Angular Velocity Distribution Research Articles

Exploration of drag on the thin film of micropolar fluid flow within a permeable medium

Advances in thin film acquired many industrial applications because of their use in several products like electronic devices, magnetic recording media, LED, optical coating, etc. Additionally, thin film has an extensive role in the study of multiferroic materials and superlattices in quantum phenomena. Therefore, it is an urge to predict the importance of drag employing Darcy-Forchheimer on the thin film flow of micropolar liquid through an expanding plate embedding with a permeable medium. Moreover, the current model enriches by incorporating the impact of Soret because of the cross-diffusion process and the radiative heat. By using the appropriate transformed variables, the designed problem is distorted, and further, these sets of equations are handled numerically employing Runge-Kutta shooting technique. The computation is carried out by deploying in-house built-in function bvp4c in MATLAB. The significant operational behavior of the manipulated quantities is accessible graphically and deliberated in the discussion section. The important findings are elaborated as; the angular velocity distribution shows a greater deceleration for the increasing microrotation and the inertial drag effect. Further, the thermo-diffusion due to Soret also attenuates the concentration profile and the solutal thickness became thinner for the higher heavier species.

Integrated modeling of anisotropic neutron yields of classical and spherical tokamaks

Estimations of counting rates of neutron spectrometers in experiments on controlled fusion with magnetic confinement, as well as calculations of energy resolved flux densities of fusion neutrons from plasma to the walls of a reactor require spatial integration of the local, usually anisotropic function of the neutron source. The integrated modeling consists of three main stages. First, sources of fast particles in beam- or wave-heated plasma are calculated. The next stage deals with spatial, energetic, and angular velocity distributions of plasma ions. Finally, double differential rate coefficients of nuclear fusion reactions are computed. This article describes calculations of spatial distributions of nuclear fusion reaction rates in classical and spherical tokamaks and the anisotropy of the neutron yield and spectra. The results are based on analytical formulas for energetic and angular distributions of the local source of fusion products in plasma. Examples of energetic spectral densities of neutron fluxes on first walls are presented, as well as energy resolved counting rates of collimated neutron spectrometers for perpendicular and tangential lines of sight.

Investigation on unsteady fluid flow around an oscillating sphere-A numerical and analytical approach

This article presents the Investigation on unsteady fluid flow around an oscillating sphere-A Numerical and Analytical approach. The analytical expressions for angular velocity and temperature of the fluid around an oscillating sphere have been obtained in form of Bessel functions with suitable assumed boundary conditions. The numerical results in terms of angular velocity, temperature and pressure distribution for various values of the material parameters have been obtained using R-K method of 6th order with shooting methods with the help of MATHEMATICA ND solver. The influence of thermo-viscous flow parameters on angular velocity, temperature, pressure and drag on the boundary have been presented in form of tables and graphs. It may be noticed that the thermo-viscous effects are more predominant in the flow region around the boundary of the oscillating sphere. The R-K method with shooting method is the most powerful and elegant method to solve the governing equations related to the fluid dynamics problems. This method gives the accurate and valid results of highly complex coupled governing equations. The analytical results obtained are validated with this method in the present problem. The results obtained by this method gives more accurate, stable and converging to the analytical results. The numerical solutions of governing equations of present work have been obtained are compared with the existing analytical results and are found to be in excellent agreement. The present theoretical work will be hope fully for the better understanding of researchers and scientists and also it is useful in chemical and nuclear industries.

Measurement of acceleration and angular velocity of particles during a 3D silo discharge

Accurate measurement of the three-dimensional (3D) movement of discrete particles is crucial for comprehending complex granular rheology in silos. In this paper, the acceleration and angular velocity of particles in 3D silos are measured by using a spherical detector based on inertial technology and magnetic positioning technology. The acceleration of particles is the largest in the center of silos, which suggest that the resistance generated by friction and extrusion is the smallest. Surprisingly, the angular velocity distribution follows lognormal function except for particles near the outlet. The correlation between acceleration and angular velocity is opposite in different flow regions. It reveals for the first time that the extent to which the resultant force on the particles affects their rotational motion is related to the flow pattern. These results have practical significance for regulating the granular flow pattern and optimizing the structural design of silos.

Kinematic characteristics of elbow joint range of motion in elite Chinese freestyle swimmers with elbow pain during dry-land simulations of swimming strokes

ABSTRACT The aim of this study was to obtain quantitative data on elbow joint ROM in elite freestyle swimmers with EP in China. Of the 50 elite freestyle swimmers recruited, 41 completed all measurements during dry-land swimming stroke simulations. Elbow joint angle, velocity, and acceleration were measured using inertial measurement units. The RMSE/D was calculated to determine the elbow joint ROM deviation. Joint angle (3.33 ∘ –42.96 ∘ ), angular velocity (−364.15 to 245.69 ∘ / s ), and angular acceleration (−7051.80 to 1465.35 ∘ / s 2 ) were significantly different between the critical pain and healthy. The probability distributions of joint angle (15.47 ∘ ±14.54 ∘ ), angular velocity (2.41 ∘ ±111.06 ∘ / s ), and angular acceleration (1.93 ± 2222.6 ∘ / s 2 ) in the slight pain group were significantly different betweenhealthy and critical pain. The RMSE/D distributions of angular velocity (28.3%) and acceleration (21.48%) in the critical pain deviated from the healthy. The peak value-RMSE/D matrix model obtained proved that elbow ROM significantly differed between the elite freestyle swimmers with EP and the healthy. Angular velocity and acceleration indicate the weakness and negative influence of kinematics on patients with EP. Thus, Potential solutions are to constantly optimise freestyle swimming techniques and strengthen the arm muscles.

Dynamics of freely falling perforated disks

The dynamics of free-falling perforated disks within the moderate Reynolds number Rem regime (700<Rem<1400) are experimentally investigated in this paper, including translation and rotation dynamics. Four falling styles are analyzed, including spiral motion, Hula-Hoop motion, helical precession motion and spiral irregular motion. In contrast to spiral irregular motion, we group the other three motions as regular motions. The relative contribution of different dynamical effects (impulsive effect, Magnus effect and viscous effect respectively) is quantitatively determined. The contribution of impulsive effect is commonly ignorable during the descent, and Magnus effect plays a crucial role in horizontal oscillations. Vortex loads always dominate this dynamical process, and balance the gravity along the vertical direction. In the Frenet–Serret coordinate system, the contribution resulting from Magnus effect is relatively small to that of vorticity-induced fluid force. Hence, an alternative way to model this involved system is presented, which is based on the extended Kelvin-Kirchhoff equations. A Fast Fourier Transform (FFT) is performed on total hydrodynamics forces FHx and FHy. For regular motions with the dimensionless inertia ratio I∗≤1×10−3, sub-harmonic force components are identified in the frequency domain. However, the frequency ratio of high-frequency components and the dominant peak is no longer integer in spiral irregular motion. The azimuth distribution of angular velocity is counted in the Frenet–Serret coordinate system. For spiral irregular motion with the dimensionless inertia ratio I∗>1×10−3, no preferential alignment is observed and its distribution scatters, while those of regular motions are rather concentrated. The probability density functions (PDFs) of angular velocity components in spiral and Hula-Hoop motions share similar distributions, which indicates angular dynamics may decouple from translation dynamics in high Reynolds number regime under certain circumstances.

Motion of an active bent rod with an articulating hinge: exploring mechanical and chemical modes of swimming

Swimming at the microscale typically involves two modes of motion: mechanical propulsion and propulsion due to field interactions. During mechanical propulsion, particles swim by reconfiguring their geometry. When propelled by field interactions, body forces such as phoretic interactions drive mobility. In this work, we employ slender-body theory to explore how a bent rod actuator propels due to a mechanical mode of swimming via hinge articulations and due to a chemical mode of swimming via diffusiophoretic interactions with a solute field. Although previous theoretical studies have examined mechanical and chemical modes of swimming in isolation, the simultaneous investigation of both modes has remained unexplored. For the mechanical mode of swimming, our calculations, both numerical and analytical, recover Purcell’s scallop theorem and show that the bent rod actuator experiences zero net displacement during reciprocal motion. Additionally, we calculate the trajectories traced by a bent rod actuator under a non-reciprocal hinge articulation, revealing that these trajectories are influenced by the amplitude of the hinge articulation, geometric asymmetry, and the angular velocity distribution between the two arms of the bent rod actuator. We provide intuitive explanations for these effects using free-body diagrams. Furthermore, we explore the motion induced by simultaneous hinge articulations and self-diffusiophoresis. We observe that hinge articulations can modify the effective phoretic forces and torques acting on the bent rod actuator, either supporting or impeding propulsion. Additionally, during self-diffusiophoretic propulsion, reciprocal hinge articulations no longer result in zero net displacement. In summary, our findings chart a new direction for designing micron-sized objects that harness both mechanical and chemical modes of propulsion synchronously, offering a mechanism to enact control over trajectories.

MHD Stagnation-Point Flow and Heat Transfer in a Micropolar Fluid over an Exponentially Vertical Sheet

This paper examines the magneto hydrodynamic (MHD), stagnation-point flow and heat transfer caused by an exponentially stretching/shrinking vertical sheet and the presence of mixed convection (buoyancy effect) in a micropolar fluid. A set of variables is employed to transform the system of partial differential equations (PDEs) to ordinary differential equations (ODEs). The ODEs are then numerically solved in MATLAB software using BVP4c. There are a lot of agreements when compared to previous findings. The impacts of different parameters, such as micropolar, magnetic, mixed convection, radiation, temperature, and stretching/shrinking parameters are displayed graphically. It is found that contradictory phenomena between Micropolar and mixed convection for fluid velocity, angular velocity and temperature distribution profiles. The velocity profile at the vertical plate increases due to the increasing buoyancy, magnetic and radiation parameters. The particle rotation occurs in two phenomena for buoyancy and magnetic parameters and it is reversible for micropolar. The temperature of the fluid decreases with buoyancy and magnetic parameters.

Model of flow transportation of bulk cargo by vertical screw conveyors

The article considers the model of transporting bulk cargo by flow by vertical high-speed screw conveyors. The peculiarities of mutual movement of cohesive and fine cargoes, in particular, in the conditions of their layer-by-layer movement, are revealed. To analyze the stress-strain state of bulk cargo in the conditions of screw conveying, a special helical coordinate system was used, which made it possible to significantly simplify the solution of the problem. The dependences for describing the shape of the helical surface that restricts the flow of cargo under the condition of incomplete filling of the working space, the volume of the elementary sector of the flow and its center of gravity are derived. The use of the model of layer-by-layer material motion is substantiated, and the distribution of linear and angular velocities of particles in the flow and, accordingly, centrifugal forces is determined. It is shown that for vertical high-speed conveyors, the motion of the flow as a whole and its individual particles retains the laws of helical transporting, which makes it possible to use the model of a material particle with the given parameters to calculate the design and operating modes of the conveyor.

AN ALIGNED MAGNETIC FIELD IMPACT ON A MICROPOLAR FLUID BOUNDARY-LAYER FLOW ACROSS AWEDGE SUBJECTED TO SLIP EFFECTS: HOMOTOPY ANALYSIS METHOD

The heat transfer on laminar boundary-layer flow (BLF) of a micropolar non-Newtonian fluid (NNF) due to a wedge with an impact of an aligned magnetic field embedded in a porous stratum accompanied by an effect of velocity and thermal slips are scrutinized. The similarity transformations are utilized to modify the governing partial differential equations into nonlinear, coupled ordinary differential equations. Resultant equations were solved analytically by homotopy analysis method (HAM). The obtained results are shown graphically for angular momentum, velocity, and temperature distributions for emerging parameters like pressure gradient parameter, velocity, and thermal slip parameters, magnetic parameter, porosity parameter, material parameter, angle of inclination, and Prandtl number. The Nusselt number and skin-friction coefficient values are tabulated. It is noticed that extending values of the material variable suppressed the velocity. The impact of an angle of inclination and porosity parameter enhance the velocity profile. A velocity field was suppressed by larger values of velocity slip variable and temperature distribution declined at the surface and it begins to increase for a certain distance with rising values of thermal slip variable. The obtained results are compared with existing results in a limiting case which provides a good agreement.

Stokes Flow in Cylindrical Containers With Rotating Ends

The Stokes flow in cylindrical containers with rotating ends was studied. Based on the characteristics of the flow, the problem was reduced to the eigenvalue and eigensolution problem of Hamiltonian dual equations with the axial coordinate simulated as the time scale. By means of the completeness of the symplectic eigensolution space and the adjoint symplectic orthogonality relationship between the eigensolutions, the expansion of the solution to the problem was obtained, and the numerical method for calculating the expansion coefficients was given. In the cases of one-end rotating, two-end rotating at the same or opposite angular velocity, the velocity and stress distributions of the flow in the cylindrical containers with different aspect ratios (of the length to the radius), were investigated. The velocity and stress distributions, and the characteristics of the flows under different boundary conditions were revealed.

Calculating Microfield Angular Velocity Distribution in Plasma through Using Molecular Dynamics Simulation

Considering the importance of statistics related to microfields in the spectral line shapes in plasma, many researchers were interested in calculating statistical distributions related to microfields with different models and approximations. Analytical approaches and numerical simulation methods can be used to study the variations of the magnitude or the directions of the microfield. The aim of this work is the calculation of distributions of microfield angles and distributions of microfield angular velocities on ions in plasmas. The article briefly presents an overview of previous work and the molecular dynamics simulation (MDS) technique used in this work. We consider interaction between all ions of the plasma according to Debye potential, and we follow evolution of the positions and velocities of particles according to Verlet algorithm. The results present effects of temperature and ion densities on calculated distributions. We compare our results with those of an analytical model based on Holtsmark model at the temperature 105 K, the ionic density 2.1015 cm–3 and for Z = +2 and Z = +5. Another comparison is done with independent particles model (IPM) for ionic coupling parameter equal to 0.17. Our values of the most probable angular velocity are less than those of the analytical calculation; differences may be caused mainly by the choice of the interaction potential and interaction between all ions in the plasma.

Sharp turns and gyrotaxis modulate surface accumulation of microorganisms

The accumulation of swimming microorganisms at surfaces is an essential feature of various physical, chemical, and biological processes in confined spaces. To date, this accumulation is mainly assumed to depend on the change of swimming speed and angular velocity caused by cell-wall contact and hydrodynamic interaction. Here, we measured the swimming trajectories of Heterosigma akashiwo (a biflagellate marine alga) near vertical and horizontal rigid boundaries. We observed that the probability of sharp turns is greatly increased near a vertical wall, resulting in significant changes in the distributions of average swimming speed, angular velocity, and rotational diffusivity near the wall (a quantity that has not previously been investigated) as functions of both distance from the wall and swimming orientation. These cannot be satisfactorily explained by standard hydrodynamic models. Detailed examination of an individual cell trajectory shows that wall contact by the leading flagellum triggers complex changes in the behavior of both flagella that cannot be incorporated in a mechanistic model. Our individual-based model for predicting cell concentration using the measured distributions of swimming speed, angular velocity, and rotational diffusivity agrees well with the experiment. The experiments and model are repeated for a cell suspension in a vertical plane, bounded above by a horizontal wall. The cell accumulation beneath the wall, expected from gyrotaxis, is considerably amplified by cell-wall interaction. These findings may shed light on the prediction and control of cell distribution mediated by gyrotaxis and cell-wall contact.

Molecular Dynamics Simulations of Ion Extraction from Nanodroplets for Ionic Liquid Electrospray Thrusters

AbstractMolecular dynamics (MD) simulations were performed for ion extraction from electrospray thrusters to investigate relevant extraction processes numerically. To approximate the electrospray jet tip, a simulation domain consisting of 4-5 nm-sized ionic liquid droplets was used. The extracted ion angles and kinetic energies from EMI–BF4 (1-ethyl-3-methylimidazolium tetrafluoroborate) and EMI–Im (1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide) droplets were quantified by applying uniform electric fields of 1.3–1.7 V nm−1. The MD simulations are in great agreement with simulations presented in the literature and consistently show a greater preference for monomer emission than reported experimentally. At field strengths above 1.5 V nm−1, apparent droplet fracturing and breakup lead to an increase in ion angular velocity distributions. Greater mobility of EMI–BF4 ions than EMI–Im was also observed, indicative of the crucial role of cation-anion hydrogen bond strengths in ion extraction and beam composition between different propellants.

Experimental and Discrete Element Method Analysis of Galvanized Steel Scrap Particles Along and After an Inclined Chute

HIsarna is a novel ironmaking process with great raw materials versatility that is attractive for various secondary resources. Among the materials that can be recycled, there is steel scrap which is fed to the furnace bath through an inclined chute. The velocity distribution of the scrap particles along the chute affects the particles’ distribution on the liquid slag and, thereupon, the efficient operation of the reactor. In this study, the flow of steel scrap particles along an inclined chute with the same dimensions as those of the actual chute of the HIsarna plant is investigated experimentally and numerically. The simulations are validated using chute tip velocity and mass fractions collected at the different compartments of a sampling device. Translational and angular velocity distributions along and across the chute are reported, and the effect of different parameters are investigated. The impact of the shape of the particles on the simulation process is found to be negligible. The angular velocity distribution in cross‐sections of the chute exhibited a V‐shaped orientation, whereas the translational velocity displayed similar values across the cross‐sections. Moreover, translational velocity appeared to increase with increasing inclination angles, whereas angular velocity increased with decreasing batch size.

Dynamic behavior of oligomers formed by “十” shaped self-propelling agents

In recent years, active matter has attracted tremendous research interest. Active matter displays many phenomena, such as super-diffusion, huge fluctuation and collective motion. The shape of active agent plays a critical role in the self-assembly of active matter. Understanding the oligomers’ dynamics of active agents is the first step to study the self-assembly of massive agents. Here, we design a self-properlling particle with the “十” shape using the Hexbug robot and investigate the dynamics of oligomers composed of these particles. To track the position of particles, the top of the particles is marked by black cards with white dots in the center. We find that these particles can agglomerate together to form stable oligomers consisting of two, three, or four particles. We study the dynamics by analyzing the trajectory, mean-square displacement, angular velocity, angular velocity distribution and the curvature distribution. We find that the dynamics can be divided into two types. One is the combination of eccentric rotation with small circular radius and irregular translation, which occurs in the system with the zero resultant force and nonzero torque. The other is the eccentric rotation with a large circular radius, which appears in the system in which both the resultant force and torque are not zero. In addition, we find that the translational dynamics of oligomers displays a super diffusion on a short time scale, influenced by the confirguration of oligomers. Further, the larger torque and the smaller moment of inertia result in the bigger angle speed of oligomers. Moreover, we investigate the curvature distribution of the trimer and find that the faster the angle speed of the trimer, the bigger its curvature is.

Effect of suction on the MHD flow in a doubly-stratified micropolar fluid over a shrinking sheet

This paper investigates the influence of suction on the flow, heat and mass transfer characteristics over a permeable shrinking sheet immersed in a doubly stratified micropolar fluid. The model which consists of partial differential equations is converted into a set of nonlinear equations using similarity transformations and then solved using the bvp4c solver. Numerical results obtained are presented graphically for the distributions of velocity, angular velocity, temperature and concentration profiles within the boundary layer for various values of the magnetic parameter and wall mass suction parameter. It is visualized that the enhancement of suction parameter will increase the skin friction, heat transfer rate (local Nusselt number) and Sherwood number. It is also found that as the magnetic parameter increase, there is an increment in the skin friction while opposite results are obtained for the local Nusselt number and Sherwood number.

On the Origin of Geostrophic Liquid Cylinders in Rotating Sphere with Oscillating Inner Core

The effect of non-axisymmetric inertial waves on the zonal flow structure in a rotating spherical shell is studied experimentally. The wave source is the inner core, which performs circular oscillations in the equatorial plane. The case of positive frequencies that corresponds to the advanced core motion is considered. As a result of non-linear effects, a quasi-two-dimensional axisymmetric steady flow with a complex distribution of angular velocity is generated. The extrema in the velocity profile are equivalent to the nested liquid geostrophic cylinders, which appearance is due to the interaction of the inertial waves within a viscous boundary layer. One of the extrema is associated with the critical latitude at the core boundary, where the inertial waves are excited. With an increase in the oscillation frequency, the position of this extremum gradually shifts to the rotation axis. Additional geostrophic circulation occurs close to the points where the inertial wave reflects from the cavity boundary.

Enhanced transport properties and its theoretical analysis in two-phase hybrid nanofluid

This study explores the issue of micropolar fluids and heat transfer in a hybrid nanofluid through a moving thin needle with prescribed surface heat flux. Here, SWCNT and MWCNT are referred to as hybrid nanoparticles, and Engine oil and Refrigerant-134A as a working fluid. Similarity transformation is implemented to acquire the similarity equations, and then numerically solved by utilizing the shooting technique bvp4c function. Hybrid nanofluids enhance the heat transfer coefficient when their concentrations and nanoparticle volumes increase. The graphical results are made for different involved parameters such as material parameter, micro-gyration parameter, moving parameter, and index parameter. It is found that the heat transfer and friction drag are improved for hybrid nanofluid than nanofluids. It is further seen that increase in the size of the needle axial and angular velocity and temperature distribution diminishes.

Исследование движения несжимаемого газа в вихревом теплогенераторе

The article presents the results of the performed analytical and experimental studies of the hydrodynamics of the translationalrotational motion of a viscous incompressible gas flow in the working space of a vortex heat generator of variable geometry, analytically determined the dependences of the effect of device performance, confuser opening angles, confuser channel width on the hydrodynamic parameters of the device and, as a consequence, its energy efficiency. The degree of energy efficiency of the swirler screw for the operation of a vortex heat generator at various loads on the working path has been experimentally estimated, according to the Euler number EUc. It has been proven that the energy efficiency of its operation is on average 35% higher when the swirler screw is installed. The influence of the geometry of the nozzle on the axial symmetry and smoothness of the flow of incompressible gas in the vortex chamber is investigated. It was found that the specified indicator is most satisfactory for a nozzle with a rectangular cross-section. The distribution of the temperature field of a moving incompressible gas along the height of the vortex chamber is investigated depending on the taper angle. The distribution of angular velocities along the axis of the flow swirler is investigated at various values of productivity. It was found that the angular velocity decreases according to the law of potential fluid flow. A mathematical model has been developed to optimize the operating modes and parameters of the vortex heat generator. A software block was built based on the mathematical package MathCAD version 11 for the implementation of the developed mathematical model. An optimal design of a vortex heat generator with a variable geometry of the working space has been developed, which has been tested in laboratory conditions. Laboratory studies have proven its high energy efficiency at the level of modern standards and the feasibility of using the device for heating buildings and structures in industry and the domestic sector. Keywords: incompressible gas, hydrodynamics of an incompressible gas flow, vortex motion, mathematical model, equation of motion, continuity equation, vortex heat generator, thermal energy, cavitation, turbulence, vortex zone, MathCAD package.