Flexible Wall Research Articles

Research on the Mechanical Properties of Flexible Material Backfilling Wall in Gob-Side Entry Retaining

In order to solve the problems of the uneven deformation of Gangue Filled Wall and the difficulty of large-scale promotion of roadway side support, and to achieve the purposes of direct disposal of coal mine waste, reducing costs, and protecting the environment, the failure mechanics model of the bagged gangue was established, and the mechanical action relationship between longitudinal external load and transverse external load of gangue woven bag was deduced. Through the uniaxial compression test of large-scale flexible backfill (coal gangue of different particle sizes), it was obtained that when the strain is 0.2, the bearing capacity of particles with particle sizes between 0 and 10 mm is greater than 5 MPa, and when the strain is 1.27, the bearing capacity of particles with particle thicknesses between 10 and 20 mm is greater than 0 mpa, which meets the requirements of resistance value and resistance growth rate of gob side entry. In the “load deflection” test of backfill (gangue) samples, it was found that the maximum failure load of wet shotcrete is greater than that of dry shotcrete, and the wet shotcrete can withstand greater deformation under the same load conditions. Through the analysis of the experimental results of “flexural strength thickness” and “maximum failure load thickness”, it was finally determined that the thickness of the spray layer with good flexibility and sufficient support force is controlled at about 80 mm.

Numerical studys on passive paramerters of a fluid-solid interaction problem derived by natural convection in a circular enclosure

The natural convection through a partitioned circular enclosure by a deformable middle wall was analyzed. To solve the FSI problem, a forceful connection between the fluid and flexible wall was established. In order to solve the problem under consideration, the Arbitrary Lagrangian-Eulerian (ALE) perspective was utilized. The finite element method (FEM), was also unilized in solving a set of model equations. Effect of wall Angle (30 ≤ η ≤ 90), flexibility (0.71 ≤ Eτ ≤ 200), Position of heat source and sink (-60 ≤ α ≤ +60) has been studied within a circular enclosure. The results indicate that a reduction in flexibility reduces the force (stress) applied to the wall as well as the average Nusselt number to some extent. Also, Increased angle of the wall leads to an enhancement in the Nu. The maximum applied stress and also wall distortion occur at specific positions of hot and cold sector, the buoyancy force and, therefore, the strength of the fluid flow are also higher, causing the heat transfer rate to increase. For The average Nusselt number, A decrease of 8.5 % for η = 90° has been reported compared to η = 30°. Also, the average Nusselt number for α = −60° is up to 124.5 % higher than for α = 60°.

Cooling of hot cylinder placed in a flexible backward-facing step channel

This paper copes with the mixed convection heat transfer and fluid–structure interaction (FSI) of a hot cylinder placed in a backward-step channel. The step is set to be flexible and deforms according to the force imparted by fluid. To attain the best cooling, different configurations of the flexible step were assessed. Equations governing the problem are solved using the finite element technique with the Arbitrary Lagrangian–Eulerian (ALE) approach to go along the moving domain. The influential parameters of such a problem are the Reynolds number Re, Richardson number Ri and the configuration of the flexible back step. Results demonstrated an improvement in the Nusselt number where at Ri = 100, a step of horizontal flexible wall augments the Nusselt number by 7.3% and 1.4% when Re = 100 and 500, respectively. Including the pressure drop in a performance criterion, it is shown that making the vertical wall of the step flexible (VFW) improves the aspects of heat transfer and the hydrodynamic of low Reynolds number, while at high Reynolds number, all suggested configurations of flexible step do not improve the performance criterion. It is found also that Reynolds number greatly improves the performance criterion while Richardson number does not.

Spongy all-in-liquid materials by in-situ formation of emulsions at oil-water interfaces

Printing a structured network of functionalized droplets in a liquid medium enables engineering collectives of living cells for functional purposes and promises enormous applications in processes ranging from energy storage to tissue engineering. Current approaches are limited to drop-by-drop printing or face limitations in reproducing the sophisticated internal features of a structured material and its interactions with the surrounding media. Here, we report a simple approach for creating stable liquid filaments of silica nanoparticle dispersions and use them as inks to print all-in-liquid materials that consist of a network of droplets. Silica nanoparticles stabilize liquid filaments at Weber numbers two orders of magnitude smaller than previously reported in liquid-liquid systems by rapidly producing a concentrated emulsion zone at the oil-water interface. We experimentally demonstrate the printed aqueous phase is emulsified in-situ; consequently, a 3D structure is achieved with flexible walls consisting of layered emulsions. The tube-like printed features have a spongy texture resembling miniaturized versions of “tube sponges” found in the oceans. A scaling analysis based on the interplay between hydrodynamics and emulsification kinetics reveals that filaments are formed when emulsions are generated and remain at the interface during the printing period. Stabilized filaments are utilized for printing liquid-based fluidic channels.

Wave impact on a rigid and flexible wall using various viscous fluids during sloshing

This paper addresses a study of wave impacts on the chamfered shape of a structure during sloshing, using two different fluids through experimental analysis. Horizontal oscillations are carried out on the tank under various excitation frequencies at a fixed amplitude. Rigid and relatively flexible walls are considered for measuring pressure impact and structural deformation from the wave impacts. Various wave impulses are directed at the sidewall, and the structural deformations are discussed in detail. Wave impacts for various fluids are carried out, from which the pressure-time history, strain values, and free-surface deformation measurements are highlighted. Through the analysis, the breaking wave gets distorted by bottom chamfer at around the vertical portion of the wall. Therefore, physical results are changed likely to having with the wave strike the wall. The impact from more viscous fluids have also been found to reduce both the dynamic pressure and structural strain at practically the same rates in comparison with less viscous fluids.

Thermal transport of two-phase physiological flow of non-Newtonian fluid through an inclined channel with flexible walls

Magnetohydrodynamics (MHD) of a non-Newtonian fluid with heat transfer through a porous medium is examined here. Jeffrey fluid is taken as the base liquid with suspends with homogenous and spherical solid particles. A peristaltic wave travels along the flexible walls of the channel. Flow is caused by the expansion and contraction of the walls along with the gravitational force. Lubrication effects are considered on both flexible walls of the channel. An exact solution is obtained for the two-phase flow of Jeffrey fluid with heat transfer. A comprehensive parametric study is carried out to analyze the role of pertinent parameters and it is inferred that a porous medium supports the flow Darcy number while strong magnetic fields hamper the flow. More thermal energy is contributed due to radiation causing a reduction in the velocity of the fluid whereas the temperature profile declines in response to varying the permeability of the porous medium. Finally, the comparative analysis reveals that Jeffrey multiphase suspension is more prominent than Newtonian multiphase fluid.

Systematic Literature Review of Hearing Preservation Rates in Cochlear Implantation Associated With Medium- and Longer-Length Flexible Lateral Wall Electrode Arrays.

BackgroundThe last two decades have demonstrated that preoperative functional acoustic hearing (residual hearing) can be preserved during cochlear implant (CI) surgery. However, the relationship between the electrode array length and postoperative hearing preservation (HP) with lateral wall flexible electrode variants is still under debate.Aims/ObjectivesThis is a systematic literature review that aims to analyze the HP rates of patients with residual hearing for medium-length and longer-length lateral wall electrodes.MethodA systematic literature review methodology was applied following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) recommendations to evaluate the HP rates of medium-length and longer-length lateral wall electrodes from one CI manufacturer (medium length FLEX 24, longer length FLEX 28 and FLEX SOFT, MED-EL, Innsbruck, Austria). A search using search engine PubMed (https://www.ncbi.nlm.nih.gov/pubmed/) was performed using the search terms “hearing preservation” or “residual hearing” and “cochlear implant” in “All fields.” Articles published only in English between January 01, 2009 and December 31, 2020 were included in the search.ResultsThe HP rate was similar between medium-length (93.4%–93.5%) and longer (92.1%–86.8%) electrodes at 4 months (p = 0.689) and 12 months (p = 0.219). In the medium-length electrode group, patients under the age of 45 years had better HP than patients above the age of 45 years.ConclusionsBoth medium-length and longer electrode arrays showed high hearing preservation rates. Considering the hearing deterioration over time, implanting a longer electrode at primary surgery should be considered, thus preventing the need for future reimplantation.

Peristaltic pump with heat and mass transfer of a fractional second grade fluid through porous medium inside a tube

In magnetic resonance imaging (MRI), this MRI is used for the diagnosis of the brain. The dynamic of these particles occurs under the action of the peristaltic waves generated on the flexible walls of the brain. Studying such fluid flow of a Fractional Second-Grade under this action is therefore useful in treating tissues of cancer. This paper deals with a theoretical investigation of the interaction of heat and mass transfer in the peristaltic flow of a magnetic field fractional second-grade fluid through a tube, under the assumption of low Reynolds number and long-wavelength. The analytical solution to a problem is obtained by using Caputo's definition. The effect of different physical parameters, the material constant, magnetic field, and fractional parameter on the temperature, concentration, axial velocity, pressure gradient, pressure rise, friction forces, and coefficient of heat and mass transfer are discussed with particular emphasis. The computed results are presented in graphical form. It is because the nature of heat and mass transfer coefficient is oscillatory which is following the physical expectation due to the oscillatory nature of the tube wall. It is perceived that with an increase in Hartmann number, the velocity decreases. A suitable comparison has been made with the prior results in the literature as a limiting case of the considered problem.

Peristaltic mechanism of hydromagnetic Jeffrey fluid having variable thermal conductivity and slip conditions

In this study, we focus on the slip effects on the peristaltic unsteady flow of magnatohydromagnetic Jeffrey fluid in a flow passage with non-conducting and flexible boundary walls. The effect of the magnetic field with varying thermal conductivity is taken under the influence of heat transfer analysis. The dimensionless system of PDEs is solved analytically, and the obtained results are computed for the temperature, pressure drop, the axial pressure gradient, axial velocity, and then these results are discussed for different values of the physical parameters of our interest. For the stream functions, the contour plots are also obtained which indicates the exact flow behavior within the flow channel, and the effects of the physical parameters on Jeffery fluid within the flow channel are discussed briefly. Our results indicate that the heat transfer coefficient decreases with an increase in thermal slip and velocity slip parameters. Furthermore, it shows that the size of the trapped bolus is greater for the inclined magnetic field as compared to the transverse magnetic field.

Investigation on orbital EDM for double-hole thin wall of integrated flexible joint

The thin neck structure of integrated flexible joint is the key factor to realize high-precision navigation in dynamically tuned gyroscope. The components of the thin neck structure include two adjacent circular holes and a thin-walled structure between the two holes. The thin wall is vulnerable to be deformed under the external loading which is generated by the tool when using traditional machining methods such as drilling and boring. Simultaneously, pronounced fabrication cost will occur as the cutting tools are also ready to be damaged for machining small holes based on superhard materials. To resolve above problems, a machining method is proposed for the structure of double-hole thin wall in the step-by-step orbital electrical discharge machining (EDM) by using a high rotation speed electrode. The procedure for EDM of double-hole flexible thin wall is designed, and the processing parameters of each step machining are optimized though orthogonal experiment and signal-to-noise ratio analysis. The machining experiments of double-hole thin wall of 3J33B material are proceed using the optimized parameters. The results show that the hole diameter of the double-hole flexible thin wall is 2 mm, the hole depth is 8 mm, and the average thickness of the thin wall is about 46.5 μm. The thickness range between the measured point and the average is 1.55 μm. Comparing with average thickness of 46.5 μm, the error is less than 3%, and the overall thickness is uniform relatively.

Biocompatible hydroxyapatite nanoparticles as templates for the preparation of thin film polyelectrolyte multilayer nanocapsules

Thin films called polyelectrolyte multilayers could be formed by alternate adsorption of positively and negatively charged polyelectrolytes. In the case of adsorption on nanoparticles followed by the dissolution of the template, it is possible to prepare hollow polyelectrolyte capsules. Due to a large number of available polymeric compounds and easily tunable multilayer properties, these systems find their application in various fields such as biomedicine and catalysis. In this study we focused on the design, synthesis and characterization of capsules of nanometer dimensions made of nontoxic weak polyelectrolytes, poly(allylamine) and poly(acrylic acid) in a water medium using fully biocompatible hydroxyapatite nanoparticles as template. The formation of the polyelectrolyte multilayer was monitored by measuring the electrophoretic mobility of particles. After the optimization of the core decomposition conditions, hollow polyelectrolyte capsules were prepared by dissolution of the template in the presence of HCl. Further characterization was performed using Fourier-transform infrared spectroscopy, energy dispersion X-ray spectroscopy, dynamic light scattering, scanning electron microscopy, and atomic force microscopy. With these techniques, the chemical composition, structure, size, morphology and stability of obtained nanocapsules were determined. It was found that the capsules are of a rather narrow size distribution ranging from 100 to 250 nm with a flexible capsule wall being only a few tens of nanometers thick which is very important in the case of future applications in the field of drug delivery. Moreover, the dispersions of nanocapsules were stable for at least 40 days. This extreme stability of nanocapsules could be probably attributed to their low mass, small dimensions, and high surface charge.

The Influences of Slippage and Hall Currents on Peristaltic Transport of a Maxwell Fluid with Heat and Mass Transfer Through a Porous Medium

In this paper, the effects of slip velocity and Hall currents on peristaltic motion of a non-Newtonian fluid with heat and mass transfer through a porous medium inside a symmetric horizontal channel with flexible walls are studied. The fluid obeys Maxwell model, the ohmic and viscous dissipations are taken into account. Some of partial differential equations describe the fluid motion with the appropriate boundary conditions are written in dimensionless form and simplified by using the approximations of long wavelength and low Reynolds number. These equations are solved analytically, and the stream function, pressure rise, temperature, and concentration distributions are obtained as functions of physical parameters of the problem. The effects of the parameters of the problem on these solutions are discussed numerically and illustrated graphically through a set of figures. It is found that the physical parameters played important roles in controling the obtained solutions.

Assessment of one and two-dimensional molecular diffusion of chloride ion through ceramic powder waste-bentonite mixture as landfill liner

One of the major problem in constructing liners that are exposed to leachate is that every material is not able to prevent transmission of contaminant to protect water resource. Lack of water resources worldwide demands for a prompt measure in order to protect extant resources and to minimize wastage growing threat on the environment. In this study, one & two-dimensional (1-D) & (2-D) diffusion test of chloride ion coupled with conductivity were conducted on Ceramic Powder Waste-Bentonite mixture (CPW-B) to investigate the capability of its use as contaminant barrier liner and its potential impact on surroundings. Parameters considered for the laboratory study were Bentonite content (BC) and Leachate height (LH). The test results indicate that there is a significant improvement in diffusion coefficient of the mixture compared with pure CPW. The compound is able to meet the standards when 30% dry weight of bentonite at least is added in CPW-B mixtures. Furthermore, the hydraulic conductivity of compounds in various pressures and variety of bentonite content was determined by the flexible wall triaxial hydraulic conductivity apparatus. The obtained hydraulic conductivities is in the range of values recommended for the compacted clayey liners and therefore, this material is acceptable in terms of advection transport.

Theoretical Study on Design of Composite Lining Structure with Rigid–Flexible Combination for Trenchless Pipeline Rehabilitation

Trenchless rehabilitation lining can be divided into flexible solid wall lining structures, rigid lining structures and rigid–flexible composite lining structures. This paper reviews the research status of the design theory of trenchless rehabilitation lining pipes, analyzes the theory of rigid–flexible composite lining structures, and points out that the value of the factor determined from non-grouting angle K1 is not clear in the design formula of the rigid–flexible composite lining structure mentioned in the ASTM ‘Standard Practice for Installation of Machine Spiral Wound Poly (Vinyl Chloride) (PVC) Liner Pipe for Rehabilitation of Existing Sewers and Conduits (ASTM F 1741)’. The value of K1 was obtained by the numerical analysis method with MATLAB software. Through the analysis of the variation trend of the K1 value, it is concluded that the design formula in the ASTM standard is only applicable to the case of incomplete grouting filling between the original pipe and the lining pipe, and is not applicable to the composite lining pipe with complete grouting filling. Finally, the explicit formula of the non-grouting angle is obtained by fitting, which is more convenient to use.

Highly Sensitive Temperature-Pressure Bimodal Aerogel with Stimulus Discriminability for Human Physiological Monitoring.

Multimodal sensor with high sensitivity, accurate sensing resolution, and stimuli discriminability is very desirable for human physiological state monitoring. A dual-sensing aerogel is fabricated with independent pyro-piezoresistive behavior by leveraging MXene and semicrystalline polymer to assemble shrinkable nanochannel structures inside multilevel cellular walls of aerogel for discriminable temperature and pressure sensing. The shrinkable nanochannels, controlled by the melt flow-triggered volume change of semicrystalline polymer, act as thermoresponsive conductive channels to endow the pyroresistive aerogel with negative temperature coefficient of resistance of -10.0% °C-1 and high accuracy within 0.2 °C in human physiological temperature range of 30-40 °C. The flexible cellular walls, working as pressure-responsive conductive channels, enable the piezoresistive aerogel to exhibit a pressure sensitivity up to 777 kPa-1 with a detectable pressure limit of 0.05 Pa. The pyro-piezoresistive aerogel can detect the temperature-dependent characteristics of pulse pressure waveforms from artery vessels under different human body temperature states.

Investigation on Water Transformation and Pore Structure of Cement-Stabilized Dredged Sediment Based on NMR Technology.

Cement-stabilized dredged sediment (CDS) when used as a new road construction material cannot only solve the problem of abandoned sediment disposal, but also effectively save natural soil resources. This study aimed to evaluate the strength and permeability of CDS and establish corresponding prediction models from the perspective of a stabilization mechanism. The soil–water composition and pore size distribution were investigated by the nuclear magnetic resonance (NMR) technique. The results demonstrated that more liquid pore water inside the CDS specimen transformed into combined water with cement hydration. The amount of combined water, which essentially characterized the hydration process of cement, presented a linear relationship with log (t). The cementation and filling action of hydrates resulted in the transformation of large pores into smaller ones, hence the optimal pore size decreased with an increasing curing period and cement content. The stress–strain curves and hydraulic conductivity were determined based on unconfined compression and flexible wall penetration tests, respectively. The unconfined compressive strength increased exponentially with the amount of combined water, and the functional correlations of hydraulic conductivity and micropore parameters were established. The reliability of the NMR technique as a new method to study the microscopic evolution mechanism of the strength and permeability of CDS was further verified by scanning electron microscopy and mercury intrusion porosimetry tests.

Simplified solution for seismic earth pressures exerted on flexible walls

Seismic earth pressures acting on basement walls and retaining walls are most commonly computed using limit state methods, in which the effects of earthquake shaking are represented by a horizontal body force in an active soil wedge. Limit state methods provide a poor physical representation of the fundamental mechanisms that give rise to seismic earth pressures, which depend on relative wall–soil displacements. Such displacements are a consequence of soil–structure interaction, which, in the absence of a strong inertial component (e.g. from a connected structure), are mainly sensitive to the ratio of wavelength-to-wall height and relative wall-to-soil flexibility. We present a simplified single-frequency procedure for computing seismic earth pressures applied to flexible retaining structures by vertically propagating shear waves. The procedure accounts for the first-order wavelength and wall flexibility effects while simplifying a number of secondary effects in a manner that produces a slightly conservative outcome. Input parameters to the proposed solution are readily attainable for engineering design applications. For typical earth retention systems, earth pressures computed using the proposed procedure are lower than those computed using limit state solutions. Predictions from the proposed solution compare well with results of numerical simulations and centrifuge modeling from literature, whereas limit state procedures either do not provide a physically meaningful solution or produce strongly biased predictions (overprediction of experiments, underprediction of available simulations).

Modeling and Fatigue Characteristic Analysis of the Gear Flexspline of a Harmonic Reducer

The failure of harmonic gear drive is mainly caused by the fatigue fracture of flexible wheels and the fatigue damage of flexible bearings. In this paper, the stress sensitivity and fatigue life characteristics of flexible wheels with thin-walled vulnerable components are studied. Firstly, the structure of the flexible wheel of a B3-80 general harmonic gear reducer is designed, the finite element model of the flexible wheel is established by using ANSYS finite element software, and the finite element analysis results are compared with the theoretical calculations to verify the correctness of the model. Finally, by changing the cylinder length, smooth cylinder wall thickness and load, the maximum equivalent stress curves of the flexible gear ring, smooth cylinder and flexible wheel bottom are obtained, and the influence law of structural parameters on the stress characteristics of flexible wheel is obtained. At the same time, the influence laws of flexible wheel cylinder length and smooth cylinder wall thickness on the fatigue life of flexible wheel is studied, which provides a theoretical basis for the structural optimization design of the cup flexible wheel.

Air and hydraulic flow characteristics of polymer amended bentonite based unsaturated GCLs

Geosynthetic clay liners (GCLs) are used in landfill applications because of their high deformation resistance and excellent self-healing ability. In the present study, air and hydraulic flow characteristics of natural bentonite based GCL (GCL-N) and polymer amended bentonite based GCL (GCL-A) were assessed using air permeability and hydraulic conductivity measurements. The airflow characteristics of GCLs were studied at various apparent degrees of saturation (Sa) and corresponding suction using a custom-designed air permeability test setup. The effect of desiccation on the airflow characteristics of GCL-A was also examined. Further, hydraulic flow characteristics of virgin and desiccated-rehydrated GCLs were assessed using a flexible wall permeameter. The water absorption capacity of GCL-A is relatively higher than GCL-N, irrespective of the stress state. For any chosen Sa, air permeability of GCL-A is lower than GCL-N. Moreover, with the decrease in the suction from 2500 kPa to 1000 kPa, the air permeability of virgin GCL-A has reduced from 9 × 10−12 m2 to 3.57 × 10−16 m2 while the desiccated-rehydrated GCL-A has reduced from 8.86 × 10−11 m2 to 1.9 × 10−13 m2. The hydraulic conductivity of GCL-A is two orders of magnitude less than GCL-N, which shows the better performance of GCL made with amended bentonite.

Numerical Study of the Aerodynamics of a Hovering Hummingbird’s Wing with Dynamic Morphing

To deepen our understanding of the aerodynamics by which hummingbirds use flexible wings to hover efficiently during flapping flight, a three-dimensional wing model with dynamic morphing was developed according to the morphological and kinematic data of a hovering hummingbird’s wing. Navier-Stokes equations were solved on a dynamically deforming grid to study wing aerodynamics. In numerical simulations, boundary-based smoothing and overset methodologies were used in combination to update the interior nodes of cells in the computational domain, allowing those nodes to accommodate the motion of the flexible wall. This study showed that the leading edge vortex (LEV) attached to the wing was stable during the downstroke but extremely unstable and shed continuously during the upstroke. In the results of the downward stroke, the different vortices separated from the surface and formed a vortex ring. The difference is that the leading edge vortex induced a vortex ring near the root and a smaller and weaker vortex ring near the wingtip during the upstroke. A significant enhancement in aerodynamic forces was found during the downstroke, along with a large number of power consumptions. We found that the asymmetry in the time-averaged vertical force between the two half strokes was 3.5, and the value was higher than that reported earlier. Aerodynamic force coefficients and efficiency matched well with those of another hummingbird wing (the ruby-throated hummingbird). It is worth noting that hummingbirds can maintain a similar wingtip speed by flapping their wings, but different strategies are adapted to hover efficiently due to the differences in size and body weight. The results of this study help to better understand the aerodynamics of the hovering hummingbird.