Explore the vast range of titles available.

This paper is concerned with predicting the progressive damage and failure of multi-layered hybrid textile composites subjected to uniaxial tensile loading, using a novel two-scale computational mechanics framework. These composites include three-dimensional woven textile composites (3DWTCs) with glass, carbon and Kevlar fibre tows. Progressive damage and failure of 3DWTCs at different length scales are captured in the present model by using a macroscale finite-element (FE) analysis at the representative unit cell (RUC) level, while a closed-form micromechanics analysis is implemented simultaneously at the subscale level using material properties of the constituents (fibre and matrix) as input. The N-layers concentric cylinder (NCYL) model (Zhang and Waas 2014 Acta Mech.225, 1391–1417; Patel et al. submitted Acta Mech.) to compute local stress, srain and displacement fields in the fibre and matrix is used at the subscale. The 2-CYL fibre–matrix concentric cylinder model is extended to fibre and (N−1) matrix layers, keeping the volume fraction constant, and hence is called the NCYL model where the matrix damage can be captured locally within each discrete layer of the matrix volume. The influence of matrix microdamage at the subscale causes progressive degradation of fibre tow stiffness and matrix stiffness at the macroscale. The global RUC stiffness matrix remains positive definite, until the strain softening response resulting from different failure modes (such as fibre tow breakage, tow splitting in the transverse direction due to matrix cracking inside tow and surrounding matrix tensile failure outside of fibre tows) are initiated. At this stage, the macroscopic post-peak softening response is modelled using the mesh objective smeared crack approach (Rots et al. 1985 HERON30, 1–48; Heinrich and Waas 2012 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, Honolulu, HI, 23–26 April 2012. AIAA 2012-1537). Manufacturing-induced geometric imperfections are included in the simulation, where the FE mesh of the unit cell is generated directly from micro-computed tomography (MCT) real data using a code Simpleware. Results from multi-scale analysis for both an idealized perfect geometry and one that includes geometric imperfections are compared with experimental results (Pankow et al. 2012 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, Honolulu, HI, 23–26 April 2012. AIAA 2012-1572). This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

The main objective of this study is to investigate the effects of Cu, Al2O3, and H2O-based nanofluids on heat transfer through annulus-shaped, two concentric cylindrical regions. The quadratic convection in the flow of hybrid nanofluids in an inclined porous annulus medium is considered. The conservation laws are obeyed in a non-linear model of the flow geometry. Applying a suitable non-dimensional transformation, we solved the resultant equation using the Runge-Kutta 4th order method with a shooting technique to obtain the solution for the velocity and temperature. The flow structure and heat transfer are influenced by quadratic resistance and mixed convection mechanisms in nonlinear Boussinesq approximation, as investigated in biomed-ical devices, nuclear reactors as well as heat exchangers. The analysis demonstrates that radiation significantly affects heat transfer by enhancing the Lorentz force, which in turn dissipates the flow rate. This behaviour aligns well with the flow patterns reported in previous studies for various physical parameters.

The recently proposed short back extrusion (SBE) method is an improved immersed-type BE method. A translational concentric cylinder rheometer is used. As the measurement position is inside the sample, the upflow in the annular space is smooth even over a short distance (5 to 15 mm). Measurement over a short distance decreases the amount of sample adhering to the plunger; this facilitates repeated measurements, as the removal of the adhering sample after each measurement is not needed. The rheometer analysis program can perform automated Newtonian, power-law, and Herschel–Bulkley flow analyses by introducing novel mathematical solutions and obtaining constitutive equations for the various flow types. Herschel–Bulkley fluids exhibit semisolid properties and thixotropic flow characteristics, specifically, stress growth or time-dependent behavior. Currently, SBE viscometry is the only available method to evaluate viscosity and yield stress simply and simultaneously and this study presented the results compared with rotational cone-plate viscometry.

Natural convective flow of a micropolar fluid is examined analytically in order to see the effect of heat and mass transfer between two concentric vertical cylinders of infinite length. The governing equations of model in non-dimensional form corresponding to the temperature, velocity and microrotational velocity, using the Boussinesq approximation and Eringen equation with suitable boundary conditions are expressed in terms of cylindrical coordinate system and then their exact solutions are obtained. The influence of the non-dimensional physical parameters such as the material and vortex viscosity parameters on the velocity, microrotational velocity is evaluated by showing on the graphs while the values of skin friction in non-dimensional form at the outer and inner surfaces of inner and outer cylinders have been presented in the tabular form.

In this study, the laminar heat transfer and nanofluid flow between two porous horizontal concentric cylinders was investigated. The problem is investigated in two different geometries and the Re=10, 25, 50, 75, 100 and volume fraction 0, 0.2%, 0.5%, 2% and 5% that related to copper nanoparticles, and porous medium porosity of 0.5 and 0.9. Compared to the first geometry, the convective coefficient in the second geometry increases by 8.3%, 7% and 5.5% at Reynolds numbers of 100, 75 and 50, respectively. Comparison of the outlet temperatures for two heat fluxes of 300 and 1200 W/m2 indicates a 2.5% temperature growth by a fourfold increase in the heat fluxes. Also, the higher Nusselt number is associated with the second geometry occurring at porosities of 0.9 and 0.5, respectively. In both geometries, the Nusselt number values at the porosity of 0.9 are higher, which is due to the increased nanofluid convection at higher porosities. The velocity of the nanofluid experiences a two-fold increase at the outlet compared to its inlet velocity in the first geometry and for both porosities. Similarly, a three-fold increase was achieved in the second geometry and for both porosities.

Soil samples with clay content ranging from 15% to 31%, were taken from three debris flow gullies in Southwest China. Three debris flow slurry samples were prepared and tested with four measuring systems of an Anton Paar Physica MCR301 rheometer, including the concentric cylinder system, the parallel-plate system, the vane geometry, and the ball measuring system. All systems were smoothwalled. Flow curves were plotted and yield stress was determined using the Herschel-Bulkley model, showing differences among the different systems. Flow curves from the concentric cylinder and parallelplate systems involved two distinct regions, the low shear and the high shear regions. Yield stresses determined by data fitting in the low shear region were significantly lower than the values from the inclined channel test which is a practical method for determining yield stress. Flow curves in the high shear region are close to those from the vane geometry and the ball measuring system. The fitted values of yield stress are comparable to the values from the inclined channel test. The differences are caused by wall-slip effects in the low shear region. Vane geometry can capture the stress overshoot phenomenon caused by the destruction of slurry structure, whereas end effects should be considered in the determination of yield stress. The ball measuring system can give reasonable results, and it is applicable for rheological testing of debris flow slurries.

The viscosity of magma exerts control on all aspects of its migration through the crust to eruption. This was particularly true for the 2021 eruption of Cumbre Vieja (La Palma), which produced exceptionally fast and fluid lava at high discharge rates. We have performed concentric cylinder experiments to determine the effective viscosities of the Cumbre Vieja magma, while accounting for its chemistry, crystallinity, and temperature. Here we show that this event produced a nepheline-normative basanite with the lowest viscosity of historical basaltic eruptions, exhibiting values of less than 10 to about 160 Pa s within eruption temperatures of ~1200 to ~1150 °C. The magma’s low viscosity was responsible for many eruptive phenomena that lead to particularly impactful events, including high-Reynolds number turbulent flow and supercritical states. Increases in viscosity due to crystallization-induced melt differentiation were subdued in this eruption, due in part to subtle degrees of silica enrichment in alkaline magma. The rheological properties of the 2021 Cumbre Vieja magma on La Palma, Canary Islands is investigated. The study indicates that this eruption was fueled by magma having among the lowest viscosities observed for mafic systems, and consequently produced lavas that were flowing in the supercritical and possibly turbulent regime.

AbstractThe current research is reported about the hydromagnetic solid–liquid flow in an annulus between two concentric circular cylinders embedded in a porous media. The impact of joule heating is also accounted for. Unlike the usually applied constant pressure gradient, the pulsatile pressure gradient is employed. The flow problem is first modeled and then tackled by Runge–Kutta–Fehlberg fourth–fifth-order (RKF45) numerical scheme along with shooting algorithm. The impacts of emerging parameters namely magnetic field parameter and porosity parameter on velocity and temperature distributions are displayed through graphs and briefly addressed.Graphical abstract

We study the stationary Navier–Stokes equations in the region between two rotating concentric cylinders. We first prove that, for a small Reynolds number, if the fluid flow is axisymmetric and if its velocity is sufficiently small in the $L^\\infty$-norm, then it is necessarily the Taylor–Couette–Poiseuille flow. If, in addition, the associated pressure is bounded or periodic in the $z$ axis, then it coincides with the well-known canonical Taylor–Couette flow. We discuss the relation between uniqueness and stability of such a flow in terms of the Taylor number in the case of narrow gap of two cylinders. The investigation in comparison with two Reynolds numbers based on inner and outer cylinder rotational velocities is also conducted. Next, we give a certain bound of the Reynolds number and the $L^\\infty$-norm of the velocity such that the fluid is, indeed, necessarily axisymmetric. As a result, it is clarified that smallness of Reynolds number of the fluid in the two rotating concentric cylinders governs both axisymmetry and the Taylor–Couette–Poiseuille flow with the exact form of the pressure.

Experiments on the inertial flow transitions of a particle–fluid suspension in the concentric cylinder (Taylor–Couette) flow with rotating inner cylinder and stationary outer cylinder are reported. The radius ratio of the apparatus was $\\unicode[STIX]{x1D702}=d_{i}/d_{o}=0.877$ , where $d_{i}$ and $d_{o}$ are the diameters of inner and outer cylinders. The ratio of the axial length to the radial gap of the annulus $\\unicode[STIX]{x1D6E4}=L/\\unicode[STIX]{x1D6FF}=20.5$ , where $\\unicode[STIX]{x1D6FF}=(d_{o}-d_{i})/2$ . The suspensions are formed of non-Brownian particles of equal density to the suspending fluid, of two sizes such that the ratio of annular gap to the mean particle diameter $d_{p}$ was either $\\unicode[STIX]{x1D6FC}=\\unicode[STIX]{x1D6FF}/d_{p}=30$ or $100$ . For the experiments with $\\unicode[STIX]{x1D6FC}=100$ , the particle volume fraction was $\\unicode[STIX]{x1D719}=0.10$ and for the experiments with $\\unicode[STIX]{x1D6FC}=30$ , $\\unicode[STIX]{x1D719}$ was varied over $0\\leqslant \\unicode[STIX]{x1D719}\\leqslant 0.30$ . The focus of the work is on determining the influence of particle loading and size on inertial flow transitions. The primary effects of the particles were a reduction of the maximum Reynolds number for the circular Couette flow (CCF) and several non-axisymmetric flow states not seen for a pure fluid with only inner cylinder rotation; here the Reynolds number is $Re=\\unicode[STIX]{x1D6FF}d_{i}\\unicode[STIX]{x1D6FA}\\unicode[STIX]{x1D70C}/2\\unicode[STIX]{x1D707}_{s}$ , where $\\unicode[STIX]{x1D6FA}$ is the rotation rate of the inner cylinder and $\\unicode[STIX]{x1D70C}$ and $\\unicode[STIX]{x1D707}_{s}$ are the density and effective viscosity of the suspension. For purposes of maintaining uniform particle distribution, the rotation rate of the inner cylinder (or $Re$ ) was decreased slowly from a state other than CCF to probe the transitions. When $Re$ was decreased, pure fluid transitions from wavy Taylor vortex flow (WTV) to Taylor vortex flow (TVF) to CCF occurred. The suspension transitions differed. For $\\unicode[STIX]{x1D6FC}=30$ and $0.05\\leqslant \\unicode[STIX]{x1D719}\\leqslant 0.15$ , with reduction of $Re$ , additional non-axisymmetric flow states, namely spiral vortex flow (SVF) and ribbons (RIB), were observed between TVF and CCF. At $\\unicode[STIX]{x1D719}=0.30$ , the flow transitions observed were only non-axisymmetric: from wavy spiral vortices (WSV) to SVF to CCF. The values of $Re$ corresponding to each flow transition were observed to reduce with increase in particle loading for $0\\leqslant \\unicode[STIX]{x1D719}\\leqslant 0.30$ , with the initial transition away from CCF, for example, occurring at $Re\\approx 120$ for the pure fluid and $Re\\approx 75$ for the $\\unicode[STIX]{x1D719}=0.30$ suspension. When the particle size was reduced to yield $\\unicode[STIX]{x1D6FC}=100$ , at $\\unicode[STIX]{x1D719}=0.10$ , only the RIB (and no SVF) was observed between TVF and CCF.