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Environmental noise has been regarded as major noise pollution with severe hazards to human physical and mental health. The common commercial fiber sound-absorption materials have insufficient low frequencies wave absorbing and fire-resistant ability, limiting their wide application. To solve these problems, a novel strategy combining flexible nanofibers and rGO/MXene nanosheets was proposed to fabricate rGO/MXene/SiO 2 nanofibers composite aerogel with hierarchically porous structure, which possessed an extremely low density of 9.8 mg/cm3 and superior low-frequency sound absorption ability (NRC value of 0.51). The obtained composite aerogel possessed a large deformation up to 80% (corresponding compressive stress of 17 kPa) and quickly recovered. In addition, the as-prepared aerogel could be easily produced on a large scale, providing a reference for the development of new generation of sound-absorbing products. [ABSTRACT FROM AUTHOR]

• A coupled high-order monotonicity-preserving interface capturing scheme for computations of compressible three-phase flows with phase changes is presented. • Numerical results are validated against experimental data. • The characteristics of bubble interactions with a free surface and parallel walls are discussed. • The effects of the initial pressure and non-condensable gas volume fraction on the behavior of the explosion bubble are analyzed. The complex dynamics of two flow problems of vapor explosion bubbles near a free surface and between two parallel plates are simulated by a compressible three-phase flow code. Firstly, a coupled high-order monotonicity-preserving (MP) interface capturing scheme is developed for the numerical computation of compressible three-phase flows, which is followed by validation with previous numerical and experimental data. Phase changes are taken into consideration and the empirical condensation coefficient is calibrated with the experimental data. For both two flow problems, good agreement between the numerical results and reference data is obtained. Most physical phenomena, including the free surface spike, the liquid jet before the impact and the complex interface deformations during multiple expanding and collapsing oscillations, are reasonably well reproduced. Afterwards, the effects of the initial vapor pressure and the non-condensable gas volume fraction in the surrounding water on the behavior of vapor bubbles are analyzed and discussed. It is found that both the initial vapor pressure and the non-condensable gas volume fraction have a substantial influence on the behavior of the bubble. Higher initial vapor pressure does indeed tend to result in larger bubbles. The presence of non-condensable gases tends to hinder the transfer of heat, slowing down condensation and potentially resulting in larger bubbles. When the initial vapor pressure is in the range of 10 to 20 atmospheres and the gas volume fraction is in the range of 0 to 0.2, the maximum vapor bubble volume is found to increase linearly with an increase of the amount of non-condensable gas. [ABSTRACT FROM AUTHOR]

In this work, we prove the uniform regularity of smooth solutions to an Ericksen–Leslie's parabolic–hyperbolic liquid crystals model in a three-dimensional torus. [ABSTRACT FROM AUTHOR]

The performance of the engine highly depends on the fuel mixing process as a significant process to achieve efficient supersonic flight. Current article has attempted to release the effects of different annular lobe-injectors on fuel mixing when Ma >1. Three various annular jet nozzles are expansively investigated for injection of the sonic hydrogen jet at supersonic air crossflow with Mach-4. Comprehensive comparison of the jet structure of these models are performed through the evaluation of Mach and fuel concentration downstream of these lobe-injectors. Comparison of mixing efficiency also indicates that the nozzle with 3-lobe configuration has 25% more fuel mixing performance than other configurations. Our findings also show that mixing performance of annular lobe-injector is about 15% more than simple one for cases with 2-lobe and 4-lobe injectors. • Influence of annular lobe-injector on the fuel mixing of hydrogen jet at supersonic flow is studied. • The mixing performance of the air/fuel jets in various jet conditions is investigated. • Effect of various profiles of shock generator on flame distribution is entirely investigated. • CFD approach is applied for the simulation of the co-jets with sinusoidal shock generator. [ABSTRACT FROM AUTHOR]

[Display omitted] • Develop a portable solar evaporator that can save storage space more than 78%. • Hyperstable plant fibers/chitosan aerogel is constructed without toxic cross-linkers/solvents. • The solar evaporator can endure tremendous and repeated compression over 100 times. • The evaporator is cost-effective and salt-rejecting, working well under various harsh conditions. • High evaporation rate of 1.38 kg m-2 h−1 and solar-to-vapor conversion efficiency of 84.27%. Solar interfacial evaporation is an effective zero-energy method for seawater desalination, and solar evaporator is the key component in this evaporation system. Despite a great deal of solar evaporators have been reported, the poor portability of large-scale evaporators as well as high costs and materials toxicity still restrict their applications. In this work, a portable solar evaporator was constructed with low-cost plant fibers from papermaking pulp, using a facile method in absence of any toxic cross-linkers and solvents. The evaporator exhibited excellent stability and flexibility, and endured tremendous and repeated compression over 100 times. A large-scale evaporator could be compressed to reduce storage space by 78%, which would be portable for individuals. The evaporator presented a high evaporation rate of 1.38 kg m-2h−1, and solar-to-vapour conversion efficiency of 84.27% under one sun irradiation. The portable solar evaporator was salt-rejecting, and worked well under harsh conditions of high salinity and different pH values. The entire material cost of this potable solar evaporator is approximately 1.75 U.S. dollar m−2, much lower than those of conventional solar evaporators. This study provides a new approach for preparing portable and cost-effective solar evaporator. [ABSTRACT FROM AUTHOR]

All-solid-state rechargeable Zn-air battery is deemed to be a promising class of power source for its attractive operational safety and mechanical flexibility. To achieve high performance of Zn-air battery, the density of active sites on the ORR/OER bifunctional electrocatalyst and the maximized access to them are of great importance. In this study, a nitrogen, sulfur and ferric co-doped three-dimensional bifunctional catalyst (FeN x /N,S–C) is developed via a facile and eco-friendly molten salt assisted synthesis. The homogeneously dispersed FeN x species, the surrounding S dopants and the 3D hierarchical architecture synergistically endow FeN x /N,S–C with dense active sites with high accessibility, abundant open pores/channels and efficient mass transfer. Compared with the commercial Pt/C–RuO 2 catalyst, the application of FeN x /N,S–C in all-solid-state rechargeable Zn-air batteries results in enhanced ORR/OER activities, lower charge-discharge voltage gaps and improved 52 h cycling durability, implying its good feasibility in practical application. The all-solid-state FeN x /N,S–C based battery shows no performance decay during charge-discharge cycles when its sodium polyacrylate hydrogel electrolyte is compressed up to 67% strain or stretched up to 400% length, implying the feasibility of the present FeN x /N,S–C catalyst in the usage of stable and flexible electronics. Image 1 [ABSTRACT FROM AUTHOR]

Lightweight and highly porous magnetic polymer foam (MPF) composites were synthesized using a simple, efficient, and environmentally friendly strategy. Their scaffold structure was well controlled using a surfactant and by varying the amount of Fe 3 O 4 nanoparticles (NPs) added to the emulsion solution used in their preparation. The three-dimensional (3D) sponge-like MPFs are microwave-absorbing materials, and their structural and microstructural characteristics were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The magnetic properties of the MPF composites were also characterized. The polymer matrix of the composites exhibited excellent thermal stability. The microwave-absorbing properties of the MPF composites with increasing amounts of Fe 3 O 4 NPs (5 wt%, 10 wt%, and 15 wt%) were systematically studied. The microwave absorption of the polymer foam was enhanced to as high as 82% with the addition of Fe 3 O 4 NPs. Our results demonstrate that the prepared MPF composites have the potential to be used as lightweight, microwave-absorbing materials. Image 1 • Magnetic polymer foam was fabricated by high internal phase emulsion method. • Fe 3 O 4 NPs provide magnetic properties without disturbing porous structure. • The foam exhibited magnetic properties and compressibility. • Microwave absorption was enhanced with macroporous polymer foam/Fe 3 O 4 composite. [ABSTRACT FROM AUTHOR]

Interest in low Reynolds number compressible flows is emerging due to prospective applications like flight on Mars and in the stratosphere. However, very little knowledge is available, both regarding the flow physics underlying this unique regime and the accuracy of numerical methods for its prediction. In this paper, low and high fidelity numerical approaches are compared with experimental measurements on both airfoils and rotors in the low Reynolds number compressible flow regime. It is shown that low fidelity approaches are suited to aerodynamic optimization despite high viscous and compressible effects. In addition, high fidelity approaches help reveal unique flow features of this regime. [ABSTRACT FROM AUTHOR]

Abstract Developing flexible and deformable supercapacitors electrodes based on porous materials is of high interest in energy related fields. We propose a novel approach called "soaking-squeezing-calcining" to fabricate a unique carbon nanotubes melamine sponge electrode, and demonstrate its application as a highly compressible supercapacitor electrode with high performance. Our supercapacitor electrode consists of three-dimensional melamine sponge as flexible skeleton and conductive skeleton, the carbon nanotubes filled in the sponge skeleton by physical adsorption and calcination process to enhance the overall conductivity and mechanical properties. After adding carbon nanotubes, the volume specific capacity of the supercapacitors increases by 3 times and the mass specific capacity is basically unchanged. Furthermore, it is found that its capacity retention rate could still reach 91% after the device is compressed by 50% for 1000 cycles of charging and discharging and 88% in the original uncompressed state for 5000 cycles of charging and discharging, respectively, which deeply proves that the carbon nanotubes reinforced sponge electrode has excellent electrochemical stability. Most importantly, the mechanical strength of the electrode increases by 5 times compared with that without carbon nanotubes. The results indicate that this electrode has the potential to fabricate deformable, robust supercapacitors with stable performance and many other energy devices. Highlights • Volume specific capacity increases by 3 times compared with no carbon nanotubes. • Capacity retention rate could reach 91% after the device was compressed by 50%. • Capacity retention rate could reach 88% for 5000 cycles of charging and discharging. • Mechanical strength raises 5 times after adding carbon nanotubes. [ABSTRACT FROM AUTHOR]

Highlights • Experimental evidence to show concrete response till peak load is non-dissipative. • Propose a new non-dissipative model for cement concrete. • Benchmarked the model with 10 different biaxial experimental studies. • Good correlation (mean R 2 = 0.94) with biaxial and uniaxial experiments. Abstract The validity of some of the assumptions made during systematic development of constitutive relation – homogeneity, isotropy, and non-dissipative response – is examined experimentally by testing plain concrete cylinders in the circumferential displacement controlled uniaxial compression tests. The tested cylinders indicate that the surface strains are not uniform and that the principal direction of the strain varies with the magnitude of the applied load. Hence, these cylinders are either deforming from a stressed state or anisotropic or both. The percentage dissipation computed as the area between the loading and unloading curves normalized using the area under the unloading curve is less than 10 percent up to 90 percent of the peak load. Therefore the mechanical response of concrete can be considered as non-dissipative. Assuming that the magnitude of the residual stresses present in the concrete panels would be small compared to the stresses arising due to the applied load, these residual stresses are ignored. Consequently, using the implicit constitutive theory framework for isotropic and compressible materials undergoing a non-dissipative process from a stress-free reference configuration, a three-dimensional constitutive relation for plain concrete is proposed. The material parameters in the proposed model are estimated from the uniaxial compression test and equal biaxial compression test. These parameters are expressed using initial Young's modulus, initial Poisson's ratio, maximum uniaxial compressive stress, the axial and transverse strain corresponding to the maximum uniaxial compressive stress, maximum equal biaxial compressive stress and the equal biaxial strain corresponding to maximum equal biaxial compressive stress. The ability of the proposed model to capture the response of various grade and type of concrete in ten biaxial experiments reported in the literature is examined. It is found that despite the limiting assumptions, the compression-compression, compression-tension and tension-tension stress strain response of the concrete in these ten experiments are adequately captured by the proposed model with mean R 2 value of 0.94. [ABSTRACT FROM AUTHOR]

Highlights • S-PAA toughness hydrogel was prepared via in-situ polymerization. • S-PAA as polyelectrolyte endowed self-healing and compressibility for supercapacitor. • The supercapacitor based on polyelectrolyte showed remarkable electrochemical performance. Abstract With overwhelming development of electronic technology, flexible electronic devices are spring up in modern today. For fulfilling the trendy and artistic designing of electronic devices, mechanical toughness and self-healable all-solid-state supercapacitors play an essential role of modern electronics. However, the sate-of-the-art polyvinyl alcohol-based electrolyte for all-solid-state supercapacitors neither has tough physical performance nor self-healing, which is hard to implant into special-shaper and repeated-deformation device for energy supplier. A novel electrolyte with mechanical robust and endowed self-healing is prepared by micelle co-polymerization of acrylic acid and octadecyl methacrylate in vinyl-treated sponge (S-PAA). The 3D interconnected skeleton of sponge serves as stress buffers to dissipate energy when physical impact (stretch and compress) is applied, solving the intrinsically poor mechanical performance and easy cracking under repeated-deformation drawbacks of state-of-the-art supercapacitors. The supercapacitor equipped with newly type of electrolyte can be worked under compressing, bending and stretching station. Moreover, the electrochemical performances have no evidence loss even using self-healed fragment electrolyte. [ABSTRACT FROM AUTHOR]

Highlights • A pressure-based method dedicated to the DNS of turbulent two-phase flows is presented. • The Coupled Level Set/VOF method is used to capture the interface and ensure mass conservation. • A reference solution for an oscillating water column configuration has been presented and used as a validation case for the numerical method. • The method is able to handle turbulent atomization processes such as breakup and coalescence, as well as vaporization. • Even in the vaporizing turbulent case, mass conservation is obtained, showing the potential and the robustness of the numerical method. Abstract This study focuses on the development of a pressure based method able to capture compressibility effects and phase change in turbulent two-phase flow DNS, using the Coupled Level Set/Volume of Fluid (CLSVOF) interface capturing method. A compressible VOF equation and a new pressure equation are described, including additional terms due to vaporization and compressibility. First, validation cases without phase change such as a gas-water shock tube and an oscillating water column configuration have been performed. Concerning the first case, obtained results suggests that the method is able to capture accurately the shock wave characteristics. For the second case, a reference solution is computed and compared with DNS results, showing the method accuracy and convergence. Finally, a two-phase Homogeneous Isotropic Turbulence with compressibility and phase change is investigated. Contrary to previous works, the vaporization process has an impact on the flows dynamics. The effects of the vaporization on the gas density is illustrated and compared with a reference solution for a constant vaporization rate. Great agreement is obtained between DNS results and the reference solution. The mass balance between total mass, gas and liquid mass is also shown and demonstrates the efficiency of the CLSVOF interface capturing method regarding mass conservation, even in a turbulent atomization context. [ABSTRACT FROM AUTHOR]

With rapidly growing commercial markets of portable and flexible electronics, flexible supercapacitors (SCs) have become one of the most promising energy storage devices due to their unique characteristics. However, the low operating voltage and energy densities severely restrict their practical application. At the same time, the liquid-electrolyte has leak issues under deformation, resulting in short circuit of the device. Herein, an all-solid-state novel symmetric supercapacitor is designed based on nanostructured δ-MnO 2 @CNTs@sponge electrodes (MCS). The device presents a high voltage (0–2 V), remarkable cycle life (>10,000 cycles; 94.2% capacitance retention) and high energy (28.5 Wh kg −1 with power density of 2780 W kg −1 ). It also processes remarkable compression ability up to 80% with no obvious volume damage. After fully charged with four devices in series, it can easily light up a light-emitting diode (LED) under different compression states without electrolyte leakage. This strategy provides a novel device design method, and can be effectively applied to the future flexible electronic products. [ABSTRACT FROM AUTHOR]

Hyphenating SFC with MS is now routinely performed in analytical laboratories. Major instrument providers supply commercial solutions for coupling SFC and MS, which has facilitated wider adoption of the technology. The current status, however, could be achieved based on the work done by many researchers over decades. Interfacing SFC with MS posed some unique challenges, compared to interfacing MS with LC or GC, demanding special solutions. Several interface designs were tried and tested over the years before suitable solutions could be detected. Additional measures, such as (a) mixing SFC mobile-phase with an additional liquid solvent at the column outlet, and (b) heating the interfacing device, had to be adopted to address some specific challenges. Although such modifications and measures look diverse, there is one factor that drove most of them - compressibility of SFC mobile-phase. There are two objectives of this review - (1) to compile various insights which were reported on describing and optimizing SFC-MS interfacing processes, and (2) to link these insights with the fundamental issue of solvent compressibility. [ABSTRACT FROM AUTHOR]

The periodic vortex shedding from bluff bodies may be used in flow metering applications. However, because the bluff-body is highly confined (typically in a pipe) the shed vortices may interact with the pipe wall; causing an undesirable non-linear behaviour. An experimental investigation has been conducted; examining the vortex-shedding characteristics of highly confined bluff-bodies in pipe flow, at high Reynolds number ( Re D = 4.4 × 10 4 to 4.4 × 10 5 ). The bluff-bodies were comprised of a forebody and tail; both of which affected the primary-shedding characteristics. The shedders typically produced two unsteady modes: Mode-I was associated with the vortex shedding and mode-II resulted from a separation of the pipe-wall boundary layer. The mode-I behaviour allowed two classes of shedder to be defined: long-tails and short-tails. Modes I and II interacted, particularly for long-tailed geometries. When the length-scale of mode-II exceeded 0.8 κ (where κ is the physical scale of the primary shedding vortex), mode-II disrupted mode-I, as the mode-frequency ratio ( f II / f I ) approached an integer value. The coupling of modes I and II caused mode-I to deviate from its preferred Strouhal number. When the deviation exceeded 25–30%, mode-I locked on to the mode-II frequency. This did not happen for short-tailed geometries, as the length-scale of mode-I was always dominant. Mode-coupling for short-tails occurred only when the mode frequencies were equal. [ABSTRACT FROM AUTHOR]

The tips of large horizontal-axis wind turbines can easily reach high speeds, thus raising the concern that compressibility effects may influence turbine wakes and ultimately power production. All past studies have assumed that these effects are negligible. Compressibility effects are assessed here in terms of blade aerodynamic properties and variable density separately. Using the Blade Element Momentum (BEM) method, we find that under normal operating conditions (i.e., wind speed  < ∼ 15 m s −1 and tip speed ratio TSR  < ∼ 12 ) aerodynamic corrections to the lift and drag coefficients of the blades have a minimal impact, thus the incompressible coefficients are adequate. To assess the variable-density effects, numerical simulations of a single turbine and two aligned turbines, modeled via the actuator line model with the default aerodynamic coefficients, are conducted using both the traditional incompressible and a compressible framework. The flow field around the single turbine and its power performance are affected by compressibility and both show a strong dependency on TSR. Wind speed and turbulent kinetic energy (TKE) differences between compressible and incompressible results origin from the rotor tip region but then impact the entire wind turbine wake. Power production is lower by 8% under normal operating conditions (TSR ∼ 8) and 20% lower for TSR ∼ 12 due to compressibility effects. When a second turbine is added, the front turbine experiences similar effects as the single-turbine case, but TKE differences are enhanced while wind speed differences are reduced after the second turbine in the overlapping wakes. These findings suggest that compressibility effects play a more important role than previously thought on power production and, due to the acceptable additional computational cost of the compressible simulations, should be taken into account in future wind farm studies. [ABSTRACT FROM AUTHOR]

Flexible supercapacitors that maintain electrochemical performance under deformation have attracted much attention for the potential application in the flexible electronics market. A compressible and flexible free-standing electrodes sponge and all-solid-state symmetric supercapacitors based on as-prepared electrodes are presented. The carbon nanotubes (CNTs) framework is synthesized by chemical vapor deposition (CVD) method, and then composited with poly (3,4-ethylenedioxythiophene) PEDOT by the electrodeposition. This CNTs/PEDOT sponge electrode shows highest mass-specific capacitance of 147 Fg -1 at 0.5 A g −1 , tuned by the PEDOT mass loading, and exhibits good cyclic stability with the evidence that more than 95% of capacitance is remained after 3000 cycles. Furthermore, the symmetric supercapacitor shows the highest energy density of 12.6 Wh kg −1 under the power density of 1 kW kg −1 and highest power density of 10.2 kW kg −1 with energy density of 8 Wh kg −1 , which exhibits both high energy density and power density. The electrochemical performance of composite electrode also indicates that the operate voltage of device could be extend to 1.4 V by the n-doping and p-doping process in different potential of PEDOT component. This flexible supercapacitor maintains stable electrochemical performance working on different bending condition, which shows promising prospect for wearable energy storage applications. [ABSTRACT FROM AUTHOR]

• The bifunctional silicone endows the molecules more feasibility by chain enlongation. • The synergistic adjustment for flexibility is employed. • The buffer of the precursor facilitates the mild formation of SixPRA-y. • SixPRA-y shows compressibility with good fatigue-resistance (1000-cycle-40% strain). • SixPRA-y exhibits superior hydrophobicity with a lotus effect. • The assembled thermal regulator enables dynamic thermal management through deforming. Lightweight and flexible aerogels are highly demanded for thermal management in the burgeoning aerospace and artificial intelligence (AI) fields. However, the design and preparation of thermal insulating aerogels integrating good flexibility, low density, and superior thermostability through environmentally friendly methods remains challengeable. Herein, by introducing bifunctional silicone, a strategy of chain elongation assisted with pore structure adjustment is developed to achieve the flexibility of thermostable phenolic resin aerogel (PRA). The silicone introduction effectively suppresses the drying shrinkage, thus enabling the employment of ambient pressure drying (APD). The obtained flexible PRA combining high softness (elastic modulus 0.05 kPa), superior deformability (cyclic compressive strain > 60%, damage strain up to 80%), and good fatigue-resistance (compression at 40% strain > 1000 cycles) exhibits low bulk density (0.058 g·cm−3), and low thermal conductivity (0.033 W·m−1·K−1). With these superior properties, it can effectively serve for static thermal insulation below 200 °C with a thickness of 2–3 mm; more attractively, it can perform dynamic thermal management as a regulator through compressing and releasing (eg. temperature 41.9–57.6 °C, 0–40% compression strain, thickness of 30 mm). These merits make the material promising for AI thermal management in fields like outdoors, aerospace, and infrared camouflage. [ABSTRACT FROM AUTHOR]

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]

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 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]

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]

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]

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]

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]

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]

[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]

In this work we consider the isentropic compressible Navier–Stokes equations in three space dimensions. Blow up result will be established, assuming the gradient of the velocity satisfies some decay constraint and the initial total momentum does not vanish. We prove the main result by a contradiction argument, based on the conservation of the total mass and the total momentum. [ABSTRACT FROM AUTHOR]

The increasing demand for flexible electronics encourages the innovative and functional designs of electrode materials with high performance and compressibility. In this work, we report a compressible supercapacitor electrode which is prepared by coating electrically active NiO/MnO 2 /carbon nanotube (CNT) composite onto a sponge. A cube of sugar was used as the template to obtain the sponge through infiltration and cross-linking of polydimethylsiloxane (PDMS). NiO/MnO 2 /CNT was deposited on the PDMS sponge to generate substantial amount of interface, resulting in a specific capacitance of 23 F/g at 0.1 A /g in a three-electrode system and 1.32 F/g at 0.5 mA in a symmetric supercapacitor. The proposed system exhibits excellent cycling stability with capacitance retention over 10.000 cycles. The strong adhesion of the binary metal oxides and carbon material onto the porous nonconductive sponge enables mechanical stability under compression-release cycles. Our study indicates that this electrode is a promising candidate for applications in flexible electronics. Furthermore, this research might guide the development of flexible, high-performance, and low-cost electrodes, which will be useful in wearable energy storage systems. [Display omitted] • Highly compressible sponge Supercapacitor electrode produced by coating electrically active NiO/MnO 2 /carbon nanotube (CNT) composite onto a sponge. • The flexible structure is obtained by replicating the structure of a sugar cube using polydimethylsiloxane (PDMS). • The electrochemical activity on the flexible platform was provided by depositing NiO/MnO 2 /CNT on the PDMS sponge. • Excellent electrochemical performance of MnO 2 /NiO/CNT composite results with the flexibility and porous structure of the sponge. [ABSTRACT FROM AUTHOR]

In an extrusion process, an external gear pump can be used to control the flow rate of the system. When extruding polymers, the viscosity is quite high, resulting in negligible inertia and thus laminar flow. The external gear pump contains two gears, one driven by a motor and one driven by means of contact with the other gear. In our previous work, the flow of a viscous fluid through an external gear pump was studied using the finite element method. Local mesh refinement was applied based on the respective distance between boundaries. Furthermore, the rotation of both gears was imposed. In this work, the rotation of one gear is imposed, whereas the other gear is freely rotating. However, the minimum distance between the gears is limited to a minimum value. When this value is reached, contact is assumed and also the rotation of second gear is imposed. A reversion of the torque on this gear results in a release of contact. In this manner, a quasi driver/driven situation is created in the numerical simulations. It is observed that contact is released periodically, and thus cannot be assumed present continuously, as is often prescribed. Non-Newtonian material properties, such as shear thinning and the pressure dependence of the density or the viscosity, alter how long contact is released during a tooth rotation. [ABSTRACT FROM AUTHOR]

Renewable biomass-based aerogels with excellent absorption properties for oil and organic solvent have been concerned recently. However, the development of cost-effective and compressible green aerogel is still a great challenge and a research hotspot. In this work, a novel hydrophobic konjac glucomannan/corn stalk fibers (KGM/CSFs) aerogel with porous three-dimensional structure featured low density, high porosity, good compressibility and hydrophobicity (146°) were prepared and used to selectively remove different organic liquids from oil/water mixtures. The effects of the amount of corn stalk fibers (CSFs) on the physical properties such as density, porosity and mechanical properties of the aerogel were investigated in detail. The obtained hydrophobic KGM/CSFs aerogel exhibited high absorption capacity (24.76 g/g-58.07 g/g) for various organic liquids. After 10 cycles, the adsorption capacity of the aerogel for chloroform and diesel remained above 90% of the initial adsorption capacity, showing excellent reusability. More importantly, the oils or organic solvents could be selectively absorbed by the hydrophobic KGM/CSFs aerogel from oil/water mixtures with a separation efficiency of over 99.38%. Considering the advantages of eco-friendliness, low cost and simple preparation process, the hydrophobic biomass-based aerogel prepared from waste corn stalks can be used as a promising absorbent for efficient and selective absorption of oils or organic solvents. [Display omitted] • 3D porous aerogel was fabricated by combining KGM and waste corn stalks. • Hydrophobic hexadecyltrimethoxysilane functional groups were added via a facile dip-coating method. • The as-prepared HKC-4 exhibited a high selectivity in absorption of oil or organic solvent. • The as-prepared HKC-4 demonstrated high separation efficiency of oil/water mixture. [ABSTRACT FROM AUTHOR]

• An rGO aerogel was prepared via oriented freezing-dried method. • High absorption capacity for organic solvents. • High mechanical compression and recyclable materials. It is essential to synthesize materials that fit versatile application backgrounds in our life through structural design method. As we all know, channel design is one of the crucial factors in catalysts and absorbent materials synthesis. In this study, we have fabricated honeycomb-like structured and porous rGO (reduced graphene oxide) aerogels by oriented structural design. The synthesis process endowed the rGO aerogels with the regular capillary channels. And it was demonstrated to possess a high absorption capacity for organic solvent ranging from 251 to 396 times (chloroform) of its own mass. Moreover, owing to its high mechanical compression, it can be recycled many times by squeezing out the organic solvent from the channels. Due to its unique performance in absorption and mechanical compression, the rGO aerogel is an ideal absorbent for polluted water treatment applications. [ABSTRACT FROM AUTHOR]

Abstract: This study deals with the numerical solution of a 2D unsteady flow of a viscous fluid in a channel for low inlet airflow velocity. The unsteadiness of the flow is caused by a prescribed periodic motion of a part of the channel wall with large amplitudes, nearly closing the channel during oscillations. The channel is a simplified model of the glottal space in the human vocal tract. Four governing systems are considered to describe the unsteady laminar flow of a viscous fluid in the channel. The numerical solution is implemented using the finite volume method (FVM) and the predictor–corrector MacCormack scheme with artificial viscosity using a grid of quadrilateral cells. The unsteady grid of quadrilateral cells is considered in the form of conservation laws using the Arbitrary Lagrangian–Eulerian method. The numerical simulations of flow fields in the channel, acquired from a developed program, are presented for inlet velocity and Reynolds number and the wall motion frequency 100 Hz. [Copyright &y& Elsevier]

A compressible Maxwell-Cahn-Hilliard binary fluid mixture in conjunction with the Sanchez-Lacombe equation of state is used to develop a one-dimensional linear model that describes acousto-spinodal decomposition by pressure-induced phase separation in compressible polymer solutions in the absence of externally imposed flow. The integrated model extends previous work acousto-spinodal decomposition of compressible polymer solutions using Euler and Newtonian model fluids [1,2]. Acousto-spinodal decomposition by pressure-induced phase separation couples density wave phenomena with mass transfer driven by the spinodal decomposition process. For viscoelastic acousto-spinodal decomposition the relevant parameters are the Mach number Ma (ratio of diffusion speed to density wave speed) and the Reynolds Re and Deborah De numbers. Concentration gradients act as a sound source in the density wave equation that feeds back into the mass diffusion equation producing, under sufficiently low Ma oscillatory spinodal decomposition. This oscillatory effect is generally suppressed by viscosity and enhanced by elasticity. The limiting standing waves (1/Re→0,1/Ma²→0,De→0) that can be generated include elasto-acoustic, viscoelastic, and visco-acoustic. Concentration fluctuations accompanied with density fluctuations generate velocity, which are a unique feature of acousto-spinodal decomposition. The role of elasticity on the rate of demixing and selection of length scales is characterized; it is found that at high viscosity and low mass diffusion, higher elasticity De is required to reach absolute maximum growth rate R∞max, which corresponds to an incompressible Euler fluid. Total structure factor calculations are shown to be qualitatively consistent with experiments at low wave vectors. Acousto-spinodal decomposition is a novel process that offers new processing and characterization routes for polymer solutions and melts. [ABSTRACT FROM AUTHOR]

Highlights: [•] A Lagrangian–Eulerian compressible model for the Navier–Stokes equations. [•] Propagation of sound waves in a supercritical fluid. [•] Modeling of phase-separation from monophasic to diphasic states near the critical point. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new compressible phase field model of two different immiscible fluid components, in which the density of each phase is variable. In order to establish the compressible phase field model, a new P-V-T equation of state is introduced to solve the pressure. The new model is derived by the physics law of conservation, and conforms to the second law of thermodynamics. The model adopts an innovative expression of Helmholtz free energy, taking into account the new state equation of pressure and the varying material properties of each phase. A high-order accurate numerical scheme is introduced to solve the model equations. The convection terms of the governing equations are discretized by the fifth-order WENO scheme, and the residual terms are discretized by the Lax–Friedrichs method. Finally, the reliability and validity of the compressible two-phase model are verified by numerical simulations. • The compressibility of fluid cannot be ignored when the velocity is high. • Deriving compressible phase field equation based on entropy increasing principle. • The viscosity and thermal conductivity of mixture are different. • An equation of state for mixture is established. [ABSTRACT FROM AUTHOR]