Geometry Configuration Research Articles

Study on Influence of Core Structure on Catalytic Converter Performance Using CFD

In recent years, as the automotive industry is growing, one of the major hope for future vehicles is to meet emissions regulations. Automobiles pollute the air, and clean-air laws have made Catalytic Converters a legal requirement because they convert harmful pollutants from an engine's exhaust into cleaner emissions. The device works with the principle of a catalyst, something that causes or speeds up a chemical reaction without itself being changed. But the presence of a catalytic converter increases the exhaust back pressure which has an indirect effect on the engine efficiency ie engine efficiency decreases, thus increasing fuel consumption. The performance of a catalytic converter is substantially affected by the flow distribution inside the substrate, a uniform flow distribution can increase its efficiency, lower the pressure drop and optimize engine performance. The flow distribution in a catalytic converter assembly 15 is governed by the geometry configurations of the inlet and outlet cone section, the substrate, and exhaust gas compositions, and therefore a better design of the catalytic converter is very important. This Project deals with the fundamental understanding and study of complex processes taking place involving fluid flow, pressure, and velocity profiles in the catalytic converter using ANSYS WORKBENCH 2022 R1. The main objective of our analysis is to determine the most effective and optimum design of a Catalytic Converter

Study of six coordinated cobalt(III) oxophlorin with different axial ligands: Optimization of geometry and determining of energy and electronic configuration at various spin states by employing of B3LYP, BV86P and M06-2X methods

The six coordinated CoIIIoxophlorin have been studied with imidazole, pyridine and t-butylcyanide as axial ligands using B3LYP, BV86P and MO6-2X methods. Conversion between two isomers [(L)2CoIII(PO)][Formula: see text] and [(L)2CoIII(PO)][Formula: see text] can be occurred at various spin multiplicities, namely singlet, triplet and quintet states. L is employed to show axial ligand namely, imidazole or pyridine. London forces have a basic role in the stability of the mentioned complexes due to non-specific solvent effects. The latter fact has been obtained using the PCM model. Also, it is specified that minimum geometries have not been obtained for some parallel or perpendicular six-coordinated complexes with special axial ligands at a finite spin state. The B3LYP method indicates that one and three [Formula: see text]-electron can be found on the Co atom in every optimized complex at triplet and quintet spin states, respectively. Also, another [Formula: see text]-electron is placed on the ring of oxophlorin. This fact is obtained for different isomers of [(IM2(CoIII(PO)] and [(Py)2CoIII(PO)] at triplet and quintet spin states, while these complexes are optimized using B3LYP. Besides, results obtained from B3LYP show that the most stable state for six coordinated CoIIIoxophlorin with any axial ligand is the singlet state. Based on crystal field theory and molecular orbital theory, electron configuration and hybridization of cobalt in [(IM)2CoIII(PO)] at singlet state can be written as t2g6 eg0 and sp3d2, respectively. Former electronic configuration indicates a strong field with low spin for d orbitals of cobalt, and latter hybridization is expected for a metal with a coordination number of 6 in a complex with Oh symmetry. The results obtained are completely satisfied by NBO analysis.

3D Diffusion of Water in Melt Inclusion‐Bearing Olivine Phenocrysts

AbstractOlivine‐hosted melt inclusions are an important archive of pre‐eruptive processes such as magma storage, mixing and subsequent ascent through the crust. However, this record can be modified by post‐entrapment diffusion of H+ through the olivine lattice. Existing studies often use spherical or 1D models to track melt inclusion dehydration that fail to account for complexities in geometry, diffusive anisotropy and sectioning effects. Here we develop a finite element 3D multiphase diffusion model for the dehydration of olivine‐hosted melt inclusions that includes natural crystal geometries and multiple melt inclusions. We use our 3D model to test the reliability of simplified analytical and numerical models (1D and 2D) using magma ascent conditions from the 1977 eruption of Seguam volcano, Alaska. We find that 1D models underestimate melt inclusion water loss, typically by ∼30%, and thus underestimate magma decompression rates, by up to a factor of 5, when compared to the 3D models. An anisotropic analytical solution that we present performs well and recovers decompression rates within a factor of 2, in the situations in which it is valid. 3D models that include multiple melt inclusions show that inclusions can shield each other and reduce the amount of water loss upon ascent. This shielding effect depends on decompression rate, melt inclusion size, and crystallographic direction. Our modeling approach shows that factors such as 3D crystal geometry and melt inclusion configuration can play an important role in constraining accurate decompression rates and recovering water contents in natural magmatic systems.

On the Effect of 3D Wave Propagation on 2D Regional‐Scale Velocity Model Building

AbstractActive seismic surveys are routinely employed by academia to study geological structure of the crust and upper mantle. Wavefields generated during these surveys are sampled at the receiver locations, but the wave‐paths traveled from a source to a sensor remains unknown. Although seismic acquisition layouts designed to investigate complex crustal‐scale environments are often two‐dimensional, the seismogram recorded at the receiver location represents information gathered along the three‐dimensional wavepaths that might offset from the 2D source/receiver profile along its transverse direction. This so‐called 3D‐effect distorts the results of 2D seismic imaging, which is unable to handle the out‐of‐plane propagation. Despite the numerous 2D seismic imaging case studies, the assessment of this issue is often overlooked. However, the problem exists ‐ especially for crustal‐scale profiles, where seismic energy propagates over distances of hundreds of kilometers and probes different crustal units. In this work we investigate the impact of 3D‐effect on the results of 2D velocity model building from the academic ocean‐bottom seismometer data. We show with polarization analysis how the 3D‐effect can manifest itself in the data domain. Using various scenarios of acquisition we evaluate the imprint of the out‐of‐plane propagation on the data and the results of full‐waveform inversion. We show that 2D velocity model building from the seismic profiles acquired in the complex geological setting can lead to wrong solution. Looking for the remedy to this issue we couple different configurations of acquisition geometries with 3D full‐waveform inversion that allow to handle the 3D effect and provide correct model reconstruction.

Microfluidic–nanophotonic sensor for on-chip analysis of complex refractive index

Photonic biosensors based on photonic integrated circuits (PICs) and microfluidic channels (MFCs) have become the subject of intensive research for point-of-care (POC) device applications. In the presented work, we demonstrate the possibility of identifying the complex refractive index (RI) of analyzed liquids through the optimization of the geometry configuration of MFCs under PICs by experimental and numerical approaches. Our results suggest that the real and imaginary parts of the RI for analytes under study can be determined from spectrum of devices with optimized MFCs width. This work paves the way for promising opportunities to identify the presence and concentration of biological markers by using RI sensors for in situ POC applications.

Improved resistive plate chambers for HL-LHC upgrade of CMS

In view of the High Luminosity LHC, the CMS Muon system will be upgraded to sustain its efficient muon triggering and reconstruction performance. Resistive Plate Chambers (RPC) are dedicated detectors for muon triggering due to their excellent timing resolution. The RPC system will be extended up to 2.4 in pseudorapidity. Before the LHC Long Shutdown 3, new RE3/1 and RE4/1 stations of the forward Muon system will be equipped with improved Resistive Plate Chambers (iRPC) having, compared to the present RPC system, a different design and geometry and 2D strip readout. This advanced iRPC geometry configuration allows the rate capability to improve and hence survive the harsh background conditions during the HL-LHC phase. Several iRPC demonstrator chambers were installed in CMS during the recently completed 2nd Long Shutdown to study the detector behaviour under real LHC conditions. This paper summarizes the iRPC project and its schedule, including the status of the iRPC production sites, details of the chamber quality control procedures and results of the commissioning of the demonstrator chambers.

A numerical study on applying ion concentration polarization in micropump design

This work focuses on applying the phenomenon of ion concentration polarization to design and investigate a micropump model that is a kind of electroosmotic micropump. Numerical study is conducted for ion concentration polarization in the manner that generates electro-osmosis flow and pumping effect. The formation of the extended space charge layer and the actions of the electric field upon this layer is applied to generate electro-osmosis flow to drive flow in the system. It is clarified that pumping effect can be enhanced by improving the geometry configurations. Multiple simulations are conducted to obtain an optimal micropump design.

Geometry Configuration and Bromo Substitution Effect of Terfluorenes on Amplified Spontaneous Emission Behaviors

Geometry Configuration and Bromo Substitution Effect of Terfluorenes on Amplified Spontaneous Emission Behaviors

Analysis and compensation of stop-and-go approximation in high-resolution spaceborne synthetic aperture radar

ABSTRACT With the advancement of spaceborne synthetic aperture radar (SAR) resolution, the conventional stop-and-go approximation-based motion model is no longer suitable for high-resolution imaging algorithms. This paper conducts a comprehensive analysis of the approximation errors resulting from the stop-and-go approximation and proposes corresponding compensation methods. Firstly, an accurate echo model based on continuous platform motion is derived from the SAR geometry configuration. The impact of these errors on range and azimuth imaging is analysed from a spectral perspective, and the applicable boundary conditions are examined. Subsequently, compensation methods are proposed to eliminate the introduced approximation errors, addressing both”fast time” and”slow time” effects, thus enabling high-resolution imaging through improvements in traditional imaging algorithms. Experimental simulations validate the effectiveness of the error analysis and compensation methods, using X-band low Earth orbit SAR as an illustrative example. The proposed methods are not only compatible with existing mature imaging algorithms, but the analytical approach and compensation methods are also applicable to SAR systems operating on different carrier frequencies, orbits, and platforms.

Influences of geometry configurations on the performance of micro-nozzles

Micro-nozzles play a critical role in various applications, such as micro-/nano-satellites in aerospace and heat dissipation and cooling in microelectronic systems (MEMS). The flows inside micro-nozzles can experience both continuum and rarefied flow due to their small size. In this research, we explore the optimal geometry configuration of micro-nozzles to achieve comprehensive performance and size, as well as background pressure compensation. Using classical computational fluid dynamics (CFD) and direct simulation Monte Carlo methods (DSMC), we investigate the effects of the expansion ratio, cross-profile shape, and plug on the performance of micro-nozzles operating over a wide range of pressures (0.5−100kPa). The results reveal that micro-nozzle performance is influenced by the interplay between flow expansion and viscous loss induced by the subsonic layer next to the micro-nozzle wall. The findings show that micro-nozzle performance improves with increasing expansion ratio in slip and continuum flow regimes, but decreases in the transition flow regime. Additionally, the results indicate that the axisymmetric micro-nozzle (with a circular cross-profile) outperforms the linear micro-nozzle (with a rectangular cross-profile) in terms of both performance and size when subject to the same conditions, making it the recommended choice for practical applications. We also find that plugs designed at the throat decrease performance, but increase stability under diverse background pressures. This study provides valuable insights for the design of high-efficiency micro-nozzles in applications such as nanosats and MEMS heat dissipation units.

Designing CO2 reduction microreactor systems under fluctuating renewable H2 supply by multi-objective stochastic optimization

Reverse water-gas shift (RWGS) microreactor systems offer the flexibility to efficiently utilize CO2 and renewable H2 for syngas production. However, the inherent fluctuation in the green H2 supply presents a substantial obstacle for cost-effective production, particularly at larger scales. In this work, the design and operation of RWGS microreactor systems with fluctuating H2 feed are addressed by multi-objective stochastic optimization. The optimization objectives are the reaction performance, the annual total cost, and the carbon footprint of the microreactor system, while the decision variables include the channel geometry, channel topology, and inter-stack flow controller configuration. The results demonstrate that a well-designed hierarchical microreactor system achieves excellent reaction performance even without inter-stack flow controllers under both deterministic and uncertain conditions. Small plate-level distribution channels and moderate-sized higher-level distribution channels allow good and stable reaction performance. To balance all the design objectives, it is suggested to first increase the number of stacks at smaller production scales and then increase the number of substrates within each stack at larger production scales. Our study provides new design insights for distributed production using modular devices under high penetration of renewable energy.

Numerical investigation of the effective mechanical properties of Octet Truss lattice structures with different strut geometry

Lattice structures have an important role in lightweight structure applications as they can supply their mechanical performance with less material. Porous structures designed with inspiration from nature, has been used in many industries such as aerospace, automotive, defense industry and biomedical field. In order to continue these advances, studies on various design configurations of porous structure geometries are carried out. This study aimed to increase the usage potential of Octet Truss lattice structures in various sectors. A numerical model is created for 3 variable parameters: strut geometry, porosity, and material type. The effective elastic modulus values are determined based on the principles of Hooke's law for each model. Based on the obtained effective elastic modulus values, it has been concluded that differences in strut geometries, porosities, and material types contribute to 1.27%, 68.85%, and 29.86% of the observed effects, respectively. In order to establish a correlation between these factors, the data is transmitted to the MATLAB software, where equations are generated using the curve fitting approach. A total of nine equations have been generated and the R-square for these equations above 0.99. According to the two desired constant values, the effective elastic modulus can be calculated using these equations without any restrictions.

Multi-objective optimization for snap-through response of spherical shell panels

Composite spherical shell panels are commonly used for the lightweight design of thin-walled structures in the structure, architecture, aerospace engineering. Depending on the shell panel length, thickness, curvature, and stacking sequence, the load-deflection response under lateral load can be either a completely stable equilibrium path or an unstable snap-through path. In this work, the response of simply supported cross-ply composite spherical shell panels subjected to lateral static loads is studied and optimized. The spherical shell exhibiting snap-through response is optimized to (a) maximize the load required to initiate snap-through and (b) minimize the unstable region. Meanwhile, the spherical shell exhibiting continuous response is optimized to (a) maximize the softening-hardening load and (b) minimize the shell weight. The decision variables for both constraint multi-objective optimization (CMOO) problems include layup sequence, thickness, and the radius of curvature to side length ratio. The nonlinear governing equations are derived based on Kirchhoff–Love hypotheses for thin shells and Hamilton's principle. A novel semi-analytical method is presented based on Bernstein polynomials combined with a fast iterative approach to compute the objective features of the responses. Benefiting from the high efficiency and robustness of the proposed approach, the CMOO problems are solved by the metaheuristic Multi-Objective Artificial Hummingbird Algorithm (MOAHA). Composite spherical shell panels with various geometry and lamination configurations are considered to validate the performance of the proposed method. The optimization of geometric parameters (shell curvature and thickness) in addition to the staking sequence provide a high degree of tailoring of the shell performance to meet various objectives. These parameters are taken as design variables that must be optimized to achieve some objectives and satisfy arbitrary nonlinear constraints.

Design framework for phononic crystals based on compression-twist coupling structures with curved beams

Compression-twist coupling structures (C-TCSs) with curved beams (CBs) exhibit unusual static and dynamic mechanical behaviours, leading great application potentials for massive engineering structures including metamaterials. Specially, the acoustic metamaterials or phononic crystals (PCs) featured by C-TCSs present outstanding bandgap properties (such as tuneable central-position and width of bandgaps adjusted via the geometry of the CBs) than those from traditional designs, endowed with numerous applications with respect of vibration and wave control fields. This paper proposes a C-TCS connected by CBs for super coupling effect and specified bandgap behaviour when treated as PCs. To investigate the performance of the C-TCS and the resulting PCs, isogeometry analysis and finite element method are adopted. A design and optimization framework with genetic algorithms is further established to search for the optimal geometry configuration of the C-TCSs. Our results show that the refined C-TCSs with CBs enhance significantly the coupling performance. And the redesigned PCs, especially those with gradient unit cells, present advanced capabilities of low-frequency, large width and prescribed bandgaps. The proposal creates a new way to the design of novel acoustic metamaterials.

Evolution features and optimization of interface shape during CdZnTe crystal growth using Vertical Gradient Freeze (VGF) technique

The growth of CdZnTe crystal suffers from poor yield due to the low thermal conductivity, and a convex growth interface is usually essential to grow large-volume CdZnTe single crystal because it can lessen the adverse interactions between the growing crystal and crucible wall. The growth of 90 mm diameter CdZnTe crystal by VGF technique has been investigated using experimental and simulation methods. The influences of the growth parameters (such as temperature gradient and growth rate) and the heat transfer configurations on the growth interface shape have been inspected respectively by the unsteady simulation. The simulation results confirm that the interface shape exhibits the tendency to be “convex → flat → concave” due to the gradually deteriorated heat transfer environment with time during growth. In addition, a modified configuration has been designed and used in experiments based on the simulation results, with the aim of strengthening the conduction heat transfer of the center region of the configuration geometry. The modified configuration consists of the splicing tapered-contact quartz&graphite support with a shorter conical region and seed region, as well as the SiC holder. Experimental results demonstrate that the modified configuration would make the growth interface maintain a convex shape for a longer duration. The CdZnTe crystal grown by using the modified configuration possesses fewer grains compared with that using the initial configuration.

Numerical and Experimental Investigation of a Volumetric Resistance Blower Performance and Its Optimization for Portable Computing Device Applications

Abstract In this paper, we present our results on a relatively new kind of blower called Volumetric Resistance Blower (VRB) for cooling of portable computing platforms like laptop computers. The VRB performance was modeled numerically and compared to traditional bladed blowers. The sources of noise, dominant in bladed blower, are absent in case of VRB, because it uses a continuous porous disk instead of discrete blades. Thus, even though at iso-rpm, VRB yielded lower flowrate, its iso-acoustic performance could be superior. Hence, further analysis was crucial to quantify the potential benefit. The acoustics experiments for bladed blower and VRB were conducted in a hemi-anechoic chamber in accordance with ECMA-74 and ECMA TR/99 standards. Iso-acoustics pressure versus volume flowrate plot for both bladed blower and VRB are compared. VRB was found to have superior performance as compared to bladed blower. The volume flowrate at open flow condition for bladed blower and VRB are comparable, but as back pressure increased the flowrate yielded by VRB kept increasing and at stagnation condition, VRB showed around 79% higher static pressure. In the second part of the work, the experimentally validated numerical model for VRB was used for numerical optimization using a design of experiments (DOE) approach and varying the geometrical parameters. Rotor distance (minimum distance from the axis of rotation of impeller to the cutwater surface) was found to be the most important parameter, and an optimum value was found. A second DOE elucidated the optimal rotor hub center location in the two-dimensional space inside the casing as when the rotor is tucked back into the casing as much as possible and when the rotor distance is above 20.15 mm. A partial P–Q curve is generated (up to 20 Pa) for optimal geometry configuration. Based on the numerical and experimental evidence, VRB is found to have the potential to replace traditional bladed design in portable computing devices. In addition, due to absence of blades, it creates lower tonal noise, giving a much more comfortable experience to the end user.

Benchmarking and economic analysis of the impact of geometric structural design on the thermoelectric performance of air‐cooled photovoltaic thermal systems

AbstractFor a sustainable system to be designed with the lowest possible cost, photovoltaic thermal (PV/T) system efficiency and heat transmission must be increased. The performance of each hybrid PV/T air system was examined using four air PV/T models with various geometric configurations. The examination of the various mathematical models revealed how each geometry configuration affected each system's performance. Air PV/T arrangements with expanded surfaces, like fins, enhance thermoelectric performance. According to the findings, the thermal efficiencies of finned absorber PV/T and finned Tedlar PV/T are, respectively, 80.3 and 77.54%. Additionally, the figures for electrical efficiencies are 11.88 and 11.93%, respectively. For these two types of PV/T systems, the annual energy output has increased and now stands at roughly 3242 and 3316 kWh/m2, respectively. Additionally, compared to other PV/T systems, the finned Tedlar PV/T system offers higher profitability in terms of cost and revenue according to an economic research.

Fatigue reliability assessment of load‐carrying cruciform welded joints with undercuts and misalignments

AbstractThe additional local stress concentration caused by undercut and misaligned defects could lead to lower fatigue strength of welded joints. The paper aims to investigate the effects of undercuts and misalignments on fatigue performance and reliability of Load‐carrying Cruciform Welded Joint (LCWJ) quantitatively by probabilistic statistics theory and fracture mechanics theory. Firstly, the geometrical characteristics of undercut and misalignment are summarized from the literature and our experiments. Subsequently, the probabilistic distributions of material fracture properties, the configurations of geometries, and flaws were evaluated under specific loading conditions. The fatigue strengths are further estimated by the probabilistic reliability theory by combining the actual fatigue data. The results demonstrate a clear disparity of fatigue crack growth threshold and resistances for the tested data of base metal and weldment. The level of defects determines the interval of fatigue life, and the larger the dispersion accompanying earlier fatigue failure occurs.

Droplet generation by the oscillation of two spark-generated bubbles near a confined opening

Cavitation bubbles can be both beneficial and detrimental. One of their beneficial applications is to produce droplets as they oscillate near a confined free surface. In this paper, the oscillation of two spark-generated bubbles beneath a confined free surface and the resultant droplet generation are studied numerically using boundary element method. Three different configurations are considered: (i) a vertical cylinder (θ = 0°), (ii) a vertical nozzle (θ = 45°) and (iii) a perforated horizontal flat plate (θ = 90°). The influences of the effective parameters, including the initial pressure and locations of the bubbles, and the configuration geometry on the dynamics of the bubbles, the free surface and the resultant droplet are studied. It was found that by decreasing the inter-bubble distance, the droplet size increases and its pinch-off occurs earlier. In general, the effect of the distance of the upper bubble from the free surface on the droplet behavior is much more significant than that of the inter-bubble distance. Furthermore, through the augmentation of the upper bubble's strength parameter, the droplet size is reduced and the moment of droplet pinch-off is postponed. Finally, the droplet size and its pinch-off time increase from the vertical cylinder to the flat plate case.

Investigation of characteristics and generating mechanism of wind noise on external microphone of mobile device

The multipurpose external microphone of mobile devices is exposed to the outside windy environment, which inevitably generates wind noise. The wind noise acts as noise in signal processing, like Active Noise Control and capturing voice, and damages the user's experience. This paper investigates the acoustic characteristics and generation mechanism of wind noise through experiments and numerical analysis for a commercial TWS earbuds model. The experimental results show that the wind noise has broadband characteristics with dominant low-frequency band noise (below 2500Hz), unlike general cavity flow. On the same model, the Lattice-Boltzmann method numerical analysis has been performed through powerFLOW software. The numerical result shows good agreement of +-3dB with experimental results in the 1/3 octave band spectrum for the wind noise band. Numerical results flow field investigation reveals that the disturbed flow field is induced by an interaction between the vortical structure of the inflow and separated flow field, which is governed by geometry configurations. The disturbances induce the complex pressure gradient on inflow into the microphone, measured as wind noise on the microphone. These results show that the wind noise measured by the microphone of mobile devices is a flow phenomenon caused by external excitation.