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Bath stirring, degassing, and decarburization in steel refining are strongly related to flow behaviors. The bubble plume produced in Ruhrstahl–Heraeus (RH) up‐snorkel plays an important role during refining, since it not only acts as a bubble pump, but also provides the reaction interface. Herein, it is aimed to form a new flow pattern in the up‐snorkel by using a nonradially arranged gas‐injection nozzle to enhance the 260 ton RH refining process. The results show that an upward spiral steel flow is produced, when nonradial gas‐injection nozzles are used in the up‐snorkel. Meanwhile, some bubbles moved toward the center region of the up‐snorkel, which may be caused by the centripetal effect in a rotational steel flow. This leads to a more uniform bubble distribution on the cross section of the snorkel, compared to that of the conventional case. Specifically, the circulation flow rate is increased by about 18.0%, and the mixing time are shortened by about 26.2% (criteria of ±5%), compared to that of the conventional case. In addition, the inclusion removal rate is increased by 0.5%, 4.8%, and 11.3% for the inclusion size of 20, 50, and 100 μm, respectively, compared to the conventional radial nozzle case. [ABSTRACT FROM AUTHOR]

Rotational moulding is a versatile polymer shaping process used to create enclosed parts from powdered precursors using heat and multi-axis rotation. Controlling the heating process and mould motion is critical to producing high-quality parts, and failures due to incorrect mould coverage or variable wall thickness are common. To date, limited simulation tools exist to predict the motion of the powder within the mould, and operators rely on unreliable prior experience to avoid defects. This paper presents an SPH simulation framework to predict particle flow patterns and powder contact time within a rotating mould. The powder-to-wall contact time was derived from the transient rigid body force (RBF) of different sensors on the mould. The method was compared with the results of DEM simulation and validated by the particle flow pattern of two experimental results. Results showed that the SPH method was capable of simulating particle flow macroscopic properties. The great computing efficiency of SPH compared to DEM simulation was also demonstrated. • Couple the SPH framework with a soil material model to simulate the polymer flow motion during rotational moulding process. • Modelling framework validated by two experimental benchmarks. • Present a significant benefit compared to the DEM method when simulating particle flow with millions of particles. [ABSTRACT FROM AUTHOR]

In comparison to alternative methods for hydrogen production, water electrolysis stands out as the optimal means for obtaining ultra-pure hydrogen. However, its widespread adoption is significantly hampered by its low energy efficiency. It has been established that the introduction of an external magnetic field can mitigate energy consumption, consequently enhancing electrolysis efficiency. While much of the research has revealed that an electrode–parallel magnetic field plays a crucial role in enhancing the bubble detachment process, there has been limited exploration of the effect of electrode–normal magnetic fields. In this work, we compare the water electrolysis efficiency of a circular electrode subjected to electrode–normal magnetic field resulting in a magnet edge effect and electrode edge effect by varying the sizes of the magnet and electrode. The findings indicate that a rotational flow caused by the Lorentz force facilitates the detachment of the hydrogen from the electrode surface. However, the rotation direction of hydrogen gas bubbles generated by the magnet edge effect is opposite to that of electrode edge effect. Furthermore, the magnet edge effect has more significant influence on the hydrogen bubbles' locomotion than the electrode edge effect. With an electrode gap of 30 mm, employing the magnet edge effect generated by a single magnet leads to an average of 4.9% increase in current density. On the other hand, the multiple magnet effects created by multiple small magnets under the electrode can further result in an average 6.6% increase in current density. Nevertheless, at an electrode spacing of 50 mm, neither the magnet edge effect nor the electrode edge effect demonstrates a notable enhancement in conductivity. In reality, the electrode edge effect even leads to a reduction in conductivity. [ABSTRACT FROM AUTHOR]

Several valuable isotopes used in medicine, industry, and science cannot be separated by a gas centrifuge with a driven mechanical rotor due to the lack of a suitable working gas that has a sufficiently high vapor pressure at room temperature. Such isotopes are typically produced by more costly separation processes. An advanced plasma centrifuge (PC) has been proposed that can separate specific isotopes at a lower cost. The PC achieves increased separation performance by the excitation of an axial counterflow in the plasma medium. In this work, we consider the non-isothermal Bödewadt problem for the PC with thermally driven axial circulation created by cooling one end of the PC's separation chamber. Due to the imbalance between the centrifugal force and the radial pressure gradient, we show that a secondary flow appears, which is imposed on the medium's rotation motion. The effect is analogous to the classical Bödewadt problem, where a rotational flow decelerates over a fixed surface. [ABSTRACT FROM AUTHOR]

Objective: To explore the experimental justification of cerebrospinal fluid (CSF) amplitude and elastic fluctuations of ventricles, we extend our previous computational study to models with rotational flow and suitable boundary conditions. In the present study, we include an elastic effect due to the interaction with the thermal solutal model which accounts for CSF motion which flows rotationally due to hydrocephalus flows within the spinal canal. Methods: Using an analytical pertubation method, we have attempted a new model to justify CSF flow movement using the influences of wall temperature difference. Results: This paper presents results from a computational study of the biomechanics of hydrocephalus, with special emphasis on a reassessment of the parenchymal elastic module. CSF amplitude in hydrocephalus patients is 2.7 times greater than that of normal subjects. Conclusions: This finding suggests a non-linear mechanical system to present the hydrocephalic condition using a numerical model. The results can be useful to relieve the complexities in the mechanism of hydrocephalus and can shed light to support clinically for a convincing simulation. [ABSTRACT FROM AUTHOR]

Aging impacts human observer's performance in a wide range of visual tasks and notably in motion discrimination. Despite numerous studies, we still poorly understand how optic flow processing is impacted in healthy older adults. Here, we estimated motion coherence thresholds in two groups of younger (age: 18–30, n = 42) and older (70–90, n = 42) adult participants for the three components of optic flow (translational, radial and rotational patterns). Stimuli were dynamic random-dot kinematograms (RDKs) projected on a large screen. Participants had to report their perceived direction of motion (leftward versus rightward for translational, inward versus outward for radial and clockwise versus anti-clockwise for rotational patterns). Stimuli had an average speed of 7°/s (additional recordings were performed at 14°/s) and were either presented full-field or in peripheral vision. Statistical analyses showed that thresholds in older adults were similar to those measured in younger participants for translational patterns, thresholds for radial patterns were significantly increased in our slowest condition and thresholds for rotational patterns were significantly decreased. Altogether, these findings support the idea that aging does not lead to a general decline in visual perception but rather has specific effects on the processing of each optic flow component. [ABSTRACT FROM AUTHOR]

Due to enhanced heat transfer rate, the nanofluid and hybrid nanofluids have significant industrial uses. The principal objective of this exploration is to investigate how thermal radiation influences the velocity and temperature profile. A water-based rotational nanofluid flow with constant angular speed Ω is considered for this comparative study. A similarity conversion is applied to change the appearing equations into ODEs. Three different nanoparticles i.e., copper, aluminum, and titanium oxide are used to prepare different nanofluids for comparison. The numerical and graphical outputs are gained by employing the bvp-4c procedure in MATLAB. The results for different constraints are represented through graphs and tables. Higher heat transmission rate and minimized skin friction are noted for triple nanoparticle nanofluid. Skin coefficients in the x-direction and y-direction have reduced by 50% in trihybrid nanofluid by keeping mixed convection levels between the range 3 < ϵ ≤ 11 . The heat transmission coefficient with raising the levels of thermal radiation between 0.5 < π ≤ 0.9 and Prandlt number 7 < Pr ≤ 11 has shown a 60% increase. [ABSTRACT FROM AUTHOR]

Tsuji burners, in which flames may be anchored in the forward stagnation region of a cylindrical porous fuel injector placed in a uniform air stream, are addressed here for moderately large Reynolds numbers. Attention is focused on conditions under which the fuel-injection velocity is not sufficiently small compared with the outer air velocity for the boundary layer to remain attached to the forward part of the cylinder surface. In the resulting flow, the flame is embedded in the thin mixing layer that forms at the surface separating the outer air stream from the fuel stream, both having, in general, different densities. The flow on the air side of the mixing layer is potential, while that on the fuel side usually is rotational because exit conditions for the fuel injection generate vorticity, for example, by imposing a requirement that the fuel must emerge normal to the cylinder surface, which is the condition analyzed herein. It is shown that introduction of a suitably density-weighted stream function reduces the problem to that of constant-density flow, with the density-square-root-weighted ratio of injection velocity to free-stream velocity Λ emerging as the only controlling parameter. The numerical solution, involving determination of the vorticity distribution in the inviscid fuel flow through an iterative scheme, provides the structure of the flow, including the mixing-layer location and the inviscid-flow strain rate there. Numerical results are presented for values of Λ ranging from small ( Λ ≪ 1) to large ( Λ ≫ 1) injection velocities. The inviscid results in the limit of vanishingly small injection velocities ( Λ approaching zero) demonstrate that, unlike the prediction of the potential-flow solution, when the fuel-side flow is rotational the outer air velocity never approaches the classical solution corresponding to potential flow around a solid cylinder ( Λ = 0), a result affecting the interpretation of analyses of experiments involving flames stabilized on Tsuji burners as the boundary layer is blown off. In particular, with rotational fuel-side flow, the streamline separating the fuel and oxidizer regions lies farther from the cylinder surface, resulting in a larger near-quiescent wake and a lower strain rate along the separating streamline. [ABSTRACT FROM AUTHOR]

In this paper, the thermal behavior of nanofluids was numerically simulated during nanoparticle sedimentation. Using the finite volume method by combining appropriate solvers, a new solver was developed in the open-source framework, i.e., open Foam. Free convection flow was transiently modeled using this solver during the sedimentation of the second phase (nanoparticles). A relative velocity term from the Vesilind relation was added to the momentum equation to model the sedimentation. Bossiness and Maiga's relations were used to calculate the density changes with temperature and effective conductivity, respectively. Simulations were performed for square, triangular, and circular cross-sections with the same hydraulic diameter at three Rayleigh numbers. In addition, the changes in Nusselt number over time and the distribution of nanoparticles under different conditions were studied. The results showed that forming the sediment layers at the bottom of the enclosure reduced the streamlines and decreased natural convection and rotational flow. In addition, it contributed to conductive heat transfer, leading to a rapid decrease in the Nusselt number of cavities. Moreover, by increasing the Rayleigh number, the square and triangular cross sections had the highest and lowest heat transfer, respectively. [ABSTRACT FROM AUTHOR]

Straight radial impeller disc pumps are widely used in several industrial applications for hard-to-pump working flow media, such as two-phase inlet conditions, either including non-miscible bubbles or solid particles with a high concentration within the main working flow. Compared with conventional pump designs, these pumps have not been widely studied, because of their particular simple design and low efficiency values that can however reach a maximum value of 0.5 with a good pressure increase in single-phase conditions. Regarding this, no basic analysis has been performed to build one-dimensional design rules considering the relative effects of design parameters proper to these unusual designs like the blade number, blade height and disc spacing. This step is an important one for two-phase flow performance evaluations which are usually derived from single-phase ones as for conventional pumps. Two different disc pump designs with, respectively, 8 and 10 radial blades, are numerically and experimentally investigated. Experimental investigations are performed in an open loop tap water test facility, under various working conditions, combining flow rate and rotational speed variations. The overall pump performances are compared and analyzed, including cavitation onset phenomena that have been found to influence the experimental performances of both pumps. The overall performance modification between both impeller designs is analyzed. Comparisons between CFD and experimental results give reliable results and can be considered to cover a sufficiently wide range of design parameters allowing us to build future adapted design rules for such specific designs. [ABSTRACT FROM AUTHOR]

An ideal static mixer can achieve efficient mixing at low pressure drops. Owing to the excellent performance of the tridimensional rotational flow sieve tray (TRST) in a gas–liquid two‐phase system, the TRST structure was modified into a rotational–perforated static mixer (RPSM) to enhance mixing in multicomponent liquid systems. The energy consumption characteristics of the RPSM were experimentally studied based on Reynolds numbers in the range of 986–7892, gap L = 0–80 mm, and relative angle γ = 0–45°. The effects of the element installation method, number, gap, relative angle, fluid Reynolds number, fluid properties, and other parameters on the RPSM pressure drop were also investigated. An interaction analysis of each factor was performed using the factorial design method and an empirical model of the RPSM Z‐factor was established. Additionally, pressure drop in the RPSM was compared with those of other commonly used static mixers. Results show that, when the element is backward‐installed, the pressure drop is higher than that in the forward direction because the fluid is constantly twisted. Moreover, the pressure drop increases with increasing element gap, and the average increase is 43.64% and 19.28% for the forward and backward installations, respectively. The influence of the relative angle on the pressure drop is mainly reflected when the gap L = 0. Subsequently, the degree of influence of each factor was determined, and the Z‐factor was calculated and found to be consistent with the experimental values (relative error of less than 15%). [ABSTRACT FROM AUTHOR]

In this 4D flow cardiovascular magnetic resonance (CMR) study, vortical blood flow in the main pulmonary artery (MPA) is quantified using circulation (ᴦ), a metric used in fluid dynamics to quantify the rotational components of flow. Circulation (ᴦ) is a 4D flow CMR metric that quantifies the vortical blood flow pattern in the MPA of patients with pulmonary hypertension (PH), distinguishes them from healthy controls, and shows high correlation with invasive markers of PH severity. [ABSTRACT FROM AUTHOR]

The deflector wheel classifier is a widely used device for the separation of fine powders in different industrial applications. The primary objective of the separation process is to achieve high-quality separation of fine powders characterized by a narrow particle size distribution and high separation sharpness. Theoretically, the reduction in the cut size is accomplished by decreasing the gas flow rate or increasing the rotational speed of the classifier, which amplifies the centrifugal forces compared to the drag forces exerted on the particles. This behavior is, indeed, observed in many cases, but it cannot be extrapolated arbitrarily. At their performance limit, classifiers may, against expectation, show an increase in cut size and, in addition, a reduction in the sharpness of the separation process. The limitation in the reduction in the cut size and in the improvement in the separation sharpness arises due to an imbalance between the operating rotational speed and flow rate, which results in a non-uniform flow field in the classifier. If the balance conditions are fulfilled, an optimum separation with a high separation sharpness can be achieved. In this work, CFD simulations validated by some experimental results are employed to represent this limitation, which is obtained by varying the operating parameters using different material densities with particles ranging from one to ten microns. [ABSTRACT FROM AUTHOR]

Using VLT/MUSE integral-field spectroscopic data for the barred spiral galaxy NGC 1097, we explore techniques that can be used to search for extended coherent shocks that can drive gas inflows in centres of galaxies. Such shocks should appear as coherent velocity jumps in gas kinematic maps, but this appearance can be distorted by inaccurate extraction of the velocity values and dominated by the global rotational flow and local perturbations like stellar outflows. We include multiple components in the emission-line fits, which corrects the extracted velocity values and reveals emission associated with AGN outflows. We show that removal of the global rotational flow by subtracting the circular velocity of a fitted flat disc can produce artefacts that obscure signatures of the shocks in the residual velocities if the inner part of the disc is warped or if gas is moving around the centre on elongated (non-circular) trajectories. As an alternative, we propose a model-independent method which examines differences in the LOSVD moments of H α and [N II]λ6583. This new method successfully reveals the presence of continuous shocks in the regions inward from the nuclear ring of NGC 1097, in agreement with nuclear spiral models. [ABSTRACT FROM AUTHOR]

Axial-flow pumps may experience significant pressure pulsation and high hydraulic noise when deviating from design conditions, and this article investigates the cross influence of rotational speed and flow rate on inlet pressure pulsation and hydraulic noise of an axial-flow pump based on coherence theory through physical model experiments. The energy amplitude of pressure pulsation is directly proportional to rotational speed and inversely proportional to flow rate, as rotational speed increases, the energy distribution of the blade passage frequency (fBPF) within different frequency bands of pressure pulsation improves. Pressure pulsation and the overall natural frequency of the pump device work together to define the primary and secondary frequencies of the sound pressure level, as rotational speed increases, these frequencies eventually move toward 2fBPF, and the coherence coefficient at frequencies of fBPF and 2fBPF is above 0.9. To reduce hydraulic noise, both pressure pulsation and natural frequency should be given sufficient attention. [ABSTRACT FROM AUTHOR]

The metallurgical function of mold electromagnetic stirring(M-EMS) was investigated by simulation according to the following factors: flow field, temperature field, solidification, removal of inclusions, slag entrainment, and macrosegregation. When the current intensity increased from 0 A to 490 A, the rotational flow induced by M-EMS enhanced gradually, and the impinging effect of jet flow on the solidification front decreased obviously. The average speed on the top surface increased from 0.015 m/s to 0.038 m/s. The temperature of the molten steel was more uniform, and the temperature on the top surface decreased from 1788.5 K to 1785.9 K. The depth of depressions induced by the jet flow decreased from 6.1 mm to 0.7 mm. When the current intensity of M-EMS was 390 A, the removal fraction of inclusions was the highest. When the current intensity of M-EMS was 0 A, no slag entrainment occurred. With the current intensity of M-EMS increasing from 290 A to 490 A, the net slag entrainment rate was 0.003, 0.013, and 0.047 kg/s. When the current intensity of M-EMS increased from 0 A to 490 A, the minimum carbon content of negative segregation in the subsurface of the bloom worsened from 0.176% to 0.167%. For the bloom CC process, the M-EMS scheme should be weak or no M-EMS to decrease the occurrence of slag entrainment and improve the negative segregation in the subsurface of the bloom. [ABSTRACT FROM AUTHOR]

The magnetohydrodynamic (MHD) rotating flow that occurs across a stretching surface has numerous practical applications in a variety of domains. These fields include astronomy, engineering, the material sciences, and space exploration. The combined examination of magnetohydrodynamics rotating flow across a stretching surface, taking into consideration fluctuating viscosity and nanoparticle aggregation, has significant ramifications across several different domains. It is essential for both the growth of technology and the attainment of deeper insights into the complicated fluid dynamics to maintain research in this field. Given the aforementioned motivation, the principal aim of this study is to examine the effects of variable viscosity on the bidirectional rotating magnetohydrodynamic flow over a stretching surface. Aggregation effects on nanoparticles are used in the analysis. Titania (TiO2) is taken nanoparticle and ethylene glycol as base fluid. The nonlinear ordinary differential equations and the boundary conditions that correspond to them can be transformed into a dimensionless form by using a technique called similarity transformation. To get a numerical solution to the transformed equation, the Runge-Kutta 4th order (RK-4) method is utilized, and this is done in conjunction with the shooting method. The impact of various leading variables on dimensionless velocity, the coefficients of temperature, skin friction and local Nusselt number are graphically represented. Velocity profiles in both direction increases with increasing values of φ. The Nusselt number increases with increasing values of the radiation and temperature ratio parameters. When a 1 % volume fraction of nanoparticles is introduced, the Nusselt number exhibits a 0.174 % increase for the aggregation model compared to the regular fluid in the absence of radiation effects. When the aggregation model is used with a 1 % volume fraction of nanoparticles, the skin friction increases by 0.1153 % in the x direction and by 0.1165 % in the y direction compared to the regular fluid. Tables show the variation in Nusselt numbers, as well as a comparison of the effects of nanoparticle's aggregation model without and with radiation. Moreover, the numerical results obtained were compared with previously published data, demonstrating a satisfactory agreement. We firmly believe that this finding will have extensive implications for engineering and various industries.

Electromagnetic stirring (M-EMS) has been extensively applied in continuous casting production to reduce the quality defects of casting billets. To investigate the effect of continuous casting electromagnetic stirring on billet segregation, a 3D multi-physics coupling model was established to simulate the internal heat, momentum, and solute transfer behavior, to identify the effect of M-EMS on the carbon segregation of a continuous casting square billet of 200 mm × 200 mm. The results show that M-EMS can move the high-temperature zone upward, which is favorable for the rapid solidification of the billet, and can promote the rotational flow of the molten steel in the horizontal direction. When the electromagnetic stirring current is varied in the range of 0–500 A, the degree of carbon segregation first decreases and then increases, with the best control of segregation at 300 A. In the frequency range of 3–5 Hz, the degree of carbon segregation degree increases with frequency. Meanwhile, the simulation and experimental results show that 3 Hz + 300 A is the best electromagnetic stirring parameter for improving the carbon segregation of casting billets with a size of 200 mm × 200 mm. So, a reasonable choice of the M-EMS parameters is crucial for the quality of the billet. [ABSTRACT FROM AUTHOR]

The statistics of breaking wave fields are characterised within a novel multi-layer framework, which generalises the single-layer Saint-Venant system into a multi-layer and non-hydrostatic formulation of the Navier–Stokes equations. We simulate an ensemble of phase-resolved surface wave fields in physical space, where strong nonlinearities, including directional wave breaking and the subsequent highly rotational flow motion, are modelled, without surface overturning. We extract the kinematics of wave breaking by identifying breaking fronts and their speed, for freely evolving wave fields initialised with typical wind wave spectra. The $\varLambda (c)$ distribution, defined as the length of breaking fronts (per unit area) moving with speed $c$ to $c+{\rm d}c$ following Phillips (J. Fluid Mech. , vol. 156, 1985, pp. 505–531), is reported for a broad range of conditions. We recover the $\varLambda (c) \propto c^{-6}$ scaling without wind forcing for sufficiently steep wave fields. A scaling of $\varLambda (c)$ based solely on the root-mean-square slope and peak wave phase speed is shown to describe the modelled breaking distributions well. The modelled breaking distributions are in good agreement with field measurements and the proposed scaling can be applied successfully to the observational data sets. The present work paves the way for simulations of the turbulent upper ocean directly coupled to a realistic breaking wave dynamics, including Langmuir turbulence, and other sub-mesoscale processes. [ABSTRACT FROM AUTHOR]

Based on the energy dissipation rate, we proposed a systematic method for quantifying the effective viscosity, effective shear rate, and flow characteristics in a drilling flow of non-Newtonian fluids in a concentric annulus subjected to a combined pressure-driven and rotational flow. Two flow parameters, i.e., the energy dissipation rate coefficient and the effective shear rate coefficient, were introduced to quantify flow characteristics, such as the relationship between pressure drop, flow rate, torque, and rotational speed, which are nearly independent of rheological behaviors. In this work, we began with flow quantification of the individual flow problem in a concentric annulus, i.e., pressure-driven flow and rotational flow, and derived expressions of two flow parameters analytically in each case. Then, we established the flow quantification method for the combined pressure-driven and rotational flow. The proposed flow modeling scheme was derived analytically with a power-law fluid and was validated for various non-Newtonian fluids, such as Carreau and Herschel–Bulkley fluids, through extensive numerical simulations. The method can be employed for the in situ viscosity measurement of drilling muds in terms of shear rate, as well as for the estimation of torque, pressure drop, and power consumption. Maximum errors between theoretical prediction and numerical simulation results in estimating torque, pressure drop, and shear-dependent viscosity were found to be 5.5%, 7.3%, and 6%, respectively. [ABSTRACT FROM AUTHOR]

Untill 1980 one of the main subjects of study in the theory of nonlinear water waves were the Stokes and solitary waves (regular waves). To that time small amplitude regular waves were constructed and the existence of large amplitude water waves of the same type was proved by using branches of water waves starting from a trivial (horizontal) wave and ending at extreme waves. Then in papers Chen & Saffman [7] and Saffman [32] numerical evidence was presented for existence of other type of waves as a result of bifurcations from a branch of ir-rotational Stokes waves on flow of infinite depth. It was demonstrated that the Stokes branch has infinitely many bifurcation points when it approaches the extreme wave and periodic waves with several crests of different height on the period bifurcate from the main branch. The only theoretical works dealing with this phenomenon are Buffoni, Dancer & Toland [4,5] where it was proved the existence of sub-harmonic bifurcations bifurcating from the Stokes branch for the ir-rotational flow of infinite depth approaching the extreme wave. The aim of this paper is to develop new tools and give rigorous proof of existence of subharmonic bifurcations in the case of rotational flows of finite depth. The whole paper is devoted to the proof of this result formulated in Theorem 5.4. [ABSTRACT FROM AUTHOR]

In vertical contact control (VCC), a microdroplet array selectively contacts with an opposite microdroplet array. Generally, VCC is useful for the dispenser mechanism based on solute diffusion between microdroplet pairs. However, sedimentation due to gravity can cause an inhomogeneous distribution of solutes in microdroplets. Therefore, it is necessary to enhance solute diffusion to achieve the accurate dispensing of a large quantity of solute in the direction opposite to that of gravity. Herein, we applied a rotational magnetic field to the microrotors in microdroplets to enhance the solute diffusion in microdroplets. Driven by microrotors, the rotational flow can generate a homogeneous distribution of solutes in microdroplets. We analyzed the diffusion dynamics of solutes using a phenomenological model, and the results showed that the rotation of microrotors can increase the diffusion constant of solutes. [ABSTRACT FROM AUTHOR]

A new dynamic mixer has been designed for the mixing of two polymer melts. Three main design parameters (number of circles of holes N, number of holes M per circle, and diameter of the holes d3) for the mixing zone of the dynamic mixer were selected to study their influences on the pressure drop Δp and the segregation scale S using Taguchi orthogonal arrays method. The influences of flow rate and rotational speed were also investigated. In addition, the melt mixing quality was compared with that of screw-based and slotted-screw mixers. The results showed that the most significant factor influencing S and S·Δp is N. Both Δp and S increased with increasing flow rate, and decreased with increasing rotational speed. Compared to the screw-based and slotted-screw mixers, the dynamic mixer had a uniform melt mixing quality and shorter length. [ABSTRACT FROM AUTHOR]

Effective pre-dehydration is achieved to stabilize and improve oil production in high water cut oil fields. In order to reduce the pressure loss during the pre-dewatering process, a low-pressure-loss dynamic hydrocyclone (LPDH) was developed. And its swirler vane was designed which can not only drive liquid into circumferential rotational flow but also produce axial pressure. The axial pressure will compensate for the separation process pressure loss. The key parameters that affected the axial pressure were studied, the relative motion between the fluid and the vane was analyzed, and a pre-dehydration LPDH was designed (processing capacity is 1.0 m3/h). The changes in the separation efficiency and axial pressure of the LPDH with the operational and physical parameters were studied by the computational fluid dynamics (CFD) numerical simulation method. The results revealed that the pressure is increased during rotation-starting, and the pressure loss of LPDH was lower than the dynamic and compound hydrocyclones. Notably, low shear stress was generated using the designed vane when the fluid started rotating, and the separation efficiency increased under these conditions. When the speed of rotation of the swirler is 167.5 rad/s, the separation efficiency of the LPDH is greater than 99.8%. [ABSTRACT FROM AUTHOR]

The initial aim of the paper is to improve the ammonia removal efficiency from skim latex using air stripping in an agitated column. The effects of air flow rate, bubble sizes, types of impellers, and rotational speed were investigated. The results showed that ammonia decreased with the increased air flow rate and the decreased bubble size. More ammonia could be removed by the use of impellers at a low rotational speed. The axial flow impeller showed higher ammonia removal than that gained from the radial flow impeller. It could be concluded that the stripping process in an agitated column should be operated at an air flow rate under the homogeneous regime without pH and temperature adjustment. The use of axial flow impeller at a rotational speed below the turbulent flow is recommended for more ammonia removal. In addition, smaller bubbles than the working range proposed in this research should be avoided because of foaming formation of the skim latex. [ABSTRACT FROM AUTHOR]

Rapid erection is a key technology for modern warfare in vehicle weapon launch systems. It is challenging to attain rapidity with the hydraulic erecting system because of the intensified cavitation in the piston chamber at high speeds, which reduces volumetric efficiency and increases flow pulsation in the typical high-pressure axial piston pump. In this paper, an improved scheme for the cylinder window area overflow surface was proposed to solve this problem. Based on the full cavitation model and the compressible model, a numerical model of the internal flow in the piston pump was developed, and the effect of rotational speeds on the flow and cavitation characteristics of the pump was analysed. The results show that after the improvement, the maximum flow of the pump is increased from 1.765 kg/s to 2.295 kg/s, an increase of 30.028%, and the maximum speed corresponding to the volumetric efficiency of more than 90% is increased from 1500 rpm to 2100 rpm. At high speeds, the improved block can effectively suppress the cavitation and backflow in the piston chamber, improve the volumetric efficiency of the piston pump and reduce the flow pulsation, which is conducive to reducing the vibration and noise of the pump body. [ABSTRACT FROM AUTHOR]

Although there is a plethora of modeling literature dedicated to the object recognition processes of the ventral ("what") pathway of primate visual systems, modeling studies on the motion-sensitive regions like the Medial superior temporal area (MST) of the dorsal ("where") pathway are relatively scarce. Neurons in the MST area of the macaque monkey respond selectively to different types of optic flow sequences such as radial and rotational flows. We present three models that are designed to simulate the computation of optic flow performed by the MST neurons. Model-1 and model-2 each composed of three stages: Direction Selective Mosaic Network (DSMN), Cell Plane Network (CPNW) or the Hebbian Network (HBNW), and the Optic flow network (OF). The three stages roughly correspond to V1-MT-MST areas, respectively, in the primate motion pathway. Both these models are trained stage by stage using a biologically plausible variation of Hebbian rule. The simulation results show that, neurons in model-1 and model-2 (that are trained on translational, radial, and rotational sequences) develop responses that could account for MSTd cell properties found neurobiologically. On the other hand, model-3 consists of the Velocity Selective Mosaic Network (VSMN) followed by a convolutional neural network (CNN) which is trained on radial and rotational sequences using a supervised backpropagation algorithm. The quantitative comparison of response similarity matrices (RSMs), made out of convolution layer and last hidden layer responses, show that model-3 neuron responses are consistent with the idea of functional hierarchy in the macaque motion pathway. These results also suggest that the deep learning models could offer a computationally elegant and biologically plausible solution to simulate the development of cortical responses of the primate motion pathway. [ABSTRACT FROM AUTHOR]

Pumps as turbines play an important role in micro pumped hydro energy storage (PHES) systems, which are widely applied in remote areas, and their operational safety can be significantly affected by the transient power-off process. The aim is to analyze the unsteady internal flow characteristics and time–frequency characteristics of the pressure fluctuations of the pump as turbine (PAT) after power-off process by using finite volume method (ANSYS CFX) and bidirectional test rig. During the transient process of power failure, internal flow instabilities were revealed by analyzing the flow field and turbulence kinetic energy. The results indicated that the flow field between the blades was extremely unstable during the brake mode. Additionally, the absolute values of the rotational velocity and flow rate were 1.21 and 0.93 times higher than the initial values, respectively, during the runaway mode. The pressure fluctuations were analyzed in the time-frequency domains using the continuous wavelet transform. The main frequency of pressure pulsation at the volute was related to the rotating speed owing to the rotor-stator interaction. This study revealed the transient flow features during the process of mixed-flow pump as turbine failure, which provides a fundamental theory for the safe transient operations of pump as turbine. [ABSTRACT FROM AUTHOR]

Enhancing heat transfer efficiency is crucial for the performance of heat exchangers, and the implementation of corrugated tubes has been shown to be an effective approach. In this study, a numerical investigation was conducted to analyze the impact of varying corrugation depths in rod baffles and two types of corrugated tubes (1 start and 3 start) on heat transfer and pressure drop characteristics. Water was used as the working fluid on the shell side of the heat exchanger, while a constant wall temperature was maintained on the tube side. Corrugation ratios (e/dh) of 0.1 and 0.13, pitch (p) of 10, 20, and 30 mm, and two types of rod baffle spacing (x/d) of 1.25 and 1.375 were considered. The analysis was performed in the turbulent flow regime with Reynolds numbers ranging from 4,000 to 24,000. Three-dimensional governing equations were solved using the standard k-e model in ANSYS-Fluent 18.1 to examine the flow behavior within the corrugated tubes. The results indicated that a primary vortex was formed in the main flow due to the induced rotational flow along the helical path, as well as a secondary vortex behind the rib. These vortices disrupted the boundary layer and promoted flow mixing between layers. The average Nusselt number for corrugated tubes (pitch 10 mm) increased by 25% and 55% for corrugation depths of 0.1 and 0.13, respectively. However, the friction factor for corrugated tubes with (e/dh) = 0.1 and 0.13 was found to be higher than that of smooth tubes by 66%, 133%, and 130%. With the incorporation of both corrugated tubes and rod baffles, the thermal enhancement factor reached 1.9 for x/d = 1.25 and 1.97 for x/d = 1.375 at the same pumping power (50 mm). This study provides valuable insights into the effects of corrugated tubes and rod baffles on heat exchanger performance for various Reynolds numbers. [ABSTRACT FROM AUTHOR]

Air flow characteristics of an open cavity have been numerically examined by using different turbulence models of Detached Eddy Simulation (DES), k-ε Realizable, k-ω Shear Stress Transport (SST) and Large Eddy Simulation (LES) based on an experimental study of open literature. Numerical results of transient analyses have been compared to experimental results at cavity length-based Reynolds number of Re = 4600. Pressure distributions, streamline patterns, streamwise velocity components, mean velocity values and their vectors have been given in terms of contour graphics. Moreover, velocity profiles have been presented. Pressure fluctuations have been triggered by flow separation and its reattachment. Due to upstream separation of boundary layer, there was curved boundary layer obtained between the outer potential-flow-like and the recirculation zones. As a result, negative velocity values are evidence for rotational flows affected by formation of secondary flows in the cavity. Furthermore, lower pressure region has been observed as a result of rotational flow which was powerful in the open cavity. Numerical results of DES and LES turbulence models are in good agreement with the results of reference study. As the numerical results obtained by LES turbulence model are approximately same with those of experimental reference study, LES turbulence model is mostly recommended. As an option to these turbulence models, k-ω SST model could be utilized for limited computer capacity. However, k-ε Realizable model is not sufficient for capturing rotational flows which are very effective in terms of present case. [ABSTRACT FROM AUTHOR]

Numerical investigation of a compressible fluid in a two-dimensional rectangular lid-driven cavity (LDC) with a vertical temperature gradient is performed by solving the compressible Navier–Stokes equation. Here, we explore the role of aspect ratio (AR) (width/height) on the vorticity dynamics and redistribution by considering three ARs of 1:1, 2:1, and 3:1. The onset and propagation of the instability are explored via time-resolved and instantaneous distributions of vorticity, time-series of streamwise velocity, and its associated spectra. The flow physics reveal that the precessing vortical structures in certain square sub-cells of the rectangular LDC resemble that of orbital motion with a primary core eddy surrounded by gyrating satellite vortices, typical of a supercritical flow in a square LDC. Upon increasing the AR, there is a major shift in the vorticity transfer from the top right corner (acting as the source of maximum vorticity generation) toward the left square sub-cells in the domain. This is further aided by the convective motion due to the imposed destabilizing vertical thermal gradient. The spectra demonstrate that a multi-periodic, chaotic flow is the consistent flow feature for the rectangular LDC for Re = 5500, irrespective of the AR. The compressible enstrophy budget of the rectangular LDC with varying AR is computed for the first time. This shows the dominance of the baroclinic vorticity over the viscous diffusion terms, which was conceived of as the major contributor to the creation of rotational flow structures. [ABSTRACT FROM AUTHOR]

A class of exact solutions to the Navier–Stokes equations for rotational incompressible flows is obtained. A three-parameter family of solutions in a ball, spherical layers, and the entire space is constructed. [ABSTRACT FROM AUTHOR]

Optical centrifuges are laser-based molecular traps that can rotationally accelerate molecules to energies rivalling or exceeding molecular bond energies. Here we report time and frequency-resolved ultrafast coherent Raman measurements of optically centrifuged CO2 at 380 Torr spun to energies beyond its bond dissociation energy of 5.5 eV (Jmax = 364, Erot = 6.14 eV, Erot/kB = 71, 200 K). The entire rotational ladder from J = 24 to J = 364 was resolved simultaneously which enabled a more accurate measurement of the centrifugal distortion constants for CO2. Remarkably, coherence transfer was directly observed, and time-resolved, during the field-free relaxation of the trap as rotational energy flowed into bending-mode vibrational excitation. Vibrationally excited CO2 (ν2 > 3) was observed in the time-resolved spectra to populate after 3 mean collision times as a result of rotational-to-vibrational (R-V) energy transfer. Trajectory simulations show an optimal range of J for R-V energy transfer. Dephasing rates for molecules rotating up to 5.5 times during one collision were quantified. Very slow decays of the vibrational hot band rotational coherences suggest that they are sustained by coherence transfer and line mixing. In this work the authors use coherent anti-Stokes Raman scattering to study collisional vibrational excitation in highly rotationally excited CO2 molecules prepared in an optical centrifuge. [ABSTRACT FROM AUTHOR]

The response characteristics of large-diameter monopiles under lateral loads obviously differ from those of traditional small-diameter piles. To investigate the failure mechanism and soil resistance of laterally-loaded large-diameter monopiles, a series of finite element analyses of monopiles in soft clay were conducted. From the analysis results, an additional rotational soil flow can be observed in the large-diameter soil-monopile system, but there is only a slight difference (approximately 2–6%) in the bearing capacity of monopiles when the p–y method is utilized with and without rotational soil flow. Consequently, the consideration of the wedge-full-flow mechanism is sufficiently accurate for the monopile design of offshore wind turbines. Moreover, the base shear force and bending moment have an important influence on the lateral behaviour of large-diameter monopiles, and ignoring these additional base resistance components can greatly underestimate (even up to − 30%) the lateral bearing capability and lateral stiffness of semi-rigid and rigid large-diameter monopiles. Modal analysis of the 5 MW wind turbine also shows that this ignorance can lead to an underestimation (nearly 13.0%) of the structure's natural frequency. To consider the contributions of the additional base resistances to the lateral stiffness and bearing capacity, we developed two new T–u and M–φ springs to expand the current p–y method. [ABSTRACT FROM AUTHOR]

[Display omitted] Protein nanofibrils (PNF) resulting from the self-assembly of proteins or peptides can present structural ordering triggered by numerous factors, including the shear flow. We hypothesize that i) depending on the contour length of the PNF and the magnitude of the shear rate applied to the PNF dispersion, they exhibit specific orientation, and ii) it is possible to predict the alignment of PNF by establishing a flow-alignment relationship. Understanding such a relationship is pivotal to improving the fundamental knowledge and application of fibril systems. We use β -lactoglobulin PNF aqueous dispersions with different average contour lengths but equal persistence lengths. We employ simple shear-dominated microfluidic devices with state-of-the-art imaging techniques: flow-induced birefringence (FIB) and micro-particle image velocimetry (μ -PIV), to probe the effect of shear flow on PNF alignment. We provide an empirical relationship connecting the birefringence Δ n (quantifying the extent of PNF alignment), and the Péclet number Pe (correlating the shear rate of the flow relative to the rotational diffusion of PNF) to understand the flow-alignment behavior of PNF under shear-dominated flows. Furthermore, we assess the alignment and flow profile of PNF at both high and low flow rates. The length of PNF emerges as a controlling parameter capable of modulating PNF alignment at specific shear rates. Our results shed new insights into the hydrodynamic behavior of PNF, which is highly relevant to various industrial processes involving the fibril systems. [ABSTRACT FROM AUTHOR]

As key devices to lift deep-sea oil and gas, mixed-flow pumps can transport multiphase flow with high inlet gas volume fraction (IGVF). Performance parameters of mixed-flow pumps may be disturbed by the complex flow and gas–liquid distribution under various conditions that need an accurate two-phase flow numerical methodology for prediction. In this work, the gas–liquid mixed flow performance of a mixed-flow pump is investigated based on the modified drag force model, which considers the bubble deformation at high IGVF. The effects of the IGVF on pressure increment and gas phase distribution are explored. The influences of flow rate and rotational speed are studied as well. Experiments are conducted to obtain performance parameters and gas–liquid distribution images. The results show that performance parameters and gas–liquid distribution predicted in simulations are consistent with those obtained in experiments. The pressure increment of the mixed-flow pump is decreased as the IGVF and flow rate increase. Especially when IGVF increases from 5% to 15%, the pressure increment drops sharply, which is the surging phenomenon. The increased speed may improve the performance. The evolution of gas phase distribution is deeply analyzed to improve the understanding of gas–liquid flow characteristics in mixed-flow pumps. [ABSTRACT FROM AUTHOR]

A heat transport system based on heat pipes is developed and analyzed. The aim is to increase the efficiency of electrical engines by transferring dissipation‐related heat. The system performance is investigated experimentally by varying the temperature range and the supplied heat flow as well as the rotational speed. The thermal resistance of the system is reduced by 98 % compared to pure heat conduction. The rotation of the system has no significant influence on the thermal resistance, which is constant until the power limit is reached. The power limit is dependent on temperature and approximately coincides with the capillary force limit. [ABSTRACT FROM AUTHOR]

The rheometric techniques available for the evaluation of mortars involve a different set of flow conditions. Squeeze flow is based on the compression of the sample with gap reduction and geometric restrictions, providing important information even when phase separation occurs and an evaluation in conditions similar to those found in several practical situations for many classes of materials, including cement‐based and ceramics. Traditional squeeze flow results are related to bulk normal force and height variation of a sample compressed between parallel plates. Additional information regarding boundary conditions at the interfaces or phenomena related to differential flow can be obtained through further instrumentation of the test. The combination of squeeze flow and a pressure mapping technique has been recently proposed, with great potential for the analysis of cement‐based materials and other granular suspensions. In this work, four mortars were evaluated by the pressure mapped squeeze flow (PMSF) method in two different displacement rates, and new ways to analyze the results were developed to expand the understanding of the flow through the technique, including plotting the pressure along multiple circumferences and an analysis of variation in each radial position. PMSF results were also compared to rotational rheometry and flow table tests for the first time, and concepts of interparticle separation were employed to discuss microstructural aspects of the flow. Due to the variety of mix designs (admixtures, particle size distribution, air content, water content, and other factors), the mortars presented diverse behaviors, ranging from primarily viscous or plastic flows to more granular responses (related to friction between particles with localized formation of jammed structures due to liquid phase migration). This work is part of an effort to establish a foundation for PMSF as a rheometric method that can be used for the analysis of a wide range of materials. [ABSTRACT FROM AUTHOR]

This work studied a high winds‐producing bow echo that occurred over South China in the pre‐rainy season using radar observations and high‐resolution analyses from the Variational Doppler Radar Analysis System. The bow echo developed from a quasi‐linear convective system (QLCS) and acquired a well‐defined bow shape after merging with a pre‐line convective cell (CC). Interestingly, the rear‐inflow jet (RIJ), which has been well recognized to play a key role in the formation of a bow echo, was not found in this merger‐formation bow echo (MFBE). The reason is that the QLCS developed in the monsoon environment of high humidity and weak vertical wind shear, leading to a weak cold pool and line‐end vortices. A new pathway of bow echo formation was proposed which highlighted the importance of the low‐level mesovortex (MV) on the leading edge of the QLCS. Vertical vorticity budget analyses revealed that the MV originated from a weak vertical vorticity band ahead of the QLCS and grew rapidly during the merger, because of the enhanced low‐level convergence in between which led to vortexgenesis via vertical stretching of vertical vorticity. The up‐scale growth of the MV produced a RIJ‐like flow wrapping cyclonically from north of the QLCS which forced the system to bulge out and finally evolve into a bow echo. This MV contributed foremost to the near‐surface gales as well. These findings shed light on the diverse formation mechanisms of bow echoes and associated high winds in the moist monsoon environment of South China. Plain Language Summary: Bow echoes represent a kind of linear organized convective system presenting bowing segment which usually cause surface damaging winds. The well‐known formation mechanism is the partly acceleration of a quasi‐linear convective system (QLCS) resulting from a system‐scale flow named rear‐inflow jet (RIJ), which penetrates from the rear‐flank region protruding to the leading edge. This jet usually develops in response to the mid‐level pressure deficit induced by the vertical gradient of buoyancy, and can also be strengthened by line‐end vortices, that is, a pair of cyclonic and anticyclonic vortex couple located on the two sides. However, these two elements were rather weak in the bow echo event studied herein compared to the classical ones. Instead, a low‐level mesoscale vortex (MV) was intensified through the merger process, the vortical flow of which enhanced a unique rear‐inflow jet, causing the convective line to bulge out. Besides, the presence of this MV enhanced the near surface high‐winds significantly. This study documents an atypical pathway for a QLCS to evolve into a bow echo, where the low‐level MV dominates the formation of bowing segment. Key Points: A bow echo forms from the merger of a quasi‐linear convective system with a cell, featured by a weak cold pool and line‐end vorticesThe merger enhances the low‐level convergence and produces a mesoscale vortex on the leading edge of the quasi‐linear convective systemThe rotational flow of the mesoscale vortex greatly enhances a special rear‐inflow jet which in turn promotes the formation of a bow echo [ABSTRACT FROM AUTHOR]

This paper presents new results for the dynamic behaviour of fluid around a rotating turbulator in a channel. The turbulator has a propeller form which is placed inside a flat channel. The research was carried out using 3D numerical simulation. The rationale of the experiment was as follows: we put a propeller-turbulator inside a flat channel, and then we insert a water flow inside the channel. The turbulator rotates at a constant and uniform speed. The main points studied here are the effect of the presence of turbulator and its rotational direction on the flow behaviour behind the turbulator. The results showed that the behaviour of flow behind the turbulator is mainly related to the direction of turbulator rotating. Also, the studied parameters affect coefficients of drag force and power number. For example, when the turbulator rotates in the positive direction, the drag coefficient decreases in terms of rotational speed of the turbulator, while the drag coefficient increases in terms of rotational speed when the turbulator rotates in the negative direction. [ABSTRACT FROM AUTHOR]

Cylindrical cyclones play an important role in oil–water separation and sewage treatment in the petroleum industry. Here, we describe the characteristics of vibration induced by a two-phase rotational flow in a cylindrical cyclone. The cyclone operating parameters together with a dimensional analysis and multiphase flow numerical simulation were used to understand the flow field characteristics. The frequency and amplitude of pressure fluctuation were obtained by measuring pressure changes at points on the axis of the device. It shows that the pressure in a cylindrical cyclone varies periodically during separation and that fluctuation frequency and amplitude are related to the inlet velocity and flow split ratio. The effect of the overflow split ratio on the pressure fluctuation frequency is negligible, but increasing the overflow split ratio will cause greater fluctuation of the flow. For a cylindrical cyclone, the pressure fluctuation frequency can be calculated from the inlet velocity. Adjusting the inlet velocity and the overflow split ratio changes the mechanical response of the structure. The results of a modal analysis show that the structural vibration response is consistent with the response state of the lowest point of the internal central-vortex pressure and that both are in approximate circular motion. Furthermore, the frequency of pressure fluctuation induced by the flow is close to the intrinsic frequency of the structure with a single bottom constraint, which can cause unwanted resonance easily. Therefore, an appropriately added constraint on a cylindrical cyclone should be taken into consideration to avoid the resonance frequency. [ABSTRACT FROM AUTHOR]

Background and Objectives Pre-sedimentation basins are considered as the major and important components in water treatment process through conventional method. Because of the high cost of constructing these basins, which is approximately 30% of the total costs of water treatment plants, modeling and optimum performance of pre-sedimentation basins are very important. In pre-sedimentation basins, because of the existence of velocity gradients, secondary and rotational flows occur. In order to increase the performance of a pre-sedimentation basin (clarifier), it is essential to have a uniform and calm flow field. The use of suitable baffle configurations may help forming favorable flow field and increase the efficiency of the pre-sedimentation basins. In order to find the proper position of a baffle in a rectangular sedimentation basin, computational investigations are performed. The first step to optimize pre-sedimentation basin is accurate calculation of the velocity field and the volume of rotation zones. Flow guiding blades can also be used to depreciate the inlet jet and reduce turbulent kinetic energy. Because of the flow complexity and also the effects of scale, physical models can not solely provide a clear understanding of the physics governing the flow field and it is necessary to study this phenomenon numerically along with field and experimental studies. The numerical results were calibrated with experimental results of Shahrokhi et al. (2011) and Imam et al. (1984). Flow simulation was performed in 3D and flow velocity profiles were compared with the experimental results in different sections of a pre-sedimentation basin. Then, in order to sedimentation investigation in the pre-sedimentation basin, advection and dispersion equation of sediment concentration was solved simultaneously with the governing equations of flow. Methodology The first step to optimize pre-sedimentation basins is accurate simulation of the velocity field and the volume of rotation zones. In the present study, numerical simulation of flow was investigated in a pre-sedimentation basin using SSIIM and Fluent models. Continuity and momentum equations were solved using finite volume method. Flow analysis was done steady by the SIMPLE algorithm for velocity and pressure coupling. Discrete method of continuity equations, momentum, turbulent kinetic energy, Reynolds stress drop and discretion of pressure equation are standard. Findings The results of the vertical distribution of sediment concentration profiles in different sections of the basin were compared with the experimental and numerical results of other researchers. Finally, the effect of flow guiding blades on the flow pattern and the efficiency of sedimentation in the presedimentation ponds were investigated. The comparison showed that there is a good agreement between numerical and experimental study with an average error of 6%. Conclusion Flow rate is one of the effective parameters on creating a rotational zone inside the basins. With increasing the inlet flow rate from 0.002 to 0.01 cubic meters per second, the length of the rotational zone has increased 25% and the width of the rotating zone has increased 45%. The secondary and rotational currents formed at the entrance of the basin are two small rotational zones and approaching the middle of the basin and formation of flow separation zones, the number of rotating areas and their dimensions have increased. From the beginning to the middle of the basin, the shear stress is increased. In the sections x = 0.46 m and x = 0.82 m, the amount of shear stress is maximum. Amount of energy in the middle of the depth has decreased by 40% compared to the water level and about 60% compared to the floor of the sedimentation basin. It showed that there is a good agreement between the numerical and experimental results. It also indicated high ability of SSIIM in predicting distribution of sediment concentration profiles in pre-sedimentation basins. With increasing flow depth, the sediment concentration decreases. In the section x = 1.58 m, the sediment concentration near the free surface is 44 mg L-1, which decreased by 57.48% compared to the concentration of sediment in the basin bed. In the case without the guide blade, near the free surface of the stream, the sediment concentration was decreased. Also, in the middle of the basin, due to the turbulence of the flow and the rotational areas, the secondary current strength was maximal and decreased as it approached the end of the basin. [ABSTRACT FROM AUTHOR]

Smooth eye movements are common during natural viewing; we frequently rotate our eyes to track moving objects or to maintain fixation on an object during self-movement. Reliable information about smooth eye movements is crucial to various neural computations, such as estimating heading from optic flow or judging depth from motion parallax. While it is well established that extraretinal signals (e.g., efference copies of motor commands) carry critical information about eye velocity, the rotational optic flow field produced by eye rotations also carries valuable information. Although previous work has shown that dynamic perspective cues in optic flow can be used in computations that require estimates of eye velocity, it has remained unclear where and how the brain processes these visual cues and how they are integrated with extraretinal signals regarding eye rotation. We examined how neurons in the dorsal region of the medial superior temporal area (MSTd) of two male rhesus monkeys represent the direction of smooth pursuit eye movements based on both visual cues (dynamic perspective) and extraretinal signals. We find that most MSTd neurons have matched preferences for the direction of eye rotation based on visual and extraretinal signals. Moreover, neural responses to combinations of these signals are well predicted by a weighted linear summation model. These findings demonstrate a neural substrate for representing the velocity of smooth eye movements based on rotational optic flow and establish area MSTd as a key node for integrating visual and extraretinal signals into a more generalized representation of smooth eye movements. [ABSTRACT FROM AUTHOR]

A comparative experimental study of a physical model of a stirred ladle for a rotor-injector aluminum degassing system in the turbulent regime has been carried out. A quantitative analysis of the gaseous oxygen mass transfer to the water in a physical model is performed by evaluating the power consumption and mass transfer capacity employing the typical methods used in mechanically stirred tanks. Three rotor injector devices were compared, including two conventional designs and one new rotor design. The rotors were evaluated as a function of the rotational speed and gas flow rates. The conventional rotors exhibited similar performance, while the new design consumed more power when operating at high gassing flow rates and rotational speeds resulting in a higher breakup rate of bubbles and promoting a better formation of tiny bubbles, which are better distributed over the entire ladle. This behavior avoids bubbles rising freely to the free surface; so that the gas hold-up increases leading to an improved mass transfer capacity when using this rotor-injector. The results reported in this work agreed with previously reported works in the literature. • Rotor-injectors for degassing aluminum have been evaluated in terms of power drawn and mass transfer. • A typical approach as used in stirred vessels allowed evaluating the devices. • A novel rotor has been analyzed and compared against two commercial designs used in industrial operations. • The novel rotor draws more power, but it exhibits better mass transfer capacity. [ABSTRACT FROM AUTHOR]

The triple decomposition of a velocity gradient tensor provides an analysis tool in fluid mechanics by which the flow can be split into a sum of irrotational straining flow, shear flow, and rigid body rotational flow. In 2007, Kolář formulated an optimization problem to compute the triple decomposition [V. Kolář, "Vortex identification: New requirements and limitations," Int. J. Heat Fluid Flow 28, 638–652 (2007)], and more recently, the triple decomposition has been connected to the Schur form of the associated matrix. We show that the standardized real Schur form, which can be computed by state of the art linear algebra routines, is a solution to the optimization problem posed by Kolář. We also demonstrate why using the standardized variant of the real Schur form makes computation of the triple decomposition more efficient. Furthermore, we illustrate why different structures of the real Schur form correspond to different alignments of the coordinate system with the fluid flow and may, therefore, lead to differences in the resulting triple decomposition. Based on these results, we propose a new, simplified algorithm for computing the triple decomposition, which guarantees consistent results. [ABSTRACT FROM AUTHOR]

In this study, the orientation dependent hardness and creep properties of heavy ion irradiated Zr-2.5Nb pressure tube alloy are investigated by nanoindentation. The indentation tests are conducted along the axial direction (AD) and the transverse direction (TD) relative to the tube. TD samples demonstrate a dependence of the indentation size effect on irradiation damage, which is related to the decrease of the plastic zone size as irradiation damage increases. The hardness of AD and TD samples shows linear dependence on the square root of the irradiation damage density. The transition of the flow pattern from laminar to rotational flow happens in TD samples when the indentation is deeper than 1 μm; rotational flow is expected to be dominant after irradiation. AD samples exhibit laminar flow regardless of indentation depth or irradiation damage. The creep distance is increased for AD while it decreased for TD after irradiation. The creep process in the unirradiated materials and irradiated TD samples is found to be plasticity creep (dislocation glide plus climb). However, for AD samples, the mechanism is changed to power-law creep after 0.6 dpa irradiation. Both the hardness and creep results can be related to the anisotropic deformation mechanisms in the samples. [ABSTRACT FROM AUTHOR]