Interface Velocity Research Articles

Retrograde Condensation in Gas Reservoirs from Microporous to Field-Scale Simulation

Hydrocarbon fields that contain non-associated gas, such as gas condensate, are highly valuable in terms of production. They yield significant amounts of condensate alongside the gas, but their unique behavior presents challenges. These reservoirs experience constant changes in composition and phases during production, which can lead to condensate blockage near wells. This blockage forms condensate bridges that hinder flow and potentially decrease gas production. To address these challenges, engineers rely on numerical simulation as a crucial tool to determine the most effective project management strategy for producing these reservoirs. In particular, relative permeability curves are used in these simulations to represent the physical phenomenon of interest. However, the representativeness of these curves in industry laboratory tests has limitations. To obtain more accurate inputs, simulations at the pore network level are performed. These simulations incorporate models that consider alterations in interfacial tension and flow velocity throughout the reservoir. The validation process involves reproducing a pore network flow simulation as close as possible to a commercial finite difference simulation. A scale-up methodology is then proposed, utilizing an optimization process to ensure fidelity to the original relative permeability curve at a microporous scale. This curve is obtained by simulating the condensation process in the reservoir phenomenologically, using a model that captures the dependence on velocity. To evaluate the effectiveness of the proposed methodology, three relative permeability curves are compared based on field-scale productivities and the evolution of condensate saturation near the wells. The results demonstrate that the methodology accurately captures the influence of condensation on well productivity compared to the relative permeability curve generated from laboratory tests, which assumes greater condensate mobility. This highlights the importance of incorporating more realistic inputs into numerical simulations to improve decision-making in project management strategies for reservoir development.

A Pore-Scale Simulation of the Effect of Heterogeneity on Underground Hydrogen Storage

Using underground hydrogen storage technology has been recognized as an effective way to store hydrogen on a large scale, yet the physical mechanisms of hydrogen flow in porous media remain complex and challenging. Studying the heterogeneity of pore structures is crucial to enhance the efficiency of hydrogen storage. In order to better understand the pore-scale behavior of hydrogen in underground heterogeneous porous structures, this paper investigates the effects of wettability, pore–throat ratio, and pore structure heterogeneity on the behavior of the two-phase H2–brine flow using pore-scale simulations. The results show that the complex interactions between wettability, heterogeneity, and pore geometry play a crucial role in controlling the repulsion pattern. The flow of H2 is more obstructed in the region of the low pore–throat ratio, and the obstructive effect is more obvious when adjacent to the region of the high pore–throat ratio than that when adjacent to the region of the medium pore–throat ratio. In high-pore–throat ratio structures, the interfacial velocity changes abruptly as it passes through a wide pore and adjacent narrower throat. Interfacial velocities at the local pore scale may increase by several orders of magnitude, leading to non-negligible viscous flow effects. It is observed that an increase in the pore–throat ratio from 6.35 (low pore–throat ratio) to 12.12 (medium pore–throat ratio) promotes H2 flow, while an increase from 12.12 (medium pore–throat ratio) to 23.67 (high pore–throat ratio) negatively affects H2 flow. Insights are provided for understanding the role of the heterogeneity of pore structures in H2–brine two-phase flow during underground hydrogen storage.

Synergistic Effect of Influence Factors on Ammonia Volatilization in Fertilizer Solution: A Laboratory Experiment

Ammonia volatilization, which is one of the main ways that nitrogen gas is released from farmland, restricts promotion of the utilization of nitrogen fertilizer and contains some potential environmental risks. To investigate the general pattern of ammonia volatilization under actual paddy field conditions, we designed an indoor simulated system to measure the amount of ammonia volatilized within a single time period by controlling the pH and concentration of NH4+ (c(NH4+)) in the solution, the gas–liquid interfacial gas velocity, and the ambient temperature. In this paper, the influence of these factors, the synergistic effect on ammonia volatilization, and their quantitative relationship are discussed. We used solutions of ammonium bicarbonate (SAB) and diammonium phosphate (SDP) for the simulation experiments, and the results showed that there is a significant linear relationship between the amount of ammonia volatilization and c(NH4+). The correlation coefficients were between 0.9214 to 0.9897 and 0.8932 to 0.9904 for SAB and SDP, respectively. The quantitative relationship between temperature and pH and the influence factor (CIF) and the initial ammonia volatilization fluxes (IAVFs) was analyzed by the least-squares method, and the degrees of polynomial were one and two, respectively. The regression equations of the SAB and SDP among the amount of ammonia volatilization with the concentration of ammonium nitrogen, the temperature, and the pH were calculated by using MATLAB. Considering the effects of temperature and pH on the CIF and IAVFs under individual conditions, we used a binary cubic model to fit the relationship between temperature and pH to the CIF and IAVFs. The simulation results showed that the correlation coefficients between the CIF and IAVFs for SAB were 0.9980 and 0.9680, respectively, and the correlation coefficients were 0.9946 and 0.9708 for SDP, respectively. The quantitative equation took into account the coefficient of determination and degrees of polynomial, and the ammonia volatilization fluxes can be calculated by using these equations.

Modelling of high-velocity free-surface flows: a revised interfacial area approach

The specific interface area transport equation is derived from first principles, and a closure model for turbulent flow is proposed. The flow is modelled by a two-phase method providing velocities of both phases at the bubbly, spray and the intermediate large scale interface (LSI) regimes. The interface area is transported by the interface velocity – a linear combination of corresponding phase velocities and a turbulent drift velocity. The resulting equation includes the source terms due to the bubble (droplet) breakup and coalescence, and turbulent splashes at the interface. A model is proposed for the source term in the LSI regime. The model is implemented in the developer's version of the Simcenter STAR-CCM+ ® CFD code. The new model is applied to self-aerating water flows down stepped chutes; the results are in reasonable agreement with the experimental data.

Enhancing improved advection upstream splitting method on triangular grids: A hybrid approach for improved stability and accuracy in compressible flow simulations

This paper introduces NAUSM+M+AUFS (New Improved Advection Upstream Splitting Method Plus Artificially Upstream Flux Vector Splitting), a novel hybrid computational scheme for simulating compressible flows on triangular grids. The AUSM+M (Improved Advection Upstream Splitting Method) method is enhanced through two key modifications to boost numerical stability and robustness in high Mach number and hypersonic flows. The first modification redefines the interfacial numerical sound velocity, reducing shock anomalies and improving shock-capturing by integrating velocity and characteristic sound speed parameters. The second modification addresses the insufficiency of the pressure flux dissipation term at supersonic speeds by introducing a formulation that increases dissipation proportionally to the Mach number, thereby enhancing performance in high-speed flows. These enhancements constitute the NAUSM+M method. The NAUSM+M+AUFS scheme combines the strengths of NAUSM+M and AUFS (Artificially Upstream Flux Vector Splitting) methods, particularly in overcoming the limitations of NAUSM+M in handling shock instabilities and the carbuncle phenomenon on structure triangular grids. A dynamic switching function adjusts the weighting between NAUSM+M and AUFS, optimizing accuracy and stability based on local flow conditions. Numerical tests demonstrate that NAUSM+M+AUFS significantly outperforms AUSM+M, NAUSM+M, and AUFS, effectively eliminating the carbuncle phenomenon and providing smooth shock wave contours. In steady flow analysis, the new hybrid method achieves convergence speeds comparable to AUFS and shows 15% to 45% superior convergence accelerating than AUSM+M, depending on the convergence rate. In addition, in steady flow analysis, the accuracy of NAUSM+M+AUFS is 46% better than that of AUFS. This approach represents a significant advancement, offering a robust, accurate, and efficient solution for high-speed aerodynamic simulations, with broad applicability across various compressible flow challenges.

Influence of heating rate on the evolution of post-annealed microstructure in Nb–Ti microalloyed steel: Interplay with initial cold-rolled microstructure

This study focuses on understanding the complex interactions between the initial cold-rolled microstructure and the heating rate, and how these factors influence the post-annealed microstructure, particularly the fraction of polygonal ferrite, in the Nb–Ti microalloyed steel. Key findings include that increasing the heating rate from 3 °C/s to 30 °C/s enhances the kinetics of reverse transformation to austenite, resulting in a larger fraction of new ferrite and thus a higher proportion of polygonal ferrite in the post-annealed microstructure in most cases. Interestingly, in scenarios where recrystallization can occur by altering the initial microstructure, the combined evolution of recrystallized and new ferrite enlarges the fraction of polygonal ferrite at slower heating rates of 3 °C/s. It indicates that the contribution of recrystallization and reverse transformation on the evolution of polygonal ferrite depends on the interplay between initial microstructure and the heating rate. Further, the calculations of the austenite/ferrite interface velocity suggest that the accelerated reverse transformation to austenite, facilitated by increased heating rates, is little affected by kinetic transitions.

A phase-field model bridging near-equilibrium and far-from-equilibrium alloy solidification

Mapping to the appropriate Gibbs–Thomson (G–T) condition is essential for phase-field modeling to produce reliable and realistic solidification microstructures. However, existing phase-field models face challenges in simultaneously satisfying both near-equilibrium and far-from-equilibrium G–T conditions. This limitation restricts the applicability of phase-field methods in scenarios with a wide range of interface velocities, such as those observed in additive manufacturing. In this work, we propose a phase-field model that bridges both regimes by redefining each interfacial concentration field into two components: a conservative term representing long-range diffusion and a non-conservative term accounting for short-range redistribution within the diffuse interface. This formulation makes the model fully variational and analytically traceable through thin-interface analysis, allowing for accurate mapping to the G–T condition and determining model parameters. A key advancement of this model is the inclusion of free energy dissipation for short-range redistribution fluxes in the thin-interface limit, providing the necessary degree of freedom to reconcile both near-equilibrium and far-from-equilibrium G–T conditions. This capability is demonstrated by applying the model to simulate banded structures, effectively capturing the transition between near-equilibrium and far-from-equilibrium states.

A novel treatment of solute drag and solute trapping at a solid–liquid interface during rapid solidification of multicomponent alloys

AbstractIn response to the renewed interest in solute drag and solute trapping models fueled by their applications to additive manufacturing, a novel treatment is proposed to describe the diffusional behaviors of solute at a migrating solid–liquid interface during rapid solidification of multicomponent alloys. While the treatment is still built on irreversible thermodynamics and linear kinetic law, its novelty lies in breaking up the classical trans‐interface diffusional flux into two separate fluxes one is the transferred‐back flux with its ending point at the interface and the other is the bumping‐back flux with its starting point at the interface. This novel treatment entails three significant improvements in reference to the existing models. Firstly, it reveals that the degree of solute drag is dependent on the ratio of liquid diffusive speed over interface diffusive speed. Secondly, a novel relation between the distribution coefficient and interface velocity is derived. It amends the confusing behavior seen in Aziz’s without‐drag continuous growth model. Thirdly, the proposed treatment eliminates the need of prescribing the degree of solute drag parameter for the kinetic phase diagram calculation. The numerical solution to the proposed model is presented, and it is ready to be used for the kinetic phase diagram calculation.

A hybrid mesoscale-continuum approach to understand and predict melting kinetics of Al powders during laser processing

Abstract Laser interaction with metallic powders during additive manufacturing (AM) leads to fast heating and cooling rates that can affect the quality of the final products due to the formation of defects. One of the first steps towards predicting microstructures generated during AM, therefore, requires an accurate understanding of the laser energy deposition mechanisms that determine the melting kinetics at the level of individual powders. The critical challenge, however, is the availability of computational methods that can model the laser energy absorption, heat transfer, and the related microstructure evolution in individual metal powders at the length and time scales of AM. This manuscript demonstrates the capability of a novel scale-bridging methodology that combines the mesoscale quasi-coarse-grained dynamics (QCGD) simulations with a continuum two-temperature model (TTM) to account for the atomistic mechanisms of laser energy deposition and microstructure evolution and predict the kinetics of melting of individual powders at the experimental time and length scales. The scale-bridging capability of the hybrid QCGD-TTM simulations is demonstrated here by investigating the laser-induced microstructure evolution in aluminum powders with various sizes ranging from 200 nm to 20 µm. The analysis of the evolution of temperature, pressure, phase fraction, and melt fronts suggests the melting mechanism is heterogeneous due to the interaction with a laser, and the melting time is observed to decrease exponentially as the laser intensity increases. The solid-liquid interface velocity can be quantified to identify correlations with interface temperatures, and the predicted values satisfy the theoretically reported limits of crystal stability of metals against homogeneous melting. In addition, the pre-melting is found at the grain boundaries of 20 µm polycrystalline aluminum powder, while a minute contribution to melting is observed. This manuscript demonstrates the capability of the QCGD-TTM method to capture laser-powder interaction and allow the investigation of the kinetics of laser melting.

Immiscible non-Newtonian displacement flows in stationary and axially rotating pipes

We examine immiscible displacement flows in stationary and rotating pipes, at a fixed inclination angle in a density-unstable configuration, using a viscoplastic fluid to displace a less viscous Newtonian fluid. We employ non-intrusive experimental methods, such as camera imaging, planar laser-induced fluorescence (PLIF), and ultrasound Doppler velocimetry (UDV). We analyze the impact of key dimensionless numbers, including the imposed Reynolds numbers (Re, Re*), rotational Reynolds number (Rer), capillary number (Ca), and viscosity ratio (M), on flow patterns, regime classifications, regime transition boundaries, interfacial instabilities, and displacement efficiency. Our experiments demonstrate distinct immiscible displacement flow patterns in stationary and rotating pipes. In stationary pipes, heavier fluids slump underneath lighter ones, resulting in lift-head and wavy interface stratified flows, driven by gravity. Decreasing M slows the interface evolution and reduces its front velocity, while increasing Re* shortens the thin layer of the interface tail. In rotating pipes, the interplay between viscous, rotational, and capillary forces generates swirling slug flows with stable, elongated, and chaotic sub-regimes. Progressively, decreasing M leads to swirling dispersed droplet flow, swirling fragmented flow, and, eventually, swirling bulk flow. The interface dynamics, such as wave formations and velocity profiles, is influenced by rotational forces and inertial effects, with Fourier analysis showing the dependence of the interfacial front velocity's dominant frequency on Re and Rer. Finally, UDV measurements reveal the existence/absence of countercurrent flows in stationary/rotating pipes, while PLIF results provide further insight into droplet formation and concentration field behavior at the pipe center plane.

The evolution of the bubble collapse morphology between two cylinders within a confined space

This work investigates the dynamic bubble behaviors between two cylinders within a confined space using high-speed photographic experiments and Kelvin impulse theory. First, the evolution of the collapse morphologies of bubbles located at the origin and along the y axis between two cylinders is qualitatively investigated. The effects of the cylinder spacing and bubble ordinate on the characteristics of the bubble deformation and the liquid velocity are then explored. The variations of the bubble interface velocities, the roundness of the bubble cross section, and the bubble radius are quantitatively analyzed. The conclusions can be summarized as follows: (1) The experimental bubble collapse phenomena at the origin can be divided into three cases: hourglass-shaped collapse, “8”-shaped collapse, and capsule-shaped collapse. Bubble collapse at the y axis can also be divided into three scenarios: awl-shaped collapse, spindle-shaped collapse, and inverted triangle-shaped collapse. (2) The cylinder spacing and the bubble ordinate significantly affect the experimental bubble collapse behaviors and the theoretical liquid flow field. (3) High-velocity liquid regions are generated around the bubble when it oscillates freely, and the nearby cylinders always lead to low-velocity regions between them and the bubble. The closer the bubble is to the cylinder, the smaller the low-velocity regions and the larger the high-velocity regions.

Interplay Between Nucleation and Kinetics in Dynamic Twinning

Abstract In this work, we apply a phase-field modeling framework to elucidate the interplay between nucleation and kinetics in the dynamic evolution of twinning interfaces. The key feature of this phase-field approach is the ability to transparently and explicitly specify nucleation and kinetic behavior in the model, in contrast to other regularized interface models. We use this to study two distinct problems where it is essential to explicitly specify the kinetic and nucleation behavior governing twin evolution. First, we study twinning interfaces in 2D. When these interfaces are driven to move, we find that significant levels of twin nucleation occur ahead of the moving interface. Essentially, the finite interface velocity and the relaxation time of the stresses ahead of the interface allow for nucleation to occur before the interface is able to propagate to that point. Second, we study the growth of needle twins in antiplane elasticity. We show that both nucleation and anisotropic kinetics are essential to obtain predictions of needle twins. While standard regularized interface approaches do not permit the transparent specification of anisotropic kinetics, this is readily possible with the phase-field approach that we have used here.

A numerical model for the simulation of complex planar Newtonian interfaces

We present a numerical model for the simulation of complex planar interfaces at which moving solid objects can be immersed, reproducing a wide variety of experimental conditions. The mathematical model consists of the Navier-Stokes equations governing the incompressible viscous flow in the liquid subphase, the transport equation for the evolution of the surfactant concentration at the interface, and the interfacial stress balance equation. The equations are simplified by treating the problem as isothermal and the surfactant as insoluble. The bulk flow equations are discretized using a collocated finite volume method, while the interfacial flow equations are discretized using a finite area method. The Boussinesq-Scriven interface constitutive model and a variant form accounting for extensional viscosity are used to describe the extra surface stress tensor. The coupling between surfactant concentration, interfacial velocity, and bulk velocity is treated implicitly by solving the interfacial and bulk equations sequentially at each time step until a stopping criterion is satisfied. The motion of the solid is treated by an arbitrary Lagrangian-Eulerian method. The model has been implemented in the OpenFOAM framework and allows the incorporation of new interface models and solvers, making the developed new package a versatile and powerful tool in the field of computational rheology. Applications of the model include the numerical simulation of flow around objects, such as probes, immersed at a complex interface, reproducing given experimental conditions, and its use as a tool in the analysis and design of interfacial stress rheometers. Several test cases have been performed to validate the model by comparing the results obtained with analytical solutions and with numerical and experimental results available in the literature.

Growing particle in a solid matrix in presence of composition stress

The diffusion-controlled growth of a spherical particle embedded in a solid matrix of infinite size has been theoretically investigated for binary alloys, in the framework of the diffusion-under-stress formalism developed by Cahn-Larché. Assuming a composition stress develops in the particle, both concentrations of the diffusing species have been determined in the particle and in the matrix, as well as the interface velocity. The dependence on the composition stress and heterogeneous shear moduli of the concentrations in the particle and the interface growth rate has been characterized.

Far-from-equilibrium solid–liquid interfacial properties of aluminum

Simulating quantitatively far-from-equilibrium conditions, which is relevant to a host of rapid solidification processes, has remained a major challenge where theoretical models and physical mechanisms for far-from-equilibrium solid–liquid (SL) interface are essential. Herein, we investigate the effects of far-from-equilibrium state and external strain on SL interfacial properties by using capillary fluctuation method and models based on transition rate theory. Under an extreme temperature gradient (TG), both SL interfacial stiffness (S) and SL interface velocity (v) are found to increase with TG. The nonlinear relationship between v and temperature is revealed over a large undercooling range (640 K). It is found that an external strain (ϵ) of 1%–3% could decrease S by 10%–30%. v is found to increase with external strains at large undercooling. Tensile strains decrease the activation energy (Q) and viscosity, thus facilitating SL interface movement. A strain-dependent Gibbs–Thomson condition is proposed by incorporating linear S-ϵ and Q-ϵ relations. Our systematically theoretical discussion on the far-from-equilibrium SL interfacial properties could provide a predictive guideline on SL interface behavior in the additive or extreme manufacturing.

Global variability of the composition and temperature at the 410-km discontinuity from receiver function analysis of dense arrays

Seismic boundaries caused by phase transitions between olivine polymorphs in Earth's mantle provide thermal and compositional markers that inform mantle dynamics. Seismic studies of the mantle transition zone often use either global averaging with sparse arrays or regional sampling from a single dense array. The intermediate approach of this study utilizes many densely spaced seismic arrays distributed around the globe. We systematically compute teleseismic P-to-S receiver functions for each seismic array and invert for the 1-D seismic velocity structure of the mantle transition zone beneath each array to facilitate a comparison between densely sampled regions. We stack 3,600 receiver functions on average at 67 arrays in total. The stack is used in a probabilistic inversion to estimate the mantle transition zone interface depths and velocities beneath each array. We focus on the 410-km discontinuity (410) because it is a prominent seismic interface that is clearly linked to a single mineral phase transition between olivine and wadsleyite. The depths and velocity contrasts of the 410 are mapped to temperatures and compositions using mineral physics constraints. The depth of the 410 ranges from ∼405–440 km, which is consistent with a ∼360 K temperature range in a dry mantle and a ∼260 K temperature range in a wet mantle (2 wt. % water). The Vs contrast across the 410 ranges from ∼2.5–8 %, which is consistent with ∼20–70 vol. % olivine composition in a dry mantle and ∼25–80 vol. % in a wet mantle. The bulk composition of the upper mantle near the 410-km discontinuity is typically considered to be well-mixed because there is no thermodynamic impediment to convection at the olivine to wadsleyite phase transition. However, the wide range of inferred olivine content from our study suggests that there are large lateral variations in the bulk composition of the upper mantle near the 410-km discontinuity.

Influence of precipitation infiltration recharge on hydrological processes of the karst aquifer system and adjacent river

Understanding the hydrological processes of the karst aquifer system (KAS) and adjacent river can further accurately evaluate karst water storage. However, the mechanism of the KAS and adjacent river hydrological processes under precipitation infiltration recharge conditions, the micro-flow behavior of groundwater in the KAS, and changes in media saturation remain unclear. This study coupled the KAS and adjacent river through the Volume of Fluid (VOF), simulated the flow behavior of groundwater in different medium of the KAS and coupled the free flow process of the adjacent river by using the multiphase Darcy-Brinkman-Stokes (DBS) equation, applied the van Genuchten-Mualem and van Genuchten-modified Mualem equations to characterize the seepage processes in soil. The results indicate that the saturation of different porous media controlled by recharge intensity directly influences the flow behavior and flow paths of the porous media. The main groundwater flow path under low precipitation intensity (b=3) is primarily the lower porous medium, while under moderate precipitation intensity (3<b≤8), the main flow path of groundwater is the karst conduit. During heavy precipitation (8<b≤12), due to the limited capacity of karst conduit, they cannot bear the large amount of groundwater supplied from upper porous medium. The peak conduit saturation in laminar flow is 0.3 lower than that in turbulent flows. Under laminar flow conditions, the conduit drainage leads to a rapid decrease in saturation, making it easier for porous media to recharge to the conduit and discharge towards the adjacent river. The turbulent state conduit maintains a high saturation recession, but the discharge is consistently lower than laminar flow. The variation process line of average flow velocity and interfacial flow velocity are obtained using the DBS method and N-S simulation method respectively. There is a certain discrepancy between the simulation results of the two methods since the N-S simulation scheme dose not consider the water retention characteristics of the porous medium.

Structures in grain-refined directionally solidified hypoeutectic Al-Cu alloys: Benchmark experiments under microgravity on-board the International Space Station

Benchmark solidification experiments were successfully performed under microgravity conditions on-board the International Space Station (ISS) within the ESAprogramme CETSOL (Columnar-to-Equiaxed Transition in SOLidification Processing). Cylindrical samples of grain-refined Al-4wt.%Cu, Al-10wt.%Cu and Al-20wt.%Cu alloys were directionally solidified in a gradient furnace to investigate columnar and equiaxed dendritic growth structures as well as the columnar to equiaxed transition under diffusive conditions. The determination of temperature gradients; interface velocities; and cooling rates at liquidus, solidus, and eutectic front positions provides well-defined thermal experimental characterization. The evaluation of the flight samples demonstrates that no significant macrosegregation along the sample axis occurred and no radial effects were observed. Therefore, purely diffusive solidification behaviour without any residual melt convection can be assumed for these microgravity experiments. The analyses of the microstructure in longitudinal cross-sections show dendritic structures without any pore formation and the averaged eutectic fraction is largely constant along the sample. The samples of refined Al-4wt.%Cu alloy show a sharp CET from columnar dendrites to a fine equiaxed steady-state grain structure whereas in the samples of refined Al-10wt.%Cu and Al-20wt.%Cu alloy, only equiaxed dendritic grain growth is observed. A quantitative analysis of the equiaxed grain morphology shows, that the shapes of the equiaxed dendrites depend on the applied temperature gradient, but the grain sizes in radial and longitudinal directions are identical. Therefore, a fully equiaxed dendritic growth structure without dendrite elongation was obtained. Compared to experiments in microgravity with non-refined Al-Cu alloys the average equiaxed grain size is about three times smaller.

Bridging molecular dynamics and additive manufacturing: A study of Al-12 at% Si alloy solidification dynamics

This manuscript provides a detailed analysis of the molecular dynamics of the directional solidification process in Aluminum-Silicon (Al-12 % at Si) alloys, with a particular emphasis on applications in additive manufacturing. Utilizing molecular dynamics (MD) simulations, the study examines large systems containing 5–15 million atoms to investigate various facets of the solidification process. These include the dynamics of interface motion and the formation of Silicon (Si) precipitates. The research reveals significant variations in interface velocities and orientations across different thermal gradients and growth rates, underscoring the intricate interaction between thermal and solute flows in the microstructural development of Al-Si alloys. These findings are vital for comprehending and refining the solidification process in additive manufacturing, ultimately enhancing the mechanical strength and reliability of the final products. The paper highlights the critical role of microstructure control in printed metals and proposes future research directions, aiming to apply these insights to more complex alloy compositions and manufacturing contexts. In the concluding phase, the scikit-image library was employed to analyze dendritic formations in solidifying Al-Si alloys using MD simulations. This analysis delineates trends in dendritic count, spacing, perimeter, and area over time, offering essential perspectives on the solidification process and its implications for the alloy's microstructure and mechanical characteristics. The Si content in the Al-Si alloy used can be considered eutectic in the solidified structure. Si atoms are predominantly located at grain boundaries and precipitate regions. Coordination number analysis further confirms the presence of Si in these locations. This microstructure, characterized by a primary Al/Al-Si matrix and Si-rich eutectic regions, aligns with experimental observations in rapid solidification processes in additive manufacturing.

Spatiotemporal Filter Velocimetry With Arbitrary-Shaped Measurement Region For Accurate Measurement In The Vicinity Of A Boundary

Viscous stress at a boundary or an interface is a source of drag acting on a body or a fluid particle and therefore its measurement is of great importance for understanding the motion of the body or the fluid particle. In this study, spatiotemporal filter velocimetry (SFV: Hosokawa &amp; Tomiyama, 2012) is extended to arbitrary quadrilateral measurement areas fitted to an interface shape for accurate measurement of flow about a deformed drop, and it is applied to flows about single drops of glycerol-water solution falling in stagnant silicon oil under clean and contaminated conditions. Figure 1 shows the trajectories of tracer particles and the measured velocity distributions. No separation is observed for the spherical and ellipsoidal drops. On the other hand, the stagnant region is observed in the dimple region of the tail of the cap drop. These results clearly indicate that the flow about the deformed drop is successfully measured by SFV with arbitrary quadrilateral measurement areas. Figure 2 shows the trajectories of tracer particles and the measured velocity distributions of single ellipsoidal drops in clean and contaminated systems. Triton X-100 was used as the surfactant and its concentration C in the drop ranges from 0.0 to 0.1 mol/m3 . The drop tail becomes flat and then slightly dimpled shape, and the internal circulation becomes weak as C increases. The internal circulation remains even at the high surfactant concentration condition under which the internal circulation in single spherical drop is fully damped (Hosokawa et al., 2017). We also evaluate interfacial velocity, interfacial shear stresses, the Marangoni stress and surfactant concentration at the interface from measured velocity distributions in the vicinity of the interface. As a result, we confirmed that SFV enables us to measure velocity distribution about a single deformed drop and enables us to evaluate interfacial velocity, interfacial shear stresses, the Marangoni stress and surfactant concentration at the interface.