Concentrated Point Sources Research Articles

Effect of hollow fiber membrane packing on the performance of modules formed with fiber tows

ABSTRACT Membrane processes are being considered for carbon dioxide capture from concentrated point sources. The processes often use hollow fiber membranes. Modules are formed by gathering fibers together in a bundle. The fibers may be supplied individually or in small groups (i.e. tows) for module fabrication. The use of tows can introduce nonuniform fiber packing due to the size and spacing of the tows. The potential for flow maldistribution and its detrimental effect on module performance is evaluated by solving the governing conservation equations. For the first time, the performance of a module formed from fiber tows is evaluated. Two performance metrics are reported: 1) recovery and 2) required area as a function of carbon dioxide removal. The effects of tow size and tow spacing are evaluated. The results indicate performance is better for smaller tows. Furthermore, lower packings, both intra- and inter-tow, are preferred. The concept of an equivalent planar bundle (EPB) for fiber tow modules is introduced to potentially reduce simulation time and costs. The simple procedure for creating the EPB is validated by comparing the performance metrics calculated using the EPB to the results obtained from full simulations.

Constructing a measurement-based spatially explicit inventory of US oil and gas methane emissions (2021)

Abstract. Accurate and comprehensive quantification of oil and gas methane emissions is pivotal in informing effective methane mitigation policies while also supporting the assessment and tracking of progress towards emissions reduction targets set by governments and industry. While national bottom-up source-level inventories are useful for understanding the sources of methane emissions, they are often unrepresentative across spatial scales, and their reliance on generic emission factors produces underestimations when compared with measurement-based inventories. Here, we compile and analyze previously reported ground-based facility-level methane emissions measurements (n=1540) in the major US oil- and gas-producing basins and develop representative methane emission profiles for key facility categories in the US oil and gas supply chain, including well sites, natural-gas compressor stations, processing plants, crude-oil refineries, and pipelines. We then integrate these emissions data with comprehensive spatial data on national oil and gas activity to estimate each facility's mean total methane emissions and uncertainties for the year 2021, from which we develop a mean estimate of annual national methane emissions resolved at 0.1° × 0.1° spatial scales (∼ 10 km × 10 km). From this measurement-based methane emissions inventory (EI-ME), we estimate total US national oil and gas methane emissions of approximately 16 Tg (95 % confidence interval of 14–18 Tg) in 2021, which is ∼ 2 times greater than the EPA Greenhouse Gas Inventory. Our estimate represents a mean gas-production-normalized methane loss rate of 2.6 %, consistent with recent satellite-based estimates. We find significant variability in both the magnitude and spatial distribution of basin-level methane emissions, ranging from production-normalized methane loss rates of < 1 % in the gas-dominant Appalachian and Haynesville regions to > 3 %–6 % in oil-dominant basins, including the Permian, Bakken, and the Uinta. Additionally, we present and compare novel comprehensive wide-area airborne remote-sensing data and results for total area methane emissions and the relative contributions of diffuse and concentrated methane point sources as quantified using MethaneAIR in 2021. The MethaneAIR assessment showed reasonable agreement with independent regional methane quantification results in sub-regions of the Permian and Uinta basins and indicated that diffuse area sources accounted for the majority of the total oil and gas emissions in these two regions. Our assessment offers key insights into plausible underlying drivers of basin-to-basin variabilities in oil and gas methane emissions, emphasizing the importance of integrating measurement-based data when developing high-resolution spatially explicit methane inventories in support of accurate methane assessment, attribution, and mitigation. The high-resolution spatially explicit EI-ME inventory is publicly available at https://doi.org/10.5281/zenodo.10734299 (Omara, 2024).

Dual Salt Cation-Swing Process for Electrochemical CO2 Separation.

Electrochemical CO2 separations, which use electricity rather than thermal energy to reverse sorption of CO2 from concentrated point sources or air, are emerging as compelling alternatives to conventional approaches given their isothermal, ambient operating conditions, and ability to integrate with renewable energy inputs. Despite several electrochemical approaches proposed in previous studies, further explorations of new electrochemical CO2 separation methods are crucial to widen choices for different emissions sources. Herein, we report an electrochemical cation-swing process that is able to reversibly modulate the CO2 loading on liquid amine sorbents in dimethyl sulfoxide (DMSO) solvent. The process exploits a reversible carbamic acid-to-carbamate conversion reaction that is induced by changing the identity of Lewis acid cations (e.g. K+, Li+, Ca2+, Mg2+, and Zn2+) coordinated to the amine-CO2 adduct in the electrolyte. Using ethoxyethylamine (EEA) as a model amine, we present NMR-based speciation studies of carbamic acid-to-carbamate conversion as a function of amine/salt concentrations and cation identity. The reaction is further probed using gas-flow reaction microcalorimetry, revealing the energetic driving forces between cations and the amine-CO2 adduct that play a key role in the described re-speciation. A prototype electrochemical cell was further constructed comprising a Prussian white (PW) potassium (K+) intercalation cathode, zinc (Zn) foil anode, and EEA/DMSO electrolyte containing a dual KTFSI/Zn(TFSI)2 salt. A low CO2 separation energy of ∼22-39 kJ/mol CO2 (0.1-0.5 mA cm-2) was achieved with a practical CO2 loading delta of ∼0.15 mol CO2/mol amine. Further optimizations in electrolyte design and cell architectures toward continuous CO2 capture-release are expected to enhance rate performance while retaining favorable separation energies.

(Invited) Electro-Swing Adsorption for CO2 Emissions Mitigation – from Concept to Start-up

The increasingly devastating effects of changing climate patterns can be attributed largely to global warming through the continuing accumulation in the environment of anthropogenic greenhouse gases such as carbon dioxide. While reduction of CO2 emissions at relatively concentrated (4-20%) point sources is a crucial component of mitigation strategies for the abatement of the CO2 impact on global temperature rise, it has become increasingly evident that direct removal of accumulated CO2 (at 420ppm, 0.042%) from the environment will also be needed if we wish to limit the global temperature rise by the turn of the century to less that 2°C. Legacy carbon capture processes rely on thermal swings, with elevated temperatures required to break the chemical bonds formed during the cooler capture stage to liberate the CO2 as a pure product stream and regenerate the sorbent. There has recently been a surge of interest in using electrochemically mediated processes for carbon capture and release which can be operated isothermally, are modular, with easy scale out, and can be installed without need for complex heat integration processes. Moreover, they can use renewable and other non-carbon energy resources.In this presentation, we will trace the development of an electrochemical swing adsorption approach for the capture of CO2, originally conceived in 2015, through to the incorporation of a start-up, Verdox, in 2019 to exploit the technology in both point source and direct air capture applications. This approach exploits the ability of certain redox species, such as quinones, to bind strongly with CO2 when in a reduced state, but which have no affinity for the acid gas when oxidized. The activation by reduction and subsequent de-activation by oxidation of the capture agent can be achieved electrochemically with the redox species either in solution or immobilized on electrode surfaces; it is this latter strategy that we will discuss here. The challenges in electrode development, including the identification and economical synthesis of appropriate redox species for the binding of the CO2, and enhancement of chemical and physical robustness with acceptable uptake kinetics, will be discussed, with projections on the future introduction to industrial applications.

Comparison of antibiotic-resistant Escherichia coli and extra-intestinal pathogenic E. coli from main river basins under different levels of the sewer system development

Antimicrobial-resistant Escherichia coli in the aquatic environments is considered a strong indicator of sewage or animal waste contamination and antibiotic pollution. Sewer construction and wastewater treatment plant (WWTP) infrastructure may serve as concentrated point sources of contamination of antibiotic-resistant bacteria and antibiotic resistance genes. In this study, we focused on the distribution of antimicrobial-resistant E. coli in two rivers with large drainage areas and different urbanisation levels. E. coli from Kaoping River with drainage mainly from livestock farming had higher resistance to antibiotics (e.g. penicillins, tetracyclines, phenicols, aminoglycosides, and sulpha drugs) and presented more positive detection of antibiotic-resistance genes (e.g. ampC, blaTEM, tetA, and cmlA1) than that from Tamsui River. In Kaoping River with a lower percentage of sewer construction nearby (0–30%) in contrast to a higher percentage of sewer construction (55–92%) in Tamsui River, antimicrobial-resistant E. coli distribution was related to livestock farming waste. In Tamsui River, antimicrobial resistant E. coli isolates were found more frequently in the downstream drainage area of WWTPs with secondary water treatment than that of WWTPs with tertiary water treatment. The Enterobacterial Repetitive Intergenic Consensus (ERIC) PCR showed that the fingerprinting group was significantly related to the sampling site (p < 0.01) and sampling date (p < 0.05). By utilising ERIC-PCR in conjunction with antibiotic susceptibility and antibiotic-resistance gene detection, the relationship among different strains of E. coli could be elucidated. Furthermore, we identified the presence of six extra-intestinal pathogenic E. coli isolates and antibiotic-resistant E. coli isolates near drinking water sources, posing a potential risk to public health through community transmission. In conclusion, this study identified environmental factors related to antibiotic-resistant bacteria and antibiotic-resistance gene contamination in rivers during urban development. The results facilitate the understanding of specific management of different waste streams across different urban areas. Periodic surveillance of the effects of WWTPs and livestock waste containing antibiotic-resistant bacteria and antibiotic-resistance genes on river contamination is necessary.

(Invited) Opportunities and Challenges for Biopolar Membrane-Based Electrosynthesis

Over the last 3 decades, research on CO2 abatement technologies centered solely on carbon capture and storage (CCS). Here, technology focus is in the design of separations technologies to capture CO2 from concentrated point (e.g. flue gas) or dilute distributed sources (e.g. atmosphere) using amine absorption, adsorption, and membranes. Most of these technologies involve adsorbing or absorbing CO2 gas, releasing this gas, and then pressurizing it for storage. Thus, a number of different subsystems and specialized new equipment are needed resulting in high capital and operating costs. As a result, CO2 capture for CCS is economically unfavorable in the absence of utilization routes for the captured CO2. Electrolysis of CO2 is a viable potential pathway toward attaining utilization; however, carbon loss in traditional electrolysis architectures is a large limitation. To overcome this challenge, movement toward bipolar-membrane (BPM) based electrolysis cells have been proposed as a viable option. BPMs contain an anion and a cation exchange layer. At the interface of these membranes, a junction potential forms when a electric field is applied across the membrane. Thus, within a BPM electrolysis cell, charge balancing occurs through water electro dissociating at the interface of the anion and cation membrane, thereby forming charge carriers in the form of OH- and H+. The production of acid and base in situ allows for a continuous process with low carbon losses. The primary aim of this talk is to discuss the challenges and opportunities that exist with the development of proper catalyst and membranes for these systems for carbon capture and electrofuel production.

Recent Advances in Small-Scale Carbon Capture Systems for Micro-Combined Heat and Power Applications

To restrict global warming and relieve climate change, the world economy requires to decarbonize and reduce carbon dioxide (CO2) emissions to net-zero by mid-century. Carbon capture and storage (CCS), and carbon capture and utilization (CCU), by which CO2 emissions are captured from sources such as fossil power generation and combustion processes, and further either reused or stored, are recognized worldwide as key technologies for global warming mitigation. This paper provides a review of the latest published literature on small-scale carbon capture (CC) systems as applied in micro combined heat and power cogeneration systems for use in buildings. Previous studies have investigated a variety of small- or micro-scale combined heat and power configurations defined by their prime mover for CC integration. These include the micro gas turbine, the hybrid micro gas turbine and solid-state fuel cell system, and the biomass-fired organic Rankine cycle, all of which have been coupled with a post-combustion, amine-based absorption plant. After these configurations are defined, their performance is discussed. Considerations for optimizing the overall system parameters are identified using the same sources. The paper considers optimization of modifications to the micro gas turbine cycles with exhaust gas recirculation, humidification, and more advanced energy integration for optimal use of waste heat. Related investigations are based largely on numerical studies, with some preliminary experimental work undertaken on the Turbec T100 micro gas turbine. A brief survey is presented of some additional topics, including storage and utilization options, commercially available CC technologies, and direct atmospheric capture. Based on the available literature, it was found that carbon capture for small-scale systems introduces a large energy penalty due to the low concentration of CO2 in exhaust gases. Further development is required to decrease the energy loss from CC for economic feasibility on a small scale. For the micro gas turbine, exhaust gas recirculation, selective gas recirculation, and humidification were shown to improve overall system economic performance and efficiency. However, the highest global efficiencies were achieved by leveraging turbine exhaust waste heat to reduce the thermal energy requirement for solvent regeneration in the CC plant during low- or zero-heating loads. It was shown that although humidification cycles improved micro gas turbine cycle efficiencies, this may not be the best option to improve global efficiency if turbine waste heat is properly leveraged based on heating demands. The biomass-organic Rankine cycle and hybrid micro gas turbine, and solid-state fuel cell systems with CC, are in early developmental stages and require more research to assess their feasibility. However, the hybrid micro gas turbine and solid-state fuel cell energy system with CC was shown numerically to reach high global efficiency (51.4% LHV). It was also shown that the biomass-fired organic Rankine cycle system could result in negative emissions when coupled with a CC plant. In terms of costs, it was found that utilization through enhanced oil recovery was a promising strategy to offset the cost of carbon capture. Direct atmospheric capture was determined to be less economically feasible than capture from concentrated point sources; however, it has the benefit of negative carbon emissions.

Estimation of Unintended Treated Wastewater Contributions to Streams in the Yangtze River Basin and the Potential Human Health and Ecological Risk Analysis.

"Clean water and sanitation" is one of the United Nations Sustainable Development Goals. One primary objective of wastewater treatment is to remove contaminants such as pathogens, nutrient, and organic matter from wastewater, while not all contaminants could be removed effectively. Wastewater treatment plants would inevitably represent concentrated point sources of residual contaminant loadings into surface waters. This study focuses on the populated Yangtze River Basin where emerging contaminants are frequently detected in the rivers in the recent years. A python-based ArcGIS model is developed to estimate the contributions of effluent discharges in water supply sources and quantify fate and environmental risks of human-derived contaminants in the river network. We find that one-third of the river networks are potentially influenced by the effluents through local or upstream inputs. Average fraction of unintended wastewater reuse in water supply intakes is estimated to be lower than 3% under the average flow scenario with an average traveling time of 0.05 day from the nearest effluent input site to water supply intakes. However, under low flow scenario, the percentage of effluent discharge would increase largely, leading to substantial increases in human health and ecological risks. This study provides a systematic investigation to understand extents of impacts of effluent inputs in river networks as well as identify the opportunities to improve the water management in the densely populated regions.

Environmental and Economic Performance of CO2-Based Methanol Production Using Long-Distance Transport for H2 in Combination with CO2 Point Sources: A Case Study for Germany

The use of CO2-based hydrocarbons plays a crucial role in reducing the climate footprint for several industry sectors, such as the chemical industry. Recent studies showed that regions which are favorable for the production of CO2-based hydrocarbons from an energy perspective often do not provide concentrated point sources for CO2, which leads to an increased environmental impact due to the higher energy demand of direct air capture processes. Thus, producing H2 in regions with high renewable power potential and transporting it to industrialized regions with concentrated CO2 point sources could provide favorable options for the whole process chain. The aim of this study is to analyze and compare pathways to produce CO2-based methanol in Germany using a local CO2 point source in combination with the import of H2 per pipeline or per ship as well as H2 produced in Germany. The environmental and economic performance of the pathways are assessed using life cycle assessment and cost analysis. As environmental indicators, the climate, material, water, and land footprints were calculated. The pathway that uses H2 produced with electricity from offshore wind parks in Germany shows the least environmental impacts, whereas the import via pipeline shows the best results among the importing pathways. The production costs are the lowest for import via pipeline now and in the near future. Import via ship is only cost-efficient in the status quo if waste heat sources are available, but it could be more competitive in the future if more energy and cost-efficient options for regional H2 distribution are available. It is shown that the climate mitigation effect is more cost-effective if the H2 is produced domestically or imported via pipeline. Compared to the import of CO2-based methanol, the analyzed H2 import pathways show a comparable (pipeline) or worse environmental and economic performance (ship).

Distribution and characteristics of wastewater treatment plants within the global river network

Abstract. The main objective of wastewater treatment plants (WWTPs) is to remove pathogens, nutrients, organics, and other pollutants from wastewater. After these contaminants are partially or fully removed through physical, biological, and/or chemical processes, the treated effluents are discharged into receiving waterbodies. However, since WWTPs cannot remove all contaminants, especially those of emerging concern, they inevitably represent concentrated point sources of residual contaminant loads into surface waters. To understand the severity and extent of the impact of treated-wastewater discharges from such facilities into rivers and lakes, as well as to identify opportunities of improved management, detailed information about WWTPs is required, including (1) their explicit geospatial locations to identify the waterbodies affected and (2) individual plant characteristics such as the population served, flow rate of effluents, and level of treatment of processed wastewater. These characteristics are especially important for contaminant fate models that are designed to assess the distribution of substances that are not typically included in environmental monitoring programs. Although there are several regional datasets that provide information on WWTP locations and characteristics, data are still lacking at a global scale, especially in developing countries. Here we introduce a spatially explicit global database, termed HydroWASTE, containing 58 502 WWTPs and their characteristics. This database was developed by combining national and regional datasets with auxiliary information to derive or complete missing WWTP characteristics, including the number of people served. A high-resolution river network with streamflow estimates was used to georeference WWTP outfall locations and calculate each plant's dilution factor (i.e., the ratio of the natural discharge of the receiving waterbody to the WWTP effluent discharge). The utility of this information was demonstrated in an assessment of the distribution of treated wastewater at a global scale. Results show that 1 200 000 km of the global river network receives wastewater input from upstream WWTPs, of which more than 90 000 km is downstream of WWTPs that offer only primary treatment. Wastewater ratios originating from WWTPs exceed 10 % in over 72 000 km of rivers, mostly in areas of high population densities in Europe, the USA, China, India, and South Africa. In addition, 2533 plants show a dilution factor of less than 10, which represents a common threshold for environmental concern. HydroWASTE can be accessed at https://doi.org/10.6084/m9.figshare.14847786.v1 (Ehalt Macedo et al., 2021).

Mechanics of 2D Elastic Stress Waves Propagation Impacted by Concentrated Point Source Disturbance in Composite Material Bars

Green’s function, an analytical approach in inhomogeneous linear differential equations, is the impulse response, which is applied for deriving the wave equation solution in composite materials mediums. This paper investigates the study of SH wave’s transmission influenced by concentrated point source disturbance in piezomagnetic material resting over heterogeneous half-space. Green function approach is used to solve differential equation and obtain the dispersion relation in determinant form and match with existing classical Love wave equation for the authenticity for the article. The properties of SH wave throughout the considered framework and their state of relying on varied geometrical and physical parameters are scrutinized. The simulated outcomes of disparate physical quantities viz., dimensionless phase velocity, elastic parameter, group velocity, initial stress, piezomagnetic/heterogeneity parameter and stress distribution of SH wave in the considered structure are investigated and used to regulate the behavior of dispersion characteristics of smart material waveguides.

Evaluating the biochemical potential for Irbid’s food waste as a source for energy

ABSTRACT Solid waste generated from the city of Irbid is all directed to a local unlined landfill with no gas collection system. More than half of the waste stream is made of food waste which turns the landfill to a concentrated point source of greenhouse gases. To assess the impact that the landfill has at the moment on global warming and to evaluate the future value of the city’s waste as a source of biogas, 20 trucks of municipal solid waste were sampled. In addition, food waste samples from Irbid were collected from five different sources for 12 weeks to quantify their generation rates and to measure their components and chemical composition. Irbid’s solid waste was found to have a distinctively high biodegradable content 68%, which is typical of developing countries’ solid waste. Physical assessment showed that 38%, 6%, 33% and 23% of the food waste was rice, meat, fruits and vegetables, and bread, respectively. Measured methane yields for the volatile solids (VS) in rice, meat, fruits and vegetables, and bread were 362, 499, 352 and 375 mL/g VS, respectively. A representative food waste sample was created to test the actual methane yield and compare it to calculated one. Actual methane yield (414 mL/g VS) was greater than the calculated value (370 mL/g VS) based on food type proportions and their specific methane yield. To assess the anaerobic biodegradability of food waste, a stoichiometric calculation of the methane production was made based on the elemental analysis of all food waste elements. Food waste was found to have the chemical formula C7H16O5N and calculated methane potential of 447 mL/g VS; indicating 85% anaerobic biodegradability of food waste, which makes Irbid’s waste perceived as a valuable source of energy.

Boundary mesh free method with distributed sources for 2D elasticity problems

This paper presents development Boundary Distributed Source method for 2D elasticity problems, in which sources are located at domain boundary, i.e., without fictitious boundary. Singularities of the kernel are totally removed by replacing the concentrated point sources with area-distributed sources–circular disc centered at the source point in this study–providing new kernels resulting from analytical integration of the original singular fundamental solution and its derivative on the area of the source disc. All the coefficients for Dirichlet and Neumann boundary conditions in the systems of equations can be determined analytically except diagonal coefficients for Neumann boundary conditions; they are calculated indirectly by the consideration of two reference solutions of rigid body motion in the two directions.

Computation of Lorentz Force and 3-D Eddy Current Distribution in Translatory Moving Conductors in the Field of a Permanent Magnet

Determination of the 3-D eddy current distribution inside a translatory moving conductor under a permanent magnet can accurately be done by using finite-element method (FEM). However, FEM calculations are very expensive, as they require discretization of the whole conductor volume. In this paper, we propose a new technique, to be called boundary element source method (BESM), where only boundary layers are discretized. The BESM is a modification of the hybrid boundary element method (HBEM). In the BESM, the concentrated point sources placed at the centers of boundary elements for the HBEM are replaced by distributed charge density over the area of the boundary element. This is especially useful in the regions, where neighboring boundary meshes significantly affect one another and when calculation point of eddy current is very close or belong to the surface of a boundary element. The method can handle arbitrary geometries of the specimen as well as the defect and arbitrary orientation of the magnetization vector. The accuracy of the proposed method is verified by comparing the results with the solutions obtained from a finite-element model. The proposed BESM approach is shown to be simple, robust, and computationally accurate.

A non-singular method of fundamental solutions for two-dimensional steady-state isotropic thermoelasticity problems

We consider a boundary meshless numerical solution for two-dimensional linear static thermoelastic problems. The formulation of the problem is based on the approach of Marin and Karageorghis, where the Laplace equation for the temperature field is solved first, followed by a particular solution of the non-homogenous term in the Navier-Lamé system for the displacement, the solution of the homogenous equilibrium equations, and finally the application of the superposition principle. The solution of the problem is based on the method of fundamental solutions (MFS) with source points on the boundary. This is, by complying with the Dirichlet boundary conditions, achieved by the replacement of the concentrated point sources with distributed sources over the disk around the singularity, and for complying with the Neumann boundary conditions by assuming a balance of the heat fluxes and the forces. The derived non-singular MFS is assessed by a comparison with analytical solutions and the MFS for problems that can include different materials in thermal and mechanical contact. The method is easy to code, accurate, efficient and represents a pioneering attempt to solve thermoelastic problems with a MFS-type method without an artificial boundary. The procedure makes it possible to solve a broad spectra of thermomechanical problems.

Non-Singular Method of Fundamental Solutions for Two-dimensional Thermoelasticity

A framework for simulation of thermomechanical processing of microstructures by the method of fundamental solutions, free of artificial boundary, is shown. The formulation of the method for two-dimensional thermal and mechanical models is presented. In particular, the formulation for elastic and thermo-elastic problems is discussed. In the thermal and mechanical models, the concentrated point sources are replaced by the distributed sources over the sphere around the singularity to regularize the singularities. The balance of heat fluxes and forces is used to calculate some of the otherwise singular diagonal coefficients. This procedure enables also to solve a broad spectra of thermomechanical problems. The novel boundary meshless method has been assessed by comparison with the method of fundamental solutions, and analytical solution. The method is easy to code, accurate, and efficient.

Average source boundary node method for potential problems

A new boundary meshfree method, named the average source boundary node method (ASBNM), is presented in this paper for potential problems. The method is based on coupling a ‘completely’ regularized boundary integral equation (CRBIE) with direct unknowns developed in this paper, removing the singularity computation, and an average source technique (AST). In this approach there are two critical developments. One is the presentation of a new removal singularity technique that results in the CRBIE, and therefore all diagonal coefficients of influence matrices can be determined analytically by the off-diagonal ones, unlike some existing boundary meshless approaches that determine diagonal coefficients from the fundamental solution by applying a known solution inside the domain, which amounts to solve the problem twice. The other is the introduction of an AST, by which the distributed source on a segment/cell can be reduced to a concentrated point source and therefore the boundary integrals in the CRBIE are not necessary. Hence, in the ASBNM only boundary nodes are required for computation without using any element or integration concept. Several test examples are presented to demonstrate the effectiveness and robustness of the proposed ASBNM.

A new boundary meshfree method for potential problems

This work presents a new boundary meshfree method, named the average source method (ASM), for solving two-dimensional potential problems. The method is based on combining a ‘completely’ regularized boundary integral equation (CRBIE) with indirect unknowns developed in this paper, removing the singularity computation, and an average source technique (AST). In this approach there are two critical developments. One is the presentation of a new removal singularity technique that results in the CRBIE, and therefore all diagonal coefficients of influence matrices can be evaluated analytically by the off-diagonal ones, unlike some existing meshless boundary approaches that determine diagonal coefficients from the fundamental solution by using a known solution, thereby doubling the solution procedure. The other is to introduce an AST, by which the distributed source on a segment/cell can be reduced to the concentrated point source and therefore the boundary integrals in the CRBIE are not necessary. Hence, in the ASM only boundary nodes are required for computation without involving any integration and element notion. Several benchmark test examples are presented to demonstrate the accuracy, convergence, efficiency and robustness of this new meshfree boundary-node methodology.

Improved non-singular method of fundamental solutions for two-dimensional isotropic elasticity problems with elastic/rigid inclusions or voids

In this work, an Improved Non-singular Method of Fundamental Solutions (INMFS) is developed for the solution of two-dimensional linear elasticity problems. The source points and field points are collocated on the physical boundary, while the conventional MFS requires a troublesome fictitious boundary outside the physical domain. In INMFS, the desingularization is, for complying with the displacement boundary conditions, achieved by replacement of the concentrated point sources by distributed sources over circular discs around the singularity, and for complying with the traction boundary conditions by assuming the balance of the forces. This procedure is much more efficient than the previously proposed procedure that involves two reference solutions and at the same time enables INMFS for solving problems with internal voids and inclusions. The method has been assessed by comparison with MFS, analytical solutions and previous desingularization technique. The method is easy to code, accurate, efficient, and straightforwardly extendable to three dimensions.

General Approach to the Evolution of Singlet Nanoparticles from a Rapidly Quenched Point Source

Among the numerous point vapor sources, microsecond-pulsed spark ablation at atmospheric pressure is a versatile and environmentally friendly method for producing ultrapure inorganic nanoparticles ranging from singlets having sizes smaller than 1 nm to larger agglomerated structures. Due to its fast quenching and extremely high supersaturation, coagulational growth already begins at the atomic scale at room temperature. On the basis of this knowledge, we develop a simple semiempirical yet versatile model for predicting the size distribution of singlet particles as a function of the process conditions. The model assumes that a plume of a turbulent aerosol flow flares out from a concentrated point source, eventually reaching the walls of the confinement where a fraction of the particles is deposited. Despite the complexity of the entire process, the concentration and size evolution of particles can be adequately described by a first-order differential equation accounting for coagulation, turbulent dilution,...