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We investigate the elastic wave propagation in various hyperelastic materials which are subjected to simple-shear deformation. Two compressible types of three conventional hyperelastic models are considered. We found pure elastic wave modes that can be obtained in compressible neo-Hookean materials constructed by adding a bulk strain energy term to the incompressible strain energy function. Meanwhile, for the compressible hyperelastic models which are reformulated into deviatoric and hydrostatic parts, only quasi modes can propagate, with abnormal ray directions that can be observed for longitudinal waves. Moreover, the influences of material constants, material compressibility and external deformations on the elastic wave propagation and refraction in these hyperelastic models are systematically studied. Numerical simulations are carried out to validate the theoretical results. This investigation may open a promising route for the realization of next generation metamaterials and novel wave manipulation devices. [ABSTRACT FROM AUTHOR]

Shell has developed a novel mono-diameter well concept for oil and gas wells as opposed to the traditional telescopic well design. A Mono- diameter well contains multiple casing sections with the same internal diameter. This is achieved by expansion of the casing sections concerned using an expansion cone. Since the well is drilled in stages and casings are inserted to support the open hole, an overlap section between two consecutive (expandable) casings exists which has to be expanded. When the cone enters the overlap section, the expansion force increases dramatically due to the expansion of two casings, cured cement and formation layers. When the cone finalizes the expansion of the overlap section it pops out, the expansion force vanishes and the cone accelerates upwards and it generates an empty volume to be filled by the well fluid (mud). As a result of this, fluid starts to flow through the drill pipe, around the cone and the fluid volume below the cone starts to decompress. This induces a surge pressure wave traveling upwards and a swab pressure wave in the expanded casing traveling downwards. If the pressure difference between outside and inside of the expanded casing exceeds the collapse rating of the casing, the casing will collapse which leads to the loss of the concerned well section. Repair of such a failure costs time and money, therefore this swab pressure must be well predicted to enable the installation process to be designed such that this collapse can be avoided. A model of fully coupled fluid-structure interaction between cone and the well fluid is built for calculating the swab pressure propagating downward and surge pressure propagating upward resulted from transient process occurring after cone pops out. This model has shown an effective tool for predicting the swabbing pressure in field deployments performed lately in Gulf of Mexico and according to its output the suitable cone is selected in order to avoid the casing collapse. [ABSTRACT FROM AUTHOR]

In this paper we consider the one-dimensional Navier-Stokes system for a heat-conducting, compressible reacting mixture which describes the dynamic combustion of fluids of mixed kinds on unbounded domains. This model has been discussed on bounded domains by Chen (SIAM J Math Anal 23:609-634, 1992) and Chen-Hoff-Trivisa (Arch Ration Mech Anal 166:321-358, 2003), among others, in which the reaction rate function is a discontinuous function obeying the Arrhenius' law of thermodynamics. We prove the global existence of weak solutions to this model on one-dimensional unbounded domains with large initial data in $$H^1$$ . Moreover, the large-time behaviour of the weak solution is identified. In particular, the uniform-in-time bounds for the temperature and specific volume have been established via energy estimates. For this purpose we utilise techniques developed by Kazhikhov-Shelukhin (cf. Kazhikhov in Siber Math J 23:44-49, 1982; Solonnikov and Kazhikhov in Annu Rev Fluid Mech 13:79-95, 1981) and refined by Jiang (Commun Math Phys 200:181-193, 1999, Proc R Soc Edinb Sect A 132:627-638, 2002), as well as a crucial estimate in the recent work by Li-Liang (Arch Ration Mech Anal 220:1195-1208, 2016). Several new estimates are also established, in order to treat the unbounded domain and the reacting terms. [ABSTRACT FROM AUTHOR]

A higher order mixed finite element method is presented for compressible transversely isotropic finite hyperelasticity. The independent variables of the three-field formulation are; displacement, fibre tension and fibre stretch. The formulation admits the description of a fully coupled stress response which evolves from an almost isotropic one into a hyper-anisotropic simply nearly inextensible response with increasing fibre tension, as for example observed in soft tissue biomechanics. Standard displacement approximation of order p in H 1 ( Ω ) is used while the auxiliary variables are approximated element wise by square integrable functions of order p − 1 in L 2 ( Ω ) . For finite extensibility the auxiliary variables are statically condensed out yielding a pure displacement based method. It is implemented in an hp -adaptive finite element code. A matching residual based error estimation capability is added and exercised. Numerical evidence indicating stability of approximation is supplied resolving a boundary layer caused by almost inextensible fibres. Coupled and uncoupled stress responses are compared. A generalised compressible transversely isotropic Holzapfel–Gasser–Ogden model is developed for the formulation that intentionally avoids the volumetric–isochoric split. Solutions obtained with the mixed method compare favourably to the corresponding ones obtained with pure displacement formulation. The latter fails in certain strongly anisotropic cases. [ABSTRACT FROM AUTHOR]

A block-centered finite difference method is introduced to solve an initial and boundary value problem for a nonlinear parabolic equation to model the slightly compressible flow in porous media, in which the velocity-pressure relation is described by Darcy-Forchheimer's Law. The method can be thought as the lowest order Raviart-Thomas mixed element method with proper quadrature formulation. By using the method the velocity and pressure can be approximated simultaneously. We established the second-order error estimates for pressure and velocity in proper discrete norms on non-uniform rectangular grid. No time-step restriction is needed for the error estimates. The numerical experiments using the scheme show that the convergence rates of the method are in agreement with the theoretical analysis. [ABSTRACT FROM AUTHOR]

A Hu–Washizu type 3-field virtual work principle for strongly transversely isotropic compressible finite hyperelasticity is developed, implemented and verified. The independent variables are: the stretch, its energy conjugate uniaxial tension and the displacement. The formulation is based on a new decomposition of the deformation gradient into a simply stretchless part and a lateral contraction-free uniaxial extension. In the fully constrained limit the formulation provides the constraint manifold setting of hyperelasticity with the simple internal kinematic constraint of inextensibility. The finite element formulation is implemented in an hp -adaptive code providing the proper flexible environment for finite elements with variable order and mixed interpolation. A study using a semi-inverse analytical solution corroborates the convergence characteristics for h -refinements and p -enrichments of the 3-field implementation. The case of isostatic loading of a circular cylinder reinforced with a single family of fibres, and the pressurisation of a saccular aneurysm-like configuration with circumferential fibre reinforcement are used for verification and illustration. A posteriori residual discretisation error estimation is used for making mesh refinements in the latter case. Typical applications are found in soft tissue biomechanics. [ABSTRACT FROM AUTHOR]

We discuss changes to a target design that improved the quality and consistency of data obtained through a novel experimental platform that enables the study of hydrodynamic instabilities in a compressible regime. The experiment uses a laser to drive steady, supersonic shockwave over well-characterized initial perturbations. Early experiments were adversely affected by inadequate experimental timescales and, potentially, an unintended secondary shockwave. These issues were addressed by extending the 4x10 13 W/cm 2 laser pulse from 19 ns to 28 ns, and increasing the ablator thickness from 185 µm to 500 µm. We present data demonstrating the performance of the platform. [ABSTRACT FROM AUTHOR]

We investigate the turbulent multiphase flow inside a nine-hole common rail Diesel injector during a full injection cycle of ISO 4113 diesel fuel into air by implicit large-eddy simulation (LES). The simulation includes a prescribed needle movement obtained from a one-dimensional multi-domain simulation. The injector geometry is represented by a conservative cut-element-based immersed boundary method with subcell resolution, which has been developed for the application in the context of cavitating liquid flows. We employ a barotropic two-phase two-fluid model, where all components (i.e. air, liquid diesel, gaseous diesel) are represented by a homogenous mixture approach. The cavitation model is based on a thermodynamic equilibrium assumption. Compressibility of all phases enables full resolution of collapse-induced pressure wave dynamics. The analysis of the turbulent flow field reveals that the opening and closing phase are dominated by small-scale turbulence, while in the main injection phase large vortical structures are formed in the needle volume and reach into the nozzle holes. Violent collapse events of cavitation structures are detected during the closing phase in the nozzle holes and after closing in the sac hole region. A comparison with LES results with a fixed injector needle at different lift positions shows a good agreement for large needle lifts, while the needle movement has significant effects on important flow features at low needle lifts. [ABSTRACT FROM AUTHOR]

A numerical investigation of the combined effects of heating and flow orientation on the forced convective flow of air past a square cylinder is carried out. In order to account for the effects of large-scale heating like thermal straining of the fluid particles, variations in thermo-physical and transport properties, a fully compressible flow model is utilized. The numerical simulations are carried out using a new flux-based particle velocity upwind scheme (PVU-M+). The computations are carried out in the parametric space of free stream Reynolds number (Re) in the range [60, 140], free stream orientation (α) in the range [0, 45°] and the Over-heat ratio, ε = (T W − T ∞ )/T ∞ in the range [0, 1] where T W and T ∞ are the uniform cylinder and free stream temperatures. At all parameter combinations the flow is found to be unsteady with vortex-shedding except for ( Re = 60, α = 0, ε = 0.8, 1.0) and ( Re = 60, α = 15, ε = 1.0) where vortex-shedding is suppressed resulting in a steady flow. By comparing the data for the global parameters like Strouhal number, mean drag coefficient and mean Nusselt number, with that obtained from a constant property incompressible flow model (Boussinesq type model), a quantification of “large-scale” heating scenario is carried out. Utilizing a novel mathematical procedure, it is shown that the data obtained for the global parameters at different Re and ε can be transformed into appropriate scaling parameters that yield an optimal collapse of the data at different ( Re , ε ) combinations for a fixed free-stream orientation. [ABSTRACT FROM AUTHOR]

Primitive Equations (PE) are an important model which is widely used in the geophysical research and the mathematical analysis. In the previous results, people derive PE from the Navier–Stokes or the Euler system by an asymptotic analysis or a numerical approximation. Here, we give a rigorous mathematical derivation of inviscid compressible Primitive Equations from the Euler system in a periodic channel, utilizing the relative entropy inequality. [ABSTRACT FROM AUTHOR]

Scalar mixing and evaporation processes are analyzed in a compressible two-phase homogeneous and isotropic turbulence configuration. To this end, the fully compressible Navier–Stokes equations are solved using a pressure-based method and a mass-conservative interface capturing method (CLSVOF). Temperature and vapor mass fraction transport equations are coupled with the momentum equation via the evaporation rate: i.e. heat and mass transfer has an effect on the flow dynamic through the generation of a Stefan flow at the interface. In this formalism, a pressure equation is developed to include the acoustic, thermal dilatation and compressibility effects. Moreover, the method can consider several gas structures in the same domain, each with independent temperature, density, and thermodynamic pressure. The latter is important to simulate atomization, where interaction among the liquid structures (such as breakup or coalescence) can generate multiple gas inclusions. This work is one of the first to describe with high fidelity the vaporization and turbulent mixing occurring in dense two-phase flows. A statistical analysis of the vapor mass fraction field is performed. The obtained results reveal the influence of the non-homogeneous scalar source at the interface, which depend directly on the local interface temperature, on the PDF shape. Under these conditions, the vapor mass fraction PDF deviates from the Gaussian and beta PDF shapes, frequently used for turbulent combustion modeling. Furthermore, access to the local surface averaged vapor mass fraction and evaporation rate at the interface allows a statistical analysis of these variables. Results show a large dispersion of both quantities, especially at the early times of the simulations, which contradict the usual assumption of a constant vapor mass fraction (or vaporization rate) at the interface used in the literature in standard vaporization models. Finally, the influence of the mean interface curvature on the evaporation rate is quantified and discussed. Large evaporation rate are present when the interface is convex (positive mean curvature). On the contrary, local saturation zones are present near concave interface (negative mean curvature), reducing the evaporation rate magnitude. • A DNS study of scalar mixing in evaporating turbulent two-phase flows is presented. • A direct resolution of heat and mass transfer is performed. • The scalar mixing is studied for two evaporation regimes by use of PDFs. • Results show the impact of the convex and concave curvature on the evaporation rate. [ABSTRACT FROM AUTHOR]

The formation of compressible porous sponge electrodes is appealing to overcome diffusion limitations in porous electrodes for applications including electrochemical energy storage, electrochemical water desalination, and electrocatalysis. Previous work has employed wet chemical synthesis to deliver conductive materials into porous polymer sponge supports, but these approaches struggle to produce functional electrodes due to (1) poor electrical connectivity of the conductive network and (2) mechanical rigidity of the foam after coating. In this work we employ oxidative molecular layer deposition (oMLD) via sequential gas-phase exposures of 3,4 ethylenedioxythiophene (EDOT) and molybdenum pentachloride (MoCl 5 ) oxidant to imbibe polyurethane (PU) sponges with electrically-conductive and redox-active poly(3,4 ethylenedioxythiophene) (PEDOT) coatings. We analyze the oMLD deposition on compressive PU sponges and modify the reaction conditions to obtain mechanically compressible and electrically conductive sponge electrodes. We specifically identify the importance MoCl 5 dose time to enhance the conductivity of the sponges and the importance of EDOT purge time to preserve the mechanical properties of the sponges. Controlling these variables produces an electrically conductive PEDOT network within the sponge support with reduced impact on the sponge's mechanical properties, offering advantages over wet-chemical synthesis approaches. The compressible, conductive sponges we generate have the potential to be used as compressible electrodes for water desalination, energy storage, and electrocatalysis., (© 2023 IOP Publishing Ltd.)

This work focuses on the performance and validation of some recent Reynolds stress models in compressible homogeneous shear flow. The SSG model developed by Speziale Sarkar and Gatski has shown a great success in simulating a variety of incompressible complex turbulent flows. On the other hand, it has not predicted correctly the compressible turbulence at high speed shear flow. Thus, a compressibility correction for this model is the major aim of this study. In the present work, two recent compressible models for the pressure strain-strain correlation have been used to modify the linear term of the SSG model. These modifications make the linear term dependent on a turbulent Mach number. In addition, compressibility correction model for the slow part of the pressure strain is proposed. The obtained results are compared with DNS results of Sarkar. The results show that important parameters characteristic of compressibility in homogeneous turbulent shear flow are well captured by the extended SSG model.

Several studies of compressible flows show that the pressure-strain is the main indicator of the structural compressibility effects. Undoubtedly, this term controls the change in the Reynolds stress anisotropy. Regarding the model of Adumitroiae et al., the slow part of the pressure strain correlation like the Rotta model uses the standard coefficient C1. The model predictions do not show large differences when compressibility increases. Correction of this coefficient using the turbulent Mach number is proposed. The two forms model of Adumitroiae et al. (with and without correction of 1 C ) are considered to study compressible mixing layers . The obtained results show that the predictions of the proposed compressibility correction model agree with the experiment results of Goebel and Dutton.

In this paper, the regularity of weak solutions to the three-dimensional compressible isentropic self-gravitating viscous fluids is considered in periodic domain. Inspired by the idea of Desjardins (1997) [3,4], we get the higher integrability of density ρ , and we remove the additional assumption of ρ ∈ L ∞ ( 0 , T ; L q 0 ) in the work of Choe and Jin (2003). Finally, we prove the supremum of the density is finite and the infimum of the density is positive in the domain ( 0 , T ) × T 3 for a positive time T . Moreover, Moser type iteration scheme is used to obtain the L ∞ norm estimate of the velocity. [ABSTRACT FROM AUTHOR]

This paper is devoted to the second-order closure for compressible turbulent flows with special attention paid to modeling the pressure-strain correlation appearing in the Reynolds stress equation. This term appears as the main one responsible for the changes of the turbulence structures that arise from structural compressibility effects. The structure of the gradient Mach number is similar to that of turbulence, therefore this parameter may be appropriate to study the changes in turbulence structures that arise from structural compressibility effects. Thus, the incompressible model (LRR) of the pressure-strain correlation and its corrected form by using the turbulent Mach number, fail to correctly evaluate the compressibility effects at high shear flow. An extension of the widely used incompressible model (LRR) on compressible homogeneous shear flow is the major aim of the present work. From this extension the standard coefficients Ci became a function of the compressibility parameters (the turbulent Mach number and the gradient Mach number). Application of the model on compressible homogeneous shear flow by considering various initial conditions shows reasonable agreement with the DNS results of Sarkar. The ability of the models to predict the equilibrium states for the flow in cases A1 and A4 from DNS results of Sarkar is examined, the results appear to be very encouraging. Thus, both parameters Mt and Mg should be used to model significant structural compressibility effects at high-speed shear flow. [ABSTRACT FROM AUTHOR]

This paper is concerned with the initial-boundary value problem for the three-dimensional compressible liquid crystal flows. The system consists of the Navier-Stokes equations describing the evolution of a compressible viscous fluid coupled with various kinematic transport equations for the heat flow of harmonic maps into S2. Assuming the initial density has vacuum and the initial data satisfies a natural compatibility condition, the existence and uniqueness is established for the local strong solution with large initial data and also for the global strong solution with initial data being close to an equilibrium state. The existence result is proved via the local well-posedness and uniform estimates for a proper linearized system with convective terms. [ABSTRACT FROM AUTHOR]

Previous studies of compressible flows carried out in the past few years have shown that the pressure-strain is the main indicator of the structural compressibility effects. Undoubtedly, these terms plays a key role toward strongly changing magnitude of the turbulent Reynolds stress anisotropy. On the other hand, the incompressible models of the pressure-strain correlation have not correctly predicted compressible turbulence at high speed shear flow. Consequently, a correction of these models is needed for precise prediction of compressibility effects. In the present work, a compressibility correction of the widely used incompressible Launder Reece and Rodi model making their standard coefficients dependent on the turbulent and convective Mach numbers is proposed. The ability of the model to predict the developed mixing layers in different cases from experiments of Goebel and Dutton is examined. The predicted results with the proposed model are compared with direct numerical simulation and experimental data and those obtained by the compressible model of Adumitroiae et al. and the original Launder Reece and Rodi model. The results show that the essential compressibility effects on mixing layers are well captured by the proposed model. [ABSTRACT FROM AUTHOR]

Aerodynamic slider bearings are currently used in various types of turbomachinery. Many such systems perform at increasingly faster speeds and may operate in the supersonic regime. Although there is extensive research on compressible lubrication extrapolated to high-speeds, very little of it addresses the potential supersonic nature of the flow. It is well known in compressible flow that many of the tendencies of subsonic flow actually reverse themselves as the singularity at Mach one is traversed. Thus, examination of this high-speed regime may yield some unanticipated results. The behavior of a thin film of air in the supersonic regime is studied in the two-dimensional flow case with rigid sliding suifaces. The one-dimensional bearing studied has a dual profile consisting of an inlet region converging wedge of constant slope and an exit region of constant gap. Two approaches are compared: the solution of a modified Reynolds equation, and the solution to a version of Navier-Stokes equations adapted to thin films. The results show that the modified Reynolds equation approach, which is useful to describe the behavior of lubricating fluids at high subsonic speeds may be inadequate in the supersonic regime. The present studies show the absence of shock and expansion wave phenomena for cases in which the film thickness ratio does not exceed 0.01. [ABSTRACT FROM AUTHOR]

The dual-medium approach is convenient for simulating flows within two interacting continua such as fractured reservoirs, because it greatly simplifies the apparent complexity of the flow problem while offering a conceptual representation of flows within and between the two continua that helps the understanding of flow responses. Considerable work has been achieved during the last decades to model the coupling term of such models, that is, matrix-fracture transfers. Whereas pseudo-steady-state transfers taking place at late times can be fairly well predicted, the simulation of transient, i.e. early-time, transfers still encounters difficulties due to intrinsically complex transfer mechanisms that the resolution of diffusion equations entails. Those difficulties are emphasized for tight porous media where transient flow behaviour persists over a durable period of time, for compressible fluids that increase inaccuracy of linear approximations of transfers, and also because of the multi-directionality of transfers. Starting from analytical solutions of diffusivity equations, the present paper proposes a methodology to account for transient effects and for non-linearities in matrix-fracture transfer formulas of dual-porosity simulators in order that they can predict the production of unconventional low-permeability hydrocarbon reservoirs. Validation of these formulas for the production of very tight fractured media is shown at the matrix block scale and at the scale of a stimulated reservoir volume. [ABSTRACT FROM AUTHOR]

We formulated a pressure equation for bubbles performing nonlinear radial oscillations under ultrasonic high pressure amplitudes. The proposed equation corrects the gas pressure at the gas–liquid interface on inertial bubbles. This pressure formulation, expressed in terms of gas-Mach number, accounts for dampening due to gas compressibility during the violent collapse of cavitation bubbles and during subsequent rebounds. We refer to this as inhomogeneous pressure, where the gas pressure at the gas–liquid interface can differ to the pressure at the centre of the bubble, in contrast to homogenous pressure formulations that consider that pressure inside the bubble is spatially uniform from the wall to the centre. The pressure correction was applied to two bubble dynamic models: the incompressible Rayleigh–Plesset equation and the compressible Keller and Miksis equation. This improved the predictions of the nonlinear radial motion of the bubble vs time obtained with both models. Those simulations were also compared with other bubble dynamics models that account for liquid and gas compressibility effects. It was found that our corrected models are in closer agreement with experimental data than alternative models. It was concluded that the Rayleigh–Plesset family of equations improve accuracy by using our proposed pressure correction. [ABSTRACT FROM AUTHOR]

This study is devoted to application of the fourth-order compact MacCormack scheme to spatial differencing of the conservative form of two-dimensional and non-hydrostatic equation of a dry atmosphere. To advance the solution in time a four-stage Runge–Kutta method is used. To perform the simulations, two test cases including evolution of a warm bubble and a cold bubble in a neutral atmosphere with open and rigid boundaries are employed. In addition, the second-order MacCormack and the standard fourth-order compact MacCormack schemes are used to perform the simulations. Qualitative and quantitative assessment of the numerical results for different test cases exhibit the superiority of the fourth-order compact MacCormack scheme on the second-order method. [ABSTRACT FROM AUTHOR]

Problems of interest in hydrogeology and hydrocarbon resources involve complex heterogeneous geological formations. Such domains are most accurately represented in reservoir simulations by unstructured computational grids. Finite element methods accurately describe flow on unstructured meshes with complex geometries, and their flexible formulation allows implementation on different grid types. In this work, we consider for the first time the challenging problem of fully compositional three-phase flow in 3D unstructured grids, discretized by any combination of tetrahedra, prisms, and hexahedra. We employ a mass conserving mixed hybrid finite element (MHFE) method to solve for the pressure and flux fields. The transport equations are approximated with a higher-order vertex-based discontinuous Galerkin (DG) discretization. We show that this approach outperforms a face-based implementation of the same polynomial order. These methods are well suited for heterogeneous and fractured reservoirs, because they provide globally continuous pressure and flux fields, while allowing for sharp discontinuities in compositions and saturations. The higher-order accuracy improves the modeling of strongly non-linear flow, such as gravitational and viscous fingering. We review the literature on unstructured reservoir simulation models, and present many examples that consider gravity depletion, water flooding, and gas injection in oil saturated reservoirs. We study convergence rates, mesh sensitivity, and demonstrate the wide applicability of our chosen finite element methods for challenging multiphase flow problems in geometrically complex subsurface media. [ABSTRACT FROM AUTHOR]

We consider the Cauchy problem for the 3D Euler system with damping coupled to radiation through two singular limits. Assuming suitable smallness hypotheses for the data, we prove that each of these two problems admits a unique smooth solution. [ABSTRACT FROM AUTHOR]

Analyses of invariants of the velocity gradient tensor (VGT) at the turbulent–nonturbulent interface of temporal plane mixing layers reveal a new type of joint pdf. When compressibility effects are small, fluid packets from the surrounding nonturbulent freestream enter the turbulent region in sheet-like zones; the VGT has one positive (compression) and two negative (expansion) eigenvalues. When compressibility effects are significant, in some parts of the turbulent–nonturbulent interface two of the eigenvalues are positive and one is negative. The implied local flow is that of streamtubes surrounded by vortex arcs (partial rings). The new topology occurs less frequently than the sheet-like regions. [ABSTRACT FROM AUTHOR]

This paper presents a characteristic-based flux partitioning for the semi-implicit time integration of atmospheric flows. Nonhydrostatic models require the solution of the compressible Eu- ler equations. The acoustic time scale is significantly faster than the advective scale, yet it is typically not relevant to atmospheric and weather phenomena. The acoustic and advective components of the hyperbolic flux are separated in the characteristic space. High-order, conservative additive Runge{ Kutta methods are applied to the partitioned equations so that the acoustic component is integrated in time implicitly with an unconditionally stable method, while the advective component is inte- grated explicitly. The time step of the overall algorithm is thus determined by the advective scale. Benchmark flow problems are used to demonstrate the accuracy, stability, and convergence of the proposed algorithm. The computational cost of the partitioned semi-implicit approach is compared with that of explicit time integration. [ABSTRACT FROM AUTHOR]

The reactive fluid dynamics of transonic flows in nozzles is an important area of experimental and theoretical research. This paper consists of two parts. In the first part an algorithm for the solution of th e Euler Equations in conservative form is discussed which simplifies a generalization of Murman Scheme [1] that is presented in Reference [2]. ChattoCs work is discussed and calculations for flows with shocks are presented. In th e second part, transonic flows with friction, heat addition and dissipation is considered. Specific a ttention is given to detonations with one-step Arrhenius chemistry. A part of this study is to understand the interaction between friction and transonic flow with combustion. The details of the numerical algorithms will be presented along with validation examples from the literature. [ABSTRACT FROM AUTHOR]

A new two-phase incompressible–compressible Smoothed Particle Hydrodynamics (SPH) method has been developed where the interface is discontinuous in density. This is applied to water–air problems with a large density difference. The incompressible phase requires surface pressure from the compressible phase and the compressible phase requires surface velocity from the incompressible phase. Compressible SPH is used for the air phase (with the isothermal stiffened ideal gas equation of state for low Mach numbers) and divergence-free (projection based) incompressible SPH is used for the water phase, with the addition of Fickian shifting to produce sufficiently homogeneous particle distributions to enable stable, accurate, converged solutions without noise in the pressure field. Shifting is a purely numerical particle regularisation device. The interface remains a true material discontinuity at a high density ratio with continuous pressure and velocity at the interface. This approach with the physics of compressibility and incompressibility represented is novel within SPH and is validated against semi-analytical results for a two-phase elongating and oscillating water drop, analytical results for low amplitude inviscid standing waves, the Kelvin–Helmholtz instability, and a dam break problem with high interface distortion and impact on a vertical wall where experimental and other numerical results are available. [ABSTRACT FROM AUTHOR]

The one-dimensional turbulence (ODT) methodology is extended to include an efficient compressible implementation and a model for capturing shock-induced turbulence is presented. Lignell et al. recently introduced a Lagrangian ODT implementation using an adaptive mesh. As the code operates in the incompressible regime (apart from constant-pressure dilatation) it cannot handle compressibility effects and their interactions with turbulence and chemistry. The necessary algorithmic changes to include compressibility effects are highlighted and our model for capturing shock–turbulence interaction is presented. To validate our compressible solver, we compare results for the Sod shock tube problem against a finite volume Riemann solver. To validate our model for shock–turbulence interaction, we present comparisons for a non-reactive and a reactive case. First, results of a shock traveling from light (air) to heavy (SF 6 ) with reshock have been simulated to match mixing width growth data of experiments and turbulent kinetic energy results from LES. Then, for one-step chemistry calibrated to represent an acetylene/air mixture we simulate the interaction of a shock wave with an expanding flame front, and compare results with 2D simulation (2D-sim) data for flame brush formation and ensuing deflagration-to-detonation transitions (DDT). Results for the Sod shock tube comparison show that the shock speed and profile are captured accurately. Results for the non-reactive shock–reshock problem show that interface growth at all simulated Mach numbers is captured accurately and that the turbulent kinetic energy agrees in order of magnitude with LES data. The reactive shock tube results show that the flame brush thickness compares well to 2D-sim data and that the approximate location and timing of the DDT can be captured. The known sensitivity of DDT characteristics to details of individual flow realizations, seen also in ODT, implies that model agreement can be quantified only by comparing flow ensembles, which are presently unavailable other than in an ODT run-to-run sensitivity study that is reported herein. [ABSTRACT FROM AUTHOR]

This paper discusses the implementation of an explicit density-based solver, that utilises the central-upwind schemes for the simulation of cavitating bubble dynamic flows. It is highlighted that, in conjunction with the Monotonic Upstream-Centered Scheme for Conservation Laws (MUSCL) scheme they are of second order in spatial accuracy; essentially they are high-order extensions of the Lax–Friedrichs method and are linked to the Harten Lax and van Leer (HLL) solver family. Basic comparison with the predicted wave pattern of the central-upwind schemes is performed with the exact solution of the Riemann problem, for an equation of state used in cavitating flows, showing excellent agreement. Next, the solver is used to predict a fundamental bubble dynamics case, the Rayleigh collapse, in which results are in accordance to theory. Then several different bubble configurations were tested. The methodology is able to handle the large pressure and density ratios appearing in cavitating flows, giving similar predictions in the evolution of the bubble shape, as the reference. [ABSTRACT FROM AUTHOR]

[Display omitted] • Elastic brushite/polyethyleneimine/nanofibrillated cellulose aerogel was developed. • The coupling of brushite and polyethyleneimine enhanced adsorption property. • PNFCA/BRU-0.2 exhibited high selectivity for Cu(II) with 332.66 mg/g. • The continuous flow purification of copper-containing wastewater was realized. • PNFCA/BRU-0.2 could block the toxicity of heavy metals to crops. To achieve efficient removal of copper(II) from heavy metal wastewater, designing an eco-friendly and low-cost adsorbent is highly desirable. Here, a novel air- and underwater shape-memory cellulose aerogel was reported via coupling brushite and polyethyleneimine (PEI)-modified nanofibrillated cellulose (NFC) for selectively adsorbing Cu(II) ions. The adsorption kinetic and isotherm studies were consistent with pseudo-second-order model and Langmuir model, indicating the removal of Cu(II) was a monolayer chemisorption process. Benefiting from the open three-dimensional (3D) framework structure and abundant exposed active sites, such compressible aerogel exhibited excellent adsorption capacity of 332.66 mg/g for Cu(II). In addition, the developed aerogel could be conveniently used as a continuous flow filter for successive purification of industrial wastewater, where the up-to-standard treatment volume was about 5.6 L. The Cu(II)-loaded aerogel could be regenerated after being eluted by 0.1 M EDTA-2Na, and its structure, shapeability and selective adsorption properties were hardly affected even after 8 consecutive cycles. Mechanistic analysis confirmed that the surface complexation, ion exchange and chemical deposition were the main driving forces for the superior adsorption performance. Finally, PNFCA/BRU could inhibit the contamination of crops by heavy metals, which was a great safeguard for wheat growth. [ABSTRACT FROM AUTHOR]

The new kind of ferroelectret electroactive polymers for flexible film sensors represent an attractive opportunity for self-powered wearable devices, which could offer sustainable and convenient health care services for people without the problem of energy supply. However, due to the mechanical heterogeneity, obtaining ferroelectrets with both a high longitudinal and transverse piezoelectric response is still a great challenge, which limits its multifunctional sensing application, especially in body motion tracking. Herein, we develop an air-filled parallel tunnel ferroelectret-based self-powered body motion detectors. Ascribed to the high mechanical compression and tensile properties of the specially designed parallel tunnel void structure and excellent charge storage stability of the fluorinated polyethylene propylene (FEP) electret film, these laminated films exhibit many fascinating merits, including ultrahigh longitudinal piezoelectric response (piezoelectric coefficient of 6200 pC/N, pressure sensitivity of 1950 pC/kPa), wide pressure detection range (0.03–62 kPa), remarkable transverse piezoelectric response (tensile sensitivity of 1600 pC/mm), long-term durability (1,08,0000 cycles), and superior friction force detection capability. This is the first work, to our knowledge, that ever use one kind of piezoelectric mechanism in a single ferroelectret-based sensor to achieve longitudinal stress, transverse stress, and tangential friction force sensing. Furthermore, on the basis of such sensors and machine learning algorithms, we designed an intelligent gesture recognition system for future human-machine interaction applications. Looking forward, our material design methodologies offer an approach to the self-powered flexible multifunctional sensor with great prosperity in household healthcare, smart mobile medical electronics, and humanoid robots. [Display omitted] • Multi-dimensional force sensing was achieved in a single sensor by using one kind of piezoelectric mechanism. • We designed an intelligent gesture recognition system for future human-machine interaction applications. • Our material design methodologies offer an approach to the multifunctional sensor with prosperity in household healthcare. [ABSTRACT FROM AUTHOR]

In our work, we investigate systematically the deformation and instability of a rotating cylinder of compressible material under fixed end thrust using Neo-Hookean material model. We employ numerical methods to study the solution of the second order differential equation for the radial deformation, which represents the deformation of the cylinder under loading conditions. We further analyse the instability behaviour of the rotating elastic cylinder using the incremental deformation theory and obtain the critical value of angular velocity when buckling occurs. Finally, we plot a phase diagram, which illustrates the regions of stable, buckling and no solution with respect to angular velocity and end thrust. • We developed theoretical model of a rotating cylinder under end thrust, adopted numerical methods to investigate its deformation and instability behaviour, and obtained a phase diagram which depicts the regions of "stable", "buckling", and "no solution" with respect to angular velocity and end thrust. [ABSTRACT FROM AUTHOR]