Cylindrical Configuration Research Articles

Influence of cylindrical magnetron sputtering configurations on plasma characteristics

ObjectiveIn the present paper, the influence of cylindrical magnetron configurations on the fundamental plasma parameters of the axial magnetic field was described in more detail. MethodsThe chamber of this system has consisted of two coaxial cylinders which are used as the electrodes of the system with the magnetic solenoid coil present in the outer cylinder to generate the axial profile of the magnetic field at different coil currents (from 2 A to 8 A). The plasma parameters of the normal glow discharge region are diagnosed. ResultsThe results showed that the cylindrical magnetron configurations had a significant impact on the characteristics of the normal glow regions. The cylindrical magnetron configurations have slight effect on the axial profile of E × B drift velocity and the cyclotron frequency. By changing the configuration plasma parameters (The electron temperature, electron number density, and Debye length) their values changed.

Evaluation of Approximate Expressions to Calculate the Area of the Intersection between a Sphere and a Cylindrical Plane

Cylindrical packed beds of spheres are found in many industrial and practical applications where heat and mass transfer and fluid flow occur. A proper understanding of the porous structure is imperative for the analysis and design of the performance of packed beds. The porosity of the packed bed and in particular the radial variation in porosity is of interest. When the positions and sizes of the spheres in the packed bed are known, the areas of the intersections between the spheres and selected cylindrical planes can be used to obtain the radial variation in porosity. The aim of the study is to evaluate the performance of approximate expressions that had been derived to calculate the intersection areas. Firstly, the ability of the approximate expressions to calculate the intersection area is evaluated by considering several typical sphere–cylindrical plane configurations. Secondly, the application of the approximate expressions to obtain the radial variation in porosity for a selection of cylindrical packed beds is evaluated. It is concluded that the approximate expressions should only be applied to packed beds with aspect ratios larger than 6 and for radial positions larger than 1.5 sphere diameters from the centre line of the cylindrical packed bed.

Energy dissipation in multistable auxetic mechanical metamaterials

Multistable mechanical metamaterials are periodic structures whose unit cells show bistable configurations. The snap-through behavior of the unit cell enhances the energy dissipation of the metamaterials. The materials are reusable and can dissipate energy multiple times since the deformation is within the elastic region. This paper presents two types of two-dimensional auxetic metamaterials: the shuriken-shaped motif with four axes of symmetry and the triangle motif with six axes of symmetry. The cylindrical and three-dimensional (3D) configurations are designed with the geometric topology method. We carry out experiments with 3D printed samples, finite element analysis (FEA), and theoretical investigation to reveal the various mechanisms of energy dissipation. The results demonstrate that the planar metamaterials exhibit different energy dissipation along various loading directions. Each type of metamaterial exhibits discrepant force-displacement characteristics. The triangle motif performs better than the shuriken-shaped motif in terms of energy dissipation along some loading directions. The proposed auxetic metamaterials perform better than the conventional multistable structures with zero Poisson’s ratio. Energy dissipation and auxetic behavior of the typically cylindrical and 3D metamaterials are verified numerically and experimentally.

Simulation study on charging performance of the latent energy storage heat exchanger with a novel conical inner tube

The application of a latent heat thermal energy storage (LHTES) system can effectively solve the problem of the mismatch between the energy supply and demand. However, most studies focus on the traditional cylindrical configuration with a low heat storage rate, which limits the wide application of LHTES systems. The configuration optimization of a vertical shell-and-tube LHTES unit is carried out in this paper to enhance heat storage rate, and the effects of cone angle values (0–10°) in the conical shell and conical tube configurations on the heat storage performance are explored by numerical simulations. The results show that these two kinds of conical configurations both significantly improve the melting rate of the phase change material (PCM) compared with the cylindrical unit. However, when the cone angle is the same, the heat transfer enhancement effect of the latter is found to be superior to that of the former. Moreover, the complete melting time is shortened by 46 % as the cone angle of the inner tube increases from 0° to 10°. More importantly, a novel conical tube configuration design is proposed to eliminate the hard-to-melt zone at the bottom of the LHTES unit with the conical tube, then the effects of different tilting heights (60–170 mm) and bottom annulus distances (0–10 mm) are investigated. The results demonstrate that the melting rate increases with the increase in the tilting height, but the increased amplitude of that gradually reduces. Besides, the average heat storage rate shows a trend of first increasing and then decreasing with the increase in the distance of the bottom annulus. When the bottom annulus distance is 2 mm, the average heat storage rate reaches the maximum value, which is 94.84 W. The research results can provide a reference for the engineering design and configuration optimization of the vertical shell-and-tube phase change heat exchanger.

Boosting the air conditioning unit performance using phase change material: Impact of system configuration

Boosting the energy efficiency of air conditioning (AC) systems will considerably impact on lowering domestic power consumption. Innovative methods are being developed to enhance AC performance. One promising method involves integrating phase change materials (PCM) with the AC systems. The significant PCM charging period is a primary limitation of coupling AC systems with PCM in the previous research. The current study aims to investigate the impact of coupling an AC unit with various PCM container configurations (e.g., parallel plates, staggered and aligned tubes, and elliptical tubes) on PCM charging and discharging, and AC performance. During the nighttime, the low ambient temperature is charged inside the PCMs. Then, during the daytime, the hot ambient air is cooled by passing through the cold PCM heat exchanger before passing over the unit condenser. A complete dynamic mathematical model for the proposed system is constructed and solved numerically using ANSYS software. Results indicate that applying the cylindrical arrangement lowers the solidification time of the PCM at night by approximately one-third compared to the plate arrangement. Also, raising the inflow air temperature of the air-PCM heat exchanger increases the air temperature difference through the heat exchanger and saving percentage of the AC's power and decreases the PCM's charging and discharging time. For inflow air temperatures of 318.15 K, 313.15 K, and 308.15 K, the maximum average percentage of saved power is around 25 %, 18.7 %, and 12.5 %, respectively for 2 h working and around 8.4 %, 7.2 %, and 6.3 %, respectively for 8 h working of the AC unit. Cylindrical configuration is preferable for daily use of AC systems as the charging process can be achieved through the nighttime.

The effect of edge valency on the load resistance of single-layer reticulated cylindrical shells

The arrangement of members plays a crucial role in determining the resistance of reticulated cylindrical shells, in addition to rise-to-span ratio, cross-section of the members, rigidity of the joints, and support conditions. Although studies on the comparison of shell structures with different configurations were available, the effect of the member arrangement on the performance of reticulated shell structures based on valency of elements was never investigated before. This paper investigates the effect of edge valency on the load resistance of shell structures by studying the behaviour of four cylindrical shell configurations with different edge valencies of vertices and faces. The limit load of the shell structures—with different span-to-rise ratios, length-to-span ratios, support conditions, load patterns, and different magnitudes of initial geometric imperfection—was calculated based on geometrical and material non-linear analyses. The results show that the increase in the edge valency of the vertices increases the overall resistance of single-layer reticulated cylindrical shells with all edges supported. In addition to edge valency, member orientation plays a prominent role in determining the overall resistance of single-layer reticulated shell structures with longitudinal edges supported. The findings on edge valency will help the designer to rearrange the members within a structure without compromising the overall resistance, resulting in an economical design.

Reinforced cement concrete (RCC) shelter and prediction of its blast loads capacity

Reinforced concrete (RC) blast shelters are of momentous importance during warfare. On-the-ground shelters are also used to store chemical explosives, ammunition, and artillery. Functional requirements of blast shelters are entirely different from ordinary residential/commercial or institutional structures and therefore very rich specifications are used for their design and construction. Thus, blast shelters are quite sturdy and robust. Evaluation of the blast resistance of such structures is a topic of research interest, particularly under the circumstances like prevailing in Ukraine, Afghanistan, Iraq, and Syria. These RC structures are subjected to extreme impulsive loadings from blasts and explosions. In the present study, the RC on-the-ground blast-resistant shelter of a novel interior cylindrical configuration consisting of vertical and inclined walls with a flat roof in M40 concrete and Fe500 steel is proposed and its investigation is carried out under two different blast scenarios namely; spherical air detonation (SAD) and hemispherical surface detonation (HSD) using ABAQUS/Explicit code. A parametric study is performed by varying standoff distance, explosive weight, blast height, steel percentage, and concrete strength. The Concrete Damage Plasticity model is implored for nonlinear elastic and inelastic behaviors, degradation of stiffness, and loading rate effect on concrete. Re-bars of steel are idealized with the classical plasticity model following elastic–plastic constitutive law. For SAD and HSD, safe on-the-ground and free-air standoff distances, as well as safe blast pressure, are predicted. Results showed that the proposed RCC shelter can withstand blast loads of 4.98 MPa against SAD and 0.93 MPa against HSD.

Optimization of Composite Cylindrical Shell Structures for Hydrostatic Pressure Loading

Abstract Deep-sea structures will collapse/implode under hydrostatic pressure when the structure dives below an instability threshold, leading to catastrophic failure. To better understand how the layup angle of composite cylindrical shells influences this instability threshold, this work explores how composite cylinders can achieve the highest (optimum) critical collapse pressure under hydrostatic loading conditions. To perform this analysis, a closed-form analytical cylinder buckling solution developed by previous work is used in conjunction with different cylindrical geometrical configurations and composite properties for glass, carbon, and intraply hybrid composite properties for woven and unidirectional structures. The results show that a composite structure's optimum layup configuration is unique to the structure's geometry and material system. However, general trends are observed for these different systems, such as how symmetric and asymmetric constructions place the axial-resistant layers near the neutral plane of the composite system. In addition, both constructions need an increase in shear-resistance layers as the L/D ratio decreases regardless of the material system. Lastly, the analytical approach presented in this work can be used to accurately determine the optimum layup angle for thin composite cylindrical structures that are subjected to external hydrostatic pressure.

Numerical study of three-dimensional flow and aerodynamic characteristics of a cylindrical cavity in rarefied hypersonic flows

Cylindrical cavity configuration frequently appears on the surface of an aerospace vehicle while flow physics of rarefied hypersonic flows over it are not clear yet. This work presents a comprehensive numerical study to reveal flow structures inside the cavity and aerodynamic surface quantities, including the pressure on and heat flux to the surfaces of three-dimensional cylindrical cavities using the DSMC method. The results showed that the traditional cavity flow types based on the classical categorization are not suitable for characterizing rarefied hypersonic flows over cylindrical cavities due to more diverse flow patterns induced by the curved cylindrical sidewall, especially for the cylindrical cavity with a shallow depth. Both the pressure on and heat flux to the striped area near the top lip of downstream curved sidewall are always the strongest due to the violent airflow collision there, which is a depth range of about 0.4 y/H away from the top lip, but those for the cavity floor are usually quite weak because the gas over it moves slowly. With the increase of cavity depth, the weaker pressure on and heat flux to the cavity floor appear because the rising curved sidewall makes it more difficult for freestream to permeate into the cavity, whereas the maximum pressure on and peak heat flux to the downstream curved sidewall seem to be unchanged. The severe rarefaction effect at 90 km make the flow pattern and temperature distribution inside the cavity different from those for 50, 60, and 70 km. As the freestream Mach number is increased from 13.4 to 33.5, the streamline patterns and velocity contours around and inside the cavity only change slightly, consequently leading to similar numerical trends of both the pressure on and heat flow to the cavity surfaces.

Influence of Cylindrical Electrode Configuration on Plasma Parameters in a Sputtering System

In the present work, the effect of the cylindrical configurations of the sputtering device electrodes on the plasma parameters (Debye length, electron temperature, electron density, plasma frequency) is studied. Also, the effect of the argon gas pressure on the discharge properties is examined with gas pressures of (0.08, 0.2, 0.4 and 0.6) Torr. The properties of the plasma are diagnosed by optical emission spectrometry. The spectroscopic method is adopted for examining the atomic spectra of argon emission. The electron temperature is determined by the Boltzmann method. While, the Stark-widening method was employed for calculating the electron number density. The voltage against current curves of the cylindrical sprayer discharges shows the voltage to be nearly constant with slight increase in current. An increase in pressure causes the cathode cascades to compress and the negative glow to become thinner and more luminous. Plasma properties such as electron temperature and Debye length decrease with increasing pressure, while electron number density and plasma frequency increase.

Acoustic Mode Attenuation in Ducts (Using CFD) with Time-Domain Impedance Boundary Condition

In the framework of improving aircraft nacelle design to comply international regulation on aircraft noise, a time-domain impedance boundary condition (TDIBC) based on the oscillo-diffusive representation is implemented in an industrial computational fluid dynamics (CFD) solver under a characteristic formalism, in order to take into account acoustic liner attenuation. A validation of such TDIBC is carried out, first on a two-dimensional benchmark case, then on a more realistic three-dimensional cylindrical configuration, with focus on the acoustic modal content and its attenuation with and without flow. Unsteady Reynolds-averaged Navier–Stokes computations are performed, with the grazing flow being considered laminar. Good agreement is found between the CFD results and the references (computational aeroacoustics results and experiments), with differences in the order of for most cases. The formulation chosen for the TDIBC proved to have no significant impact on numerical stability or computational time.

Retrospective Review of 45 Implanted Human Acellular Dermal Lyophilized Implants to Stabilize Talotarsal Instability, Single Center, Single Surgeon Case Series

A retrospective review of 45 surgeries for repair of Talotarsal instability, with a review of the clinical, radiographic, and biomechanical aspects associated with Talotarsal dislocation and instability. The surgeons utilized an acellular lyophilized human dermal tissue engineered into a cylindrical configuration (stent) to be implanted from lateral to medial via the sinus tarsi. The goal of surgery is to reduce the dislocation, to enhance positioning of the rearfoot and allow regeneration of the Talotarsal ligamentous structures into a more stable configuration. Outcomes found in this review are very promising, none of the implant stents required removal, elimination of the sense of hard stop as seen with other materials in this procedure. Conclusion: excellent outcomes with minimal adverse events, rapid restoration of function in all patients.

Schelkunoff Formulation of the Sommerfeld Integral for the Hertzian Dipole Located in the Vicinity of Cylindrical Structures

AbstractA numerical integration of the Sommerfeld integral is performed using the Schelkunoff formulation for cylindrical media. The Schelkunoff kernel for cylindrical media involves higher order modified Bessel functions with azimuthal summation over higher order modes. As such, the convergence characteristics of the cylindrical integral kernel are strongly dependent on complex linear combinations of higher order Bessel/Hankel/modified Bessel functions, compared to the case of the planar media where only a single Bessel/modified Bessel function of zeroth order is present. Two cylindrical configurations are analyzed using the new formulation, viz. a conducting cylinder and a dielectric‐coated conducting cylinder. The branch‐point singularity in the first configuration is removed using the angular transformation for the Sommerfeld/Schelkunoff formulations. A path deformation technique is used for the second configuration to address the problem of poles and branch‐point singularities on the real axis of integration. The in‐depth analysis of the cylindrical kernels and the integrals with variation in the location of the observation point clearly bring out the relative merits of both formulations for the cylindrical configurations, with the TE/TM coupling for the coated cylinder considered.

Shielding Effectiveness of Ideal Monolayer Graphene in Cylindrical Configurations With the Method of Auxiliary Sources

Electromagnetic shielding is one of the most important branches of Electromagnetic Compatibility. Traditionally, metals were commonly used for shielding materials due to their high conductivity. Recently, however, increasing needs have emerged for lightweight, flexible, optical transparent, non-corrosive shielding materials to be used in flexible electronics, aerospace, and automotive manufacturing. For these reasons, carbon-based materials, such as graphene, have attracted increased attention for shielding applications. The main objective of this work is to evaluate ideal monolayer graphene as a shielding material for cylindrical configurations in the RF/microwave region. The numerical modeling of the involved structures is performed by the Method of Auxiliary Sources (MAS). Particularly, since the standard MAS suffers from numerical difficulties when applied in highly-conductive regions, a modified version of MAS is employed in which the graphene layer is replaced by an Impedance Matrix Boundary Condition (IMBC). The same condition is also applied for the case of a Few Layer Graphene (FLG) shield. The derived numerical results are found to be in excellent agreement with those obtained by FEM-based commercial software.

Performance tests on embedded cooling tube type metal hydride reactor for heating and cooling applications

• Heating and cooling traits of two AB 5 -type metal hydride alloys were investigated. • Heating performances of the alloys were found to be superior compared to cooling. • Peak heating rate of 3.5 kW was accomplished, producing 514 kJ heat within 361 s. • A decentralized heating cum H 2 storage system was suggested based on test results. The present work reports the heating and cooling characteristics of two AB 5 type metal hydride (MH) alloys commercially labelled as A3® and LCC1®. A cylindrical MH reactor configuration comprising 48 Embedded Cooling Tubes (ECT) in a circular pattern and an outer jacket was considered to accomplish the set objectives. Two identical reactors were each filled with 3.4 kg of one of the alloys. The reactor configuration allows MH alloy to be filled in the shell space while the heat transfer fluid (HTF) could flow through the tubes and the outer jacket. A set of parametric investigations was conducted on the aforementioned alloys by varying the operational parameters. During the absorption set of the parametric study, hydrogen supply pressure was varied from 10 bar to 30 bar, and HTF temperature was varied from 15 °C to 35 °C, while during the desorption study, HTF temperature was varied from 5 °C to 25 °C. At the absorption condition of 30 bar and 25 °C, the alloys A3® and LCC1® attained absorption capacity of 1.24 wt.% and 1.38 wt.%, respectively. At this condition, LCC1® was able to generate 514.5 kJ cumulative heat output in 361 s, yielding a maximum heating rate of 3.57 kW. The parametric study revealed that the absorption behaviour of A3® was more sensitive towards changes in supply pressure as well as HTF temperature compared to LCC1®. Compared to heating performance, the cooling performance of both the alloys was lower. Based on the outcomes of the experimental study, it was suggested to utilize LCC1® for decentralized hydrogen storage cum heating applications in the temperature range of 15–35 °C.

Using Cylindrical and Spherical Symmetries in Numerical Simulations of Quasi-Infinite Mechanical Systems

The application of cylindrical and spherical symmetries for numerical studies of many-body problems is presented. It is shown that periodic boundary conditions corresponding to formally cylindrical symmetry allow for reducing the problem of a huge number of interacting particles, minimizing the effect of boundary conditions, and obtaining reasonably correct results from a practical point of view. A physically realizable cylindrical configuration is also studied. The advantages and disadvantages of symmetric realizations are discussed. Finally, spherical symmetry, which naturally realizes a three-dimensional system without boundaries on its two-dimensional surface, is studied. As an example, tectonic dynamics are considered, and interesting patterns resembling real ones are found. It is stressed that perturbations of the axis of planet rotation may be responsible for the formation of such patterns.

Numerical simulations of the effect of spacer filament geometry and orientation on the performance of the reverse osmosis process

Momentum and mass transfer in reverse osmosis membrane modules must be optimized to design efficient and economical designs. The feed spacers are used to improve mixing, to minimize fouling and concentration polarization. This computational study analyses fluid flow, mass transfer, concentration polarization and pressure drop in the feed channel of a reverse osmosis membrane module with different spacer filament geometry (cylindrical, diamond, pentagonal, and triangular), orientation and Reynolds numbers. The computational model solves three-dimensional fluid flow and mass transfer while considering the complex water and solute flux boundary conditions. The cylindrical spacer filaments configurations showed the lowest water flux, followed by pentagonal, diamond, and triangular spacer filaments configurations. The concentration boundary layer thickness was high near the spacer surface due to the stagnant velocity zone. The results indicated that the concentration polarization on the membrane surface increases with a decrease in Reynolds numbers. The channel containing triangular filament spacers gave the maximum water flux and minimum concentration polarization. The spacer configurations with an attack angle of 45° and a transverse angle of 135° showed the highest water flux; however, the pressure drop was also high. The channel containing triangular spacer filament (T1A0) showed the least CP. However, the concentration boundary layer thickness was higher at the bottom side of the channel. The developed model could be useful for predicting the reverse osmosis membrane process performance.

Convergent angles of a tapered implant referred from the root profile of premolars

Background/purposeLimited studies have discussed the convergent profiles regarding tapered implants based on biological considerations. This study analyzed the convergent angles (CAs) of premolar roots and imitated a tapered implant according to the anatomy of tooth roots. Materials and methodsA total of 60 single-rooted premolars were explored by micro-computed tomography. Every individual root was divided into 10 segments corono-apically, and the roots’ buccolingual (BL) and mesiodistal (MD) CAs were measured by sections. To mimic a dental implant, the irregular shape of examined root cross-sections was transformed into a circular shape with equal areas. A biomimetic dental implant (BDI) was reconstructed and its CAs were compared with those of the natural roots’ BL and MD at the examined levels and overall estimation. ResultsIn general, the maxillary and mandibular premolars demonstrated comparable CA patterns. However, significantly different CA patterns of BL, MD, and BDI were developed for both the maxillary and mandibular roots at the examined levels. The BL’s CAs were greater than those CAs measured from the BDI and MD aspects, particularly for the sections at the middle and apical thirds of the roots. For overall CAs, the BDI’s CAs were comparable with the average CAs of the BL and MD for both premolar groups. ConclusionInstead of a cylindrical configuration, the BDI prototype demonstrated a tapered model with a continuous slope. The average CA of BDI was 14°–24°, serving as a biological reference for future tapered implant design and research.

Distributed order fractional diffusion equation with fractional Laplacian in axisymmetric cylindrical configuration

In this paper, we consider the powers (fractional and natural) of the Laplacian operator in axisymmetric cylindrical geometry. We get the fundamental solution of the distributed order time-fractional diffusion equation with this type of fractional Laplacian and the fractional moment of solution is given. Our study is considered in the plane and half space cases and the roles of the Mittag-Leffler and Wright functions in the structures of solutions are also discussed.

Stability characteristics of Walter’s B viscoelastic fluid in a cylindrical configuration with heat transfer

The stability characteristics of the viscous fluid–viscoelastic fluid interface are investigated in a region confined by two rigid cylindrical surfaces. Walter’s B viscoelastic fluid is taken for the analysis and the fluid phases are transferring heat along with mass from one phase to the other. The gravitational acceleration effect is neglected and therefore, the interface is unstable due to surface tension. Using the linear stability analysis, the implicit expression for the critical wave number is derived analytically in terms of associated physical parameters and solved through the Newton–Raphson method. The various plots are made in terms of perturbations growth rate and critical wave number showing the behavior of flow variables. It is found that the instability of the interface decreases if the transfer of heat is increased. Walter’s B viscoelastic fluid interface is more unstable than the equivalent Newtonian fluid interface. The density of Walter’s B fluid resists the perturbation’s growth while viscoelasticity has an inverse effect.