Different Combinations Of Geometrical Parameters Research Articles

A novel approach for estimating blood flow dynamics factors of eccentric stenotic arteries based on ML

Reliable and rapid estimation of blood flow dynamics factors in eccentric stenotic arteries could significantly improve clinical treatments. Numerical simulation methods such as FSI and CFD are widely used to investigate blood flow conditions. However, both FSI and CFD are computationally expensive and not suitable for large-scale research. This work proposes an effective approach for estimating the blood flow dynamics factors of eccentric stenotic arteries based on ML. The estimation approach includes three steps: (a) blood flow conditions of idealized eccentric stenotic arteries modeled with different geometric parameters were simulated by CFD and FSI, and the error between CFD and FSI results were evaluated, (b) datasets of nonlinear relationships between discretized geometric parameters and blood flow dynamics factors were created using CFD, and (c) blood flow dynamics factors of eccentric stenotic arteries were estimated by carefully designed ML model. The accuracy validation was conducted by different representative cases, which have different combinations of geometric parameters including stenosis severity, eccentricity, and stenosis plaque length. The ML model can output the blood flow dynamics factors including peak wall shear stress and peak systole velocity accurately within 1 s, which shows proposed approach not only achieves accurate estimation of blood flow dynamics factors but also bypasses the expensive computational cost.

Numerical Investigation on Gas Production Performance in Methane Hydrate of Multilateral Well under Depressurization in Krishna-Godavari Basin

Nature gas hydrate is a new kind of clean and potential resources. Depressurization is regarded as the most effective and promising hydrate production technology. One of the key points in improving the gas production effectiveness of depressurization is whether pressure gradient could transmit in strata effectively. Single well method is widely used in hydrate exploit which is circumscribed in expanding the range of hydrate decomposition. Consequently, the well structure and production strategy needs to be optimized for improving the gas recovery efficiency. The multilateral well technology is proposed for increasing the gas productivity of the reservoir greatly by increasing the multilateral branches. In this paper, we established a numerical simulation model based on the geological data NGHP-02-16 site in the KG basin to evaluate the gas production performance of the reservoir by depressurization. It mainly focuses on investigating the gas production performance of multilateral wells with different combinations of geometric parameters of multilateral branches, such as different dip angle, numbers, and spacing of lateral branches. The result shows that the multilateral well method can effectively increase the gas production rate with the water production rate increase slightly. The cumulative gas production volume of a single vertical well is about 2.85 × 10 6   m 3 , while it is of the multilateral well can reach 4.18 × 10 6   m 3 during a one-year production. The well interference, the effective influence radius of each multilateral branch, and the vertical depth of the lateral branch are the main factors which affect the gas production efficiency of the multilateral well. The optimization of the geometric parameters of lateral should consider not only the gas production efficiency but also the well interference between the lateral branches.

Effect of urban built form and density on building energy performance in temperate climates

Urban built form and density are crucial parameters for the optimization of building energy performance. However, a cohesive framework which correlates building energy with urban built form and density is lacking, with no unified agreement on the concept of urban density. This study establishes the subtle interrelationships between urban built forms, density and building energy performance using two density indicators, specifically, site coverage and plot ratio. This paper initially considers geometrical variables of four customary urban built forms to investigate their relationship with the density indicators. Energy analyses are performed on the geometrical models representing residential buildings using the City of London as an example of a temperate climate. Annual building energy demands of pavilion, terrace, court and tunnel-court forms are calculated. The findings are used to produce a heat map of energy intensity on the Form Signature graphs. Results show that high-rise buildings with greater plan depths achieve higher energy efficiency. Moreover, it is shown that greater cut-off angles correspond to higher energy demands under temperate climatic conditions. An energy indicator, termed Energy Equity is introduced which represents the ratio between PV energy generation installed on roofs with respect to the total energy demand of the building. Further analyses show that by considering energy demand and PV energy generation simultaneously, low-rise buildings with greater plan depths provide improved energy performance. A comparative analysis of the energy performance of different built forms with similar geometric parameters demonstrates that the tunnel-court and the pavilion built forms provide the best and worst energy performance, respectively. However, when constraining density whilst changing other geometric parameters, this converse is true. Finally, the study illustrates that the same density for the same built form can be achieved by different combinations of geometric parameters that certainly affects energy performance of buildings. Graphic display of the analysis results provide urban planning guidelines that represent the database of major findings of this study. It can be used by designers, planners and architects to identify the most energy-efficient built form and density for promoting more sustainable cities.

Analysis and optimisation of a rib-stiffened vaulted floor for dynamic performance

There appears in the construction of modern multi-storey buildings in recent years, a prevailing trend for large bay sizes, lightweight floor systems and reduced dividing partitions. These tendencies have aroused a greater awareness of potential vibration problems when the structural floor systems are subjected to human induced activities such as footfall loading, as vibration performance may become an influential factor in the design of lightweight floor structures. A rib-stiffened vaulted floor described in this paper, can achieve sufficient structural stiffness and load-bearing capacity in an ultra-lightweight construction system. The aim of this study was to obtain a fundamental understanding of the floor’s dynamic behaviour and to develop appropriate measures to improve its dynamic performance. Dynamic analyses and assessment were conducted on 180 mesh models of the floor with different combinations of geometric parameters and compared against acceleration acceptance criterion. After the parametric performance evaluations, qualitative and quantitative relationships among the geometric parameters, modal parameters and dynamic performance were found, where it was shown that most floors failed to meet the acceptance criterion. Different approaches were then taken to improve the dynamic performance of the floors, using manual distribution of additional mass or optimised relocation of constant total mass. Selective distribution of mass in targeted areas accomplished considerable improvements in the dynamic performance. This paper identifies that statically optimised low-mass floors may be particularly sensitive to footfall loading, and establishes a reliable procedure for dynamic analysis using the dynamic characteristics of a rib-stiffened vaulted floor, revealing improvements to dynamic performance and providing insight into high frequency floors.

Deriving guidelines for the design of plate evaporators in heat pumps using zeotropic mixtures

This paper presents a derivation of design guidelines for plate heat exchangers used for evaporation of zeotropic mixtures in heat pumps. A mapping of combined heat exchanger and cycle calculations for different combinations of geometrical parameters and working fluids allowed estimating the trade-off between heat transfer area and pressure drops on the thermodynamic and economic performance indicators of the cycle. Compressor running costs constituted the largest cost share, and increased due to a steep decrease of the heat pump coefficient of performance at high refrigerant pressure drops. It was found that the pressure drop limit leading to infeasible designs was dependent on the working fluid, thereby making it impossible to define a guideline based on maximum allowable pressure drops. It was found that economically feasible designs could be obtained by correlating the vapour Reynolds number and the Bond number at the evaporator inlet as ReV−0.42Bd0.26≈0.040. The use of the proposed guideline was illustrated for the mixture Propane/Iso-Pentane (0.5/0.5), leading to evaporator designs with net present values deviating maximum −4.4% from the best value found in the mapping. The presented methodology can be applied in different scenarios to develop similar guidelines, thereby decreasing the cost of combined cycle and component optimizations.

Peridynamic simulation of fracture in quasi brittle solids using irregular finite element mesh

When subjected to increasing external loads, quasi brittle solids usually experience crack nucleation and propagation, leading to final failure of material. Numerical modeling and simulation of cracking process is an essentially important issue in mechanics and engineering science. This paper aims at applying the peridynamic method to simulate crack propagation using irregularly distributed material grids generated from finite element mesh. For post-treatment of physical fields such as strain and stress, a relevant visualization technique is developed. Various numerical tests are conducted for validation and application. Firstly, a square plate with a centrally located circular hole is considered for uniaxial tension tests performed with different non-uniform distributions of material grids. Peridynamic predictions are compared to finite element results and the influence of grid density, distribution and orientation on fracturing process is evaluated and the nonlocality of numerical results is demonstrated. Secondly, a pre-cracked plate with an off-centre circular hole is simulated under tension condition to assess the performance of locally refined grid. Finally, a square plate containing two parallel pre-existing cracks under biaxial tension is tested under different combinations of geometric parameters. The present work is in favour of developing a combined peridynamics/finite element numerical technique for efficient modelling and simulation of complex cracking problems.

Multiple topological phase transitions in a gyromagnetic photonic crystal

We present the design of a tunable two-dimensional photonic crystal that exhibits multiple topological phases, including a conventional insulator phase, a quantum spin Hall phase, and a quantum anomalous Hall phase under different combinations of geometric parameters and external magnetic fields. Our photonic crystal enables a platform to study the topology evolution attributed to the interplay between crystalline symmetry and time-reversal symmetry. A four-band tight-binding model unambiguously reveals that the topological property is associated with the pseudospin orientations and that it is characterized by the spin Chern number. The emerging quantum anomalous Hall phase features a single helical edge state that is locked by a specific pseudospin. Simulation results demonstrate that the propagation of such a single helical edge state is robust against magnetic impurities. Potential applications, such as spin splitters, are described.

Evaluations of mixed-mode stress intensity factors for load-carrying fillet welded cruciform joints using the least-squares method

This study presents the numerical and experimental applications of using the least-squares method (LSM) to evaluate the mixed-mode stress intensity factors (SIFs) of load-carrying fillet welded cruciform joints. In the numerical application, fillet welded cruciform joints of different combinations of geometric parameters (including weld leg size, initial lack of penetration size, and plate thickness) were systematically studied using the finite element method and the LSM. The derived SIF results were used to develop the general formulae of the opening mode (mode-I) and shearing mode (mode-II) SIFs, K I and K II, respectively. To validate the numerical results, five fillet welded cruciform joint specimens were fabricated and tested by a non-contact optical experiment using a commercial digital camera and the digital image correlation technique for image processing. The numerical and experimental mode-I SIF results were in good agreement with the results from the existing BS 7910 formula for fillet welded cruciform joints. In addition, the suggested non-contact optical experiment is simple and portable, making it well-suited for measuring mixed-mode SIFs directly from the welded details on site. This is very useful for fracture and fatigue evaluation and analysis of weld in existing or newly designed structures, such as steel bridges and offshore structures.

The Cosserat Elasticity Constants of Circular Cell Honeycombs

Closed form expressions for the Cosserat constants for circular cell honeycombs are derived using a combination of non-dimensional analysis and numerical analysis. The expressions for the four in-plane Cosserat compliances, which are the plane strain bulk compliance, the shear compliance, the micropolar compliance and the bending compliance are derived in terms of the cell size, cell thickness and the linear elastic properties of the cell wall material. Numerical analyses are performed to verify the accuracy of the derived constants by considering different combinations of geometric parameters and different numbers of cells for the honeycombs. It is shown that the closed form expressions are an accurate representation of the Cosserat constants of circular cell honeycombs.

Comparison of fatigue life for T and cruciform welded joints with different combinations of geometrical parameters

The fatigue life for T and cruciform welded joints containing different extents of lack of root penetration was calculated for different combinations of geometrical parameters, including thicknesses up to 45 mm, by integration of the Paris law and use of stress intensity factor solutions calculated previously. The effect of attachment and main plate thickness, weld leg length and initial lack of penetration size on fatigue life was studied. For T welded joints, the effect of different support span has also been investigated. The results are reported as fatigue life curves for both types of joints. All the curves show higher fatigue life for T joints than for cruciform joints. These curves were then compared with the S– N curves for failure from either weld toe position or on the weld throat, proposed by Eurocode 3. The maximum tolerable sizes for lack of penetration at which weld toe failures would still rule are reported for each case. Results of experimental tests are in good agreement with the predictions.