Fluid Flow Velocity Research Articles

Study on the Flow Characteristics of Non-Newtonian Drilling Fluid Through Vibrating Screen Meshes

Summary Composite screens are a critical component of drilling fluid shale shakers, and their performance directly affects the recovery efficiency of drilling fluid. This study focuses on the composite screens of shale shakers and simulates the flow of non-Newtonian drilling fluids through different structures of composite screens to investigate the impact of drilling fluid rheological parameters and screen compositions on screening performance. The research results indicate that the flow velocity of the drilling fluid is the highest while passing through the lower screen, and the turbulent kinetic energy (TKE) is at its maximum in the lower screen area, where energy dissipation is also the greatest. An increase in the rheological parameters of the four-parameter model drilling fluid generally increases the difficulty of passing through the screen, with the flow behavior index and viscosity coefficient having a particularly significant impact on the pressure drop coefficient. Compared with the plain composite screen, the herringbone composite screen and plain patterned composite screen have lower pressure drop coefficients, with the herringbone composite screen demonstrating the best screening performance. These findings provide theoretical references for flow analysis and structural optimization of shale shaker screens in drilling fluid applications.

Artificial gravity: an effective countermeasure for microgravity-induced headward fluid shift?

Long-duration spaceflight is associated with pathophysiological changes in the intracranial compartment hypothetically linked to microgravity-induced headward fluid shift. This study aimed to determine whether daily artificial gravity (AG) sessions can mitigate these effects, supporting its application as a countermeasure to spaceflight. Twenty-four healthy adult volunteers (16 men) were exposed to 60 days of 6° head-down tilt bed rest (HDTBR) as a ground-based analog of chronic headward fluid shift. Subjects were divided equally into three groups: no AG (control), daily 30-min intermittent AG (iAG), and daily 30-min continuous (cAG). Internal carotid artery (ICA) stroke volume (ICASV), ICA resistive index (ICARI), ICA flow rate (ICAFR), aqueductal cerebral spinal fluid flow velocity (CSFV), and intracranial volumetrics were quantified at 3 T. MRI was performed at baseline, 14 and 52 days into HDTBR, and 3 days after HDTBR (recovery). A mixed model approach was used with intervention and time as the fixed effect factors and the subject as the random effect factor. Compared with baseline, HDTBR was characterized by expansion of lateral ventricular, white matter, gray matter, and brain + total intracranial cerebral spinal fluid volumes, increased CSFv, decreased ICASV, and decreased ICAFR by 52 days into HBTBR (All Ps < 0.05). ICARI was only increased 14 days into HDTBR (P < 0.05). Neither iAG nor cAG significantly affected measurements compared with HDTBR alone, indicating that 30 min of daily exposure was insufficient to mitigate the intracranial effects of headward fluid shift. Greater AG session exposure time, gravitational force, or both are suggested for future countermeasure research.NEW & NOTEWORTHY Brief exposure to continuous or intermittent artificial gravity via short-arm centrifugation was insufficient in mitigating the intracranial pathophysiological effects of the headward fluid shift simulated during head-down tilt bed rest (HDTBR). Our results suggest that greater centrifugation session duration, gravitational force, or both may be required to prevent the development of spaceflight-associated neuro-ocular syndrome and should be considered in future ground-based countermeasure studies.

A novel model for low-permeability reservoir numerical simulation considering dynamic capillary force

ABSTRACT Capillary force is not only affected by water saturation but also affected by fluid flow velocity, which is necessary to modify the prior numerical simulation methods. First, a dynamic capillary force testing device was developed, then, an experimental procedure was adopted to measure the dynamic capillary force curve. Three dynamic capillary force curves were obtained under different displacement velocity conditions. Finally, the dynamic capillary force was introduced into the flow equation of low-permeability reservoir numerical simulation. The oil-phase equation and water-phase equation were discretized in three-dimensional space, and the IMPES method was used to solve the water saturation and pressure difference. The calculation results between the traditional numerical simulation method and the novel method under heterogeneous and inhomogeneous conditions were analyzed. The results reveal that the difference in water cut is mainly reflected in the rapid rise of water cut. In the early stage of rapid increase, the water cut calculated by the new method is slightly higher than traditional method. When the water cut is more than 65%, the water cut calculated by the new method is slightly lower than the traditional method.

Effect of different injection strategies considering intravenous injection on combination therapy of magnetic hyperthermia and thermosensitive liposomes

Abstract The combination therapy of magnetic hyperthermia and thermosensitive liposomes (TSL) is an emerging and effective cancer treatment method. The heat generation of magnetic nanoparticles (MNPs) due to an external alternating magnetic field can not only directly damage tumor cells, but also serves as a triggering factor for the release of doxorubicin from TSL. The aim of this study is to investigate the effects in the degree of tumor cell damage of two proposed injection strategies that consider intravenous administration. Since both MNPs and TSL enter the tumor region intravenously, this study establishes a biological geometric model based on an experiment-based vascular distribution. Furthermore, this study derives the flow velocity of interstitial fluid after coupling the pressure distribution inside blood vessels and the pressure distribution of interstitial fluid, which then provides the convective velocity for the calculation of subsequent nanoparticle concentration. Different injection strategies for the proposed approach are evaluated by drug delivery result, temperature distribution, and tumor cell damage. Simulation results demonstrate that the proposed delayed injection strategy after optimization can not only result in a wider distribution for MNPs and TSL due to the sufficient diffusion time, but also improves the distribution of the temperature and drug concentration fields for the overall efficacy of combination therapy.

Nonlinear vibrations and static bifurcation of a hyperelastic pipe conveying fluid

This study investigates the free and forced nonlinear vibrations, along with the static bifurcation behavior, of a fluid transmission hyperelastic pipe supported by clamped ends. Both geometrical and material nonlinearities are taken into account. The mathematical model is grounded in Euler–Bernoulli beam theory, incorporating von Kármán nonlinearity to capture the complexities of the system. For the hyperelastic materials, the strain energy function proposed by Yeoh is employed. Considering that the lowest critical velocity of the fluid flow is associated with the first mode, after deriving the governing equation using Hamilton’s principle, Galerkin discretization is applied to obtain the reduced order model in the first mode. Analysis of static bifurcation and stability is performed and critical velocity values of fluid flow are determined. The analysis of free and forced vibrations of the hyperelastic pipe is conducted using the method of multiple time scales, specifically focusing on the sub-critical velocity range of fluid flow, which corresponds to the unbuckled state of the pipe. This approach allows for a comprehensive examination of how fluid flow velocity influences the frequency characteristics of free vibrations, as well as the frequency response in the vicinity of the main resonance. The results obtained from this study can significantly enhance our understanding of the design and application of hyperelastic pipes in various fluid transfer scenarios. By elucidating the dynamic behavior and critical parameters associated with these pipes, the findings can inform engineering practices and contribute to the optimization of systems that utilize hyperelastic materials for fluid conveyance.

Analysis of hydrodynamics and thermal–hydraulic performance of twisted angle fins within an annular conduit

AbstractThis paper investigated the influence of various twisted angles of fin inserts integrated on the inner heated pipe wall of a double-pipe heat exchanger by analysing the thermal–hydraulic performance through numerical simulations. Results showed twisted angle fin (TAF) induced turbulent fluid flow phenomena, generating transverse and longitudinal vortices, along with swirling flow. This collaboration between the vortices and swirling flow effectively prevents heat trapping and enhances heat transfer from the inner pipe wall through the intensive fluid mixing. Despite longitudinal swirling vortices and turbulence significantly enhance local and global heat transfer performance, they led to increased pressure drop. However, TAF twisting reduces pressure drop by streamlining flow. The performance evaluation criterion (PEC) value is a dimensionless quantity that facilitates the comprehensive evaluation of optimal configurations by comparing the increment in Nusselt number and the increment in friction factor. PEC values greater than 1 indicate that the increase in Nusselt number exceeded the increase in friction factor. Among tested configurations, the twisted fin angles of 60° (TAF60) exhibited the highest improvement in Nusselt number and friction factor, also achieving the highest PEC of 1.59712 at Reynolds number of 1194.71. TAF40 and TAF50 were identified as optimal configurations for enhancing the thermal–hydraulic efficiency, with average PEC values of 1.26893 and 1.27030, respectively. Overall, the study indicated a consistent enhancement trend with increasing twisted angles and emphasizes the significant thermal performance improvement of TAF configurations compared to the smooth conduit. Furthermore, the results showed a converging tendency across all TAF configurations in the percentage improvement in Nusselt number and friction factor, as well as PEC compared to the baseline No fin configuration with increasing Reynolds number, suggesting that future improvements in thermal–hydraulic performance are more dependent on geometric angles than fluid flow velocity.

Development of the wave motion induced by near-bottom periodic disturbances in a two-layer shear current

The behavior of wave motion arising in an ideal incompressible homogeneous fluid under switching-on periodic bottom disturbances is studied in the linear approximation for the two-dimensional non-stationary problem. In the undisturbed state, the velocities of two-layer fluid flow are linear functions of the vertical coordinate in each of the layers with different gradients and coincide on the boundary of the layers. The upper boundary of fluid can be either free or bounded by the rigid cover. The dispersion dependences and the group velocities of the appearing wave modes are determined. The vertical displacements of the free surface and the interface between the layers are calculated. A comparison with the solution for a single-layer fluid is carried out.

Barrel rifling node offset detection and subsequent optimization based on thin film in-mold decoration characteristics of the Johnson–Cook model

In this paper, a nodal detection method for the detection and optimization of barrel helix offsets is proposed. The barrel used in this experiment is a 6-helix barrel. Moreover, the special properties of the film of Polyetheretherketone (PEEK) material are used to cover the surface of the barrel helix with a virtual in-mold decoration (IMD) film, and the unique nature of the film die offset in the IMD is utilized to detect the position of the barrel helix. The area with a large die index is the area with a large helix offset in the barrel, and the IMD die index is introduced to quantify the data. The IMD die index is used to determine the helix offset of the damaged barrel. The novelty of this work is that each node can use the die index to efficiently detect the position of the barrel helix deviation, carry out subsequent optimization and repair work through the optimization of the injection molding parameters and the design optimization of the barrel and verify the experiment by comparing the results. Through the steady-state simulation research mode, different permutations and combinations of the two process parameters are simulated to study their effects. Quantitative reference indicators include but are not limited to dependent variables such as the fluid flow velocity, shear rate, temperature distribution and phase transition, and the shear heating process of the injection screw is taken into account in the mold flow analysis to ensure that the die index value is more accurate. It can be seen from the analysis results that the temperature of the barrel changes after the groove depth and groove width are changed, and the effect ratio of the groove depth is lower than that of the groove width in the same degree of size change.

Testing the functionality of OLGA software for determining optimal oil transport modes to prevent solid particle deposition

Background: During operation, all mechanical impurities entering the collector through the flow lines settle at the bottom due to a decrease in flow velocity. This leads to a reduction in the capacity of the pipeline network, increased pressure, and premature equipment wear. To address this issue it is essential to understand the dynamics and intensity of sludge formation at the bottom of the pipeline. Aim: Evaluate the functionality and efficiency of the dynamic multiphase flow simulator in addressing challenges related to the transport of borehole fluid containing solid particles. Materials and methods: To build a mathematical simulation of multiphase flow with solid particles using OLGA specialised software, we selected one of the oil gathering lines in field N, with a diameter of 159х10 mm and a length of 1600 m, as the study object. This oil gathering line collects production from 16 wells. The OLGA simulator was used to model the process and measure flow parameters with different particle diameters, predicting the dynamics of variables such as time-varying flow velocities, fluid composition, temperatures, and particulate deposition. For a flow with a particle diameter of 104 µm, active precipitation occurs at flow rates between 200 and 300 m³/day. At flow rates of 400 m³/day and above, the velocity is sufficient to carry the particles without significant accumulation in the pipeline. Results: The software enabled the calculation of the dynamic system for different solid particle diameters in multiphase flow, addressing the challenge of evaluating the dynamics of solid phase accumulation in the pipeline and determining the fluid flow velocity required to prevent sludge formation. The software is suitable for implementing simulation modelling to develop technical solutions that minimise the risks of solid particle deposition in oil gathering pipelines during the operation of on-shore infrastructure facilities. Conclusion: The software enabled the calculation of the dynamic system for different solid particle diameters in multiphase flow, addressing the challenge of evaluating the dynamics of solid phase accumulation in the pipeline and determining the fluid flow velocity required to prevent sludge formation. The software is suitable for implementing simulation modelling to develop technical solutions that minimise the risks of solid particle deposition in oil gathering pipelines during the operation of on-shore infrastructure facilities.

Solidification behavior of WC particles reinforced nickel alloy cladding layers by plasma surfacing: Simulation and experiment

In this work, a numerical simulation model was developed to investigate the complex heat and mass transfer process inside the molten pool during plasma surfacing. The temperature distribution and fluid flow were employed to depict the evolution of the molten pool. The findings revealed that the maximum temperature is located on the surface of the cladding layer corresponding to the position of heat source, and the temperature distribution follows a Gaussian distribution along the scanning direction. Thermal accumulation is obvious due to the continuous energy input in the initial stage, as a result, the maximum temperature and fluid flow velocity gradually increase with the deposition process. The maximum temperature and fluid flow velocity at 4.0 s are 1893 K and 0.281 m/s in case 110 A, respectively. The predicted shapes and dimensions are consistent with the results of the deposition experiments, with a maximum error of no more than 15 %. In order to investigate the impact of WC particles on the solidification microstructure of nickel composite layers, corresponding plasma surfacing experiment was implemented. The solidification characteristics of the microstructure follow planar-cellular-columnar-equiaxed crystals in the bonding layer and WC particles-columnar-equiaxed dendritic crystals in hard layer, respectively. Furthermore, the Ni dendritic near the retained WC particles transformed into columnar crystals due to temperature gradient in the local area.

Numerical Simulation of Fixed-Free End Beam’s Modal Behaviour using Two-Way Coupled Fluid-Structure Interaction Approach

The fluid flow velocity stands as a pivotal parameter with a great influence on the mutual interaction between the fluid domain and structure. This paper focuses on structural deformation, structural velocity, von-Mises stress and frequency response of a fixed-free end beam using two-way coupled fluid-structure interaction within ANSYS Workbench. The parameters such as deformed fluid pressure and velocity were analysed across three diverse flow regimes: laminar, transitional and turbulent – each aligned with distinct fluid velocities. The outcomes show that the total deformation, velocity and von-Mises stress distribution of the fixed-free end beam increase as the inlet fluid velocity increases. As a result, the pressure and velocity distribution in the fluid flow which receiving the resultant or leftover structure deflection also increases as the incoming fluid velocity increases. Furthermore, the analysis probes the frequency response in turbulent flow conditions reveals higher values compared to laminar and transitional flows, albeit within the same natural frequency domain. This observation marks significant vibrational characteristics found in the presence of turbulent flow dynamics.

Shear-induced fluid localization, episodic fluid release and porosity wave in deformable low-permeability rock salt

Understanding fluid distribution and migration in deformable low-permeability rock salt is critical for geologic disposal of nuclear waste. Field observations indicate that fluids in a salt formation are likely compartmentalized into relatively isolated patches and fluid release from such a formation is generally episodic. The underlying mechanism for these phenomena remains poorly understood. In this paper, a hydrological-mechanical model is formulated for fluid percolation in a rock salt formation under a deviatoric stress. Using a linear stability analysis, we show that a porosity wave (a train of alternating high and low porosity pockets) can emerge from positive feedbacks among intergranular wetting, grain boundary weakening and shear-induced material dilatancy. Fluid localization or episodic release can be viewed as a stationary or propagating porosity wave respectively. Fluid pockets transported via a porosity wave remain relatively isolated with minimal mixing between neighboring pockets. We further show that the velocity of fluid flow can be significantly enhanced by the emergence of a porosity wave. The concept and the related model presented in this paper provide a unified consistent explanation for the key features observed in fluid flow in rock salt. The similar process is expected to occur in other deformable low-permeability media such as shale and partially molten rocks under a deviatoric stress. Thus, the result presented here has an important implication to hydrocarbon expulsion from shale source rocks, radioactive waste isolation in a tight rock repository, and caprock integrity of a subsurface gas (CO2, H2 or CH4) storage system. It may also help develop a new engineering approach to fluid injection into or extraction from unconventional reservoirs.

Numerical Study of High-g Combustion Characteristics in a Channel with Backward-Facing Steps

High gravity (high-g) combustion can significantly increase flame propagation speed, thereby potentially shortening the axial length of aero-engines and increasing their thrust-to-weight ratio. In this study, we utilized the large eddy simulation model to investigate the combustion characteristics and flame morphology evolution of premixed propane–air flames in a channel with a backward-facing step. The study reveals that both the increase in centrifugal force and flow velocity can enhance pressure fluctuations during combustion and increase the turbulence intensity. The presence of centrifugal force promotes the occurrence of Rayleigh–Taylor instability (RTI) between hot and cold fluids. The combined effects of RTI and Kelvin–Helmholtz instability (KHI) enhance the disturbance between hot and cold fluids, shorten the fuel combustion time, and intensify the dissipation of large-scale vortices. The increase in fluid flow velocity can raise the flame front’s hydrodynamic stretch rate, thereby enhancing the turbulence level during combustion to a certain extent and increasing the fuel consumption rate. When a strong centrifugal force is applied, the global flame propagation speed can be more than doubled. Within a certain range, the increase in high-g field strength can enhance the intensity of RTI and accelerate the transition of RTI to the nonlinear stage.

Numerical Study on the Impact of the Richardson Number on Convection in an Enclosure, with Moving Sidewalls for Three Aspect Ratios: A = 1, 2 and 0.5

Using mathematical models, this research investigation seeks to explore how varying aspect ratios and the Richardson number impact the mixing effectiveness, fluid flow velocity, and heat transfer characteristics in a rectangle-shaped space where cooling occurs along the sides and warm with a steady temperature exists throughout the 80% of the bottom section's center. Discretizing the governing equations through the finite volume approach, we solved them iteratively using the Tri-diagonal Matrix Algorithm, where pressure-velocity coupling was successfully implemented via the SIMPLER procedure. Innovative approaches for convection and diffusion terms involved employing a power-law difference scheme alongside a central differential scheme. In various simulations with specified parameters (Re = 100, Pr = 0.71), we visualized results in forms like streamlines, isothermal lines, and temperature/velocity profiles, along with local and average Nusselt numbers. We observe five unique structure formations during flow behavior by analyzing how Richardson numbers impact heat transmission within a specific geometric configuration (enclosure size A = 1). A change in aspect ratio leads to improved control over fluid movement while minimizing structural distortion. A subtle rise in heat transmission emerged as the average Nusselt number and Richardson number intersection strengthened force convection's domination while experiencing significant escalation under conditions conductive to natural convection. Decreasing the aspect ratio increased heat transfer efficiency when the Richardson number rose.

Continuous Focusing of Particles by AC-Electroosmosis and Induced Dipole Interactions.

Continuous particle focusing by using microfluidics is an effective method for separating particles, cells, or droplets for analytical purposes. Previously, it was shown that an alternating current across rectangular microchannels with slightly deformed side walls results in vortex flow patterns caused by alternating current electroosmosis (AC-EOF) and could lead to particle focusing. In this work, we explore this mechanism by experimentally studying the particle focusing behavior for various fluid flow velocities through a microchannel. Since it is unlikely that the particles are kept in their focused position solely by convection, a theoretical force balance between the hydrodynamic and the induced dipole force was determined. In our experiments, it was found that there is no substantial effect of the pressure-driven fluid velocity on the particle focusing velocity within the studied range. From the theoretical force balance calculations, it was determined that while the addition of the induced dipole force can still not completely describe the experimentally observed particle focusing, the induced dipole can be strong enough to overcome the hydrodynamic force. Finally, it is hypothesized that under specific circumstances, including a repulsive electrostatic force between a particle and electrode wall can complete the theoretical particle focusing force balance. Alternative phenomena that could also play a role in particle focusing are proposed.

Erosion of surfaces by trapped vortices

Two two-dimensional free boundary problems describing the erosion of solid surfaces by the flow of inviscid fluid in the presence of trapped vortices are considered. The first problem tackles an initially flat, infinite fluid-solid interface with uniform flow at infinity and a vortex in equilibrium above the surface. The second involves flow around a finite body with a trailing Föppl-type vortex pair. The conformal invariance of the complex potential permits both problems to be formulated as a Polubarinova–Galin (PG) type equation in which the time-dependent eroding surface in the physical z-plane is mapped to the fixed boundary of the ζ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\zeta $$\\end{document}-disk. The Hamiltonian governing the equilibrium position of the vortex (or vortex pair in the second problem) is also found from the same map. In each problem, the PG equation giving the conformal map is found numerically and the time-dependent evolution of the interface and vortex location is determined. Different models governing the erosion of the interface are investigated in which the normal velocity of the boundary depends on some given function of the fluid flow velocity at the boundary. Typically, in the infinite surface case, erosion leads to the formation of a symmetric valley beneath the vortex which, in turn, moves downward toward the interface. A finite body undergoes erosion which is asymmetric in the flow direction leading to a flattening of the lee surface of the body so displaying some similarity to the experiments and associated viscous theory of Ristroph et al, Moore et al (Proc Natl Acad Sci 109(48):19606–19609, 2012, Phys Fluids 25(11):116602, 2013).

Deriving Flow Velocity and Initial Concentration From Liesegang‐Like Patterns

AbstractZebra rocks, characterized by their striking reddish‐brown stripes, rods, and spots of hematite (Fe‐oxide), showcase complex self‐organized patterns formed under far‐from‐equilibrium conditions. Despite their ease of recognition, the underlying mechanisms of pattern‐forming processes remain elusive. We introduce a novel advection‐dominated phase‐field model that effectively replicates the Liesegang‐like patterns observed in Zebra rocks. This numerical model leverages the concept of phase separation, a well‐established principle governing Liesegang phenomena in a two‐dimensional setting. Our findings reveal that initial solute concentration and fluid flow velocity are critical determinants in pattern morphologies. We quantitatively explain the spacing and width of a specific Liesegang‐like pattern category. Furthermore, the model demonstrates that vanishingly low initial concentrations promote the formation of oblique patterns, with inclination angles influenced by rock heterogeneity. Additionally, we establish a quantitative relationship between band thickness and geological parameters for orthogonal bands. This enables the characterization of critical geological parameters based solely on static patterns observed in Zebra rocks, providing valuable insights into their formation environments. The diverse patterns in Zebra rocks share similarities with morphologies observed on early Earth and Mars, such as banded iron formations and hematite spherules. Our model, therefore, offers a plausible explanation for the formation mechanisms of these patterns and presents a powerful tool for deciphering the geochemical environments of their origin.

Увеличение продолжительности работы установки электроцентробежного насоса для повышения безопасности и сокращения рисков при спускоподъемных операциях

The study analyzes basic complications associated with generating mechanical impurities; numeric modeling to optimize the electrical submersible pump operation has been performed. Modeling the fluid flow in combination with erosion models has been used to determine the key factors facilitating the erosion of the electrical submersible pump action wheel impeller during oil production. In order to obtain a complete view of the flow and erosion properties, modeling has been performed for the entire fluid flow route. Modeling of the flow and the action wheel component erosion has been performed to determine the impact of the flow imbalance as well as to ensure the boundary conditions at the input for the modeling. The modeling results have shown: the rotational flow introduced in the mixing point at the action wheel input significantly impacts the strength properties of the modeled object; the area most exposed to erosion is the area of the action wheel impeller. The values of loss of material have been determined via the time sequence of geometry changes in the compounds in combination with the actual hydraulic operational parameters. The flow trajectories proposed for modeling show that the recirculating flow is the dominant. It is widely adopted that recirculation is one of the main causes of increased erosion in the compounds of the electrical submersible pump as it leads to the high frequency of high-speed impacts by sand particles. In order to reduce the erosion risk, the analysis aiming to identify the impeller geometrical parameters has revealed that the erosion rate in the compound can be reduced by decreasing the inclination of the action wheel impeller. The study has demonstrated that numerical modeling can provide a detailed and precise evaluation of erosion potential in cases associated with the high velocity of fluid flow with particles of mechanical impurities.

Prediction model of maximum stress for concrete pipes based on XGBoost-PSO algorithm

Due to varying burial conditions and service environments, concrete pipes exhibit complex mechanical behavior. Existing theoretical, simulation, and test methods for determining the maximum stress of pipes have significant limitations, including excessive assumptions, low efficiency, and restricted applicable conditions. Therefore, there is an urgent need to propose a multi-factor associated method for pipe stress prediction. This paper proposed an innovative approach to finely simulate the mechanics response for concrete pipes under the coupling action of stress-seepage-fluid fields. The accuracy of this numerical simulation method was validated through full-scale test. Sensitivity analysis based on Morris sensitivity analysis theory was conducted on traffic load magnitude and speed, buried depth, groundwater table, fluid height and velocity, bedding strength, backfill strength, and pipe diameter. A dataset of “physical variables - maximum stress” for concrete pipes was established. A multi-factor-correlated prediction model of maximum stress for concrete pipe was proposed using XGBoost machine learning method optimized by Particle Swarm Optimization (PSO) algorithm. The results indicate that pipe diameter is highly sensitive; buried depth and traffic load magnitude are sensitive; groundwater table, bedding strength, and backfill strength are moderately sensitive; while fluid height, traffic speed, and flow velocity are insensitive. The XGBoost-PSO model demonstrates the highest accuracy and lowest error compared to BP, RF, and XGBoost models, with improvements in prediction accuracy of 59.6 %, 23.8 %, and 8.6 %, respectively. The model achieves RMSE of 0.118 and MAE of 0.213, demonstrating the suitability of the XGBoost-PSO model for predicting maximum stress for concrete pipes.

A novel compartmental approach for modeling stomach motility and gastric emptying

The stomach, a central organ in the Gastrointestinal (GI) tract, regulates the processing of ingested food through gastric motility and emptying. Understanding the stomach function is crucial for treating gastric disorders. Experimental studies in this field often face difficulties due to limitations and invasiveness of available techniques and ethical concerns. To counter this, researchers resort to computational and numerical methods. However, existing computational studies often isolate one aspect of the stomach function while neglecting the rest and employ computationally expensive methods. This paper proposes a novel cost-efficient multi-compartmental model, offering a comprehensive insight into gastric function at an organ level, thus presenting a promising alternative.The proposed approach divides the spatial geometry of the stomach into four compartments: Proximal/Middle/Terminal antrum and Pyloric sphincter. Each compartment is characterized by a set of ordinary differential equations (ODEs) with respect to time to characterize the stomach function. Electrophysiology is represented by simplified equations reflecting the “slow wave behavior” of Interstitial Cells of Cajal (ICC) and Smooth Muscle Cells (SMC) in the stomach wall. An electro-mechanical coupling model translates SMC “slow waves” into smooth muscle contractions. Muscle contractions induce peristalsis, affecting gastric fluid flow velocity and subsequent emptying when the pyloric sphincter is open. Contraction of the pyloric sphincter initiates a retrograde flow jet at the terminal antrum, modeled by a circular liquid jet flow equation.The results from the proposed model for a healthy human stomach were compared with experimental and computational studies on electrophysiology, muscle tissue mechanics, and fluid behavior during gastric emptying. These findings revealed that each “ICC” slow wave corresponded to a muscle contraction due to electro-mechanical coupling behavior. The rate of gastric emptying and mixing efficiency decreased with increasing viscosity of gastric liquid but remained relatively unchanged with gastric liquid density variations. Utilizing different ODE solvers in MATLAB, the model was solved, with ode15s demonstrating the fastest computation time, simulating 180 s of real-time stomach response in just 2.7 s. This multi-compartmental model signifies a promising advancement in understanding gastric function, providing a cost-effective and comprehensive approach to study complex interactions within the stomach and test innovative therapies like neuromodulation for treating gastric disorders.