Computational Parametric Study Research Articles

Matrix curing and stress field development around fiber during the solvent evaporation-induced repolymerization of recycling composites

When recycling fiber-reinforced composites using depolymerized polymer solutions, oligomers reconnect through covalent bond exchange reactions (BERs), which ultimately forms a crosslinked network with mechanical properties comparable to those of virgin materials. This process offers exciting opportunities for the primary recycling of engineering composites, but it is intricately influenced by a few material and process parameters, such as heating temperature, duration, and fiber volume fractions. These parameters collectively determine the matrix's curing degree and the evolution of stress fields around the fiber, which are significant factors determining the quality and mechanical performance of recycled composites. This study introduces a diffusion-reaction-mechanics finite-element computational model to examine the solvent-induced repolymerization process in recycling composites. The model predicts the matrix curing degree, residual stress development around the fiber, and the composite's mechanical properties, aligning with experimental results. Parametric computational studies are then conducted to assess the influences of temperature, fiber content, solvent diffusivity, and the reactivity of BERs. The objective is to identify material and processing conditions that ensure efficient composite recycling while minimizing the development of residual stress. Overall, this study enhances our understanding of the mechanisms behind composite recycling using organic solvents and provides valuable insights for industrial stakeholders looking to optimize processing conditions and advance the commercialization and widespread adoption of this innovative recycling technique.

Impact of building porosity on exterior convective heat transfer coefficients: An experimental and computational parametric study

Exterior convective heat transfer is vital for connecting a building and its surrounding environment. With an increasing focus on porous buildings for sustainable design, accurately calculating exterior convective heat transfer is critical, and also poses significant challenges. This study used experimental and computational fluid dynamics (CFD) techniques to assess the impact of building porosity on exterior CHTCs. Onsite measurements at an actual porous building were conducted first for validation, which was further extrapolated by linking the actual porous building with idealized porous buildings. Parametric CFD simulations were then performed on hypothetical isolated buildings with ten different idealized geometries (including one fully enclosed building as a baseline and nine porous buildings) and two wind directions (perpendicular and oblique). The resulting exterior CHTCs obtained through CFD simulations were compared with those from exterior CHTC models in EnergyPlus, along with the resulting differences in cooling load. The findings revealed that the maximum difference in exterior CHTCs between CFD simulations and exterior CHTC models in EnergyPlus was nearly threefold, leading to cooling load deviations of up to 19%. From a practical perspective, this study highlights the impact of building porosity on exterior convective heat transfer, underscoring the importance of considering building porosity in building energy simulation for more accurate cooling load prediction.

A computational parametric study of ducted fuel injection implementation in a heavy-duty diesel engine

Experiments have shown that ducted fuel injection (DFI) effectively reduces soot emissions from direct-injection diesel engines. Although many computational studies have evaluated DFI’s spray development and soot reduction mechanisms in constant volume chambers, only limited computational work on internal combustion engines exists. The DFI duct assembly changes the engine’s in-cylinder flow, spray, and combustion development. Therefore, current production engine designs might not be optimal for achieving the best engine performance with DFI. This work conducted an extensive numerical study to evaluate how parameter changes affect DFI performance. The parameters include swirl ratio, piston geometry, compression ratio (CR), number of injector orifices, split injection strategy, and exhaust gas recirculation (EGR) in a heavy-duty diesel engine utilizing DFI. The combustion and soot emission data from the Sandia compression ignition optical research engine were used for model validation. Simulations showed that an increased swirl ratio resulted in more intense jet flame-piston interaction, slowing down the combustion heat release during the late combustion stage and leading to lower indicated thermal efficiency (ITE) due to higher exhaust losses. A piston-bowl design with a reentrant inner piston edge yielded the highest thermal efficiency, due to the reduced cylinder head heat transfer loss. Additional injector orifices led to higher efficiency owing to a more advanced combustion phasing. Nevertheless, the maximum pressure rise rate (MPRR) and oxides of nitrogen (NOx) emissions also increased with the number of injector orifices due to more rapid heat release and higher combustion temperature. Implementation of a split injection strategy combined with a higher EGR rate effectively inhibited the excessive MPRR and NOx formation. In general, the study concluded that DFI is not sensitive to most parameter changes but will benefit from future parameter optimization.

Development of the tied butterfly shape for structural fuses

Recently, there has been research and interest in structural fuses as a way to concentrate seismic damage in replaceable elements and protect the rest of the structure from inelastic actions. However, there is no consensus on structural fuse shape, particularly for structural fuses consisting of a steel plate subjected to shear deformations, because studies with different objectives arrive at different shapes. For example, studies seeking to optimize the structural fuse shape to maximize fracture resistance often result in something that looks like the butterfly-shaped link, whereas other studies that optimize the form to maximize buckling resistance result in a shape with links that are tied together. In this study, a new structural fuse shape, named the tied butterfly shape, was developed to integrate the advantages of both the buckling-resistant configuration and the butterfly-shaped link. First, the concepts for the tied butterfly shape are presented along with plastic mechanism analysis to derive an equation for shear strength. Then, an experimental program is described including three tied butterfly shape structural fuses and one straight link structural fuse for comparison. Finite element models are then validated against the experimental results and a parametric computational study is presented that evaluates the effect of key design variables on the structural behavior of this tied butterfly shape. The experimental study revealed that the tied butterfly shape structural fuse was capable of maintaining stable hysteretic behavior up to a shear angle of 23% before fracture or buckling and that multiple tied butterfly shapes can be connected together. Based on the plastic mechanism analysis and parametric study, design equations and recommendations for implementation in practice are provided.

Parametric Enhancement of a Window-Windcatcher for Enhanced Thermal Comfort and Natural Ventilation

Window-windcatchers, a passive ventilation method, have been shown to improve ventilation and enhance thermal comfort. Preliminary characterization of a novel window-windcatcher has been undertaken in a previous work, but no relationship had been identified between the actual ventilation rate (Qact), the wind velocity (VTw) and crucial design parameters such as the fins angle (ϴ)). In this paper, the relationship that quantifies how the window-windcatcher’s performance depends on VTw and ϴ was determined. Additionally, for the first time, the ventilation performance of the window-windcatcher was optimized by studying the effects of ϴ and the fins-wall distance (DW−f) through a Computational Fluid Dynamics parametric study (ANSYS)|. In this optimization approach, the angle ϴ and the distance DW−f corresponding to the maximum actual-to-required ventilation rate were found to be 80° and 45 cm, respectively. The actual ventilation rate increased by approximately 13.2% compared with the baseline design of the windcatcher (ϴ and DW−f equal to 40° and 45 cm, respectively); this corresponds to an increase of approximately 8.6% in the actual-to-required ventilation rate, according to the ASHRAE standards.

Twist Blade Distributor in Fluidization Systems: Part 1 – The Computational Procedure

Flowing gas in fluidized bed through selected inlet distributor may imparts a drag effect on the particles, would cause an increase in gas flow, that maybe sufficient to rearrange the particles movement. Thus, study on the airflow in a fluidization system through numerical analysis has been conducted to investigate the airflow distribution affected by new model distributor of twist blade distributor configuration. The present study would emphasis on computational procedure and parametric study via ANSYS Fluent before a detailed study on selected twist blade distributor are conducted. The selected parametric study on the twist blade distributor configuration whereby the twist blade angle (100°), horizontal inclination angle (15°), radial inclination angle (10°) and number of blades (60) was carried out. Therefore, the results of the studies that have been carried out meet the expected standards based on previous studies.

Multicomponent numerical model for heat pump control with low-temperature heat storage: A benchmark in the conditions of Central Europe

This paper presents a computational parametric study on increasing the Seasonal Coefficient of Performance for residential heat pumps, utilizing an enhanced computational model and comparing it to previous research. The model computes a system that consists of a heat pump, low-temperature heat storage, heat exchanger and circulation pump, and a control unit which allows the heat pump to choose either low-temperature heat storage or ambient air as the favorable heat source. A parametric study is conducted to obtain results from a numerical model describing in detail the heat storage, surrounding soil, and the behavior of a water tank with and without temperature stratification and with two different geometries. These are combined into three different systems. Each system uses an algorithm for heat pump control that combines equithermal regulation and deferred heat storage discharging based on long-term temperature trends. Python is used to transform the numerical model into a computational model, and the assessment of heat pump operation is made based on meteorological data from the years 2012–2021 recorded in the city of Brno, Czech Republic, Central Europe. Previous studies have suggested that this combination for heat pump control and a more detailed numerical model of the system should result in a SCOP increase. In this study, heat losses of an actual occupied building with floor area of 140 m2 without considering heat radiation are used. The results show that stratification cannot be omitted for numerical modelling, and that the geometry of the storage influences how the storage should be designed. For a wide and shallow storage, it is better to insulate the system and increase the SCOP from 3.8 to 4.65, but non-insulated deep and narrow storage can increase the from 3.8 to 4.95. Flow rate is also an important parameter with a local maximum between 0.01 and 0.02 kg/s for every cubic meter of the storage. When a system consisting of parts readily available on the market is used at optimal conditions, the resulting increase can be from 11.8% up to as high as 25.7% with low-temperature heat storage ranging from 9 to 25 cubic meters.

Computational and experimental study of structural fuses optimized to resist buckling

The concept of structural fuses, i.e., replaceable hysteretic dampers that limit the forces that can be transferred to the surrounding structure, has been used in research and practice to improve the seismic performance of structural systems. A recent study used topology optimization to develop new structural fuse shapes that discourage buckling and promote stable yielding of shear-acting structural fuses. The objective of the current study is to further validate and develop the optimized shapes to allow the design and application of these optimized structural fuse shapes in practice. First, the pixelated optimized topology was interpreted as a collection of geometric shapes, parameterized to make it accessible for design, and plastic mechanism analysis was used to develop a generalized equation for shear strength. An experimental study was conducted on three specimens that were 711 mm by 762 mm by 25 mm thick, to evaluate strength, stiffness and hysteretic behavior. Finite element models were then validated against the experimental results, and used to conduct a computational parametric study to evaluate the effect of varying key design parameters on strength, stiffness, out-of-plane buckling, effective plastic strain, and energy dissipation. The experimental study showed that one of the optimized geometries possessed a good balance between buckling resistance and fracture resistance reaching approximately 11% shear angle without either. Design guidance is provided for this topology including a parameterized method for reproducing the shape, design equations, and recommendations for proportioning.

Computational fluid dynamics-based parametric study on the performance of solar air heater channel.

Computational fluid dynamics (CFD) plays a prominent role in the design and development of solar air heaters. The previous investigations have lagged in using a radiation model for the solar heat input; instead, most of the researchers simulated a constant heat flux model. Moreover, an extensive study on the geometrical and boundary conditions like confinement and transition length, suction, and blowing effects has not been studied. The present investigation deals with the aforementioned effects on the flow and heat transfer characteristics of the SAH channel, which is designed for residential space heating. The finite volume-based solver Ansys Fluent is used for finding the field variables. The confinement height is varied from 25 to 150mm, and the transition length is varied from 250 to 1000mm. The suction and blowing effect is investigated by changing the flow direction across the channel. Even though the temperature rise is less significant with respect to confinement height and transition length, the effective efficiency increases with decreasing channel height and increasing transition length. In general, blowing of air across the channel gives better performance than suction. When comparing them, the influence is less in temperature rise and more in pressure drop for the channel height of 25mm, whereas the channel height of 150mm has better influence in temperature rise and less influence in pressure drop.

Inlet air fogging strategy using natural gas fuel cooling potential for gas turbine power plants

Fogging is an effective cooling system used for gas turbine (GT) inlet air cooling. In this study, three fogging strategies were tested: direct fogging, fogging with a natural gas (NG) heat exchanger (FNGE), and FNGE using a storage tank (FNGET). The discrete phase model (DPM) with the standard k-ω turbulence model was used. A computational parametric study was conducted using the standard k-ω turbulence model on a GT compressor inlet duct to optimize the effect of the FNGET cooling strategy. The effects of duct length, number of nozzles, uniform droplet diameter, and nozzle angle on the compressor inlet air temperature and relative humidity (RH) were examined in this parametric study. A duct with 15 m length, 48 nozzles in each half, 100 μm droplet diameter, and 60° nozzle angle exhibited the maximum decrease in the temperature of the compressor inlet air. The minimum (maximum) reduction in temperature was 5.54 °C (15.77 °C), which was observed at 30 °C (40 °C) ambient dry-bulb temperature (DBT) and 60% (15%) RH. The minimum (maximum) increase in the GT output power was 8.99 MW (26.44 MW), or 3.87% (11.15%), which was under the ambient conditions of 34 °C (30 °C) and 60% (15%) RH. The maximum enhancement in GT thermal efficiency was 1.47%, which occurred under the ambient conditions of 30 °C DBT and 15% RH. The maximum decrease in GT specific fuel consumption (SFC) was 4.30%, which was seen under the ambient conditions of 30 °C and 15% RH. FNGET was the most effective cooling strategy in terms of GT output power, thermal efficiency, and SFC. This novel cooling strategy can be applied to various GT models.

Computational Parametric Study on Full-Scale Ultimate Tested Dynamic Message Sign with Welded Connections

AbstractTransportation industries have commonly used welded connections in the production of dynamic message signs (DMSs) for several years. Even though with numerous alternatives such as bolt/rive...

Design strategy of axial slot casing treatment for a transonic compressor rotor based on parametric analysis

An unsteady computational parametric study of the axial slot casing treatments (ASCTs) is performed in a tip-critical transonic rotor. Other than previous practices of considering the compressor overall performance as the design target directly, this paper takes the recirculation flow inside the slot cavity as the bridge to link the overall performance with geometric parameters of ASCT. The recirculation flow has a compound effect on the rotor tip flow field, leading to a significant influence on compressor stability and efficiency. Thus, a design strategy is proposed to improve the ASCT effectiveness based on recirculation flow control. Firstly, the study of the relationship between the recirculation flow and the ASCT effectiveness is carried out on a single rotor row with a standard semi-circular ASCT. The recirculation is quantitatively described by crucial recirculation parameters, the injection flow rate, the injection axial momentum, and the injection angle. The influence of these parameters on stall margin and efficiency is clarified through analyzing the tip region axial momentum and flow losses at design and near stall point. Then, the geometry of ASCT is characterized by three key parameters: the axial position, the open area ratio, and the skew angle. According to the parametric study, the variations of recirculation parameters with the slot geometric parameters can be quantitatively analyzed. Consequently, the influence mechanisms of geometric parameters on ASCT effectiveness are elucidated from the perspective of recirculation flow. Based on the above understanding, the effectiveness of ASCT can be improved by changing the geometric parameters to redesign the recirculation parameters. Finally, a new semi-circular ASCT configuration is improved by this strategy. The numerical results show that compared with the standard configuration, the new ASCT configuration increases the stall margin from 7.38% to 15.81% with almost the same peak efficiency.

Steel Structures Research Update: Seismic Performance of Nonorthogonal Special Moment Frame Beam-to-Column Connections

Ongoing research on the seismic behavior of nonorthogonal special moment frame beam-to-column connections is highlighted. Featured is a comprehensive experimental and computational study under way at the University of Arkansas and led by Dr. Gary Prinz, Associate Professor in Structural Engineering. The research team includes PhD students Hossein Kashefizadeh and Damaso Dominguez. Dr. Prinz’s research interests include mechanics and simulation of ductile fracture, seismic design solutions for steel structures, and computer simulation of structures under dynamic loading. He received a National Science Foundation Faculty Early Career Development (CAREER) award to investigate a new micromechanics-based approach to ductile fracture simulation in additively manufactured steels for improved seismic structural fuse design. Dr. Prinz has also been awarded AISC’s Milek Fellowship. The four-year Milek Fellowship is supporting this research on the seismic performance of skewed special moment frame (SMF) connections. The research team is partway through the third year of the four-year study. Selected results from the computational parametric study are highlighted along with a preview of the experimental investigation.

Influence of control strategy on seasonal coefficient of performance for a heat pump with low-temperature heat storage in the geographical conditions of Central Europe

This paper presents a computational parametric study on increasing the Seasonal Coefficient of Performance (SCOP) for residential heat pumps. The studied system consists of a heat pump, low-temperature heat storage, and a control unit. The heat pump enables selection of a low-temperature heat source between ambient air and water in a tank. Two variants of low-temperature heat storage are tested, particularly, insulated-water heat storage and water heat storage sunken in soil. The study is further complemented with a test of selected algorithms for heat pump control: equithermal regulation, a binary algorithm for temperature source selection, a predictive algorithm for the heat storage discharging, and an algorithm for deferred heat storage discharging. A computational model of the system is made using Python. The assessment of HP operation is made based on meteorological data from the years 2008–2019 recorded in the city of Brno, Czech Republic, Central Europe. The results obtained show that using the approaches tested has the potential for increasing the SCOP. This increase reaches as much as 5.19% and it requires only a simple software change in the heat pump control algorithm and connection to meteorological data prediction.

Steel-Concrete Composite Beams with Precast Hollow-Core Slabs: A Sustainable Solution

Industrialization of construction makes building operation more environmental friendly and sustainable. This change is necessary as it is an industry that demands large consumption of water and energy, as well as being responsible for the disposal of a high volume of waste. However, the transformation of the construction sector is a big challenge worldwide. It is also well known that the largest proportion of the material used in multistory buildings, and thus its carbon impact, is attributed to their slabs being the main contributor of weight. Steel-Concrete composite beams with precast hollow-core slabs (PCHCSs) were developed due to their technical and economic benefits, owing to their high strength and concrete self-weight reduction, making this system economical and with lower environmental footprint, thus reducing carbon emissions. Significant research has been carried out on deep hollow-core slabs due to the need to overcome larger spans that resist high loads. The publication SCI P401, in accordance with Eurocode 4, is however limited to hollow-core slabs with depths from 150 to 250 mm, with or without a concrete topping. This paper aims to investigate hollow-core slabs with a concrete topping to understand their effect on the flexural behavior of Steel-Concrete composite beams, considering the hollow-core-slab depth is greater than the SCI P401 recommendation. Consequently, 150 mm and 265 mm hollow-core units with a concrete topping were considered to assess the increase of the hollow core unit depth. A comprehensive computational parametric study was conducted by varying the in situ infill concrete strength, the transverse reinforcement rate, the shear connector spacing, and the cross-section of steel. Both full and partial interaction models were examined, and in some cases similar resistances were obtained, meaning that the same strength can be obtained for a smaller number of shear studs, i.e., less energy consumption, thus a reduction in the embodied energy. The calculation procedure, according to Eurocode 4 was in favor of safety for the partial-interaction hypothesis.

Computational parametric study on efficiency of low boiling point fluid plants under heat exchange process intensification

One of the main challenges for the energy industry is to improve the reliability and efficiency of heat exchange equipment in heating plants. Phase-change heat exchangers with low boiling point fluid (LBPF) are widely used in both conventional and renewable energy. The main objectives of increasing the efficiency of heat exchange equipment are to reduce the weight and dimensions, to increase the amount of heat transferred and to reduce the electricity consumption spent on pumping the heat transfer agent. These objectives are achieved by implementing various methods of heat exchange intensification in heat exchange equipment. A key aspect concerning application of various types of heat exchange intensifiers in heat exchange equipment is evaluation of possibility to increase their design efficiency. The paper presents the results of a computational parametric study of changes in efficiency of some LBPF-based plants when intensifying heat exchange processes by modifying functional surfaces of heat exchangers by laser ablation.

Computational parametric study for plastic strain localization and fracture in a polycrystalline material with a porous ceramic coating

Polysilazane-based ceramic coatings have ever-increasing applications in critical and high-power engineering. This paper analyzes the effects of the substrate grain size, the curvature of the coating-substrate interface and the pore-free coating layer on the plastic strain localization and fracture of the porous ceramic coating–polycrystalline substrate structures under compressive loading applied to the coated surface. Models for generating pore and polycrystalline structures of the coating and substrate are developed, with the experimentally observed microstructures of the coated steel being taken into account in calculations explicitly as the initial data of the boundary-value problem. Numerical results obtained by the finite-difference method show that the crack-initiation strain depends on the substrate grain size exponentially. A comparison between the models with serrated and plane coating-substrate interfaces suggests that in the former case, coating cracking initiates near the humps of the interface concavities and the top and bottom pore surfaces, while in the latter case, two sites of cracking nucleation can be distinguished, namely, close to the pores – in the fine-grained substrate, and near the coating-substrate interface – in the case of coarse grains. The results indicate that it is preferable to use the coated specimens characterized by a serrated coating-substrate interface.

Parametric investigation on the design of RBS moment connections with jumbo beams and columns

Recent experiments demonstrated that reduced beam section moment connections with some of the largest hot-rolled beam and column shapes (jumbo shapes) may not have sufficient ductility for high seismic applications if designed according to current design procedures. A parametric computational study was performed to evaluate potential changes to the design procedures to enhance the ductility of these connections with jumbo shapes. First, three-dimensional finite element models were developed and calibrated to match cyclic experimental results including load vs displacement response, panel zone deformations, and deformed shape. The models were then used to conduct parametric studies with inelastic monotonic loading to examine the effect of design parameters including beam flange reinforcing fillet weld size, panel zone strength and doubler plate location on fracture potential. The results showed that the size of the reinforcing fillet weld on the underside of the bottom flange has a significant impact on the local stresses and strains at the location of fracture initiation in the tests and that larger size fillet welds should be used with jumbo beams to mitigate the concentration of inelastic strains. The results also showed that joints with higher panel zone strengths lead to lower fracture potential and that moving the column web doubler plate outwards to the edge of the flange is another effective strategy to reduce local strain concentrations. The absence of local buckling in jumbo sections eliminates the strength degradation that limits demands on the welds and needs to be taken into consideration in their design.

Mitigating intensity of urban heat island by better understanding on urban morphology and anthropogenic heat dispersion

Anthropogenic heat is one of the key factors that causes intensive Urban Heat Island (UHI) due to its direct impact on ambient temperature in urban areas. Stagnated airflow due to closely packed tall buildings causes weak dilution and removal of anthropogenic heat. Consequently, research is critically needed to investigate the effect of urban morphology on anthropogenic heat dispersion and provide effective planning strategies to reduce UHI intensity, especially at the extreme scenarios, such as with very low wind speed and high heat emission. This study provides scientific understanding and develops a Geographic Information System (GIS)-based modelling tool to support decision-making in urban planning practice. We start from a computational parametric study at the neighbourhood scale to investigate the impact of urban morphology on heat dispersion. Site coverage ratio and frontal area density are two urban morphological parameters. Ten parametric cases with two heat emission scenarios are designed to study representative urban areas. Furthermore, based on the energy conservation within urban canopy layers, we develop a semi-empirical model to estimate spatially-averaged in-canopy air temperature increment, in which the exchange velocity between street canyons and overlaying atmosphere is estimated by the Bentham and Britter model. The performance of new model is validated by cross-comparing with Computational Fluid Dynamics (CFD) results from the parametric study. By applying this new model, the impact of anthropogenic heat on air temperature is mapped in residential areas of Singapore for both long-term annually averaged and short-term extreme low wind speed to improve urban climate sustainability and resilience.

Computational Analysis of Turbulent Hemodynamics in Radiocephalic Arteriovenous Fistulas to Determine the Best Anastomotic Angles

Hemodynamics has been known to play a major role in the development of intimal hyperplasia leading to arteriovenous fistula failure. The goal of our study is to investigate the influence of different angles of side-to-end radiocephalic anastomosis on the hemodynamic parameters that promote intimal dysfunction and therefore intimal hyperplasia. Realistic three-dimensional meshes were reconstructed using ultrasound measurements from distal side-to-end radiocephalic fistulas. The velocity at the proximal and distal radial inflows and at specific locations along the anastomosis and cephalic vein was measured through duplex ultrasound performed by a single examiner. A computational parametric study, virtually changing the inner angle of anastomosis, was performed. For this purpose, we used advanced computational models that include suitable tools to capture the pulsatile and turbulent nature of the blood flow found in arteriovenous fistulas. The results were analyzed in terms of velocity fields, wall shear stress distribution, and oscillatory shear index. Results show that the regions with high oscillatory shear index, which are more prone to the development of hyperplasia, are greater and progressively shift toward the anastomosis area and the proximal vein segment with the decrease of the inner angle of anastomosis. These results are specific to distal radiocephalic fistulas because they are subject to proximal and distal radial inflow. The results of this study show that inner anastomosis angles approaching 60-70° seem to yield the best hemodynamic conditions for maturation and long-term patency of distal radiocephalic fistulas. Inner angles greater than 90°, representing the smooth loop technique, did not show a clear hemodynamic advantage.