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We theoretically study the conformational and dynamical properties of semiflexible active polar ring polymers under linear shear flow. A ring is described as a continuous semiflexible Gaussian polymer with a tangential active force of a constant density along its contour. The linear but non-Hermitian equation of motion is solved using an eigenfunction expansion, which yields activity-independent, but shear-rate-dependent, relaxation times and activity-dependent frequencies. As a consequence, the ring's stationary-state properties are independent of activity, and its conformations and rheological properties are equal to those of a passive ring under shear. The presence of characteristic time scales by relaxation and the activity-dependent frequencies give rise to a particular dynamical behavior. A tank-treading-like motion emerges for long relaxation times and high activities, specifically for stiff rings. In the case of very flexible polymers, the relaxation behavior dominates over activity contributions suppressing tank-treading. Shear strongly affects the crossover from a tank-treading to a relaxation-dominated dynamics, and the ring polymer exhibits tumbling motion at high shear rates. This is reflected in the tumbling frequency, which displays two shear-rate dependent regimes, with an activity-dependent plateau at low shear rates followed by a power-law regime with increasing tumbling frequency for high shear rates. [ABSTRACT FROM AUTHOR]

Biomolecular condensates play a key role in cytoplasmic compartmentalization and cell functioning. Despite extensive research on the physico-chemical, thermodynamic, or crowding aspects of the formation and stabilization of the condensates, one less studied feature is the role of external perturbative fluid flow. In fact, in living cells, shear stress may arise from streaming or active transport processes. Here, we investigate how biomolecular condensates are deformed under different types of shear flows. We first model Couette flow perturbations via two-way coupling between the condensate dynamics and fluid flow by deploying Lattice Boltzmann Molecular Dynamics. We then show that a simplified approach where the shear flow acts as a static perturbation (one-way coupling) reproduces the main features of the condensate deformation and dynamics as a function of the shear rate. With this approach, which can be easily implemented in molecular dynamics simulations, we analyze the behavior of biomolecular condensates described through residue-based coarse-grained models, including intrinsically disordered proteins and protein/RNA mixtures. At lower shear rates, the fluid triggers the deformation of the condensate (spherical to oblated object), while at higher shear rates, it becomes extremely deformed (oblated or elongated object). At very high shear rates, the condensates are fragmented. We also compare how condensates of different sizes and composition respond to shear perturbation, and how their internal structure is altered by external flow. Finally, we consider the Poiseuille flow that realistically models the behavior in microfluidic devices in order to suggest potential experimental designs for investigating fluid perturbations in vitro. [ABSTRACT FROM AUTHOR]

Experimental studies of the dynamics of shear flow and turbulence spreading at the edge of tokamak plasmas are reported. Scans of line-averaged density and plasma current are carried out while approaching the Greenwald density limit on the J-TEXT tokamak. In all scans, when the Greenwald fraction f G = n ¯ / n G = n ¯ / ( I p / π a 2 ) increases, a common feature of enhanced turbulence spreading and edge cooling is found. The result suggests that turbulence spreading is a good indicator of edge cooling, indeed better than turbulent particle transport is. The normalized turbulence spreading power increases significantly when the normalized E × B shearing rate decreases. This indicates that turbulence spreading becomes prominent when the shearing rate is weaker than the turbulence scattering rate. The asymmetry between positive/negative (blobs/holes) spreading events, turbulence spreading power and shear flow are discussed. These results elucidate the important effects of interaction between shear flow and turbulence spreading on plasma edge cooling.

We performed a series of molecular dynamics simulations on monodisperse polymer melts to investigate the formation of shear banding. Under high shear rates, shear banding occurs, which is intimately accompanied by the entanglement heterogeneity. Interestingly, the same linear relationship between the end-to-end distance Ree and entanglement density Z is observed at homogeneous flow before the onset of shear banding and at the shear banding state, where Ree ∼ ln ( W i 0.87 ) − ξ 0 Z is proposed as the criterion to describe the dynamic force balance of the molecular chain in flow with a high rate. Deviating from this relation leads to a force imbalance and results in the emergence of shear banding. We establish a scaling relation between the disentanglement rate Vd and the Weissenberg number Wi as V d ∼ W i 0.87 for stable flow in homogeneous shear and shear banding states. The formation of shear banding prevents chains from further stretching and disentanglement. The transition from homogeneous shear to shear banding partially dissipates the increased free energy from shear and reduces the free energy of the system. [ABSTRACT FROM AUTHOR]

Kinetics of force-mediated chemical reactions of end-tethered polymers with varying chain length N in varying shear rate flow γ ̇ are explored via coarse-grained Brownian dynamics simulations. At fixed γ ̇ , force F along a polymer increases linearly with N as previously predicted; however, contrary to existing theory, the F(N) slope increases for N above a transition length that exhibits minimal dependence on γ ̇ . Force profiles are used in a stochastic model of a force-mediated reaction to compute the time for x percent of a polymer population to experience a reaction, tx. Observations are insensitive to the selected value of x in that tx data for varying N and γ ̇ can be consistently collapsed onto a single curve via appropriate scaling, with one master curve for systems below the transition N (small N) and another for those above (large N). Different force scaling for small and large N results in orders of magnitude difference in force-mediated reaction kinetics as represented by the population response time. Data presented illustrate the possibility of designing mechano-reactive polymer populations with highly controlled response to flow across a range in γ ̇ . [ABSTRACT FROM AUTHOR]

We analyze the shear response of grafted polymer chains in shear flow via coarse-grained molecular dynamics simulations with an explicit solvent. We find that the solvent flow penetrates into almost the whole brush for "mushroom"-type brushes but only a few bond distances for dense brushes. In all cases, the external stress on the wall equals the entropic stress associated with the distorted polymer conformations. We find that the external stress increases linearly with shear rate at low rates and sublinearly at high rates. The transition from linear to sublinear scaling occurs where chains react to flow by reorienting. Sublinear scaling with shear rate disappears if the shear rate is nondimensionalized with the effective relaxation time of chain subsegments located in the outer part of the brush that experiences flow. [ABSTRACT FROM AUTHOR]

Shear flow has been theoretically predicted to suppress the undulation of surfactant bilayers and generate negative tension, which is considered to be a driving force of the transition from the lamellar phase to the multilamellar vesicle phase in surfactant/water suspensions, the so-called onion transition. We performed coarse-grained molecular dynamics simulations of a single phospholipid bilayer under shear flow to clarify the relationship between the shear rate, bilayer undulation, and negative tension, providing molecular-level insight into the undulation suppression. An increasing shear rate suppressed bilayer undulation and increased negative tension; these results are consistent with theoretical predictions. The non-bonded forces between the hydrophobic tails facilitated negative tension, whereas the bonded forces within the tails suppressed it. The force components of the negative tension were anisotropic in the bilayer plane and prominently changed in the flow direction, although the resultant tension was isotropic. Our findings regarding a single bilayer will underlie further simulation studies of multilamellar bilayers, including inter-bilayer interactions and topological changes of bilayers under shear flow, which are essential for the onion transition and are unresolved in the theoretical and experimental studies. [ABSTRACT FROM AUTHOR]

Mechanical properties of glass are critical for technical applications, thus comprehending the material response to mechanical tests is of great importance. In this study, we employ the nanoindentation combined with nanoscale infrared (nano-IR) spectroscopy combined with scattering-type scanning near-field optical microscopy (s-SNOM) and ToF-SIMS, to elucidate the nanoindentation rate dependence of plastic deformation of soda lime silicate glass. Experiment results show that the nanohardness and elastic modulus of soda lime silicate (SLS) glass exhibit a strong dependence on loading rate, while those of fused quartz (FQ) shows a much weaker dependence. The residual indent volume at fast loading conditions is smaller for SLS glass than FQ; but as the loading rate decreases, the residual indent volume of FQ and SLS glass becomes similar. The indent volume of SLS glass after sub- T g annealing (reverting subsurface densification) shows negligible dependence on the loading rate, suggesting that the densification of SLS glass is strongly enhanced at lower indentation rate, but the shear flow is independent or weakly dependent. Using nanoscale infrared spectroscopy and ToF-SIMS techniques, the sodium ion migration in SLS glass surface in the indent is found to be associated with the subsurface densification. These results suggest the possible role of highly mobile sodium ions on in nano- and micro-scale plastic deformation behavior of SLS glass. [ABSTRACT FROM AUTHOR]

For blending immiscible polymers, such as in the toughening modification of polylactide (PLA) via blending with rubbery materials, interfacial compatibilization is of great significance while the mechanism, especially the role of interfacial rheology, remains elusive. In this study, styrene-butadiene block copolymer elastomer (SBC) was employed to toughen PLA and a dumbbell-shaped Janus nanoparticle (JNP) consisting of polymethyl methacrylate and polystyrene spheres with equal size (∼80 nm) was used as the compatibilizer. Located at the interface, JNPs exhibited a great compatibilization efficiency in PLA/SBC blends, as demonstrated by the good morphology stabilization against droplet coalescence under static annealing and low shear flow conditions, as well as by the resistance against droplet breakup under high shear flow conditions. Moreover, as revealed from the linear viscoelasticity of JNP compatibilized blends, when JNP loading is more than 2 phr, aside from shape relaxation, an interfacial relaxation dominated by Marangoni stress was observed, indicating the possibility of particle redistribution on droplet surfaces. However, when loading is more than 4 phr, relaxations in the terminal zone no longer exist, implying the possible formation of a particle network on the droplet surface. This is consistent with the mechanical properties. The blend shows the greatest toughness at JNP loading around 3 phr, while the toughness is very poor when JNP loading is either too low or too high. This suggests interfacial relaxation to be crucial to guarantee a good toughening effect of SBC in PLA. [ABSTRACT FROM AUTHOR]

We propose a torque rheometer coupled with an ultrasonic velocity profiler (UVP) for evaluating multiphase fluids as bulk rheology in oscillatory shear flows. The rheometer mainly consists of wide-gap coaxial cylinders, where the outer cylinder is sinusoidally oscillated and the inner cylinder is fixed to a torque sensor for measuring the wall shear stress. Based on Cauchy's equation of motion, the spatiotemporal distribution of the shear stress is obtained from the velocity information and the wall shear stress as a boundary condition. This rheometer was applied to a carboxymethyl cellulose aqueous solution and compared with a standard torque-type rheometer. The results of the evaluated viscoelastic properties agreed well with each other, indicating the validity of the proposed rheometry. To further investigate the applicability of the rheometer to multiphase fluids, suspensions of solid spherical particles with a diameter of 220 μ m with volume fraction of 0.8–3.4% were measured, which are out of the applicable ranges of the standard rheometer. For volume fractions up to 3% where the UVP measurement is available, the relative viscosity agrees well with a theoretical formula. This indicates the applicability of the method to examine multiphase fluids. [ABSTRACT FROM AUTHOR]

In this work, the doubly periodic shear layers are employed to underpin the vortex dynamics associated with the perturbed free shear layers using the lattice Boltzmann method with the Bhatnagar–Gross–Krook collision model. The effect of (i) width between shear layers, (ii) modes of perturbation, (iii) the strength of perturbation, and (iv) thickness of a shear layer on roll-up formation, vortex interactions, pairings, and the generation of thin filaments is studied in detail with the evolution kinetic energy, enstrophy, and palinstrophy for Reynolds number, Re = 30 , 000 . The formation of thin vorticity braids and vortex merging causes the production of vorticity gradients and a rise in the palinstrophy. No compelling interplay is observed with corotating or counter-rotating vortices for a minimum separation distance ( S 1 ) between two opposite vorticity strips. The counter-force from each layer creates a jet whose properties differ from those of a single shear layer. However, the evolution of multiple pairs of shear layers produces smaller vortices of lower strength and enhances the growth of palinstrophy and decay of kinetic energy and enstrophy. The rise in the momentum thickness is observed for the interactive flows ( S 2 ≤ S 1 ), while the non-interactive flow ( S 2 > S 1 ) shows constant momentum thickness. The increased perturbation strength quickens the roll-up of shear layer and enhances the growth of palinstrophy. Thick shear layers evolves with dipole-like structures and slows down the decay of kinetic energy and enstrophy compared to thin shear layer flows. It generates family of thin vortex filaments and influences the rapid growth of vorticity gradients and positive Okubo–Weiss-Q-quantity. [ABSTRACT FROM AUTHOR]

The current investigation focuses on examining viscous corrections for viscous potential flow (VCVPF) analysis concerning the Rayleigh–Taylor instability occurring at the interface of a Rivlin–Ericksen (R–E) viscoelastic fluid and a viscous fluid during the transfer of heat and mass between phases. The R–E model is a fundamental framework in the study of viscoelastic fluids, providing insights into their complex rheological behavior. It characterizes the material's response to both deformation and flow, offering valuable predictions for various industrial and biological applications. Within the framework of viscous potential flow (VPF) theory, viscosity is exclusively accounted for in the normal stress balance equation, disregarding the influence of shearing stress entirely. This study introduces a viscous pressure term into the normal stress balance equation alongside the irrotational pressure, presuming that this addition will improve the discontinuity of tangential stresses at the fluid interface. Through derivation of a dispersion relationship and subsequent theoretical and numerical stability analyses, the stability of the interface is investigated across various physical parameters. Multiple plots are generated using the dispersion relation, and a comparative analysis between VPF and VCVPF is conducted to establish improved stability criteria. The investigation highlights that the combined impact of heat/mass transport and shearing stress serves to delay the instability of the interface. [ABSTRACT FROM AUTHOR]

The effect of side holes morphology changes in double J stent (DJS) on encrustation was analyzed using computational fluid dynamics (CFD). We analyzed DJS side holes with inner diameter of 1 mm and outer diameters of 1 (type A), 1.2 (type B) and 1.4 (type C) mm, respectively. Concentric stenosis with three intraureteral degree (0%, 12%, and 88%) was analyzed. The flow rate, shear stress and wall shear stress (WSS) distribution were investigated. Urine flow through SH1 before the ureteropelvic junction (UPJ) differed based on the ureteral stenosis degree. The sum of flow rates through the SHs increased with diameter. In the stented ureter with 12% stenosis, the flow rate through SH1 approximately doubled than that without ureteral stenosis, and the flow rate through SH1 was maximal for the type 'C' stent in both 12% and 88% ureteral stenosis. The mean shear stress in the SHs increased with the degree of stenosis. The WSS around the SHs was higher for type 'C' than types A and B. From the flow rates and shear stresses in and around the SHs, the larger SH diameter of the DJS from the UPJ to mid-ureter is expected to induce encrustation reduction, especially in patients with urinary lithiasis. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of plasma actuation on cavitation in the flow field around a hydrofoil, the RNG k-ε turbulence model with density correction, the Schnerr--Sauer cavitation model, and the plasma phenomenological model were used to analyze the influence of forward and reverse plasma actuation on the cavitation characteristics of the NACA66(MOD) hydrofoil at an angle of attack of 8. The cavitation number of the incoming flow was 0.99. The results showed that under the positive excitation condition, the cavitation volume on the suction side of the hydrofoil was reduced by about 30%, and the time-averaged lift--drag ratio was reduced by about 5%, which had little influence on the reentrant jet, vortex and shear flow. Therefore, the cavitation suppression effect on the hydrofoil flow field was weak. Under the condition of reverse actuation, the volume of cavitation on the suction side of the hydrofoil was reduced by about 87%, and the time-averaged lift--drag ratio was increased by about 21%, which effectively worsened the development conditions of cavitation. By greatly reducing the intensity of the re-entrant jet and eliminating the vortex and shear flow in the flow field, cavitation in the hydrofoil flow field was obviously suppressed. This shows that reasonable plasma actuation is an effective means to control hydrofoil cavitation. [ABSTRACT FROM AUTHOR]

This paper investigates the shape and hydrodynamic characteristics of the sand bed at the junction of urban pipelines and their relationship with the flow ratio. Various hydrodynamic and morphological features, including shear layers, spiral cells, and scour pits. The dataset used for analysis consists of a three-dimensional time-averaged velocity field, turbulence, bed morphology, and confluence morphology of equilibrium phases obtained under controlled laboratory conditions. For large flow ratios (q*), significant local erosion occurs near the downstream shear plane at the junction. When the flow of tributaries surpasses that of the main stream, the strength and downstream extension of the spiral cell blocks increase. The max Reynolds number shear stress predominantly concentrates in the middle region of the water depth, aligning with the turbulent kinetic energy representation of the shear layer. Keeping the flow ratio constant, the velocity, turbulent kinetic energy, and absolute Reynolds shear stress all escalate with increased flow. [ABSTRACT FROM AUTHOR]

Comprehensive coherent structures around a surface-mounted low aspect ratio square cylinder in uniform flow with an oblique angle of $45^{\circ }$ were investigated for cylinder-width-based Reynolds numbers of 3000 and 10 000 by direct numerical simulation based on a topology-confined mesh refinement framework. High-resolution simulations and the critical-point concept were scrutinized to reveal for the first time the reasonable and compatible topologies of flow separation and complete near-wall structures, due to their extensive impact on various engineering applications. Large-scale horseshoe vortices are observed at two notable foci in the viscous sublayer. Within this layer, a wall-parallel jet is formed by downflow intruding into the bottom surface at the half-saddle point, then deflecting in the upstream direction and finally penetrating the bottom surface until the half-saddle point. A pair of conical vortices on the cylinder's top surface switch themselves on two sides of the square cylinder, where the switching frequency is identical with that of the sway of the side shear layer. The undulation of the Kelvin–Helmholtz instability is identified in the instantaneous development of a conical vortex and side shear layer, where the scaling of the ratio of the Kelvin–Helmholtz and von Kármán frequencies follows the power-law relation obtained by Lander et al. (J. Fluid Mech. , vol. 849, 2018, pp. 1096–1119). Large-scale arch-shaped vortex is often detected in the intermediate wake region of a square cylinder, involving two interconnected portions, such as the leg portion separated from leeward surfaces and head portion rolled up from the top surface. The leg portion of the arch-shaped vortex was rooted by two foci near the bottom-surface plane. [ABSTRACT FROM AUTHOR]

We investigate the dynamics of a gas jet impinging perpendicular to a thin liquid film dragged by a rising vertical substrate. This configuration is relevant to the jet-wiping process in hot-dip galvanization and it is unstable. Previous studies analysed the dynamics of the instability in the case of liquids with low Kapitza numbers (highly viscous liquids), more amenable to experimental and numerical investigations. This work extends the previous investigations by focusing on the wiping at much higher Kapitza numbers, which are more relevant to the galvanizing process. The simulations are carried out by combining volume of fluid and large-eddy simulations, and the dynamics of the gas–liquid interaction is analysed using extended multiscale proper orthogonal decomposition. The simulations allowed for analysing the jet-wiping instability in new flow conditions. Despite the largely different conditions, the results show that the interaction between the gas jet and the liquid film is qualitatively similar, featuring two-dimensional waves in the liquid correlated with oscillations and deflections of the gas jet in all cases. The wave characteristics (e.g. frequency and propagation speed) scale remarkably well using the Shkadov-like scaling based on the liquid, suggesting a dominant role of the liquid film in the coupling, and potentially enabling extrapolation of the results to a broader range of wiping conditions. Finally, we use the numerical results to discuss the limitations of liquid-film models, which constitute currently the only possible approach to study the jet-wiping process in industrial conditions. [ABSTRACT FROM AUTHOR]

The linear stability of plane Couette–Poiseuille flow (CPF) is studied with the physical effects of stratification, rotation and viscosity all included for the first time together. With no stratification, two instability mechanisms are present due to the shear and rotation which, for the most part, do not interact as they favour different forms of two-dimensionality. However, there are some small parts of parameter space where new three-dimensional instability appears indicating that Rayleigh's criterion is also violated in parameter space beyond where shear instability is expected. No fully localised centrifugal instabilities can be found for CPF, but they are shown to exist if the base flow shear has a maximum in the domain (the base flow needs to be at least cubic in the cross-stream variable rather than just quadratic as in CPF). With stable stratification present, new instabilities are found due to the combined effects of stratification and rotation, but only some appear to be of the resonance-type associated with the strato-rotational instability. The other unstable branches are more accurately interpreted as a stratification-modified centrifugal instability. Three-dimensional versions of this violate Rayleigh's criterion even when this is extended to include stratification. When stratification is stronger than rotation, the resonance-type instabilities are only dominant for cyclonic flows. [ABSTRACT FROM AUTHOR]

We consider a two-dimensional, two-layer, incompressible, steady flow, with vorticity which is constant in each layer, in an infinite channel with rigid walls. The velocity is continuous across the interface, there is no surface tension or difference in density between the two layers, and the flow is inviscid. Unlike in previous studies, we consider solutions which are localised perturbations rather than periodic or quasi-periodic perturbations of a background shear flow. We rigorously construct a curve of exact solutions and give the leading order terms in an asymptotic expansion. We also give a thorough qualitative description of the fluid particle paths, which can include stagnation points, critical layers, and streamlines which meet the boundary. [ABSTRACT FROM AUTHOR]

The extensive use of polypropylene (PP) in various industries has heightened interest in developing efficient methods for recycling and optimising its mixtures. This study focuses on formulating predictive models for the Melt Flow Rate (MFR) and shear viscosity of PP blends. The investigation involved characterising various grades, including virgin homopolymers, copolymers, and post-consumer recyclates, in accordance with ISO 1133 standards. The research examined both binary and ternary blends, utilising traditional mixing rules and symbolic regression to predict rheological properties. High accuracy was achieved with the Arrhenius and Cragoe models, attaining R2 values over 0.99. Symbolic regression further enhanced these models, offering significant improvements. To mitigate overfitting, empirical noise and variable swapping were introduced, increasing the models' robustness and generalisability. The results demonstrated that the developed models could reliably predict MFR and shear viscosity, providing a valuable tool for improving the quality and consistency of PP mixtures. These advancements support the development of recycling technologies and sustainable practices in the polymer industry by optimising processing and enhancing the use of recycled materials. [ABSTRACT FROM AUTHOR]

This work focuses on the heat transfer analysis of the magnetohydrodynamic peristaltic flow of blood through the gap between two coaxial flexible tubes of different wavelengths. In this model, the non-Newtonian biviscosity fluid is assumed to be blood, which is flowing through the annulus region between the inclined tubes. The governing equations for the considered problem are simplified under the assumptions of a zero Reynolds number and long wavelength approximations. An analytical expression for the temperature is obtained in its closed form, while a semi-analytical solution for the axial velocity of the moving fluid is determined using the homotopy perturbation method. Expressions for various flow variables such as shear stress, volumetric flow rate, pressure rise, and frictional force at the surface of inner and outer tubes are also obtained. In this work, we discussed the impact of various flow parameters like the Hartmann number, Grashof number, heat source, upper limit apparent viscosity coefficient, amplitude ratios of inner and outer tubes, radius ratio, and wavelength ratio on the above flow variables. The streamline contour plots are also drawn for the realization of the flow pattern of the blood inside the endoscope. The comparison of shear stresses for the peristaltic and rigid endoscopes and the validation of the present result with the previously established results are also discussed. A noteworthy observation drawn from the present model is that the pressure gradient enhances for increasing values of wavelength ratio when the wavelength of the inner tube is less than the wavelength of the outer tube, whereas the pressure gradient gets suppressed for increasing values of wavelength ratio when the wavelength of the inner tube is greater than the wavelength of the outer tube. From the present analysis, it is also found that the shear stress τrz of blood is the least for a peristaltic endoscope as compared to the rigid one. Therefore, this study may be applicable to medical practitioners for laparoscopic purposes, as a peristaltic endoscope may be a more appropriate device due to its flexibility than a rigid endoscope. [ABSTRACT FROM AUTHOR]

The aim of this study was to review the roles of endothelial cells in normal tissue function and to show how COVID‐19 disease impacts on endothelial cell properties that lead to much of its associated symptomatology. This places the endothelial cell as a prominent cell type to target therapeutically in the treatment of this disorder. Advances in glycosaminoglycan analytical techniques and functional glycomics have improved glycosaminoglycan mimetics development, providing agents that can more appropriately target various aspects of the behaviour of the endothelial cell in‐situ and have also provided polymers with potential to prevent viral infection. Thus, promising approaches are being developed to combat COVID‐19 disease and the plethora of symptoms this disease produces. Glycosaminoglycan mimetics that improve endothelial glycocalyx boundary functions have promising properties in the prevention of viral infection, improve endothelial cell function and have disease‐modifying potential. Endothelial cell integrity, forming tight junctions in cerebral cell populations in the blood–brain barrier, prevents the exposure of the central nervous system to circulating toxins and harmful chemicals, which may contribute to the troublesome brain fogging phenomena reported in cognitive processing in long COVID disease. [ABSTRACT FROM AUTHOR]

This study investigates the problem of low efficiency and the lack of a water supply at the Hemmat Water Intake, in Iran, where severe sediment accumulation was observed at the intake mouth. The Flow-3D software was used to simulate the flow patterns under various scenarios of hydraulic regimentation works. The considered parameters include: (i) three alternative locations of the spur dike (i.e., a spur dike placed on the opposite side of the intake inlet and aligned with the upstream edge of the intake, to be regarded as a witness spur dike; a spur dike at a distance DS of 7 m downstream of the witness spur dike, which implies a dimensionless distance DS/bi1 of 1/3, with bi1 being the intake opening width; and a spur dike at a distance of 7 m upstream of the witness spur dike with a dimensionless distance, still, of 1/3); (ii) four spur dike lengths, LS/Br, with LS being the effective spur dike length and Br the approach river width; and (iii) five spur dike deviation angles of 75, 90, 105, 120, and 135 degrees (the deviation angle is the angle between the spur dike axis and the original river-bank line from which the spur dike extends). The results showed that, with the increase in the relative spur dike length (LS/Br), the velocity of the flow entering the water intake increases by 11%. A spur deviation angle of 135 degrees increases the flow depth at the intake inlet by 9% compared to a smaller deviation angle of 75 degrees. In addition, the spur dike increases the flow shear stresses at the intake inlet by up to 50%. Overall, the main flow of the river with the highest velocity and depth, and best directed towards the water intake, occurs for the placement of the longest spur dike (i.e., LS/Br = 0.46) in front of the inlet (i.e., witness spur dike) and for a spur dike deviation angle of 135 degrees. The spur dike increases the shear stress at the intake entrance by more than five times with respect to the case of its absence. In general, the presence of a spur dike on the opposite bank and with a deviation angle in the direction of the intake inlet well directs the main flow towards the canal intake. Moreover, it reduces the possibility of sedimentation in the canal inlet by increasing the flow velocity. Therefore, the results of this study could also be useful in increasing the hydraulic efficiency of lateral intakes by reducing the sedimentation phenomena. [ABSTRACT FROM AUTHOR]

Recent advances in organ chip (or, "organ-on-a-chip") technologies and microphysiological systems (MPS) have enabled in vitro investigation of endothelial cell function in biomimetic three-dimensional environments under controlled fluid flow conditions. Many current organ chip models include a vascular compartment; however, the design and implementation of these vessel-on-a-chip components varies, with consequently varied impact on their ability to capture and reproduce hemodynamic flow and associated mechanosensitive signaling that regulates key characteristics of healthy, intact vasculature. In this review, we introduce organ chip and vessel-on-a-chip technology in the context of existing in vitro and in vivo vascular models. We then briefly discuss the importance of mechanosensitive signaling for vascular development and function, with focus on the major mechanosensitive signaling pathways involved. Next, we summarize recent advances in MPS and organ chips with an integrated vascular component, with an emphasis on comparing both the biomimicry and adaptability of the diverse approaches used for supporting and integrating intravascular flow. We review current data showing how intravascular flow and fluid shear stress impacts vessel development and function in MPS platforms and relate this to existing work in cell culture and animal models. Lastly, we highlight new insights obtained from MPS and organ chip models of mechanosensitive signaling in endothelial cells, and how this contributes to a deeper understanding of vessel growth and function in vivo. We expect this review will be of broad interest to vascular biologists, physiologists, and cardiovascular physicians as an introduction to organ chip platforms that can serve as viable model systems for investigating mechanosensitive signaling and other aspects of vascular physiology. [ABSTRACT FROM AUTHOR]

This study investigates and compares the performance of counter-rotating and co-rotating intermeshing twin-screw designs in filament extruder machines. The research sought to determine whether the counter-rotating intermeshing design with its opposite flow direction offers advantages over the co-rotating intermeshing design in terms of flow analysis and shear rates. Flow analysis was conducted to examine the velocity of the polypropylene-based biocomposite material inside the barrel. Shear rate data was obtained by evaluating the relationship between shear rate and screw speed to assess the stability and maximum shear rate of the twin-screw extruders. The results revealed that the counter-rotating intermeshing twin-screw extruders exhibited higher shear rates and more consistent pressure compared to the co-rotating intermeshing design. The superiority of the counter-rotating extruder was attributed to its opposite flow direction and distinct thread shapes, facilitating efficient material compression and improved dispersion of polymer-based biocomposite materials. The study suggested the potential for further exploration and refinement of the counter-rotating intermeshing twin-screw extruder design, particularly in producing polypropylene-based biocomposite filaments for Fused Deposition Modeling (FDM) machines. [ABSTRACT FROM AUTHOR]

The dynamics of Langmuir modes, waves (LW), and shear Langmuir vortices (SLV) are studied in kinematically complex astrophysical plasma flows. It is found that they exhibit several peculiar, velocity shear-induced, asymptotically persistent phenomena, including efficient energy exchange with the background flow and various kinds of instabilities, leading to their exponential growth and echoing solutions with persistent wave-vortex-wave conversions. There is a remarkable similarity between these phenomena and those happening with compressible acoustic modes. The relevance and possible importance of these phenomena for different types of astrophysical plasma flow patterns with kinematic complexity are discussed. In particular, we argue that these physical processes may account for the persistent appearance of plasma oscillations in the heliosphere and interstellar plasma flows. In particular, we believe that the kinematically complex motion of plasma may naturally lead to the asymptotically persistent appearance of Langmuir modes that are born, grown, fed, sustained and maintained by these flows. [ABSTRACT FROM AUTHOR]

For the slag-blowing effect of a conical laser processor in the cooling hole machining process of aeroengine hot parts, the flow field characteristics near the jet impinging on the aperture plate and its influencing factors are investigated. For the jet structure of coaxial high pressure gas impinging on a flat plate with blind holes, numerical simulation methods are used to analyze the comprehensive effects of different inlet pressures pml (0.2-1.5 MPa), jet spacing H/D, (3.6, 5.6, 7.6) and impact angle a (30°, 45°, 60°, 90°) on the gas dynamics performance near the blind holes. The results show that when H/D, is 3.6, with the increase of inlet pressure, the gas dynamics performance near the blind orifice shows a tendency of gradual improvement followed by a drastic decrease, and the better working pressure is 1 MPa; when the jet spacing H/D, reaches 5.6 and above, the aerodynamic level of the gas flow near the blind orifice can be improved by appropriately increasing the nozzle pressure, but the enhancement is limited. As the impact angle a decreases, the outflow mass flow rate in the blind hole gradually increases, and when a is 30°, it is about 11 times higher than that of the vertical jet, but the shear flow of the gas on the impact surface becomes weaker as the impact angle decreases. [ABSTRACT FROM AUTHOR]

Shish crystals are crucial to achieving high performance low-dimensional ultra-high molecular weight polyethylene (UHMWPE) products. Typically, high stretch and shear flow fields are necessary for the formation of shish crystals. In this study, UHMWPE gel films with reserved shish crystals were prepared by gel molding, the structural evolution and properties of UHMWPE films stretched at temperatures of 100, 110, 120 and 130 °C were investigated by in situ small-angle X-ray scattering (SAXS)/ultra-small-angle X-ray scattering (USAXS)/wide-angle X-ray diffraction (WAXD) measurements as well as scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) measurements. Our findings showed that the reserved shish crystals can facilitate the formation and structural evolution of shish-kebab crystals during the hot stretching. Additionally, the reserved shish crystals promote the structural evolution of UHMWPE films to a greater extent when stretched at 120 and 130 °C, compared to 100 and 110 °C, resulting in higher crystallinity, orientation, thermal properties, breaking strength and Young's modulus. Compared to UHMWPE high-entangled films with reserved shish crystals prepared by compression molding, UHMWPE low-entangled films with reserved shish crystals prepared by gel molding are more effective in inducing the formation and evolution of shish-kebab crystals during the hot stretching, resulting in increased breaking strength and Young's modulus. [ABSTRACT FROM AUTHOR]

The Cordillera Blanca and Cordillera Huayhuash contain some of the highest topography in the Andes and provide insight into tectonomagmatic processes associated with the onset of flat-slab subduction. These adjacent ranges shared a similar history of deformation and exhumation prior to the late Miocene, when synconvergent extension began in the Cordillera Blanca. Magmatism in the Cordillera Huayhuash has been inferred as coeval with magmatism in the Cordillera Blanca. Yet, extension, which has been correlated with magmatic heat flow, is limited to the Cordillera Blanca. New zircon U-Pb dates and trace and rare earth element concentrations from the Cordillera Blanca batholith and the Huayllapa pluton in the Cordillera Huayhuash and reassessment of existing zircon data help to characterize regional magmatic processes prior to the establishment of flat-slab subduction. Two compositionally distinct samples of the Huayllapa pluton yielded mean ages of 24.8 ± 0.4 Ma and 25.4 ± 0.8 Ma. In contrast, the Cordillera Blanca batholith has a protracted crystallization history postdating that of the Cordillera Huayhuash by up to 20 m.y. Miocene magmatism in the Cordillera Blanca began at 19 Ma and ended with injection of large volumes of geochemically distinct, mantle-derived magma from 10 to 5 Ma. We suggest that 6–5 Ma magmatism in the Cordillera Blanca promoted elevated heat flow and reduced shear strength, which facilitated extensional shearing along the western slopes of the range, whereas colder amagmatic crust in the Cordillera Huayhuash inhibited southward propagation of faulting. Our data demonstrate that the linkages between magmatism and elevated heat flow identified in the Cordillera Blanca are important driving processes in initiating extension in cordilleran-style orogenies. [ABSTRACT FROM AUTHOR]

Protein denaturation and aggregation resulting from the effects of interfacial stress, often enhanced by flow and shear stress, pose significant challenges in the production of therapeutic proteins and monoclonal antibodies. The influence of flow on protein stability is closely intertwined with interfacial effects. In this study, we have developed a microfluidic device capable of exposing low volume (< 320 µL) protein solutions to highly uniform shear. To disentangle the synergistic impact of flow and interfaces on protein aggregation, we fabricated two devices composed of different materials, namely poly(methyl methacrylate) (PMMA) and stainless steel. Upon application of shear, we observed formation of protein particles in the micron-size range. Notably, The number of particles generated in the steel devices was ∼ 3.5 fold lower than in the PMMA device, hinting at an interface-mediated effect. With increasing the protein concentration from 1 to 50 mg/mL we observed a saturation in the amount of aggregates, further confirming the key role of solid-liquid interfaces in inducing particle formation. Introduction of non-ionic surfactants prevented protein aggregation, even at the highest tested protein concentration and low surfactant concentrations of 0.05 mg/mL. Overall, our findings corroborate the synergistic impact of shear and interface effects on protein aggregation. The device developed in this study offers a small-scale platform for assessing the stability of antibody formulations throughout various stages of the development and manufacturing process. [ABSTRACT FROM AUTHOR]

Separation of equally sized particles distinguished solely by material properties remains still a very challenging task. Here a simple separation of differently charged, thermo‐responsive polymeric particles (for example microgels) but equal in size, via the combination of pressure‐driven microfluidic flow and precise temperature control is proposed. The separation principle relies on forcing thermo‐responsive microgels to undergo the volume phase transition during heating and therefore changing its size and correspondingly the change in drift along a pressure driven shear flow. Different thermo‐responsive particle types such as different grades of ionizable groups inside the polymer matrix have different temperature regions of volume phase transition temperature (VPTT). This enables selective control of collapsed versus swollen microgels, and accordingly, this physical principle provides a simple method for fractioning a binary mixture with at least one thermo‐responsive particle, which is achieved by elution times in the sense of particle chromatography. The concepts are visualized in experimental studies, with an intend to improve the purification strategy of the broad distribution of charged microgels into fractioning to more narrow distribution microgels distinguished solely by slight differences in net charge. [ABSTRACT FROM AUTHOR]

Cells are capable of sensing and responding to the extracellular mechanical microenvironment via the actin skeleton. In vivo, tissues are frequently subject to mechanical forces, such as the rapid and significant shear flow encountered by vascular endothelial cells. However, the investigations about the transient response of intracellular actin networks under these intense external mechanical forces, their intrinsic mechanisms, and potential implications are very limited. Here, we observe that when cells are subject to the shear flow, an actin ring structure could be rapidly assembled at the periphery of the nucleus. To gain insights into the mechanism underlying this perinuclear actin ring assembly, we develop a computational model of actin dynamics. We demonstrate that this perinuclear actin ring assembly is triggered by the depolymerization of cortical actin, Arp2/3-dependent actin filament polymerization, and myosin-mediated actin network contraction. Furthermore, we discover that the compressive stress generated by the perinuclear actin ring could lead to a reduction in the nuclear spreading area, an increase in the nuclear height, and a decrease in the nuclear volume. The present model thus explains the mechanism of the perinuclear actin ring assembly under external mechanical forces and suggests that the spontaneous contraction of this actin structure can significantly impact nuclear morphology. [ABSTRACT FROM AUTHOR]

Two types of flow mechanisms consisting of unidirectionally arrayed fibers and uncured thermoset resin exist in prepreg materials. These mechanisms are percolation flow where resin flows out of the gaps between fibers, and shear flow where resin and fibers flow together. Based on our previous study, we assumed that percolation flow is controlled by the rheology of the matrix resin, whereas shear flow is controlled by the rheology of prepreg. Based on this assumption, we experimentally evaluated the 'multiscale' solidification (solidification of matrix resin and that of prepreg) process using dynamic mechanical analysis during gelation. The solidification of matrix resin was examined by observing the development of loss angle, which provides a continuous description of the solidification process. On the other hand, the solidification of prepreg was characterized by analyzing the relationship between the shear storage modulus of prepreg and that of the matrix resin. Finally, we examined the difference in the solidification process between prepreg and matrix resin during gelation. [ABSTRACT FROM AUTHOR]

A new turbulence model has been developed for a Reynolds-averaged Navier–Stokes (RANS) simulations of buoyancy-driven flows. This study proposes a modification to the buoyancy-related term in the conventional k–ε RANS model's ε equation. Typical two-equation RANS models provide accurate predictions in homogeneous shear flow, decaying turbulence, and log-law regions, but have uncertain effectiveness for buoyancy-driven flows, particularly concerning the buoyancy-related term in the ε equation. They have produced significant errors in natural convection scenarios where the buoyancy-related term dominantly affects the modeling results, such as in the Rayleigh–Bénard (RB) convection. Conventional models are known to inaccurately predict RB convection when treated as a steady-state problem with zero mean velocity, considering only the gravity-directed coordinate as the independent variable. The analysis reveals that the conventional RANS model, along with modeling terms for buoyancy effects, provides not only inaccurate but also divergent turbulent heat fluxes in RB convection at high Rayleigh numbers. The proposed model establishes mathematical conditions that enable steady-state RANS simulations to converge to consistent scaling relations for the Nusselt number across a wide range of Rayleigh and Prandtl numbers in RB convection. This approach algebraically modifies a single term in the ε equation, so that the term vanishes in the absence of buoyancy, so the modification integrates seamlessly with the conventional k–ε RANS model. [ABSTRACT FROM AUTHOR]

We investigate the effectiveness and universality of the turbulence control strategy for wall-bounded shear flows proposed by Chagelishvili et al. The basis of this strategy is the continuous seeding of the flow viscous sub-layer with spanwise asymmetric and specially designed velocity perturbations. This seed velocity field, amplifying due to the shear flow non-normality, breaks the flow spanwise reflection symmetry, specifically leading to the generation of a secondary nonuniform spanwise mean flow, which significantly reduces the flow turbulence. For now, this strategy is realized by a weak near-wall volume forcing, which, though theoretical/hypothetical, initiates the needed seed velocity field in the flow. To confirm the practical significance of this control strategy, we evaluated its effectiveness in the plane Couette flow at various Reynolds numbers, and with the forcing locations at different distances from the wall. The universality of the discussed turbulence control strategy is shown through the direct numerical simulations. The simulations with the near-wall volume forcing having specially designed, fixed configuration and amplitude result in the reduction of turbulence kinetic energy production by 30%–40% across a wider range of Reynolds numbers, R e τ = 52 , 92 , 128 , and 270 , and the forcing various wall-normal localizations in plus units, y peak + = 0.16 , 0.28 , 0.38 , 0.81 , 2.56 , and 2.76. [ABSTRACT FROM AUTHOR]

We report the orientation dynamics of a sinusoidally driven spheroid suspended in a slow and weak/strong oscillatory shear flow without Brownian and inertial forces, derive the governing equations, find the classical Jeffery orbits, and then solve them numerically. These equations describe Jeffery's orbits for no external force and no flow oscillations. When the external forces are small, and there are no oscillations, they can be seen as perturbations of the equations that result in Jeffery's orbits. The small perturbations disturb the Jeffery orbits. We also analyze the chaotic and regular dynamics regimes in nearly quiescent, simple shear, and weak/strong and slow oscillating shear flows. We observe quantitative and qualitative differences in the particle dynamics for an oscillating shear flow compared to simple shear flow, as seen from the Poincaré sections, attractors, phase diagrams, time series, and Lyapunov exponents. The analysis indicates that the slow oscillations reduce the complexity of the dynamics of the particle compared to simple shear flow. The steady-state solutions for both prolate and oblate spheroids remain in the flow gradient plane in the case of strong oscillatory shear. At the same time, there is some disturbance from the flow gradient plane for weak oscillations due to the external force instead of inertial forces reported earlier in the literature. In addition, we propose a mechanism to improve particle separation based on shape using a combination of simple and oscillating shear flows, offering significant advantages in separating particles from a colloidal mixture that would otherwise be impossible. [ABSTRACT FROM AUTHOR]

The power of a macromolecular theory for the transport properties of a polymeric liquid increases with the number of analytical expressions for its most important material functions. In this work, we add another of these canonical function to our recent series of material function derivations for rotarance theory. By rotarance theory, we mean the explanation of the elasticity of polymeric liquids by use of (i) the diffusion equation to get the orientation distribution in Euler coordinates, and (ii) the integration in phase space using this distribution to get the target material function. In this paper, we target parallel superposition of oscillatory shear flow upon steady shear flow. We arrive at analytical expressions for both parts of the complex viscosity in parallel superposition. We find that these explain the classic experimental observations in parallel superposition: (a) the maximum in the real part of the complex viscosity, and (b) the negative values of minus its imaginary part, and (c) the independence of the steady mean shear stress from the superposed oscillation. [ABSTRACT FROM AUTHOR]

The blood protein Von Willebrand factor (VWF) is critical in facilitating arterial thrombosis. At pathologically high shear rates, the protein unfolds and binds to the arterial wall, enabling the rapid deposition of platelets from the blood. We present a novel continuum model for VWF dynamics in flow based on a modified viscoelastic fluid model that incorporates a single constitutive relation to describe the propensity of VWF to unfold as a function of the scalar shear rate. Using experimental data of VWF unfolding in pure shear flow, we fix the parameters for VWF's unfolding propensity and the maximum VWF length, so that the protein is half unfolded at a shear rate of approximately 5000 s - 1 . We then use the theoretical model to predict VWF's behaviour in two complex flows where experimental data are challenging to obtain: pure elongational flow and stenotic arterial flow. In pure elongational flow, our model predicts that VWF is 50% unfolded at approximately 2000 s - 1 , matching the established hypothesis that VWF unfolds at lower shear rates in elongational flow than in shear flow. We demonstrate the sensitivity of this elongational flow prediction to the value of maximum VWF length used in the model, which varies significantly across experimental studies, predicting that VWF can unfold between 2000 and 3200 s - 1 depending on the selected value. Finally, we examine VWF dynamics in a range of idealised arterial stenoses, predicting the relative extension of VWF in elongational flow structures in the centre of the artery compared to high shear regions near the arterial walls. [ABSTRACT FROM AUTHOR]

By considering the rotationality of shear flow, we distinguish between tube segments created by reptation before the inception of shear flow and those created during flow. Tube segments created before inception of shear flow experience both stretch and orientation, while tube segments created after inception of flow are not stretched, but are only aligned in the flow direction. Based on this idea, the Rotation Zero Stretch (RZS) model allows for a quantitative description of the start-up of shear flow and stress relaxation after step-shear strain experiments, in agreement with data of polystyrene long/short blends and corresponding polystyrene 3-arm star polymers investigated by Liu et al. (Polymer 2023, 281:126125), as well as the shear viscosity data of poly(propylene carbonate) melts reported by Yang et al. (Nihon Reoroji Gakkaishi 2022, 50:127–135). In the limit of steady-state shear flow, the RZS model converges to the Doi-Edwards IA model, which quantitatively describes the steady-state shear viscosity of linear polymer melts and long/short blends. The assumption of "non-stretching" of tube segments created during rotational flow is therefore in agreement with the available experimental evidence. Three-arm star polymers behave in a similar way as corresponding blends of long and short polymers confirming the solution effect of the short arm in asymmetric stars. The analysis of step-shear strain experiments reveals that stress relaxation is at first dominated by stretch relaxation, followed at times larger than the Rouse stretch relaxation time by relaxation of orientation as described by the damping function of the Doi-Edwards IA model. The RZS model does not require any nonlinear-viscoelastic parameter, but relies solely on the linear-viscoelastic relaxation modulus and the Rouse stretch relaxation time. [ABSTRACT FROM AUTHOR]

Guava seeds constitute 6 to 12% of the fruit weight, which contributes significantly to waste disposal in landfills annually. Guava seed oil (GSO) was extracted and evaluated for its quality attributes and utilized as substitute (10 to 50%) of refined oil in eggless and egg-based salad dressing. The yield of GSO was 10.07%, showing newtonian behaviour with significant amount of phenolic content (91.58 mg GAE/100 g), antioxidant capacity (52.91%) and total carotenoids (20.75 µg/g). FTIR spectra at 1742 1/cm confirm the presence of linoleic acid. Results showed that upto 20% level of GSO substitution in salad dressing results in superior organoleptic scores in comparison to higher levels. GSO substitution significantly (p ≤ 0.05) influenced the ash, acidity, pH, free fatty acid, peroxide vale of the salad dressing. Both salad dressings substituted with 20% GSO displayed significant (p ≤ 0.05) increases in total phenols (5.85%–8.23%) and total carotenoids (58.45%–61.12%), as result of which antioxidant activity also increased (18.17%–29.48%). Optical microscopy and particle size distribution confirmed that GSO substitution in salad dressing lowered the mean particle size and increased specific surface area, thus indicating increased oxidative stability of salad dressing. GSO substitution enhanced the viscosity, as salad dressing demonstrated pseudoplastic flow during shear rate. Storage studies (3 months) revealed GSO substituted exhibited better quality characteristics, antioxidant activity and oxidative stability in comparison to control. Results confirmed that GSO has a potential for substitution in salad dressing as functional components which enhanced the quality and storage stability of the salad dressing. [ABSTRACT FROM AUTHOR]

Modified starch, derivatives of cellulose and sodium alginate are shear thinning fluids which can be analyzed using hyperbolic tangent model as these fluids can be used as natural thickeners in the ink. Thus, the present article's intent is to study the flow conduct of hyperbolic tangent nanofluid in microchannel situated horizontally. The impact of viscous dissipation and magnetic field is recorded. The suction‐ injection is promoted at the walls of the microchannel. Two imperative slip mechanisms like Brownian motion and thermophoresis are accounted for the study. Entropy scrutiny is carried out for system effectiveness. To simplify the non‐linear equations certain non‐dimensional variables are used. The obtained mathematical formulations are solved using an efficient problem‐solving operation namely Runge–Kutta–Fehlberg 4–5th order method. The parameters attained are studied using graphical illustrations. The findings of this article comprehend that on enlarging Weissenberg number, flow field declines at the bottom wall and levitates at the top wall and the material power law parameter magnifies the velocity distribution. Entropy generated is maximum at top wall and minimum at the bottom wall for the Brownian motion parameter but the reverse manner is attained for thermophoresis parameter. Incorporating porous media to the microchannel for the flow of shear thinning fluid is useful in cell engineering, spotting particles and filtering. [ABSTRACT FROM AUTHOR]

This paper adopted numerical simulation based on the MD method to research the effect of different shear rates and wax contents on wax deposition focused on crude oil. The findings indicated that under shear flow conditions, there were primarily four steps during deposition. Diffusion was the initial stage when wax diffused onto the metal surface. In the second stage, wax adsorbed onto a metal surface aligned itself parallel to the surface via Brownian motion, generating two different kinds of deposits. Subsequently, agglomerates were formed between the adsorbed deposits and the wax as a result of molecular interactions and bridging effects. Furthermore, the second and third deposited layers gradually showed peeling off and sliding under shear force. The wax deposition process was comparable for crude oil systems with varying shear rates and wax concentrations, and the deposited layer's thickness on the metal surface was constant. The first, second, and third deposits were mainly adsorbed at 0.122 nm, 0.532 nm, and 1.004 nm away from the Fe surface, and the interaction energy between crude oil molecules and the Fe surface was mainly vdW force. The contact between Fe and wax progressively increased as the shear rate and wax content rose, promoting the wax adsorption on the metal surface and causing more of the wax to congregate in the deposited wax. The findings of the research can theoretically help a more thorough comprehension of the wax deposition. [ABSTRACT FROM AUTHOR]

An approach for creating continental‐scale, multi‐scale plasma convection maps in the nightside high‐latitude ionosphere using the spherical elementary current systems technique has been developed and evaluated. The capability to reconstruct meso‐scale flow channels improved dramatically, and the velocity errors were reduced by ∼30% compared to the spherical harmonic fitting method. Uncertainties of velocity vectors estimated by varying the model setup was also low. Convection maps for a substorm event revealed multiple flow channels in the polar cap, dominating the convection in the quiet time and early growth phase. The meso‐scale flows extended toward the nightside auroral oval and had continuous flow channels over >20° of latitude, and the flow channels dynamically merged and bifurcated. The substorm onset occurred along one of the flow channels, and the azimuthal extent of the enhanced flows coincided with the initial width of the auroral breakup. During the expansion phase, the meso‐scale flows repetitively crossed the oval poleward boundary, and some of them contributed to subauroral polarization streams enhancements. Increased flows extended duskward, along with the westward traveling surge. Then, flows near midnight weakened and evolved to the Harang flow shear. The meso‐scale flow channels had significant (∼10%–40% on average) contributions to the total plasma transport. The meso‐scale flows were highly variable on ∼10 min time scales and their individual maximum contributions reached upto 73%. These results demonstrate the capability of specifying realistic convection patterns, quantifying the contribution of meso‐scale transport, and evaluating the relationship between meso‐scale flows and localized auroral forms. Key Points: High‐resolution convection maps in the nightside high‐latitude ionosphere were created with small errors and good agreement with Defense Meteorological Satellite ProgramThe convection maps revealed a dynamic interplay of multiple flow channels during a substorm, including precursor flows to substorm onsetThe meso‐scale flows contribute to ∼10%–40% of the total flows on average. The contribution increases up to 73% during flow bursts [ABSTRACT FROM AUTHOR]

Data products relating to auroral arc systems are often sparse and distributed while ionospheric simulations generally require spatially continuous maps as boundary conditions at the topside ionosphere. Fortunately, all‐sky auroral imagery can provide information to fill in the gaps. This paper describes three methods for creating electrostatic plasma convection maps from multi‐spectral imagery combined with plasma flow data tracks from heterogeneous sources. These methods are tailored to discrete arc structures with coherent morphologies. The first method, "reconstruction," builds the electric potential map (from which the flow field is derived) out of numerous arc‐like ridges that are then optimized against the plasma flow data. This method is designed for data from localized swarms of spacecraft distributed in both latitude and longitude. The second method, "replication," uses a 1D across‐arc flow data track and replicates these data along a determined primary and secondary arc boundary while simultaneously scaling and rotating to keep the flow direction parallel to the arc and the flow shear localized at the arc boundaries. The third, "weighted replication," performs a replication on two data tracks and calculates a weighted average between them, where the weighting is based on data track proximity. This paper shows the use of these boundary conditions in driving and assessing 3D auroral ionospheric, multi‐fluid simulations. Plain Language Summary: The aurora, or northern and southern lights, are embedded within a complicated system of interacting electric fields, magnetic fields, and charged particles, the more energetic of which produce the lights themselves by exciting the neutral atmosphere. This brings about a 3D electric current system. These currents enter and exit the atmosphere along the Earth's magnetic field lines, and can only close their circuit between 80 and 150 km. This paper outlines the importance of simulating auroral arc systems in 3D and thus the need for generating continuous horizontal top‐boundary drivers for these simulations. This is difficult as the available data products are limited. This paper provides three methods for creating these boundary conditions using multi‐color, all‐sky auroral imagery in conjunction with approximately across‐arc plasma flow data tracks provided by spacecraft, sounding rockets, and/or radar measurements. Key Points: We provide three methods for developing ionospheric convection flow maps from limited data tracks in conjunction with auroral imageryMethods for generating distributed plasma flow surrounding auroral arcs can benefit from auroral arc information provided by all‐sky imageryModeling realistic auroral current closure needs drivers that vary along‐arc, across‐arc, and in altitude via electron precipitation spectra [ABSTRACT FROM AUTHOR]

This work investigates seasonal and interhemispheric variations of the afternoon auroral responses to the interplanetary magnetic field (IMF) By effects. The auroral observations are adopted from the global ultraviolet imager instrument on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite during 2002–2007. The results show that in both summer and winter solstices, the stronger afternoon auroral intensity is associated with negative IMF By (By < 0) in the northern hemisphere, and with By > 0 in the southern hemisphere. This suggests stronger contributions from the upward field‐aligned currents (FACs), which can be induced by the By‐associated north‐south oriented electric field and the By‐associated flow shear in the ionosphere. In addition, the strongest afternoon aurora occurs in summer in each hemisphere. In summer, the absolute difference between the auroral peak intensity under the two By polarities is greater and occurs earlier than in winter, which may be related to changes in FACs and conductivity from winter to summer. Differently, in equinoxes stronger auroral intensity favors By conditions associated with more frequent occurrence of southward IMF Bz, such as By < 0 and By > 0 conditions in March and in September, respectively. Therefore, in equinoxes the effects of the favorable By, which were seen in solstices, are masked. We suggest that these are caused by the Russell‐McPherron effect, which leads to more southward Bz conditions, resulting in more energy deposited and subsequent stronger aurora in polar ionosphere. These results contribute to our deeper understanding of the asymmetrical phenomena in the Earth's magnetosphere‐ionosphere induced by IMF By. Plain Language Summary: Aurora is mainly controlled by coupling among the solar wind, magnetosphere and ionosphere. The afternoon aurora can vary with the change of the north‐south components (positive‐negative Bz) and east‐west components (positive‐negative By) of interplanetary magnetic field (IMF). Generally, compared with northward Bz, stronger afternoon aurora occurs when Bz is southward. It also has By orientation preference from case studies and statistics. In this study, quantitative and statistical analysis was performed on the afternoon aurora. We confirmed that in summer and winter of the northern hemisphere, the afternoon auroral intensity is stronger for negative By than that for positive By, while the opposite trend, that is, the stronger afternoon aurora under positive By, occurs in the southern hemisphere. This hemispheric change of the afternoon auroral response to By is most probably associated with the resultant field‐aligned currents. However, the afternoon auroral intensity is stronger for negative By in both hemispheres in March and is stronger for positive By in both hemispheres in September. In each equinox, the stronger afternoon auroral intensity prefers the By orientation that is associated with greater occurrence frequency of southward Bz. Key Points: In summer and winter solstices, the afternoon auroral responses to By polarities are opposite between the northern and southern hemispheresThe absolute difference in auroral peak intensity between different By polarities is greater and occurs earlier in summer than in winterIn equinoxes, stronger afternoon auroral intensity is mostly associated with the Russell‐McPherron effect, regardless of the hemisphere [ABSTRACT FROM AUTHOR]

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Granular flows, such as rockslide debris flows, can reach high velocities and travel vast distances, but mechanisms behind this high mobility remain elusive. Using the Discrete Element Method, we implement confined shear flow with fractal particle size distribution to study the physical mechanisms inside the highly localized basal zones. Our results show that the shear strength of confined flow decreases at large fractal dimensions, and a notable transition in shear behavior also occurs with increasing fractal dimension: large particles exhibit low granular temperature and act as solid phase within a semi‐diluted suspension, and small particles enter the rolling regime. The small particles behave as interstitial fluids and reduce the shear strength of confined flow. We suggest that the reduction of shear strength stemming from the fractal particle size distribution may provide insights into the mechanisms within the highly localized basal zones, ultimately contributing to the high mobility of granular flows. Plain Language Summary: Some geophysical flows are known for their high velocities and long travel distances. Many theories have been proposed to explain the long travel distances. There remains a puzzle among them, that is, whether the particle size distribution is one of the influencing factors. In this paper, we implement a series of confined shear flows to assess the effect of fractal particle size distribution on the shear behavior of the basal zone within granular flows. Our results show that, at a large fractal dimension, the large and small particles behave like solids and the fluid in suspension, respectively. Small particles with high angular velocity reduce the shear strength of the confined shear flows. We suggest that the reduction of shear strength might be one of the reasons for the long travel distances of some geophysical flows. Key Points: We demonstrate the relevance of two invariant quantities to the fractal dimension of confined shear flowWe show the suspension‐like transition of confined shear flow at a large fractal dimensionRolling regime of small particles results in "granular lubrication" phenomenon and reduces the shear strength of confined shear flow [ABSTRACT FROM AUTHOR]

The utilization of drag-reducing polymers has long been hindered by their irritancy, corrosiveness, and toxicity across various domains. In this investigation, we explored sodium alginate, a natural drag reducer, for its efficacy in reducing drag and its resilience to shear in millimeter-scale pipelines. Initially, an experimental setup was devised to assess the drag reduction capabilities of sodium alginate at varying concentrations and flow rates using Response Surface Methodology (RSM). The relationship between drag reduction (DR), concentration (C), and flow rate (Q) was established by analyzing the experimental data. Subsequently, variance analysis was employed to validate the data accuracy, with a comparison between predicted and experimental DR values revealing an error margin within ± 20%. Analysis of cyclic shear testing of sodium alginate solution in tubes demonstrated its effectiveness as a shear flow drag reducer. Furthermore, results from laser particle size analysis indicated minimal molecular breakage of sodium alginate during cyclic shear. [ABSTRACT FROM AUTHOR]

Local scour around bridge foundations significantly impacts the stability and safety of marine structures. The development of scour holes adjacent to the pile foundations of sea-crossing bridges, influenced by tidal currents, involves multidimensional physical fields, multiscale coupling, and complex variations in marine loads. However, experimental models alone are inadequate for investigating the underlying mechanisms. Numerical simulation, a critical tool for studying local scour processes, faces the challenge of accurately modeling sediment transport, particularly under tidal flow conditions near pile foundations. To solve this challenge, this research considers the effect of reciprocating flow on sediment shear as well as its characteristic dissipation based on the immersed boundary method, introduces a reciprocating flow dissipation mechanism, and adds a momentum exchange term between the fluid and the sediment to derive a new controlling equation; a new tidal flow localized scour solver is ultimately constructed, termed TidalflowFOAM. The solver effectively simulates complex flow conditions under tidal currents, extending the modeling capabilities to more realistic three-dimensional bridge scour scenarios under combined wave and current conditions. Validation through cases reported in the literature and a series of controlled experiments, encompassing varying depths, flow velocities, and pile diameters, demonstrates the solver's proficiency in capturing post-vortex data and accurately reflecting the influence of key factors on scour depth. However, the fidelity of the simulated scour hole morphology under tidal flow conditions behind the piles requires enhancement. The proposed numerical model for tidal flow conditions has high solution accuracy and can guide practical engineering applications. [ABSTRACT FROM AUTHOR]