Effect Of Shape Research Articles

An experimental comparative study on condensing supersonic steam jets in water tank: Square, rectangular, and circular cross-sectional shapes

The direct contact condensation phenomenon has gained significant attraction among researchers due to positive aspects such as low driving potential and rapid heat transfer rates in its industrial uses. The present study explores the effect of the cross-sectional shape of converging-diverging on steam-submerged jet condensation behavior. The influence of three cross-sections (circular, square, and rectangular) on steam jet shapes, jet length, average heat transfer coefficient, and maximum expansion ratio were studied. The dimensionless steam jet length for circular, square, and rectangular nozzles has been found in the range of 2.2–7.7, 2.43–8.41, and 2.22–8.35, respectively. The maximum expansion ratio for circular, square, rectangular major axis plane, and rectangular minor axis plane has been found in the range of 1–1.71, 1.14–2.15, 1.22–2.82, and 1.06–1.45. Results show that the maximum expansion ratio and dimensionless jet length rise with steam pressure and water temperature rise. Dimensionless jet length decreases in the order of nozzle with cross-section: square > rectangular > circular. Correlation for dimensional jet length of both circular and non-circular nozzles is presented using the analytical and curve fitting methods. The maximum expansion ratio decreases in order: major axis plane > square > circular > minor axis plane. The average heat transfer coefficient (MW/m2 oC) for circular, square, and rectangular nozzles has been found in the range of 1.16–4.88, 0.89–3.14, and 1.01–3.49. Results show that the average heat transfer coefficient falls with the rise in steam pressure and water temperature. The average heat transfer coefficient decreases in order: circular > rectangular > square. Condensation regime maps are proposed for circular, square, and rectangular nozzles, including diagonal plane effects in square and rectangular nozzle.

Investigation on heat transfer and fluid flow of a plasma arc in a plasma melting furnace: Model validation and parameter effects

Plasma melting furnaces, as an innovative application of thermal plasma, have seen extremely limited numerical studies of their internal plasma arcs, remaining largely in the nascent stages. Due to the complexity of the material composition, the ultra-high currents and temperatures pose great challenges to the numerical calculation of the plasma arc, especially for plasma melting furnaces with an industrial-scale production capacity of 30 t/d. Therefore, this study uses computational fluid dynamics to deeply investigate the fluid flow and heat transfer of the plasma arc in a single-electrode plasma melting furnace operating at a current of 8000 A and a voltage of 170 V. Special attention is given to the impact of the plasma arc on the bath surface, with additional discussions on the effects of electrode gap and cathode bottom shape. The conclusions show that the plasma arc column exhibits a typical bell-shaped profile, and the reduced radial Lorentz force induces an outward expansion of the relevant parameters. The plasma arc achieves a maximum velocity of 2116 m/s and attains the peak temperatures of 19991 K. The heat transfer efficiency from the plasma arc to the bath surface is about 28 %. An innovative evaluation metric for the effective melting region on the bath surface is proposed, and it is currently circular with a radius of 0.525 m. The electrode gap has a minimal effect on the plasma arc. Enlarging the electrode gap can expand the effective melting region, while also bringing about numerous adverse effects. The graphite cathode with the planar bottom exhibits the optimal performance overall, followed by the cambered surface, with the conical surface showing the worst.

Specialization of a new flux-based approach to thermal problems. Numerical study of glass façades of buildings with cast shadows

Uneven temperature distributions in the glass panes of building façades can induce thermal stresses exceeding material strength, a critical condition usually referred to as “thermal shock”. Here, we specialize in architectural glazing a recently-proposed flux-based variational approach to thermal problems, by considering heat exchanges resulting from climatic actions, in particular the variability of environmental temperatures and solar radiation, influenced by the shielding of cast shadows. The finite element implementation is facilitated because the unknown field is the heat displacement, whose time derivative is the heat flux, which is much smoother than the temperature field, on which the classical approach via Fourier’s law is based. A custom in-house-made FEM code is used to determine the effect of size and shape of cast shadows on temperature distribution in monolithic and laminated glass panes, also coupled in insulating glass units. We find that the temperature difference between irradiated and shadowed regions is only mildly influenced by the shape and size of the shadows, but the glass thickness determines the width of the transition zone and, hence, the temperature gradient. Practical rules for the design of glass façades are tentatively proposed.

Modeling effect of rock shape characteristics on run-out distribution of rockfalls

The aim of this study was to analyze and model the effect of rock shapes on the run-out distribution characteristics of rockfalls. To this end, we conducted a parametric study of rockfall simulations using the discrete element method, which is a numerical simulation method capable of directly representing rock shapes. The results indicated a strong correlation between the sphericity of rocks and the run-out distribution characteristics, expressed by two types of sphericity. Furthermore, we developed a regression model that can predict the run-out distribution using these two sphericities and the parameters of the calculation conditions as the explanatory variables. Although there is some room for improvement in terms of the developed regression model, it was confirmed that the relationship between the sphericity of rocks and the run-out distribution characteristics suggests the potential to enhance efficient rockfall risk assessments through numerical analysis.

Capacity planning of wind-photovoltaic-electrolysis-battery system coupling renewable fuel synthesis

The wind-photovoltaic-electrolysis-battery (WPEB) system coupling fuel synthesis by supplying hydrogen and electricity simultaneously can reduce the carbon emission intensity of renewable fuels. However the capacity planning method is rarely reported, this work takes WPEB system coupling renewable methanol synthesis as an example. The business mode and the effect of load profile shape on the capacity configuration are first studied. Then, a two-stage capacity planning method is proposed to improve system performance: At the 1st stage, the capacity configuration is performed using 5 typical load profiles, and the case with minimum net present cost (NPC) is regarded as a pseudo-optimal solution. In the 2nd stage, the wind & solar power profile of the pseudo-optimal solution is standardized and the shape is used to build a variable renewable energy (VRE) flowing load profile as model input, the capacity planning result in the 2nd stage is regarded as the optimal case. The main conclusions are summarized below: (1) The WPEB system has five revenues from selling electricity, methanol, oxygen, CO2 trading in China certified emission reduction (CCER) market and carbon emission allowance (CEA) market. (2) Deep valley load profile obtains the lowest NPC of 2.7656 billion¥ and greatest internal rate of return (IRR) of 6.8843% among 5 typical profiles. (3) The two-stage planning method can further decline the NPC to 2.2018 billion¥ and boost IRR to 10.5583% by employing demand-side flexibility. (4) The sensitivity factors contributing to IRR orders from high to low are methanol price>O2 price>CO2 price of CCER>unmet H2 penalty>electricity price.

Experimental Investigation of Ammonia/Oxygen/Argon Combustion: The Role of Equivalence Ratio and Nozzle Shape in a Constant Volume Combustion Chamber with Sub-chamber

The global rise in carbon emissions presents a rising challenge for current and future generations. In the pursuit of zero carbon emissions, ammonia (NH3) has emerged as an attractive alternative energy source. Ammonia offers a carbon-free fuel option with a higher energy density than liquid hydrogen while maintaining ease of transport and storage. However, ammonia still has its drawbacks, such as a high autoignition temperature, slow burning velocity, and low heating value, that demand further investigation of its combustion characteristics. This experiment was done to study the effect of nozzle shape and equivalence ratio (ɸ) on the combustion of an ammonia/oxygen/argon mixture using a constant volume combustor equipped with a sub-chamber. The fuels were premixed for 10 minutes and conditioned to an initial pressure of 0.2 MPa and an initial mixture temperature of 423 K. The results show that the different nozzle shapes each have their advantages in terms of pressure and jet speed. Overall, the lean mixtures (ɸ0.6 and ɸ0.8) consistently performed better compared to the stoichiometric mixtures (ɸ1.0) in all categories investigated in this study. The round nozzle generates higher pressure, while the special shape nozzle enhances jet speed, highlighting trade-offs between the two.

Orbital Debris Shape Effect Investigations for Mitigating Risk

Orbital Debris Shape Effect Investigations for Mitigating Risk

Effect of the shape of microswimmers and slip boundary conditions on the dynamic characteristics of near-wall microswimmers

Although the interaction between microswimmers and walls during near-wall swimming has been extensively studied, the effect of microswimmer shapes and slip boundary conditions on the dynamic characteristics of near-wall microswimmers has received less attention. In this study, elliptical microswimmer models have been developed with various aspect ratios based on circular microswimmers. The lattice Boltzmann method has been used for the numerical simulation of the dynamic behaviour of microswimmers near walls. Under slip boundary conditions, the escape or capture of microswimmers by the walls is influenced by the swimming Reynolds number (Res), wall slip length (ls) and the aspect ratio (Cab) of a microswimmer. Changes in the Cab value of a microswimmer considerably affect its swimming state, especially for puller-type microswimmers. The tendency of pullers to be captured by the wall increases with increasing Cab. Moreover, changes in ls within the slip boundary condition of a puller can induce a transition in its movement state from a wall oscillation state to a stable sliding state and eventually to a wall lock-up state, a process influenced by the Cab value of the puller. Pusher-type microswimmers show a considerably increased tendency to escape from walls with increasing Cab and no wall lock-up state is observed, which is opposite to the case of pullers. Pushers and pullers show an increased tendency to be captured by the wall with increasing initial swimming angle of the microswimmer. The findings of this study enhance our understanding of the swimming patterns of natural microswimmers near walls and are of substantial importance for the design of artificial microswimmers and microfluidic devices.

Effects of Particle Shape and Surface Structure on the Adsorption Properties of Polystyrene Microplastics

Model spherical polystyrene particles are studied to understand the interactions of microplastics with organic pollutants. Analysis of the experimental results presented in the literature is complicated since researchers use different types and concentrations of particles, durations of tests, etc. In addition, there is little information on the effect of the structure of the surface layer of polystyrene particles on the processes under study, and the question of the effect of the shape of polystyrene particles remains open. Here, we present the first results of a model experiment to study the effect of the shape and structure of the surface layer of polystyrene microspheres and non-spherical particles of 2 to 5 μm in size on the sorption properties in relation to model molecules of rhodamine B as a model organic pollutant. The properties of both the initial model polystyrene particles and the modified ones were studied by optical, transmission electron, and atomic force microscopy, as well as using the Brunauer–Emmett–Teller method (BET). The sorption process was studied by spectrophotometry, and the analysis of sorption curves was carried out using the Langmuir model. It is shown that the shape of polystyrene model particles does not have a significant effect on the sorption capacity. At the same time, the sorption processes of rhodamine B molecules are determined by the structure of the surface layer, which can be changed, for example, by exposing the polystyrene microspheres to N,N′-dimethylformamide.

Interface evolution induced by two successive shocks under diverse reshock conditions

The effects of reshock conditions, including the interface evolution state before reshock and the second shock intensity, on interface instability induced by two successive shocks propagating in the same direction are investigated via shock-tube experiments. It is observed that the reshock promotes the interface instability, and the post-reshock perturbation evolution relates to both the pre-reshock interface evolution state and second shock intensity. For the linear evolution of the twice-shocked interface, existing models perform poorly when either the pre-reshock interface shape effect or the secondary compression effect is pronounced, as current reduction factors fail to accurately describe these effects. Besides, the reshock-induced linear amplitude growth rate shows a non-monotonic dependence on the scaled pre-reshock amplitude, primarily due to the shape effect of the pre-reshock interface. For the post-reshock nonlinear evolution, the model proposed by Zhang & Guo (J. Fluid Mech., vol. 786, 2016, pp. 47–61) offers reasonable predictions when the second shock is weak. However, when the second shock is moderately strong, the model overestimates the bubble growth and underestimates the spike evolution under the influence of the significant secondary compression effect. Furthermore, empirical linear and nonlinear models capable of describing the dependence of the post-reshock evolution on reshock conditions are proposed based on the present experimental results and existing models.

Effect of various notch shape on Lamb wave scattering behaviour in a bent plate

Abstract The application of guided waves to investigate commonly used plate shapes in the aerospace, mechanical and civil industries are plates with bend shapes. This paper investigates the interaction of fundamental Lamb waves with notches in bent plates, commonly found in aerospace, mechanical, and civil engineering applications. These areas are particularly susceptible to failure due to defects such as cracks and notches, which often manifest as semi-circular corrosion patches or 900 notches. The presence of notches affects stress distribution, necessitating thorough analysis to prevent accidents. Accordingly, this paper focus on the interaction of fundamental Lamb waves through two types of notches that could be present inside a bent metal plate section. To explore this, a hybrid numerical framework is employed which combines Semi-Analytical Finite Elements (SAFE) with the Finite Element Method (FEM). A bent plate sections with various notch types is simulated using FEM, while SAFEs facilitate the definition of wave propagation through healthy regions of the plate. The study analyses the scattering behaviour of Lamb waves for different notch configurations and examines both fundamental modes over a specified frequency range. With a change in the interrogation signal parameters, there is a noticeable difference in the sensitivity of scattered waves with different notch types. Formulating a strategy for identifying and locating a notch inside a bent plate may need careful consideration of the important conclusions drawn. Understanding these interactions, aim of the paper is to enhance the integrity assessment of structural components subject to such defects.

Thermal performance analysis of magnetohydrodynamic Al[formula omitted]O[formula omitted]-SiO2-TiO[formula omitted]/water ternary hybrid nanofluid in converging and diverging channels with nanoparticle shape effects

Improving heat transfer in thermal systems is critical to achieving better results in a variety of systems. The study aims to investigate the laminar flow dynamics of Al2O3-SiO2-TiO2/water hybrid nanofluids, emphasizing how the channel geometry affects the velocity, temperature distribution, and heat transfer efficiency. This understanding is crucial for optimizing industrial processes, such as cooling systems and heat exchangers. Effects of various nanoparticle shapes, joule heating, viscous dissipation, thermal radiation, and heat source/sink on the system’s behavior are evaluated. Governing partial differential equations are transformed into ordinary differential equations using similarity variables and are solved semi-analytically via the homotopy analysis method. As the Hartmann number increases from 1 to 7, the heat transfer rate rises from 0.02% to 0.9%. When the radiation parameter and Eckert number are varied from 0.05 to 0.2, the heat transfer rate increases significantly, from 1.2% to 4.86% and 3.43% to 13.73%, respectively. Heat transfer rate increased by 16.28% with heat source (Q=2) and decreased by -16.12% with heat sink (Q=−2). Platelet-shaped nanoparticles demonstrate lower skin friction in divergent channels, whereas spherical nanoparticles exhibit higher skin friction; this trend reverses in convergent channels. Suspensions of nanoparticles with a 5% volume fraction achieve heat transfer rates of 1.88%, 4.07%, 10.54%, 19.20%, and 8.74% for spheres, bricks, cylinders, platelets, and blades, respectively. The study reveals that Al2O3/H2O, Al2O3-TiO2/H2O, and Al2O3-SiO2-TiO2/H2O nanofluids have the best heat transfer rates for mono nanofluid, hybrid nanofluid, and ternary hybrid nanofluid by 15.24%, 19.92%, and 19.20%, respectively. Finally, multiple linear regression is employed to analyze the impact of relevant parameters on heat transfer rate and skin friction.

Effect of Particle Shape on Cyclic Shear Behavior of Granular Mixtures–Geogrid Interface

The cyclic shear stiffness and damping ratio of angular and round particle geogrid interfaces is of much concern in reinforcement structure seismic analysis. In this study, various component percentages of crushed limestone and spherical granular medium mixtures were used to investigate the role of particle regularity in static and cyclic direct shear tests. The test results revealed that an increase in the proportion of round particles decreased cyclic shear strength and volume change. The phenomenon of shear softening was observed with a high amplitude of shear displacement when the proportion of round particles was increased in the mixture. As the percentage of round particles increased, the maximum interface shear stiffness decreased significantly from, 39.69 to 28.28 MPa/m, but a reverse trend in the maximum damping ratio was observed, from 0.308 to 0.37. The effect of cyclic shear history and proportion of round particles on interface strength parameters was also analyzed. A linear regression model was fitted to the data for quantifying the relationship between the proportion of round particles and friction angle. The results suggest that different percentages of round and angular particles can produce varying degrees of particle interlock between aggregate and geogrid, influencing the macro-mechanical behavior of the reinforced soil interface.

Macroscopic effects of intraparticle fracture, grain topology and shape on vehicle dynamics and mobility over gravel road beds

Macroscopic effects of intraparticle fracture, grain topology and shape on vehicle dynamics and mobility over gravel road beds

Effects of anode geometry on DC magnetron sputtering of copper oxide films deposition

Abstract Effects of anode shape are examined in a custom-made DC magnetron sputtering system. Polycrystalline copper-oxide (CuO) films are deposited using wedge, ring and disc shaped anodes. Current–voltage (I-V) characteristics of the discharge were fitted with models of plasma discharge. Above 700 V a notable rise in average plasma impedance, from approximately 2kΩ to 7kΩ was observed. Scanning electron microscope (SEM) images reveal uniform and porous film growth. The deposition increased significantly with increasing the anode surface area due to decrease in gas density in cathode sheath. For all the anode shapes tested, the deposition rates were higher in magnetron sputtering compared to DC sputtering mode. X-ray diffraction (XRD) of the films deposited with the disk anode revealed polycrystalline films with predominant CuO phase. With increasing sputtering power, average crystallite size vary from 11 nm to 21 nm, dislocation density vary from approximately 8.4×〖10〗^(-3) nm-2 to 2.3×〖10〗^(-3) nm-2 and micro strain from approximately 3.3×〖10〗^(-3) to 1.7×〖10〗^(-3). This indicate that higher sputtering at higher powers produce higher quality films. Atomic force microscopy revealed that the rms roughness of the samples is about 4 nm.

Ballistic characteristics of ceramic core sandwich structures

The ceramic core sandwich structure (CCSS) is a lightweight material with advantages of high anti-ballistic impact performance, high energy absorption and high specific strength. The ballistic performances of the CCSS with metal face plates hit vertically by projectiles with the nose shapes of conical, flat, and hemispherical are studied analytically and numerically in this paper. Based on the principle of energy conservation, an analytical model of ballistic characteristics of the sandwich ceramic core structure is developed. Numerical calculations are conducted, and the numerical model has been verified by experimental results from references by others. In addition, the analytical results agree well with finite element results. The effects of shape of projectile head, the thickness ratio of three plates of CCSS, and the ratio of shear strength of ceramic core to yield strength of metal face plates on the ballistic characteristics of the CCSS are discussed. It is shown that the conical-nosed projectile achieved the highest ballistic limit velocity (BLV) and the sharper nose increases the normal stress at the impact area thereby enhancing the BLV. The thickness of the ceramic core significantly influences the resistance of the CCSS and the thicker ceramic core enhances the ability of CCSS to absorb kinetic energy from the projectile. Furthermore, an appropriate increase in the yield strength of face plates can enhance the anti-ballistic impact performance of the CCSS. These insights have practical implications for the design of protective systems in military and civilian applications, where optimizing materials for impact resistance is crucial.

Tetrahedral shape and Lambda impurity effect in $^{80}$Zr with a multidimensionally constrained relativistic Hartree-Bogoliubov model

Abstract This study investigates the tetrahedral structure in $^{80}$Zr and Lambda ($\Lambda$) impurity effect in $^{81}_{~\Lambda}$Zr using the multidimensionally constrained relativistic Hartree-Bogoliubov model.
 The ground states of both $^{80}$Zr and $^{81}_{~\Lambda}$Zr exhibit a tetrahedral configuration, accompanied by prolate and axial-octupole shape isomers. 
 Our calculations reveal there are changes in the deformation parameters $\beta_{20}$, $\beta_{30}$ and $\beta_{32}$ upon $\Lambda$ binding to $^{80}$Zr, except for $\beta_{32}$ when $\Lambda$ occupies $p$-orbits. 
 Compared to the two shape isomers, the $\Lambda$ particle exhibits weaker binding energy in the tetrahedral state when occupying the $1/2^+[000](\Lambda_s)$ or $1/2^-[110]$ single-particle states. In contrast, the strongest binding occurs for the $\Lambda$ particle in the $1/2^-[101]$ state with tetrahedral shape. A large $\Lambda$ separation energy may not necessarily correlate with a significant overlap between the density distributions of the $\Lambda$ particle and the nuclear core, particularly for tetrahedral hypernuclei.

Creep evaluation for fiber-reinforced composites with hybrid fibers: From quantifying fiber anchorage effect to homogenization model

A general micromechanical creep model for fiber-reinforced composites with multi-type hybrid fibers is proposed from quantifying the fiber anchorage effects. An average Eshelby tensor-based homogenization method is employed to calculate the effective creep of composites with realistic-shaped (straight, hooked, and wavy) fibers. A fiber anchorage zone is introduced to depict the anchorage effects of fibers and its parameters are obtained by back analysis. The micromechanical model and fiber anchorage zones are validated by comparing with extensive creep experimental data and finite element simulation. According to the micromechanical model, the effects of fiber shapes, types, direction, anchorage zone, and fiber doping on the creep of composites are systematically explored. The results show fiber shapes and types have obvious effects on composites creep. Fiber deflection angle leads to a monotonous increase in creep. The creep with fiber doping is between the two cases without fiber doping. It indicates that the creep of fiber-reinforced composites can be tailored via proper design for these factors.

Numerical and experimental investigations on the effect of skeleton shapes and heat transfer directions on water freezing in porous media

Incorporating porous skeletons into PCMs is an effective strategy for enhancing their thermal properties. However, this approach increases the complexity of the heat transfer process and poses a challenge to accurate modeling. This study investigates the water freezing process in porous skeletons with various shapes and heat transfer directions through experiments and numerical simulations. The model employs the hybrid finite element method with mesh adaptation to optimize numerical solutions. The experimental and simulation results are in good agreement, which validates the accuracy of this model. The study aims to reveal the evolution mechanisms of the phase interface, temperature field, and freezing rate of water in various porous skeletons, enhancing the theoretical foundation and offering insights for practical applications. Results show that the square steel skeleton exhibits the highest freezing rate among the tested skeleton shapes, while the rhombus resin skeleton demonstrates the slowest. Furthermore, the square skeleton shows the smallest interface deflection before and after the pores, while the rhombus skeleton presents the largest. Additionally, vertical heat transfer from bottom to top increases the freezing rate by 38.97% compared to horizontal heat transfer from left to right.

Size and shape dependence of hydrogen-induced phase transformation and sorption hysteresis in palladium nanoparticles

Abstract Phase transitions of metals in hydrogen environments are critically important for applications in energy storage, catalysis, and sensing. Nanostructured metallic particles can lead to faster charging and discharging kinetics, increased lifespan, and enhanced catalytic activities. However, establishing a direct causal link between nanoparticle structure and function remains challenging. In this work, we establish a computational framework to explore the atomic configuration of a metal-hydrogen (M-H) system when in equilibrium with a H environment. This approach combines Diffusive Molecular Dynamics with an iteration strategy, aiming to minimize the system's free energy and ensure uniform chemical potential across the system that matches that of the H environment. Applying this framework, we investigate H chemical potential-composition isotherms during the hydrogenation and dehydrogenation of palladium nanoparticles, ranging in size from $3.9$ nm to $15.6$ nm and featuring various shapes including cube, rhombic dodecahedron, octahedron, and sphere. Our findings reveal an abrupt phase transformation in all examined particles during both H loading and unloading processes, accompanied by a distinct hysteresis gap between absorption and desorption chemical potentials. Notably, as particle size increases, absorption chemical potential rises while desorption chemical potential declines, consequently widening the hysteresis gap across all shapes. Regarding shape effects, we observe that, at a given size, cubic particles exhibit the lowest absorption chemical potentials during H loading, whereas octahedral particles demonstrate the highest. Moreover, octahedral particles also exhibit the highest desorption chemical potentials during H unloading. These size and shape effects are elucidated by statistics of atomic volumetric strains resulting from specific facet orientations and inhomogeneous H distributions. Prior to phase transformation in absorption, a H-rich surface shell induces lattice expansion in the H-poor core, while before phase transformation in desorption, surface stress promotes lattice compression in the H-rich core. The magnitude of the volumetric strains correlates well with the size and shape dependence, underlining their pivotal role in the observed phenomena.