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Background The blade unit of the tridimensional rotational flow sieve tray (TRST) makes the fluid form a rotational–perforated flow. The analysis of the flow properties of the unit is helpful to understand the hydrodynamic characteristics of TRST. Methods The gas–liquid concurrent flow field was studied using the multi-fluid VOF method. The rotational and perforated flows at each section were analyzed based on the section rotational flow ratios. Significant findings The section rotational flow ratio for the gas phase was between 0.6 and 0.85, and the transition section of the rotational and perforated flows of the liquid phase was z = 30 mm. The relationships between TRST and blade unit were clarified. The simulation performed for analyzing the mass transfer and structural optimization of the blade unit and TRST.

The air curtain system can collect the dust particles from hard-to-seal sources, which proves to be a feasible method for satisfying the increasing dust prevention requirements in China. In this study, aiming at addressing the dust escape problem at the tobacco stem loading point in a tobacco factory, a rotational flow air curtain dust-collecting system with a size of 2m x 2m x 2m was used for dust collection. The dust-collecting characteristics using the original dust suction hood and the developed air curtain dust-collecting system were analyzed and compared. Results show that the external dust concentration when the original dust suction hood operated was as high as 83.65 mg/m3, with a dust-collecting efficiency of only 16.35 %, suggesting serious dust escape; after the use of the developed air curtain dust-collecting system, the dust-collecting efficiency reached up to 86.93∼94.76 % under the same operating conditions. By studying the influence of two factors, air curtain jet velocity and exhaust-to-pressure ratio, on the dust collection efficiency of the air curtain system, at an exhaust-to-pressure ratio of 0.8 and an air curtain jet velocity of 13.5 m/s, the corresponding dust-collecting efficiency reached a maximum of 94.76 %. The present test results confirmed a better application effect of the developed air curtain dust-collecting system than the original dust-collecting system at the industrial loading point. Using the developed air curtain dust-collecting system is mainly aimed at the dust source, reduce the dust in the workshop dissemination and dispersion that can lower the transmission path of COVID-19 via aerosol.

Using CFD simulation, we first investigated the flow field distribution of the tridimensional rotational flow sieve tray (TRST) under different structural parameters (i.e. number of the blades, twist angle of the blades, tray height and sieve hole diameter) and installation methods (forward and backward) when gas flows downward through the TRST. Secondly, we carried out a comparative study of three modified structures of the tray, i.e. no supporting ring, a closed internal cylinder and no sieve holes present. Finally, we studied the transformed situations of the rotational flow and propose a dimensionless correlation to evaluate the performance of the tray. The results show that, apart from the tray with a smaller twist angle of the blade, the gas flow field distributions for all the other types of trays are similar. When two trays are installed, the gas flow field of the second tray in a forward installation is obviously different to that of a backward installation. The transformed position of the rotational flow for most types of trays is about half the depth of the tray. After comprehensive evaluation, the optimized tray structures are identified as a configuration with 8 blades, a 90° twist angle of the blades, a tray height of 40 mm, and sieve holes of 5 mm diameter. In addition, the tray should have open internal cylinder without a supporting ring. When a multi-tray is installed, the backward installation method should be adopted.

Perceiving the spatial layout of objects is crucial in visual scene perception. Optic flow provides information about spatial layout. This information is not affected by image blur because motion detection uses low spatial frequencies in image structure. Therefore, perceiving scenes with blurry vision should be effective when optic flow is available. Furthermore, when blurry images and optic flow interact, optic flow specifies spatial relations and calibrates blurry images. Calibrated image structure then preserves spatial relations specified by optic flow after motion stops. Thus, perceiving blurry scenes should be stable when optic flow and blurry images are available. We investigated the types of optic flow that facilitate recognition of blurry scenes and evaluated the stability of performance. Participants identified scenes in blurry videos when viewing single frames and the entire videos that contained translational flow (Experiment 1), rotational flow (Experiment 2) or both (Experiment 3). When first viewing the blurry images, participants identified a few scenes. When viewing blurry video clips, their performance improved with translational flow, whether it was available alone or in combination with rotational flow. Participants were still able to perceive scenes from static blurry images one week later. Therefore, translational flow interacts with blurry image structures to yield effective and stable scene perception. These results imply that observers with blurry vision may be able to identify their surrounds when they locomote.

A novel column internal is proposed, named the tridimensional rotational flow sieve tray (TRST), which has a three-dimensional hollow structure that can make the gas form two kinds of flow pattern coupled with each other: one is rotational flow and the other is flow through the perforations. Using an air-liquid system, we experimentally measured the pressure drops (dry and wet) when gas-liquid flows concurrently downwards through the TRST. We also examined the effects of gas-liquid flux, various geometric parameters of the TRST (i.e. number of blades, twist angles of the blades, tray heights and sieve hole diameters), tray installation methods (forward and backward) and number of installed trays on the pressure drop. The results indicate that the pressure drop increases with increasing gas-liquid flux, number and twist angles of the blades, but decreases with increasing tray heights and sieve hole diameters. The pressure drop of the tray is largest in backward installation, smaller in first installed location and smallest in forward installation. Compared with other new types of trays, the pressure drop of the TRST is lower and there is a significant resistance performance advantage. In addition, according to the mechanism of gas-liquid flow in the TRST, we established the mathematical model of TRST performance in the range of operating conditions. The fitting values agree well with the experimental values.

The rotational dynamics has been studied for different mass asymmetric systems In 49 122 + 50 126 Sn , Cs 48 114 + 54 134 In , Mo 40 100 + 64 148 Gd , Kr 36 86 + 67 162 Ho , Ga 31 71 + 71 177 Lu , Ni 28 60 + 76 188 Os and Cr 24 50 + 78 198 Pt for incident energies between 40 MeV/nucleon and 400 MeV/nucleon for impact parameter range 0.25 b ˆ 0.45 using isospin-dependent quantum molecular dynamics (IQMD) model. Our calculations reveal that the time evolutions of rotational observables for participant and spectator nuclear matter are different in mass asymmetric heavy ion reactions. Theoretical data of BUU model's azimuthal distributions for free protons have been compared successfully with IQMD model calculations. The rotational flow of free protons with increasing incident energies and elliptic flow (calculated from the fits of azimuthal distributions of free protons) dependence with energy has also been investigated.

This work presents the development of the new De-Esterified Tragacanth (DET) microcapsules (MCs). Co-flow extrusion method was applied for producing the MCs; the processing parameters were optimized by the Taguchi design to obtain the smallest and the most spherical MCs. Computational Fluid Dynamic (CFD) modeling was accomplished to show the formation of droplets at different airflows, and finally, βTC3 pancreatic cells were encapsulated in the MCs. The optimum MCs had 214.58μm size and 60.75% sphericality. The air pressure and the cross-linking reaction of DET were the most influential parameter in size and the sphericality of MCs, respectively. CFD showed two velocity vortices with rotational flow formed in the chamber, which caused changing the droplet moving direction. The encapsulated cells were proliferated, and cell viability was not reduced during six days. These phenomena make DET MCs a potential candidate for the cell encapsulation.

Among many practical applications in hydraulic engineering, rotational separators of a suspension and vortex flow controls may serve as especially interesting examples. This form of motion, despite some evident regularity, is a complex phenomenon so to describe it one should make use of CFD tools or pursue an experimental approach to the subject. Both of these possibilities are not very convenient, so any rational method that provides a possibility for calculating the velocity field and pressure distribution is welcome. For the considered class of technical objects, the family of kinematic models is to the purpose. The velocity field is described in this case by some algebraic relations, assumed arbitrarily on the basis of a qualitative evaluation of this field and the model constant is calculated from a delivered and dissipated energy in the energy balance. This method was effectively used in the description of rotational separators and pressure flow controls operation. This paper presents an application of such an approach to open flow regulators.

Tracer materials as inserts have been used to study the material flow during Friction stir spot welding (FSSW) of DP590 steel of 1.6 mm thickness. A PCBN tool with convex scrolled shoulder was used for welding. The progressive development of the material flow with tool penetration has been investigated by tracking the tracer distribution. When flow conditions are established, the shoulder scrolls provide the driving force for material flow by dragging the plasticized materials towards the pin and releasing them there. The released material flow outwards and upwards towards the shoulder periphery along different sub-surface flow routes. Successive flows in this fashion builds up the material circulation within the flow zone. The bonding ligament is created by intermixing of material between the overlapping sheets. The flow zone size and ligament width increases with increasing tool penetration. The flow zone encompasses the pin and a large area below the tool shoulder. Material flow during FSSW can be subdivided in two components, namely rotational flow and through thickness flow. A combination of the two components results in the spiraling motion of plasticized material within the flow zone. A material transport model is developed on the basis of experimental observations, illustrating the material flow during FSSW and the formation of bonding ligament.

The hydrodynamic performance of the TRST in a gas-liquid countercurrent flow column was investigated experimentally in this article. The results show that the operating field can be divided into low and high loading areas according to the increasing rate of the pressure drop. The space utilization of the tray is low, and the flow patterns are mainly droplet-column and continuous film flows. The pressure drops of the tray at each installed locations are different, indicating that the gas-liquid load of each tray is unbalanced. Compared with concurrent flow operation, the range of gas flux is at least 45% less, and the liquid flux range is at least 37.5% less. Compared with other new tray types under countercurrent flow operation, the pressure drop of the TRST is smaller, less than 300 Pa, but the range of gas-liquid flux is also narrow. The empirical models of the pressure drops, loading curve, and flooding curve agree well with the experimental data.

Rotational flow is often observed in lotic ecosystems, such as streams and rivers. For example, when an obstacle interrupts water flowing in a stream, energy dissipation and momentum transfer can result in the formation of rotational flow, or a vortex. In this study, I examined how rotational flow affects a predator–prey system by constructing a spatially explicit lattice model consisting of predators, prey, and plants. A predation relationship existed between the species. The species densities in the model were given as S (for predator), P (for prey), and G (for plant). A predator (prey) had a probability of giving birth to an offspring when it ate prey (plant). When a predator or prey was first introduced, or born, its health state was assigned an initial value of 20 that subsequently decreased by one with every time step. The predator (prey) was removed from the system when the health state decreased to less than zero. The degree of flow rotation was characterized by the variable, R . A higher R indicates a higher tendency that predators and prey move along circular paths. Plants were not affected by the flow because they were assumed to be attached to the streambed. Results showed that R positively affected both predator and prey survival, while its effect on plants was negligible. Flow rotation facilitated disturbances in individuals’ movements, which consequently strengthens the predator and prey relationship and prevents death from starvation. An increase in S accelerated the extinction of predators and prey.

The movement of a pair of point vortices with arbitrary intensities, embedded in a nonstationary shear and rotational flow, is studied. The expression for the vorticity center is shown to be reduced to a Riccati equation. In the particular case of harmonic oscillations, parametric resonance, which results in unbounded motion of the vortex pair, is found and analyzed. Using the fast oscillation averaging, an analytical estimate for the main zone in the parametric space is obtained. With the help of numerical calculations, the reliability of the estimate is asserted and a family of the minor zones is obtained.

A ship's screw-propeller produces thrust by rotation and, at the same time, generates rotational flow behind the propeller. This rotational flow has no contribution to the generation of thrust, but instead produces energy loss. By recovering part of the lost energy in the rotational flow, therefore, it is possible to improve the propulsion efficiency. The contra-rotating propeller (CRP) system is the representing example of such devices. Unfortunately, however, neither a design method nor a full-scale performance prediction procedure for the CRP system has been well established yet. The authors have long performed studies on the CRP system, and some of the results from the authors’ studies shall be presented and discussed.

This paper presents the centrifugation of the nano-particles using the rotating flow in the microchamber. The feasibility of the microfluidic centrifuge was demonstrated numerically and experimentally. The centrifugation of the nano-particles of 300 and 500 nm was visualized by using a high-speed CCD camera and a micro-PIV. In addition, its performance was characterized quantitatively. The experimental results of the mechanical contact-free microfluidic centrifuge showed the same physical phenomena with the conventional one even in its small size. Also, a new finding was obtained that the transient motion influenced the stable operation of the microfluidic centrifuge.

Two linear eddy-viscosity models, the v2-f and k-ω models, have been combined with an algebraic structure-based algorithm for the evaluation of the Reynolds stresses. This closure was originally designed as an integral part of the algebraic structure-based model (ASBM) to capture the turbulent anisotropy occurring in rotating wall bounded flows. It is shown that the algebraic structure-based evaluation of the Reynolds stresses can be used directly with conventional turbulence models sensitizing them to rotation. Significant improvement in the prediction of anisotropic turbulent flow can be achieved without an additional tuning of the closure coefficients. The models are evaluated in spanwise rotating channel flow and in flat plate boundary layers. The sensitivity to the Reynolds and rotation numbers is investigated. The results are compared with DNS data. © 2006 Elsevier Inc. All rights reserved. 27 653 660 653-660

We consider stationary and nonstationary problems of viscous incompressible fluid flows with slip boundary conditions in a rotating bounded domain. We show a geometrical representation of the slip conditions where principal curvatures of its boundary surfaces are characteristic coefficients. When the domain is axisymmetric, it is proved that a steady flow exists if external force f→ in equations of motion is orthogonal to rigid rotational flows, and that a nonstationary flow converges to a steady flow depending on its initial flow as time tends to infinity, if f→ is independent of time and orthogonal to rigid rotational flows and if the L2-norm of f→ is sufficiently small.

Resume On montre dans cette Note que la modelisation des ecoulements turbulents homogenes rotationnels en moyenne exige de considerer, a cote des effets lies au nombre de composantes de la fluctuation de vitesse et a la dimensionalite de celle-ci, les effets directement lies a la rotation moyenne de l'ecoulement a travers un tenseur du troisieme ordre, la stropholyse. On forme l'equation pour la partie completement symetrique de cette stropholyse et on discute les prerequis necessaires a la fermeture des termes qui interviennent dans cette equation. Pour citer cet article : J. Piquet, C. R. Mecanique 331 (2003).

It is shown that for a body which is swimming at low Reynolds number and is spherical at some time of its motion the mean surface flow velocity and the mean surface rotational flow velocity in the laboratory frame vanish at that time. The instantaneous translational and rotational swimming velocities are the opposite of the mean surface flow velocity and the mean surface rotational flow velocity in the rest frame. The swimming velocities are calculated for an example of spherical squirming motion. In the example, the translational swimming velocity oscillates in time about a steady value and the rotational swimming velocity is steady.

Fine particle separation is essential to a lot of high technologies in energy and other areas. The need for high standard of separation performance challenges conventional gas/solid separation devices like cyclones. A brief comparative analysis on some previous efforts of improving fine particle separation is made. Numerical simulation for the three-dimensional flow in a multi-crossing flow separator is introduced. The result shows a flow pattern of solid-body vortex in the channels, which is different with that of conventional cyclones. Two criteria C 1 and C 2 are proposed for evaluating the performance of fine particle separation, which correlate the separation performance with the characteristic flow parameters of separators. The comparison of the separation performance for different separators based on C 1 and C 2 indicates that the rotational flow pattern in separators affects the performance of fine particle separation. Finally, an innovative idea for improving fine particle separation is suggested and explained.

An overview of the development and current state of analytic element method, as well as a brief presentation of the principles on which the technique is based is presented in this article. Illustrations of a few representative analytic elements are also presented. A brief discussion is added of both rotational flow and transient flow. The latter two aspects of the method require further development before they are ready for implementation in computer programs and can be applied to the modeling of groundwater flow.

Recent studies have suggested that humans cannot estimate their direction of forward translation (heading) from the resulting retinal motion (flow field) alone when rotation rates are higher than ∼ 1 deg/sec. It has been argued that either oculomotor or static depth cues are necessary to disambiguate the rotational and translational components of the flow field and, thus, to support accurate heading estimation. We have re-examined this issue using visually simulated motion along a curved path towards a layout of random points as the stimulus. Our data show that, in this curvilinear motion paradigm, five of six observers could estimate their heading relatively accurately and precisely (error and uncertainty < ∼ 4 deg), even for rotation rates as high as 16 deg/sec, without the benefit of either oculomotor or static depth cues signaling rotation rate. Such performance is inconsistent with models of human self-motion estimation that require rotation information from sources other than the flow field to cancel the rotational flow. Published by Elsevier Science Ltd

Exact “universal” unsteady rotational flow solutions are compared to an earlier class of exact unsteady flows. They apply to different flow situations.

The rotational flow in a region bounded by two axisymmetric closed surfaces has been studied by variational methods. The approach is described in detail for the global power-law representation of a viscosity function. Numerical, as well as simple, analytical results applicable to immersion rotational viscometry are given for the spheroidal geometry of bounding surfaces.

An exact formulation is used to solve the problem of the effect of rotating tangential stresses of prescribed form, exerted on a free plane surface of a viscous fluid. The qualitative structure of the flow which appears within the fluid is studied. The use of the results to calculate the upwelling caused by hurricanes outside the zone of the strongest winds, yields real numerical values. The motion of the fluid studied here refers to the class of selfsimilar conical flows, various types of which were studied in /1–7/.

The first part of this paper contains a reconsideration of the conventional squeeze-film situation. It is shown that the Part 1 concentration on the half-time t 1 2 sometimes hides interesting elastico-viscous effects, since these are most pronounced at short times after the load is applied. The bulk of the paper is concerned with the more general situation in which a rotational flow is superimposed on the basic squeezing flow. This is brought about by rotating the bottom plate. An approximate theoretical analysis is shown to lead to a satisfactory prediction of observed behaviour under conditions of light loading. The experiments show substantial transient stress-overshoot effects under some conditions and there is also a possible indication of long-range memory effects in some of the experiments.

A dynamically self-consistent model is proposed of the nearly-viscometric steady rotational flow of a simple fluid. The main feature of the model is its linearity with respect to transversal secondary motions disturbing a primary viscometric circular flow. It is shown that this ‘quasi-viscometric’ model represents all the flow and stress patterns with relevancy up to the second order, O( Re 2 , ReWi , Wi 2 ). In the quasi-viscometric model, three material viscometric functions appear only. The QV model is thus self-consistent from experimental point of view as well.

An analysis is presented on the deposition from a charged aerosol passing through a two-dimensional bend due to the simultaneous action of inertial and electrostatic forces. Collection efficiency is found for an idealized rotational flow. The results are compared qualitatively with available experimental data.

It is proved that the vanishing of the velocity-velocity commutator is possible only if ∫ d 3 x υ μ ( x ) is a multiple of the identity or a constant of motion; equivalence of Landau's approach to that of Yamasaki et al. is also discussed.

The viscosity of the medium is taken into consideration in deriving an evolution equation describing the propagation of non-linear centrifugal waves along the free surface of a translational-rotational liquid flow. The result is the Burgers-Korteweg-de Vries (BKdV) equation, for which a steady solution is described in the form of a shock wave with soliton oscillators near the front. Estimates are presented for the effect of viscosity on the wave-front structure and the conditions of formation previously predicted by the author /1/ for centrifugal solitons, which play an important role in various atmosphere processes ∗∗ .