Fluid Movement Research Articles

Research on 2D Animation Simulation Based on Artificial Intelligence and Biomechanical Modeling

Animation techniques have been completely transformed by the union of Artificial Intelligence (AI) and biomechanical modeling, particularly in 2D animation. This study looks at a combination of AI and biomechanics to address the challenges of simulating 2D animation. Current approaches in 2D animation often struggle to achieve lifelike and fluid movements, especially when representing complex motion or interaction. These traditional techniques rely on manual keyframing or physics simulation, which may be time-consuming and do not provide the rich detail needed for realism in animations. To meet these aspects, this study suggested 2D animation using Artificial Intelligence with Biomechanical Modeling (2D-AI-BM). Our approach thus harnesses Deep Neural Network (DNN) for moving forecasts and improvement using biopsychological principles to help us imitate natural human actions better. In addition to character animation, it could apply to interactive storytelling and educational simulations. As a result, animators get more control over motion generation while drastically reducing the necessity for manual intervention through this fusion of AI and biomechanics, which smoothens the production pipeline for animations. This paper considers several important metrics to evaluate the proposed approach’s effectiveness, including user satisfaction, computational efficiency, motion smoothness and realism. Comparative studies with classical animation methods showed that the method generates realistic movements on 2D characters while saving time during production. The numerical findings exemplify that the recommended 2D-AI-BM model improves an accuracy rate of 97.4%, computational efficiency ratio of 96.3%, motion control ratio of 95.4%, pose detection ratio of 94.8% and scalability ratio of 93.2% compared to other popular techniques.

Experimental research on the acoustic detection of different fracture characteristics

Fractures serve as critical pathways for fluid movement and storage within tight reservoirs, playing a pivotal role in the exploration and development of geologic resources. The intricate nature of these fractures, often manifesting as complex belts due to the influence of multifaceted tectonic activities, complicates the understanding of how wave propagation is altered by various fracture characteristics. To address this challenge, we carry out physical experiments and finite-difference numerical simulation studies on scaled physical models of wells based on acoustic logging techniques. This study meticulously examines the interplay between different fracture attributes and the behavior of the S and Stoneley waves, providing a quantitative analysis of the fracture width, density, and ductility. Our findings reveal that the amplitude of the direct Stoneley wave exhibits an exponential decline with an increase in the equivalent fracture width. With a constant equivalent fracture width, an increase in the number of fractures leads to a higher amplitude of the direct Stoneley wave. Moreover, as the radius of the fracture extension expands, the relative amplitude of the Stoneley wave diminishes, following a logarithmic trend.

Non-Darcian MHD flow of ternary-hybrid Cu-TiO2-Al2O3/H2O nanofluid over an inclined sheet with activation energy

This study has been carried out to understand the unsteady MHD slip flow of a water-based ternary hybrid nanofluid including spherical Cu, titanium dioxide TiO2 and cylindrical Al2O3 nanoparticles across an angled sheet. The complicated scenario above investigates how ternary-hybrid nanofluid behaves when it is stretched across an inclined surface in the existence of a magnetic field. In complex thermal systems such as energy-generating technologies and cooling mechanisms, an understanding of this relationship is essential. In the existence of first-order velocity slip, the heat transfer has been examined taking into account the non-Darcy Porous media, activation energy, and heat source. The study is more accommodating because of the Soret effect. The relevant similarity transformations are applied in primary equations and a built-in bvp4c program is employed for solutions. The effectiveness of the numerical approach is demonstrated by a thorough agreement with results that have been published in the past. The key conclusions are as follows: greater values of the first order slip parameter cause the flow to slow down; an increase in Soret number causes the flow to speed up; and in both scenarios—that is, with and without velocity slip, fluid movement drops caused by higher values of the chemical reaction. The Forchheimer parameter lowers fluid velocity while activation energy enhances the fluid concentration.

High correlated color temperature artificial lighting impairs retinal pigment epithelium integrity and chloride ion transport: A potential mechanism for choroidal thinning

Among the environmental factors contributing to myopia, the role of correlated color temperature (CCT) of ambient light emerges as a key element warranting in-depth investigation. The choroid, a highly vascularized and dynamic structure, often undergoes thinning during the progression of myopia, though the precise mechanism remains elusive. The retinal pigment epithelium (RPE), the outermost layer of the retina, plays a pivotal role in regulating the transport of ion and fluid between the subretinal space and the choroid. A hypothesis suggests that variations in choroidal thickness (ChT) may be modulated by transepithelial fluid movement across the RPE. Our experimental results demonstrate that high CCT illumination significantly compromised the integrity of tight junctions in the RPE and disrupted chloride ion transport. This functional impairment of the RPE may lead to a reduction in fluid transfer across the RPE, consequently resulting in choroidal thinning and potentially accelerating axial elongation. Our findings provide support for the crucial role of the RPE in regulating ChT. Furthermore, we emphasize the potential hazards posed by high CCT artificial illumination on the RPE, the choroid, and refractive development, underscoring the importance of developing eye-friendly artificial light sources to aid in the prevention and control of myopia.

Modification in airfoil’s tonal noise using periodic suction-blowing excitation

This paper examines the modifications in the flow and sound fields due to the application of a periodic suction-blowing excitation strip on the top and bottom surfaces of a NACA0012 airfoil. The flow and sound fields have been directly computed (DNS approach) by solving unsteady, two-dimensional compressible Navier–Stokes equations using physical dispersion relation preserving schemes. The flow approaches the airfoil at a Reynolds number of 5000 and 5o angle of attack. In the no-excitation case, the sound is mainly created by the lift and drag dipole equivalent sources associated with vortex shedding. However, the application of suction-blowing excitation results in two additional sound sources: monopole-equivalent sound sources due to fluid movement in and out of the airfoil surface and the drag dipole-equivalent sound sources due to periodic change in the airfoil’s effective cross-sectional area. The combined effects of these sound sources result in significant mitigation of sound on the suction side of the airfoil. The excitation amplitude and forcing frequency effects on sound field modifications have been studied in depth. Beats of sound have been observed when the forcing frequency is close to the excitation frequency.

Comparative Evaluation of Dissolution Performance in a USP 2 Setup and Alternative Stirrers and Vessel Designs: A Systematic Computational Investigation.

The dissolution testing method described in the United States Pharmacopeia (USP) Chapter ⟨711⟩ is widely used for assessing the release of active pharmaceutical ingredients from solid dosage forms. However, extensive use over the years has revealed certain issues, including high experimental intervariability observed in specific formulations and the settling of particles in the dead zone of the vessel. To address these concerns and gain a comprehensive understanding of the hydrodynamic conditions within the USP 2 apparatus, computational fluid dynamic simulations have been employed in this study. The base design employed in this study is the 900 mL USP 2 vessel along with a paddle stirrer at a 50 rpm rotational speed. Additionally, alternative stirrer designs, including the hydrofoil, pitched blade, and Rushton impeller, are investigated. A comparison is also made between a flat-bottom tank and the USP round-bottom vessel of the same volume and diameter. Furthermore, this work examines the impact of various parameters, such as clearance distance (distance between the bottom of the impeller and bottom of the vessel), number of impeller blades, impeller diameter, and impeller attachment angle. The volume-average shear rate (Stv), fluid velocity (Utv), and energy dissipation rates (ϵtv) represent the key properties evaluated in this study. Comparing the USP2 design and systems with the same stirrer but flat-bottom vessel reveals more homogeneous mixing compared to the USP2 design. Analyzing fluid flow streamlines in different designs demonstrates that hydrofoil stirrers generate more suspension or upward movement of fluid compared to paddle stirrers. Therefore, when impellers are of a similar size, hydrofoil designs generate higher fluid velocities in the coning area. Furthermore, the angle of blade attachment to the hub influences the fluid velocity in the coning area in a way that the 60° angle design generates more suspension than the 45° angle design. The findings indicate that the paddle stirrer design leads to a heterogeneous shear rate and velocity distributions within the vessel compared with the other designs, suggesting suboptimal performance. These insights provide valuable guidance for the development of improved in vitro dissolution testing devices, emphasizing the importance of optimized design considerations to minimize hydrodynamic variability, enhance dissolution characterization, and reduce variability in dissolution test results. Ultimately, such advancements hold potential for improving in vitro-in vivo correlations in drug development.

Use of Function Diagrams in Physiology Education: Nessie the Nephron and Navigating the Lochs

Function diagrams focus on physiological concepts rather than associated structures and can serve as elaboration tools and mnemonic aids. A function diagram prototype of the gastrointestinal system was recently described (Wilson & Barrett, Adv Physiol Educ, 45:264–268, 2021). Currently, a functional diagram of the glomerulus, nephron, urinary system, and bladder is proposed. Colloquially named “Nessie the Nephron” to loosely capture the looping structure and illusive understanding of renal blood flow, glomerular filtration, and epithelial transport for the student, not to mention the nearly mythical countercurrent multiplier. “Navigating the Lochs” references Nessie’s possible habitat and more importantly the movement and storage of the modified ultrafiltrate from the nephron. The primary analogies that form the structure of this function diagram are: Rain Barrel, Soaker Hose, & Hose Nozzle (afferent and efferent blood flow and filtration pressure); Water Purification System (glomerular filtration barrier forming multiple step filtration process involving the capillary, basement membrane, and podocytes); Mixed Recycling Machine (proximal tubule individual, co-, and bulk transport); Desiccator & Briner (thin descending limb removal of water and thin/thick ascending limb movement of salt); Conveyor Belt Picker (distal nephron selective ion transport); and Concentrator (collecting duct water and urea transport). The primary analogies that elaborate “Navigating the Lochs” are Aqueduct & Cistern System (fluid movement and collection); and Pressure Gauge, Syringe Bulb, and Two-valve Plumbing (bladder storage and micturition). Complimenting these analogies is the rich potential for inclusion of clinical and comparative applications and examples to link previous knowledge and strengthen memories for future retrieval. University of Kentucky College of Medicine. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Identifying some regularities of the turbulent steady-state plane-parallel motion of incompressible fluid at the entrance length

This paper investigates the structural changes in the turbulent motion of an incompressible fluid in the hydrodynamic entrance region of plane-parallel pressure motion. Movement in pressure hydromechanical systems usually occurs in a turbulent regime. Studying the patterns of changes in hydrodynamic parameters under conditions of stationary turbulent pressure motion in the inlet region is a very urgent task. The study was carried out on the basis of boundary layer equations. Taking into account the dependence of changes in the kinematic viscosity coefficient that occur between layers of fluid, a boundary value problem was formed. Analytical solutions have been obtained that make it possible to obtain patterns of changes in velocity and pressure in any effective flow section. Based on the general conclusions of the study, solutions were found for two cases: a) the velocity of the fluid entering the cylindrical pipe is constant; b) the velocity of the incoming fluid has a parabolic distribution. For these cases, using computer analysis of the data obtained, general graphs of velocity changes were constructed in various sections along the hydrodynamic entrance region. These graphs, which display the change in velocity along the entire length of the inlet, make it possible to obtain the velocity of fluid movement at any point along the inlet length and estimate the length of the transition zone. The results obtained are among the least studied issues of classical fluid mechanics and are of important theoretical interest. The results obtained are applicable for the correct construction of the hydrodynamic entrance region of machinery. A calculation formula has been obtained to determine the length of the hydrodynamic inlet region

Physical analysis and thermal case of magnetized fluid flow and heat transfer via stretchable cylinder: Hall impact and entropy generation

The study of fluid flow in cylindrical shapes under the effect of electric fields is of utmost importance because of its vast applications in industrial, agricultural, and biomedical domains, as well as in drilling machines, equipment, transport brakes, and vehicles. The purpose of this research is to analyze the influence of Hall impacts, slippage effects, and thermal relaxation time on the magnetohydrodynamic flow near an extended cylinder or flat plate. An assessment of entropy generation is carried out. Results are determined by the process of elongating a planar surface and a cylindrical object. The velocity field and entropy production are greater in the case of a stretched cylinder compared to a stretching flat plate. The choice of an appropriate stretching surface may have an impact on the thermal conductivity of the boundary layer. Velocity, temperature, and entropy are influenced by several factors including the Eckert number, thermal relaxation time, transverse curvature, magnetic field, Hall effect, molecular slip, and mixed convection parameters. These characteristics influence the movement of fluid, the transfer of heat, the measure of disorder (entropy), and the Bejan number. The variables mentioned cause changes in skin friction and Nusselt values. The Hall effect has advantages in reducing friction and enhancing heat transfer in industrial and technical processes.

Geophysical Characterization and Seepage Detection of the Chimney Rock Dam Embankment Near Salina, Oklahoma

The operator of Chimney Rock Dam observed the emergence of increasing seepage at the toe of the dam when the water level in the reservoir exceeded a particular elevation. However, the source and the pathways of the seepage were not identified. To address this issue, integrated geophysical methods were employed to delineate the different units of the dam embankment and identify potential seepage zones and pathways. The methods utilized in this study included electrical resistivity tomography (ERT), self-potential (SP), and multichannel analysis of surface waves (MASW). The ERT profiles revealed variations in the dam’s fill properties, including areas with anomalously low resistivity, interpreted as zones of relatively high moisture content. The two long SP profiles conducted along the dam embankment displayed similar spatial correlations with these low-resistivity zones, suggesting potential preferential seepage pathways. The SP map generated from a suite of parallel SP profiles conducted over the abutment depicts a pattern of positive background and negative potential anomalies, which may suggest fluid movement or seepage potential. The MASW profile along the top of the dam characterized an upper low shear-wave velocity layer corresponding to the top dry section of the embankment underlain by a higher shear-wave velocity layer, interpreted as saturated zone. The utilized geophysical methods successfully characterized the different materials of the embankment and identified zones of potential seepage.

Bödewadt flow of thermally radiative hybrid nanofluid under the implication of horizontal magnetic field

It is a known fact that the implication of uniform magnetic field in transversal direction to fluid flow concerns the stabilization of velocity field and deterioration of heat transfer rate. It is now recognized that the applied uniform horizontal magnetic field is useful for stabilizing/destabilizing the flow rate, which is principally rely upon the direction angle such as cooling/heating the disk surface. Considering this, the present study investigates an incompressible three-dimensional Bödewadt flow above a stretchable with an implication of horizontal magnetic field. The Bödewadt flow defines a uniform and stable angular movement of fluid at sufficient large distance from the stationary surface. Such flow is balanced by the Centrifugal forces and is featured through radial pressure gradient. The radiative heat transfer attributes are characterized by the hybrid nanofluid, which is composition of Copper ( Cu ) and Titanium Dioxide ( Ti O 2 ) with water ( H 2 O ) as base fluid. A well-known approach of similarity variables is adopted to first normalize the flow model and then the resultant system of coupled non-linear ordinary differential equations is solved by Runge-Kutta-Fehlberg (RKF) MATLAB built-in package. The graphical results on flow and thermal fields are sketched for different values of dimensionless quantities. It is observed that direction angle in terms of horizontally applied magnetic field has stabilizing impact along radial axis close to the 0 ° or 90 ° , whereas destabilizing influence of direction angle is noticed between 30 ° − 60 ° . The temperature field is enhanced by the enlarged parametric values of thermal Biot number and solid volume fractions. Local Nusselt-number is increased at the disk surface by the radiation parameter.

Dynamic trend of lung fluid movement during exercise in heart failure: From lung imaging to alveolar-capillary membrane function

BackgroundIn chronic heart failure (HF), exercise-induced increase in pulmonary capillary pressure may cause an increase of pulmonary congestion, or the development of pulmonary oedema. We sought to assess in HF patients the exercise-induced intra-thoracic fluid movements, by measuring plasma brain natriuretic peptide (BNP), lung comets and lung diffusion for carbon monoxide (DLCO) and nitric oxide (DLNO), as markers of hemodynamic load changes, interstitial space and alveolar-capillary membrane fluids, respectively. Methods and resultsTwenty-four reduced ejection fraction HF patients underwent BNP, lung comets and DLCO/DLNO measurements before, at peak and 1 h after the end of a maximal cardiopulmonary exercise test. BNP significantly increased at peak from 549 (328–841) to 691 (382–1207, p < 0.0001) pg/mL and almost completely returned to baseline value 1 h after exercise. Comets number increased at peak from 9.4 ± 8.2 to 24.3 ± 16.7, returning to baseline (9.7 ± 7.4) after 1 h (p < 0.0001). DLCO did not change significantly at peak (from 18.01 ± 4.72 to 18.22 ± 4.73 mL/min/mmHg), but was significantly reduced at 1 h (16.97 ± 4.26 mL/min/mmHg) compared to both baseline (p = 0.0211) and peak (p = 0.0174). DLNO showed a not significant trend toward lower values 1 h post-exercise. ConclusionsModerate/severe HF patients have a 2-step intra-thoracic fluid movement with exercise: the first during active exercise, from the vascular space toward the interstitial space, as confirmed by comets increase, without any effect on diffusion, and the second, during recovery, toward the alveolar-capillary membrane, clearing the interstitial space but worsening gas diffusion.

Understanding and Modeling the Pathophysiology of Hydrocephalus: In Search of Better Treatment Options

Hydrocephalus is caused by an overproduction of cerebrospinal fluid (CSF), an obstruction of fluid movement, or improper reabsorption. CSF accumulation in the brain’s ventricles causes ventriculomegaly, increased intracranial pressure, inflammation, and neural cell injury. Hydrocephalus can arise from brain trauma, hemorrhage, infection, tumors, or genetic mutations. Currently, there is no cure for hydrocephalus. Treatments like shunting and endoscopic third ventriculostomies are used, but, unfortunately, these therapeutic approaches require brain surgery and have high failure rates. The choroid plexus epithelium (CPe) is thought to be the major producer of CSF in the brain. It is a polarized epithelium that regulates ion and water movement from a fenestrated capillary exudate to the ventricles. Despite decades of research, control of electrolyte movement in the CPe is still not fully understood. This review discusses important transporters on the CPe, how some of these are regulated, and which of them could be potential targets for hydrocephalus treatment. To advance the development of hydrocephalus treatments, physiologically relevant preclinical models are crucial. This review covers some of the current animal and cell culture methods used to study hydrocephalus and highlights the need to develop standardized preclinical models that are used by multiple investigators in order to replicate critical findings and resolve controversies regarding potential drug targets.

An iterative Kalman filter-based method for traveltime tomography

Abstract In addition to directly determining the inverted velocity, it is crucial to assess the uncertainty (or confidence) of the relevant velocity imaging results. This is especially true when dealing with time-lapse seismic data, which play a crucial role in detecting changes in fluid movement in petroleum reservoirs. In this study, we developed an iterative Kalman filter-based method to monitor time-lapse changes in the subsurface using traveltime tomography. Our approach considers the uncertainty of the results. We successfully verified the validity of our proposed method through synthetic crosshole and time-lapse tests. Our iterative Kalman filter-based method provides reasonable reconstruction results suitable for accessing uncertainties, and the algorithm can be used to monitor changes in the subsurface medium.

From Streamline to Pathline: Visualizing Particle Trajectories Under Changing Velocity Fields

Summary Monitoring of subsurface fluid motion is critical for optimizing hydrocarbon production and CO2 sequestration. Streamlines are frequently used to visualize fluid flow; however, they provide only an instantaneous snapshot of the velocity field and do not offer an exact representation of fluid movement under varying field conditions. In contrast, pathlines are constructed by tracking individual particles within the fluid, enabling us to trace the movement of these particles as they traverse through changing velocity fields. Pathline is the trajectory that an individual fluid particle follows in the reservoir. It can be thought of as “recording” the path of a fluid element in the flow field for a given time interval. Pathlines are distinct from streamlines which represent a snapshot of the velocity field at a given instant. The direction the path takes is determined by the streamlines at a specific instant. To start with, streamlines are traced based on the grid face fluxes of finite-difference simulation. Streamline tracing continues till the time of flight equals the current time. The endpoints of the current streamlines become the starting points for the next tracing period. Thus, our formulation incorporates changing flow fields, and the process is repeated for each time interval until the end. The proposed injection monitoring method is tested using a 3D field-scale model with complex geologic features to demonstrate its power and utility. The pathlines were compared with streamlines, as well as the water saturation distribution. Three scenarios are tested: a constant well schedule, a changing well schedule with partial shut-in, and a changing well schedule with a whole field cessation. Results indicate that the pathline provides a more accurate swept volume, consistent with saturation distribution. The robustness of our algorithm and implementation is demonstrated with a complex embedded discrete fracture model (EDFM) to visualize flow patterns in discrete facture network. Pathlines display the fluid flow across fractures and are subsequently used to explore the sweep efficiency and the well connectivity.

Projection of 4D seismic onto the ensemble observation subspace for data assimilation

Time-lapse (4D) seismic data offer valuable insights into fluid movements and pressure changes within reservoirs, thus aiding the updating of numerical models used in hydrocarbon recovery and geological CO2 storage. However, it is essential to characterize both the uncertainties in the data and the limitations in the forward model to effectively utilize this information. In the context of ensemble-based data assimilation methods, this objective is accomplished through the utilization of the data-error covariance matrix, denoted as Ce. The selection of an appropriate Ce is of paramount importance, as it determines the level of accuracy required to match the data and influences the relative weight assigned to various data sources and prior information during the computation of model updates.Despite significant efforts, the practical estimation of Ce, accounting for both data and model errors, remains a challenging task. This paper presents a novel methodology for estimating Ce within an ensemble-based 4D seismic data assimilation framework. The approach involves projecting observed seismic data onto the subspace defined by predicted data from the prior ensemble and estimating Ce based on the residuals—the difference between observed and projected 4D seismic data. The proposed methodology is tested through application with actual data from three real-world reservoir cases.

Design and Simulation of the Biodiesel Process Plant for Sustainable Fuel Production

The biodiesel production process is extensively studied in the literature, focusing on mechanisms, modeling, and economic aspects, yet plant design and fluid flow losses remain underexplored areas. The study addressed this gap by designing a biodiesel production plant, analyzing flow losses, and developing a pipe network and suitable pump models. In this study, an integration of biodiesel production plant design and simulation of continuous production of Calophyllum inophyllum biodiesel was investigated. Biodiesel production encompasses complex stages that involve systematic planning and system design. The goal of the plant design is to reduce the losses that occur during the conversion process, which can reduce the capital cost of the plant. A few assumptions were made when selecting biodiesel plant materials, such as pipes, pumps, fittings, and bends. These assumptions were based on considerations of the biodiesel fluid properties and pressure requirements. On the other hand, Aspen Plus was used to simulate the biodiesel production process. Calophyllum inophyllum was considered oil as the biodiesel feedstock and was inputted to the Aspen Plus as triglyceride composition. The simulation was carried out with rigorous kinetic reactions using the Non-Random Two-Liquid (NRTL) method to predict the liquid equilibrium in the reactor. Results revealed that the designed steel pipe meets safety requirements with a bursting pressure of 49.68MPa, capable of withstanding the maximum pressure of 4 bar and turbulent flow conditions. Additionally, the selected pump satisfies the required head and flow rate, ensuring efficient fluid movement. Moreover, simulation results closely matched experimental data, and 88% of biodiesel yield was recorded.

Splay aligned liquid crystal network photoactuators for integrated microfluidic pumps

As lab-on-a-chip devices aim to incorporate complex and multi-step microfluidic workflows, active fluid control within these platforms is critical. We use a splay aligned liquid crystal network (LCN) photoactuator, capable of deformation upon blue light illumination, as a stimuli responsive material to create integrated fluidic elements. After optimization of the manufacturing parameters, a well-defined actuator material is attained. Illumination with a 455 nm light emitting diode (LED) at 41 mW cm−2 achieves deflection of a 3 × 8 × 0.05 mm LCN film by 380 µm, generating forces of 1.1 mN. The actuator response is stable over time and scalable by light intensity, temperature, and size of the LCN film. By combining with a polydimethylsiloxane (PDMS) membrane, integration into a microfluidic chip is demonstrated and fluid movement of 77 nL in a 2 s stroke is attained. In a pumping setup, the LCN film functions as pumping membrane and two passive PDMS check valves complete the integrated micropump. Constant pumping rates of 0.1 µL min−1 are achieved. An advantage of this micropump setup lies in the non-contact actuation method, which allows for easy integration into microfluidic chips, without the need for chip-to-world connections. Furthermore, with the simple manufacturing procedure and the low operating power, important requirements for application in point-of-care settings are fulfilled.

Hydraulic tortuosity of porous media: comparison of different modeling methods

Abstract Hydraulic tortuosity is a crucial parameter affecting the movement of fluid in porous media. Currently, researchers have used different methods to construct porous media models and studied the variation of hydraulic tortuosity with porosity. In this paper, we use Monte Carlo random particle, quartet structure generation set (QSGS), and CT-scan reconstruction to construct porous media models with different porosity. The finite element method is used to simulate the fluid passing through the models. The effectiveness of the QSGS algorithm in constructing porous media is verified. The hydraulic tortuosity of the three types of model is computed using the streamline length ratio method, and its variation law with porosity is explored. The results show that the change law of the three models is consistent. The law of power function change is satisfied between the two for all models, which means the increase in porosity causes a decrease in tortuosity. Different models are constructed to explore the effect of tortuosity on permeability. An increase in tortuosity results in a smaller permeability when other conditions are equal. This paper aims to provide effective methods for constructing porous media models and a reference for studying hydraulic tortuosity.

Insights into fluid migration during the 2021 La Palma eruption using seismic noise interferometry

Ambient noise correlation analyses are largely used to monitor temporal medium changes generally associated with stress field variations and/or fluid movement. Here, we analyze the 2021 eruption of La Palma, the most active island in the Canary archipelago, to study its effects on the structure in a post-eruptive stage. To date, most of the studies, whether in volcanic environments or other geological systems, focus on determining seismic velocity changes that can be associated with precursory signals. In our study, we are interested in localizing the medium changes that permit constraining the depth of the most affected structure and suggesting possible mechanisms capable of inducing such alterations. The auto- and cross-correlation functions were computed using the phase cross-correlation strategy. The correlations were linearly stacked using a 3-day sliding window. The combination of these two approaches proved to render the best results. The analysis of 3 years of data resulted in the detection of occasional decorrelation before the eruption, followed by a well-defined decoherence period after the eruption. In addition, the relationship between the waveform correlation and lag time, using autocorrelations from before and after the eruption, permits identifying phase shifts and waveform distortion, which are sensitive to different parameters and, thus, have great importance in inferring the possible mechanism. Phase shifts occur when there is only velocity change without changing the structure, whereas waveform distortion is caused by a structural (geological) change. We also inferred the depths at which the most significant medium alterations occur. We observed that the decorrelation occurs at lag times corresponding to changes localized in depth. The surface structure appears to not have undergone significant medium changes for depths until approximately 8 km, either before or after the eruption.