Vortex Liquid Research Articles

Magnetic field induced transition from a vortex liquid to Bose metal in ultrathin a -MoGe thin film

We identify a magnetic field induced transition from a vortex liquid to Bose metal in a 2-dimensional amorphous superconductor, a-MoGe, using a combination of magnetotransport and scanning tunnelling spectroscopy (STS). Below the superconducting transition, Tc ~ 1.36 K, the magnetoresistance isotherms cross at a nearly temperature independent magnetic field, H_c^*~ 36 kOe. Above this field, the temperature coefficient of resistance is weakly negative, but the resistance remains finite as T --> 0, as expected in a bad metal. From STS conductance maps at 450 mK we observe a very disordered vortex lattice at very low fields that melts into a vortex liquid above 3 kOe. Up to H_c^* the tunnelling spectra display superconducting gap and coherence peak over a broad background caused by electron-electron interactions, as expected in a vortex liquid. However, above H_c^* the tunnelling spectra continue to display the gap but the coherence peak gets completely suppressed, suggesting that Cooper pairs lose their phase coherence. We conclude that H_c^* demarcates a transition from a vortex liquid to Bose metal, that eventually transforms to a regular metal at a higher field H* where the gap vanishes in the electronic spectrum.

Interactions of Self-Localised Optical Wavepackets in Reorientational Soft Matter

The interaction of optical solitary waves in nematic liquid crystals, nematicons and vortices, with other nematicons and localised structures, such as refractive index changes, is reviewed. Such interactions are shown to enable simple routing schemes as a basis for all-optical guided wave signal manipulation.

Chemisorption of CO2 in a gas–liquid vortex reactor: An interphase mass transfer efficiency assessment

AbstractTo develop cost‐effective CO2 capture technology process intensification will play a vital role. In this work, the capabilities of a gas–liquid vortex reactor (GLVR) as novel process intensification equipment are evaluated by studying its interphase mass transfer parameters to build up the fundamentals for its future application to for example, CO2 capture. The NaOH‐CO2 chemisorption system and Danckwerts' model are applied to obtain the effective interfacial area and liquid‐side mass transfer coefficient. Results show that the gas–liquid contact in the GLVR is capable of both generating a large interfacial area in a small reactor volume and creating a region with high‐energy dissipation to improve mass transfer. A comparison of the volumetric mass transfer coefficients with data reported in literature for conventional and intensified reactor types confirms a superior mass transfer efficiency and, most importantly, a favorable energetic efficiency of the GLVR.

Liquid vortexes and flows induced by femtosecond laser ablation in liquid governing formation of circular and crisscross LIPSS

Orientations of laser induced periodic surface structures (LIPSS) are usually considered to be governed by the laser polarization state. In this work, we unveil that fluid dynamics induced by femtosecond (fs) laser ablation in liquid (fs-LAL) can easily break this polarization restriction to produce irregular circular-LIPSS (CLIPPS) and crisscross-LIPSS (CCLIPSS). Fs laser ablation of silicon in water shows formation of diverse LIPSS depending on ablation conditions. At a high power of 700 mW (repetition rate of 100 kHz, pulse duration of 457 fs and wavelength of 1045 nm), single/twin CLIPSS are produced at the bottom of macropores of several microns in diameter due to the formation of strong liquid vortexes and occurrence of the vortex shedding effect. Theoretical simulations validate our speculation about the formation of liquid vortex with an ultrahigh static pressure, which can induce the microstructure trenches and cracks at the sidewalls for fs-LAL of Si and tungsten (W) in water, respectively. At a low power of 50 mW, weak liquid vortexes are produced, which only give birth to curved LIPSS in the valleys of grooves. Consequently, it is deduced that liquid vortex plays a crucial role in the formation of macropores. Mountain-like microstructures induce complex fluid dynamics which can cause the formation of CCLIPSS on them. It is believed that liquid vortexes and fluid dynamics presented in this work open up new possibilities to diversify the morphologies of LIPSS formed by fs-LAL.

Liquid vortexes and flows induced by femtosecond laser ablation in liquid governing formation of circular and crisscross LIPSS

Orientations of laser induced periodic surface structures (LIPSS) are usually considered to be governed by the laser polarization state. In this work, we unveil that fluid dynamics induced by femtosecond (fs) laser ablation in liquid (fs-LAL) can easily break this polarization restriction to produce irregular circular-LIPSS (CLIPPS) and crisscross-LIPSS (CCLIPSS). Fs laser ablation of silicon in water shows formation of diverse LIPSS depending on ablation conditions. At a high power of 700 mW (repetition rate of 100 kHz, pulse duration of 457 fs and wavelength of 1045 nm), single/twin CLIPSS are produced at the bottom of macropores of several microns in diameter due to the formation of strong liquid vortexes and occurrence of the vortex shedding effect. Theoretical simulations validate our speculation about the formation of liquid vortex with an ultrahigh static pressure, which can induce the microstructure trenches and cracks at the sidewalls for fs-LAL of Si and tungsten (W) in water, respectively. At a low power of 50 mW, weak liquid vortexes are produced, which only give birth to curved LIPSS in the valleys of grooves. Consequently, it is deduced that liquid vortex plays a crucial role in the formation of macropores. Mountain-like microstructures induce complex fluid dynamics which can cause the formation of CCLIPSS on them. It is believed that liquid vortexes and fluid dynamics presented in this work open up new possibilities to diversify the morphologies of LIPSS formed by fs-LAL.

Online Measurement of Gas and Liquid Flow Rates in Wet Gas Using Vortex Flowmeter Coupled With Conductance Ring Sensor

Wet gas flow commonly exists in several industries. The online measurement of gas and liquid flow rate is beneficial for economic efficiency. A combination of vortex flowmeter and liquid film sensor was proposed for two-phase flow measurement of wet gas. The specific form is as follows: the dual-modality sensing system was designed and calibrated by an annular mist flow loop. The fluid materials are pure air and water liquid. The ranges of operating pressure, the superficial gas velocity, and superficial liquid velocity are 1.5 bar–3.5 bar, 18.86–37.73 m/s, and 0.0028–0.028 m/s. Then the function relations of liquid film thickness and vortex frequency, with gas and liquid Weber numbers were built, respectively. Finally, a novel model for calculating gas and liquid flow rates in wet gas measurement was established, and solved by the Newton iterative algorithm. It showed that the percentage error (PE) of gas flow rate predicted by the model is within ±1.5%, and the mean absolute percentage error (MAPE) is 0.55%. The full-scale PE of liquid flow rate is within ±5% and the MAPE is 3.48%. The data show that this solution for gas and liquid flow rates measurement of wet gas by combining a vortex flowmeter with a conductance ring sensor is feasible.

Development of a method for numerical modeling of the separation flow at the entrance to a rectangular exhaust channel with sharp edges

We have developed a method for mathematically simulating flow separation at the entrance to the exhaust channels of rectangular shape, using stationary discrete vortices in an ideal incompressible liquid in full spatial setting. When designing the discrete model, straight and curvilinear quadrangular vortex frames, straight and curvilinear horseshoe-shaped vortices were used. Using the developed computational procedure and computer program, the outline of vortex zone at the entry to the rectangular exhaust channel with sharp edges and the axial velocity of the air flow are determined. The results were compared with studies by different authors, as well as calculations by the methods of the theory of functions of a complex variables for the slotted exhausts and with results earlier obtained by us for calculation the square exhaust opening by means of discrete vortices in non-stationary and quasi-symmetric setting. The further direction of research will be related to the investigation of flows detached at the entrance to the rectangular exhaust hoods by the developed method, as well as by CFD methods. Then it is necessary to identify the regularities of the change of the local resistance coefficient at the entrance to the exhaust hood, shaped by the found outlines of the vortex zones.

Simulation of the enhancement of Dean flow on the liquid–liquid extraction in membrane contactors

Dean vortices generated through the curved paths have been demonstrated to be beneficial to enhance gas–liquid mass transfer in membrane contactors. However, the effect of Dean vortices in liquid–liquid membrane extraction was seldom studied. This work implemented a numerical model describing the liquid–liquid extraction process in curved membrane contactors with the software of COMSOL. The liquid–liquid extraction experiments were first performed verifying the applicability of the simulation. Firstly, the discussion about the role of membrane resistance revealed the fact that enhancement provided by Dean flows would be more pronounced for systems with lower membrane resistance. A parametric study was then conducted including geometric parameters and physical properties of the fluid, which indicated smaller pitch, smaller curvature diameter, and less viscous fluid led to a better enhancement. The intensification factor was in the range of 1 ∼ 1.8, corresponding to the Dean number range of 5 ∼ 30. Considering the energy consumption, the values of modified intensification factors were lower than 1 only when the Dean numbers were smaller than 8. Finally, the performance of four curved geometries: helically-wound, 90-degree bend, meander-shaped, knotted were compared. The presented model yielded new insights into the liquid–liquid exaction enhancement in the curved membrane contactors.

Characteristics of flow and liquid distribution in a gas–liquid vortex separator with multi spiral arms

Fischer–Tropsch (F–T) synthesis is an important route to achieve the clean fuel production. The performance of gas–liquid separation equipment involving in the progressive condensation and separation of light and heavy hydrocarbons in the oil-gas products has become a bottleneck restricting the smooth operation of the F–T process. In order to remove the bottleneck, a gas–liquid vortex separator with simple structure, low pressure drop and big separation capacity was designed to achieve the efficient separation between gas and droplets for a long period. The RSM (Reynolds Stress Model) and DPM (Discrete Phase Method) are employed to simulate the flow characteristics and liquid distribution in the separator. The results show that the separation efficiency is influenced by the flow field and liquid phase concentration in the annular zone. The transverse vortex at the top of spiral arm entrains the droplets with small diameter into the upper annular zone. The entrained droplets rotate upward at an angle of about 37.4°. The screw pitch between neighbor liquid threads is about 0.3 m. There is a top liquid ring in the top of annular zone, where the higher is the liquid phase concentration, the lower is the separation efficiency. It is found that by changing the operating condition and the annular zone height the vortex can be strengthened but not enlarged by the inlet velocity. The screw pitch is not affected by both inlet velocity and annular zone height. The liquid phase concentration in the top liquid ring decreases with both the increases of inlet velocity and annular zone height. The total pressure drop is almost not affected by the annular zone height but is obviously affected by the inlet velocity. When the height of annular zone is more than 940 mm, the separation efficiency is not changed. Therefore, the annular zone height of 940 mm is thought to be the most economical design.

Development & Fabrication of AL-3Mg Based SiC & Gr. Hybrid Metal Matrix Composite by Stir Casting Method

The congregation of ceramic particulates in Aluminum hybrid metal matrix composites induces a greater significance in marine and automotive engineering applications because of its strength to weight ratio, good anti-corrosive properties, and high-temperature resistance. The research work focuses on the fabrication of hybrid metal matrix composite with influences of hard ceramic particulates like silicon carbide and dispersoid of graphite in Al-3Mg matrix material, and tribology behavior routed through the liquid metallurgical vortex method. The characterizations of conglomerate like, tensile properties, hardness, compression tests were investigated. The wear resistance increases with assorted graphite compositions. Microstructural examination shows the dispersoids of graphite and silicon carbides are uniformly distributed. The test results of Al-3Mg conglomerates reveal that tensile and hardness properties were enhanced with the addition of Gr. & SiC, as silicon carbide being a harder constituent mixed with a ductile matrix.

Tribological performance of aluminium hybrid self-lubricating composites reinforced with green synthesized graphene

In this contemporary research work, graphene nanosheets were synthesized by the green method using agricultural waste and characterized by FESEM, XRD and Raman spectroscopy. Vortex liquid metallurgy technique is used to fabricate AA7075 hybrid composites reinforced with graphene and hard ceramic. The samples were evaluated for tensile strength, hardness and tribological behaviour. The influencing wear parameters percentage of graphene reinforcement, load, sliding speed and sliding distance were varied three levels each. An empirical relationship was formulated using face-centred central composite design considering wear weight loss and coefficient of friction as output responses. The influencing parameters on the output responses were determined by employing analysis of variance and the objective is to find the optimal process parameters. Graphene enriched the mechanical and wear behaviour. The composite having a 0.5 reinforcement percentage of graphene exhibited higher hardness and higher tensile strength. The optimal combination of tribological parameters for minimum wear loss and friction coefficient was found for 0.5% of graphene reinforcement, 30 N load, 2.5 m s−1 sliding speed, 1000 m sliding distance. The worn surface was also analyzed using FESEM and inverted microscope images.

Vortex creation and control in the Kitaev spin liquid by local bond modulations

The Kitaev model realizes a quantum spin liquid where the spin excitations are fractionalized into itinerant Majorana fermions and localized $\mathbb{Z}_2$ vortices. Quantum entanglement between the fractional excitations can be utilized for decoherence-free topological quantum computation. Of particular interest is the anyonic statistics realized by braiding the vortex excitations under a magnetic field. Despite the promising potential, the practical methodology for creation and control of the vortex excitations remains elusive thus far. Here we theoretically propose how one can create and move the vortices in the Kitaev spin liquid. We find that the vortices are induced by a local modulation of the exchange interaction; especially, the local Dzyaloshinskii-Moriya (symmetric off-diagonal) interaction can create vortices most efficiently in the (anti)ferromagnetic Kitaev model, as it effectively flips the sign of the Kitaev interaction. We test this idea by performing the {\it ab initio} calculation for a candidate material $\alpha$-RuCl$_3$ through the manipulation of the ligand positions that breaks the inversion symmetry and induces the local Dzyaloshinskii-Moriya interaction. We also demonstrate a braiding of vortices by adiabatically and successively changing the local bond modulations.

Liquid hydrodynamics in a gas-liquid vortex reactor

A gas–liquid vortex reactor (GLVR) is considered one of the promising Process-Intensified Equipment for applications that require high mixing and mass transfer efficiency. To gain understanding of the fundamentals of GLVR operation, the gas–liquid hydrodynamics in the GLVR has been investigated by high-speed imaging, digital images analysis and cross correlation. Gas bubbles and liquid ligaments are observed in the GLVR over a wide operating window. The dynamic liquid layer thickness in the GLVR chamber varies in the range of 26–36 mm. The instantaneous and time-average velocity fields of the liquid phase are obtained with a guaranteed high signal-to-noise ratio (cross correlation peak ratio higher than 10), allowing the analysis of liquid turbulent properties including the turbulent kinetic energy and its dissipation rate. Results show that the high turbulent kinetic energy dissipation rate ranging from 23 to 114 m2/s3 contributes to a high mixing and mass transfer efficiency in the GLVR.

Numerical study of hole formation in a thin flapping liquid sheet sheared by a fast gas stream

This study reports aerodynamics effects of a fully developed double-shear layer gas flow in the perforation and disintegration of a thin liquid sheet using three-dimensional numerical simulations. A double-shear layer gas flow, where a thin quiescent gas layer is sandwiched between the two fast moving gas layers, is first simulated up to a statistically steady state. The downstream dynamics of the gas shear layers shows vortex shedding and three-dimensional rib-like vortical structures, similar to the wake of a bluff body. This gas flow is then used as the initial condition for a liquid-gas simulation, where the liquid phase is sandwiched by the top and bottom fast gas streams. A thin liquid sheet with a thickness of 25 μm is considered using air/water conditions. The liquid sheet oscillates and small holes, preceded by craters surrounded by ripples, are formed. The thinning of the liquid sheet, spanwise corrugations, and vortex separations within the liquid-gas boundary layer are shown to govern the dynamics of the liquid sheet. A localized pressure jump is also observed inside the liquid sheet and precedes the rupture of the liquid sheet by pushing the liquid away in the span direction. The holes formed subsequently grow in size, collide and merge with each other, and break the liquid sheet into multiple droplets.

Analysis of pressure fluctuations for oil-gas two-phase flow in a horizontal pipe using the bubble number density equation

Visualization experiments and numerical simulations of two-phase flow are conducted to study the pressure fluctuation characteristics of oil-gas flow in horizontal pipes. The two-fluid model based on the Eulerian–Eulerian method is adopted, and the bubble number density equation (BNDE) is introduced to the simulation to predict the bubble size and distribution within the pipe. The bubble size and pressure variations in the pipe obtained from the simulations agree well with the recorded values from the experiments. The fast Fourier transform (FFT) algorithm is used to analyze the characteristics of pressure fluctuations, and the results show that the sudden pressure increase in the pipe sections is related to gas injection. The bubble number density increases with liquid flow rate (Ql ), which causes the oil-gas flow to be more turbulent while increasing the amplitude of high-frequency fluctuations. The maximum amplitude for the dominant frequency is observed near the pump inlet for low liquid flow rates. At high liquid flow rates, more liquid vortices are found near the gas orifice, and there is a maximum amplitude for the dominant frequency in this section. Due to the high swirling strength at larger inlet gas volume fraction (IGVF), there is an obvious increase in the amplitude of low-frequency fluctuations, while the amplitude of high-frequency fluctuations is nearly the same under all IGVF.

Classical magnetic vortex liquid and large thermal Hall conductivity in frustrated magnets with bond-dependent interactions

Recently, the observation of large thermal Hall conductivities in correlated insulators with no apparent broken symmetry has generated immense interest and debates on the underlying ground states. Here, considering frustrated magnets with bond-dependent interactions, which are realized in the so-called Kitaev materials, we theoretically demonstrate that a large thermal Hall conductivity can originate from a classical ground state without any magnetic order. We discover a liquid state of magnetic vortices, which are inhomogeneous spin textures embedded in the background of polarized spins, under out-of-plane magnetic fields. In the classical regime, different configurations of vortices form an effectively degenerate manifold. We study the static and dynamical properties of the magnetic vortex liquid state at zero and finite temperatures. In particular, we show that the spin excitation spectrum resembles a continuum of nearly flat Chern bands, which ultimately leads to a large thermal Hall conductivity. Possible connections to experiments are discussed.

Micromixing in a gas–liquid vortex reactor

AbstractThe gas–liquid vortex reactor (GLVR) has substantial process intensification potential for multiphase processes. Essential in this respect is the micromixing efficiency, which is of great importance in fast reaction systems such as crystallization, polymerization, and synthesis of nanomaterials. By creating a vortex flow and taking advantage of the centrifugal force field, the liquid micromixing process can be intensified in the GLVR. Results show that introducing a liquid into a gas‐only vortex unit results in suppression of primary and secondary gas flow. The Villermaux–Dushman protocol is applied to study the effects of the gas flow rate, liquid flow rate, and liquid viscosity based on a segregation index. Based on the incorporation model and reaction kinetics, the micromixing time of the GLVR is determined to be in the range of 10−4 ~ 10−3 s, which is comparable to the highly efficient rotating packed bed and substantially better than a static mixer.

Universal behavior of the bosonic metallic ground state in a two-dimensional superconductor

Anomalous metallic behavior, marked by a saturating finite resistivity much lower than the Drude estimate, has been observed in a wide range of two-dimensional superconductors. Utilizing the electrostatically gated LaAlO3/SrTiO3 interface as a versatile platform for superconductor-metal quantum phase transitions, we probe variations in the gate, magnetic field, and temperature to construct a phase diagram crossing from superconductor, anomalous metal, vortex liquid, to the Drude metal state, combining longitudinal and Hall resistivity measurements. We find that the anomalous metal phases induced by gating and magnetic field, although differing in symmetry, are connected in the phase diagram and exhibit similar magnetic field response approaching zero temperature. Namely, within a finite regime of the anomalous metal state, the longitudinal resistivity linearly depends on the field while the Hall resistivity diminishes, indicating an emergent particle-hole symmetry. The universal behavior highlights the uniqueness of the quantum bosonic metallic state, distinct from bosonic insulators and vortex liquids.

Anomalous vortex liquid in charge-ordered cuprate superconductors

The interplay between charge order and d-wave superconductivity in high-[Formula: see text] cuprates remains an open question. While mounting evidence from spectroscopic probes indicates that charge order competes with superconductivity, to date little is known about the impact of charge order on charge transport in the mixed state, when vortices are present. Here we study the low-temperature electrical resistivity of three distinctly different cuprate families under intense magnetic fields, over a broad range of hole doping and current excitations. We find that the electronic transport in the doping regime where long-range charge order is known to be present is characterized by a nonohmic resistivity, the identifying feature of an anomalous vortex liquid. The field and temperature range in which this nonohmic behavior occurs indicates that the presence of long-range charge order is closely related to the emergence of this anomalous vortex liquid, near a vortex solid boundary that is defined by the excitation current in the [Formula: see text] 0 limit. Our findings further suggest that this anomalous vortex liquid, a manifestation of fragile superconductivity with a suppressed critical current density, is ubiquitous in the high-field state of charge-ordered cuprates.

Influence of Balance Hole Diameter on Leakage Flow of the Balance Chamber in a Centrifugal Pump

The balancing holes in centrifugal pumps with seals mounted in both suction and discharge sides are one of the approaches used by pump manufacturers to reduce the axial thrust. The balance hole diameter directly affects the axial force of the centrifugal pump. The flow characteristics in the balance chamber are closely related to the balance hole diameter. However, research is not very clear on the internal flow of the balanced chamber, due to the small axial and radial sizes and the complicated flow conditions in the chamber. In this paper, we analyzed the influence of the balance hole diameter on the liquid leakage rate, flow velocity, and vortex motion in the balance chamber. The results indicated that when the balance hole diameter was lower than the design value, the volume flow rate of leakage flow was proportional to the diameter. The liquid flow rate and vortex distribution rules in the balance chamber were mainly associated with the coeffect of radial leakage flow in the rear sealing ring interval and the axial balance hole leakage flow. The research has revealed the mechanisms of leakage flow of the balance chamber in the centrifugal pump and that this is of great significance for accurate calculation and balancing of the axial force.