Fluid Flow Research Articles

Permeability estimation for deformable porous media with convolutional neural network

Purpose Accurately evaluating fluid flow behaviors and determining permeability for deforming porous media is time-consuming and remains challenging. This paper aims to propose a novel machine-learning method for the rapid estimation of permeability of porous media at different deformation stages constrained by hydro-mechanical coupling analysis. Design/methodology/approach A convolutional neural network (CNN) is proposed in this paper, which is guided by the results of finite element coupling analysis of equilibrium equation for mechanical deformation and Boltzmann equation for fluid dynamics during the hydro-mechanical coupling process [denoted as Finite element lattice Boltzmann model (FELBM) in this paper]. The FELBM ensures the Lattice Boltzmann analysis of coupled fluid flow with an unstructured mesh, which varies with the corresponding nodal displacement resulting from mechanical deformation. It provides reliable label data for permeability estimation at different stages using CNN. Findings The proposed CNN can rapidly and accurately estimate the permeability of deformable porous media, significantly reducing processing time. The application studies demonstrate high accuracy in predicting the permeability of deformable porous media for both the test and validation sets. The corresponding correlation coefficients (R2) is 0.93 for the validation set, and the R2 for the test set A and test set B are 0.93 and 0.94, respectively. Originality/value This study proposes an innovative approach with the CNN to rapidly estimate permeability in porous media under dynamic deformations, guided by FELBM coupling analysis. The fast and accurate performance of CNN underscores its promising potential for future applications.

Laser and Astrophysical Plasmas and Analogy between Similar Instabilities

Multipulse laser–matter interactions initiate nonlinear and nonequilibrium plasma fluid flow dynamics and their instability creating microscale vortex filaments, loop-soliton chains, and helically paired structures, similar to those at the astrophysical mega scale. We show that the equation with the Hasimoto structure describes both, the creation of loop solitons by torsion of vortex filaments and the creation of solitons by helical winding of magnetic field lines in the Crab Nebula. Our experiments demonstrate that the breakup of the loop solitons creates vortex rings with (i) quasistatic toroidal Kelvin waves and (ii) parametric oscillatory modes—i.e., with the hierarchical instability order. For the first time, we show that the same hierarchical instability at the micro- and the megascale establishes the conceptual frame for their unique classification based on the hierarchical order of Bessel functions. Present findings reveal that conditions created in the laser-target regions of a high filament density lead to their collective behavior and formation of helically paired and filament-braided “complexes”. We also show, for the first time, that morphological and topological characteristics of the filament-bundle “complexes” with the loop solitons indicate the analogy between similar laser-induced plasma instabilities and those of the Crab and Double-Helix Nebulas—thus enabling conceptualization of fundamental characteristics. These results reveal that the same rotating metric accommodates the complexity of the instabilities of helical filaments, vortex rings, and filament jets in the plasmatic micro- and megascale astrophysical objects.

Extraction of persistent lagrangian coherent structures for the pollutant transport prediction in the Bay of Bengal

AbstractLagrangian Coherent Structures (LCS) are the hidden fluid flow skeletons that provide meaningful information about the Lagrangian circulation. In this study, we computed the monthly climatological LCSs (cLCS) maps utilizing 24 years (1994–2017) of HYbrid Coordinate Ocean Model (HYCOM) currents and ECMWF re-analysis winds in the Bay of Bengal (BoB). The seasonal reversal of winds and associated reversal of currents makes the BoB dynamic. Therefore, we primarily aim to reveal the cLCSs associated with seasonal monsoon currents and mesoscale (eddies) processes over BoB. The simulated cLCS were augmented with the complex empirical orthogonal functions to confirm the dominant lagrangian transport pattern features better. The constructed cLCS patterns show a seasonal accumulation zone and the transport pattern of freshwater plumes along the coastal region of the BoB. We further validated with the satellite imagery of real-time oil spill dispersion and modelled oil spill trajectories that match well with the LCS patterns. In addition, the application of cLCSs to study the transport of hypothetical oil spills occurring at one of the active oil exploration sites (Krishna-Godavari basin) was described. Thus, demonstrated the accumulation zones in the BoB and confirmed that the persistent monthly cLCS maps are reasonably performing well for the trajectory prediction of pollutants such as oil spills. These maps will help to initiate mitigation measures in case of any occurrence of oil spills in the future.

New correlations to estimate the rough fracture permeability using computational fluid dynamics simulation

AbstractIn fractured reservoirs, the fracture network provides the main path for fluid flow. Appropriate estimation of the fracture permeability influences the precise prediction of the reservoir’s future performance. Commonly, for a known geometry of natural or induced fracture, the permeability is estimated by applying local cubic law. One major drawback of this approach is that the fracture surface roughness, which has a significant effect on fracture permeability, is not considered. Moreover, the knowledge about the impact of fracture surface roughness on fracture permeability is not currently sufficient. In this research, the fluid flow in fractures with rough-walled surfaces was studied using computational fluid dynamics. For this purpose, the fluid flow through fractures was simulated by applying appropriate roughness for fracture walls. Furthermore, two correlations, based on response surface methodology and power-law models, were proposed to predict fracture permeability as a function of four independent variables (surface roughness, fracture aperture, angle, and porosity). The results of the two presented correlations were validated, and the statistical analysis indicates that both models are appropriate to predict fracture permeability. The findings of this study will be of great assistance with understanding and characterization of the fluid flow in rough fractures and can be used in future works.

Fluid-Solid Interaction Analysis at the Slip Joint of a Boiling Water Reactor Type 5 Jet Pump

In this paper, the fluid-solid interaction of a jet pump of a boiling water reactor type 5 (BWR/5), with its riser subjected to a leakage flow through its slip joint, is reported. This is a fluid-elastic instability problem. A methodology is proposed for the evaluation of the velocity of the fluid at the slip joint with and without a labyrinth seal. It is calculated with computational fluid dynamics. The results show that such a seal reduces the velocity of the fluid and produces a stable and linear behavior between the inlet and the outlet fluid velocities at the slip joint. Then the first five natural frequencies of the jet pump assembly are evaluated. The range is between 24.74 Hz and 60.21 Hz. The mass of water inside and outside of such an assembly is considered. With these data and the dimensions of the slip joint, a finite element mesh is developed and the time step (∆t = 0.001 s) is determined. The fluid and structure mesh are coupled. The fluid flow through the slip joint without a labyrinth seal is evaluated with a two-way fluid-structure interaction under normal conditions of operation. Accelerations up to 8 g can be developed at the bottom of the mixer. The fluid flow is estimated during the first 0.25 s. Flow-induced vibration can be exacerbated in resonance conditions. These values are similar to those obtained in the experimental analyses reported in the open literature. One of the excitation frequencies caused by the interaction between the fluid and the structure was close to the third natural frequency of this assembly (46.99 Hz). If the integrity of the labyrinth seal is maintained, the jet pump will not present high-amplitude oscillations. Therefore, an adequate management of seal degradation is required and failures of the jet pump can be avoided.

Lab on a bead with oscillatory centrifugal microfluidics for fast and complete mixing enables fast and accurate biomedical assays.

Rapid mixing and precise timing are key for accurate biomedical assay measurement, particularly when the result is determined as the rate of a reaction: for example rapid immunoassay in which the amount of captured target is kinetically determined; determination of the concentration of an enzyme or enzyme substrate; or as the final stage in any procedure that involves a capture reagent when an enzyme reaction is used as the indicator. Rapid mixing and precise timing are however difficult to achieve in point-of-care devices designed for small sample volumes and fast time to result. By using centrifugal microfluidics and transposing the reaction surface from a chamber to a single mm-scale bead we demonstrate an elegant and easily manufacturable solution. Reagents (which may be, for example, an enzyme, enzyme substrate, antibody or antigen) are immobilised on the surface of a single small bead (typically 1-2mm in diameter) contained in a cylindrical reaction chamber subjected to periodically changing rotational accelerations which promote both mixing and uniform mass-transfer to the bead surface. The gradient of Euler force across the chamber resulting from rotational acceleration of the disc, dΩdisc/dt, drives circulation of fluid in the chamber. Oscillation of Euler force by oscillation of rotational acceleration with period, T, less than that of the hydrodynamic relaxation time of the fluid, folds the fluid streamlines. Movement of the bead in response to the fluid and the changing rotational acceleration provides a dynamically changing chamber shape, further folding and expanding the fluid. Bead rotation and translation driven by fluid flow and disc motion give uniformity of reaction over the surface. Critical parameters for mixing and reaction uniformity are the ratio of chamber radius to bead radius, rchamber/rbead, and the product Trchamber(dΩdisc/dt), of oscillation period and Euler force gradient across the fluid. We illustrate application of the concept using the reaction of horse radish peroxidase (HRP) immobilised on the bead surface with its substrate tetramethylbenzidine (TMB) in solution. Acceleration from rest to break a hydrophobic valve provided precise timing for TMB contact with the bead. Solution uniformity from reaction on the surface of the bead in volumes 20-50uL was obtained in times of 2.5s or less. Accurate measurement of the amount of surface-bound HRP by model fitting to the measured kinetics of colour development at 10 s intervals is demonstrated.

Direct Numerical Simulation of Mixed Convection Flow in Lid-Driven Cavities

The mixed convection of heat transfer and fluid flow in a - lid drivencubical cavity filled with air is investigated numerically in this study. The computational procedure is based on the finite volume method and a full multigrid acceleration solver. The top wall of the cavity is maintained at a constant high temperature - Th, and it can move with a constant velocity U0. The bottom wall is immobile and maintained at a cold temperature Tc. While, the remaining boundary parts of the cavity are motionless and kept thermally insulated. Several numerical simulations were conducted to investigate mixed convection heat transfer in a sliding cubical cavity for a range of Reynolds numbers from 1000 to 5000 and Richardson numbers from 0.001 to 10. The influence of mixed convection parameters, Reynolds number, Richardson number, and heat transfer rate on the flow behavior was analyzed through parametric studies. The results include flow and heat transfer characteristics, iso-surfaces, and streamlines for the entire range of Richardson numbers and Reynolds numbers investigated. The study shows that as Reynolds number is increased beyond a critical value, the flow becomes unstable and bifurcates.

Impacts of pancreatic exocrine insufficiency on gut microbiota.

Pancreatic exocrine insufficiency (PEI) can be induced by various kinds of diseases, including chronic pancreatitis, acute pancreatitis, and post-pancreatectomy. The main pathogenetic mechanism of PEI involves the decline of trypsin synthesis, disorder of pancreatic fluid flow, and imbalance of secretion feedback. Animal studies have shown that PEI could induce gut bacterial overgrowth and dysbiosis, with the abundance of Lactobacillus and Bifidobacterium increasing the most, which could be partially reversed by pancreatic enzyme replacement therapy. Clinical studies have also confirmed the association between PEI and the dysbiosis of gut microbiota. Pancreatic exocrine secretions and changes in duodenal pH as well as bile salt malabsorption brought about by PEI may affect and shape the abundance and composition of gut microbiota. In turn, the gut microbiota may impact the pancreatic exocrine acinus through potential bidirectional crosstalk. Going forward, more and higher-quality studies are needed that focus on the mechanism underlying the impact of PEI on the gut microbiota.

Improving Aeromechanical Performance of Compressor Rotor Blisk with Topology Optimization

When it comes to modern design of turbomachinery, one of the most critical objectives is to achieve higher efficiency and performance by reducing weight, fuel consumption, and noise emissions. This implies the need for reducing the mass and number of the components, by designing thinner, lighter, and more loaded blades. These choices may lead to mechanical issues caused by the fluid–structure interaction, such as flutter and forced response. Due to the periodic aerodynamic loading in rotating components, preventing or predicting resonances is essential to avoid or limit the dangerous vibration of the blades; thus, simulation methods are crucial to study such conditions during the machine design. The purpose of this paper is to assess a numerical approach based on a topology optimization method for the innovative design of a compressor rotor. A fluid-structural optimization process has been applied to a rotor blisk which belongs to a one-and-a-half-stage aeronautical compressor including static and dynamic loads coming from blade rotation and fluid flow interaction. The fluid forcing is computed by some CFD TRAF code, and it is processed via time and space discrete Fourier transform to extract the pressure fluctuation components in a cyclic-symmetry environment. Finally, a topological optimization of the disk is performed, and the encouraging results are presented and discussed. The remarkable mass reduction in the component (≈32%), the mode-shape frequency shift from a fluid forcing frequency, and an overall relevant reduction in the dynamic response around Campbell’s crossing confirm the efficacy of the presented methodology.

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.

Numerical analysis of inclined magnetic force impact on cross liquid flowing with widening shallow and heat generating

ABSTRACT The creation, utilisation, conversion, and exchange of thermal energy are all covered under the thermal engineering subject of heat transfer. Heat transfer plays a major role in engineering and industrial sectors like food packaging, food additive manufacturing, electronic cooling, microturbine, etc. Scientists across the world have tried to explore the impact of heat transfer on fluid past an expandable surface due to its exciting applications in industries like polymer production, paper production, crystal glass manufacturing, etc. This article has unique exploration, and it emphasises interpreting the Cross fluid flow along stretching surface with convective heat transport analysis by using the Lie group methodology. We investigated the implication of inclined upper-convected Maxwell fluid magnetohydrodynamic (MHD) movement through a penetrable strained plate. To solve nonlinear differential equations and clearly determine their absolute invariants, the Lie group approach is introduced. For the numerical solution of non-linear ordinary differential equations with boundary conditions, the fourth-order Runge–Kutta procedure with shelling performance is utilised. Plots showing the impacts of motivated and non-motivated MHD are researched and examined for the alterations of many parameters, and statistical graphs are given to explain the physical values. It is evident that opposing behaviour occurs in connection to temperature captivation and generation parameters together with motivated and non-motivated MHD. Under an amplified, heat-generating parameter and Deborah number, the rate of heat transmission increases. The Lie group investigation of Cross liquid in the presence/absence of inclined and non-inclined has not been investigated yet in the available literature.

Numerical solutions of thin film flows of non-Newtonian fluids via optimal homotopy asymptotic approach

The objective of this research is to recover new solutions in the lifting and drainage cases of thin film flows involving non-Newtonian fluid models namely Pseudo-Plastic (PP) and Oldroyd 6-Constant (O6C). Both of the considered fluids exhibit numerous uses in industry when coupled with thin film phenomena. Some of the industrial applications include decorative and optical coatings, prevention of metallic corrosion and lithography of various diodes, sensors and detectors. For solution purpose, a modified version of Optimal Homotopy Asymptotic Method (OHAM) is proposed in which Daftardar–Jafari polynomials will replace the classical OHAM polynomials in nonlinear problems and provide better results in terms of accuracy. The paper includes a comprehensive application of modified algorithm in the case of thin film phenomena. To validate the obtained series solutions, the paper employs a rigorous assessment of convergence and validity by computing the residual errors in each scenario. For showing the effectiveness of modified algorithm, numerical comparison of classical and modified OHAMs is also presented in this study. Furthermore, the study conducts an in-depth graphical analysis to assess the impact of fluid parameters on velocity profiles both in lifting and drainage scenarios. The results of this investigation demonstrate that the proposed modification of OHAM ensures better accuracy of solutions than the classical OHAM. Consequently, this method can be effectively utilized for tackling more advanced situations.

Influence of Dufour/Soret and Space-Dependent Internal Heat Source on Combined Convection of Non-Newtonian Fluids Flow Past a Vertical Full Cone in Porous Media: The VHF/VMF Case

Influence of Dufour/Soret and Space-Dependent Internal Heat Source on Combined Convection of Non-Newtonian Fluids Flow Past a Vertical Full Cone in Porous Media: The VHF/VMF Case

Effectiveness of injection protocols for hydraulic stimulation in enhanced geothermal systems

To harness the immense potential of geothermal energy for non-intermittent baseload power, low-permeability crystalline hot rocks need to be hydraulically stimulated to create Enhanced Geothermal Systems (EGS) that enable economically profitable fluid flow rates. However, hydraulic stimulation is usually associated with seismic activity that has led to project cancellation in a few occasions. To improve our understanding of the coupled hydro-mechanical (HM) processes behind stimulation during both injection and post-injection stages (after shut-in), we numerically analyze three different stimulation protocols: constant-rate, step-rate, and cyclic injection with and without bleed-off after shut-in (and between cycles for the cyclic protocol). Simulation results show that the injection protocol has a higher influence on the HM response of the fracture than the total volume of injected water, which challenge scaling laws that relate the injection volume with the expected maximum magnitude of the induced earthquakes. The trade-off between maximizing permeability enhancement, while minimizing induced seismicity is not straightforward. In particular, bleeding-off the well after injection restricts induced seismicity, but at the expenses of limiting permeability enhancement. When considering stimulation of a single fault, all protocols yield comparable slip rates and, thus, magnitude of the induced earthquake, with the constant-rate injection being the fastest to induce the largest earthquake. The small differences in the HM response to hydraulic stimulation do not permit identifying a protocol that performs better than the others.

Numerical Simulation of Cathode Nodule Local Effects

As one of the main factors decreasing current efficiency and product quality, the growth of nodules deserves attention in the copper electrorefining process. Three-dimensional (3D) Finite Element Method models combining tertiary current distribution and fluid flow were established in this study to investigate the details of the growth of columnar nodules, including the electrolyte flow around the nodule and its effects. Compared with an inert nodule, a significant impact of the electrochemical reaction of an active nodule has been observed on the fluid flow, which may be one of the reasons for the formation of small nodule clusters on the cathode. Furthermore, the local current density is not even on the nodule surface under the comprehensive influence of local electrolyte flow, local overvoltage, and the angle with the anode surface. Thus, the head of an active nodule grows faster than the root, and the upper parts grow faster than the lower parts, leading to asymmetric growth of the nodules.

Data-Driven Inline Leak Detection for Pipelines Using Flow-Induced Acoustics Analysis

Fluid and water distribution networks are essential to the modern world. However, these systems are prone to leaks, which can lead to significant water loss, damage to infrastructure, and environmental pollution. The proposed solution makes use of Acoustic Emission sensors placed in discrete locations in the pipeline which measures the sound in the pipeline caused by the flow of fluids. Computation models are used to deduce the location from the input provided by the sensors. In case of leak, the leak is localized through cross correlation and TDOA methods. This solution is particularly developed for water distribution pipelines. Keyword: Acoustic data analysis, Data-driven models, Cross-Correlation, Time Difference of Arrival (TDOA)

Omphacite breakdown: nucleation and deformation of clinopyroxene-plagioclase symplectites

The breakdown of omphacite plays an important role in the exhumation and retrogression of eclogites. Additionally, metamorphic reactions associated with grain size reduction have the potential to significantly impact deformation mechanisms and the rheology of crustal rocks. We analyze the breakdown reaction omphacite → diopsidic clinopyroxene + plagioclase ± amphibole and associated microstructures by electron backscatter diffraction. The reaction results in the formation of (diopsidic) clinopyroxene-plagioclase symplectites. Samples were chosen from localities on Holsnøy (western Norway) and Lofoten (northern Norway), that are representative of vermicular symplectites, partly recrystallized symplectites, and deformed symplectites. Interphase misorientation analysis based on the electron backscatter diffraction results reveals that the nucleation of (diopsidic) clinopyroxene-plagioclase symplectites was crystallographically controlled, with the diopside copying the lattice orientation of the omphacite, and the plagioclase growing along diopside planes with favorable, i.e., similar, interplanar spacing. Deformation of the (diopsidic) clinopyroxene-plagioclase symplectites occurred by fracturing, transitioning into grain boundary sliding accommodated by diffusion creep. The results indicate that the formation of vermicular symplectites is not associated with enhanced permeability and fluid flow. Subsequent recrystallisation and grain-size sensitive deformation of the symplectites facilitates fluid redistribution and weakening of the retrogressed eclogites.

Influence of Permeability and Shear-Thinning Behavior on the Hydrodynamics Flow Features Around Porous Square Cylinders

Abstract This article investigates the laminar flow of power-law fluids through two porous square cylinders in a side-by-side configuration. The effects of power-law index (n), Darcy number (Da), and gap ratio (g/W) are examined within ranges of g/W = 0.5–5, n = 0.4–0.8, and Da = 10−6–10−2, respectively. Two flow conditions are considered: first, for a creeping flow (unseparated flow) at Re = 1 where Darcy's law is applicable; second, for a viscous dominant flow at Re = 100, where Darcy–Forchheimer-extended model is exercised. Flow patterns behind the porous cylinders are analyzed using streamlines, velocity profiles, pressure distribution curves, and vorticity structural parameters (Г). In low permeability levels, the flow exhibits an irregular nonperiodic vortex shedding characterized by a single large vortex street far off the downstream for g/W = 0.5. However, synchronized wake patterns were observed in either antiphase or in-phase modes for higher gap ratios. Leading-edge separation with two-side recirculation induces quasi-periodicity in the flow for all g/W. It was found that increasing the permeability can prevent the leading edge separation. Additionally, a transition from antiphase to in-phase mode occurs when the permeability is altered while maintaining constant flow-time. The presence of a jet-like flow between cylinders significantly impacts unsteady wake patterns. The impact of g/W, power-law index, and permeability on drag is also examined. A jump in some flow parameters was observed at higher Re for the midrange Darcy number, but no such increase was noted for the high shear-thinning behavior. These findings provide a potential approach for improving the design of fluidic systems involving porous cylinders.

A Compressible Formulation of the One-Fluid Model for Two-Phase Flows

In this paper, we introduce a compressible formulation for dealing with 2D/3D compressible interfacial flows. It integrates a monolithic solver to achieve robust velocity–pressure coupling, ensuring precision and stability across diverse fluid flow conditions, including incompressible and compressible single-phase and two-phase flows. Validation of the model is conducted through various test scenarios, including Sod’s shock tube problem, isothermal viscous two-phase flows without capillary effects, and the impact of drops on viscous liquid films. The results highlight the ability of the scheme to handle compressible flow situations with capillary effects, which are important in computational fluid dynamics (CFD).

Hydrocarbon Transportation in Heterogeneous Shale Pores by Molecular Dynamic Simulation

Shale oil in China is widely distributed and has enormous resource potential. The pores of shale are at the nanoscale, and traditional research methods encounter difficulty in accurately describing the fluid flow mechanism, which has become a bottleneck restricting the industrial development of shale oil in China. To clarify the distribution and migration laws of fluid microstructure in shale nanopores, we constructed a heterogeneous inorganic composite shale model and explored the fluid behavior in different regions of heterogeneous surfaces. The results revealed the adsorption capacity for alkanes in the quartz region was stronger than that in the illite region. When the aperture was small, solid–liquid interactions dominated; as the aperture increased, the bulk fluid achieved a more uniform and higher flow rate. Under conditions of small aperture/low temperature/low pressure gradient, the quartz region maintained a negative slip boundary. Illite was more hydrophilic than quartz; when the water content was low, water molecules formed a “liquid film” on the illite surface, and the oil flux percentages in the illite and quartz regions were 87% and 99%, respectively. At 50% water content, the adsorbed water in the illite region reached saturation, the quartz region remained unsaturated, and the difference in the oil flux percentage of the two regions decreased. At 70% water content, the adsorbed water in the two regions reached a fully saturated state, and a layered structure of “water–two-phase region–water” was formed in the heterogeneous nanopore. This study is of great significance for understanding the occurrence characteristics and flow mechanism of shale oil within inorganic nanopores.