Parametric Study Research Articles

S890 hot-rolled ultra-high strength steel (UHSS) seamless circular hollow section beam–columns: Testing, modelling and design

With the recent rapid development of manufacturing techniques and material science, advanced hot-rolling of ultra-high strength steel (UHSS) with material grades up to S890 becomes possible. The structural behaviour of S890 hot-rolled ultra-high strength steel (UHSS) seamless circular hollow section (CHS) beam–columns fabricated through the advanced manufacturing method, was investigated through testing and numerical modelling and reported in this paper. In the physical testing, a total of 12 beam–columns were firstly tested featuring the flexural buckling failure mode, with the material coupon tests and initial global geometric imperfection measurements performed. FE modelling was then conducted, where the FE models were developed and validated against the test observations. The validated FE models were then adopted in the parametric studies in a wider spectrum of member lengths, cross-section dimensions and loading combinations, resulting in the additional 300 FE data to be generated. Finally, the current design provisions, as set out in Eurocode, American specification and Australian standard, are assessed for their applicability to S890 hot-rolled UHSS seamless CHS beam–columns. It was revealed from the assessment results that the design provisions in three design codes can be accurately applied to S890 hot-rolled UHSS seamless CHS beam–columns.

Feasibility on equivalence ratio measurement via OH*, CH*, and C2* chemiluminescence and study of soot emissions in co-flow non-premixed DME/C1–C2 hydrocarbon flames

The effects of dimethyl ether (DME) addition to methane and ethylene fuels on the combustion characteristics of heat release, soot emissions, and flame temperature were investigated experimentally and numerically in a non-premixed laminar flame configuration. The flame-heat release soot-volume fraction was measured experimentally using CH*, OH*, and C2* chemiluminescence and planar two-color soot pyrometry, respectively. The CH*, OH*, and C2* were used to locate flame-heat release regions as well as to investigate the soot signal’s effect on their measurements. The ratios of the chemiluminescence pairs (OH*/CH* and OH*/C2*) were studied for the feasibility of map local equivalence ratios. Numerical calculations across a full range of DME mixing ratios were performed through 1D laminar flame simulations implemented with a detailed mechanism to provide an indication of the flame structures and profiles of key species including OH*, OH, CH*, CH, CH3, C3H3, C2H2, heat release rate (HRR), and flame temperature. An existing developed soot model was used in a 2D computational study to investigate its validity for modeling soot for DME (oxygenated fuel)/C2H4/N2 flames. Parametric studies have been carried out on some key parameters in the soot model to find optimum values that can be used in future studies. Although soot radiation intensities increased at a small amount (25%vol) of DME addition in the DME/methane flames, the soot pyrometry results showed a reduced soot volume fraction with an increased DME mixture ratio in both DME/methane and DME/ethylene flames studied, agreeing with the key conclusion of 1D numerical results. The flame HRR decreases with the increasing addition of DME to methane and ethylene flames and correlates with the trend of OH* and CH* profiles. The 1D simulation showed a non-monotonic correlation between OH*/CH* ratios and equivalence ratios, implying a limited use of OH*/CH* for the equivalence ratio measurement in non-premixed flames with DME additions.

Self-rigidizable Kapton-SMA conical booms: A comprehensive numerical and experimental study

Inflatable gossamer space structures require structural rigidity after partial or complete out-gassing of the inflation gases. The current study focuses on the rigidity generation in a fully deployed, out-gassed Kapton laminated conical boom. A novel approach is applied to produce out-of-plane structural stiffness in the gossamer structure using the shape memory alloy (SMA) wires embedded between Kapton laminate membranes. The finite element analysis is performed to find the generated stiffness in the system and validated with the experimental results. To this end, an experimental set-up is developed to provide a stable and uniform thermal environment with the inflation facility. Additionally, different measuring devices are also employed in the test set-up to note the readings of pressure, temperature, and displacement sensors. Moreover, the Kapton and SMA material properties are found experimentally, and their material models are validated with published studies. Furthermore, constitutive equations of the SMA-Kapton composite are also included in the study. After that, a parametric study is done to know the effect of design and material parameters on the boom's stiffness.

Friction Stir Spot Welding of Thin Aluminium Sheets to Polyamide 6: A Study of the Welding Parameters and Strategies

The joining of aluminium alloy AA6082-T6 to polyamide 6 (PA6) by friction stir spot welding (FSSW) was investigated in the current work. Although previous studies can be found on the joining of polymers and metals by FSSW, welding using aluminium plates as thin as the ones used in this work (1 mm) was not found. The influence of the plunge depth (0.1 to 0.5 mm) and the dwell time (15 and 30 s) parameters on the welding results was studied. In general, the increase of these parameters led to the improvement of the maximum load of the joints under tensile-shear testing. Additionally, the feasibility of multiple spot welding was tested and proven. Finally, although most of the welds were performed with a pinless tool, a tool with a conical pin and a concave shoulder was used for comparison. The use of this more conventional tool resulted in joints easily broken by handling. Still, the potential of the conical pin tool was demonstrated. The different conditions were evaluated based on morphology and tensile-shear testing. The weld with the best mechanical behaviour was produced with multiple spot welding, which failed for a maximum load of about 2350 N.

A Novel Method of Boreal Zone Reforestation/Afforestation Estimation Using PALSAR-1,2 and Landsat-5,8 Data

Nowadays, global remote sensing studies of tropical forest parameters are relevant for assessing carbon sequestration, whereas boreal forests receive little attention. This is due to the current idea that forests with greater aboveground biomass absorb more carbon. However, new research indicates that rapidly growing young forests take up more carbon than mature ones. Therefore, it is necessary to develop universal methods of remote reforestation/afforestation monitoring. The existing reforestation methods rely on the separate analysis of multispectral optical images and radar data. Here, we propose a method for analyzing the joint dynamics of NDVI (or the Normalized Burn Ratio, NBR) and the radar vegetation index (RVI) on a 2D plot for a test reforestation site. NDVI and NBR time series were derived from Landsat-5,8 data, and the RVI was derived from ALOS-1,2 and PALSAR-1,2 for 2007–2020 using the resources of Google Earth Engine. The quantitative parameters to evaluate the degree of reforestation and changes in the species composition of young trees have been suggested. The suggested method enables a more thorough evaluation of reforestation by measuring the coupled dynamics of the projective cover of young trees and aboveground biomass.

On the number of subproblem iterations per coupling step in partitioned fluid‐structure interaction simulations

AbstractIn literature, the cost of a partitioned fluid‐structure interaction scheme is typically assessed by the number of coupling iterations required per time step, while ignoring the internal iterations within the nonlinear subproblems. In this work, we demonstrate that these internal iterations have a significant influence on the computational cost of the coupled simulation. Particular attention is paid to how limiting the number of iterations within each solver call can shorten the overall run time, as it avoids polishing the subproblem solution using unconverged coupling data. Based on systematic parameter studies, we investigate the optimal number of subproblem iterations per coupling step. In addition, this work proposes a new convergence criterion for partitioned algorithms that is based solely on the number of subproblem iterations required to reach the subproblem residual tolerances and therefore does not require any additional convergence tolerance for the coupling loop.

Improving Three-Dimensional Synthetic Jet Modeling in a Crossflow

Abstract Three different circular synthetic jet modeling inlet conditions are studied for a turbulent crossflow. The study examines the differences when modeling the whole synthetic jet actuators (SJA), neck-only or jet-slot-only under constant actuation frequency (f = 300 Hz), and crossflow blowing ratio (CB = 0.67). Phase-averaged and time-averaged results reveal that both whole SJA and neck-only methods generated nearly identical flow fields. For the neck-only case, a notable reduction in computational cost is achieved through the implementation of an analytical jet profile. The jet-slot-only method, on the other hand, introduces reversed flow during the ingestion cycle, leading to the injection of false-momentum into the crossflow. However, the false-momentum primarily affects the flow immediately downstream of the jet exit, with the boundary layer profile recovering rapidly. A parametric study highlights the importance of maintaining a volume ratio less than 1 of ingested to modeled neck volume to prevent the creation of false-momentum.

Improving the Flexural Response of Timber Beams Using Externally Bonded Carbon Fiber-Reinforced Polymer (CFRP) Sheets.

This paper presents a numerical investigation of the flexural behavior of timber beams externally strengthened with carbon-fiber-reinforced polymer (CFRP) sheets. At first, the accuracy of linear elastic and elastic-plastic models in predicting the behavior of bare timber beams was compared. Then, two modeling approaches (i.e., the perfect bond method and progressive damage technique using the cohesive zone model (CZM)) were considered to simulate the interfacial behavior between FRP and timber. The models were validated against published experimental data, and the most accurate numerical procedure was identified and subsequently used for a parametric study. The length of FRP sheets varied from 50% to 100% of the total length of the beam, while different FRP layers were considered. Moreover, the effects of two strengthening configurations (i.e., FRP attached in the tensile zone only and in both the tensile and compressive zones) on load-deflection response, flexural strength, and flexural rigidity were considered. The results showed that elastic-plastic models are more accurate than linear elastic models in predicting the flexural strength and failure patterns of bare timber beams. In addition, with increasing FRP length, the increase in flexural strength ranged from 10.3% to 52.9%, while no further increase in flexural strength could be achieved beyond an effective length of 80% of the total length of the beam. Attaching the FRP to both the tensile and compressive zone was more effective in enhancing the flexural properties of the timber beam than attaching the FRP to the tensile zone only.

Performance Evaluation of Inerter-Based Dynamic Vibration Absorbers for Wind-Induced Vibration Control of a Desulfurization Tower

High-rise flue gas desulfurization towers are susceptible to wind loads, which can cause instability and failure in the along-wind and across-wind directions. The tuned mass damper (TMD) has been widely applied in the wind-induced vibration control of high-rise structures. To enhance the control performance and reduce the auxiliary mass of TMD, this study focuses on inerter-based dynamic vibration absorbers (IDVAs) for controlling the vibration response of a desulfurization tower. The dynamical equations of the tower–IDVA systems are established under wind loads, and a parameter optimization strategy for IDVAs is proposed by using the genetic algorithm. The performance of the traditional TMD and six IDVAs in the vibration control of the tower are systematically compared. Numerical simulations demonstrate that both the TMD and IDVAs can substantially mitigate the vibration response of the tower. However, compared to the TMD with the same response mitigation ratio, more than 34% of the auxiliary mass can be reduced by two optimal IDVAs. In addition, the energy dissipation enhancement and lightweight effect of the two IDVAs are explained through parametric studies.

Moment Redistribution in UHPC Continuous Beams Reinforced with High-Strength Steel Bars: Numerical Investigation and Prediction Model

Considering moment redistribution in the design of ultra-high-performance concrete (UHPC) statically indeterminate structures can fully exploit the load-bearing potential of members, simplify reinforcement details, and save construction costs. Due to the excellent properties of ultra-high-performance concrete (UHPC) that distinguish it from conventional concrete, new characteristics of the moment redistribution manifest in UHPC structures. In this study, a finite element (FE) analytical model was developed to simulate and analyze the bending behavior and moment redistribution of UHPC continuous beams reinforced with high-strength steel bars. The simulation and test results exhibited excellent agreement with the experimental research. Based on the FE model, a fine analysis for nine simulated two-span UHPC continuous beams was conducted with a detailed discussion of the failure modes, load-displacement curves, variations of support reaction forces, tensile strains of steel bars, and the whole process of moment redistribution. Subsequently, the variation rules of moment redistribution in UHPC continuous beams were explored by an extensive parametric study of 108 simulated beams. The studied parameters included a neutral axis depth factor, concrete strength, yielding strength of reinforcement, beam depth, span–depth ratio, reinforcement ratio between the mid-span and intermediate support section, as well as load forms. According to the numerical results, new formulas for estimating the two-stage moment redistribution in UHPC continuous beams with high-strength reinforcement were established. Finally, a comparison of moment redistribution between normal concrete continuous beams and UHPC continuous beams was performed. It can be observed that the elastic moment distribution in UHPC continuous beams was comparatively smaller, while the plastic moment distribution was relatively larger than those of normal concrete continuous beams. Overall, the degree of the total moment distribution in UHPC structures was greater than that of normal concrete structures due to the high ductility of UHPC. The research in this study may provide a technical reference for the practical engineering of UHPC.

Sustainable system development for efficient management of waste tires through gasification and solar energy for useful outputs: A thermodynamic analysis

In this study, a solar based integrated waste tires gasification system with desalination is developed, and the respective analyses of this system are performed for multiple useful outputs, including electricity, hydrogen, fresh water as well as heat provided to the community. The thermodynamic assessment of this system is performed by using energy and exergy analyses. Moreover, both energy analysis and exergy analysis are performed for essentially investigating and evaluating the performance of the overall system. Moreover, analyses of the effects of varying operating conditions on the subsystems’ efficiencies are carried out. Both Aspen Plus and Engineering Equation Solver software packages are used for thermodynamic analyses and simulations. In this integrated system, solar energy is the prime source and utilized for producing steam. This study aims to bring up a unique solution for better resources management and sustainability. Furthermore, the waste tires are gasified to produce syngas in the designed system where both Rankine and Brayton cycles are utilized for producing electricity and heat. In addition to this, excess heat is transferred to the desalination system for producing fresh water. For improving the overall system performance, some parametric studies are performed to investigate both energy and exergy efficiencies. The energy efficiency of the integrated system is therefore calculated as 38.9 % while the exergy efficiency of this system is found to be 34.6 %. For the developed system, electricity generation and amount of heating are also calculated as 58.65 MW and 7.35 MW respectively. Moreover, the hydrogen and freshwater production capacities are determined to be 0.75 kg/s and 355.40 kg/s respectively.

Syngas-Enriched hydrogen production via catalytic gasification of water hyacinth using renewable palm kernel shell hydrochar

Syngas produced from biomass gasification has emerged as a highly promising substitute for conventional fossil fuel, catering to various industrial applications while ensuring minimal greenhouse gas emissions. Water hyacinth (WH) has been a major concern due to its invasive nature and uncontrollable growth which impedes aquatic growth and urban management. Fortunately, WH is a potential biomass feedstock due to the comparable cellulose and hemicellulose contents alongside high carbon content and high calorific value which reflects good biofuel properties. Therefore, this study aims to investigate the conversion of WH biomass via catalytic air gasification for syngas-enriched hydrogen production using palm kernel shell hydrochar (PKSH). A parametric study was conducted in a lab-scale fixed-bed downdraft gasifier based on the response surface methodology coupled with Box-Behnken design (RSM-BBD). The combined interaction effects of the influencing parameters investigated are temperature (600–800 °C), biomass particle size (2–6 mm), catalyst loading (0–10 wt%), and air flow rate (1–3 L/min). Temperature was revealed to be the primary factor with significant influence on the H2 and CO output. Maximum syngas (30.09 vol%) compositions of 11.14 vol% H2 and 18.95 vol% CO were obtained at 800 °C with a particle size of 6 mm and air flow rate of 2 L/min alongside 5 wt% PKSH catalyst loading.

On wave propagation in nanobeams

Wave propagation in Rayleigh nanobeams resting on nonlocal media is investigated in this paper. Small-scale structure-foundation problems are formulated according to a novel consistent nonlocal approach extending the special elastostatic analysis in Barretta et al. (2022). Nonlocal effects of the nanostructure are modelled according to a stress-driven integral law. External elasticity of the nano-foundation is instead described by a displacement-driven spatial convolution. The developed methodology leads to well-posed continuum problems, thus circumventing issues and applicative difficulties of the Eringen–Wieghardt nonlocal approach. Wave propagation in Rayleigh nanobeams interacting with nano-foundations is then analysed and dispersive features are analytically detected exploiting the novel consistent strategy. Closed form expressions of size-dependent dispersion relations are established and connection with outcomes available in literature is contributed. A general and well-posed methodology is thus provided to address wave propagation nanomechanical problems. Parametric studies are finally accomplished and discussed to show effects of length scale parameters on wave dispersion characteristics of small-scale systems of current interest in Nano-Engineering.

Highly selective conversion of toluene to acetylene for upcycling by a plasma process

The electrification of diverse chemical processes with renewable electricity is considered to be an attractive solution to the issue of global warming, which is becoming continuously more severe. Plasma can be an effective supplier of heat during electrification. Here, we achieve a highly selective conversion of toluene (C7H8) to acetylene (C2H2) using rotating-arc plasma, which is a capable means of upcycling industrial waste into value-added materials. Compared to other processes involving treatment or oxidation to eliminate low concentrations of C7H8, the proposed approach shows the conversion of high concentrations of C7H8 to C2H2. Based on parametric studies on the effect of the residence time, specific energy input, reactant concentration, and simulation, the highest reported C2H2 selectivity and energy efficiency are obtained. The results suggest that plasma can act as an effective source of thermal activation and rotating-arc plasma can be a promising means to achieving electrification in the chemical industry.

Biomass gasification in rotary kiln integrated with a producer gas thermal cleaning unit: An experimental investigation

In this work, gasification of hazelnut shells grains is carried out in a bench-scale rotary kiln by using air as gasifying agent at 800 °C. The producer gas is directly treated in a thermal cleaning unit operating at 800–1100 °C with the aim to reduce the load of contaminants. The producer gas cleaning by thermal methods is usually studied by using model compounds, whilst herewith the behavior of a real producer gas is investigated. Results indicate that at high temperature CO2 reacts with tar and particulate to generate CO, thereby improving the quality of producer gas in terms of heating value, producer gas yield and contaminants content. Benzene is the most abundant organic contaminant of the producer gas, the concentration of which is significantly reduced upon thermal treatment. For the first time, a bench-scale rotary kiln gasifier with lignocellulosic biomass as feedstock is integrated with a thermal cleaning unit, providing experimental evidences about the suitability of rotary kiln for air gasification of lignocellulosic biomass and its integration with a thermal unit. The proposed approach could find application also when other types of gasifier are adopted, although a parametric study should be carried out in order to fully understand the reaction mechanism of contaminant removal and to find optimal operation conditions, also as a function of biomass feedstock features.

A parametric study of a bolted joint rotor-bearing system with an unbalanced offset disk

The turbine disk is the core component of an aero-engine whose position and unbalanced force seriously affect the vibration stability of the rotor system. Ignoring the influence of the offset disk may result in discrepancies between real-world scenarios and numerical simulation results. The present work aims to explore the nonlinear dynamic characteristics of rotor systems under the coupling of bolted joint and offset disk effect, as well as the influence of offset disk position and its unbalanced force on the system dynamic behavior and bending stiffness of bolted joint also investigated. The governing equations of a bolted joint rotor-bearing system with an offset disk were established based on the finite element method and derived as a dimensionless expression in the first. Then, the Newmark method was employed for the numerical solution of the motion equations, and then a bifurcation analysis of the rotor system and the evolution of bending stiffness for the bolted joint was studied. Next, by comparing the frequency-amplitude diagrams, bifurcation diagrams, time history, shaft obits, and bending stiffness diagrams of the bolted joint, the effect of the offset disk position and its unbalanced force on the nonlinear system dynamic was revealed. Finally, an experimental study was carried out to verify the numerical result using the bolted joint rotor test rig with an offset disk. The analysis result of the present work can provide theoretical guidance for structure design and stability analysis on the aero-engine.

Adiabatic compressed air energy storage system combined with solid-oxide electrolysis cells

Green hydrogen from electrolysis using renewable energy is becoming increasingly important and competitive because of the rapid decrease in the price of electricity from solar photovoltaic (PV) and wind power. Electrical energy storage (EES) can reduce the installation capacity of electrolyzers owing to their steady and continuous operation. Adiabatic compressed air energy storage (A-CAES) systems can be effectively combined with large scale solid-oxide electrolysis cells (SOEC) for low-cost production of hydrogen. Although the round-trip efficiency of the power-only A-CAES (70–75%) is lower than that of batteries (90%), the A-CAES system can be used as a combined cooling, heat and power (CCHP) system, providing heat and power to SOEC in order to maximize the energy efficiency of the system. This paper presents a parametric study of an A-CAES system combined with an SOEC system in terms of the energy and exergy analyses. The results show that a medium-temperature trigeneration CCHP A-CAES system in combination with a SOEC system with a compression power of 100 MWh can provide 47.8 MWh of electric power and 63.5 MWh of heat to the SOEC system as well as 9.9 MWh of cold energy from the cold outlet air of the A-CAES.

Uniformly distributed FeVO4 nanocuboids on exfoliated rGO facilitated by supersonic spraying for wearable supercapacitors

High-energy–density supercapacitors exhibiting high power density and long-term stability are essential devices for energy storage applications, such as wearable electronics. In this study, we utilized supersonic spray deposition to exfoliate reduced graphene oxide (rGO). Additionally, a solvothermal process was employed to engineer the nanostructure of iron/vanadium oxides. Consequently, the resulting multivalent iron/vanadium oxide and rGO composites exhibited remarkably high energy densities. Three major parametric studies were conducted to investigate the electrochemical properties of iron oxide (FO), vanadium oxide (VO), and iron/vanadium oxide (FVO) composites with rGO. FVO/rGO emerged as the most promising sample, exhibiting an areal capacitance of 1240 mF·cm−2 at a current density of 2 mA·cm−2, as well as achieving a 90 % capacitance retention even after 8000 galvanostatic charge–discharge cycles. Furthermore, this sample delivered an energy density of 0.17 mWh·cm−2 at a power density of 4 mW·cm−2.

Experimental and numerical exploration for the design of swift-constructed demountable blind bolts

In this study, a new type of blind bolt that combines high tensile resistance and stiffness with easy and fast installation and demounting capabilities is proposed, named Swift-Constructed Demountable Blind Bolt (SCDBB). The components, intended working mechanism, and fabrication process are first introduced. Geometric constraints of critical components are then derived based on the desired behaviour. To study the performance of SCDBBs under tensile loading and their behaviour during the installation process, 9 experimental tests were conducted. Two failure modes, namely, bolt shank fracture and buckling of the expansion nut blades, were revealed when subjected to maximum tensile loading. Subsequently, finite element (FE) models were developed and validated by comparing the numerical results with the experimental data. To further explore the impact of key design parameters on the behaviour of the bolts under tensile loading and performance during installation, parametric studies consisting of 106 FE models were conducted for bolts of three sizes with variations in four key design parameters. The findings indicate that the failure modes under maximum tensile loading and maximum installation force are sensitive to the length, thickness, and gap of the elastic expansion nut. The optimised ranges for each design parameter were identified to prevent undesirable blade buckling.

Structural Analysis and Finite Element Methods: Modeling and Simulation in Mechanical Engineering

This research dives into the space of "Structural Analysis and Finite Element Methods: Modeling and Reenactment in Mechanical Designing," utilizing a multifaceted approach to comprehensively get the mechanical behaviour of building structures. Finite Element Analysis (FEA) was utilized to scrutinize a steel structure beneath assorted stacking conditions, uncovering stretch conveyances basic for basic optimization. The study amplified its centre to Fluid-Structure Interaction (FSI), unravelling the complex flow between liquid forces and basic reactions, with suggestions for seaward building applications. Warm recreations of composite materials give bits of knowledge into temperature-induced stresses, directing fabric choice and plan alterations in extraordinarily warm situations. Sensitivity investigations and parametric studies methodically investigated plan impacts on auxiliary execution, helping in optimization endeavours. Approval against experimental information guaranteed the precision of numerical recreations, improving their validity.