Flow Behavior Research Articles

Numerical Simulations Using iRIC Nays2DH for Sediment Transport Behaviors in Dam Breach Tests

After the breach of a landslide dam, the sediment in the breach opening will be carried downstream by the breach flood. The river channel will also be eroded by the flood, resulting in bed load transport. Three large-scale dam breach tests were conducted to investigate the sediment transport behavior after a dam breach. The topography data of the creek channel were measured before and after the dam breach tests to understand the sediment transport behavior. The sediment transport simulations of the dam breach tests were conducted using the iRIC Nays2DH software. The simulations focused on three types of test setups: the single dam, single dam with a spur dike, and double dam models. The terrain (DEM) for the numerical model input was designated based on the LiDAR results, and a flow hydrograph during the dam breach tests was applied. The accuracy of the simulations was assessed using the “coverage index” and “mean absolute percentage error”. A numerical parametrical study was performed to find the major parameters that influenced the simulations. The results showed that the dynamic behavior of water flow and sediment during the dam breach processes were effectively captured by the iRIC Nays2DH simulation, but with limitations. The average flow velocity of the flood in the single dam case was the fastest among the three types of dam breaches. Due to the contraction of the creek channel caused by the spur dike, severe erosion occurred locally, and the flow rate increased in the narrowed section. Water impoundment between the two dams after the first dam breach and the consequent breach of the second dam were also well-simulated for the double dam breach. The findings and simulations in this study help explain dam breaches better and can guide researchers working on sediment transport during dam-breach floods.

Performance evaluation of a scramjet engine utilizing varied cavity aft wall divergence with parallel injection in a reacting flow field

Abstract The effect of implications of the dual cavity with aft wall divergence in a parallel injection reacting flow has been numerically investigated. This research intends to emphasize the behaviour of the supersonic flow under varying divergence angles of the cavity aft wall. A two-dimensional Reynolds-Averaged Navier-Stokes (RANS) equation and an SST k-ω turbulence model with a single-step chemical reaction for hydrogen-air are utilized for the simulation. Followed by the strut injector, the cavities are positioned symmetrically inside the combustor. The bottom cavity aft wall divergence varies, whereas the top wall is mounted with a rectangular cavity. The performance of cavity locations is compared with the baseline DLR model. From the evaluation of numerical outcomes along with different cavity configurations, it has been noted that the 15-degree cavity divergence angle enhances the recirculation zone which leads to improved mixing performance. Also, the cavity improves the combustion stability by increasing the flow residence time. From this numerical analysis, it is associated that an almost 20 % reduction in combustor length is achieved, however, an 18 % rise in the pressure loss is noted because of emanating shock waves from the cavity edges.

Einstein’s spacetime curvature and gravitational waves: Elucidating the gradient flow of scalar invariants, variations in the Ricci scalar, and gravitational wave propagation

In the general theory of relativity initially rationalized by Einstein, the gravity is considered as an occurrence ensuing from the spacetime curvature, which is in turn triggered by the presence of mass. This article provides a detailed analysis of spacetime curvature and gravitational waves, enhancing our understanding of general relativity and astrophysics. Using both analytical and numerical methods, we examined the gradient flow of scalar invariants, variations in the Ricci scalar, and gravitational wave propagation. New findings include the identification of unique curvature patterns around rotating black holes, a detailed comparison of gradient flow behavior in different spacetime geometries, and the discovery of a correlation between scalar invariant fluctuations and gravitational wave amplitudes. These findings validate numerical techniques and reveal how different parameters affect gravitational wave characteristics. While simplified models are used, the present study offers a robust framework for future research. Our work aligns with previous studies but also reveals unique aspects of wave behavior, with implications for quantum gravity and cosmology.

Producing high-colloidal-stability sesame paste: structural role of stone milling-modified protein.

Sesame paste faces issues with poor colloidal stability during storage, thereby affecting product quality and consumer experience. This study aimed to modify the proteins in sesame paste through stone milling and investigated the differences in stability produced in this environment, with the goal of addressing this issue. As the number of grinding times increased from one to three, the median diameter of sesame paste significantly decreased from 85 to 74 μm (P < 0.05), and the centrifugal oil separation rate dropped from 9.05% to 6.82%. Rheological measurements indicated an increase in the flow behavior index (n) from 0.51 to 0.61. Confocal laser scanning microscopy results revealed a more uniform co-distribution of protein and oil when ground thrice. The β-sheet content of the protein in sesame paste increased from 52.92% to 56.34%, with enhancements in surface hydrophobicity, hydrophobic interactions and emulsification of protein. When the number of grinding times increased to five, the particle size of the sesame paste was further reduced and the β-sheet content of the protein decreased to 51.00%, while the oil separation rate increased to 7.78%. Stone milling induces structural modifications in proteins, which in turn alter the internal structure of sesame paste, resulting in varying levels of oil separation at different grinding times. Among them, sesame paste ground thrice showed a 25% reduction in the oil separation rate and experienced minimal oil separation over 120 days, making it suitable for practical production. © 2024 Society of Chemical Industry.

Effects of spherical, disk-like and lamellar nanocomposite particles on cold flow behaviors of waxy crude oil

Wax precipitation and deposition are challenging hurdles in pipeline transportation of waxy crude oil. This study focuses on transforming SiO2, Laponite, and montmorillonite particles into hydrophobic particles through polymer grafting. Chemical structure analysis and grafting ratio calculation were performed. Through thermogravimetric analyzer (TGA) test, Laponite showed the highest grafting ratio. The effects of adding nanocomposites, TDA-2024-22, and commercial pour point depressants on the rheological behavior and wax crystallization behavior of African crude oil were compared. Addition of the nanocomposite PDA-22@SiO2 to crude oil, reduced the viscosity by 85.6% at 20 °C and the thixotropy by 60.2%. Wax crystal size decreased in the order of PDA-22@SiO2, PDA-22@Laponite, KS-10, TDA2024-22, and PDA-22@MMT. The pour point decreased by 6 °C with PDA-22@ SiO2 particles but only 3 °C with Laponite and montmorillonite composites. Spherical nanocomposites are promising flow improvers for waxy crude oil.

Numerical Study of Hydrogen-Rich Fuel Coherent Jet in Blast Furnace Tuyere

Injecting hydrogen-rich fuel into blast furnaces is an effective strategy to reduce carbon dioxide (CO2) emissions. The present study established a three-dimensional (3D) model based on a coherent jet of hydrogen-rich fuel. The combustion characteristics and the flow, heat, and mass transfer behaviors in the reaction region were simulated by the Computational Fluid Dynamics (CFD) method. The effects of fuel jet velocity on the distributions of gas velocity, temperature, and species in the reaction region were systematically analyzed. The results show that hydrogen-rich fuel burned around the main jet, generating a high-temperature, low-density flame. As flame length increased, the main jet experienced less decay. The outward expansion of the jet caused continuous diffusion of gas temperature and its components. As the fuel jet velocity increased, the temperature along the main jet centerline rose sharply, while the length of the high-concentration gas region extended. Doubling the jet velocity increased its centerline velocity by 11% and raised the average reaction region temperature by 4.12%. The obtained highlighted results are of paramount importance for optimizing hydrogen-rich smelting in blast furnaces.

Flow behavior and heat transfer characteristics of liquid film on vertical hot surface by inclined jet impingement

In this study, the flow behavior and heat transfer characteristics of the liquid film on the hot wall by inclined jet impingement are experimentally studied in detail. The effects of jet parameters, such as jet inclination angle, impingement distance, jet Reynolds number (Rej), and nozzle diameter are explored. The liquid film flow is visualized using a high-speed camera, and the surface temperature and heat flux are obtained by solving the inverse heat conduction problem. The results indicate that the liquid film shape is strongly affected by jet inclination angle but is almost unaffected by other parameters. As the inclination angle increases, the liquid film shape changes from elliptical to fusiform. In addition, the onset, enhancement, and disappearance of boiling cause the expansion and contraction of liquid film. The splashing rate is barely affected by jet parameters and remains within the range of 80–95 % under all conditions. The propagation of wetting fronts exhibits anisotropy. Except for the impingement distance, the position of wetting fronts along y-axis direction displays a high dependence on all parameters. The Rej and nozzle diameter have a significant effect on the heat flux at the impingement point and parallel flow zone, while the jet inclination angle and impingement distance only effect the impingement point. The visualization image proves that the droplet impingement pattern is the main reason for the increase in heat flux at higher impingement distances. Optimizing jet parameters can promote the wall to enter the rapid cooling stage in advance and increase maximum heat flux, thereby improving the maximum cooling capacity of the jet. Finally, an empirical equation is proposed to predict the maximum Nusselt number.

Serrated Flow Behavior in Commercial 5019 Aluminum Alloy

Serrated flow effects are visible on a metal surface even after coating. Thus, they are undesirable to manufacturers and product users. To meet the expectations of the industry, research on the conditions for serrated flow occurrence in 5019 aluminum alloy was carried out and the results were collected in the current paper. Thus, the influence of the alloy initial microstructure due to different tempers as well as plastic deformation conditions, i.e., strain rate and temperature, on the alloy stress–strain behavior was determined. Two tempers were considered: the as-fabricated F-temper and the W-temper (i.e., quenched in water after annealing at 500 °C). The synergic influence of these tempers and their tensile test conditions on the serration behavior of the stress–strain curves, i.e., the stress drop and reloading time, were also determined and categorized. Structural and X-ray diffraction studies rationalized the stress–strain characteristics according to dynamic strain aging models with positron annihilation lifetime spectroscopy providing insight into the role of lattice defects (i.e., dislocations and vacancies). The map of the serrated flow domain allowed us to obtain the activation energy of the onset of the Portevin–Le Chatelier effect equal to 56 kJ/mol. It is close to the activation energy for the pipe diffusion mechanism, obtained by applying the model formulated originally for Type B stress serration.

Emulsifiers: Their Influence on the Rheological and Texture Properties in an Industrial Chocolate

The complexity of the chocolate matrix leads to it having characteristic rheological properties that may pose difficulties for its industrial manufacture. Many factors influence the flow behaviour of chocolates, such as raw materials, the amount of fat, the moisture content, particle-size distribution, the concentration of emulsifiers, or manufacturing conditions, among others. This study focusses on the rheological properties of an industrially manufactured chocolate with a 48% cocoa content, and the effect caused by the addition of two emulsifiers (soya lecithin and polyglycerol polyricinoleate (PGPR)) on the rheological properties. In the case of lecithin, a clear effect has been observed on the plastic viscosity and the yield stress. Plastic viscosity decreases until a concentration of 0.6% lecithin is reached, and thereafter remains relatively constant, while yield stress increases over the studied range. This effect is not observed when PGPR is used as the emulsifying agent. In this case, a small concentration of PGPR decreases the yield stress. Thixotropy was determined using the Casson model, and its behaviour was found to be similar to that of plastic viscosity with respect to changes in the PGPR and lecithin concentrations. Textural determinations were also carried out, relating the rheology characteristics to the texturometry.

Flow behaviors and dynamic recrystallization mechanisms study of TC4 under different temperatures and strain rates

Flow behaviors and dynamic recrystallization mechanisms study of TC4 under different temperatures and strain rates

Effects of fluid properties on coarse particles transport in vertical pipe

The mineral resources in deep-seabed are attracting extensive attention. A numerical simulation of particle transport in a vertical pipe for a deep-sea mining system is conducted using the CFD-DEM method. The effects of fluid density, fluid viscosity and rheological parameters of non-Newtonian fluids on the liquid-solid flow behavior in a vertical pipe are investigated. For Newtonian fluids, increasing the density or viscosity enhances the particles' performance in following the fluid and reduces the slip velocity, but also increases the pressure drop. The efficient lifting of particles can be facilitated by adjusting fluid density and viscosity, while considering factors such as energy consumption. For non-Newtonian fluids, an increase in either the flow behavior index n or the consistency coefficient k results in an increase in the fluid's apparent viscosity. This leads to an increase in the particle suspension capacity and local particle velocity, along with a decrease in local particle concentration.

Bioavailability Improvement by Atomic Layer Coating: Fenofibrate A Case Study

Biopharmaceutical Classification Systems (BCS) class II drugs show poor solubility and high permeability in the body. Fenofibrate (FF) is a classic example of a BCS class II drug, used to treat high cholesterol and triglyceride (fat-like substances) levels in the blood. Atomic layer coating (ALC) is a surface engineering technology adapted from the semiconductor industry, where metal oxides are coated one atomic layer at a time over the active pharmaceutical ingredients (API) particles. ALC coating was proven to improve the processability, alter the hydrophilicity, improve the stability, and fine-tune the release of drugs. Herein, we report the intervention of ALC coating in enhancing the bioavailability of a poorly water-soluble drug (fenofibrate) in the animal model. The physical properties of uncoated fenofibrate were compared with those of zinc oxide-coated and silicon oxide-coated fenofibrate. Following the application of the coatings, the structural integrity (both chemical stability and solid-state stability) of the active pharmaceutical ingredient (API) remained uncompromised, as corroborated by 1H NMR and powder X-ray diffraction analyses. Notably, zinc oxide-coated fenofibrate exhibited favorable flow characteristics, whereas no discernible enhancement in flow behavior was observed for silicon oxide-coated fenofibrate. The results from contact angle measurements suggest that the silicon oxide-coated fenofibrate exhibits superior wetting behavior, as indicated by a contact angle nearing 0°. The application of ALC demonstrates an enhanced dissolution rate when compared to the uncoated active pharmaceutical ingredient (API) while leaving its equilibrium solubility unaffected. Coating the API with silicon oxide improves particle hydrophilicity and wetting properties, whereas zinc oxide coating aids in particle de-agglomeration, thereby enhancing their interaction with an aqueous medium. In vivo bioavailability studies conducted on rodents and larger animal (dog) models indicate a substantial increase in bioavailability (approximately 2 times) for the silicon oxide-coated API in comparison to the uncoated API, as determined by the area under the curve (AUC). Furthermore, the Cmax values for the silicon oxide-coated API also demonstrate a significant increase (approximately 3 times) over the uncoated API. Notably, an oral subacute toxicity study of ALC silicon-coated fenofibrate revealed no toxic effects attributable to the coating. This study underscores the potential of ALC in augmenting the bioavailability of BCS(II) drugs.

Study on heat transfer and flow of molten pool during the deposition process of laser wire additive manufacturing

In the laser wire additive manufacturing process, the molten pool acts as the critical link between the wire and the deposited part. The heat transfer and flow behavior within the molten pool predominantly determine the quality of the final deposition. Under laser power ranging from 2400 to 3000 W, traverse speeds between 0.01 and 0.04 m/s, and wire feeding speeds from 0.03 to 0.08 m/s, three distinct flow states—single-swirl, double-swirl, and no-swirl—were observed with increasing heat input. Under the optimum process parameters, the molten pool with stable temperature distribution and orderly flow was obtained. In multilayer deposition, the implementation of a laser decay strategy mitigates steep temperature gradients, diminishes the Marangoni effect within the molten pool, and effectively reduces both heat accumulation and lateral flow. Consequently, the flow mode transitions from no-swirl to swirl, and the maximum flow velocity decreases by 40%.

Flow Behavior and Breakup of Liquid Jets Issued from Rectangular Nozzles

Flow Behavior and Breakup of Liquid Jets Issued from Rectangular Nozzles

CFD Investigation of Dual Synthetic Jets on an Optimized Aerofoil's Trailing Edge

In fluid dynamics, a flow control device is used to control, manage, or modify the behavior of a fluid flow. Jet actuators work by releasing high-velocity jets of fluid, usually air or gas, into the surrounding environment to control or manipulate the flow of fluids. In this study, the flow control device, which was a dual synthetic jet actuator (DSJA), acted as a lift enhancement device over an optimized NACA 0012 aerofoil with a rounded trailing edge (TE) (Coanda surface approximately 9% of the trailing edge was modified) to enhance the lift at various angles of attack (AOAs). Fluctuating pressure inlets were introduced in two slots. When the dual synthetic jets were in control, the out-of-phase jets from the upper and lower trailing edge jets helped to boost the lift coefficient. The suction stroke from the lower half of the jet made the Coanda effect stronger in the upper half. The upper trailing edge jet deflected downwards merged with the lower one and helped to deflect the flow field closer to the bottom half. An unsteady CFD analysis was performed on optimized airfoils with and without a DSJ, with a driving frequency of 40.6 and a reduced frequency of 0.025 at a Reynolds number of 25000. The results obtained at different angles indicated that the L/D ratio was improved by 13.5% at higher angles of attack in the presence of the DSJA.

Long time behavior for the two-dimensional magnetohydrodynamic flows in a general domain

By utilizing spectral analysis methods and properties of fractional order operators, some new estimates have been established for the nonlinear terms appearing from the two-dimensional non-stationary magnetohydrodynamic flows in a general domain. Based on these, a series of energy decay properties are given. Furthermore, the large time decay behavior of the solution and that of its gradient have also been addressed in the L∞ and L2 spaces, respectively.

Exploring the Thermal Behavior of Cu-water and CuO-water Power-law Nanofluids on a Rotating Circular Disc: A Computational Analysis

The current theoretical investigation focuses on the thermal behavior of a power-law nanofluid flow on a rotating circular disc. In which nanofluid is made by taking colloidal suspension of copper (Cu) and copper oxide (CuO) nanoparticles in a base fluid like water. A theoretical investigation is conducted by formulating a mathematical model of a power-law fluid (which exhibits shear thickening and thinning effects) along with the Tiwari and Das model. A similarity transformation is employed to transform the nonlinear partial differential equations (PDEs) into ordinary differential equations (ODEs) and these ODEs are then numerically solved using the shooting technique. The study's findings are analyzed graphically by plotting radial, tangential, and axial velocity profiles, temperature profiles, Nusselt number, and skin friction coefficients to show how various factors affect the fluid's flow and heat transfer. It is revealed that drag force reduces in Cu-water nanofluid as compared to CuO-water nanofluid for all types of fluids (Newtonian, pseudoplastic, and dilatant fluids) and Nusselt number becomes high in Cu-water nanofluid for both Newtonian and dilatant fluids as compared to CuO-water nanofluid but in case of pseudoplastic reverse behavior is observed. Heat transfer rate in Cu-water dilatant and pseudoplastic nanofluids increases up to 20.4% and 12.5% with respect to base fluid and in CuO-water dilatant and pseudoplastic water nanofluids, it increases up to 18.6% and 15.2%.

LSTM + Transformer Real-Time Crash Risk Evaluation Using Traffic Flow and Risky Driving Behavior Data

LSTM + Transformer Real-Time Crash Risk Evaluation Using Traffic Flow and Risky Driving Behavior Data

Data-driven prediction of flow fields in a needle-ring-net electrohydrodynamic pump system

In this paper, a data-mechanism hybrid modeling method for efficiently obtaining an electrohydrodynamic flow field is proposed. First, a backpropagation (BP) model with high accuracy is trained to get the value of essential parameter q0 for the mechanism simulation of flow fields. Subsequently, the mechanism model is used to generate a database for flow field reconstruction. Three machine learning algorithms, namely, BP neural network, random forest regression (RFR), and convolutional neural network (CNN), are employed to predict and reconstruct the flow behaviors of a needle-ring-net electrohydrodynamic pump. The RFR model demonstrates higher accuracy and precision in predicting velocity and pressure in the flow field compared to the BP and CNN models. The use of machine learning models for flow field prediction can significantly reduce the computational time while maintaining the computational accuracy. Additionally, an analysis assessing the impact of varying dataset sizes on the prediction accuracy of the model is conducted. The results indicate that the size of the dataset significantly influences the model predictive performance. Specifically, larger datasets are suggested to enhance both the accuracy and the generalization capabilities of the model. This observation highlights the critical role of dataset size in optimizing the performance of machine learning models for predictive tasks in engineering applications. These results offer important references for improving the design and optimization of electrohydrodynamic pumps.

Bedform development in confined and unconfined settings of the Carchuna Canyon (Alboran Sea, western Mediterranean Sea): An example of cyclic steps in shelf-incised canyons

Newly acquired high-resolution multibeam bathymetry in combination with sub-bottom acoustic profiles, surficial sediment samples, and three-dimensional flow simulations made possible the characterization of bedforms along the axial channel and depositional lobe of the shelf-incised Carchuna Canyon (Alboran Sea, western Mediterranean Sea). This study aims to describe the erosional and depositional bedforms in confined and unconfined settings of the Carchuna Canyon in order to determine the genetic constraints on sedimentary processes leading to bedform development along the canyon in recent times.The straight Carchuna Canyon, deeply incised in the shelf up to 200 m off the coastline, hosts: (1) crescentic-shaped bedforms (CSBs) that exhibit distinctive crest concavities, asymmetries, and lengths along the axial channel; (2) continuous lateral levees and; (3) a channel bend with three depressed stretches of the levee crest that are less than 20 m high. A set of concentric sediment waves and two scour trails were identified proximal to the channel bend on the open slope east of the Carchuna Canyon. Two distinct acoustic groups consisting of four acoustic units with distinct acoustic patterns were defined along the sediment wave field. The sediment transport simulation shows the highest flow velocities along the Carchuna Canyon thalweg, while along the overbank deposition the highest velocity values occur along the top of the bedform crests, with the higher Froude values being found over the bedform lee sides.The occurrence of CSBs along the canyon axial channel suggests the imprint of confined sediment-laden gravity flows descending from the canyon head and exhibiting a flow variability along the canyon induced by local variations of slope gradient and/or sediment concentration. A spatial relationship is identified between the development of sediment waves over the overbank deposit and lowered levee crest heights at the channel bend. In contrast, more energetic downstream turbiditic flows exceed the levee crest at the channel bend, focusing the overflow and promoting erosion of the overbank deposit, thereby generating the scour trains. Based on the recent history of overbank deposition, two alternating scenarios of flow behavior can be interpreted. In a high-density turbidity current setting, erosion would prevail along the axial channel. Widespread spillover flows of coarse-grained sediments would occur in both levees, forming heterogeneous sedimentary patterns that change downslope within the depositional lobe due to lesser turbulence of spillover turbidity currents and gentler slope gradients. In contrast, in a low-density turbidity current setting, turbidity currents flowing along the Carchuna Canyon would form depositional bedforms in the axial channel, while spillover processes would be localized at the channel bend, forming either depositional or erosional bedforms over the depositional lobe according to the frequency, magnitude and focusing of turbiditic flows.