Search

In this paper, the computational examination is carried out on the heat generation, Soret and Dufour's influence on the unsteady MHD convection flow of an incompressible viscous fluid with chemical reaction. It is due to the exponentially accelerated vertical porous plate embedded in a permeable medium with ramped wall temperature together with surface concentration and also with thermal radiation impacts. The basic governing set of the equations of the fluid dynamics to the flow is converted into nondimensional form by inserting suitable nondimensional parameters and variables. In addition, the resultant equations are solved computationally with the efficient Crank–Nicolsons implicit finite difference methodology. The influences for several imperative substantial parameters for the model on the velocity, temperature and concentration for the fluids, the skin friction coefficient, Nusselt and Sherwood number for together thermal situations have been explored with the help of graphical profiles and tabular forms. It is found that, the increasing quantities of the Dufour, temperature generation and thermal radiation parameters, the fluid temperature as well as velocity enhances. Similarly, it is noted that an escalating Soret parameter causes the fluid's velocity and concentration whereas the chemical reaction parameter notifies reversal outputs. [ABSTRACT FROM AUTHOR]

Glass ionomer cements (GICs), while being beneficial source of fluoride ions, suffer from inferior mechanical properties. The mechanical properties of these cements are significantly influenced by the characteristics of the Sr-Aluminosilicate glass used in the fabrication of these cements. This study investigates the changes in glass properties when Zn2+ ions are substituted for Sr2+ ions at different concentrations of 1, 3, and 5 wt% This substitution was under taken based on the similarity of zinc ion valence electrons and the same time its greater ionic field strength with respect to strontium ions. It is demonstrated that the ability of ZnO to provide crosslinks with polyacrylic chains during cement setting stage is lower in comparison to SrO, a fact with detrimental effect on the setting time of cements. Nevertheless, our findings suggest that the effect of ZnO on the mechanical properties of cement depends on the specific composition of the glass. ZnO has the ability compete with Al 2 O 3 in network forming process, which lead to the creation of AlO x species with a higher coordination number. It was determined that parameters such as stronger bonding of Zn-O and the presence of AlO x species with higher coordination numbers played a crucial role in enhancing the compressive strength of cement from 43.8 ± 2.1 up to 90.3 ± 3.5 MPa. Moreover, the presence of zinc cations enhanced the strength of non-bridging oxygen bonds, reducing the viscous flow during the application of load through deformation. This reduction in viscous flow is considered to play a significant factor in the increase of the microhardness values of the samples from 90.3 ± 3.5 to 265 ± 1.5 HV. [ABSTRACT FROM AUTHOR]

High temperature and ultrafast heating rate, the characteristics of ultrafast high‐temperature sintering (UHS) process, make it difficult to capture the evolution of sintering behavior and explore sintering mechanism of alumina ceramics. In this study, molecular dynamic simulations are adopted to describe the sintering behaviors of equal‐sized and unequal‐sized alumina nanoparticles, particularly about shrinkage behaviors, microstructure evolution and atomic migration. Results show that high temperature and ultrafast heating rate can yield two different abnormal shrinkage behaviors, accelerating the polymerization of the nanoparticles. The main mechanism for this phenomenon is that high temperature causes the amorphization of crystal structure of nanoparticles, and ultrafast heating rates retain larger sintering driving forces at high temperatures, leading to the reduction of diffusion activation entropy and migration barriers. In particular, the appearance of viscous flow further enhances the shrinkage of the nanoparticles. In addition, surface diffusion is found to dominate the growth of sintering neck during this period. These findings are expected to deepen the understanding of ultrafast high‐temperature sintering mechanism. [ABSTRACT FROM AUTHOR]

This work provides direct experimental evidence supporting the generation of the airfoil circulation associated with a starting vortex as a viscous-flow process based on global velocity measurements near the trailing edge (TE) of a NACA0012 airfoil at the angle of attack of 6° in a low-speed wind tunnel. The evolving flow topology near the TE exhibits the apparent inviscid flow pattern in a very short initial period, the sequential formation and growth of the starting vortex as a result of near-wall viscous flow development, and the final establishment of the Kutta condition as the starting vortex travels downstream. The evolving flow field in the starting flow over the airfoil is topologically consistent. [ABSTRACT FROM AUTHOR]

We consider the governing equations for the motion of the inviscid fluids in two moving domains and an evolving surface from an energetic point of view. We employ our energetic variational approaches to derive inviscid multiphase flow systems with surface flow and tension. More precisely, we calculate the variation of the flow maps to the action integral for our model to derive both surface flow and tension. We also study the conservation and energy laws of our multiphase flow systems. The key idea of deriving the pressure of the compressible fluid on the surface is to make use of the feature of the barotropic fluid, and the key idea of deriving the pressure of the incompressible fluid on the surface is to apply a generalized Helmholtz-Weyl decomposition on a closed surface. In Appendix, we introduce one of the candidates for the viscous terms of viscous multiphase flow with a tangential compressible surface flow. [ABSTRACT FROM AUTHOR]

In this paper, we establish the existence of global-in-time solutions to the compressible micropolar fluid for a viscous heat-conducting flow with shear viscosity and general large initial data. We prove that the temperature is uniformly bounded from below and above in time and space and the global weak solution is asymptotically stable as the time tends to infinity. [ABSTRACT FROM AUTHOR]

The unsteady hydromagnetic free convection flow of rotating incompressible viscous fluids across an infinite moving plate with fractional thermal transportation is explored in the presence of heat source, Hall current and slip velocity effects. The Laplace transform method is used to convert the controlling PDEs corresponding to the temperature and velocity profiles into linear ODEs. To get the results, the classical model is modified to a fractional-order model using constitutive relations of the generalized Fourier’s law for heat flux. After making the equations dimensionless, solutions to the energy and velocity equations may be found. Graphs are plotted to check the insight of physical characteristics. Moreover, the Mittag-Leffler kernel is most affected. The memory of temperature improved by using generalized Mittag-Leffler kernel in comparison of exponential kernel. Some graphical representations of the temperature and velocity were created using the software application Mathcad. As a result, it is found that with the application of a generalized Mittag-Leffler kernel, the thermal and momentum boundary layers as well as the memory of fluid properties can be enhanced for larger values of the fractional parameter. [ABSTRACT FROM AUTHOR]

Ice streams are major regulators of sea level change. However, standard viscous flow simulations of their evolution have limited predictive power owing to incomplete understanding of involved processes. On the Greenland ice sheet, borehole fiber-optic observations revealed a brittle deformation mode that is incompatible with viscous flow, over length scales similar to the resolution of modern ice sheet models: englacial ice quake cascades that are unobservable at the surface. Nucleating near volcanism-related impurities that promote grain boundary cracking, the ice quake cascades appear as a macroscopic form of crystal-scale wild plasticity. A conservative estimate indicates that seismic cascades are likely to produce strain rates that are comparable in amplitude with those measured geodetically, providing a plausible missing link between current ice sheet models and observations. [ABSTRACT FROM AUTHOR]

Excessmolar volume, excess isentropic compressibility, deviation inviscosity, and excess Gibbs free energy for activation of viscous flow were determined for binary mixtures of 2-nitroanisole with substituted cyclohexanone (2,6-dimethylcyclohexanone (J1), 2-methylcyclohexanone (J2), and cyclohexanone (J3)) at selected compositions and temperatures ranging from 303.15 K to 313.15 K. These properties were calculated from experimentally measured densities, viscosities, and speeds of sound. The results were analysed in terms of intermolecular interactions, specifically dipole-dipole interactions leading to charge complex formation. The Jouyban-Acree model was used to correlate the experimental density and speed of sound data, with the accuracy assessed using mean relative deviation (MRD) and individual relative deviation (IRD). [ABSTRACT FROM AUTHOR]

The current research explores an unsteady Casson fluid flow through a stretching sheet with a thermal radiation effect. The influence of heat absorption/generation, viscous disputation and Joule heating is also incorporated. The governing partial differential equations of the flow problem are reduced into boundary layer regimes, which are then transformed using similarity variables into ordinary differential equations. The results are conducted graphically to present the feature of the different parameters in the problem. The physical quantities are tabulated and observed. It is examined that the velocity field is scaled back for thicker values of $ {\beta ^\ast } $ β ∗ . Furthermore, higher values of $ N{r^\ast } $ N r ∗ increase the thermal layer thickness. [ABSTRACT FROM AUTHOR]

In this article, the non-axisymmetric MHD Homann stagnation point flow over an impermeable rigid cylindrical disk is discussed. Thermal convection is also studied in the Homann flow of water by adding the multi-wall carbon nanotube/ single-wall carbon nanotube (MWCNT/SWCNT) as nanoparticles. The analysis of energy transport in nanofluids is done by adopting the dynamic and static models namely the Buongiorno and Xue models for nanofluids, respectively. Furthermore, the effect of non-linear thermal radiations and viscous dissipation on thermal energy transport is also examined. The appropriate transformations are used in order to obtain the similar differential equations. The resulting non-linear transformed coupled equations are solved by the bvp4c method in MATLAB. It is noted that for MWCNT-Water nanofluid there is significant enhancement in the heat conduction rate as compared to SWCNT-Water nanofluid. [ABSTRACT FROM AUTHOR]

A technology for numerical analysis of the local biglobal stability of laminar incompressible boundary layers over streamwise-ribbed surfaces is proposed. Within its framework, the stability is studied using the locally-parallel approximation and Floquet theory. The work of the proposed technology is demonstrated by the example of a boundary layer over a streamwise-ribbed plate of finite thickness. For the considered values of ribbing parameters, it is shown that the presence of ribbing increases the growth of disturbances compared to a plate without ribbing, thereby promoting the natural laminar–turbulent transition. [ABSTRACT FROM AUTHOR]

The baseline Launder-Spalding k - ε model cannot be integrated to the wall. This paper seeks to incorporate the entire law of the wall into the model while preserving the original k - ε framework structure. Our approach involves modifying the unclosed dissipation terms in the k and & equations specifically within the wall layer according to direct numerical simulation (DNS) data. The resulting model effectively captures the mean flow characteristics in both the buffer layer and the logarithmic layer, resulting in robust predictions of skin friction for zero-pressure-gradient (ZPG) flat-plate boundary layers and plane channels. To further validate our formulation, we apply our model to boundary layers under varying pressure gradients, channels experiencing sudden deceleration, and flow over periodic hills, with highly favorable results. Although not the focus of this study, the methodology here applies equally to the k-ω formulation and yields improved predictions of the mean flow in the viscous sublayer and buffer layer. [ABSTRACT FROM AUTHOR]

The viscous behavior and microstructure of CaF2–CaO–Al2O3–MgO slag with different B2O3 contents for electroslag remelting were investigated by employing the rotating cylinder method and molecular dynamics (MD) in conjunction with the Raman spectroscopy measurement. The results show that the viscosity of B2O3-containing ESR slag at 1823 K increased from 0.008 to 0.026 Pa s, the turning point temperature decreased from 1610 K to 1583 K, and the viscous flow activation energy of the slag decreased from 197.33 to 73.31 kJ mol−1, when the increase of B2O3 content from 2 to 7mass pct. Increasing B2O3 promotes the formation of [BO3]3− structures and [AlO3F]4− structure unit and increases the degree of polymerization of the slag. It is preliminarily speculated that increasing B2O3 destroys [AlO4]5−–[AlO4]5− structure to form [BO3]3−–[AlO4]5− structure (or [BO4]5−–[AlO4]5−). Consistent with the results of molecular dynamics calculations, the Raman spectroscopy results also show that the aluminate structure network of ESR slag is depolymerized and more borate structures units are generated as B2O3 content increases. Therefore, B2O3 can complicate the melt structure and increase the viscosity of ESR slag. [ABSTRACT FROM AUTHOR]

Viscous creep features in perennially frozen, ice-supersaturated talus/debris, usually called ‘rock glaciers’, are characteristic phenomena of mountain permafrost. On behalf of the Global Network for Permafrost (GTN-P) as part of the Global Climate Observing System (GCOS), the International Permafrost Association (IPA) has developed an initiative to systematically inventory them at global scale, and to monitor their kinematics. Corresponding consensus-based guidelines (RGIK 2023) define precise mapping procedures underpinned by facts and physics-based concepts concerning the involved conditions, material properties, processes and spatiotemporal scales. The related, more or less complex landsystem relations are treated in a strictly objective/descriptive sense as spatial upslope connections or neighbourhood situations. Application of such principles helps with avoiding misinterpretations and confusion sometimes induced with direct, intuitive, genetic attribution of landform ‘origins’. This is illustrated for a case in Nuristan, eastern Hindu Kush, Afghanistan, where in-situ measurements are lacking. Permafrost can confidently be inferred to be abundant in the region. Numerous, often spectacular, millennia old, and still actively advancing rock glaciers can be recognized and clearly distinguished from down-wasting (debris-covered) glaciers. Comparison with long-term creep in permafrost at Galena Creek (Absaroka Mountains) and Gruben (Swiss Alps), where in-situ measured facts are available, confirm that the international guidelines for related inventorying and mapping are fully adequate and should strictly be adhered to. [ABSTRACT FROM AUTHOR]

The shear-induced diffusivity of non-Brownian spheres in monodisperse suspensions undergoing viscous flow was calculated using simulations that account for particle roughness and friction as independent parameters. The diffusivity increases significantly as the friction coefficient is increased, and the effect is largest on rougher particles. Roughness reduces the transverse diffusivities relative to smoother particles for sufficiently concentrated suspensions of frictionless and low-friction particles. However, the diffusivity of roughened particles is larger than smoother ones at high values of the friction coefficient. The increase of the diffusivity with friction is associated with a significant broadening of the variance of the rotational velocities. The most prevalent observation, when correlating the microstructure to changes in diffusivity for frictionless particles, is that less diffusive systems, with larger roughness, form layers along the flow direction. These results confirm previous experimental and simulation results that roughness can decrease diffusivity at large concentrations using a more detailed model. Also, comparisons of the simulation results with previously published experimental measurements indicate that friction improves the alignment of the results with experiments. [ABSTRACT FROM AUTHOR]

Excess molar volume, excess isentropic compressibility, deviation in viscosity and excess Gibbs free energy of activation of viscous flow for binary mixtures of N,N-dimethyl benzyl amine with 2-methyl-1-butanol(P1), 2-pentanol (P2) and 2-methyl-2-butanol (P3) components selected compositions were determined from the measured values of densities (ρ), viscosities (n), and speeds of sound (u) of pure components and their mixtures from 303.15 K to 313.15 K. The results are analysed in terms of intermolecular interactions or hydrogen bonding or netero-association interactions in the binary mixtures. Finally, the Prigogine-Flory-Patterson (PFP) Theory is applied to identify the most predominant molecular interaction. Using the Jouyban-Acree model, results are discussed in terms of mean relative deviation (MRDs) and individual relative deviation (IRD) between calculated and experimental densities, speeds of sound and viscosities as an accuracy criterion. [ABSTRACT FROM AUTHOR]

Excess molar volume, excess isentropic compressibility, deviation in viscosity and excess Gibbs free energy of activation of viscous flow for binary mixtures of dibenzyl amine with 1-pentanol (P1), 2-pentanol (P2) and 2-methyl-2-butanol (P3) components selected compositions were determined from the measured values of densities (ρ), viscosities (η), and speeds of sound (u) of pure components and their mixtures from 303.15 K to 313.15 K. The results are analysed in terms of complex formation through proton donor – acceptor interactions or hydrogen bonding or hetero molecular association interactions in the binary mixtures. Finally, the Prigogine–Flory–Patterson (PFP) Theory is applied to identify the most predominant molecular interaction. Jouyban-Acree model, results are discussed in terms of mean relative deviation (MRDs) and individual relative deviation (IRD) between calculated and experimental densities, speeds of sound and viscosities as an accuracy criterion. [ABSTRACT FROM AUTHOR]

Smoothed particle hydrodynamics (SPH), a fully Lagrangian particle method, has been widely used in various applications, such as the simulation of incompressible flow with a free surface. For highly viscous flow, which typically appears in polymer processing, a fully implicit scheme, which implicitly treats both the predictor and corrector procedures of the projection method in the SPH framework, is efficient and numerically stable. This study proposes a simple and efficient fully implicit scheme that improves predictive accuracy for highly viscous flow. The proposed scheme utilizes a recently developed scheme for highly viscous flow that performs the pressure calculation before the viscosity diffusion calculation, unlike the conventional projection method. This study further improves the viscosity diffusion calculation by considering a viscous diffusion term that is usually ignored due to the continuity equation. Including this term enables us to correctly perform calculations for non‐Newtonian flows. The increase in the computational cost that results from the inclusion of the term is alleviated by introducing a two‐step method for calculating the viscous diffusion terms. The developed scheme is applied to injection molding of a polymer melt between two parallel plates. The results show that the proposed two‐step implicit scheme reproduces the fountain flow behavior near the advancing front. In addition, a three‐dimensional molding simulation of a plate with a hole shows a significant improvement in the prediction of the filling pattern in the mold. [ABSTRACT FROM AUTHOR]

This paper considers the Keller-Segel model coupled to stochastic Navier-Stokes equations (KS-SNS, for short), which describes the dynamics of oxygen and bacteria densities evolving within a stochastically forced 2D incompressible viscous flow. Our main goal is to investigate the existence and uniqueness of global solutions (strong in the probabilistic sense and weak in the PDE sense) to the KS-SNS system. A novel approximate KS-SNS system with proper regularization and cut-off operators in H s (R 2) is introduced, and the existence of approximate solution is proved by some a priori uniform bounds and a careful analysis on the approximation scheme. Under appropriate assumptions, two types of stochastic entropy-energy inequalities that seem to be new in their forms are derived, which together with the Prohorov theorem and Jakubowski-Skorokhod theorem enables us to show that the sequence of approximate solutions converges to a global martingale weak solution. In addition, when χ (⋅) ≡ const. > 0 , we prove that the solution is pathwise unique, and hence by the Yamada-Wantanabe theorem that the KS-SNS system admits a unique global pathwise weak solution. [ABSTRACT FROM AUTHOR]

Hydrodynamic cloaks, a type of metamaterials possessing zero-drag properties, show fascinating potential for aerospace, marine engineering, and high-speed transportation. However, achieving zero drag with hydrodynamic cloaks in viscous flows is challenged by the complexity of the Navier–Stokes equations. This study designs spherical hydrodynamic cloaks based on machine learning, which allow objects to move in a viscous fluid without disturbing the flow fields. These cloaks merely require the supply of uniform external forces, unaided by metamaterials, allowing objects wrapped in the cloak to move unimpeded through viscous flow fields. Numerical simulations show that these cloaks provide significant drag reduction efficiency (up to 96.26%) and enhance flow stability by eliminating lift fluctuations. These findings provide new insights into flow control and expand the applicability of hydrodynamic metamaterials to high Reynolds number environments, with promising applications in multiphysics fields such as thermal-hydrodynamic coupling and acoustic-hydrodynamic coupling. [ABSTRACT FROM AUTHOR]

A uniform, steady, viscous, laminar magnetohydrodynamic (MHD) flow over a fixed partially contaminated liquid drop placed in a porous region is considered. An interfacial slip is assumed on its surface. The drag force with cap angle is obtained analytically. The special case results are consistent with available results in literature. The flow pattern graphs are studied. It is observed that the coefficient of drag values rise in tandem with increases in the slip parameter, viscosity ratio, Hartmann number, and porosity parameter. Compared to viscous flow over a contaminated liquid drop and MHD flow over a contaminated liquid drop without being placed in a porous region, the drag of MHD flow over a contaminated liquid drop planted in a porous region is greater. It can be seen from the flow pattern comparison graph that areas without porous media have free flow, but areas with porous media have enhanced internal circulations and external flow that is extended toward objects. [ABSTRACT FROM AUTHOR]

The hydroelastic effects of an elastic plate and its piezoelectric characteristics under wave forces are examined in this study. The hydroelastic analysis models fluid motion and hydrodynamic pressure using viscous flow theory, solved through a combination of the Reynolds–averaged Navier–Stokes equations, the continuity equation, and the shear stress transport turbulence model. The finite element method is employed both to solve the hydroelastic motion of the plate and to calculate the static electric field. Unlike previous studies where the piezoelectric plate was fully submerged in water, this work places the plate on the wave surface. This approach serves two purposes: to increase the static pressure difference between the upper surface and lower surface of the plate and to amplify the wave-induced forces. A detailed analysis of strain energy, plate deformation, and electric voltage distribution is also presented. [ABSTRACT FROM AUTHOR]

Alternative energy sources require the search for innovative materials with promising functionalities. Systems with unusual chemical properties represent an insufficiently explored domain, concealing unexpected features. Using diffraction and Raman spectroscopy over a wide temperature range, supported by first‐principles simulations, a rare phenomenon is unveiled: phase‐dependent chemical interactions between binary components in the NaCl–Ga2S3 system. In this unique occurrence, previously intact binary crystalline species transform upon melting into mixed liquid structural isomers, forming bonds with new partners. The chemical combinatorics appears to be fully reversible for stable crystals and liquids. Despite this, rapidly frozen glasses out of thermodynamic equilibrium remain in a metastable isomeric state, offering remarkable properties, particularly a high room‐temperature Na+ conductivity, comparable to the best sodium halide superionic conductors and therefore encouraging for sodium solid‐state batteries and energy applications. A rigidity paradigm is responsible for the observed phenomenon, as the extremely constrained Ga2S3 crystal lattice does not survive viscous flow, breaking up at a short‐range level. The removal of rigidity constraints and dense packing leads to a significant increase in empty space, which is the origin of high sodium diffusivity. Broadly, the rigidity‐driven structural isomerism opens up an inspiring path to the discovery of atypical materials. [ABSTRACT FROM AUTHOR]

Densities (ρ), speeds of sound (u), and viscosities (η) of binary mixtures of N,N-dimethyl benzyl amine (DMBA) with 1,2-dichlorobenzene (1,2-DCB), 1,3-dichlorobenzene (1,3-DCB), and 1,2,4-trichlorobenzene (1,2,4-TCB) were measured at temperatures ranging from 303.15 K to 313.15 K for selected compositions. Excess molar volume (VE), excess isentropic compressibility (κsE), viscosity deviation (Δη), and excess Gibbs free energy for activation of viscous flow (ΔG*E) were subsequently determined from the experimental data. The obtained results were analysed to elucidate the nature of intermolecular interactions, specifically focusing on attractive forces, steric hindrance or hetero-association within the mixtures. The Prigogine–Flory–Patterson (PFP) theory was employed to identify the dominant type of molecular interaction. The Jouyban–Acree model was applied to calculate densities, speeds of sound, and viscosities. The accuracy of the model was evaluated using mean relative deviations (MRDs) and individual relative deviations (IRDs) between the calculated and experimental values. [ABSTRACT FROM AUTHOR]

A thorough investigation into binary mixtures of propargyl alcohol and various carboxylic acids (ethanoic, propanoic and butanoic) was conducted. Measurements of density (ρ), speed of sound (u) and viscosity (η) were meticulously performed across the entire range of mole fractions at temperatures (303.15 K−313.15 K) and atmospheric pressure (0.1 MPa). These data were used to calculate key thermodynamic and transport properties, including excess molar volume, excess isentropic compressibility, deviation in viscosity and excess Gibbs free energy of activation for viscous flow. The partial molar properties and infinite dilution molar partial properties were also determined for each binary system. Trends and behaviours were interpreted within the framework of intermolecular interactions, focusing on complex formation and specific chemical forces. The PFP theory and Jouyban–Acree model were critically applied, with confidence in the findings supported by FTIR studies. [ABSTRACT FROM AUTHOR]

Herein, the influence of P2O5 on the break temperature and phase composition of slag from the double slag converter steelmaking process is investigated comprehensively. The composition and micromorphology of crystallized phase are analyzed by X‐Ray diffractometer and scanning electron microscope equipped with energy dispersive spectrometer. The results reveal that the break temperature of slag increases owing to an increase of P2O5 content. When the P2O5 content is 2%, the break temperature is 1198 °C, and it increases to 1209 °C for the slag with 4% P2O5. With the increase of P2O5 content from 2% to 8%, the activation energy for viscous flow shows an upward trend. The crystallized phase at the same temperature with different P2O5 contents remains nearly unchanged, but the diffraction peak intensity is different. When the P2O5 content remains constant, a decrease in temperature results in significant changes in the micromorphology of crystallized phases. The present results improve the knowledge about the P‐rich slag, and are also significant in optimizing the double slag converter steelmaking process. [ABSTRACT FROM AUTHOR]

Bionic flapping hydrofoil motion is increasingly used in bionic underwater robots. However, many scholars have focused their attention on the navigation problem in deep-water environments, thus ignoring changes in the hydrodynamics of hydrofoils under the action of the near-free-surface effect. This paper studies and explores the hydrofoil motion in near-free surfaces through the RANS viscous flow numerical simulation method, combined with overset mesh and adaptive mesh technology. Three different forms of motion are studied respectively, including a stationary fixed, a single-degree-of-freedom pitch and a two-degree-of-freedom heaving-pitching coupled hydrofoil. The effects of varying the immersion depth d on the lift and thrust generated were analyzed. Results indicate noticeable differences in the free surface action among different motion forms. When the water depth is less than one chord length C, the lift and thrust of the three motion forms decreased rapidly decrease. When d/C=1-1.5, the static fixed hydrofoil lift and thrust gradually approach the deep-water state. When d/C>2, the pitching motion of a single degree of freedom also tends to be stable. The two-degree-of-freedom motion is d/C>3. This finding shows that the effect of the near-free surface is closely related to the vertical motion. The greater the vertical motion is, the more severe the effect. [ABSTRACT FROM AUTHOR]

The particle size-dependent processes of structural relaxation and crystal growth in amorphous nifedipine were studied by means of non-isothermal differential scanning calorimetry (DSC) and Raman microscopy. The enthalpy relaxation was described in terms of the Tool–Narayanaswamy–Moynihan model, with the relaxation motions exhibiting the activation energy of 279 kJ·mol−1 for the temperature shift, but with a significantly higher value of ~500 kJ·mol−1 being obtained for the rapid transition from the glassy to the undercooled liquid state (the latter is in agreement with the activation energy of the viscous flow). This may suggest different types of relaxation kinetics manifesting during slow and rapid heating, with only a certain portion of the relaxation motions occurring that are dependent on the parameters of a given temperature range and time frame. The DSC-recorded crystallization was found to be complex, consisting of four sub-processes: primary crystal growth of αp and βp polymorphs, enantiotropic βp → βp′ transformation, and βp/βp′ → αp recrystallization. Overall, nifedipine was found to be prone to the rapid glass-crystal growth that occurs below the glass transition temperature; a tendency of low-temperature degradation of the amorphous phase markedly increased with decreasing particle size (the main reason being the increased number of surface and bulk micro-cracks and mechanically induced defects). The activation energies of the DSC-monitored crystallization processes varied in the 100–125 kJ·mol−1 range, which is in agreement with the microscopically measured activation energies of crystal growth. Considering the potential correlations between the structural relaxation and crystal growth processes interpreted within the Transition Zone Theory, a certain threshold in the complexity and magnitude of the cooperating regions (as determined from the structural relaxation) may exist, which can lead to a slow-down of the crystal growth if exceeded. [ABSTRACT FROM AUTHOR]

In this study, an innovative guiding pin-fin array optimization has been developed through three-dimensional numerical simulations to enhance the cooling efficiency of gas turbine blade trailing edge. The guiding pin-fin array is optimized using the Kriging surrogate model and Genetic Algorithm (GA), aiming to significantly improve the heat transfer rates and uniformity within the wedge-shaped channel. The design parameter chosen for optimization is the deflection angle of each guiding pin fin, and the optimization process is conducted in two rounds. The first-round optimization yields a first-optimized guiding pin-fin array, which exhibits superior overall heat transfer performance and reasonable pressure loss compared to conventional circular, oblong, and parallel pin-fin arrays. For the first-optimized guiding pin-fin (1st-OGP) channel at the Reynolds number of Re = 50,000, the total Nusselt number and pressure loss are 44.1% higher and 9.9% lower than those of the baseline circular pin-fin array (CP), respectively. An experimental validation using the transient liquid crystal (TLC) thermography method is carried out and proves the effectiveness of the optimization process. However, it is noted that the first-optimized guiding pin-fin exhibits even lower heat transfer at a low Reynolds number of Re = 10,000, particularly in the channel middle region, which is mainly due to the incapable turning flow control in the root region of the wedged channel. To address this issue and further improve the heat transfer performance at low Reynolds numbers, a second-round optimization is performed by specifically adjusting the deflection angle of the selected guiding pin fins near the root region of the wedged channel. This secondary optimization demonstrates significant heat transfer improvements over the whole studied Reynolds number range with a reasonably reduced consumption of computational resources. The total Nusselt number and pressure loss are 69.3% higher and 11.9% lower than those of the baseline circular pin-fin array, respectively, at Re = 50,000. The optimization process proposed in this paper produces a high-performance cooling structure design with elaborate guiding pin-fin arrangements in the wedge-shaped channel, which indicates high heat transfer enhancement and relatively lower pressure loss in the wedged channel for the turbine blade trailing edge. [ABSTRACT FROM AUTHOR]

A two‐dimensional (2D) axisymmetric numerical model, based on the finite element method, for glass containers forming processes is presented. Glass forming processes involve coupled thermomechanical phenomena in which heat transfer and viscous flow are dependent, as glass viscosity is highly dependent on temperature. During the overall process glass changes from a molten state to a solid state. Therefore, adequate cooling conditions must be set appropriately. From the numerical point of view, the modeling must be robust so as to adjust to the different sequenced stages. Remeshing techniques requiring adequate data transfer, as well as, different thermal and mechanical contact conditions between glass and molds must be taken into account. Also, effective treatment of the incompressible conditions associated with glass flow must be dealt with. The aim is to set the better process parameters so that the final containers have the required geometrical shape and thickness distribution. A numerical model was conducted addressing all these issues and a thickness distribution comparison with real industrial products was performed. [ABSTRACT FROM AUTHOR]

This research examines the appearance of a two‐dimensional steady flow movement of a viscous, incompressible fluid undergoing chemical reactions along an infinitely long vertical porous plate. The flow is influenced by a transverse magnetic field, with the plate experiencing a uniform suction velocity. The research novelty lies in inspecting the impacts of ohmic dissipation and diffusion‐thermo effects while maintaining constant heat and mass flux and considering heat and mass transfer in the presence of thermal radiation. Using perturbation techniques, the foremost calculations are solved, and the results are presented both graphically and in tables. The analysis shows that higher values of the diffusion‐thermo parameter upsurge fluid velocity and temperature, whereas the presence of the transverse magnetic field decreases fluid velocity and temperature. [ABSTRACT FROM AUTHOR]

Field and remote sensing studies suggest that ice mélange influences glacier–fjord systems by exerting stresses on glacier termini and releasing large amounts of freshwater into fjords. The broader impacts of ice mélange over long timescales are unknown, in part due to a lack of suitable ice mélange flow models. Previous efforts have included modifying existing viscous ice shelf models, despite the fact that ice mélange is fundamentally a granular material, and running computationally expensive discrete element simulations. Here, we draw on laboratory studies of granular materials, which exhibit viscous flow when stresses greatly exceed the yield point, plug flow when the stresses approach the yield point, and exhibit stress transfer via force chains. By implementing the nonlocal granular fluidity rheology into a depth- and width-integrated stress balance equation, we produce a numerical model of ice mélange flow that is consistent with our understanding of well-packed granular materials and that is suitable for long-timescale simulations. For parallel-sided fjords, the model exhibits two possible steady-state solutions. When there is no calving of icebergs or melting of previously calved icebergs, the ice mélange is pushed down-fjord by the advancing glacier terminus, the velocity is constant along the length of the fjord, and the thickness profile is exponential. When calving and melting are included and treated as constants, the ice mélange evolves into another steady state in which its location is fixed relative to the fjord walls, the thickness profile is relatively steep, and the flow is extensional. For the latter case, the model predicts that the steady-state ice mélange buttressing force depends on the surface and basal melt rates through an inverse power-law relationship, decays roughly exponentially with both fjord width and gradient in fjord width, and increases with the iceberg calving flux. The buttressing force appears to increase with calving flux (i.e., glacier thickness) more rapidly than the force required to prevent the capsizing of full-glacier-thickness icebergs, suggesting that glaciers with high calving fluxes may be more strongly influenced by ice mélange than those with small fluxes. [ABSTRACT FROM AUTHOR]

A two-dimensional periodic Stokes flow of viscous incompressible fluid in a rectangular cavity with constant velocities applied to the top and bottom walls is considered. The study of advection regimes is reduced to the sequential solving of two problems. To solve the first problem, the analytical method of superposition, which allows one to obtain any desired accuracy of the velocity field, is used. To solve the second problem, which is associated with obtaining the trajectories of individual fluid particles, numerical calculations of the Cauchy problem were performed. An analysis of the boundary conditions accuracy was performed based on the control of local integration. The advection of the selected volume of fluid in the rectangular cavity under the periodic motion of walls for a finite period time based on piecewise spline cubic interpolation is modeled. The obtained numerical results agree with well-known experimental data. [ABSTRACT FROM AUTHOR]

In this paper, it was considered a numerical simulation of the water surface movement during the partial collapse of the destruction of a dam with complex terrain. The numerical simulations took into account debris after a partial collapse of the dam, which imitates debris and moves downstream with the water flow. Carrying out these calculations brings the results closer to the real scenario. The mathematical model was based on the Navier–Stokes equations and uses the turbulent large eddy method (LES) model describing the flow of an incompressible viscous fluid. To describe the movement of a two-phase fluid, the volume of fluid (VOF) methods for the phase were used, and the Discrete Phase Model (DPM) and Macroscopic Particle Model (MPM) were used to describe the movement of particles. For the numerical solution of this system of equations, the Pressure Implicit Split Operator (PISO) numerical algorithm was chosen. The results show that the model is accurate and capable of handling very complex interactions such as particle transport or hydrodynamic actions on structures if the appropriate scales are reproduced. Also in this work, a three-dimensional (3D) model of the flow of a dam break on uneven terrain was considered and combined problems were performed that are closer to real conditions. For combined problems, flood zones and flood times were determined, knowledge of which will help evacuate people from dangerous areas. The accuracy of the 3D model and the selected numerical algorithm were verified using two natural measurements. [ABSTRACT FROM AUTHOR]

On the analysis of literary sources and working processes of a positive displacement pump we established that a hydrolic diode in positive displacement pumps improves their reliability and their most efficient application is in pumps in which the process of reverse flow into the working cavity into the discharge line is insignificant in time, for example, in spur rotary pumps. We established on comparing the results of a numerical experiment on the flow of a viscous incompressible fluid in a hydrolic diode, that the k-w model most accurately describes the fluid flow in a diaphragm hydrolic diode both quantitatively and qualitatively. The performed parametric analysis of the influence of the main parameters on the fluid flow in the hydrolic diode and the diodicity proved that the distance between the hydrolic diode plates should be within 35–40 mm; the angle of inclination of the plates to the body of the hydrolic diode should be 20°−30°; the number of pairs of plates should be within 7–9 pcs. [ABSTRACT FROM AUTHOR]

This study investigated the viscosity and sulfide capacity of electric smelting furnace (ESF) slag (CaO-SiO 2 -6wt.%MgO-10 wt%Al 2 O 3 -FeO) with a basicity of 0.8 through cylinder rotating method and gas-slag equilibrium experiments. Additionally, the high-temperature structure of the slag was analyzed using FTIR and Raman spectroscopy. The results showed that as the FeO content increased from 1 wt% to 9 wt%, the viscosity of the ESF slag gradually decreased, with a more pronounced reduction observed when the FeO content exceeded 5 wt%. The increase in FeO content led to a reduction in the initial liquidus temperature, resulting in the formation of a greater amount of liquid phase at lower temperatures. Furthermore, FeO released O2− ions at high temperatures, which depolymerized the silicate network structure, thereby reducing the viscous flow resistance. These dual effects of FeO contributed to the decrease in slag viscosity. In addition, the sulfide capacity of the slag increased with rising FeO content, and the activity order of sulfides in the slag was FeS > CaS > MgS. This was because Ca2+ ions were largely consumed for charge compensation within the silicate structure in the low-basicity slag. Based on these findings, during the ESF furnace smelting process, the desulfurization step should preferably be conducted at the front end of the reduction process. [ABSTRACT FROM AUTHOR]

Lithiation-free mold fluxes with excellent performances are urgently needed to be developed, due to the desire for Li 2 CO 3 (Li 2 O) from the lithium battery industry. So, in this study, the melting, viscosity and structure of the CaO-SiO 2 based flux melt, with the aim to replace Li 2 O by Na 2 O and B 2 O 3 , were investigated. Results show that the melting temperature decreased from 1258.1-1651.9 K to 1245.3–1632.5 K, and the viscosity at 1573 K decreased from 0.310 to 0.098 Pa s, when the ratio of Li 2 O/(Na 2 O + B 2 O 3) decreased from 0.38 to 0.00. Meanwhile, the break temperature reduced from 1475.3 to 1451.4 K, and the activation energy of viscous flow also decreased from 181.44 to 55.39 kJ/mol, with the decease of Li 2 O/(Na 2 O + B 2 O 3) ratio. Melt structure analyses indicate that the simpler structural units, such as Q0(Si), Q1(Si), [AlO 4 ]5- tetrahedral and B-O- in [BO 3 ] increased, while the more complex structural units, like Q2(Si), Q3(Si), bending vibration of Si-O-Al and boron ring in borate reduced, when Li 2 O was replaced by Na 2 O and B 2 O 3. These changes suggest that the DOP of the flux melt was reduced and the melt structure was simplified during the lithiation-free process. [ABSTRACT FROM AUTHOR]

In this paper, the global existence of weak solutions is justified for the three-dimensional (3D) compressible magneto-micropolar fluids with discontinuous initial data which are of small energy but possibly large oscillations with constant state as far field which could be vacuum. Our result is a generalization of Huang et al. Commun. Pure Appl. Math. 65, 549–585, (2012) from viscous isentropic flows to the viscous compressible magneto-micropolar fluids. [ABSTRACT FROM AUTHOR]

The primary subject of this article is the study of the viscous flow of nanofluids consisting of copper-methanol and water in the presence of a three-dimensional stretched sheet, which is subjected to magnetohydrodynamic effects (3D-MHD-NF) by employing artificial recurrent neural networks that are optimized using a Bayesian regularization technique (ARNN-BR). The viscosity effect is recognized to be dependent on temperature, with methanol and water being used as the base fluid. The presented model is employed in the manipulation and creation of surfaces within the field of nanotechnology. Its applications include stretching, shrinking, wrapping, and painting devices. The Adams method was employed to generate a dataset for the 3D-MHD-NF model for four scenarios by varying the Hartmann number (H), volume fraction of nanoparticle (φ ), and viscosity parameter (α). The ARNN-BR technique employed a random selection of data 70% for training, 20% for testing, and 10% for validity. It has been found that boundary layer becomes thinner as the volume percentage of nanoparticle increases. Additionally, it is observed that augmentation in the viscosity parameter results in a proportional rise in temperature. Moreover, it is observed that increment in the variables H, φ, and α have an impact on the velocity boundary thickness in both the x- and y-directions. The newly introduced ARNN-BR technique's dependability, stability, and convergence were assessed using a fitness measure based on mean squares errors, histogram drawings, regression, input-error cross-correlation, and autocorrelation analysis for each scenario of the 3D-MHD-NF model. [ABSTRACT FROM AUTHOR]

This study presents a mathematical model of incompressible viscous fluid flow in an elastic tube with thin walls, emphasizing the function of injection or suction through the tube wall to simulate fluid exchange. Under the assumption of a minimal slope parameter, the nonlinear governing equations are linearized up to second order using a perturbation approach. For the velocity component, wall shear stress, and mean pressure drop, analytical solutions are acquired. The pressure differential equation can be solved numerically by applying Gill's fourth-order method. The tube geometry, Womersley number, suction/injection, and elasticity characteristics all have an impact on variations in wall shear stress, based on the results. Furthermore, the mean pressure drop decreases consistently with increasing elasticity value, irrespective of tube geometry. [ABSTRACT FROM AUTHOR]

Vanadium-bearing titanomagnetite is a valuable mineral resource that as a raw material for blast-furnace ironmaking can lead to an increase in the mass fraction of TiO2 in slag. However, TiO2 will be excessively reduced in the process of ironmaking and produce the TiC and Ti(C,N) suspended in the slag, deteriorating the metallurgical properties of the slag. In this study, the effect of TiC and Ti(C,N) on the viscous flow characteristics of CaO-SiO2-8.25%MgO-15%Al2O3-30%TiO2 slags was investigated by the rotating cylinder method. The research results showed that in the five-element slag system with a ∑TiO2 content of 30% and the ratio of w(CaO)/w(SiO2) = 1.20, the viscosity of slag increases with the increase of TiC and Ti(C,N) mass fraction over a range of 1 to 7%, and the viscosities of system containing TiC were greater than that containing Ti(C,N). The melting temperature of slags was determined by calculating the second-order derivative of viscosity with temperature. It was found that the melting temperature of slag increases with the increase of TiC and Ti(C,N) content, and the melting temperature of slag containing a smaller particle size of TiC is more high. The viscous-flow activation energy Eη of slags increases with the increase of TiC and Ti(C,N) content, which has a concomitant variation corresponding with the results of the effect of TiC and Ti(C,N) on viscosity. The revised Einstein-Roscoe equation has high prediction accuracy for the viscosity of solid-liquid slag systems containing corresponding solid particles. [ABSTRACT FROM AUTHOR]

With the development of renewable energy and the utilization of marine resources, large-scale offshore floating photovoltaics have gradually attracted widespread attention. In order to develop offshore floating photovoltaics and promote sustainable development, it has become necessary to explore the hydrodynamic characteristics of floating photovoltaic units and floating arrays. In this work, based on the viscous flow theory, the Computational Fluid Dynamics (CFD) and the discrete element method (DEM) methods are used to analyze the hydrodynamics of the floating body unit of offshore floating photovoltaics. The influencing factors include mooring length, mooring radius, and floating unit length. In addition, the hydrodynamic performance of the floating body unit and the floating body array under different wave heights and periods is also discussed to explore the influence of environmental loads on the floating body unit and the floating body array. The results indicate that the mooring tension exhibits an opposite trend with the surge and heave motions when the mooring line length and radius are varied. The motion is found to be more pronounced when the floating body unit length is 0.4 times the wavelength. The heave motion of the floating body unit exhibits a strong linear relationship with wave height, increasing by 0.01 m for every 0.015 m increase in wave height. The motion of the floating body units on both sides connected to the mooring lines decreases as the array length increases. [ABSTRACT FROM AUTHOR]

In natural environments, fish almost always swim in groups. Investigating the coupled mechanism of biomimetic fish exhibiting autonomous swimming capabilities advances our understanding of fish schooling phenomena and simultaneously aids in refining the structural and formation configurations of underwater robotic vehicles. This work innovatively develops an algorithm based on the Direct-Forcing Immersed Boundary Method (DF-IBM) and implements it in an efficient, modular software program written in C++. The program accelerates the calculation process by using a multigrid method. Validation against a benchmark case of flow around a cylinder, with comparison to data from the existing literature, verifies the program's precision with discrepancies of less than 3.6%. Based on this algorithm, the paper analyzes the incompressible viscous flow during the movement of parallel-aligned biomimetic fish. It uncovers the interaction between the fish's motion and the surrounding flow field and also reveals the hydrodynamic mechanisms of the group motion of the parallel-aligned biomimetic fish. The flow field under varying spacing and phases between the parallel-aligned biomimetic fish proves that the interaction between the flow fields induced by the two fish bodies becomes increasingly significant when decreasing the lateral spacing from 1.4 L to 0.6 L . Notably, an initial lateral convergence of the fish bodies is observed, followed by a sideways swimming pattern at a particular pitch angle, accompanied by a decrement in their forward swimming velocity as they approach each other. Additionally, this study compares flow field alterations in parallel-aligned biomimetic fish with identical lateral spacing but opposing flapping phases. The findings indicate that, irrespective of the phase, the fish exhibit an initial convergence followed by a sideways motion at a specific pitch angle. However, due to disparities in the tail's flow field, a larger pitch angle is generated when the fish swim in unison. All the findings above will provide a solid theoretical foundation for the design and optimization of underwater robotic vehicles. [ABSTRACT FROM AUTHOR]

A mathematical model for tropical cyclones' winds, taking into account various crucial considerations makes the analysis of Cecil and Majdalani (2022) more realistic. Drawing inspiration from their work which obtains the axial velocity from the stream function, we incorporate the notion of viscous flow within cyclone dynamics, a modification that brings present model more closely aligned with the real-world conditions. Our key considerations include the absence of axial velocity at the ground, zero radial velocity at the cyclone's centre, and outside the eye-wall. In order to derive pressure, we integrate axial pressure gradient with respect to axial coordinate; and as a consequence we get an arbitrary function of radial coordinate which we eliminate by using Vatistas (1991) velocity at the ground to meet the cyclostrophic balance. Azimuthal velocity and pressure are derived for viscous flows. The formulations hold good for arbitrary Reynolds number. The analysis demonstrates a positive relationship between Reynolds number and azimuthal velocity within cyclone's eye. This trend persists within the inner eye-wall, characterized by a gradually diminishing velocity. An inflexion point is identified midway the eye and the eye-wall, where maximum azimuthal velocities are observed. The central focus of our study revolves around the influence of eye size on various velocity components and pressure. Our findings reveal that a larger eye size correlates with the development of more intense tropical storms. However, this increase in storm intensity reaches a peak and subsequently experiences a rapid decline within the rain band region compared to smaller eye cyclones. Regardless of the eye's size, our analysis consistently demonstrates that atmospheric pressure increases as one moves away from the eye. • Mathematical model for the viscous flow of tropical cyclone. • Dependence of eye sizes on the intensity of the tropical cyclones. • The behavior of velocity components on the Reynolds number. [ABSTRACT FROM AUTHOR]

AbstractThis paper presents an analytical solution for the steady flow of viscous, incompressible conducting fluid through a porous slit between two permeable parallel plates. A uniform magnetic field is applied normal to the plates. Brinkman equation is used as governing equation of motion. Beaver and Joseph’s slip condition is used to characterize the flow boundary conditions. Exact solution for axial and transverse velocity are given and stream lines of the flow for different values of flow parameters are sketched. The impact of magnetic field on flow is investigated. The obtained results are useful to understand the mechanism of blood flow through human tissues. [ABSTRACT FROM AUTHOR]