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Diabatic heating by convection in the eyewall often produces an annular region of high potential vorticity (PV) around the relatively low PV eye in a strong tropical cyclone (TC). Such a PV ring is barotropically unstable and can encourage exponentially growing PV waves. In this study, such instability and the subsequent nonlinear evolutions of three TC-like vortices with different degrees of hollowness PV ring on an f-plane are first examined using an unforced, inviscid shallow-water-equation model. Results show that the simulated eyewalls evolve similarly to those in the nondivergent barotropic model. It is also found that the polygonal eyewall structure can be decomposed into vortex Rossby waves (VRWs) of different wavenumbers with different amplitudes, allowing for wave-wave interaction to produce complicated behaviors of mesovortices in the TC eyewall. The same set of PV rings has been examined on a beta-plane. Although the beta effect has been rendered unimportant to the eyewall evolution due to the relatively small-scale of inner-core circulation, it is shown in this study that the beta effect may erode the coherent structure of mesovortices in the eyewall of an initially hollow PV-ring vortex. Mesovortices modeled on the beta-plane with greater beta parameter tends to experience an earlier breakdown along with the enhanced radial gradients of the basic-state (azimuthal mean) angular velocity, followed by wave-wave and wave-flow interactions, leading to earlier merger and axisymmetrization processes. This implies that the beta effect could be one of the forcings that shorten the lifetime of quasi-steady mesovortices in the eyewall of real TCs.

The concept of topology has dramatically expanded the landscape of magnetism, leading to the discovery of numerous magnetic textures with intriguing topological properties. A magnetic skyrmion is an emergent topological magnetic texture with a string-like structure in three dimensions and a disk-like structure in one and two dimensions. Skyrmions in zero dimensions have remained elusive owing to challenges from many competing orders. Herein, by integrating electron holography and micromagnetic simulations, we uncover the real-space magnetic configurations of a novel skyrmionic vortex structure confined in a B20-type FeGe tetrahedral nanoparticle. This texture shows excellent robustness against temperature without applying a magnetic field; an isolated skyrmionic vortex forms at the ground state. These findings shed light on zero-dimensional geometrical confinement as a route to engineer and manipulate individual skyrmionic metastructures.

PURPOSE Asymmetric dilated vortex vein (ADVV) observed in eyes with pachychoroid spectrum diseases is thought to be due to congestion of choroidal blood flow. The purpose of this study was to quantitatively investigate the blood flow velocity of ADVV using laser speckle flowgraphy (LSFG). STUDY DESIGN Retrospective case series. METHODS This was a retrospective case series with 23 eyes of 18 patients with ADVV on en-face OCT. A pair of choroidal veins from ADVV side (defined as ADVV vein) and non-ADVV side (defined as non-ADVV vein) was selected in each eye under the following criteria: (i) equivalent proximity to the deviated watershed, (ii) does not overlap with retinal blood vessels in the en-face OCT image, (iii) has approximately the same blood vessel diameter. Rubber bands were placed on the selected choroidal veins on the LSFG color map. Mean blur rate (MBR) values of ADVV and non-ADVV veins were statistically compared. RESULTS The average MBR was 10.11 ± 1.9 in the ADVV veins and 13.49 ± 6.2 in the non-ADVV veins, showing significantly lower values in the ADVV veins (P = 0.03). The blood vessel diameter of the ADVV was 10.26 ± 3.0 and in the non-ADVV veins, 10.63 ± 2.9 pixels; not significantly different (P = 0.66). The distance from the deviated watershed to the ADVV was 53.3 ± 24.8 and to the non-ADVV veins, 46.80 ± 20.3 pixels; not significantly different (P = 0.41). CONCLUSION In eyes with ADVV, the blood flow velocity in the ADVV veins was lower than in the non-ADVV veins, suggesting anatomical congestion of ADVV.

The interaction between an incident shock wave and a wavy end-wall in a three-dimensional geometry is numerically simulated by using a high-order finite-difference solver with a ghost-cell immersed boundary method. The aim is to discover the differences of the unsteady propagation characteristics of triple bifurcation points and transverse waves at different incident shock Mach numbers ( $$M_{1})$$ and wavy wall amplitudes ( $$A_{\mathrm{ww}}$$ ). For a benchmark case with $$M_{1}=1.5$$ and $$A_{\mathrm{ww}}=1$$ mm, the simulated results are in a good agreement with other studies, indicating the reliability of the current simulation technique. The numerical results at $$M_{1}=1.5$$ , 1.9, 2.5, and 3.5 show that the Mach numbers of the transverse shock waves issued from the triple bifurcation points decrease with time according to a power function. It indicates that the deformation of the shock wave attenuates with time and its flat shape is gradually recovered. The stronger the incident shock wave is, the faster the deformation decays. In the central region, a petal-like vortex structure is observed near the wavy wall and its advancing speed with periodic fluctuation correlates with the cycle of the transverse motion of the triple bifurcation point. With the increase of $$M_{1}$$ , the petal-like vortex gradually grows up in size, and a faster rate can be observed in the normal direction. By comparing the propagation characteristics of transverse waves at different wavy wall amplitudes, it is discovered that the cellular pattern becomes more diverse as the wall amplitude increases. This is due to the multiple collisions of the transverse waves on the wavy wall, which leads to the multi-modal waves system in the shocked gas.

In quantum fluids, the quantisation of circulation forbids the diffusion of a vortex swirling flow seen in classical viscous fluids. Yet, a quantum vortex accelerating in a superfluid may lose its energy into acoustic radiation, in a similar way an electric charge decelerates upon emitting photons. The dissipation of vortex energy underlies central problems in quantum hydrodynamics, such as the decay of quantum turbulence, highly relevant to systems as varied as neutron stars, superfluid helium and atomic condensates. A deep understanding of the elementary mechanisms behind irreversible vortex dynamics has been a goal for decades, but it is complicated by the shortage of conclusive experimental signatures. Here, we address this challenge by realising a programmable quantum vortex collider in a planar, homogeneous atomic Fermi superfluid with tunable inter-particle interactions. We create on-demand vortex configurations and monitor their evolution, taking advantage of the accessible time and length scales of our ultracold Fermi gas. Engineering collisions within and between vortex-antivortex pairs allows us to decouple relaxation of the vortex energy due to sound emission and interactions with normal fluid, i.e. mutual friction. We directly visualise how the annihilation of vortex dipoles radiates a sound pulse in the superfluid. Further, our few-vortex experiments extending across different superfluid regimes suggest that fermionic quasiparticles localised inside the vortex core contribute significantly to dissipation, opening the route to exploring new pathways for quantum turbulence decay, vortex by vortex., Comment: 7+9 pages, 4+7 figures

In this study, the vortex formed on the upstream of the frontal water intake structure in a dam lake was investigated by numerical modeling. Using the computational fluid dynamics method, vortex formation for different water levels was examined numerically. The purpose of this study is to prevent the formation of vortex, which can cause serious damage to the hydraulic structure. The water intake structure examined in the study has three units and rectangular shapes. The geometrical areas of each unit in the water intake structure are equal. The discharge and the distance between the side curtain walls were kept constant. The pressure at the inlet of the water intake structure has been changed depending on the height of the water level. The model scale of the water intake is 1/40. Froude model affinity was used as the model scale. In the numerical study, air intakes to the extent of serious damage to the structure and vortex formations have been observed. Visual simulations and analysis results of numerical models prepared and analyzed in FLOW-3D were examined in FlowSight. The first numerical models are based on examining the vortexes in the water intake structure, and the later numerical models are on the structures that prevent the vortexes in the water intake structure. Vortex formation in hydraulic structures is an undesirable physical phenomenon. Especially in dams with hydroelectric power plants, it causes serious damage to energy efficiency loss, water intake structure, shortening the service life of turbines and energy tunnels. Due to these problems, different anti-vortex structures were tested on the numerical model by CFD method in order to eliminate or reduce the negative forces from vortexes. Structures that block the tested vortex may allow to increase the operating water level in the dam reservoir. A new water intake structure model has been created for the solution of this hydraulic problem, which may cause great danger. Thanks to the new models created, it has been observed that air intake and vortex formations occur in a way that will cause less damage to the hydraulic structure in question.

The Western Tibetan Vortex (WTV) is a large-scale circulation pattern identified from year-to-year circulation variability, which was used to understand the causal mechanisms for slowdown of the glacier melting over the western Tibetan Plateau (TP). A recent argument has suggested the WTV is the set of wind field anomalies resulting from variability in near-surface air temperatures over the western TP (above 1500 m), which, in turn, is likely driven by the surface net radiation. This study thereby evaluates the above putative thermal-direct mechanism. By conducting numerical sensitivity experiments using a global atmospheric circulation model, SAMIL, we find a WTV-like structure cannot be generated from a surface thermal forcing imposed on the western TP. A thermally-direct circulation generated by the surface or near surface heating is expect to cause upward motions and a baroclinic structure above it. In contrast, downward motions and a quasi-barotropic are observed in the vertical structure of the WTV. Besides, we find variability of the surface net radiation (sum of the surface shortwave and longwave net radiation) over the western TP can be traced back to the WTV variability based on ERA5 data. The anticyclonic (cyclonic) WTV reduces (increases) the cloudiness through the anomalous downward (upward) motions, causes more (less) input shortwave net radiation and thereby more (less) surface net radiations, resulting in the warmer (cooler) surface and near-surface air temperature over the western TP. The argument is constructive in encouraging examination of the radiative balance processes that complements previous studies.

The vortex at the Ta/Fe explosively welded interface is featured by the intermediate zone being fully bounded by Ta matrix, which differs from the vortex structures observed in the most bimetallic interfaces. In this work, advanced characterizations and numerical simulations were integrated to establish a detailed evolution model of the special vortex, and the associated governing mechanisms were identified. It was also inferred that the mesoscale cavity and microcracks within the vortex resulted from the geometric hole and extrusion movement that generated during the vortex evolution, respectively. Furthermore, a diversity of metallurgical structure was revealed at the Ta/Fe interface, which did support the deformation path of the interface material observed in the simulations. The insights gathered here benefit an in-depth comprehension of impact welding.

In this paper, we consider the concentration property of solutions to the dispersive Ginzburg-Landau (or Gross-Pitaevskii) equation in three dimensions. On a spatial domain, it has long been conjectured that such a solution concentrates near some curve evolving according to the binormal curvature flow, and conversely, that a curve moving this way can be realized in a suitable sense by some solution to the dispersive Ginzburg-Landau equation. Some partial results are known with rather strong symmetry assumptions. Our main theorems here provide affirmative answer to both conjectures under certain small curvature assumption. The results are valid for small but fixed material parameter in the equation, in contrast to the general practice to take this parameter to its zero limit. The advantage is that we can retain precise description of the vortex filament structure. The results hold on a long but finite time interval, depending on the curvature assumption., Comment: 26 pp

Currently propeller boss cap fin (PBCF) and propeller duct are among the well-known energy saving devices (ESD) for their effectiveness in recovery of energy losses during practical operation. These two devises prominently reduce the hub vortex as well tip vortex and hence improve propeller efficiency. Combined study of PBCF and propeller duct has become important and is essential to observe their impact in propeller efficiency. Here, numerically the importance of duct angle of attack and duct position in a ducted propeller in the presence of PBCF has been investigated to improve the overall efficiency. Five different angles of attack (0°, 2.5°, 5°, 7.5°, 10°) with 2.5° interval and five different positions (0.1, 0.15 m before propeller, at the propeller, 0.1, 0.15 m after the propeller) of duct have been considered to investigate the overall efficiency in the presence of both ESDs. Reynolds Average Navier Stokes (RANS) equations are utilized for numerical simulation in moving reference frame (MRF) approach. The simulations reveal that a maximum improvement of 7.05% is obtained in propeller efficiency at 0° angle of attack and it proportionally reduces with the increase in angle of attack. It is also observed that duct placed before propeller produced a maximum enhancement in efficiency of about 9.86% in comparison with other duct positions. Variation of pressure coefficient, vortices, skin friction coefficient and turbulence kinetic energy are also studied in detail in order to have a better understanding about the flow behaviour.

This paper reports the experimental investigations of the wake of a rotating and translating sphere in the close proximity of a plane wall at moderate Reynolds numbers (Re = 450–2020, defined based on velocity of translation and diameter of the sphere) and for a non-dimensional rotation rate, Ω* (ratio of surface velocity to the translation velocity of the sphere), of 1. For the current gap (h)-to-diameter (d) ratio of the sphere (h/d = 1/16), at Re = 1000, hairpin vortices shed in the wake where looping of small-scale vortices increases with the increase in Re. At Re > 1000, the transition from hairpin type to shear layer vortex shedding occurs. At a relatively high Reynolds number (Re = 1130), the separated vortex sheets from both sides of the sphere exhibit Kelvin–Helmholtz instability, and the wake shows multiple vortical structures. At Re = 2020, a strong interaction of vortex rings in the wake of the sphere and boundary layer at plane wall results in the breakdown of larger vortical structures into smaller scales. The separation angle changes from the equatorial region to the pole of the sphere because of differential rotational speeds at other planes. At midplane, the separation angle increases with Re, and it decreases again when hairpin–shear layer vortex shedding transition occurs. The Strouhal number as a function of Re indicates the presence of dual frequency beyond this transition.

Laboratory experiments were performed to characterize the distinct features of hairpin-like vortical structures induced via pulsed, wall-normal jets in laminar (LBL), and turbulent boundary layers (TBLs). Hotwire anemometry was used to characterize the disturbed flow at multiple streamwise, transverse, and vertical locations. The dominant spatiotemporal structure of the induced motions was reconstructed using Taylor’s hypothesis and time-averaged, phase-locked data. Results support the concept that the meandering of very-long, low-momentum streaks observed in the logarithmic layer and lower part of wake regions of TBLs results from the upwash of hairpin vortices or packets. Comparing the induced hairpin-like vortices in the LBL and TBL reveals the modulation of the mean shear; using the second-order derivative of the mean streamwise velocity, we show a linkage between the mean shear gradient and appearance of low- and high-momentum streaks in the logarithmic layer. Streamwise velocity profiles with a pitot tube by Smith (Effect of Reynolds number on the structure of turbulent boundary layers, 1994) at ten Reynolds numbers from Reθ = 4601 to 13,189 are also inspected to evaluate such linkage in a broader range of Re. As Reynolds number increased, the vertical regions of the negative second derivative of mean streamwise velocity increased. The minimum value of mean shear gradient decreased, indicating that the mean shear stress gradient increased to form more noticeable low- and high-momentum streaks in the logarithmic layer. Besides, the Reynolds tensor’s principal stresses and principal axes angles associated with the hairpin vortex legs stretching are demonstrated by DNS data (Spalart, P. R. 1988) as Reynolds number increased.

Features of the simulation of the thermodynamic and gasdynamic processes occurring in devices for reducing the noise level of a shot from a gun were considered. A simulation of large vortices in the nonstationary turbulent flow of powder gases in a muzzle noise reduction device with a silencer representing a shaped channel with several chambers, whose volumes decrease in the direction to the silencer outlet, has been performed. Results of qualitative and quantitative investigations of the initiation, development, and damping of the shock waves in the flow of powder gases, formed as a result of the firing of a shot made from a signal gun, are presented.

The present paper numerically investigates viscoelastic fluid flow in the developing flow regime through both straight and 90-degree curve ducts. The aim is to investigate the effects of the first and second normal-stress differences (N1 and N2) as well as the curvature ratio ( $$\kappa = D/R$$ , where R and D are the curvature radius and channel side, respectively) and Reynolds number on the secondary flow patterns. Simulations were carried out in developing flow conditions in curved ducts using the finite volume method. The Reynolds numbers were 10, 20, 30, 40, 50, and 100, and the curvature ratios were 0.05, 0.066, 0.1, and 0.2. The Giesekus constitutive equation was utilized to model the non-linear rheological behavior of a 5.0 wt.% solution of polyisobutylene (PIB) in tetradecane (C14H30). The results reveal that a secondary flow with eight corner vortices is generated in a fully developed flow of viscoelastic fluid through a straight duct. This behavior is attributed to the difference in the second normal stress in the flow field. The results of the current study confirm that the second normal stress difference and change in the sign of N2 around the cross section’s corners trigger these corner vortices. Furthermore, the effects of the curvature ratio on the distributions of first and second normal-stress differences in the developing Dean flow were studied for the first time. The vorticity vector method was used for mixing-enhancement assessment. The results show that the intensity of secondary flows was significantly higher in viscoelastic fluid at all curvature ratios and at all considered Reynolds numbers than in Newtonian fluid flow.

Experimental and numerical study of active and passive flow control are notable and highly practical subjects in aircraft and missiles. Fluid jets are invaluable tools for this purpose. Accordingly, the present study delves into the effects of a pair of air microjets on turbulent flow over a plate. For this purpose, numerical model results were verified by experimental data of flow over a plate in the presence of a pair of air jets. Next, vortex formation, merging, and dissipation into the flow were studied at velocity ratio, VR = 4.0, by changing the spacing between the pair of jets and their orientations. The vortex position relative to the floor and other vortices, vortex intensity, flow velocity, Reynolds stresses in different directions, and pressure are discussed. The best vortex-merging results were found in a pair of co-directional jets (d/D = 10) condition. A pair of co-directional jets (d/D = 10) produced better results than opposite ones (d/D = 10—ccr). In the configuration with d/D = 10, the vortex intensity was nearly 80% higher than that of the single jet case. Further, the pair of jets pushed the post-jet pressure rise around 30 cm away.

This study aimed to examine the integrity of two-cavity sand casting products in relation to the angular orientation of gating design. Two angular orientations of 60° and 45° were investigated experimentally and numerically and compared with the efficiency of a 90° gating system. The FLOW three-dimensional (3D) simulation was conducted to detect smooth filling and describe the pattern of molten aluminium LM4 (Al–Si5Cu3) alloy flow. From the results obtained, the turbulent flow was observed with vortex, which created a larger surface gap to allow air entrapment in molten metal. For both instances, casting discontinuities such as blow holes, pin holes, sponge shrinkage, sand inclusions, and dross were observed on the cut 2 mm machined surfaces of the moulded components with various degrees of intensity. Visual analysis, optical microscopy, ultrasonic and X-ray measurements were conducted to check the accuracy of the experimental components. All the defect detection methods depicted the fewest manufacturing defects with 45° angular orientation, which was attributed to uninterrupted flow of molten metal and low backflow strain. The component with 90° exhibited significant defects due to turbulent flow, entrapment of air bubbles, lack of mould filling, and uneven solidification. These factors consequently caused irregular cracks in the material. Therefore, practically, 45° angular orientation of gating design with two-cavity mould set-up is hereby recommended for optimum/best quality sand casting of aluminium LM4 (Al–Si5Cu3) alloy components, as required in many manufacturing companies.

A comprehensive dynamics simulation has been presented in a quad-beam optic fiber with intersection arrangement. As the offset distance changes, the motion type of dielectric micro-particle could transform from trapping to orbital rotation. Finally, they would be repelled far away from the trapping center due to weak centripetal forces. Different from dual-beam optic fiber configuration, this intersection arrangement has much stronger trapping force to attract the suspending particles. Moreover, the cross optical trapping having misalignment could generate a vortex field with symmetric characteristics, which cause the particles carrying out circular orbital movement. This novel optic fiber arrangement is conducive to the application of particle manipulation and provides more technical support in integrated microfluidic chip.

We investigate the characteristics of a dust-devil-like vortex (DDLV) observed using thermal image velocimetry (TIV) at a sports ground in Tokyo. Thermal image velocimetry provides unique observations of the two-dimensional velocity distribution for a DDLV with high spatio–temporal resolution (i.e., tens of cm s−1) near the ground. Two DDLVs were detected, one each in summer and winter, and the quantitative features of the larger, stronger DDLV in the winter are examined. The size and strength of the detected DDLV, which are quantified using TIV, are within the ranges reported in past observations and numerical simulations of dust devils. The vortex appears at the boundary of a cold-air current near a 55-m building wall, and persists for more than 3 min.

The buoyancy-driven thermogravitational Rayleigh–Benard convection (RBC) occurs in a 1–3 cm-deep layer of normal He-I in a wide experimental cell heated from above at temperatures below the liquid 4He density maximum T

The Monte Carlo method has been used to calculate the trapped magnetic field in superconducting plates with holes. The mechanism of flux pinning on the holes is implemented with special subprocesses added to the algorithm: vortex capture and emission, both occurring on the hole boundaries. Secondary peaks related to the holes emerge on the calculated profiles of the trapped magnetic field. It has been found that these peaks disappear in plates with sufficiently strong pinning or when the computational mesh is coarse (the case corresponding to a low resolution of probes in experiments). The dependence of the trapped field on the hole radius has been analyzed.

To understand fundamental problems in hypersonic laminar-turbulent boundary layer transition for three-dimensional complex vehicles, a new standard model with typical lifting-body features has been proposed, named as hypersonic transition research vehicle (HyTRV). The configuration of HyTRV is fully analytical, and details of the design process are discussed in this study. The transition characteristics for HyTRV are investigated using three combined methods, i.e., theoretical analyses, numerical simulations, and wind tunnel experiments. Results show that the fully analytic parameterization design of HyTRV can satisfy the model simplification requirements from both numerical simulations and wind tunnel experiments. Meanwhile, the flow field of HyTRV reveals typical transition mechanisms in six relatively separated regions, including the streamwise vortex instability, crossflow instability, secondary instability, and attachment-line instability. Therefore, the proposed HyTRV model is valuable for fundamental researches in hypersonic boundary layer transition. A new standard model with typical lifting-body features for boundary layer transition research has been proposed. Results of three combined analysis methods show that the flow field of HyTRV reveals typical transition mechanisms in six relatively separated regions, including the streamwise vortex instability, crossflow instability, secondary instability, attachment-line instability. Therefore, the proposed HyTRV model is valuable for fundamental researches in hypersonic boundary layer transition.

CEAS Aeronautical Journal 13, 97-112 (2022). doi:10.1007/s13272-021-00555-1, Published by Springer, Wien [u.a.]

Foam sclerotherapy is a simple and easy minimally invasive treatment for varicose veins, but foam stability is a bottleneck in the treatment. The foam-coalescence pattern can reveal the process of foam decay, whereas the effects of fluid parameters can characterize the decay patterns under various conditions. This study is instructive for clinical and research purposes. Four liquid parameters were considered by the addition of surfactant P-188 to change the liquid properties. A simplified four-foam basic unit model was developed. Two-phase flow calculations were performed in ANSYSA Fluent with grid-independence verification, and post-processing was performed using Tecplot 360. As the concentration of P-188 increased from 0 to 12%, the foam-coalescence time gradually increased from 0.28 to 0.35 ms at a growth rate of approximately 25%. The coalescence of the unit foam group of the four foams finally approached a spherical shape. The first consolidation consumed 0.03 ~ 0.05 ms, and the velocity increased sharply to 1.0 ~ 1.2 m/s in the second consolidation. The greater the concentration of P-188, the later the peak appeared. A simplified spatially stereoscopic coalescence model was developed, and the foam-coalescence time was found to increase linearly with increase in the surfactant concentration. It was revealed that foam coalescences under different conditions mainly included the coalescence proximity effect of the pressure gradient field and the repulsion effect of the vortex on the bubble surface. This paper serves as a basis for the design of more macroscopic foam-stability experiments and paves the way for ideas achieving the stability of sclerosing foam.

In the present study, numerical simulations of the pressure-sensitive paint (PSP) rotor in hover were conducted using a Reynolds-averaged Navier–Stokes computational fluid dynamics (CFD) flow solver based on unstructured mixed meshes. In the simulations, an improved laminar-turbulent transition model $$\gamma - {\text{Re}}_{{\vartheta t}} - {\text{CF}}^{ + }$$ was adopted for the prediction of laminar-turbulent onset phenomena involving crossflow-induced transition and flow separation. To capture vortices with high resolution, an improved scheme ESWENO-P was utilized for computing inviscid fluxes on Cartesian meshes. The predicted results such as transition onset locations and rotor aerodynamic performances in terms of thrust coefficient, torque coefficient, and figure of merit were compared with the experimental data. The effects of the fuselage and facility wall on PSP rotor performance in hover were also investigated.

The flutter of thin elastic plates (sheets) in a fluid flow is an interesting nonlinear problem, as well as an important engineering problem, because the sheets are used in many industrial applications. A detailed understanding of flutter characteristics and sustaining mechanism of limit cycle oscillation (LCO) is important to suppress the flutter. In this study, a nonlinear analysis on a LCO of rectangular sheets in a three-dimensional uniform fluid flow using the nonlinear beam model and vortex-lattice method is performed. The influence of the vortex element model of the vortex-lattice method on the post-critical behavior is investigated in detail. Moreover, fluid–structure interaction simulations are performed using computational fluid dynamics and computational structural dynamics to examine the flow field and pressure distributions acting on a sheet surface in detail. It is found that flow separation around the side edges of a fluttering sheet can affect the post-critical behavior.

Numerical study was carried out in order to investigate thermo-hydraulic performance and flow characteristics of rectangular channel fitted with the novel type conic vortex generator [NTCVG] in the range of Re = 5000–20,000 with an increment of Re = 2500. To evaluate the NTCVG’s effect on heat transfer augmentation, three-dimensional [3D] turbulent flow was analyzed by using the shear-stress transport (SST) k-ω turbulence model. The numerical results revealed that NTCVG was detected to be capable of generating two primary vortices along with four corner vortices for each vortex generator [VG]. NTCVG was compared in terms of TEF with other VGs studied either numerically or experimentally in literature. Due to its curved surface, NTCVG was compared not only with flat surfaced VGs but also with inclined, curved as well as perforated surfaced VGs for the purpose of providing comprehensive comparison. Based on numerical results, NTCVG showed superior performance in comparison to VGs investigated in literature. In terms of heat transfer augmentation, NTCVG manipulates incoming air to the heated surface by its aerodynamically designed shape. The superiority of NTCVG with regard to heat transfer enhancement was exhibited with the use of flow field, temperature and Nu number distribution. DWPC, which performs relatively well in improving heat transfer, was considered for an example of comparison. While both LVGs were determined to be exhibited close f values, an increase in Nu number was attained on the order of 58.75% and 41.05% for NTCVG and DWPC, respectively, in comparison to smooth channel at the lowest Re number. NTCVG showed not only at the rate of 8.42% higher TEF value than DWPC, but also the second highest TEF value [TEFNTCVG = 1.33] was attained among all other VGs compared.

In this study, a validated CFD model is used to analyze the flow field and pollutant distribution in an isolated canyon (street aspect ratio, W/H = 1) by considering different street categories and arrangements of void deck under a perpendicular inflow wind. The results reveal that the street geometry affects significantly the in-canyon flow structures and thus the pollutant distributions. Comparing with the regular street canyon (a main clockwise vortex is obtained therein), the void deck can cause several vortices when a strong stream of air passes through the canyon. It is the most conducive to pollutant removal for the void decks at both buildings, while the construction with void deck at the upstream building causes pollutant accumulation on the windward side. Moreover, a larger high-pollution zone is generated above the elevated road due to the wind recirculation therein, and for the two-level street and the street with depressed road, the weak wind leads to the accumulation of traffic pollutants in the underground space. This study will provide technical support for urban street planning and design to alleviate traffic pollution.

The side-blown vortex smelting reduction reactor proposed in this paper is a new type of metal extraction equipment. The study of fluid dynamics is significant for improving reactor performance. Physical simulation is used to analyze the effects of the angle and number of blown lances, nozzle diameter, gas flow rate, and measuring depths on the reactor’s transfer and mixing characteristics. Dimensional analysis is used to correlate dimensionless numbers (Reynolds number Re, modified Froude number Fr′, capillary number Ca, number of blown lances n, and horizontal angle of the blown lance α) with mixing time and multiphase flow behavior. The results show that when the nozzle diameter and the number of blown lances are constant, Fr′, Ca and α are negatively correlated with the mixing time, and Re is positively correlated with the mixing time. When the angle of the blown lance is constant, Re and Ca are negatively correlated with mixing time, and Fr′ is positively correlated with mixing time. With the increase of Re, Fr′, Ca, the mixing behavior will gradually change from the bubbling regime to the transition regime and then to the steady jetting regime.

In order to study the fluid–solid coupling dynamic characteristics of parachute-payload system during drop process and analyze the unsteady aerodynamic characteristics under finite mass opening conditions, an adaptive moving fluid mesh method is developed on the basis of the existing arbitrary Lagrangian–Eulerian (ALE) fluid–solid coupling method. The calculation results of open force and drop velocity on the C-9 parachute demonstrate the effectiveness of this method. On this basis, the effect of canopies with three different permeability on parachute-payload system motion characteristic including opening property, steady descent property and stability is studied. Comparative analysis is conducted for structures and characteristics of vortex with different canopy materials, and interference mechanism of unsteady flow for parachute-payload system in unsteady oscillation is revealed. The results show that the adaptive moving fluid mesh method can effectively eliminate restrictions of existing simulation methods for parachute-payload system and significantly reduce calculation time. For the lightweight parachute, permeability has significant effect on kinetic characteristic of parachute-payload system. Canopy with large permeability has small opening load and structural stress in opening stage. After opening, there are mainly small vortexes distributed evenly behind the canopy with good stability. However, canopy with small permeability has obvious breath behavior and oscillation in opening stage. The main vortexes periodically shed off after opening. With the change of permeability from small to large, Parachute-payload system eventually presents three steady descent modes: conical descent, gliding descent and stable vertical descent. Graphical abstract

This study presents a computational investigation of a flapping wing executing to and from horizontal motion with a fixed angle of attack or pitch orientation. The computational results compare well with the experimental results of Lua et al. (Exp Fluids 51(1):177–195, 2011). An attempt has been made to understand the effect of flapping frequency (f), Reynolds number (Re) and angle of attack ( $$\alpha$$ ) on flow features like vortex structures and wing–wake interaction. The present study is conducted for five different flapping frequencies, namely, f = 0.021, 0.21, 0.315, 0.42 and 2.1 Hz, four different chord-based Reynolds numbers, namely Re = 2000, 5000, 10,000 and 50,000 and two different angles of attack, namely $$\alpha = 45^{\circ }$$ and $$\alpha = 60^{\circ }$$ . Vorticity contours display variation of vortex structures with change in flapping frequency. The temporal history of resultant force coefficients show distinct characteristics like amplitude modulation, linear growth and decay, inflexional behavior, dual peak behavior, etc. Frequency spectrum of the lift coefficient reveals that the flapping frequency is most dominant and it is accompanied by several harmonics. At higher Reynolds number, the spectrum displays broadband character. The power content of the dominant frequency increases with increase in flapping frequency and decreases with increase in angle of attack. A short investigation on the effect of three-dimensionality of the flow is also presented in this study. Additionally, three-dimensional eddy resolving simulations were performed with IDDES.

Experimental investigations are presented on the characterization of flow turbulence and velocity fields around circular piers placed in isolated, tandem, and staggered arrangements in a rigid bed channel with identical flow conditions. Instantaneous velocity measurements are undertaken using a 16 MHz micro down-looking Acoustic Doppler Velocimeter (ADV) at different grid points along the flow depth. The streamline pattern obtained from the velocity fields is presented on vertical planes around the piers. Further, the resultant contours of vortices are plotted for all three types of arrangements, i.e., isolated, tandem, and staggered arrangements, to understand the strength of the vortices around the piers. Apart from the above investigations, the turbulence characteristics such as turbulence intensities, turbulent kinetic energy, velocity power spectra and Reynolds shear stresses at different planes are also presented for all three configurations of piers. The turbulence characteristics are used to identify the influence of one pier over others in the tandem and staggered arrangements compared to that of the isolated piers. The horseshoe vortex system, quantified by its vorticity and strength, is found to be predominant in the staggered configuration. A horseshoe vortex is formed at 0.36d, 0.9d and 0.35d (d is the diameter of the pier) upstream of the isolated pier, front piers of the tandem and front piers of the staggered case, respectively. A zone of recirculation is formed just upstream of the rear pier in the tandem case. The Reynolds shear stresses near the bed, turbulent kinetic energy and turbulence intensities are also found to be quite significant downstream of the front pier in the staggered arrangement compared to those in the isolated and tandem arrangements. The turbulent kinetic energy at the mid-flow depth is found to be 2.5 times higher than that near the bed. The velocity power spectra reveals that the strength of wake vortices is 2.5 times greater for the front piers of the staggered case than that of the tandem front piers with Strouhal numbers, $${S}_{t}$$ = 0.26 and 0.112 for the staggered and tandem cases, respectively, near the bed. The present study enhances the understanding of the flow structure around isolated, tandem and staggered bridge piers.

To evaluate the influence of axial clearance on the performance characteristics in turbopumps, numerical simulations of an entire flow passage were carried out. The simulations were validated by performance characteristic experiments. The progress of the reciprocating axial movement in the rotor between the front and back covers was disassembled into five fixed clearances groups. Hump characteristic occurs at the same flow rate under these clearances groups. The hydraulic loss of the inducer-impeller was clearly influenced by the clearances. In particular, the hydraulic loss of the impeller changes significantly at the low flow rate under the ±0.3 mm clearance. With the increase of the flow rate, the effect of the clearance change on the flow is weakened. An innovative entropy production analysis was also performed. The distribution of the high local entropy production rate at the impeller inlet under the 0 mm clearance and at the impeller outlet under the −0.15 mm and −0.3 mm clearances overlapped with the vortex caused by flow separation, and the counterpart at the back cover is concentrated around the clearance structures, thereby leading to high hydraulic loss.

Recently, domestic gas turbines are primarily operated under partial loads. Hence, thermal expansion of components decreases, leading to a discontinuity between the 1st blade and 2nd vane. In this study, the local heat transfer coefficients are derived using the naphthalene sublimation method to analyze thermal characteristics based on step height, and flow characteristics are analyzed using numerical simulation. An extreme heat load of the flat endwall appears around the leading edge of the vane due to the secondary vortex. Under the step conditions, the heat load increases in the upstream region as the main flow near the endwall is reattached to the endwall surface. In addition, two high heat transfer distributions appear due to the recirculation flow, and a step-induced vortex is formed. As the step-induced vortex moves to the suction side within the vane flow path, a high thermal load appears in the corresponding region. Consequently, we found that the occurrence of a step causes severe thermal damage in the upstream region of the vane endwall. The area-averaged heat transfer of the stepped endwall is increased by about 10.6 % and 17.3 % at hs/Cx = 0.05 and 0.1, respectively, as compared to that of the flat endwall.

Experiments and three-dimensional numerical computations are performed to investigate the air-oil intermittent two-phase flow in a horizontal pipe for different air and oil flow rates. The numerical predictions of pressure drop and flow structure are compared with the experimental results to validate the numerical model. At a higher airflow rate, regardless of the oil flow rate, a mixing vortex formed by the velocity difference between the liquid film and liquid slug causes smaller bubbles to detach from the elongated bubble and disperse into the flow. The eddy viscosity ratio in the elongated bubble unit, which is challenging to measure by the experimental method, is numerically calculated to infer the mixing vortex and verify interfacial turbulence dampening in the air-oil intermittent flow regime. Due to surface tension, the eddy viscosity ratio is completely suppressed at the air-oil interface signifying the interfacial turbulence dampening in the air-oil intermittent flow regime.

Pumped storage units are the main parts in China’s power construction, as a hot issue concerned by the industry. The pump turbine involves the two-way flows and a multiple condition operation, and its operation flow pattern is very complex. The particle image velocimetry (PIV) is a very effective test technique to determine the internal flow field of pump turbines. This paper discusses the key problems of the pump turbine, based on the PIV experiments under typical conditions of the pump turbine, especially for problems such as the S-shape problem, the hump problem, the pressure fluctuation problem and the cavitation problem. In the internal flow fields under typical conditions are determined. The vortices induced and their development are observed in the PIV test. The flow phenomenon is shown at each operating point. The typical problems of the pump turbine are closely related to the vortex distribution in the internal flow field. From the PIV test results under several working conditions and from the comparisons between the optimal condition and the part load condition, it is seen that the vortex distributions are very different. Vortices at the vane-less area between the guide vane and the runner are closely related to the strong pressure pulsation, the first hump and the S-shape curve. From the PIV results of the cavitation working points, it is seen that the flow angle is changed in the vane-less region and the runner leading edge because of the cavitation bubbles and that the flow angle deviates from the optimal setting angle. From the computational fluid dynamics (CFD) result of the second hump working points, it is concluded that the vortex shedding on the runner leading edge is the main cause of the second hump.

Numerous studies suggest that disturbed shear, causing endothelium dysfunction, can be related to neighboring vortex structures. With this motivation, this study presents a methodology to characterize the vortex structures. Precisely, we use mapping and characterization of vortex structures' changes to relate it with the hemodynamic indicators of disturbed shear. Topological features of vortex core lines (VCLs) are used to quantify the changes in vortex structures. We use the Sujudi-Haimes algorithm to extract the VCLs from the flow simulation results. The idea of relating vortex structures with disturbed shear is demonstrated for cerebral arteries with aneurysms virtually treated by inserting foam in the sac. To get physiologically realistic flow fields, we simulate blood flow in two patient-specific geometries before and after foam insertion, with realistic velocity waveform imposed at the inlet, using the Carreau-Yashuda model to mimic the shear-thinning behavior. With homogenous porous medium assumption, flow through the foam is modeled using the Forcheimmer-Brinkmann extended Darcy model. Results show that foam insertion increases the number of VCLs in the parent lumen. The average length of VCL increases by 168.9% and 55.6% in both geometries. For both geometries under consideration, results demonstrate that the region with increased disturbed shear lies in the same arterial segment exhibiting an increase in the number of oblique VCLs. Based on the findings, we conjecture that an increase in oblique VCLs is related to increased disturbed shear at the neighboring portion of the arterial wall., 36 pages, 10 figures, 3 tables, submitted to Physical and Engineering Sciences in Medicine

We report upon synthesis of stable chains of magnetically aligned zero-valent α-Fe nanoparticles and investigation of their magnetization reversal mechanism. The magnetic hysteresis loops with magnetic field applied at various directions with respect to the nanoparticle chain are measured experimentally and reproduced numerically by precisely mimicking the sample geometry under finite element modeling. The magnetization reversal mechanism is visualized in all three dimensions (3Ds) using 3D simulation and visualization toolkits. The reversal is found to nucleate from the ends of the chains and progressed through curling and fanning modes, vortex nucleation, propagation and annihilation. A better quantitative agreement is observed for increased number of nanoparticles and parallel chains.

The 2 kW Gravitational Vortex Hydro Power Plant (GVHPP) system was designed, installed and evaluated. The plant consisted of a unique prefabricated circular intake basin and a closed tailrace conduit. The head and flow of the installed plant was 1.73 m and 0.093 m3/s, respectively. The average plant efficiency and generated power output were found to be 49.36% and 477.24 W, respectively. Though the result is well below the expected power output, it correlates well with studies for similar technology. The power was generated by the combined effect of the vortex generated by the circular basin as well as the pressure due to the restricted passage of flow by gravity in the closed tailrace. The report analysed the performance of the GVHPP system and suggested ways by which the output and efficiency can be maximised. The report suggests that cost-effective decentralised small-scale projects are more feasible in the rural communities rather than expensive and complex grid network that cannot be sustained.

To investigate the nozzle geometry influence on vortex cooling performance in the actual leading edge region, an improved vortex cooling configuration with a coolant chamber is established based on the middle cross section of stage 1 vane blade of GE-E3 high pressure gas turbine. Numerical simulations are conducted to research the effects of nozzle position, nozzle number and nozzle aspect ratio on the flow and heat transfer behavior. Results show that with the introduction of the coolant chamber, the mass flow of nozzles increases gradually from the upstream to the downstream instead of a uniform mass flow distribution. Configurations with nozzles placed at the sides (the vortex cooling) have better cooling performance than with nozzles placed in the middle (the impingement cooling). What’s more, the configuration with nozzles placed along the pressure side has the best comprehensive cooling performance. Due to the irregular blade line, a flow entrainment that is not found in simplified circular configurations is observed on the pressure side weakening the local heat transfer performance. The cooling performance is most sensitive to the nozzle number. As the nozzle number increases, the friction coefficient and heat transfer intensity both decrease. Moreover, as the nozzle aspect ratio increases, the friction coefficient and heat transfer intensity both increases first and then decrease. Results indicate a certain vortex cooling configuration may have the optimal nozzle number and nozzle aspect ratio. For this paper’s configuration, the best nozzle number is 5 and the best nozzle aspect ratio is 4.

The impact of the human nasal airway complexity on the pharyngeal airway fluid mechanics is investigated at inspiration. It is the aim to find a suitable degree of geometrical reduction that allows for an efficient segmentation of the human airways from cone-beam computed tomography images. The flow physics is simulated by a lattice Boltzmann method on high-performance computers. For two patients, the flow field through the complete upper airway is compared to results obtained from three surface variants with continuously decreasing complexity. The most complex reduced airway model includes the middle and inferior turbinates, while the moderate model only features the inferior turbinates. In the simplest model, a pipe-like artificial structure is attached to the airway. For each model, the averaged pressure is computed at different cross sections. Furthermore, the flow fields are investigated by means of averaged velocity magnitudes, in-plane velocity vectors, and streamlines. By analyzing the averaged pressure loss from the nostrils to each cross section, it is found that only the most complex reduced models are capable of approximating the pressure distribution from the original geometries. In the moderate models, the geometry reductions lead to overpredictions of the pressure loss in the pharynx. Attaching a pipe-like structure leads to a higher deceleration of the incoming flow and underpredicted pressure losses and velocities, especially in the upper part of the pharynx. Dean-like vortices are observed in the moderate and pipe-like models, since their shape comes close to a $$90^\circ$$ -bend elbow pipe.

The dissipation of the energy of high-speed flows in vortex spillway structures is considered. The operation of existing hydraulic projects with vortex spillways is analyzed. Laboratory tests of a vortex spillway for the conditions of the Telmama HPP were conducted.

A low-dimensional model of a top-tensioned riser under excitations from vortices and time-varying tension is proposed, where the van der Pol wake oscillator is used to simulate the loading caused by the vortex shedding. The governing partial differential equations describing the fluid–structure interactions are formulated and multi-mode approximations are obtained using the Galerkin projection method. The one mode approximation is applied in this study and two different resonances are investigated by employing the method of multiple scales. They are the 1:1 internal resonance between the structure and wake oscillator (also known as ‘lock-in’ phenomenon) and the combined 1:1 internal and 1:2 parametric resonances. Bifurcations under the varying nondimensional shedding frequency for different mass–damping parameters are investigated and the results of multiple-scale analysis are compared with direct numerical simulations. Analytical responses are calculated using the continuation method and their stability is determined by examining the eigenvalues of the corresponding characteristic equations. Effects of the system parameters including the amplitude of the tension variation, vortex shedding frequency and mass–damping parameter on the system bifurcations have been investigated. The analytical approach has allowed to probe bifurcations occurring in the system and to identify stable and unstable responses. It is shown that the combined resonances can induce large-amplitude vibration of the structure. Counter-intuitively, the amplitude of such responses increases rapidly as the amplitude of the tension variation grows. Comparisons between the analytical and numerical results confirm that the span of the system vibration can be accurately predicted analytically with respect to the obtained response amplitudes of responses. The proposed multi-mode approximation and presented findings of this study can be used to enhance design process of top tension risers.

The authors have performed 3D numerical investigations into the velocity field behind a 3D thin plate by the LES method. The plate was located at a height of 0.002 m in a turbulent boundary layer formed in a water channel. The chord length of the plate and its spanwise size were equal to 0.01 m and 0.024 m respectively. The Reynolds number calculated from the half-width of the channel and the velocity on its axis was equal to 7500. It has been shown that under the impact of the wake of the plate, the longitudinal velocity normalized to the stagnation velocity grew in the logarithmic region at a distance to x/δ = 3.8, and pulsations of all the velocity components decreased in the buffer region to the distance x/δ = 0.8. As the lower shear layer of the wake approached the surface, longitudinal pulsations reached their minima at the wall at x/δ = 1.8, whereas vertical and transverse pulsations became higher than those in an unperturbed boundary layer. The calculated characteristics of the velocity field satisfactorily correlated with the relevant characteristics obtained in experimental investigation with similar initial and boundary conditions. An analysis of the velocity fi eld has revealed the mechanism of impact of the wake on the structural change of wall flow. The involvement of the wall medium in the lower shear layer generated the outflow of the medium from the channel wall, and the involvement in the upper shear layer formed the inflow of a high-speed medium to the buffer region. The medium′soutflow from the wall led to a reduction in the velocity gradient at the surface. Shear stresses decreased at a distance of four thicknesses of the boundary layer, and their local reduction amounted to as much as ~30%. Trailing vortices descending from the plate′s side edges created a nonuniform transverse-velocity distribution. This nonuniformity caused the vorticity to form in the buffer region. The arising system of small-size vortices blocked the feed of the high-speed medium to the wall, retarding the growth in the shear stresses on the surface in the interval 1.4 ≤ x/δ ≤ 2.6. The vortex system degenerated upon the stabilization of the transverse velocity and shear flow on the surface was restored.

This study was to evaluate the effects of ischemic mitral regurgitation (IMR) on vortex formation and leaflet dynamics using an established porcine infarct model of IMR. Using direct coronary ligation, five animals were subjected to a posterolateral myocardial infarction (MI) followed by an MRI at 12-weeks post MI. MR imaging consisted of 4D time-resolved left ventricular (LV) flow, full coverage 2D LV cine, and high resolution 2D cine of mitral valve dynamics. Five additional naive animals underwent identical imaging protocols to serve as controls. Image analysis was performed to obtain mitral transvalvular flows as well as LV volumes throughout the cardiac cycle. In addition, anterior to posterior mid-leaflet tip distances were measured throughout the cardiac cycle for determination of temporal leaflet dynamics. It was found IMR caused asymmetric vortex ring formation with the anterior vortex having a lower vorticity relative to its posterior counterpart. In contrast, normal ventricles create symmetric and tightly curled vortices in the basal chamber just underneath the mitral leaflets which conserve kinetic energy and aid in effective ejection. IMR animals were also evaluated for leaflet separation and were found to have a greater leaflet opening and achieved peak vorticity and peak leaflet opening later than control animals. In conclusion, this study shows the effects that altered vortex formation, due to IMR, can have on ventricular filling and leaflet dynamics. These findings have important implications for understanding blood flow through the dilated heart and how ring annuloplasty and volume reduction interventions may influence mitral valve dynamics.

In this paper, an experiment of a robotic model at Reynolds number of approximately 240 is performed with the aim of establishing a scaling law for describing the circulation growth of the leading-edge vortex (LEV) on a flapping wing. Three typical modes of wing rotation, i.e., advanced, symmetric, and delayed modes, are considered to examine the effects of wing rotation on the scaling formation of LEV. The streamwise velocity fields of the LEV along the span of the wing are measured by particle image velocimetry technique. Experimental results demonstrated that a spirally three dimensional (3D) LEV with spanwise distribution of circulation rolls up on the upper surface of wing and the circulation of LEV usually obtains the peak before the end of wing stroke. Based on the concept of vortex formation time, the formation time of the 3D LEV are defined in two distinct manners. One (denoted by $$T_{\text {LEV}}^*$$ ) is defined based on the LEV circulation, and the other (denoted by $$T_{\text {LEV}}^{**}$$ ) is defined based on the wing kinematics. It is found that $$T_{\text {LEV}}^{**}$$ increases monotonously during the upstroke and downstroke, whereas $$T_{\text {LEV}}^*$$ generally arrives peaks and then decreases. The peak value of $$T_{\text {LEV}}^*$$ indicates the formation number of LEV, which stays in the range of 2.5–5.5, agrees with the scaling formation number predicted by other vortices. Moreover, the mode of wing rotation plays a controllable role in the formation number of LEV by modulating the characteristic length scale that feeds the formation of LEV. After reaching the formation number, the LEVs stably remain attached on the flapping wing and even further grow at some spanwise locations because of vorticity transport. Furthermore, the linear relationship between $$T_{\text {LEV}}^*$$ and $$T_{\text {LEV}}^{**}$$ before reaching the formation number can suggest a potential model for predicting the circulation growth of LEV based on wing kinematics.

A series of Direct Numerical Simulations (DNS) at low Reynolds number is performed to investigate the flow and the heat transfer in ducts with complex geometry, which are frequently encountered in many engineering fields, especially in aeronautics. A finite-difference approach and the immersed-boundary method are adopted to solve the governing equations in the computational domain. The flow and heat transfer phenomena in a circular pipe are studied in detail for laminar and turbulent regimes; thus the code is validated through a comparison of present DNS results with those provided by some trusted references. Straight ducts with regular polygonal cross sections represent the first type of ducts with complex geometry analyzed in this paper. The behavior of the pumping power expenditure is studied when the number of polygonal sides changes. The secondary motions are then investigated, and their effects on the mean velocity and temperature contours are studied. The shapes of vortices in secondary motions are compared with those provided by an analytical approach, which is based on the eigenfunctions of the Laplacian operator. Also the geometries pioneeringly studied by Nikuradse in 1930 are taken into account.

The mathematical model for nanomaterial convection through a complex geometry in presence of Kelvin force has been reported in this article. To involve the feature of nanomaterial, single phase model was selected which has nice accuracy for low concentration of iron oxide. Impose of magnetic source next to inner hot wall generates the new force which helps the nanofluid migration. The mathematical equations were solved via CVFEM. The accuracy of method was checked with comparing results against old publication. The styles of flow and isotherms with change of Ra, MnF were examined in results. Augment of Kelvin force converts the sole vortex to two eddies with opposite directions in low Ra and thermal plume appears inside the domain. Rise of buoyancy makes the strength of eddy to augment and Kelvin force makes the streamline values to increase. Nu enhances about 179. 36% with rise of Kelvin forces when Ra = 1e5. Nu augments about 11.13% with dispersing nanoparticles in to H2O. Rise of Ra makes Nu to grow about 119.97% when MnF = 4000.

An ultrasonic vortex C-Scan technique has been proposed to inspect stainless steel resistance spot welding (RSW) joints. Wavelet decomposition method is applied to analyze the original A-Scan data. By combination of semisoft threshold constructor and ultrasonic power ratio arithmetic (UPRA), the effect of corona bond is eliminated effectively, and its boundary is abstracted legibly. The nugget diameter measurement error is reduced from 2, approximately, to 0.19 mm. The fitted curve, nugget diameter and tensile strength, can be used to predict maximum tensile strength of joints online without destructive experiment. Shrinkage voids flaws located in the middle of the nugget have little influence on tensile strength.

Energy flux density for higher-order cylindrical vector vortex (HCVV) beam focused through a dielectric interface is analyzed numerically based on vector diffraction theory. Numerical results shows variation in the direction of the energy flux or Poynting vector distribution both in transverse and longitudinal plane upon suitably tuning the topological charge and polarization order of HCVV beam. We also note that the strong reverse flow of energy occur at the centre of the focal plane for certain values of the topological charge and polarization order. These results may find potential applications in optical trapping and optical manipulations.