Momentum Characteristics Research Articles

Shape factor and thermal radiation effects on convective MHD flow of Casson blood ternary hybrid nano‐fluid through a stretched rotating rigid disk

AbstractThe mathematical modeling of blood flow with the incorporation of ternary hybrid nanoparticles (i.e., titania, silica, and alumina nanoparticles) is the focus of this work. The flow of blood is simulated using the Casson fluid model. The impacts of ternary hybrid nanoparticles, shape factor, and Geometry of solid nanoparticles are visualized and investigated. The momentum and thermal characteristics of a flowing liquid are determined by considering magnetization, porosity, and nonlinearized radiating thermal flux. The basic partial differential equations resulting from mathematical modeling are turned into non‐linear ordinary differential equations using suitable velocity transforms. The derived nonlinear equations are then numerically calculated using the 4th‐5th order Runge‐Kutta‐Fehlberg method with the shooting technique and analytically solved by the Adomian decomposition method (ADM). The effects of the factors involved on the dimensionless profiles produced are fully addressed. It is found that the Skin friction factor and heat transfer rate in the radial direction upsurge with the augment of both rotation parameter and nanoparticles volume fraction; however, the Skin friction factor drops in the azimuthal direction. Also, results obtained reveal an enhancement in the local Nusselt number with the upsurge in the magnitude of radiation parameter, Rd, solid nanoparticles concentration, , shape factor value, s, and disk temperature, . For validation, the outcomes of this inquiry were compared to the outcomes of the HAM‐based Mathematica software. In addition, the acquired analytical DRA data are compared to numerical RKF45 values and those given in the literature.

Investigation of turbulence and interfacial exchange features of the gap area within the fully developed Shallow-Submerged canopy flow

The flow patterns within a longitudinal gap area formed by discontinuous distributions of submerged canopy, as well as the momentum and mass exchange characteristics between the gap area and the overlying free-flow, were studied using high-resolution Large Eddy Simulation (LES). The gap area is located within the fully developed region of submerged canopy flow. The simulations considered four aspect ratios of the gap area, L/h (ranging from 1 to 4), where L and h represent the span of the gap area and the height of the canopy, respectively, and two canopy densities, ϕ = 0.08 and 0.15. Results indicate that recirculation vortices appear only at ϕ = 0.15 and penetrate the downstream canopy patches to varying extents, with the distance of invasion decreasing as L/h increases. Influenced by the recirculation vortices, the bed shear stress in the downstream part of the gap area and the initial section of the downstream canopy patch is significantly increased compared to the fully developed region of the upstream canopy patch. Within the parameter range covered, vertical penetration of the mixing layer into the gap area always occurs, consistently falling into the shear layer growth regime, with significant enhancement of turbulence within the gap area even at L/h = 1. The high momentum entrainment elevates longitudinal velocity and turbulence intensity in the upper corner regions of the downstream canopy patch’s leading edge, combined with localized increases in bed shear stress, potentially destabilizing plants at the forefront of the downstream canopy patch. Although the total momentum exchange across the interface between the gap area and the upper free-flow layer is approximately independent of L/h, larger canopy densities lead to stronger momentum transport, and turbulent transport always dominates. Mass exchange generally increases with L/h, with more efficient vertical mass exchange in ϕ = 0.15 cases at L/h = 3 and 4.

Spin–momentum properties in the gradient-index fiber

The vector characteristics of the kinetic momentum, spin angular momentum (SAM), and light field of a radially polarized vortex beam (RPVB) in the radial gradient-index (GRIN) fiber are analyzed using a unified methodology based on the generalized Huygens-Fresnel principle and the spin-momentum relationship. The kinetic momentum, SAM, transverse-type spin (t-SAM), longitudinal-type spin (l-SAM) and light field contain parallel and perpendicular components to the optical axis in the GRIN fiber. Moreover, the optical spin skyrmion from the SAM, t-SAM, and l-SAM can be observed at the semi-focal plane and the focal plane of the GRIN fiber. To the best of our knowledge, this is the first confirmation of spin skyrmions in the GRIN fiber. The analysis of spin-momentum properties of an RPVB in the GRIN fiber combined with the generalized Huygens-Fresnel principle and the spin-momentum relationship can be applied in describing the vector properties of transmission in atmospheric and optical systems.

Fractional numerical analysis of γ-Al2O3 nanofluid flows with effective Prandtl number for enhanced heat transfer

Abstract Nanoparticles have gained recognition for significantly improving convective heat transfer efficiency near boundary layer flows. The characteristics of both momentum and thermal boundary layers are significantly influenced by the Prandtl number, which holds a crucial role. In this vein, the current study conducted a detailed computational analysis of the mixed convection flow of $\gamma$Al$_2$O$_3$-H$_2$O and $\gamma$Al$_2$O$_3$-C$_2$H$_6$O$_2$ nanofluids over a stretching surface. This research integrates an effective Prandtl number, utilizing viscosity and thermal conductivity models based on empirical findings. Additionally, a unique double-fractional constitutive model is debuted to accurately evaluate the effective Prandtl number’s function in the boundary layer. The equations were solved using a numerical technique that combined the finite-difference method with the L$_1$ algorithm. This investigation presents numerical findings related to the velocity, temperature distributions, wall shear stress coefficient, and heat transfer coefficient, contrasting scenarios with and without the effective Prandtl number. The research shows that integrating nanoparticles into the base fluids reduces the temperature of the nanofluid with an effective Prandtl number while enhancing the heat transfer rate irrespective of its presence. Nonetheless, the introduction of a fractional parameter reduced the heat transfer efficiency within the system. Notably, the $\gamma$Al$_2$O$_3$-C$_2$H$_6$O$_2$ nanofluid demonstrates superior heat transfer enhancement capabilities compared to its $\gamma$Al$_2$O$_3$-H$_2$O counterpart but also exacerbates the drag coefficient more significantly. Many practical applications of this study include electronics cooling, industrial process heat exchangers, and rotating and stationary gas turbines in power plants, and efficient heat exchangers in aircraft.

Investigation of momentum and heat transfer characteristics of Maxwell fluid cascading over a stretching sheet: A HAM approach

This paper presents a novel investigation into the intricate behaviour of momentum and heat transport phenomena in a non-Newtonian Maxwell fluid flowing over a stretching sheet. Incorporating thermal radiation Rd, magnetic fields M, buoyancy effects λT, and porous media K under convective boundary conditions the study unveils complex fluid behaviours. Energy equation has been obtained by incorporating non-uniform heat source/sink along with viscosity of the fluid as a function of temperature across the domain. Leveraging the Lie Scale transformation technique, the governing non-linear partial differential equations are converted into non-linear ordinary differential equations. With the aid of Homotopy Analysis Method (HAM), a semi-analytical technique, the solutions describing the physical phenomenon of the current model have been obtained. Further, the results are assessed through the graphical analysis of the velocity profile f′η, thermal profile θη, skin friction coefficient CfRe12, and Nusselt number NuRe−12. The obtained results using HAM shows good agreement with the existing literature. The present work offers practical implications for various engineering applications.

Numerical investigation of evaporation-induced flow around sessile droplets using a sharp-interface algebraic VOF approach

In this study, we numerically investigate the external gaseous flow around an evaporating sessile droplet, especially the interaction between different transport mechanisms of the evaporation-induced flow and evaporation dynamics. A sharp-interface algebraic volume-of-fluid (SA-VOF) solver which incorporates the Boussinesq approximation to deal with thermal and solutal buoyancy has been developed for direct numerical simulation of evaporating droplets in natural convection. Evaporation of a heptane droplet is first simulated to validate the developed solver, and the predicted evaporation rates show good agreement with experimental data. An evaporating sessile droplet on a heated substrate is then simulated through three distinct models to account for contributions from different transport mechanisms of the evaporation-induced flow, i.e. diffusion, the Stefan flow and natural convection. Extensive cases have been simulated at different gravity levels and environmental conditions to clarify the separate role of each mechanism. Results show that the convective flow can enhance evaporation of sessile droplets considerably at elevated substrate temperatures, accounting for up to 40.4% of total evaporation at the substrate temperature of 60 °C and the humidity of 36%. The contribution of the Stefan flow or natural convection in the evaporation process increases with the substrate temperature while stays almost independent of the environmental humidity. Additionally, minute details of the evaporation-induced flow at zero and normal gravity, including flow field, gas mixture density, vapor fraction and temperature distribution, are comparatively studied to reveal the complex characteristics of momentum, mass and heat transfer associated with droplet evaporation in natural convection.

Numerical assessment of the drag force and Nusselt number during droplet impingement onto a particle

The dynamics of droplet impingement onto solid particles play a crucial role in various engineering applications, yet a fundamental understanding of the intricate momentum and heat transfer characteristics within the processes remains unclear. In this work, we numerically investigate and quantify the drag force and Nusselt (Nu) number during the process using a volume of fraction model. After model validations, it is employed to simulate the processes of molten iron ore spreading over a coke particle for demonstration. The results show that the drag force exhibits rapid initial growth, followed by significant fluctuations marked by two peaks, ultimately decreasing to a low value. The Nu number undergoes a sharp ascent to an immediate peak, followed by a two-stage decline with varying rates. Furthermore, the effect of three key operating parameters is quantified. The comparative analysis unveils that a larger droplet size significantly contributes to an augmented drag force, especially during the first peak. The Nu numbers under various droplet sizes follow a similar trajectory, rising and then decreasing until the wetter surface reaches the maximum. The larger droplets show a slower Nu number decrease. A higher initial droplet position can remarkably increase the drag force and Nu number with more rapid fluctuations. Conversely, the effect of gas velocity under the symmetrical and steady flow field is limited and can be practically disregarded. The present work reveals the fundamental characteristics of momentum and heat transfer process during droplets impact particles.

Comprehensive study of tri-hybrid nanofluid flow in a vertical channel with Cu, Al2O3, and TiO2 nanoparticles via fractional dynamics and non-local kernel approach

Nanofluids and hybrid nanofluids enhance the transfer of heat with low nanoparticle concentration. Tri-hybrid nanofluids combine different nanoparticles (NPs) to further increase the performance of base fluids. Tri-hybrid nanofluids have significant uses in several industries, including electronic cooling, heat transport, biomedical engineering as well as energy storage systems. This study investigates the thermal performance of tri-hybrid nanofluid in the existence of a magnetic field and porous saturated space along with copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) NPs dispersed in base fluid, i.e. water (H2O) flowing through a vertical channel by convection. The resultant partial differential equations based on Atangana–Baleanu time-fractional derivative (having non-singular and non-local kernel) are solved using the Laplace transform along with the appropriate physical conditions. The Stehfest as well as Tzou’s numerical approaches are then utilized to compute the Laplace inverse, to check the validity of obtained solutions and to get the graphical representations of, concentration, energy, and velocity fields. The results show that tri-hybrid nanofluids have advanced thermal as well as momentum characteristics compared to nanofluids and hybrid nanofluids.

Numerical study of hybrid binary Al2O3-Cu-H2O nanofluid coating boundary layer flow from an exponentially stretching/shrinking perforated substrate with Cattaneo-Christov heat flux, heat source, suction and multiple slip effects

Modern coating systems are increasingly deploying nanomaterials which offer improved thermal performance. The optimization of these systems can benefit from more elegant fluid dynamic models of the coating process. Inspired by these advancements, the present investigation introduces a novel mathematical model to analyze the boundary layer transport in Al2O3-Cu-H2O hybrid binary nanofluid coating deposition on an exponentially stretching porous substrate (sheet). Lateral mass flux (suction) at the wall is also considered a heat source (generation) for hot spot manufacturing effects. To add further sophistication to the thermal conduction model, a non-Fourier approach is adopted which accurately incorporates thermal relaxation effects i.e. the Cattaneo-Christov heat flux (CCHF) model. The Tiwari-Das volume fraction nanoscale formulation is implemented for different combinations of Alumina (Al2O3) and Copper (Cu) metallic nanoparticles in an aqueous base fluid (H2O). Hydrodynamic wall and thermal slip are also included as they feature in coating processes. The fundamental equations governing mass, momentum, and energy conservation, along with the corresponding conditions at the wall (substrate) and free stream, are made dimensionless through suitable scaling similarity transformations. The resulting nonlinear coupled ordinary differential boundary value problem is subsequently addressed using the efficient MATLAB bvp4c routine. Special cases of the non-Fourier model are validated against published results, and the general model is further confirmed through validation using an Adams-Moulton 2-step predictor-corrector algorithm (AMPC). Furthermore, dual solutions of the generalized model are extracted and visualized. A comprehensive study of the effects of key thermophysical key parameters on momentum and thermal characteristics (velocity, temperature, skin friction and local Nusselt number) is conducted and solutions are visualized graphically. The computations show that higher temperatures are present with intensification in the thermal relaxation parameter (Cattaneo-Christov hyperbolic model parameter), which predicts therefore larger temperatures than the classical Parabolic heat conduction model using Fourier analysis. Effectively, thermal relaxation is responsible for finite heat wave propagation and produces more accurate estimations of heat transfer than the Fourier model. An increase in stretching parameter enhances the skin friction coefficient and elevates the local Nusselt number. As the thermal relaxation parameter increases, the temperature magnitudes corresponding to the first and second solutions are both enhanced as are thermal boundary layer thicknesses. An increase in wall suction induces an escalation in the first solution for velocity whereas it reduces the second solution velocity. Stronger wall suction suppresses temperatures. With increasing thermal slip, the boundary layer is cooled i.e. temperature plummets and thermal boundary layer thickness is decreased. Strong deceleration is induced with greater hydrodynamic (velocity) slip. Both first and second solutions for skin friction are elevated with shrinking whereas they are depressed with stretching. With greater velocity slip both the first and second solutions for skin friction are depleted with greater velocity slip for the shrinking case, whereas they are generally enhanced for the very strong stretching case. The computations offer some new insights into multi-physical thermal fluid dynamics of nanofluid-based coating systems.

Visit Nearby Halo Substructures Using LAMOST DR9 MRS Data

Based on the LAMOST DR9 Medium Resolution Spectra (MRS) catalog, combined with astrometries from Gaia DR3, we conducted an investigation into the substructures in the stellar halo to obtain their chemical and kinematic information. We employed the HDBSCAN algorithm in the (L z , E, L xy ) space for clustering and utilized Mahalanobis distance to merge the clustering results. Ultimately, within the LAMOST DR9 MRS catalog, we identified members of Gaia–Sausage–Enceladus (GSE), Helmi streams, and the high-α disk and in situ halo. Additionally, there are three clusters that cannot be correlated with known substructures. Based on their angular momentum (L z ) characteristics, we have tentatively named two of them High-L z -Cluster-1 (HLC-1) and High-L z -Cluster-2 (HLC-2), both exhibiting high angular momentum (L z ) features. The third cluster, owing to its extremely low L z , is termed the Low-L z -Cluster. Then detailed analysis about those substructures are executed including member stars’ identification and kinematic and chemical distribution. The resulting GSE member stars exhibit a well-defined metallicity distribution function with its peak at [Fe/H] ∼ −1.2, consistent with previous findings, and we found there appear to be some differences in the distribution on the V total–r gal plane between GSE and its included Splash component. Regarding Helmi streams, in the [Mg/Fe]–[Fe/H] plane we detected potential traces of the α-knee phenomenon at [Fe/H] ∼ −1.53. Finally, we tentatively provide the possible origin for the HLC-1 and HLC-2.

Utilizing Artificial intelligence to identify an Optimal Machine learning model for predicting fuel consumption in Diesel engines

This paper describes the utilization of artificial intelligence (AI) techniques to identify an optimal machine learning (ML) model for predicting dodecane fuel consumption in diesel combustion. The study incorporates sensitivity analysis to assess the impact levels of various parameters on fuel consumption, thereby highlighting the most influential factors. In addition, this study addresses the impact of noise and implements data cleaning techniques to ensure the reliability of the obtained results. To validate the accuracy of the predictions, the study performs several metrics and validation process, including comparisons with computational fluid dynamics (CFD) results and experimental data. Comprehensive comparisons are made among neural networks (NN), random forest regression (RFR), and Gaussian process regression (GPR) models, taking into account the complexity associated with fuel consumption predictions. The findings demonstrate that the GPR model outperforms the others in terms of accuracy, as evidenced by metrics such as mean absolute error (MAE), mean squared error (MSE), Pearson coefficient (PC), and R-squared (R2). The GPR model exhibits superior predictive ability, accurately detecting and predicting even individual data points that deviate from the overall trend. The significantly lower absolute error values also consistently indicate its higher accuracy compared with the NN and RFR models. Furthermore, the GPR model shows a remarkable speedup, approximately 1.7 times faster than traditional CFD solvers, and physically captures the momentum and thermal characteristics in a surface field prediction. Finally, the target optimization is assessed using the Euclidean distance as a fitness function, ensuring the reliability of predicted data.

Optical trapping capability of tornado circular Pearcey beams

We systemically investigate optical trapping capability of a kind of tornado waves on Rayleigh particles. Such tornado waves are named as tornado circular Pearcey beams (TCPBs) and produced by combining two circular Pearcey beams with different radii. Our theoretical exploration delves into various aspects, including the propagation dynamics, energy flux, orbital angular momentum, trapping force, and torque characteristics of TCPBs. The results reveal that the orbital angular momentum, trapping force, and torque of these beams can be finely tuned through the judicious manipulation of their topological charges (l 1 and l 2). Notably, we observe a precise control mechanism wherein the force diminishes with |l 1 + l 2| and |l 1–l 2|, while the torque exhibits enhancement by decreasing solely with |l 1 + l 2| or increasing with |l 1–l 2|. These results not only provide quantitative insights into the optical trapping performance of TCPBs but also serve as a valuable reference for the ongoing development of innovative photonic tools.

The equivalence principle for a plane gravitational wave in torsion-based and non-metricity-based teleparallel equivalents of general relativity

We study the energy–momentum characteristics of the plane “+”-polarized gravitational wave solution of general relativity in the teleparallel equivalent of general relativity (TEGR) and the symmetric teleparallel equivalent of general relativity (STEGR) using the previously constructed Noether currents. The current components describe energy–momentum locally measured by an observer if the displacement vector ξ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\xi $$\\end{document} is equal to the observer’s 4-velocity. To determine the non-dynamical connection in these theories, we use the unified “turning off” gravity principle. For a constructive analysis of the values of Noether currents and superpotentials in TEGR and STEGR, we use the concept of “gauges”. The gauge changing can affect the Noether current values. We study under what conditions the Noether current for the freely falling observer is zero. When they are established, the zero result can be interpreted as a correspondence to the equivalence principle, and it is a novelty for gravitational waves in the TEGR and STEGR. We highlight two important cases with positive and zero energy, which reproduce the results of previous works with a different approach for determining gravitational energy–momentum in the TEGR, and give their interpretation.

Orbital angular momentum splitter of light based on beam displacer

In recent years, the high-dimensional properties of the orbital angular momentum degree of freedom of light have attracted extensive attention. This degree of freedom has been studied and used in many scientific fields, especially in optical communication and quantum information. In order to fully utilize the high-dimensional properties of orbital angular momentum, non-destructive separation of different orbital angular momentum states has become a fundamental requirement. However, the existing orbital angular momentum beam-splitting systems either lack stability and cascade expansibility, or the properties of the separated orbital angular momentum states are seriously damaged, thus failing to participate in further interaction processes. In this work, we construct a miniature Mach-Zehnder interferometer based on the beam displacer, and design an orbital angular momentum beam splitter, thereby realizing the non-destructive beam splitting of orbital angular momentum mode. In the orbital angular momentum splitter, the theoretical energy loss is zero because there exists only total reflection of the beam. The beam in the miniature Mach-Zehnder interferometer passes through the same optical element, and the spatial deviation of the beam is small, so the orbital angular momentum beam splitter has good stability. In addition, because the separated orbital angular momentum state has the same propagation direction as the incident orbital angular momentum state, the beam splitter has good extensibility and is easy to use in cascade. Our research result is of great significance in using the orbital angular momentum as a high-dimensional degree of freedom in optical communication and other related fields.

Mathematical model analysis for hydromagnetic flow of micropolar nanofluid with heat and mass transfer over inclined surface

In this study, a mathematical model analysis is made to figure out the impacts of relevant thermophysical effects on the rates of micropolar nanofluid transport phenomena near an inclined exponentially stretching surface. The flow phenomena are described mathematically using partial differential equations and simplified to dimensionless ordinary differential forms via suitable transformation variables. The resulting nonlinear coupled differential equations are then solved by using the optimal homotopy analysis method and the validity of the method is verified in convergence and comparative analysis. The rates of linear momentum, angular momentum, heat exchange and mass diffusion characteristics are investigated against continuous variations of pertinent parameters. Graphical elucidations are preferred to present the results of the study in detail. It was found that the rate of heat exchange is intensified with increasing values of micropolar parameter, Soret number and forces of buoyancy. Also, the rate of couple stress grows for higher estimation of micropolar parameter, surface shrinking, angle of inclination and heat sink parameter values. Further, the wall shear stress is strengthened for increasing values of the micropolar parameter, Dofour number, Soret number, buoyancy forces, heat release, chemical reaction and thermophoresis effects. On the other hand, the Sherwood number is enlarged with higher values of surface stretching parameter, medium porosity, Dufour number, chemical reaction, forces of buoyancy, heat release and Schmidt number.

Influence of Planar Confinement on Momentum and Heat Transfer from a Blunt‐Headed Cylinder to Generalized Newtonian Fluids

AbstractThis study investigated the momentum and thermal characteristics of a blunt‐headed cylinder immersed in a stream of generalized Newtonian fluids (i.e., power‐law fluids) under various planar confinements. The flow and heat transfer characteristics were obtained by solving the constitutive equations with a finite‐element‐based solver for varying ranges of governing parameters. Reynolds number (Re = 1–40), Prandtl number (Pr = 5–100), power‐law index (n = 0.3–1.8), and blockage ratios (β = 2–40) were considered as the governing parameters for the study. Streamlines, drag coefficients, isotherm contours, and average Nusselt numbers were obtained as output parameters of the study. The local distribution of the pressure coefficient and Nusselt number are also presented to gain deep insight into the vicinity of the blunt‐headed cylinder. Shear‐thickening and shear‐thinning fluids exhibited an inverse trend for flow separation under planar confinements. The average Nusselt number exhibits a positive correlation with the Reynolds and Prandtl numbers while showing negative dependence on the power‐law index and blockage ratio. Overall, momentum and heat transfer show complex relationships with the governing parameters. The functional relationships are shown as correlations for flow‐separation Reynolds number, total drag force, and average Nusselt number on relevant dimensionless parameters for general applications.

Particle shape matters: Flow and heat transfer characteristics of nonspherical particles

The primary shape considered for the present numerical study is the spherical segment dissected from the spherical particle at an angle α from its vertical y-axis. The shape effect of the spherical segments on momentum and heat transfer characteristics are presented in terms of shape factor (ψ) spanning over the range of 0.424 (α = 300) ≤ ψ ≤ 0.996 (α = 1500) for Reynolds number, 1 ≤ Re ≤ 150. The results of drag, heat transfer coefficient, and streamlines have been compared with the closest shapes of spherical segment, i.e., cone (0.324 ≤ ψ ≤ 0.658) and short cylinder (0.541 ≤ ψ ≤ 0.872) to identify the role of the particle shape. The range of shapes has been correlated for drag and average Nusselt number as a function of Re, shape factor, ψ and particle longest chord length or base diameter to height ratio (1 ≤ dc/h ≤ 7.463).

Effectively modulating spatial vortex four-wave mixing in a diamond atomic system

Due to the spatial characteristics of orbital angular momentum, vortex fields can be applied in the fields of quantum storage and quantum information. We study the realization of spatially modulated vortex fields based on four-wave mixing in a four-level atomic system with a diamond structure. The intensity and spiral phase of the vortex field are effectively transferred to the generated four-wave mixing field. By changing the detuning of the probe field, the phase and intensity of the generated vertex four-wave mixing field can be changed. When the probe field takes a large detuning value, the spatial distribution of the intensity and phase of the vertex four-wave mixing field can be effectively tuned by adjusting the Rabi frequency or detuning value of the coupled field. At the same time, we also provide a detailed explanation based on the dispersion relationship, and the results agree well with our simulation results.

Crosstalk characteristics of orbital angular momentum of focused perfect vortex beam in atmospheric turbulence

The perfect optical vortex beam (POV) is a special kind of vortex beam, whose radius is independent of its orbital angular momentum (OAM) mode, but the atmospheric turbulence (AT) causes crosstalk between different topological charges, which is a serious challenge in OAM-based communication system. We establish a theoretical model with a turbulence suppression effect for deriving the spiral spectrum of a focused perfect optical vortex beam (FPOV) after propagation through anisotropic AT. Through numerical analysis, we simulate the behavior of FPOV under different turbulence and beam parameters to better understand the effect of the received probability and its corresponding modal crosstalk under various conditions. In addition, the simulation of AT uses the multi-phase screen method to verify the theoretical results. The results show that the changes in topological charge, wavelength, receiving aperture, beam waist, and hollow radius all have an influence on the received probability. Also, some strategies for selecting turbulence parameters to reduce modal crosstalk in anisotropic AT are also discussed. The focus would reduce the effect of turbulent aberrations on the signal OAM mode received probability, and the FPOV provided better performance than the POV, which may be useful in OAM-based free space optical communication.

Creation of galaxy-shaped vortex relief structures in azo-polymers with petal-like beams.

We demonstrate the formation of surface relief structures in azo-polymers which exhibit multiple spiral arms, through irradiation of a rotating petal-like beam formed by the coherent superposition of Laguerre-Gaussian modes with opposite handedness. Intriguingly, the fabricated relief structures reflect full geometric parameters of the irradiated petal beam, such as handedness, topological charge, initial azimuthal phase and even ellipticity, corresponding to azimuthal and polar angles along equator and meridian planes of an orbital Poincaré sphere. The handedness, or direction of rotation, of the fabricated structures with multiple spiral arms could be controlled via the rotation and polarization directions of the irradiating laser field. This effect highlights an exotic coupling between the optical intensity gradient induced mass transport of the irradiated material and the spin angular momentum characteristics of the irradiating optical field. The azimuthal orientation of the surface relief structures could also be tuned by altering the initial relative phase between the coherently superposed Laguerre-Gaussian modes with opposite handedness, constituting the irradiating petal laser field. This work offers new insights into fundamental interactions which occur between light and matter, and we believe, will pave the way towards advanced technologies, such as ultrahigh density optical data storage.