Disk Rotation Research Articles

ОСОБЕННОСТЬ МЕХАНИЗИРОВАННОЙ ПОСАДКИ МАЛИНЫ САЖЕНЦАМИ С АСИММЕТРИЧНОЙ КОРНЕВОЙ СИСТЕМОЙ

An analysis of planting machines used in horticulture and forestry is given in the article. A version of the most simplified machine with the placement of a planting disk and support wheels on one axis mounted on plain bearings is proposed for planting raspberries. The results of studying an array of typical seedlings for the shape and overall dimensions of their root system are given. It has been established that up to half of the studied array of planting material has a root system close to the symmetrical type, and 37.5% of seedlings are characterized by a twofold or more degree of asymmetry. The nature of the interaction between the root system of a seedling and the soil covering it is shown. The seedling is placed in the seedling holder with the most developed part of the roots forward in the direction of rotation of the disk. The combined vertical and longitudinal pressure of the soil coming from the harrows overturns the seedling, as a result of which its stem can take a position close to horizontal. If, when placing a seedling in a seedling holder, the most developed part of its root system is oriented in the direction opposite to the direction of rotation of the planting disk, then, as a rule, in the final position the stem of the seedling is inclined from the vertical at a small angle. It has been established that the spatial orientation of the stem of a raspberry seedling has no practical significance, because the root shoots that grow after planting are bearing fruit, the quality of which is not related to the spatial orientation of the original stem. The planting machine has been successfully used on the farm for 25 years. It has been established that after its passage, about 5% of planted plants require additional manual trimming.

A finite element method study of the effect of vibration on the dynamic biomechanical response of the lumbar spine

BackgroundStudies focusing on lumbar spine biomechanics are very limited, and the mechanism of the effect of vibration on lumbar spine biodynamics is unclear. To provide guidance and reference for lumbar spine biodynamics research and vibration safety assessment, this study aims to investigate the effects of different vibrations on lumbar spine biodynamics. MethodsA validated finite element model of the lumbosacral spine was utilized. The model incorporated a 40 kg mass on the upper side and a 400 N follower preload. As a comparison, another model without a coupled mass was also employed. A sinusoidal acceleration with an amplitude of 1 m/s2 and a frequency of 5 Hz was applied to the upper and lower sides of the model respectively. FindingsWhen the coupled mass point is not introduced: in the case of upper-side excitation, the lumbar spine shows a significantly larger response in the x-direction than in the z-direction, while in the case of lower-side excitation, the lumbar spine experiences rigid body displacement in the z-direction without any movement, deformation, rotation, or stress changes in the x-direction. When the coupled mass point is introduced: both upper and lower-side excitations result in significant differences in z-directional displacement, with relatively small differences in vertebral rotation angle, disc deformation, and stress. Under upper excitation, low-frequency oscillations occur in the x-direction. In both types of excitations, the anterior-posterior deformation of the L2-L3 and L4-L5 intervertebral discs is greater than the vertical deformation. The peak (maximum) disc stress exceeds the average stress and stress amplitude across the entire disc. Regardless of the excitation type, the stress distribution within the disc at the moment of peak displacement remains nearly identical, with the maximum stress consistently localized on the anterior side of the L4-L5 disc. InterpretationAccurately simulating lumbar spine biodynamics requires the inclusion of the upper body mass in the lumbosacral spine model. The physiological curvature of the lumbar spine could escalate the risk of lumbar spine vibration injuries. It is more instructive to apply local high stress in the disc as a lumbar spine vibration safety evaluation parameter.

OER Activity of Iridium Nanoparticle Catalysts By RDE and Comparison with MEAs

To accelerate the deployment of green hydrogen, lowering the cost of water electrolyzer is one of the important issues. Iridium anode catalyst is a key material for highly efficient and stable operation of proton exchange membrane (PEM) water electrolyzer, however, limited resources of iridium lead to higher cost and the limited availability. Therefore, there is a strong need to develop novel catalysts that can reduce iridium usage without compromising on activity. Rotating electrode half-cell is a useful technique for OER activity measurement of anode catalysts [1], however broader consensus about the activity measurement protocol is still missing. In addition, it is also unclear whether the measured activity values from the RDE are consistent with those of the MEA. The RDE activity is influenced by various measurement parameters; catalyst loading on the disk electrode, ionomer content, electrolyte conductivity, potential range etc. Here, we demonstrate the impact of these RDE parameters on the measured OER activity using various iridium catalysts [2]. The OER activity was evaluated by linear sweep voltammogram at a scan rate of 1 mV sec-1 and a disk rotation rate of 3,600 rpm to minimize the contribution of capacitive current and mass transfer loss due to O2 bubbles. Too much catalyst loading on the disk electrode leads to a decrease in apparent OER activity, so that catalyst loading should be in the range where the catalyst activity is independent of the loading amount. Electrolyte solution was also found to have a significant effect on OER activity; comparing to the activity in perchloric acid solution (0.1 M HClO4), sulfuric acid solution (0.05 M H2SO4) and phosphoric acid (0.1 M H3PO4) showed 60% and 40% activity, respectively. To verify the obtained values of OER activity by RDE at the optimized condition, the OER activities were also determined by MEAs at corresponding conditions. The OER activities of MEA and RDE were found to be approximately the same regardless of catalyst species. Detailed measurement conditions and results will be discussed at the Meeting. References S. M. Alia, G. C. Anderson, J. Electrochem. Soc., 166 (2019) F282. T. Ioroi, T. Nagai, Z. Siroma, K. Yasuda, Int. J. Hydrogen Energy, 47 (2022) 38506.

Role of Ionic Liquids As Modifiers of Ru-Based Catalysts for Water Electrolysis

The generation of hydrogen through electrocatalytic water splitting has attracted tremendous attention in the past years [1,2]. Although water electrolysis has been already established in industrial settings, a large amount of research is still being carried out to further improve the catalytic efficiency and stability to exploit the full potential of this technology. One approach in this endeavor is the utilization of ionic liquids (ILs) as modifiers of electrocatalysts and electrode surfaces [3, 4]. The special physicochemical properties of the IL can affect and ideally improve the characteristics of the electrocatalyst, e.g., in terms of mass and electron transport [3]. Furthermore, the hydrophilic nature of certain ILs can in addition influence gas bubbles removal on the working electrode and improve the stability of the catalysts (e.g., Ru) by acting as a monomer-like binder [4].In this study, we compared the effect of four different ILs that are based on the same cation chain (1-butyl-3-(4-methylphenethyl)-1H-imidazol-3-ium) but different anions (-OAc, -NTf2, -Br, and -MeSO3) on Ru nanoparticles as catalysts for hydrogen and oxygen evolution reactions (HER and OER). To this end, carbon nanotubes were functionalized using different ILs and subsequently decorated with 1-2 nm Ru nanoparticles (Ru NPs) following an established organometallic approach [5]. We analyze how the catalytic activity/stability for HER, as well as OER, is influenced by the metal-ILs combination by established electrochemical methods utilizing a rotational disc electrode setup, with a particular focus on the different hydrophilic natures (depending on the anion) of the four ILs. To obtain a more comprehensive picture of how the different ILs affect Ru dissolution during the reaction, the IL/catalyst systems are additionally investigated by inductively coupled plasma-optical emission spectroscopy (ICP-OES) in a flow cell setup, as well as by electrochemical quartz crystal microbalance (EQCM) measurements.In this work, we discuss the use of ILs as modifiers for catalyst/electrode systems in water-splitting reactions, highlighting the importance of careful IL selection as well as the necessity for more future research in this field to fully explore the potential of IL/NPs-systems in electrochemistry.

Swirl Enhancement Effect on Turbine Rim Seal Performance

Abstract In gas turbines, sealing flow is extracted from the high-pressure compressor and supplied into the turbine wheel-space to suppress hot gas ingestion. Such hot gas ingestion is thought to be driven by the difference in either the static pressure or swirl between the mainstream and wheel-space flows. For the first time, experiments have been conducted in a low-speed single-stage axial turbine with a single-radial clearance rim seal and a “swirler” on the rotor disk. The objective is to evaluate the impact of enhanced wheel-space flow swirl on the rim seal performance. The swirler does not affect the mainstream flow. In the wheel-space, however, the swirler reduces static pressure; increases swirl; and improves rim seal performance (i.e., reduces the minimum sealing flowrate needed for hot gas ingestion prevention). Thus, the seal performance improvement occurs with increased difference in pressure and reduced difference in swirl between the mainstream and wheel-space flows. Therefore, it can be inferred that the rim seal performance depends more strongly on swirl than pressure. Preliminary gas turbine cycle performance studies indicate that net cycle efficiency benefits can be obtained.

INFLUENCE OF THE PATTERN OF THE COMBINED GRINDING SET OF THE DISC MILL ON INDIVIDUAL PAPER-FORMING PROPERTIES OF FIBROUS SEMI-FINISHED PRODUCTS AND THE PHYSICAL AND MECHANICAL CHARACTERISTICS OF THE FINISHED PRODUCT

The improvement of the process of grinding fibrous semi-finished products in pulp and paper production is caused by a reduction in the raw material base, requirements for the quality of finished products, as well as the desire to reduce production energy costs. Changing the grinding parameters allows you to change the properties and characteristics of the resulting materials in a wide range. The main controlled parameters of the grinding process are the gap between the rotor and stator disks, the rotor speed, the concentration of the fibrous mass. One of the important parameters of the grinding process is also the design of the grinding set. The article considers the influence of various configurations of cavities of the combined grinding set of a disc mill on the properties of the fibrous mass and finished paper castings. Individual paper-forming properties were evaluated, including the increase in the degree of grinding of the fibrous mass and the length of the fiber, as well as the physical and mechanical characteristics of the finished castings, which include the breaking length of the paper, the number of double folds and the tear resistance index. The grinding was carried out on a semi-industrial disc mill using a combined grinding set. For comparison, wavy and conical grinding cavities with straight unidirectional knives were selected. It was revealed that the wave-shaped grinding cavity has higher quality indicators in comparison with the conical grinding cavity by the nature of the impact on the fibrous mass.

Analysis of Single-Blade Passage and Full Circumference Large-Eddy Simulations of Turbine Rim Seal Flows

Abstract The flow in a 1.5-stage axial flow turbine with 16 vanes and 32 blades is investigated by large-eddy simulations with special focus on the analysis of the hot gas ingress through the rim seal into the upstream wheel space. Two setups with different solution domains are used. In the first large-eddy simulation, the full circumference of the turbine is resolved on a mesh with approximately 1 billion mesh cells. The second setup includes only a single-blade passage and is solved on a mesh with approximately 75 million cells. The analysis shows that the flow fields inside the upstream wheel space, i.e., between the disk of the upstream stator and the rotor disk strongly differ. In the 360 deg domain, two large-scale rotating vortex structures are observed, which have a strong impact on the ingress of main annulus gas into the wheel space. These structures cannot be captured in the single-blade passage domain. The instantaneous flow fields are further analyzed by dynamic mode decomposition to determine similarities and differences in the two flow fields. The comparison of the modes from the two setups reveals that the hot gas ingress from modes at the blade passing frequency generates a reduced sealing efficiency only at the outer radius of the wheel space. The additional presence of large-scale modes, however, reduce the sealing efficiency also in the inner wheel space. These results suggest that a single-blade passage simulation cannot be used for a reliable prediction of the hot gas ingress for the investigated turbine setup and operating condition.

Dynamometric Investigation on Airborne Particulate Matter from Automobile Brake: Impact of Disc Materials on Brake Emission Factor

In this work, we evaluated the impact of disc rotors of gray cast iron (GCI), nitrocarburized (NC), and superhard ceramic-coated (SCC) GCI on the brake wear PM emissions of passenger vehicles using dynamometric measurements. The brake emission factor (BEF) of the SCC was greatly reduced by more than a factor of 1/5 compared with those for the GCI and NC for both low-steel and non-steel friction materials. Surface topological and microstructural analyses confirmed that more severe wear was pronounced for the NC rotor compared with the SCC, as evidenced by large concave pits in the wear tracks. Analysis of the size-classified airborne PM suggests that reduced micron-sized particles, which originated from the GCI disc, were responsible for the lower BEF due to the increased hardness of the SCC.

Effect mechanism of multi-phase coupling on particle behaviors in magnetorheological foam plane finishing process

In this study, the effect mechanism of multi-phase coupling on particle behaviors in magnetorheological foam plane finishing (MRFPF) was researched to realize the collaborative control of particle distribution uniformity and polishing quality. To reach the goal, particle behaviors in MRFPF under the effect of fluid-solid coupling in magnetorheological foam were numerically studied by molecular dynamics (MD) simulation based on the force analysis that considering pressure drop due to fluid flow in foam pores. According to the simulation results, the influence law of different processing parameters on the radial distribution uniformity of particles was analyzed based on experimental analysis method. The results show that the polishing disk rotation speed and foam porosity have a positive effect on the radial distribution uniformity of particles, while the foam aperture affects little, and the greatest influence is produced by foam porosity which followed by polishing disk rotation speed and foam aperture. What's more, an optimal parameter combination with foam porosity 0.7, polishing disk rotation speed 30 rpm, and foam aperture 1 mm was determined by comprehensively considering the fluidity of MRPF and self-excited characteristics of abrasive particles in MRPF. Moreover, the advantages of MRFPF in improving the particle distribution uniformity and surface finishing quality to that of magnetorheological finishing were verified from numerical simulations and experiments.

Experimental and Numerical Investigations into the Effects of Rim Seal Structure on Endwall Film Cooling and Flow Field Characteristics

During the practical operation of gas turbines, relatively cooled air from the compressor and the rim seal is applied in order to prevent mainstream ingestion into the space between the rotor and stator disc cavities, which can prolong the service life of hot components. On the one hand, the purge flow from the rim seal will inevitably interact with the mainstream and result in secondary flow on the endwall. On the other hand, it can also provide an additional cooling effect. In this paper, four rim seal structures, including an original single-tooth seal (ORI), a double-tooth seal (DS), a single-tooth seal with an adverse direction of the coolant purge flow and mainstream (AS) and a double-tooth seal with an adverse direction of the coolant purge flow and mainstream (ASDS), are experimentally and numerically investigated with mass flow ratios of 0.5%, 1.0% and 1.5%. The flow orientation of the coolant from the rim seal is considered as one of the main factors. The pressure-sensitive paint technique is used to experimentally measure the film cooling effectiveness on the endwall, and flow field analysis is conducted via numerical simulations. The results show that the cooling effect decreases in the cases of DS and ASDS. AS and ASDS can achieve a better film cooling performance, especially under a higher mass flow ratio. Furthermore, the structural changes in the rim seal have little impact on the aerodynamic performance. AS and ASDS can both achieve a better aerodynamic and film cooling performance.

Free vibrations of axially loaded thin-walled shaft-disk rotors subjected to non-uniform temperature field

Research on vibrations of shaft-disk rotors in non-uniform thermal field is essential for the design of rotating machinery. In this paper, the dynamic model of axially loaded thin-walled shaft-disk rotors in axial non-uniform temperature field is developed, considering three-dimensional displacement fields of the shaft and disk. This model introduces the temperature-dependent properties of materials, and gyroscopic and centrifugal effects. Based on the Euler-Bernoulli beam theory and the Kirchhoff plate theory, Lagrange's equation is used to derive the differential equations of motion. By comparing with the results of the existing reference and finite element results, the accuracy of the present model is verified. The effects of the axial displacement of shaft, temperature-dependent material property, temperature difference, temperature distribution, disk position and axial preload on the free vibration of shaft-disk rotors are discussed. Results show that the present model can effectively predict free vibrations of shaft-disk rotors in axial non-uniform temperature field. The effect of thermal field on vibrations of shaft-disk rotors is affected by the rotational speed and disk location as well.

Experimental Measurements of Flow-Averaged Toroidal Vortices in Buoyancy-Dominated Rotating Cavities

Abstract The flow structures and heat transfer within rotating cavities of aero-engine axial compressors influence the thermal expansion of the rotor disks, and consequently the blade-tip clearances. To investigate the flow field at the bore and lower cavity region, experimental measurements have been acquired in an engine-representative test facility. Axial, tangential, and radial velocities were measured using a miniature five-hole probe at a range of axial and radial positions. Time-averaged results from 28 tests carried out at nondimensional parameters comparable to engine conditions: 1.3 × 104 ≤ Rez ≤ 8.2 × 104, 3.0 × 105 ≤ Reθ ≤ 3.2 × 106, 0.11 ≤ Ro ≤ 3.24, 0.14 ≤ βΔT ≤ 0.36 are presented in this paper. The axial and tangential velocity measurements conform to previous work, while the radial velocity component provides quantitative evidence of an asymmetric toroidal vortex in the cavity gap, biased toward the downstream disk. The vortex is characterized by the local vorticity and grows in strength and size as Rossby number increases above Ro = 0.34 to 1.63. The effect of βΔT on the vortex formation is negligible compared to the influence of the tangential Reynolds number as the local circulation is suppressed by the Coriolis forces at high rotational speeds. Both the tangential and radial velocity results suggest that as Ro is increased, the proportion of air that is radially ingested and expelled from a cavity decreases.

Optimization of operational parameters using RSM, ANN, and SVM in membrane integrated with rotating biological contactor

Membrane fouling is a critical bottleneck to the widespread adoption of membrane separation processes. It diminishes the membrane permeability and results in high operational energy costs. The current study presents optimizing the operating parameters of a novel rotating biological contactor (RBC) integrated with an external membrane (RBC + ME) that combines membrane technology with an RBC. In the RBC + ME, the membrane panel is placed external to the bioreactor. Response surface methodology (RSM) is applied to optimize the membrane permeability through three operating parameters (hydraulic retention time (HRT), rotational disk speed, and sludge retention time (SRT)). The artificial neural networks (ANN) and support vector machine (SVM) are implemented to depict the statistical modelling approach using experimental data sets. The results showed that all three operating parameters contribute significantly to the performance of the bioreactor. RSM revealed an optimum value of 40.7 rpm disk rotational speed, 18 h HRT and 12.4 d SRT, respectively. An ANN model with ten hidden layers provides the highest R2 value, while the SVM model with the Bayesian optimizer provides the highest R2. RSM, ANN, and SVM models reveal the highest R-square values of 0.97, 0.99, and 0.99, respectively. Machine learning techniques help predict the model based on the experimental results and training data sets.

ANALYTICAL DETERMINATION OF ASYMMETRIC PARAMETERS DISK HARROW

Having analyzed the technologies of pre-sowing field preparation, it should be concluded that the soil is processed before sowing with cultivators, disk, tooth and needle harrows, as well as soil tillers. Rolling before sowing ensures the destruction of soil lumps, as well as partial leveling of the field surface. However, the task of qualitative preparation of the field for sowing with the use of disk harrows is currently insufficiently solved, therefore it is necessary to substantiate the rational design parameters of an asymmetric disk harrow containing working bodies, which include, in particular, spherical disks. The following should also be noted, if the harrow is intended for use on harder, for example, chernozem soil, then the rod is attached to the hole further from the axis of rotation of the two-armed lever, which ensures the distance of the attachment device from the middle line of the harrow, which conditions the preservation of its balance when working on such soil. The process of rectilinear movement and rotation of spherical disks with a certain radius R in the soil at a depth h, which are installed at different angles to the direction of harrow movement, is considered. In the work, the impact of spherical disks with the remains of stubble, chopped straw was considered, it was established that spherical disks should be clamped between the sharpened cutting edge and the soil and cut them. It has been established that for guaranteed rotation of a spherical disk in the soil with minimal slippage and rolling resistance, its diameter must be substantiated. Since the spherical disk for soil cultivation is installed at an angle of attack α, to the direction of harrow movement, the projection of the spherical disk in the longitudinal-vertical plane is an ellipse with semi-axes. The rational diameter of the spherical disc of the asymmetric disc harrow under the conditions of its rotation in the soil with minimal values of sliding and rolling resistance, as well as a high-quality process of cutting the soil, stubble and soil displacement, is theoretically substantiated. It was established that the rational values of the diameter of the spherical disc of the asymmetric disc harrow depends on the depth h of soil treatment, the angle of attack α and the physical and mechanical properties of the soil.

MODELING OF ROUGH ROTARY MILLING OF CRANKSHAFT PINS

The development of the modern automotive industry requires a quick adaptation of new production methods. This is possible thanks to software capable of simulating manufacturing processes. The paper discusses the modeling of the machining operation of a crankshaft’s crankpins for a diesel engine with the use of the planetary milling method. i.e., modeling of milling operation when a disc milling cutter, having its cutting inserts directed inwards, is performing rotary motion, and at the same time, the axis of this milling cutter circulates around the axis of a machined crankpin. For this purpose, a geometrical model of the machining of the crankshaft’s crankpin has been developed. Based on the design documentation of the crankshaft of the 4C90 type diesel engine and the documentation of the Steyr internal disc milling cutter, their CAD models have been developed, and the both models were linked together with suitable kinematic dependencies. In the next step, the crankpin having a length of 25 mm was divided by planes (in quantity lp=21) into 1.25 mm sections. On the main cutting edge of two cutting inserts of the disc milling cutter, points were marked at intersection locations with these planes. Using the Inventor 2016 system, twelve spline curves have been generated for each plane because each plane intersects 12 cutting inserts mounted in cassettes positioned around the circumference of the body of the disc milling cutter. Next, the spline curves were brought to a common coordinate system, rotating them at an angle resulting from the positioning of the cassettes with cutting inserts in the body of the disc milling cutter. Prepared in such a way, spline curves were written in dwg format, which allowed for trimming of the spline curves at the circle with a radius of rcp = 27.90 mm, corresponding to the radius of the crankpin after milling, considering grinding allowance (ø55h6 + 0.80 mm grinding allowance). As a result, it enabled to leave sections of the arcs tangential to the diameter ø55.80 mm and, in such a way, generate the outline of the shape of the crankpin using the REGION command for 21 cross-sections. The outline of the cylindricity of the crankpin was obtained using the strategy of outlines of the roundness, which were generated earlier; this strategy consisted in the collection of 360 points on the circumference of 21 mutually parallel sections cut by planes perpendicular to the axis of the crankpin. To determine the effects of the circular feed rate of the circulating move of the axis of rotation of the internal disc milling cutter on the accuracy of the machining, simulations of the shape of the crankpin were performed for three values of the feedrate: vf = 1200 mm/min; vf = 2100 mm/min and vf = 3000 mm/min. The spline curves with a determined (depending on the duration of the simulation) number of points: 3500, 2100 and 1409 were obtained for each simulation. The calculated cylindricity deviation for the feedrate vf = 1200 mm/min amounted to CYLrck = 0.2272 mm, for the feedrate vf = 2100 mm/min – CYLrck = 0.2406 mm, while for the feedrate vf = 3000 mm/min – CYLrck = 0.2929 mm.

Flute Instability Effects for Disk Accretion onto Neutron Stars with Strong Magnetic Fields

The flute instability at the inner edge of a thin diamagnetic accretion disk is analyzed. Themagnetic field configuration model fromAly (1980) is used. We have analyzed a modified dispersion relationfor the flute instability that takes into account the Keplerian disk rotation. We have derived the inner radiusof the accretion disk within our analysis of the flute instability.We show that the inner radius does not differfrom the Alfve´ n radius for spherical accretion to within a dimensionless coefficient, with the proportionalitycoefficient depending only on the turbulence alpha parameter and the relative disk thickness (h/r).

Vibration Control of a Multi-Disc Rotor System with Active Lateral Bearings and Disturbance Estimation

A rotor system used in a wide range of engineering applications generally consists of a rotor shaft, multiple discs, blades and other essential components, generating a multi-disc rotor arrangement. System uncertainties caused by unbalanced discs and disc mass variation, compounded with external disturbances under different operating conditions, can lead to a variation in rotor-dynamic characteristics with multiple structural resonances, potentially causing an excessive level of rotor lateral vibration. Therefore, to effectively suppress lateral vibration for such a multi-disc rotor system, an active vibration control approach using active lateral bearings with disturbance estimation is presented in this work. The utilized active lateral bearings can generate necessary bearing displacement regulations to eliminate the bearing forces so to effectively control the lateral vibration of the rotor system. The disturbance estimation approach is used to estimate the unknown uncertainties associated with the system's internal dynamics and external disturbances affecting the rotor system, incorporating an extended state observer (ESO). Utilizing the total disturbance estimated by the ESO to cancel out the effects of the disturbance using active lateral bearings, the rotor lateral vibration can be satisfactorily suppressed with sufficient control robustness against uncertainties in the rotor internal dynamics, particularly associated with the degree of mass unbalance of rotor discs, demonstrating the effectiveness of the active vibration control approach for suppressing vibration in a rotor system.

Galaxy kinematics and mass estimates at z ∼ 1 from ionized gas and stars

ABSTRACT We compare ionized gas and stellar kinematics of 16 star-forming galaxies (log (M⋆/M⊙) = 9.7–11.2, SFR =6 − 86 M⊙ yr−1) at z ∼ 1 using near-infrared integral field spectroscopy (IFS) of Hα emission from the KMOS3D (the K-band Multi-Object Spectrograph 3D) survey and optical slit spectroscopy of stellar absorption and gas emission from the LEGA-C (Large Early Galaxy Astrophysics Census) survey. Hα is dynamically colder than stars, with higher disc rotation velocities (by ∼45 per cent) and lower disc velocity dispersions (by a factor ∼2). This is similar to trends observed in the local Universe. We find higher rotational support for Hα relative to [O ii], potentially explaining systematic offsets in kinematic scaling relations found in the literature. Regarding dynamical mass measurements, for six galaxies with cumulative mass profiles from Jeans Anisotropic Multi-Gaussian Expansion (JAM) models the Hα dynamical mass models agree remarkably well out to ∼10 kpc for all but one galaxy (average $\Delta M_{\rm dyn}(R_{e,\rm F814W})\lt 0.1$ dex). Simpler dynamical mass estimates based on integrated stellar velocity dispersion are less accurate (standard deviation 0.24 dex). Differences in dynamical mass estimates are larger, for example, for galaxies with stronger misalignments of the Hα kinematic major axis and the photometric position angle, highlighting the added value of IFS observations for dynamics studies. The good agreement between the JAM and the dynamical models based on Hα kinematics at z ∼ 1 corroborates the validity of dynamical mass measurements from Hα IFS observations, which can be more easily obtained for higher redshift galaxies.

Unsteady Al2O3-Cu/H2O hybrid nanofluid flow over a rotatable stretching disk with heat generation and deceleration: Stable dual solutions

This study reveals the impact of heat generation and variable strength of rotation on the unsteady flow of a hybrid nanofluid over a rotatable disk with stretching characteristics and deceleration. A novel mathematical model specifically tailored to elucidate the behavior of a hybrid nanofluid is proposed. By employing similarity variables, the governing model is reformulated into ordinary differential equations (ODEs). The bvp4c function (MATLAB) is employed to efficiently obtain the numerical solutions of these ODEs. To provide a comprehensive study, a stability analysis is also conducted to investigate the properties associated with the non-unique dual solutions generated by the model. Dual solutions are generated, and both are analyzed to be stable. A lower amount of heat generation with greater disk rotation strength is recommended to further improve the heat transfer rate of the model. The bifurcation point is absent within the setup ranges of the parameters in the present study, which suggests a well-maintained laminar flow simulation. The findings of this study offer valuable insights and can assist other researchers in improving their understanding and modeling of similar fluid flow systems, particularly hybrid nanofluid flow systems.

Numerical and regression analysis of horizontal magnetic field in slippery nanofluid flow with Arrhenius activation energy

The significance of magnetic field in the fluid flow models is important in order to stabilize the flow stream. The present work explores the horizontal magnetic field influences in steady-state laminar swirl Newtonian nanomaterial fluid flow triggered by disk rotation. To categorize the thermal performance, a well-established theory of nanofluid (Buongiorno model) is implemented in flow phenomenon. Thermal radiative term is demonstrated in the energy transportation equation. The impact of chemical species is investigated by the expression of AAE (Arrhenius activation energy). The flow model is normalized in accordance with von Kármán similarity transformations. The resulting normalized system of equations is converted to a system consisting of first order differential equations and then is solved by Runge-Kutta-Fehlberg (RKF-45) built-in method. The physical results are discussed graphically on velocity, temperature, and concentration streams. Shear stresses, local Nusselt and Sherwood numbers are calculated at the surface of the rotating disk. In addition, the regression process is utilized to address the parameters impacts on the variables. The stabilizing impact of magnetic field along radial direction is noticed by means of direction angle close to 00 and 900. Velocity profiles in radial direction are enhanced by the velocity slip parameter. Concentration filed is increased through activation energy. The inclination angle has a weak impact on heat transfer rate. Finally, a comparison is established with the published literature in limiting scenario.