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The paper gives a glimpse on the problem of the transverse force on a vortex, its proper determination in general and the role in the process of quantum vortex nucleation. Investigation of this problem is an essential part of the scientific heritage of Joe Vinen as an experimentalist and a theoretician. [ABSTRACT FROM AUTHOR]

In the process of table tennis man-machine sparring, the ball will rotate when it collides with the racket/table, which will cause the sphere to deviate due to the influence of the Magnus force. Therefore, it is difficult to meet the requirements of accurate trajectory prediction of table tennis robot. Trajectory prediction and rotation measurement technology can help improve the robot's ability of prediction and striking. In order to help researchers in this field understand the research methods and existing technologies of table tennis trajectory prediction and rotation measurement, the new developments in the research of table tennis trajectory prediction and rotation measurement are reviewed. After reclassifying and sorting out the research results based on the research achievements in this field in recent years, the advantages and disadvantages of different methods are analyzed and the key issues are sorted out. Finally, the future research trend of table tennis trajectory prediction and rotation measurement is prospected. [ABSTRACT FROM AUTHOR]

• Magnus force on cylinder or sphere in a shear-thinning fluid is investigated. • Magnus force reduces compared with that in a Newtonian fluid. • Shear viscosity sensitive functions are introduced to analyze this force reduction. • A relationship is proposed to quantify Magnus force reduction for small Re. This study aims to investigate the impact of fluid shear-thinning on the Magnus forces acting on a rotating cylinder or a sphere immersed in an unbounded flow using direct numerical simulation. The Carreau model is employed to represent the shear-thinning fluid, with the considered Reynolds number (Re) ranging from 0.01 to 100, Carreau number (Cu) from 0 to 100, power-law index (n) from 0.1 to 1, and viscosity ratio (β) from 0.001 to 0.5. The rotation rate (α) is fixed at 6. A characteristic Reynolds number, Re c , based on a viscosity evaluated at the characteristic shear rate, γ ˙ α = α U ∞ / 2 a , is introduced. It is found that, at a constant Re c , compared to that in a Newtonian fluid, the Magnus force exerted on the rotating cylinder or sphere in the shear-thinning fluid is reduced. This reduction results from the difference in viscosity distribution between the upper and lower sides of the cylinder or sphere. Furthermore, our analysis demonstrates that the logarithmic reduction in the Magnus force coefficient can be expressed as a linear combination of the logarithm of the strain rate difference and the logarithm of the shear strain rate sensitive function at two limit states, Cu →0 or Cu →∞. This work may be helpful to deepen the understanding of complex rheological behavior encountered in swirling flow hydrodynamics. [ABSTRACT FROM AUTHOR]

This study analyzed the characteristics of pitched baseballs from TV broadcast videos to understand the effects of the Magnus force on a pitched-baseball trajectory using aerodynamic theory. Furthermore, an automatic measurement and analysis system for pitched-baseball trajectories, ball speeds, and spin rates was established, capturing the trajectory of the baseball thrown by the pitcher before the catcher catches it and analyzing its related dynamic parameters. The system consists of two parts: (1) capturing and detecting the pitched baseball in all frames of the video using the YOLOv3-tiny deep learning algorithm and automatically recording the coordinates of each detected baseball position; (2) automatically calculating the average speed and spin rate of the pitched baseball using aerodynamic theory. As the baseball thrown by the pitcher is fast, and live-action TV videos like sports and concerts are typically at least 24 fps or more, this study used YOLOv3-tiny algorithm to speed up the calculation. Finally, the system automatically presented pitching data on the screen, and the pitching information in the baseball game was easily obtained and recorded for further discussion. The system was tested using 30 videos of pitched baseballs and could effectively capture the baseball trajectories, throw points, catch points, and vertical displacements. Compared with the values from the TV broadcast, the average errors on the calculated ball speed and spin rate were 1.88% and 7.51%, respectively. Using the ratio of the spin rate and ball speed as a parameter to analyze the pitching state of the pitcher's four-seam fastball in the Nippon Professional Baseball and Major League Baseball matches, it was observed that when this ratio increased, the Magnus displacement of the ball increased, thereby decreasing its late break. Therefore, the developed system provides scientific pitching data to improve the performance of baseball pitchers. [ABSTRACT FROM AUTHOR]

This study analyzed the characteristics of pitched baseballs from TV broadcast videos to understand the effects of the Magnus force on a pitched-baseball trajectory using aerodynamic theory. Furthermore, an automatic measurement and analysis system for pitched-baseball trajectories, ball speeds, and spin rates was established, capturing the trajectory of the baseball thrown by the pitcher before the catcher catches it and analyzing its related dynamic parameters. The system consists of two parts: (1) capturing and detecting the pitched baseball in all frames of the video using the YOLOv3-tiny deep learning algorithm and automatically recording the coordinates of each detected baseball position; (2) automatically calculating the average speed and spin rate of the pitched baseball using aerodynamic theory. As the baseball thrown by the pitcher is fast, and live-action TV videos like sports and concerts are typically at least 24 fps or more, this study used YOLOv3-tiny algorithm to speed up the calculation. Finally, the system automatically presented pitching data on the screen, and the pitching information in the baseball game was easily obtained and recorded for further discussion. The system was tested using 30 videos of pitched baseballs and could effectively capture the baseball trajectories, throw points, catch points, and vertical displacements. Compared with the values from the TV broadcast, the average errors on the calculated ball speed and spin rate were 1.88% and 7.51%, respectively. Using the ratio of the spin rate and ball speed as a parameter to analyze the pitching state of the pitcher’s four-seam fastball in the Nippon Professional Baseball and Major League Baseball matches, it was observed that when this ratio increased, the Magnus displacement of the ball increased, thereby decreasing its late break. Therefore, the developed system provides scientific pitching data to improve the performance of baseball pitchers.

A two-dimensional (2D) computational model for simulation of incipient sediment motion for non-cohesive uniform and non-uniform particles on a horizontal bed was developed using the Discrete Element Method (DEM). The model was calibrated and verified using various experimental data reported in the literature and compared with different theories of incipient particle motion. Sensitivity analysis was done and the effects of relevant parameters were determined. In addition to hydrodynamic forces such as drag, shear lift and Magnus force, the particle-particle interaction effects were included in the model. The asymptotic critical mobility number was evaluated for various critical particle Reynolds numbers ( R ∗ ) in the range of very small and very large R*. The obtained curve is classified into four regions. It was found that in the linear region, the drag force has the principal role on the initiation of motion. Moreover, the critical mobility number is independent of particle diameter. A procedure for estimating the critical shear velocity directly from the information on particle diameter and roughness height was developed. Finally, the mechanism of incipient motion for the different regions was studied and the effect of different forces on the incipient particle motion was obtained. It was found that the maximum effects of lift and Magnus forces were, respectively, less than ten and twenty percent of the total force. The drag force, however, was typically the dominant force accounting for majority of the net hydrodynamic force acting on sediment particles at the onset of incipient motion. [ABSTRACT FROM AUTHOR]

Magnetic skyrmion (MS), a vortexlike region with reversed magnetization in nanomagnets, has recently emerged as an exciting development in the field of spintronics. It has a number of beneficial features, including remarkably high stability, ultralow depinning current density, and extremely compact size. Due to these benefits, skyrmions have generated great interest in the design of spintronic memory. In this paper, we evaluate the use of skyrmion-based memory as a last-level cache for general-purpose processors. In the skyrmion-based memory structure, data can be densely packed as multiple bits in a long magnetic nanotrack. Write operations are performed by injecting a spin-polarized current in the nanotrack. Since multiple skyrmions (each representing a bit) are packed into a single nanotrack, they need to be accessed by shifting them along the nanotrack with a charge current passing through a spin-Hall metal (SHM). We identify the following key challenges associated with MS-based cache design: 1) the high-current requirements for skyrmion nucleation limit the density benefits offered by these structures, since the transistor supplying write currents is the limiting factor that determines the bit-cell area; 2) the proposed nanotrack structure results in significant performance overheads due to the latency arising from the shift operations; 3) the skyrmions move toward the edge of the nanotrack during shift operations owing to the Magnus force. Hence, an additional idle operation time is required to relax skyrmions back through the repulsive force from the edge; and 4) to avoid annihilation of skyrmions from the edge, the duration and the current density of the shift operation have to be well controlled. To overcome these challenges, a multi-bit skyrmion cell with appropriate peripheral circuit is proposed, considering the heterogeneity in the read/write characteristics. The density benefits are explored by performing the layout of different multi-bit cells. We perform a systematic device-circuit-architecture co-design to evaluate the feasibility of our proposal. Our experiments demonstrate the potential of, and the challenges involved in, using skyrmion-based memory as last-level caches. [ABSTRACT FROM AUTHOR]

To accurately predict the probabilities of impact damage to aircraft from runway debris, it is important to understand and quantify the aerodynamic forces that contribute to runway debris lofting. These lift and drag forces were therefore measured in experiments with various bodies spun over a range of angular velocities and Reynolds numbers. For a smooth sphere, the Magnus effect was observed for ratios of spin speed to flow speed between 0.3 and 0.4, but a negative Magnus force was observed at high Reynolds numbers as a transitional boundary layer region was approached. Similar relationships between lift and spin rate were found for both cube- and cylinder-shaped test objects, particularly with a ratio of spin speed to flow speed above 0.3, which suggested comparable separation patterns between rapidly spinning cubes and cylinders. A tumbling smooth ellipsoid had aerodynamic characteristics similar to that of a smooth sphere at a high spin rate. Surface roughness in the form of attached sandpaper increased the average lift on the cylinder by 24%, and approximately doubled the lift acting on the ellipsoid in both rolling and tumbling configurations. [ABSTRACT FROM AUTHOR]

The trajectory of a soccer ball, kicked with a spin to curve it into the goal, is strongly influenced by aerodynamic factors such as the Magnus force. Several studies using a wind-tunnel and high-speed cameras have investigated the Magnus force acting on a spinning soccer ball. However, the exact effect of the Magnus force on the trajectory of a spinning soccer ball in free flight remains unclear. This study set out to use an optical three-dimensional motion-capture system to record the details of the flight of such a spinning soccer ball. The maximum curvature of the ball’s trajectory occurred in the middle of its flight. The sideways-directed Magnus force acting on the ball decreased as the ball’s speed decreased during the entire flight. Thus, it was concluded that the deflection of the trajectory of the ball decreases as the sideways-acting force decreases throughout the flight.

The aerodynamic forces acting on a baseball are those produced by the contact between the ball and the air, and are defined by the initial conditions of the pitch. It is well known that such forces determine the changes from the typical parabolic ballistic trajectory, either in the direction of the movement of the ball (drag force), or producing a lift or lateral deflection (Magnus and seam forces). The drag and Magnus effects have been widely studied and there are many references about their nature and the trajectory they produce, which is predictable. This has led to most baseball research being related with spinning pitches. On the other hand, there is the unpredictable motion of a knuckleball, whose erratic trajectory accompanied by a poor understanding of the forces produced by the asymmetry of the seams had markedly limited research about it until the beginning of this century. However, nowadays interest in the knuckleball is resurfacing. Data collected by wind tunnel experiments and real pitches have motivated researchers to analyze the phenomenon and build models that try to predict the motion of the ball. In this work we aim to provide the reader some basic ideas on aerodynamic forces through a combination of experimental results, phenomenological and dimensional analysis, with special focus on new advances on the seam effects of a knuckleball pitch. In addition, we discuss possible ways to extend the existing models about the seam forces. Finally, we summarize from the literature some methods regarding the reproduction and reconstruction of baseball trajectories from aerodynamic forces and discuss their application as well.

In this study, three-dimensional baseball kinematics are described including spin characteristics batted toward the left field (same field), center field, and right field (opposite field) in baseball. The study also discusses the effects of these kinematics on the flight distance. Six collegiate male baseball players performed free-batting and were instructed to hit the ball as far as possible. The balls just before, at, and after bat-ball impact were recorded with three high-speed video cameras. Eighty-one trials (same field: 25 trials, center field: 30 trials, and opposite field: 26 trials) were analyzed, and the ball kinematics among the three hitting directions were compared. Although there were no significant differences in the initial velocities and launch angles along the vertical plane of batted balls for the three hitting directions, the flight distance for the opposite field was significantly shorter than that for the other fields. The magnitude of the side spin components for the opposite field was significantly greater than that for the other fields. We conjecture that the balls batted toward the opposite field experienced a larger Magnus force along the horizontal direction; moreover, the trajectories were relatively more curved than in the cases towards the other fields. Therefore, a straight-line distance to the batted ball landing point in the opposite field tended to be shorter despite the similar initial velocity and launch angle. The results demonstrated that the spin characteristics, especially the side spin component, were different for different batting directions, and indicated that these characteristics affected the ball trajectory and flight distance. [ABSTRACT FROM AUTHOR]

Deep spiking neural networks (SNNs) have emerged as one of the popular architectures in complex pattern recognition and classification tasks that can be enabled by low-power neuromorphic hardware. However, hardware implementation of such algorithms using conventional CMOS devices is area expensive and energy inefficient. This is owing to the fundamental mismatch between the underlying neuromophic computations and the CMOS transistors along with energy consumption involved in synaptic memory-access operations. Hence, there is a need for novel “neuro-mimetic” devices offering a direct mapping to synaptic and neuronal functionalities together with the possibility of providing in situ synaptic storage. Magnetic skyrmions have recently been proposed as a promising alternative for next-generation information carrier due to remarkably high stability, ultra-low depinning current density, and extremely compact size. In this paper, the design of skyrmion-based devices to emulate biological synapses and neurons is explored, and skyrmionic synapse-based crossbar architectures driving skyrmionic neurons are proposed. We perform a systematic device-circuit-architecture co-design for digit recognition with the MNIST handwritten digits dataset to evaluate the feasibility of our proposal. The device-to-system simulations indicate that the proposed skyrmion-based devices in deep SNNs can potentially achieve two orders of magnitude improvement in energy consumption over an optimized CMOS implementation at a 45 nm technology node. [ABSTRACT FROM AUTHOR]

In this work, a method to reconstruct trajectories by obtaining the initial conditions, velocity and angular velocity, from spinning throws is designed. It is based on considering Magnus effect can be separated from rest of forces that define the dynamics of the ball, such assumption is supported by an energetic analysis. Thus, the methodology consists in solving the two-point boundary value problem (BVP) of the movement equations without Magnus force and then adding its effect. We found that only three points (ball positions as functions of time) of a trajectory are necessary to characterize it, and consequently to solve the three-point BVP. This result is applied in an algorithm based on the shooting method, which obtains the initial conditions of synthetic trajectories by minimizing the distance between points of the original trajectory and those of the proposed trajectory, with high accuracy in a short time. [ABSTRACT FROM AUTHOR]

In this paper, the Magnus force induced by a disk-type, spinnable autonomous underwater vehicle (AUV), i.e., autonomous underwater helicopter (AUH), was predicted to promote the spinning AUH moving away from a deep-sea region with temporary and shockable ocean current. The simulation technique of the ANSYS-CFX solver based on viscous computational fluid dynamics (CFD) was employed to analyze the hydrodynamic performance of the spinning AUH and its high-speed propellers in uniform flow conditions. The behavior of the spinning AUH in currents can obviously alter the pressure distribution on both sides of the disk-shaped hull form, resulting in a differential pressure force in the horizontal plane, i.e., Magnus force. The simulation results show that this induced force can enable an AUH at 1 knot service speed to successfully move away from a sudden, transient, and/or steady, uniform ocean current region with inflow velocities of 1–2 knots in deep-sea conditions. The Magnus force induced by symmetrically configurated propeller couple force can be more efficient and effective at driving the AUH’s escape from the current spoiler zone than driving the AUH using the two high-revolution propellers directly. A suitable mechanical power energy-saving matching point integrating the AUH and symmetric propulsion was determined to compare the proposed method and two conventional methods for AUH escape from currents. The comparison results prove that the proposed method is effective and efficient. This study provides a significant reference for the interdependent relationship between the effective spinning speed of an AUH, subject to couple force, controlled propeller revolution, AUH speed, and battery capacity, and the range of ocean currents.

The phenomenon of drift motion of single-domain ferromagnetic particles induced by the Magnus force in a viscous fluid is studied analytically. We use a minimal set of equations to describe the translational and rotational motions of these particles subjected to a harmonic force and a non-uniformly rotating magnetic field. Assuming that the azimuthal angle of the magnetic field is a periodic triangular function, we analytically solve the rotational equation of motion in the steady state and calculate the drift velocity of particles. We study in detail the dependence of this velocity on the model parameters, discuss the applicability of the drift phenomenon for separation of particles in suspensions, and verify numerically the analytical predictions. [ABSTRACT FROM AUTHOR]

This paper derives the non-inertial terms, also referred to as fictitious forces, for aero-ballistic cases using an Eulerian approach. These cases display unsteady rates of change in acceleration in all six degrees of freedom. Six fictitious forces are identified in the momentum equation. Their origin and nature of these forces are elaborated upon. As shown in previous work, the continuity and energy equations remain invariant. The non-inertial boundary layer equations are derived to determine the effect of fictitious forces in the near-wall region. Through an order of magnitude analysis it was determined that none of the fictitious forces cancels out. It will therefore have an influence on the boundary layer properties. [ABSTRACT FROM AUTHOR]

Spin bowling is generally coached using a standard technical framework, but this practice has not been based upon a comparative biomechanical analysis of leg-spin and off-spin bowling. This study analysed the three-dimensional (3D) kinematics of 23 off-spin and 20 leg-spin bowlers using a Cortex motion analysis system to identify how aspects of the respective techniques differed. A multivariate ANOVA found that certain data tended to validate some of the stated differences in the coaching literature. Off-spin bowlers had a significantly shorter stride length (p = 0.006) and spin rate (p = 0.001), but a greater release height than leg-spinners (p = 0.007). In addition, a number of other kinematic differences were identified that were not previously documented in coaching literature. These included a larger rear knee flexion (p = 0.007), faster approach speed (p < 0.001), and flexing elbow action during the arm acceleration compared with an extension action used by most of the off-spin bowlers. Off-spin and leg-spin bowlers also deviated from the standard coaching model for the shoulder alignment, front knee angle at release, and forearm mechanics. This study suggests that off-spin and leg-spin are distinct bowling techniques, supporting the development of two different coaching models in spin bowling. [ABSTRACT FROM AUTHOR]

Asymmetric liquid–liquid droplet heating mechanisms differ from the more commonly studied and better understood symmetric liquid–gas mechanisms. In this work, we simulate two-dimensional low Weber number droplet heating in developing low Reynolds number liquid boundary layers. Of particular interest are the influences of Weber, Prandtl, and Reynolds number magnitudes on the system evolution. We perform simulations with a coupled Eulerian–Lagrangian interface capturing methodology – the Lagrangian volume of fluid – alongside an Eulerian solver for the Navier–Stokes equations that provides the spatial and temporal evolution of the temperature and velocity fields for the droplet and the surrounding fluid. Our results show droplet rolling induced by the velocity boundary layer modifies the temperature field in and around the droplet. Conduction negates the thermal influence of rolling in low Prandtl number droplets, but modifies the continuous phase temperature field. The Magnus force separates the droplets from the heated surface, decreasing their heating rate. These results establish the fundamentals of asymmetric liquid–liquid droplet heating in developing boundary layers: it is necessary to include the Magnus force in physically representative near-wall droplet heating models, and resolution of near-droplet temperature gradients may be necessary in situations with temperature dependent interface processes. [ABSTRACT FROM AUTHOR]

There are some reports that the Magnus force becomes negative at some situation in wind tunnel test. If so, there is possibility of a variety of curves using change of the direction of the Magnus force. PIV measurements of a flying table tennis ball were conducted to confirm whether a similar phenomenon was observed in real flight. A high-speed camera with a frame rate of 10k fps was used to capture the instantaneous flow field of the flying ball. The imaging region was 210 mm × 210 mm. The Reynolds number was approximately 6.5 × 10 4 , which corresponds to a smash in table tennis. A coordinate transformation of the ball's fixed coordinate system captured the wake motion of non-rotating and rotating balls. In the non-rotating condition, the averaged velocity field of the ball was observed to be symmetric, whereas, in the rotating condition, it was asymmetric, which shows the Magnus effect. At spin parameter is 0.65, the Magnus force becomes zero to indicate the appearance of the negative Magnus force. These observations quantitatively agree with the wind tunnel test. [ABSTRACT FROM AUTHOR]

An atom consists of a nucleus containing Z protons and N neutrons surrounded by Z electrons. These electrons are arranged in a sequence of symmetric patterns called shells with structure determined by the balance of the forces on the electron cores. These forces include electrostatic and centrifugal force as well as magnetic and gyroscopic force related to the angular momentum of the spinning electron core. The resulting patterns involve layers of shells, or two equal subshells, of nested concentric polygons each with an odd number of sides and with each vertex of a polygon occupied by an electron core when the subshell is complete. In the stationary state of an atom, the electron cores do not move but. are subjected to a virtual orbital motion with respect to primordial fluid flowing past them due to the field of a linear vortex associated with each electron core. [ABSTRACT FROM AUTHOR]

The effect of planar defects on the Magnus force in type-II superconductors is studied. It is shown that the deformation of the vortex due to the presence of a planar defect leads to a local decrease in the mean free path of electrons in the vortex. This effect reduces the effective Magnus coefficient in normal direction to the planar defect, leading to an anisotropic regime of the Hall effect. The presented developments here can qualitatively explain experimental observations of the anisotropic Hall effect in high- T superconductors in the mixed state. [ABSTRACT FROM AUTHOR]

The principal building block of the atomic nucleus is the deuteron which is formed by the addition of a neutron to a proton with both spin vectors parallel and directed along the line of centers, which is also the axis of a linear vortex in a primordial ideal fluid filling all space as postulated by the hydrodynamic theory of particles and fields previously published in this journal. Two deuterons with opposite spin vectors lying on the same axis can combine to form an alpha particle (helium nucleus). Many nuclei consist of compact clusters of alpha particles with parallel axes giving rise to atomic mass numbers divisible by 4, which are called magic numbers because these nuclei are unusually stable and abundant. There is a repulsive magnetic force and a repulsive Magnus force between deuterons with spin vectors parallel and orthogonal to the line of centers, but when the spin vectors are antiparallel there is an attractive magnetic force and an attractive Magnus force between the deuterons. As a result deuterons tend to assemble into flat layers with deuterons located at the vertices of concentric polygons with odd numbers of sides (3, 5, 7, etc.) centered on a single deuteron on an axis of rotational symmetry. A similar layer of deuterons with opposite spin vectors will be located beneath the first layer to give a sequence of nested polygons with alpha particles at the vertices. [ABSTRACT FROM AUTHOR]

Highlights: [•] A model for motion of spinning fertiliser grains on a concave spinning disc with radial straight vanes was developed. [•] A three dimensional ballistic model that takes into account spin of fertiliser grains was developed. [•] Simulations indicate a major effect of fertilizer particle spin on their landing position. [Copyright &y& Elsevier]

We study the Thiele equation for current-induced motion in a skyrmion lattice through two soluble models of the pinning potential. Comprised by a Magnus term, a dissipative term and a pinning force, Thiele’s equation resembles Newton’s law but in virtue of the topological character to the first, it differs significantly from Newtonian mechanics and because the Magnus force is dominant, unlike its mechanical counterpart—the Coriolis force—skyrmion trajectories do not necessarily have mechanical counterparts. This is important if we are to understand skyrmion dynamics and tap into its potential for data-storage technology. We identify a pinning threshold velocity for the one-dimensional pinning potential and for a two-dimensional attractive potential we find a pinning point and the skyrmion trajectories toward that point are spirals whose frequency (compare Kepler’s second law) and amplitude-decay depend only on the Gilbert constant and potential at the pinning point. Other scenarios, e.g. other choices of initial spin velocity, a repulsive potential, etc are also investigated.

Abstract: The Magnus effect on a prototype model soccer ball rotating perpendicular to the flow direction at Reynolds numbers in the range of was investigated by means of aerodynamic force measurements and of a flow field survey. Experiments were performed using a rear sting support where the soccer ball was split into two halves that were driven by a motor inside of them. In the non-rotating state the variation of force coefficients with Reynolds number and boundary layer separation points are within the range that is found for real soccer balls. In the rotating-state, considerable changes of the mean force coefficients with Reynolds number and spin parameter occurred, which can be attributed to the altered boundary layer separation. These changes also lead to significant changes of size and deflection of the wake zones in the lateral direction. A negative Magnus effect occurs in the critical Reynolds number range. Positive Magnus force is induced when the boundary layer is either laminar or turbulent on both sides of the rotating model soccer ball. [Copyright &y& Elsevier]

A newly developed procedure for predicting the growth of deposits on the fuel rods of a water-cooled water-moderated reactor under coolant boiling conditions is described. The results obtained from an experimental validation of the procedure carried out for fuel assemblies at different stages of their operation in a vessel-type boiling-water reactor are presented. It is shown on the basis of experimental data that the deposits forming on the fuel rods in a boiling-water reactor consist mainly of copper and iron. Copper exists in dissolved form and precipitates in pores between the particles of iron compounds, and the thickness of deposits is determined by the particles of iron corrosion products themselves. The corrosion products incipience and growth processes were investigated, and the effect of deposit formation from fine iron particles on fuel rod claddings operating under coolant boiling conditions was predicted theoretically and revealed experimentally. Relatively large particles moving along a fuel rod cannot penetrate into the laminar sublayer due to the effect of Magnus force on them. Based on the results of theoretical and experimental investigations, recommendations on decreasing the content of iron corrosion product particles in transient operating modes of boiling water reactors are worked out. The method of very fast decrease of pressure at low levels of reactor power worked out on a VK-50 reactor makes it possible to remove relatively large particles of shutdown corrosion products to the coolant purification system while keeping them from depositing on the fuel rods. With the use of this routine operation, matters concerned with radiation safety and durability of fuel assemblies in boiling light-water reactors are solved in a more efficient manner. [ABSTRACT FROM AUTHOR]

In this paper, an analytical and numerical study of the three-dimensional equations describing the motion through the air of a spinning ball is presented. The initial analysis involves constant drag coefficients, but is later extended to involve drag varying with the spin ratio. Excellent agreement is demonstrated between numerical, analytical and experimental results. The analytical solution shows explicitly how the ball's motion depends on parameters such as ball roughness, velocity and atmospheric conditions. The importance of applying three-dimensional models, rather than two-dimensional approximations, is demonstrated. [ABSTRACT FROM AUTHOR]

Advances in the versatile design and synthesis of nanomaterials have imparted diverse functionalities to Janus micromotors as autonomous vehicles. However, a significant challenge remains in maneuvering Janus micromotors by following desired trajectories for on-demand motility and intelligent control due to the inherent rotational Brownian motion. Here, we present the enhanced and robust directional propulsion of light-activated Fe 3 O 4 @TiO 2 /Pt Janus micromotors by magnetic spinning and the Magnus effect. Once exposed to a low-intensity rotating magnetic field, the micromotors become physically actuated, and their rotational Brownian diffusion is quenched by the magnetic rotation. Photocatalytic propulsion can be triggered by unidirectional irradiation based on a self-electrophoretic mechanism. Thus, a transverse Magnus force can be generated due to the rotational motion and ballistic motion (photocatalytic propulsion) of the micromotors. Both the self-electrophoretic propulsion and the Magnus force are periodically changed due to the magnetic rotation, which results in an overall directed motion moving toward a trajectory with a deflection angle from the direction of incident light with enhanced speed, maneuverability, and steering robustness. Our study illustrates the admirable directional motion capabilities of light-driven Janus micromotors based on magnetic spinning and the Magnus effect, which unfolds a new paradigm for addressing the limitations of directionality control in the current asymmetric micromotors.

Investigations undertaken to understand the mechanics of the motion of large sandbags and to compute their trajectories are reported in this paper, along with the details of the experimental setup and procedures. The motion of sandbags is recorded from the side of a flume by a high-definition charge-coupled device (CCD) camera, and the digital particle tracking velocimetry (DPTV) technique is used to track the motion of the bags. An equation is developed for the normalized maximum horizontal settling distance from the experimental data. It is found that the particle velocity normal to the flow depends mainly on the characteristic diameter of the particle and the Froude number of the flow, whereas the particle velocity in the streamwise direction shows lower dependency on the Froude number. Analysis of the particle tumbling shows that the Magnus force may be neglected for the purpose of modeling the trajectories of sandbags in uniform flows. A model of particle motion is developed by solving the Lagrangian equation numerically. Two approaches to computing the trajectory of sandbags are investigated. The results show that the approach in which the drag coefficient is varied based on the orientation of a particle gives better results than if the drag coefficient is kept constant and is based on the broadside orientation of the particle. The results also show that the change in the drag coefficient may be as low as 28% to as high as 76% based on the orientation of the particle with respect to the flow. [ABSTRACT FROM AUTHOR]

Abstract: Aerodynamic force measurements and a flow field survey were carried out on a sphere rotating perpendicular to the flow direction in order to investigate the effect of the rotation on the flow parameters at Reynolds numbers in the range of 0.68×105