Flow Spreading Research Articles

Experimental study on buildability and mechanical properties of 3D printing cob

The application of 3D printing technology to earth buildings conforms to the development concept of low carbon, green and intelligent construction. The key issue lies in the development of earth material with both favorable buildability and sufficient mechanical properties. In this study, the printing parameters of mixture for 3D printing with different water contents were optimized. The optimum water content of 3D printing cob was determined based on the buildability. The result shows that when the flow spreading diameter is between 140 mm and 160 mm, 3D printing cob has good buildability performance. The optimum water content is 24.6 %. In addition, anisotropic performance was analyzed by compressive strength tests from three orthogonal directions. In particular, according to the test results of single printing limit height and yield stress, the buildability of 3D printing cob wall was analyzed. The building strategy of the printing divided into multiple times was obtained.

Trajectory and spreading of falling circular dense jets in shallow stagnant ambient water

This study investigates the trajectory and spreading of a horizontal circular dense jet flow discharged above the water surface, the flow of which falls into shallow stagnant ambient water. For this purpose, 27 experiments were performed using three diameters, flow rates, and falling heights to investigate jet trajectory. In addition, nine experiments with constant falling height were conducted to study jet spreading. The densimetric Froude number of the jet flow at the nozzle outlet and water surface of the present study ranged from 0.72 to 4.22 and 36.96 to 86.10, respectively. The data pertaining to this study were extracted and analyzed through image processing. The results of the experiments showed that by increasing both the momentum and falling height, the trajectory of the jet flow reached a farther distance from the discharge nozzle. The spreading of the outer boundaries of the dense circular falling jet flow tended to extend downstream of the impact point and had an elliptical motion on the bed. The relationship between radial distance from the impingement point to the outer boundary of flow and time was determined to have a power of 0.67 for flow along the flume and 0.59 for flow along the flume's width.

Prediction of retrogressive landslide in sensitive clays by incorporating a novel strain softening law into the Material Point Method

Sensitive clays, when subjected to large strains, exhibit a unique strain-softening behavior, transforming into a remolded liquid with remarkably low shear strength. When a slope fails, this behavior leads to the remolded clay moving away from its original position, triggering subsequent failures and catastrophic outcomes. To accurately predict such scenarios, it is crucial to incorporate realistic strain-softening characteristics into the constitutive soil model. This paper presents a novel yet practical strain-softening law developed by the authors that effectively captures the post-peak behavior of sensitive clays down to their remolded strength. The softening law is implemented in an elastoplastic Mohr-Coulomb model and incorporated into Anura3D, an open-source software that uses the Material Point Method to simulate large deformations. The constitutive model is calibrated by simulating the stress-strain behavior through direct shear tests conducted at three sensitive clay landslide locations. The accuracy of the overall numerical framework is assessed by predicting the post-failure movements of these landslides. Notably, two of the landslides, Sainte-Monique (1994) and Saint-Jude (2010), have previously been analyzed using other numerical tools, allowing for a comparative analysis with the method presented here. The third landslide, the Saint-Luc-de-Vincennes landslide, representing a composite flow slide and spread, has been numerically simulated for the first time. The post-failure behavior observed in the landslide events is compared with field observations and other numerical analyses. The results show that the MPM models with the proposed strain-softening law can reasonably predict post-failure retrogression and runout distance, which are crucial parameters for determining the risk of landslides in sensitive clays.

Numerical simulation of solidification of molten slag impacting inclined wall in boiler based on smoothed particle hydrodynamics method

In order to study the process of high temperature liquid slag impinging on the wall, the slagging phase change is produced by combustion of high alkali coal in a boiler chamber. In this paper, based on the smoothed particle hydrodynamics (SPH) method, the flow spreading and solidification model of slag particles hitting the inclined wall are established, and the dynamic process of flow spreading and the phase change of slag particles hitting the wall are analyzed by simulating the deposition process of the phase change of slag particles hitting the wall. The effects of different inclination angles of the wall on its deformation and solidification heat transfer are further discussed. It is shown that the change of inclination angle during the impact of single slag on the wall has a greater influence on the spreading flow process. During the impact of single/double slag on the wall with different inclination angles, the time taken by the double slag to reach the final spreading length and complete phase transition is nearly five times longer than that of the single slag. The direction of slag impact also has an effect on the spreading and phase transition. This SPH method provides a novel numerical simulation idea to study the kinetic behavior of molten slag hitting the wall and the problems related to phase change deposition in boilers.

The development of a fly ash-based geopolymer for extrusion-based 3D printing, along with a printability prediction method

This paper presents insights into the design and development of a geopolymer consisting of fly ash and ground granulated blast furnace slag (GGBFS) usable for extrusion-based 3D printing. It also reports on factors influencing the printability of the geopolymer, such as the amount of GGBFS, the solids content, mixing time, and activator ratio. Besides measuring the setting behaviour, the yield stress, and the ultrasonic velocity, we also conducted a modified flow spread test to investigate the geopolymer’s early physical material properties. We also used analytical methods (SEM, XRD, and TG) to explain its physical behaviour. We introduced an adjusted test for the flow spread (VFS test), which gives information about the thixotropic behaviour depending on the shear stress and the opentime for printing. By comparing the derivatives of the yield stress curve with printing tests on an XYZ gantry printer and analysis of the yield stress measurement’s transition point, we also present a unique method that allows researchers to assess the printability of the geopolymer solely on one small-scale laboratory tests without requiring printing tests on a physical 3D printer.

Mathematical modeling and flow thermodynamics study of borosilicate glass melt after external addition of Cr2O3

This article uses a high-temperature sintering imaging instrument to test the flowability of borosilicate glass melt doped with Cr2O3, and establishes a mathematical model for high-temperature glass melt spreading. Discuss the glass melt from a thermodynamic perspective by combining model interpretation with experimental characterization. The results indicate that the thermodynamic judgment formula for high-temperature flow spreading of borosilicate glass is: Q≥ρ[A0exp(−T/k0)+S0]−M·δ[A0exp(−T/k0)+S0]1/2. To improve the high-temperature flow ability of borosilicate glass, it is necessary to increase the spreading activation energy Q. On the other hand, it is necessary to reduce the spreading coefficients A0、 k0 and S0. As a refractory metal oxide and active oxide, Cr2O3 plays a role in reducing the spreading coefficient of glass systems.

Mechanical performance of cement mortar with clear glass waste powder as a partial sand replacement

Abstract This research addresses Malaysia’s glass waste predicament, primarily stemming from discarded glass bottles in the food and beverage sector. Typically consigned to landfills, these bottles not only occupy valuable space but also deplete essential resources like siliceous sand crucial for glass production. To combat this environmental issue, the study explores the viability of repurposing waste glass as a construction material. By processing the waste glass to match sand’s size distribution, it is incorporated into cement mortar. The investigation assesses the fresh and hardened properties of cement mortar, including density, flow spread diameter, and various strengths. Analysis of parameters, such as the cement/sand/water ratio, and the extent of glass waste replacement, reveals that 100 % replacement of sand with glass waste powder yields the highest strengths, notably in compressive, splitting tensile, and flexural tests. Maintaining a cement/sand/water ratio of 1:5:1.24 achieves a 7 MPa compressive strength at 28 days and a 200 mm spread diameter in the flow table test. The study concludes that increasing glass waste replacement enhances cement mortar strengths, providing a sustainable solution to Malaysia’s glass waste issue and enhancing construction materials like bricks and concrete products.

From cement to geopolymers: Performances and sustainability advantages of ambient curing

The production of Portland cement results in substantial carbon emissions. Geopolymers are regarded as highly promising alternative binder materials to cement due to their low energy consumption and excellent mechanical properties. However, it should be noted that the thermal curing process of geopolymers diminishes their low-carbon advantage. In this study, ground granulated blast furnace slag (GGBS) was used to replace metakaolin (MK) by the ratio of 10 %, 20 %, 30 %, 40 %, and 50 % to produce geopolymers. The aim was to examine the impact of GGBS content on the thermal curing performance of MK-based geopolymers. The microstructure of the specimens was analyzed using SEM and XRD analysis techniques. Lastly, a comprehensive assessment of their sustainability potential was carried out. As a result, slag may increase flow spread, decrease the setting time, and effectively improve the mechanical properties which curing on ambient temperature. The group with 50 % slag content had the highest compressive and flexural strengths, reaching 55.9 MPa and 8.45 MPa at 28 d, respectively. The drying shrinkage of geopolymers increases as the GGBS content goes up. Notably, owing to the evolution of chemical transformation and gel structure, MK exhibits a significant mitigation on shrinkage. Ultimately, with a 50 % slag content, the carbon dioxide emissions of geopolymer can be reduced to 265.36 kg CO2-eq, which is a 43.6 % decrease compared to that of OPC. With a comprehensive consideration of the performance and sustainability potential of geopolymers, it is recommended to introduce GGBS content in the range of 30 %–40 %.

From CountMin to Super kJoin Sketches for Flow Spread Estimation

Real-time data stream processing is key to many Internet applications ranging from e-commerce, social networks, to network monitoring. Sketches (compact data structures) are often used to track large, high-rate streams and estimate their statistics. However, the traditional model for measuring flow size, e.g., number of packets in each flow, is unsuitable for more sophisticated applications that require flow spreads, i.e., number of distinct elements in each flow. When there are numerous flows, most existing work modifies CountMin sketches — which were designed to measure flow size — for measuring flow spread. They inherit a similar design and a commonly-used min operation from the CountMin sketches. This paper casts doubt on such a solution path, arguing that the inherited sketch design and the min operation were both intended for a different purpose and are not the best for flow spread measurement. Replacing the min operation with new position-aware operations, we propose the kJoin sketches that achieve much better average accuracy. We mathematically derive the estimation error bound. We also apply our sketches for network-wide measurement. Trace-driven experiments on software/GPU/FPGA platforms demonstrate our work significantly improves estimation accuracy, streaming rate (recording throughput), and query throughput, compared to the state-of-the-art.

The role of shear flow collapse and enhanced turbulence spreading in edge cooling approaching the density limit

Experimental studies of the dynamics of shear flow and turbulence spreading at the edge of tokamak plasmas are reported. Scans of line-averaged density and plasma current are carried out while approaching the Greenwald density limit on the J-TEXT tokamak. In all scans, when the Greenwald fraction fG=n¯/nG=n¯/(Ip/πa2) increases, a common feature of enhanced turbulence spreading and edge cooling is found. The result suggests that turbulence spreading is a good indicator of edge cooling, indeed better than turbulent particle transport is. The normalized turbulence spreading power increases significantly when the normalized E×B shearing rate decreases. This indicates that turbulence spreading becomes prominent when the shearing rate is weaker than the turbulence scattering rate. The asymmetry between positive/negative (blobs/holes) spreading events, turbulence spreading power and shear flow are discussed. These results elucidate the important effects of interaction between shear flow and turbulence spreading on plasma edge cooling.

Impact of design aspects on iron removal efficiencies from coal mine drainage in full-scale lagoons

In response to the potential ecological problems caused by coal mine drainage, passive Mine Water Treatment Schemes (MWTS), consisting of settlement lagoons and aerobic wetlands, are developed to remove iron and other contaminants prior to discharge into the environment. Existing research has examined individual design aspects separately, addressing the effect of lagoons' design on treatment performance. However, long-term research lacks data on the design aspects of full-scale mine drainage lagoons, to ensure consistent iron removal and optimal treatment of the mine drainage. This study analysed and assessed the design aspects of five full-scale lagoons, alongside monthly iron concentrations spanning over a period of twelve years, aiming to evaluate lagoon treatment performance based on different design aspects. Correlation and regression analyses were conducted to offer a better understanding of the potential relationships between iron removal efficiencies and the various design aspects of lagoons.Results indicated that the mean iron removal efficiencies of the lagoons studied, ranged from 25.12% to 92.85%, being impacted by the different design features. The correlation and multiple regression analysis results suggest that operational Water Levels, Surface Area, Aspect Ratio, layout and number of inlets and outlets, as well as shape of the lagoons affected iron removal (R2 0.78, p-value <0.05). Lagoons with larger aspect ratio were observed to have performed better in removing iron. In addition, a reduction in operational water level was observed to lead to increased iron removal. Furthermore, the result of the regression analysis demonstrated that the age of the lagoon significantly affects its treatment performance. Overall, lagoons with mid-mid configuration, multiple inlets and outlets and aspect ratio of 4 are found to allow for better flow and contaminant spread within the system, ensuring better adsorption and optimal removal of iron, although subject to regular ochre removal. This study offers valuable insights to lagoons design engineers, research scientists, policy makers and MWTS operators to optimize treatment performance.

Monitoring and Early Warning Method of Debris Flow Expansion Behavior Based on Improved Genetic Algorithm and Bayesian Network

Based on an improved genetic algorithm and debris flow disaster monitoring network, this study examines the monitoring and early warning method of debris flow expansion behavior, divides the risk of debris flow disaster, and provides a scientific basis for emergency rescue and post-disaster recovery. The function of the debris flow disaster monitoring network of the spreading behavior disaster chain is constructed. According to the causal reasoning of debris flow disaster monitoring information, the influence factors of debris flow, such as rainfall intensity and duration, are selected as the inputs of the Bayesian network, and the probability of a debris flow disaster is obtained. The probability is compared with the historical data threshold to complete the monitoring and early warning of debris flow spreading behavior. Innovatively, by introducing niche technology to improve traditional genetic algorithms by learning Bayesian networks, the optimization efficiency and convergence speed of genetic algorithms are improved, and the robustness of debris flow monitoring and warning is enhanced. The experimental results show that this method divides debris flow disasters into the following five categories based on their danger: low-risk area, medium-risk area, high-risk area, higher-risk area, and Very high-risk area. It accurately monitors the expansion of debris flows and completes early warning. The disaster management department can develop emergency rescue and post-disaster recovery strategies based on early warning results, thus providing a scientific basis for debris flow disasters. The improved genetic algorithm has a higher learning efficiency, a higher accuracy, a faster convergence speed, and higher advantages in learning time and accuracy of the Bayesian network structure.

In-depth investigation of FAM20A insufficiency effects on deciduous dental pulp cells: Altered behaviours, osteogenic differentiation, and inflammatory gene expression.

Loss-of-function mutations in FAM20A result in amelogenesis imperfecta IG (AI1G) or enamel-renal syndrome, characterized by hypoplastic enamel, ectopic calcification, and gingival hyperplasia, with some cases reporting spontaneous tooth infection. Despite previous reports on the consequence of FAM20A reduction in gingival fibroblasts and transcriptome analyses of AI1G pulp tissues, suggesting its involvement in mineralization and infection, its role in deciduous dental pulp cells (DDP) remains unreported. The aim of this study was to evaluate the properties of DDP obtained from an AI1G patient, providing additional insights into the effects of FAM20A on the mineralization of DDP. DDP were obtained from a FAM20A-AI1G patient (mutant cells) and three healthy individuals. Cellular behaviours were examined using flow cytometry, MTT, attachment and spreading, colony formation, and wound healing assays. Osteogenic induction was applied to DDP, followed by alizarin red S staining to assess their osteogenic differentiation. The expression of FAM20A-related genes, osteogenic genes, and inflammatory genes was analysed using real-time PCR, Western blot, and/or immunolocalization. Additionally, STRING analysis was performed to predict potential protein-protein interaction networks. The mutant cells exhibited a significant reduction in FAM20A mRNA and protein levels, as well as proliferation, migration, attachment, and colony formation. However, normal FAM20A subcellular localization was maintained. Additionally, osteogenic/odontogenic genes, OSX, OPN, RUNX2, BSP, and DSPP, were downregulated, along with upregulated ALP. STRING analysis suggested a potential correlation between FAM20A and these osteogenic genes. After osteogenic induction, the mutant cells demonstrated reduced mineral deposition and dysregulated expression of osteogenic genes. Remarkably, FAM20A, FAM20C, RUNX2, OPN, and OSX were significantly upregulated in the mutant cells, whilst ALP, and OCN was downregulated. Furthermore, the mutant cells exhibited a significant increase in inflammatory gene expression, that is, IL-1β and TGF-β1, whereas IL-6 and NFκB1 expression was significantly reduced. The reduction of FAM20A in mutant DDP is associated with various cellular deficiencies, including delayed proliferation, attachment, spreading, and migration as well as altered osteogenic and inflammatory responses. These findings provide novel insights into the biology of FAM20A in dental pulp cells and shed light on the molecular mechanisms underlying AI1G pathology.

Numerical simulation of solidification of boiler molten ash impinging on vertical wall based on Smoothed Particle Hydrodynamics method

In order to study the whole process of the high temperature liquid slag fly ash produced after the combustion of high alkali coal as power coal in the boiler furnace, which moves in the furnace and impinges on the water wall, the heat exchange occurs and then the cooling phase transformation deposits and slags, and the possible factors of slagging particles are studied by changing the environmental variables. In this paper, based on Smoothed Particle Hydrodynamics (SPH), the dynamic behavior of boiler molten ash impacting vertical wall is studied, and the flow spreading and solidification model of molten slag impacting vertical wall is established. Thus, the process of phase change deposition of slag particles against wall is simulated. By observing the phase distribution of slag and the change in spreading process, the complete process of the slag particles hitting the wall, spreading, shrinking and solidifying is analyzed. Based on the cohesive and repulsive surface force method, a temperature-dependent surface tension model is established to simulate the effect of surface tension on flow characteristics when molten ash impinges on low-temperature vertical walls. The influences of slag impact velocity, initial temperature and water wall temperature on deformation and solidification heat transfer are discussed. The results show that the initial velocity and initial temperature of slag particles affect the phase change deposition velocity and the final spreading factor of slag, while the temperature of the water wall has little effect on the deposition deformation and solidification process of slag.

Experimental and numerical study on liquid film cooling performance under heated wall condition

Liquid film cooling is broadly applied in the thermal protection of liquid rocket engine. An experimental system of liquid film cooling for a heated curved stainless-steel wall is built in this study to investigate the effects of jet mass flow rate, jet angle, and nozzle diameter on the cooling performance. The temperature distribution of the heated wall is demonstrated with infrared thermography technology and the flow spreading shape of the liquid film is captured with high-speed camera. A numerical liquid film cooling model based on the volume of fluid (VOF) coupled Level-set method is established to calculate the evaporative heat absorption and spreading shape of liquid film. The experimental study indicates that the peak film thickness in the hydraulic jump region increases with the jet mass flow rate, such as the peak film thickness increases from 265.15 to 632.25 μm at Q = 100–600 mL·min−1. Besides, a jet angle of 35 degree can maintain the maximum wall temperature drop of 29.4 °C. In addition, the simulated peak film thickness presents a minimum deviation of 5.2 % from the experimental data. The numerical model provides important reference for the study of liquid film cooling performance of the liquid rocket engine.

Mechanochemical Activation of the C‐S‐H binder Celitement

AbstractThe hydraulic binder Celitement is produced by a mechanochemical activation of an X‐ray amorphous CSH phase. This process step not only chemically activates the material, but also reduces its specific surface area. Thus, both strength and workability of Celitement based systems can be controlled. In this paper the effect of the duration of the activation milling on chemical and microstructural changes of Celitement is focused. Therefore ATR‐FTIR Spectroscopy, Thermogravimetry, Heatflow Calorimetry, Scanning Electron Microscopy and BET (N2) specific surface area measurements are used aside classical experiments on the flow spread and compressive strength of Celitement based mortars. As a result, it is shown that micro structural changes and chemical activation occur already at the beginning of the activation milling and significantly influence the practical performance of mortars.

Optimization of a Self-Compacting Paste Based on Glass Powder Using Mixture Design and the Desirability Function

Abstract The partial replacement of cement by supplementary cementitious materials is an opportunity for reducing fossil energy consumption and greenhouse gas emissions. In this study, forty (40) pastes were formulated by applying a 4-factor mixture plan, consisting of cement, glass powder (GP), superplasticizer and water. Third order models “special cubic” established for the flow time, spreading diameter, and flow velocity, responses were statistically significant. The analysis of the models allowed the study of the individual and combined effects of the different factors, highlighting the predominant effect of the superplasticizer on the dispersion GP fines. The multi-criteria optimization allowed the development of two optimal pastes SCP1 and SCP2 incorporating 25 and 7% GP, respectively. SCP1 was chosen because at this GP amount, unlike at 28 days, the paste presents the best strengths at 90 days with 4.5% increase for flexural tensile strength and 15.69% increase for compressive strength while maintaining satisfactory workability.

Bubble–bubble interactions in two-dimensional bubble-chain flows

We experimentally investigate the bubble–bubble interactions and associated flow structures in a two-dimensional bubble chain while varying the bubble generation frequency up to 21Hz. The considered bubbles are characterized by a Bond number of around 1.0, and Archimedes and Reynolds numbers of O(102), high enough to have the shape and path instabilities. Near the nozzle (developing region), bubble trajectories and spacing between adjacent bubbles are retained (bubble-in-line arrangement), driven by the upward inertia. As the flow develops, the bubble wakes become organized and thus their interactions govern the flow. With increasing the bubbling frequency, it can be further classified into the bubble pairing, grouping, and coalescence-dominant regime. In the in-line arrangement, the trailing bubble is acceleratingly dragged to the wake behind the leading bubble, which are rearranged in tandem by the asymmetric wake. With increasing the bubbling frequency, the bubbles form a group, rapidly diffusing the jet-like liquid flow horizontally. As the vertical inertia (inviscid mechanism) dominates, the coalescence occurs frequently and the horizontal spreading of the liquid flow is suppressed substantially. By analyzing the time-averaged and fluctuating liquid velocity fields, we explain the bubble–bubble interactions in relation to the consequent modulation of the liquid-phase flow.

Аналитическое решение задачи определения границы растекания потока

A mathematical model of a two-dimensional high-speed flow in terms of justification and taking into account several physical assumptions is formulated. The problem is solved analytically in the plane of the velocity hodograph and in the physical plane to determine all parameters in terms of flow flow. The coupling of a uniform flow with a general flow in the form of a "simple wave" made it possible to achieve a reduction in the error of the mathematical model. The adequacy of the pre-sented method is shown.&#x0D; The existing models are described that are insufficiently acceptable and adequate in terms of the geometry of the flow boundary, but with a large mismatch in local depths and velocities. The adequacy of the new model as a whole is characterized by the convergence of the model parameters both in geometry (flow spreading boundaries) and kinematics (depth and flow velocity) increased to 18% in both directions.&#x0D; The section of the "simple wave" should be well combined with the real flow, taking into ac-count the forces of resistance to the flow. The boundaries of the use of the proposed model belong to the section of the expansion of the flow in 3-7 b as required in the reference literature, and have been clarified in earlier works. The proposed model, as shown in the article, takes into account real (experimental) flow spreading and is consistent with previously performed theoretical studies. An important conclusion in the article is that the values of the Froude criterion in the new model can be any in the range from 1 to infinity, and at the same time the section "$X_D^I$" can increase with in-creasing Froude number.

Diagnostics of gas-dynamic connection between gas caps and their influence on the product composition of the North Caspian production wells as per tracer tests

Diagnostics of gas-dynamic connection between gas caps and their influence on the product composition of the North Caspian production wells as per tracer tests