the needle vortex generators along the leading edge of the delta wing made the vortices smaller and closer to the wing surface and wing axis, postponed the vortex breakdown by approximately 13% of the chord length, and decreased the fluctuations of vortex breakdown location. In addition, the use of needle vortex generators eliminated the secondary vortices. [ABSTRACT FROM AUTHOR]

With a global population estimated at 2000 individuals between Argentina and Chile, less than 1% of its historical population, the huemul (Hippocamelus bisulcus) is categorized as "Endangered". Through a population viability analysis, we sought to estimate the viability of two huemul populations under different threat scenarios. Through a sensitivity analysis, we expected to identify those threats, and environmental or population variables that are more relevant for each population survival. Our main goal is to contribute to the management of the species in Chile through threats prioritization seeking to focus future conservation strategies. This research involved huemul populations from the Nevados de Chillán-Laguna del Laja Biological Corridor Biosphere Reserve (NCLL) and the Cerro Castillo National Park (PNCC). The NCLL population showed a very low probability of survival with a mean time to extinction of 45.9 years; in contrast, PNCC population exhibited a higher probability of survival with a mean time to extinction of 68.6 years. Predation and harassment by dogs seem to have the most significant negative impact on both populations' fate. Additionally, populations were highly sensitive to the percentage of reproductive females and female mortality. Based on our findings, we proposed concentrating conservation efforts on reducing or eliminating dogs' chances to attacks and predate huemul, as well as to focus surveillance actions on females. [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]

Multi-principal element alloys (MPEAs) exhibit outstanding strength attributed to the complex dislocation dynamics as compared to conventional alloys. Here, we develop an atomic-lattice-distortion-dependent discrete dislocation dynamics framework consisted of random field theory and phenomenological dislocation model to investigate the fundamental deformation mechanism underlying massive dislocation motions in body-centered cubic MPEA. Amazingly, the turbulence of dislocation speed is identified in light of strong heterogeneous lattice strain field caused by short-range ordering. Importantly, the vortex from dislocation flow turbulence not only acts as an effective source to initiate dislocation multiplication but also induces the strong local pinning trap to block dislocation movement, thus breaking the strength-ductility trade-off. [ABSTRACT FROM AUTHOR]

Considering the importance of wind turbine tower, its vibration under multi-hazard action consisting of vortex-induced load and seismic load needs to be controlled, especially as the height of the wind turbine tower increases, it increases the risk of its higher-order vibration. To address this issue, theoretical equations for vortex-induced load based on the governing equation of particle damping system are put forward, the vibration control of a 1/20 scale wind turbine model is studied, and the experimental and numerical analyses are conducted. Many studies have shown that wind turbine tower equipped with tuned mass damper (TMD) can result in an RMS response reduction ratio ranging from 20% to 40%. Compared to TMD, particle tuned mass damper (PTMD) has better vibration control effect under single seismic load, and still achieves good vibration control ability with a maximum RMS (root–mean–square) reduction ratio of 35.55% under multi-hazard action. Furthermore, MPTMD (multiple particle tuned mass damper) is proposed for controlling higher-order vibration mode, achieving a maximum RMS reduction ratio of 65.93%. Combining the spectrum diagram result, the ability to control higher-order mode vibration of MPTMD is confirmed. [ABSTRACT FROM AUTHOR]

The particles of micron and submicron sizes (PM 2.5 and less) in gas environments pose a significant danger to humanity due to the emergence of specific and very dangerous diseases of the cardiovascular, respiratory, and immune systems of the human body. Such particles are the most difficult to detect; therefore, their effects on human health have only been discovered in recent decades. Classical ultrasonic coagulation by sinusoidal action turns out to be ineffective for PM 2.5 due to the peculiarities of the physical mechanisms of hydrodynamic and orthokinetic interaction realized in gaseous media. This article presents a theoretical justification for choosing ways to increase the efficiency of ultrasonic coagulation of PM 2.5 by creating special conditions under which nonlinear disturbances of the velocity and pressure of the gas phase in the ultrasonic field occur. The authors performed simulations of ultrasonic coagulation under nonlinear disturbances of the velocity (vortex) and the pressure (shock waves), which has numerical difficulties due to the instability of existing methods. As a result of the numerical analysis, the possibility of increasing the coagulation rate of particles in the submicron size range up to limit values (13 times due to nonlinear pressure disturbances, and an additional increase of at least 2 times due to aerosol compaction in the vortex field of gas velocity) was shown. [ABSTRACT FROM AUTHOR]

Expressions are obtained for the position of the maximum Imax of the Fourier transform of a Bessel–Gaussian beam (BGB) and its dependence on the topological charge is substantiated. It is found that Imax depends on the angle of the cone and the parameters of the Gaussian beam. Here, as the cone angle is reduced (and, therefore, the diffraction-free region increases), the distances between the maxima of the intensity distributions in the focal plane of the lens, corresponding to different magnitudes of the topological charge, increase. An expression is found for the position of the energy center of the Fourier transform of the BGB and it is shown that it also depends on the cone angle γ and the size of the Gaussian beam waist w0. As the product γw0 increases, the shift in the energy center of the BGB relative to the radius R of the annular Fourier spectrum in the approximation of geometric optics decreases. These results reveal the impossibility of forming perfect vortices with a BGB. Here the degree of their "imperfection" is determined by the deviation of the maximum of the intensity distribution in the focal plane of the lens on the parameter R which specifies the radius of the ring of the Fourier image of the Bessel beam, which is greater for beams with a larger diffraction-free region. [ABSTRACT FROM AUTHOR]

In this paper, we consider the formation of vortices in multilayer stacks of Bose–Einstein condensates with tilted dipoles by numerical simulations of the Gross–Pitaevskii equation. Different dependencies of critical rotation frequency (CRF) and optical lattice height, vortex number, and rotation frequency are studied, depending on the direction of the dipole axis and dipole strength. Our results show that the CRF in z = 0 is minimum. When the optical lattice height is gradually increased, the CRF decreases gradually. Reducing of dipole strength in anisotropic dipole–dipole interaction (DDI) favours the formation of vortices, and such decline in isotropic DDI hinders the creation of vortices. The reason for this difference is that the repulsive interaction is favorable and the attractive interaction is disadvantageous for the vortex formation. In addition, we study the first-order correlation function and focus on variation of coherence. For small rotation frequency, the break of coherence occurs earlier in the case of purely repulsive interaction. With an increase in rotation frequency, the coherence concurrently disappears in layer z = 2. Moreover, we also investigate the quenched dynamics, showing that the increase of angular momentum is induced by changing the direction of dipoles and in this process the vortex number remains unchanged. [ABSTRACT FROM AUTHOR]

This study presents an analysis of heat transmission and magnetic nanofluid flow in a minichannel with corrugated upper wall and exposed to a magnetic field. Choice of this geometry allows an improvement of heat transfer contrary to that of rectangular shape. This study is developed to complete the existing ones in the literature. In this two-dimensional study, flow is supposed to be laminar, and the chosen fluid is Fe3O4-water magnetic nanofluid which is used as cooling fluid. For this nanofluid, two volume fractions (0.6, 1%) were used. Several simulations were conducted for a series of Reynolds numbers which vary between 150 and 210 and magnetic field strengths which take values ranging from 0 up to 1400 G for two chosen configurations (a source located at 15 mm and two sources located, respectively, at 7.5 and 15 mm). The results obtained show that magnetic nanofluid subjected to a magnetic field seems as an active vortex generator which modifies the flow structure, allowing a good mixing of the fluid and consequently an improvement in heat transmission. For selected values of magnetic field intensities, an improvement in heat transmission was observed followed by a reduction in pressure drop. This is due to the separation of the fluid from the lower wall which reduces the friction effect. Rise in volume fraction does not modify the flow structure, and it allows an enhancement in heat transfer. According to results obtained, we note a maximum of 10.21% enhancement of heat transmission in the case of a source located at 15 mm and a maximum of 27.44% of improvement of heat transmission in in the case of application of two sources for the case where the volume fraction is equal 1%. With this study, we can locate the correct position of the magnets allowing a good heat transfer rate. [ABSTRACT FROM AUTHOR]

By numerically solving the Gross–Pitaevskii equation with phenomenological dissipation term, we study the vortex formation properties of a three-dimensional dipolar Bose–Einstein condensate of 164Dy atoms. We studied the influence of the contact interaction between atoms on the formation mechanism of vortices. We also study how the dipole orientation affects the vortex formation properties and the number of vortices. We find that enhancing the interaction of short-range repulsion interaction or dipolar repulsion interaction can shorten the time to form a stable vortex structure and increase the number of vortices. [ABSTRACT FROM AUTHOR]

There are various secondary flow types in turbodrill's blade cascades, and all kinds of secondary flow have a significant effect on flow loss. In this paper, the stator cascade of φ160 mm turbodrill is taken as the research object, and the CFD method is used to analyze the secondary flow and its evolution. The origin and evolution mechanism of secondary flow is explained from the flow mechanism. The results show that when the working rotary speed is lower than the design rotary speed, the secondary flows are composed of suction surface separation vortex, horseshoe vortex, and passage vortex coexisting. The intensity of secondary flows increases with the decrease of rotary speed. When the working rotary speed is near the design rotary speed, the secondary flows include horseshoe vortex, passage vortex, and corner vortex. When the working rotary speed is higher than the design rotary speed, the secondary flows consist of pressure surface separation vortex and suction surface trailing edge separation vortex. Regardless of rotary speed, secondary flow intensity in the shroud region is greater than the hub region, which has a greater influence on the mainstream. In addition, compared with high rotary speeds, secondary flow intensity is greater at low rotary speeds, resulting in greater flow losses. [ABSTRACT FROM AUTHOR]

In this study, the critical submergence of deep well pumps is analyzed. The critical submergence, which is an important parameter for centrifugal pumps and water intakes that usually have a certain diameter, is determined using dimensionless quantities. The innovative aspect of this study is that three different water inlet opening models are created for two shaft pumps with different nominal diameters, these models are related to the water inlet diameters and the critical submergence is defined using dimensionless quantities. The critical submergence of the pumps was determined using a vacuum measurement method and the critical submergence of each model at different flow rates was compared with Froude number dependent submergence equations developed by other researchers. The aim of this study is to determine the critical submergence of the pumps and to use the flow models developed at these depths with the aid of mathematical equations to ensure the operation of the pumps in the reliable zone (vortex-free). The physical models were found to be effective for vortex formation depth and vortex shape. The physical models found Fcr (critical Froude number) ≤1.40 for pump P1 and Fcr ≤1.44 for pump P2, these values can also be used to determine the suction lift of the pumps. The critical Weber and Reynolds numbers decrease as the water suction area of the pumps increases. Considering the depth of vortex formation, it would be appropriate to use the original (D0) physical models for both pumps. As a result, dimensionless quantities can be used to determine the critical submergence of deep well pumps. [ABSTRACT FROM AUTHOR]

The objectives of this paper are to pursue an accurate numerical method of unsteady cavitating flow at a reasonable calculation cost and investigate the unsteady cavitating flow characteristics of a centrifugal pump. Firstly, the cavitating flow simulations of a centrifugal pump were performed using the partially-averaged Navier–Stokes (PANS) turbulence model and its improved model to evaluate the numerical methods based on experimental data. Compared with the experimental results, the improved PANS turbulence model can better predict the cavitating flows in the pump and has better applicability. Further, the unsteady cavitating flow characteristics of the centrifugal pump, such as the vapour volume fraction, the cavitation-vortex dynamics and the pressure and head fluctuations, were simulated by improved PANS model and discussed. The liquid flow vortex at the end of the cavitation in the impeller is an important reason for the periodic change of the cavitation shape. The periodic change of cavity volume has a certain impact on the pressure pulsation in the impeller and the pump head. [ABSTRACT FROM AUTHOR]

The T-junction structure with one inlet and two outlets is ubiquitous in natural and aerospace systems. However, previous research has mainly focused on vortex breakdown under steady-state flow in symmetrical structures. Limited research has been conducted on vortex breakdown in asymmetric structures, where the radii of the two channels differ. This creates a flow rate difference between the outlets, and the ratio of mass flow rate in the small channel to the large channel is defined as the splitting ratio. To study the appearance of vortex structures in the outlet channel under different flow rates and splitting ratios, a split-type asymmetrical circular cross-section pipeline experimental system that can be flexibly disassembled was designed and built. Pressure signals of each channel using pressure sensors were measured and analyzed. It is worth noting that a string tracing technology combined with particle image velocimetry (PIV) technology to monitor the outlet channel was adapted to visualize the flow. Results show that the pressure oscillations in the channels of the T-junction are related to the splitting ratio. Besides, asymmetric T-junction structure exhibits different large vortex structure formation and breakup processes in the two outlet channels, and these processes are influenced by the splitting ratio. • A new split-type asymmetrical T-junction experimental system was designed • Splitting ratio plays important part in pressure oscillation and vortex formation • A string tracing technology was first adapted to visualize the flow • Particle image velocimetry (PIV) technology was modified to visualize the flow • Flow characteristics exhibit a non-linear correlation with the splitting ratio [ABSTRACT FROM AUTHOR]

Obstruction of the LVAD flow path can occur when blood clots or tissue overgrowth form within the inflow cannula, pump body, or outflow graft, and it can lead to thrombus, embolism, and stroke. The goal of this study was to measure the impact of progressive pump inflow obstruction on the pressure and flow dynamics of the LVAD-supported heart using a mock circulatory loop. Pump obstruction (PO) was produced by progressively blocking a fraction of the LVAD inlet area. Pressures, flows, and the midplane velocity field of the LV were measured for three LVAD speeds and six PO levels. Pressure and flow decreased with PO, shifting more of the flow through the aortic valve such that the total flow decreased by 6–11% and decreased the efficiency of the work of the native heart up to 60%. PO restricts diastolic flow through the LVAD, which reduces mitral inflow and decreases the strength and energy of the intraventricular vortices. The changes in flow architecture produced by PO include flow stasis and increased shear, which predispose the system to thromboembolic risk. Analysis of the contributions to external work may enable early detection, which allows time for therapeutic intervention, reducing the likelihood of pump replacement and the risk of complications. [ABSTRACT FROM AUTHOR]

To reveal how aircraft affects the internal flow of the ejector nozzle, we have constructed three model types in this article. These include the model of SR-71 aircraft, the model that only contains ejector nozzle with third auxiliary valve, and the model that integrates the previous two. The results showed that in the transonic regime (Ma = 1.2), the third auxiliary flow mainly stems from the boundary layer of the aircraft body. Indeed, a large-scale flow separation phenomenon near the third auxiliary door may require a more nuanced description. The mainstream flow is always in an overexpansion state and results in a Mach plate structure at the exit of the nozzle. However, after integration, the rates of the third auxiliary and the secondary flow are reduced by 18.15% and 5.26%, respectively. Meanwhile, the mainstream flow demonstrates higher overexpansion levels, the position of the Mach plate further downstream changes, and the thrust coefficient decreases by 1.75%. It is worthwhile noting that a strong pressure gradient occurs in the circumferential direction near the connecting structure, which induces lateral flow. This lateral flow breaks away from the wall under the reverse pressure gradient of the nozzle, thus forming three vortex pairs. [ABSTRACT FROM AUTHOR]

Abstract This study employed computational fluid dynamics-discrete phase model (CFD-DPM) to investigate the transport characteristics of transient high-temperature dust in a vertical tee duct. Utilizing the large eddy simulation (LES) model, the research elucidated the flow characteristics, temperature field distribution, and particle deposition patterns within the tee duct. Specifically, it was observed that the vortex generated by the tee duct dissipated when x/D exceeds 20. Furthermore, high-temperature fluid exhibited an upward migration within the pipe by buoyancy, concurrently intensifying flow velocity fluctuations. Particle diffusion was initially driven by particle inertia and later became dominated by the combined effects of vortex and buoyancy. The deposition of particles displayed a trend of a sharp increase and decrease, then a gradual increase and decrease along the duct. The particle deposition can be divided into three stages, each governed by varying influencing factors on particle movement: (a) particle inertia within the range 0 < x/D < 5; (b) vortex carry spanning 5 < x/D < 20; and (c) turbulent pulsations beyond 20 < x/D. The total deposition mass was decreased by 50% by the vortex. This article provides a comprehensive description of the diffusion and deposition of transient high-temperature dust in a tee duct. [ABSTRACT FROM AUTHOR]

Abstract In order to improve the efficiency of the conventional serpentine solar air heaters, this article proposed a serpentine solar air heater containing a triangular spoiler. A 3-D verified mathematical model of serpentine solar air heaters with triangular spoilers was established. The results showed that the arranging triangular spoiler had a positive effect on enhancing the thermal performance of solar air heaters. It could be seen from the velocity and temperature contours that the triangular spoiler could reduce the intensity and area of the vortex zones, and hence decrease the temperature dead zone in the flow channel. The collection efficiency reached its peak value when the angle of triangular spoiler was 64°. Compared with the nontriangular spoiler, the collection efficiency was increased by 4.4% ∼6.2%. In general, the optimal angle of triangular spoiler was determined to be 40° by comprehensive analysis of effective efficiency. [ABSTRACT FROM AUTHOR]

New-type vortex structures in a 3D ferromagnet—vortex rings—are predicted. It is established experimentally that these structures have finite energy. The nature of the interaction of pairs of such rings in the simplest cases is investigated. [ABSTRACT FROM AUTHOR]

Objectives: Blood‐flow pattern is an essential factor in cardiovascular development. Recently, blood speckle‐tracking echocardiography (BST) based on high‐frame‐rate ultrasound has emerged as a promising technique for the assessment of blood‐flow patterns and properties. The objectives of this study were to determine the feasibility of BST in the fetus and to assess intracardiac blood‐flow patterns of fetuses with a congenital heart defect (CHD) using this technique. Methods: This was a prospective study consisting of 35 normal fetuses, 35 fetuses with left‐sided obstructive lesion (LSOL) and 35 fetuses with right‐sided obstructive lesion (RSOL). BST images of fetal intracardiac regions of interest (ROIs), including the left ventricle (LV), right ventricle (RV), ascending aorta (AAo), aortic arch (AA), descending aorta (DAo) and pulmonary artery (PA), were obtained and analyzed. The feasibility of BST was assessed, and blood‐flow pattern and number of vortices in the ROIs were recorded. Results: The median gestational age of the fetuses was 24.7 weeks (range, 19.6–34.3 weeks). BST was feasible in 81.6% of cases, and the cut‐off value of depth for an adequate BST image was ≤ 7.9 cm. There were no differences in the presence of vortex/turbulent blood flow in the LV or RV among the three groups. Vortex/turbulent blood flow in the AAo was detected in 0% (0/35), 14.3% (5/35) and 57.1% (20/35) of cases in the control, LSOL and RSOL groups, respectively. The respective values were 5.7% (2/35), 14.3% (5/35) and 51.4% (18/35) for the AA; 0% (0/35), 48.6% (17/35) and 0% (0/35) for the DAo; and 0% (0/35), 40.0% (14/35) and 51.4% (18/35) for the PA. With the exception of the DAo in the RSOL group, vortex/turbulent flow in the great artery ROIs was significantly more common in the LSOL and RSOL groups than in controls (P < 0.01). In the LSOL group, the number of vortices in the AAo, AA, DAo and PA was significantly greater compared with that in controls (P < 0.01). In the RSOL group, the number of vortices in the LV, AAo, AA and PA was significantly greater compared with that in controls (P < 0.01). Conclusions: Fetuses with CHD were more likely to exhibit vortex/turbulent blood flow and increased number of vortices in the great arteries compared with healthy controls. Further research is needed to determine the biomechanical effect of blood‐flow patterns, especially vortex flow, on fetal cardiovascular structure and function. © 2023 International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

The evolution of unforced and weakly damped two-dimensional turbulence over random rough topography presents two extreme states. If the initial kinetic energy E is sufficiently high, then the topography is a weak perturbation, and evolution is determined by the spontaneous formation and mutual interaction of coherent axisymmetric vortices. High-energy vortices roam throughout the domain and mix the background potential vorticity (PV) to homogeneity, i.e., in the region between vortices, which is most of the domain, the relative vorticity largely cancels the topographic PV. If E is low, then vortices still form but they soon become locked to topographic features: Anticyclones sit above topographic depressions and cyclones above elevated regions. In the low-energy case, with topographically locked vortices, the background PV retains some spatial variation. We develop a unified framework of topographic turbulence spanning these two extreme states of low and high energy. A main organizing concept is that PV homogenization demands a particular kinetic energy level E#. E# is the separator between high-energy evolution and low-energy evolution. [ABSTRACT FROM AUTHOR]

Here we consider a model of an isolated vortex to understand the vertical dynamics induced by mesoscale eddies in the ocean. We use the analytical solutions to a balanced model for an ellipsoid of uniform potential vorticity to examine how the vertical motions induced depend on the vortex shape and its orientation, i.e. whether the vortex is vertically upright or tilted with respect to the vertical axis. The motion induced by the vortex can be divided into two kinds: (1) the interior flow which acts on the vortex itself and (2) the exterior flow which acts on its surroundings. For an upright ellipsoid, there are no self-induced vertical motions and the vortex rotates steadily about the vertical axis. However, for a tilted ellipsoid we find solutions exist where the vortex rotates about the vertical axis, while the vertical motions cause the tilt angle of the vortex to oscillate. This effect is stronger as the tilt angle is increased. Considering the exterior flow, there exists an exterior vertical velocity for the upright and tilted ellipsoids. However, the dynamics induced by the exterior vertical velocity is very different for the upright and tilted cases. We find that for an upright ellipsoidal vortex, the vertical motions are largest for vortices with high horizontal eccentricity and a vertical height-to-width aspect ratio near unity, vanishing as the horizontal cross-section of the vortex becomes circular. Instead for the tilted case, the vertical motions are largest when the horizontal cross section is circular, and for strongly prolate vortices, with the largest vertical motions occurring when the tilt angle is 45 ∘ . [ABSTRACT FROM AUTHOR]

The article considers an approach to the description of random fields as a set of intense structures with random parameters. Such structures are observed both in optical fields propagating in inhomogeneous media and fields of hydrodynamic origin and are formed because of focusing on radiation or deformation of flows. The article discusses the filtration methods and the evolution of such structures. Different modes of structures, modes of periodic and stochastic oscillations, are described. [ABSTRACT FROM AUTHOR]

A gun-track launcher that combines a balanced gun with a rocket track is an important technology for the non-destructive recovery of high-value projectile weapons. Given the restrictions imposed by the track and the interference caused by it, the muzzle jet of such launchers is significantly different from those of traditional artillery. Given this engineering background, this study examines the characteristics of the evolution of supersonic muzzle jets with different constrained boundaries. Results show that the structure of the muzzle jet undergoes a distortion that changes its symmetric circumferential shape into an asymmetric one, tilted above the center of the muzzle. Vortexes are generated below the track owing to lateral airflow, and their formation and evolution lead to significant changes in the pressure of the flow field. Moreover, the asymmetry of the flow field varies owing to the different structures of the side plates of the track, which leads to varying characteristics of the development of shock waves and vortexes in the muzzle jet. The content of this article provides a theoretical basis and necessary technical support for enriching the research connotation and engineering applications of shock wave fields. [ABSTRACT FROM AUTHOR]

A vehicle is more stable when the geometric center, center of gravity, and stagnation point are in line. However, the inflow direction and velocity magnitude of the operational environment of road vehicles are varying. This study aims to investigate the aerodynamic behavior of a water-drop-shaped vehicle under side wind conditions. Some essential aerodynamic performances of the vehicle are numerically and graphically analyzed at 0 deg, 10 deg, and 20 deg of side wind directions. The value of the coefficient of drag, drag force, coefficient of lift, and lift force exponentially increases as the yaw angle elevates. The lower part on the area of the front-wheel compartment becomes the critical location indicated by the results on pressure coefficient, friction coefficient, and total wall shear stress distribution along the vehicle surface. Increasing the side wind angle triggers more significant vortex regions generated around the wheel compartment and on the leeward side of the vehicle. [ABSTRACT FROM AUTHOR]

The discovery of nematic triplet superconductivity in doped topological insulators CuxBi2Se3 triggers interest in the identification of the d-vector of the triplet, which is related to the antinodal direction of the gap function and determines whether the superconductor is topological. We perform self-consistent analysis of the vortex state properties in a nematic spin-triplet px-wave superconductor. We first derive a Ginzburg-Landau theory to determine the shape of the vortex and vortex lattice. We find the spatial profile of the isolated vortex is elongated along the antinodal direction, and the vortex lattice is a distorted triangular lattice elongated along x, becoming square in the specific case of a small circular Fermi surface. Finally, we calculate the local density of states self-consistently for an isolated vortex and the vortex lattice using the microscopic Bogoliubov-de Gennes equation. We find that the profile of the local density of states at low in-gap energies is always elongated along the antinodal direction. Our findings are valuable for the experimental detection of the antinodal direction of the gap function in nematic triplet superconductors, and subsequently the identification of the topological character of the superconducting state as in CuxBi2Se3. [ABSTRACT FROM AUTHOR]

The formation of vortices behind the gates of diversion dams is an operational challenge. Such vortices lead to vibration and corrosion in the gate, reducing the lifetime and raising the operational cost of the dam. This study investigated these vortices and their formation. It was found that the gate or cutoff wall was not the only explanation for the vortices; the closed side gates also contribute to vortex formation. Furthermore, an increase in the gate width reduced vorticity; the vortex size experienced a 200% reduction as the gate size increased by 200%. The cutoff wall diameter was another determinant. An increase in the cutoff wall diameter raised vorticity. The vortices increased by 50% as the wall diameter increased by 150%. [ABSTRACT FROM AUTHOR]

[Display omitted] It was shown that at 298 K and 100–300 Torr, the flame front of a well-mixed dilute methane–oxygen mixture, propagating to the ends of hollow cylindrical and conical obstacles, does not form a vortex shedding behind them; however, under the same conditions, this instability occurs when hot products flow behind the obstacles. [ABSTRACT FROM AUTHOR]

Piezoelectric energy harvesters (PEHs) are a kind of energy harvester that generates electricity due to pressure or vibration. Vortex-induced vibration (VIV) is a method that utilized wind energy and bluff body to generate the vibration in PEH. The objective of this research was to study the output voltage that generates in different bluff bodies with various airflow velocities. Experimental and simulation have done in this study. Experimental used PEH that consists of piezoelectric bimorph and rectangular-trapezoid fin. Bluff bodies with various cross-sectional areas, namely rhombus, square, and triangle were set up in front of the PEH at a distance of 80 cm. The various air velocities are set up to 5, 7, and 9 m/s in the wind tunnel with a cross-section of 250 mm × 250 mm. The simulation used the finite element method in explore the fluid flow pattern. The rhombus cross-sectional bluff body can generate voltage with an average of 1.5 volts. It is more voltage generated than a square and triangle. A vortex is formed near the rhombus bluff body and generates pressure fluctuation in its wake region. This pressure fluctuation takes place until airflow hits and leads PEH to vibrate and generate the voltage. [ABSTRACT FROM AUTHOR]

Hydropower is one of the most sustainable and desirable renewable energy sources. Gravitational water vortex hydro turbine (GWVHT) systems are one of the most suitable and sustainable renewable power generation devices for remote and rural areas, particularly in developing countries, owing to their small scales and low costs. There are various GWVHT systems with different configurations and various operating conditions. The main components of a GWVHT system include the inlet and outlet channels, a basin, and a turbine on which there are a number of blades attached. This paper presents a comprehensive review regarding the progress and development of various GWVHT systems, covering broad aspects of GWVHT systems, particularly various types of basins, inlet and outlet channels, turbines with blades which have different shapes, orientations, sizes, numbers, etc. The nature of the previous studies is summarised. The fundamentals of the vortex dynamics involved and the quantitative analysis of the performance of GWVHT systems are also described. The turbulence models and multiphase models used in some leading numerical simulation studies have been reviewed. As a case study, the implementation of a GWVHT system in PNG is presented. Based on the review of previous studies regarding GWVHT systems, the major issues and challenges are summarised, and some key topics are recommended for future research work on the performance of GWVHT systems. [ABSTRACT FROM AUTHOR]

A review of fundamental theoretical studies concerning the theory and application of the nonsteady-state analogy to an incompressible fluid flowing around slender bodies is presented. Problems related to the application of nonsteady-state analogy to wings, to the wake behind an elliptically loaded wing, as well as methods for numerical calculation of the evolution of vortex sheets and for determining the positions of lines of low separation from solid surfaces are considered taking into account viscous-inviscid interactions. The issues of nonuniqueness and asymmetry of solutions for the problems of a separated flow moving around slender bodies are discussed. [ABSTRACT FROM AUTHOR]

A review of fundamental theoretical publications is presented, wherein the flow of an incompressible fluid in the cores of three-dimensional vortex sheets formed in the case of the separated flow of low-aspect-ratio wings are considered. Problems concerning an inviscid-fluid flow in the core of a conical vortex sheet and a vortex sheet vanishing from the edges of a parabolic wing, as well as the problem of a viscous-fluid flow in the core of a conical vortex structure, are considered. [ABSTRACT FROM AUTHOR]

A review of fundamental theoretical studies concerning plane vortex flows in an incompressible fluid is presented. Problems connected with flow in the vicinity of the point of a vortex sheet vanishing from a solid surface, with self-similar flows of an ideal and viscous fluid, with flow in the cores of spiral vortex sheets, with the stability and diffusion of vortex flows, and with the development of a theory of boundary-layer separation from a solid surface are considered. [ABSTRACT FROM AUTHOR]

The term "vortex" refers to a region in a fluid where the flow spin around an axis line, which could be flat or curved. Vortices can twist, stretch, move, and interact in several situations, once they are formed. The angular and linear momentum, along with some energy and mass, are all noticeable in a rotating vortex. Descriptions of vortices developed in various flows include smoke rings, dust devils, cyclones, and the wind surrounding a tropical tornado. The existence of vortices in the natural environment makes it important for researchers to explore them when and wherever they are encountered. Magnetic field effects include numerous technical applications such as: B. Extraction of geothermal energy, casting of metals, cooling of nuclear reactors. Hybrid nanofluids, on the other hand, are more effectively accepted as next-generation thermal systems in automotive cooling applications, heat exchangers, and HVAC due to their higher thermophysical properties. The purpose of this work is to study how local magnetic fields affect the magnetic flux of a hybrid nanofluid inside an enclosure induced by a magnetic source. We implement a single-phase model (SPM) to classify hybrid nanofluids and computationally evaluate the associated partial differential equations (PDEs). The results reflect that the localized magnetic field generates a counter-rotating vortex in the flow which breaks apart the other vortex and hence becomes strengthened. The vortex elongates along the direction of the localized magnetic field and tends to occupy a major part of the cavity. Magnetic field decreases in the thermal gradient near the horizontal walls of the enclosure. The faster-moving lids cause more rigorous mixing of the layer of fluid at different temperatures, which distorts the uniformity of the pattern of isotherms. Finally, heat transport is more affected by the magnetic field as compared to skin friction. [ABSTRACT FROM AUTHOR]

Pumped-storage power plants change operating conditions frequently, which seriously affects the safe operation of the unit operating under non-design conditions. In this study, the relationship between the flow structure with different guide vane openings (GVOs) of pump-turbine under the runaway condition is discussed. Moreover, the internal flow characteristics and the pressure fluctuation under the runaway condition are investigated. The dominant pressure fluctuation with 7 f n is obtained in the vaneless and double-row cascade space of pump-turbine under runaway conditions. The pressure fluctuation of large GVOs is more serious than that of low GVOs in general. The pressure fluctuation amplitude exists to the most significant amount in the vaneless space of pump-turbine to compare with the other component. The rotating stall is observed with a large guide vane opening under the runaway conditions. Nevertheless, the rotating stall disappears with a small GVO of 6 mm. [ABSTRACT FROM AUTHOR]

The wood turtle (Glyptemys insculpta) is experiencing widespread declines throughout its range in the eastern United States and Canada. Maine has been considered a stronghold for the species due to an abundance of suitable upland and stream habitat. Furthermore, recent studies have identified Maine as a potentially important climate refuge for wood turtles. Using data collected in a 5-yr capture–mark–recapture study on a wood turtle population in central Maine, we estimate population size, apparent survival rates, population growth rates, and population viability. We also performed a sensitivity analysis to illustrate the impacts of slight perturbations to demographic rates. Our estimated total population size is 73 (95% CI = 69–85) individuals. Annual apparent survival varied across years, ranging from 80.5% to 97.5%, with females having a slightly higher survival at 94.9% (95% CI = 81.6%–97.8%) than males at 92.8% (95% CI = 77.6%–97.4%). The baseline population viability analysis model predicted a k of 0.93 (95% CI = 0.91–0.95) and a 100% probability of extinction within 150 yrs. Despite some broad permutations in our baseline demographic parameters, there were no scenarios included within our sensitivity analysis that increased the population's growth rate to a positive value. These results have implications for the long-term persistence of wood turtles in Maine and throughout their range. Our study helps fill a need for current data from this area that may be used to inform both local and regional management plans. [ABSTRACT FROM AUTHOR]

Vortex electromagnetic waves have superior performance over electromagnetic waves. In order to improve the radar super-resolution lateralization technique in its missing modes, this study proposes to start from the perspective of mode missing. The missing modes are reconstructed using the Adaptive Step Size Gradient Descent (ASSGD) method by exploiting the features of the missing modes. The linear minimum mean square error (LMMSE) estimation method is also used to solve the problem of poor reconstruction accuracy due to the Missing Modes. The Missing Modes Iterative Adaptive Approach (MMIAA) algorithm and Missing Modes Sparse Learning via Iterative Minimization (MMSLIM) algorithm are then used. Minimization (MMSLIM) algorithm to recover missing modes. The results showed that the RMSEs of the recovery errors of MMSLIM, MMIAA and ASSGD were 0.16, 0.31 and 0.82 respectively at a modal missing ratio of 0.7, while ASSGD fails to recover the missing modal data at a modal missing ratio of 0.9. The overall data quality of the azimuthally estimated RMSE was average when the signal-to-noise ratio was at [-5, 10] dB. And the curve becomes flatter when it reaches 15 dB or more, indicating that MMSLIM, MMIAA has important theoretical and practical value. [ABSTRACT FROM AUTHOR]

Simple Summary: Wildlife conservation effectiveness relies on the accuracy of population data used to build management plans. Estimating population size and dynamics of large vertebrates living on wide areas is a challenging task and results can vary depending on the methods adopted. In the present study, the size of a wolf population was estimated both by field monitoring and statistical modeling on demographic data. Results showed discrepancies with respect to previous bibliographic estimates which resulted significantly lower. Moreover, statistical techniques on demographic data allowed a deeper knowledge of population's trend, pointing out the importance of mortality rates in driving population growth. We suggest combining statistical modeling and field monitoring to achieve a satisfactory knowledge of population size and dynamics useful to foster reliable management and conservation plans. We estimated the current size and dynamics of the wolf population in Tuscany and investigated the trends and demographic drivers of population changes. Estimates were obtained by two different approaches: (i) mixed-technique field monitoring (from 2014 to 2016) that found the minimum observed pack number and estimated population size, and (ii) an individual-based model (run by Vortex software v. 10.3.8.0) with demographic inputs derived from a local intensive study area and historic data on population size. Field monitoring showed a minimum population size of 558 wolves (SE = 12.005) in 2016, with a density of 2.74 individuals/100 km2. The population model described an increasing trend with an average annual rate of increase λ = 1.075 (SE = 0.014), an estimated population size of about 882 individuals (SE = 9.397) in 2016, and a density of 4.29 wolves/100 km2. Previously published estimates of wolf population were as low as 56.2% compared to our field monitoring estimation and 34.6% in comparison to our model estimation. We conducted sensitivity tests to analyze the key parameters driving population changes based on juvenile and adult mortality rates, female breeding success, and litter size. Mortality rates played a major role in determining intrinsic growth rate changes, with adult mortality accounting for 62.5% of the total variance explained by the four parameters. Juvenile mortality was responsible for 35.8% of the variance, while female breeding success and litter size had weak or negligible effects. We concluded that reliable estimates of population abundance and a deeper understanding of the role of different demographic parameters in determining population dynamics are crucial to define and carry out appropriate conservation and management strategies to address human–wildlife conflicts. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of the dynamic and thermal behavior of air-flow within a heat exchanger equipped with two distinctive baffles: a perforated baffle and a partially inclined baffle. The influence of hole positioning in the perforated baffle on the overall performance of the heat exchanger is thoroughly investigated through a systematic examination of temperature curves at varying Reynolds number values. The results demonstrate significant enhancements in flow characteristics attributed to the presence of these baffles. The flow structure exhibits prominent main currents across the gaps and secondary currents through the holes. The inclusion of these barriers leads to significant deformations and the emergence of well-developed recycling cells in the form of vortices. Both the perforated and inclined baffles effectively reduce pressure values on their frontal regions, thereby mitigating friction losses. Furthermore, the introduction of a perforation in the lower part of the baffle induces a more turbulent flow compared to the other cases. This is attributed to the expansion of the recirculating cells, resulting in improved fluid mixing and subsequent enhancement of thermal energy gain. These findings offer valuable insights into the design and optimization of heat exchangers, enabling improved performance and efficiency in various engineering applications. [ABSTRACT FROM AUTHOR]

In order to improve the yield of steel produced in the converter and the quality of the molten steel, and to understand the distribution of the flow field in the converter and ladle during the steelmaking process, the CFD fluid simulation software Fluent 2020 R2 was used to analyze the flow field of the converter static steelmaking process. The aperture of the steel outlet and the timing of the vortex formation under different angles were studied, as well as the disturbance level of the injection flow in the ladle molten pool. The study revealed that in the steelmaking process, the emergence of tangential vectors caused the entrainment of slag by the vortex, whereas in the later stages of steelmaking, the turbulent flow of slag disrupted the vortex, resulting in its dissipation. When the converter angle increases to 90°, 95°, 100°, and 105°, the eddy current occurrence time is 43.55 s, 66.44 s, 68.80 s, and 72.30 s, and the eddy current stabilization time is 54.10 s, 70.36 s, 70.95 s, and 74.26 s, respectively. When the converter angle is 100–105°, it is suitable to add alloy particles into the ladle molten pool. When the tapping port diameter is 220 mm, the eddy current inside the converter changes and the mass flow rate of the tapping port is "oscillating". When the aperture of the steel outlet was 210 mm, the steelmaking time could be shortened by about 6 s without affecting the internal flow field structure of the converter. [ABSTRACT FROM AUTHOR]

Policies and measures to control pandemics are often failing. While biological factors controlling transmission are usually well explored, little is known about the environmental drivers of transmission and infection. For instance, respiratory droplets and aerosol particles are crucial vectors for the airborne transmission of the severe acute respiratory syndrome coronavirus 2, the causation agent of the coronavirus 2019 pandemic (COVID-19). Once expectorated, respiratory droplets interact with atmospheric particulates that influence the viability and transmission of the novel coronavirus, yet there is little knowledge on this process or its consequences on virus transmission and infection. Here we review the effects of atmospheric particulate properties, vortex zones, and air pollution on virus survivability and transmission. We found that particle size, chemical constituents, electrostatic charges, and the moisture content of airborne particles can have notable effects on virus transmission, with higher survival generally associated with larger particles, yet some viruses are better preserved on small particles. Some chemical constituents and surface-adsorbed chemical species may damage peptide bonds in viral proteins and impair virus stability. Electrostatic charges and water content of atmospheric particulates may affect the adherence of virion particles and possibly their viability. In addition, vortex zones and human thermal plumes are major environmental factors altering the aerodynamics of buoyant particles in air, which can strongly influence the transport of airborne particles and the transmission of associated viruses. Insights into these factors may provide explanations for the widely observed positive correlations between COVID-19 infection and mortality with air pollution, of which particulate matter is a common constituent that may have a central role in the airborne transmission of the novel coronavirus. [ABSTRACT FROM AUTHOR]