Influence Of Geometrical Characteristics Research Articles

Numerical Analysis of Geometry Influence on Heat Transfer in a Slotted Fin and Tube Heat Exchanger

The influence of geometric characteristics on thermal and hydraulic performance of slotted fin and tube heat exchangers has been numerically analyzed. Numerical model of a slotted fin and tube heat exchanger has been developed and validated using the experimental data. Considered geometric parameters were fin pitch, fin thickness, and slots height. Air inlet velocities ranged from 1 to 4 m/s, corresponding to Reynolds numbers ranging from 558 to 2234. Total of 56 different cases have been numerically solved and results have been presented in terms of exchanged heat flux, average air outlet temperature, and pressure drop along the heat exchanger. The analysis showed that for the considered operating conditions, an increase in fin pitch results in a slightly higher exchanged heat flux and significant reduction of pressure drop, but after certain value further increase in fin pitch does not result in a noticeable augmentation of exchanged heat flux. Additionally, higher exchanged heat flux was achieved for greater fin thicknesses but causing higher air-side pressure drop. Finally, it was found that the slots height for which a heat exchanger will achieve the highest exchanged heat flux depends on air inlet velocity, however the pressure drop was lower in cases of smaller slots heights.

Mathematical modeling of forced oscillations of manometric tubular springs

Difficult working conditions, as well as vibrations of technological process units and unstable load intensity impose high demands on overpressure monitoring devices that ensure the required measurement accuracy and trouble-free operation of equipment. The use of pressure gauges today is a mandatory requirement for monitoring overpressure. The main type of pressure gauges uses manometric tubular springs (MTP) as elastic sensing elements. Therefore, the issue of calculating the motion of the MTP under the influence of external variable loads, in particular variable internal pressure, is relevant. Issues related to the influence of internal pressure pulsations and external periodically changing external forces remain unexplored. For successful operation, the strength and frequency characteristics of vibrations of tubular springs were previously investigated, the effects of cross-sectional shapes and basic geometric dimensions on their vibration characteristics were considered, and the process of vibration damping by liquid was analyzed. The paper presents a mathematical model of forced oscillations of the MTP based on Lagrange equations of the second kind. The MTP is considered as a mechanical system with two degrees of freedom, that is, defined by two generalized coordinates. They are a relative change in the main angle of the tube and an increase in the small semi-axis of the cross section. The model allows us to determine the nature of the movement of the MTP under the influence of periodically changing internal pressure. To implement it, a program has been developed in MATLAB, which makes it possible to determine the required characteristics of pressure monitoring devices that exclude the possibility of resonance. With the help of the developed program, the influence of geometric characteristics and internal pressure pulsations on the movements of the free end of the MTP is estimated. The presented model can be successfully used for dynamic calculations of manometric tubes, since it is a classical approach to solving problems of vibrations of mechanical systems. In addition, it will allow you to calculate the parameters of tubular elastic elements used in various mechanisms as power elements.

Influence of Geometric Characteristics of Fiber Reinforced Polymer (FRP)on Stresses at the FRP-Concrete Interface

Influence of Geometric Characteristics of Fiber Reinforced Polymer (FRP)on Stresses at the FRP-Concrete Interface

SiamMFC: Visual Object Tracking Based on Mainfold Full Convolution Siamese Network.

Visual tracking task is divided into classification and regression tasks, and manifold features are introduced to improve the performance of the tracker. Although the previous anchor-based tracker has achieved superior tracking performance, the anchor-based tracker not only needs to set parameters manually but also ignores the influence of the geometric characteristics of the object on the tracker performance. In this paper, we propose a novel Siamese network framework with ResNet50 as the backbone, which is an anchor-free tracker based on manifold features. The network design is simple and easy to understand, which not only considers the influence of geometric features on the target tracking performance but also reduces the calculation of parameters and improves the target tracking performance. In the experiment, we compared our tracker with the most advanced public benchmarks and obtained a state-of-the-art performance.

A Coupled Eulerian-Lagrangian Simulation and Tool Optimization for Belt Punching Process with a Single Cutting Edge.

The objective of this paper is to analyze the belt punching process with the use of a single cutting edge and discuss the influence of geometrical features of the piercing punch on the perforation force. Two basic shapes of the piercing punch with a single cutting edge were tested: tools with the blade pointing inside or pointing outside. The analytical models of the stress distribution in the shearing cross sections were derived for both punches. The presented model, along with the series of empirical tests and Coupled Eulerian-Lagrangian simulation, was used for finding the effective geometry of the piercing punch with a single cutting edge for the belt perforation. The geometrical parameters taken into consideration for the tool optimization were the following: angle of the blade, thickness of the wall and diameter of the piercing punch cutting edge. The obtained results show that changing these parameters has a significant influence on the perforation force necessary to execute the machining process and affects the quality of the holes in the perforated belts. The most important geometrical features of the hollow sharpened punch are the angle and the direction of the blade, which change the force distribution and, as a result, the mechanics of the process.

Monitoring and Analysis of Stress Distribution of the Interaction between Rock and Backfill and the Influence of Geometric Features of the Backfill Boundary

Backfill mining methods are widely used in metal mines. The boundary part of the backfill has a direct effect on the local stability in mining engineering. The distribution of stress on the boundary part of the backfill and surrounding rock had their own features. To study the characteristics of stress distribution of backfill and surrounding rock on the boundary part, we conducted a field investigation, field monitoring, and numerical simulation. According to the underground monitoring, the overall characteristics of the boundary part of the backfill were that the accumulated horizontal stress was larger than the accumulated vertical stress on the deep sublevel and the accumulated horizontal stress was smaller on the shallow sublevel. On the contact zone (i.e., the boundary part), the stress of the surrounding rock was larger than the stress of the backfill. Combined with the numerical model analysis, we determined that the geometric features of the backfill boundary had an influence on the stress distribution of stress. The multistep boundary helped the integrity of the contact zone and local stability in deep mining.

The Potential of the Reed as a Regenerative Building Material—Characterisation of Its Durability, Physical, and Thermal Performances

Knowing the properties of vernacular materials is crucial to heritage conservation and to develop innovative solutions. Reed, considered to be a carbon-neutral and a carbon dioxide sink material, has been used for centuries for diverse uses. Its high availability and properties made it a popular building material, including in Portuguese vernacular architecture. An experimental investigation was conducted to evaluate the physical performance, thermal performance, and durability of the reed found in Portugal since the characterisation of this material was not found in previous studies. The influence of geometric characteristics and the presence of nodes on these properties were also analysed, and the results showed that they are irrelevant. The studied reeds were found to have an adequate thermal performance to be used as thermal insulation. Their thermal resistance (1.8 m2·°C/W) and thermal conductivity (0.06 W/m·°C) are under the requirements defined by Portuguese regulations on thermal insulation materials. Overall, the physical characteristics (moisture content, density, and retraction) are compatible to its use in the construction. Concerning durability, there was only a trend for mould growth in particular environments. The results provide valuable data to be considered in the development of new construction products based on this natural and renewable material. Additionally, considering the studied samples, the reed found in Portugal has characteristics suitable for use as a building material, especially as a thermal insulation material.

Особенности фазовых превращений растворов полимеров в деформируемых пористых матрицах

The influence of geometric characteristics (size and shape) of a pore on phase equilibria in stratifying polymer solutions within porous matrices have been simulated by means of equilibrium chemical thermodynamics. Using the example of liquid stratifying polybutadiene-polystyrene mixtures, we have shown that a strain of a matrix which influences on pore shapes, determines mutual solubilities of components within a pore, equilibrium volume ratios of co-existing phases and their thermodynamic stability. High strains of a matrix lead to suppressing the stratification while every composition up to the equimolar one becomes thermodynamically stable.

Influence of Geometric Characteristics of the Bomb-Fluger System on its Dynamics

Influence of Geometric Characteristics of the Bomb-Fluger System on its Dynamics

Numerical studies of the influence of various geometrical features of a multispiked connecting scaffold prototype on mechanical stresses in peri-implant bone

The multispiked connecting scaffold (MSC-scaffold) prototype is an essential innovation in the fixation of components of resurfacing arthroplasty (RA) endoprostheses, providing their entirely non-cemented and bone-tissue-preserving fixation in peri-articular bone. An FE study is proposed to evaluate the influence of geometrical features of the MSC-scaffold on the transfer of mechanical load in peri-implant bone. For this study, an FE model of Ti-Alloy MSC-scaffold prototype embedded in a bilinear elastic, transversely isotropic bone material was built. For the compressive load on the MSC-scaffold, maps of Huber-Mises-Hencky (HMH) stress in peri-implant bone were determined. The influence of the distance between the bases of neighbouring spikes, the apex angle of spikes, and the height of the spherical cup of spikes of the MSC-scaffold were analysed. It was found that the changes in the distance between the bases of neighbouring spikes from 0.2 to 0.5 mm cause the HMH stress to increase in bone material by 32%. The changes of the apex angle of spikes from 2° to 4° decrease the HMH stress in bone material by 39%. The changes of height of the spherical cup of spikes from 0 to 0.12 mm increase the HMH stress in bone material by 24%. In conclusion, the spikes’ apex angle and the distance between the bases of spikes of the MSC-scaffold are the key geometrical features determining the appropriate MSC-scaffold prototype design. The built FE model was found to be useful in bioengineering design of the novel fixation system for RA endoprostheses by means of the MSC-scaffold.

Effect of stenosis eccentricity on the functionality of coronary bifurcation lesions-a numerical study.

Interventional cardiologists still rely heavily on angiography for the evaluation of coronary lesion severity, despite its poor correlation with the presence of ischemia. In order to improve the accuracy of the current diagnostic procedures, an understanding of the relative influence of geometric characteristics on the induction of ischemia is required. This idea is especially important for coronary bifurcation lesions (CBLs), whose treatment is complex and is associated with high rates of peri- and post-procedural clinical events. Overall, it is unclear which geometric and morphological parameters of CBLs influence the onset of ischemia. More specifically, the effect of stenosis eccentricity is unknown. Computational fluid dynamic simulations, under a geometric multiscale framework, were executed for seven CBL configurations within the left main coronary artery bifurcation. Both concentric and eccentric stenosis profiles of mild to severe constriction were considered. By using a geometric multiscale framework, the fractional flow reserve, which is the gold-standard clinical diagnostic index, could be calculated and was compared between the eccentric and concentric profiles for each case. The results suggested that for configurations where the supplying vessel is stenosed, eccentricity could have a notable effect on and therefore be an important factor that influences configuration functionality.

Ferromagnetic model on the Apollonian packing.

This work investigates the influence of geometrical features of the Apollonian packing (AP) on the behavior of magnetic models. The proposed model differs from previous investigations on the Apollonian network (AN), where the magnetic coupling constants depend only on the properties of the network structure defined by the packing, but not on quantitative aspects of its geometry. In opposition to the exact scale invariance observed in the AN, the circle's sizes in the AP are scaled by different factors when one goes from one generation to the next, requiring a different approach for the evaluation of the model's properties. If the nearest-neighbors coupling constants are defined by J_{i,j}∼1/(r_{i}+r_{j})^{α}, where r_{i} indicates the radius of the circle i containing the node i, the results for the correlation length ξ indicate that the model's behavior depend on α. In the thermodynamic limit, the uniform model (α=0) is characterized by ξ→∞ for all T>0. Our results indicate that, on increasing α, the system changes to an uncorrelated pattern, with finite ξ at all T>0, at a value α_{c}≃0.743. For any fixed value of α, no finite temperature singularity in the specific heat is observed, indicating that changes in the magnetic ordering occur only when α is changed. This is corroborated by the results for the magnetization and magnetic susceptibility.

Reliability of analytical models for the prediction of out-of-plane capacity of masonry infills

The out-of-plane response of infill walls has recently gained a growing attention and has been recognised fundamental in the damage assessment of reinforced concrete and steel framed buildings subjected to seismic loads. The observation of damage after earthquakes highlighted that out-of-plane collapse of masonry infills may occur even during seismic events of low or moderate intensity, causing both casualty risks and unfavourable situations affecting the overall structural response. Even though studies concerning the out-of-plane behaviour of infills are not as many as those focused on the in-plane response, in the last decades, a substantial number of researches have been carried out on the out-of-plane behaviour of infills. In this study, the out-of-plane response is investigated considering different aspects. First, damages observed after past earthquakes are examined, with the aim of identifying the main parameters involved and the most critical configurations. Secondly, the response recorded in about 150 experimental tests is deeply examined, focusing on the influence of geometrical characteristics, boundary conditions, prior in-plane damage, presence of reinforcing elements and openings. Finally, different theoretical capacity models and code provisions are discussed and compared, giving specific attention to those based on the arching theory. The reliability of some of these models is herein tested with reference to experimental results. The comparison between analytically predicted and experimental values allows to appreciate the extent of approximation of such methods.

Effect of non-conformal gold deposition on SERS related plasmonic effects.

Recently, a comprehensive three dimensional computational model based on rigorous coupled wave analysis (RCWA) has been developed to investigate the properties of surface plasmons resident on metal coated arrays of inverted pyramidal pits used for SERS sensing applications in the form of 'klarite'. This simulation tool allows the identification of a variety of dispersive features including propagating and localized surface plasmons as well as simple diffraction relating to the influence of geometrical features. In this paper, we investigate the influence of non-conformality of the gold coating over the internal surfaces of the inverted pyramidal pits on plasmon dispersion. Modeling reveals very strong changes in plasmon behavior as a function of gold layer conformality. Dependent upon conformality of the gold coating we find that the nano-textured metallic surface can behave either as an efficient broadband mirror-like reflector or as an efficient broadband, wide angle absorber at infrared wavelengths. Creation of a broadband wide angle absorbing surface such as this has important implications for photovoltaic cells. For sensing applications, understanding the effect of metal layer conformality on plasmon dispersion gives clear insight into how to further improve the SERS enhancement factor.

Influence of Geometric Characteristics of Canal on Precipitating Capacity of Separator

Designed mathematic model allows calculating trajectories of spherical non-deformable particles movement in the flow of viscous non-burnt liquid in the flat canal of complex geometry. According to the results of calculations graphs of dependence of precipitating particles share on their diameter and degree of curvature of the researched canal have been built.

On the Influence of Geometrical Features and Wind Direction over an Urban Canyon Applying a FEM Analysis

The urban areas discomfort is related to the increase of local temperatures due to the geometrical characteristics and thermal properties of the built environment. This study shows the results of a FEM analysis through which a urban canyon geometry has been modelled. A 3D domain has been considered taking into account three different wind directions and to geometrical parameters variation, such as the aspect ratio (Height- Width) and the urban canyon length.

Influence of geometrical characteristics of sidewall-type multiple aneurysms on hemodynamic factors

Multiple aneurysms occur rarely and have not been well investigated. The purpose of this study is to verify whether high rupture risk of multiple aneurysms is due to the interaction between multiple aneurysms’ geometrical characteristics. The following geometrical characteristics were varied in an idealized sidewall-type model: aneurysm a1’s dome-neck length ( S), size ratio, inflow angle ( α), distance between two aneurysms ( D), and the parent vessel’s angle ( θ). We varied the parent blood vessel and aneurysm sac a1’s geometrical characteristics to analyze their hemodynamic influence on aneurysm a2. By comparing the influence on aneurysm a2, we found that parent blood vessel geometrical characteristics such as the distance between aneurysms ( D) and the parent vessel’s angle ( θ) were the most hemodynamically influential characteristics examined. The impact of varying the aneurysm’s geometrical characteristics such as dome-neck length ( S), size ratio, and inflow angle ( α) was not obvious. The reason for the higher rupture rate of multiple aneurysms is not due to interactions between the aneurysm sacs but due to factors of each individual aneurysm.

The influence of geometrical characteristics on the photocatalytic activity of TiO2 nanotube arrays for degradation of refractory organic pollutants in wastewater.

The effects of geometrical characteristics such as surface area (SA) and porosity of TiO2 nanotube arrays (TNAs) on its photocatalytic activity were investigated by applying variable voltages and reaction times for the anodization of Ti substrates. While larger SA of nanotubes was observed under higher applied potential, the porosity of TNAs decreased by increasing anodizing voltage. Under applied potential of 80 V, the SA of TNAs increased from 0.164 to 0.471 m2/g as anodization time increased from 1 to 5 hours, respectively. However, no significant effect on the porosity of TNAs was observed. On the other hand, both SA and porosity of TNAs, synthesized at 60 V, increased by augmenting the anodization time from 1 to 3 hours. But further increasing of anodization time to 5 hours resulted in a decreased SA of TNAs with no effect on their porosity. Accordingly, the TNAs with SA of 0.368 m2/g and porosity of 47% showed the highest photocatalytic activity for degradation of 4-chlorobenzoic acid (4CBA). Finally, the degradation of refractory model compounds such as carbamazepine and bisphenol-A was tested and more than 50% of both compounds could be degraded under UV-A irradiation (λmax=365 nm).

Multi-objective thermal analysis of a thermoelectric device: Influence of geometric features on device characteristics

Proper assessment of geometric features of a thermoelectric generator is important to design devices with improved performance features such as high efficiency and output power. In the present study, three the-state-of-the-art multi-objective evolutionary algorithms, namely, NSGA-II (Non-dominated Sorting Genetic Algorithm-II), GDE3 (Generalized Differential Evolution generation 3), and SMPSO (Speed-constrained Multi-objective Particle Swarm Optimization) are used to optimize the geometric features of a thermoelectric generator for improved efficiency and output power while incorporating different operating conditions. The parameters assessing geometric features of the device include shape factor and pin length size while operating parameters include temperature ratio and external load parameter. Thermal analysis incorporating geometric features and operating parameters of the device is introduced prior to the optimization study. The findings are validated against the results reported in the open literature. It is found that shape factor and pin length size have significant effect on the device performance. Increasing shape factor (S ≤ 0.5) first increases thermal efficiency to reach its maximum (∼17%), and furthermore, an increase in shape factor (S ≥ 0.5) lowers thermal efficiency significantly (∼8%). Device output power behaves similar to that of efficiency for small increment in shape factor, provided that further increase in shape factor does not influence output power of the device. A unique design configuration is present for a fixed operating condition of a thermoelectric generator; in which case, thermal efficiency and output power of the device attain high values.

Experimental research of motor-and-tractor starters’ wear resistance

Regularities of influence of geometric characteristics and working units material on wear resistance of different kinds of eccentric freewheel clutches for motor-and-tractor starter drives have been experimentally determined.