Search Results (450)

During perforation operations, high-speed jet penetration into the casing-cement sheath-formation assembly damages the bonding interfaces, resulting in fluid flow along these interfaces within the wellbore. This can compromise the wellbore seal integrity and shorten the lifespan of the oil and gas well. To address this, a numerical model was developed using fluid-solid coupling algorithms, combined with a cohesive zone damage model and the ALE algorithm. The model was employed to analyze the dynamic damage evolution of the bonding interfaces during the jet penetration process and quantify the effects of the cement sheath’s mechanical parameters (shear modulus and compressive strength) and geological stress on the axial damage length and area. The results indicate that both the casing-cement sheath and cement sheath-formation interfaces exhibit significant damage, with the former showing a larger damage area under identical mechanical conditions; as the cement sheath’s shear modulus increases, the damaged area at the casing-cement sheath interface expands, while that at the cement sheath-formation interface reduces. Conversely, an increase in the cement sheath’s compressive strength reduces the damage extent at both interfaces, as does elevated geological stress. Based on engineering cases, different cement slurry types were compared to minimize perforation-induced interface damage. This study provides theoretical and practical guidance for optimizing cement selection and assessing bonding interface integrity during perforation. Full article

This study investigates the flow field and temperature field characteristics of a certain type of aerospace tail-thrust clutch friction plate under engagement conditions. A thermo–fluid–solid coupled convective heat transfer model was established based on the velocity distribution of lubricating oil within the groove cavities. The model was applied to analyze the surface temperature distribution of a single friction pair (friction plate and steel plate) under different operating parameters. The results reveal that both the inlet temperature and flow rate of the lubricating oil have a mitigating effect on temperature rise. However, due to the geometric constraints of the groove structure, the maximum wetted area and the actual inflow are inherently limited. Consequently, the temperature evolution during engagement is more significantly influenced by rotational speed and applied pressure. In particular, once these parameters exceed certain critical values, the surface temperature exhibits a sharp increase. Furthermore, the optimization of lubricating flow is constrained by friction materials. A higher flow rate does not necessarily yield greater lubrication benefits; instead, the optimal flow rate solution tailored to the friction pair should be pursued. This work provides theoretical insights into parameter control for aerospace tail-thrust clutches in practical operation. Full article

Modeling the pre-extraction of coalbed methane presents a significant mathematical challenge due to the complex interplay of multiple physical fields. This paper presents a robust mathematical model based on a thermo-hydro-mechanical damage (THMD) framework to describe this process. The model is formulated as a system of coupled, non-linear partial differential equations (PDEs) that integrate governing equations for heat transfer, fluid seepage, and solid mechanics with a damage evolution law derived from continuum damage mechanics. A key contribution of this work is the integration of this multi-physics model, solved numerically using the Finite Element Method (FEM), with a statistical modeling approach using Response Surface Methodology (RSM) and Analysis of Variance (ANOVA). This integrated framework allows for a systematic analysis of the model’s parameter space and a rigorous quantification of sensitivities. The ANOVA results reveal that the model’s damage output is most sensitive to the borehole diameter (F = 2531.51), while the effective extraction radius is predominantly governed by the initial permeability (F = 4219.59). This work demonstrates the power of combining a PDE-based multi-physics model with statistical metamodeling to provide deep, quantitative insights for optimizing gas extraction strategies in deep, low-permeability coal seams. Full article

With the increasing global demand for energy, the development of unconventional resources has become a focal point of research. Among these, shale gas has drawn considerable attention due to its abundant reserves. However, its low permeability and complex fracture networks present substantial challenges. This study investigates the composite fracturing technology combining supercritical CO₂ and slickwater for shale gas extraction, elucidating the mechanisms by which it influences shale fracture roughness and conductivity through an integrated approach of theory, experiments, and numerical modeling. Experimental results demonstrate that the surface roughness of shale fractures increases markedly after supercritical CO₂–slickwater treatment. Moreover, the dynamic evolution of permeability and porosity is governed by roughness strain, adsorption expansion, and corrosion compression strain. Based on fluid–solid coupling theory, a mathematical model was developed and validated via numerical simulations. Sensitivity analysis reveals that fracture density and permeability have a pronounced impact on shale gas field productivity, whereas fracture dip angle exerts a comparatively minor effect. The findings provide a theoretical basis for optimizing composite fracturing technology, thereby enhancing shale gas extraction efficiency and promoting effective resource utilization. Full article

Asteroids are remnants of primordial material from the early stages of solar system formation, approximately 4.6 billion years ago, and they preserve invaluable records of the processes underlying planetary evolution. Investigating asteroids provides critical insights into the mechanisms of planetary development and the potential origins of life. To enable efficient sample acquisition under vacuum and microgravity conditions, this study introduces a two-stage gas-driven asteroid sampling strategy. This approach mitigates the challenges posed by low-gravity environments and irregular asteroid topography. A coupled computational fluid dynamics–discrete element method (CFD–DEM) framework was employed to simulate the gas–solid two-phase flow during the sampling process. First, a model of the first-stage gas-driven sampling device was developed to establish the relationship between the inlet angle of the gas nozzle and the sampling efficiency, leading to the optimization of the nozzle’s structural parameters. Subsequently, a model of the integrated two-stage gas-driven sampling and sample-delivery system was constructed, through which the influence of the second-stage nozzle inlet angle on the total collected sample mass was investigated, and its design parameters were further refined. Simulation outcomes were validated against experimental data, confirming the reliability of the CFD–DEM coupling approach for predicting gas–solid two-phase interactions. The results demonstrate the feasibility of collecting asteroid regolith with the proposed two-stage gas-driven sampling and delivery system, thereby providing a practical pathway for extraterrestrial material acquisition. Full article

This study investigates premature fatigue failure in rocker arm gears of large-mining-height shearers operating at alternating ±45° working angles, where insufficient lubrication generates non-uniform thermal -stress fields. In this study, an integrated multiphysics framework combining transient thermal–fluid–structure coupling simulations with fatigue life prediction is proposed. Transient thermo-mechanical coupling analysis simulated dry friction conditions, capturing temperature and stress fields under varying speeds. Fluid–thermal–solid coupling analysis modeled wet lubrication scenarios, incorporating multiphase flow to track oil distribution, and calculated convective heat transfer coefficients at different immersion depths (25%, 50%, 75%). These coupled simulations provided the critical time-varying temperature and thermal stress distributions acting on the gears (Z6 and Z7). Subsequently, these simulated thermo-mechanical loads were directly imported into ANSYS 2024R1 nCode DesignLife to perform fatigue life prediction. Simulations demonstrate that dry friction induces extreme operating conditions, with Z6 gear temperatures reaching over 800 °C and thermal stresses peaking at 803.86 MPa under 900 rpm, both escalating linearly with rotational speed. Lubrication depth critically regulates heat dissipation, where 50% oil immersion optimizes convective heat transfer at 8880 W/m²·K for Z6 and 11,300 W/m²·K for Z7, while 25% immersion exacerbates thermal gradients. Fatigue life exhibits an inverse relationship with speed but improves significantly with cooling. Z6 sustains a lower lifespan, exemplified by 25+ days at 900 rpm without cooling versus 50+ days for Z7, attributable to higher stress concentrations. Based on the multiphysics analysis results, two physics-informed engineering optimizations are proposed to reduce thermal stress and extend gear fatigue life: a staged cooling system using spiral copper tubes and an intelligent lubrication strategy with gear-pump-driven dynamic oil supply and thermal feedback control. These strategies collectively enhance gear longevity, validated via multiphysics-driven topology optimization. Full article

The erosion mechanism of hydrocyclones under air column conditions is still unclear. In this paper, Computational Fluid Dynamics–Discrete Phase Model (CFD-DPM) technology is adopted to perform transient simulations of the three-phase flow (liquid–gas–solid) within a hydrocyclone. The Reynolds Stress Model (RSM) and Volume of Fluid (VOF) model are adopted to simulate the continuous phase flow field within the hydrocyclone, while the DPM coupled with the Oka erosion model is used to predict the particle flow and erosion mechanisms on each wall within the hydrocyclone. The particle sizes considered are 15 μm, 30 μm, 60 μm, 100 μm, 150 μm, and 200 μm, respectively, with a density of 2600 kg/m³. The particle velocity is consistent with the fluid velocity at 5 m/s, the total mass flow rate is 6 g/s, and the volume fraction is less than 10%. The results indicate that the cone section suffers the severest erosion, followed by the overflow pipe, column section, infeed section, and roof section. The erosion in the cone section reaches its maximum value near the underflow port, with an erosion rate approximately 6.8 times that of the upper cone section. The erosion distribution in the overflow pipe is uneven. The erosion of the column section exhibits a spiral banded distribution with a relatively large pitch. The erosion rate in the infeed section is approximately 1.47 times that of the roof section. Full article

High-frequency vibrations in annular gap type pressure-regulating valves of wind tunnels can induce fatigue, fracture, and operational failures, posing challenges to safe and reliable operation. This study proposes a hybrid leakage fault diagnosis framework that integrates wavelet packet-based signal analysis with advanced deep learning techniques. Time-domain acceleration signals collected from multiple sensors are processed to extract maximum component energy and its variation rate, identified as sensitive and robust indicators for leakage detection. A fluid–solid coupled finite element model of the valve system further validates the reliability of these indicators under different operational scenarios. Based on this foundation, a Vision Transformer (ViT)-based model is trained on a dedicated database encompassing multiple leakage conditions and sensor arrangements. Comparative evaluation demonstrates that the ViT model outperforms conventional deep learning architectures in terms of accuracy, stability, and predictive reliability. The integrated framework enables fast, automated, and robust leakage diagnosis, providing a comprehensive solution to enhance the monitoring, maintenance, and operational safety of wind tunnel valve systems. Full article

This study, motivated by the pronounced fluid loss characteristics of water-based fracturing fluids, developed a fluid–solid coupling model to investigate water-based fracturing in geological reservoirs. The model was further employed to analyse the effects of multiple factors on fracture propagation and the seepage capacity of water-based fracturing fluids. Moreover, the underlying mechanisms of fracture propagation and seepage enhancement were elucidated from a microscopic molecular perspective. The results obtained that the high apparent viscosity of water-based fracturing fluids not only enhances the fracturing efficiency of reservoir rocks but also results in a reduced seepage volume (−17 mL) in low-permeability reservoirs. Furthermore, the reservoir porosity (+2.5%) exhibits a clear inverse proportional relationship with fracturing efficiency (−0.9 m), while the seepage volume (+7 mL) of water-based fracturing fluids continues to increase. The strength and quantity of hydrogen bonds between molecules in water-based fracturing fluid, influenced by external factors, directly affect fluid seepage. The seepage behaviour of water-based fracturing fluids in geological reservoirs, together with the influence of reservoir conditions on fracture propagation, provides valuable reference data for rock fracturing and reservoir stimulation. However, the absence of data analysis and microscopic images of microscopic molecular dynamics constitutes a challenging problem that demands attention. Full article

This study evaluates the impact of mineralogy, elemental composition, and reaction pathways on hydrogen (H₂) generation in seven ultramafic and mafic (basaltic) rocks. Experiments were conducted under typical low-temperature hydrothermal conditions (150 °C) and captured early and evolving stages of fluid–rock interaction. Pre- and post-interactions, the solid phase was analyzed using X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS), while Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to determine the composition of the aqueous fluids. Results show that not all geologic H₂-generating reactions involving ultramafic and mafic rocks result in the formation of serpentine, brucite, or magnetite. Our observations suggest that while mineral transformation is significant and may be the predominant mechanism, there is also the contribution of surface-mediated electron transfer and redox cycling processes. The outcome suggests continuous H₂ production beyond mineral phase changes, indicating active reaction pathways. Particularly, in addition to transition metal sites, some ultramafic rock minerals may promote redox reactions, thereby facilitating ongoing H₂ production beyond their direct hydration. Fluid–rock interactions also regenerate reactive surfaces, such as clinochlore, zeolite, and augite, enabling sustained H₂ production, even without serpentine formation. Variation in reaction rates depends on mineralogy and reaction kinetics rather than being solely controlled by Fe oxidation states. These findings suggest that ultramafic and mafic rocks may serve as dynamic, self-sustaining systems for generating H₂. The potential involvement of transition metal sites (e.g., Ni, Mo, Mn, Cr, Cu) within the rock matrix may accelerate H₂ production, requiring further investigation. This perspective shifts the focus from serpentine formation as the primary driver of H₂ production to a more complex mechanism where mineral surfaces play a significant role. Understanding these processes will be valuable for refining experimental approaches, improving kinetic models of H₂ generation, and informing the site selection and design of engineered H₂ generation systems in ultramafic and mafic formations. Full article

Wellbore stability is a crucial factor affecting the safe exploitation of offshore natural gas hydrates. As a sustainable energy source, natural gas hydrate has significant reserves, high energy density, and low environmental impact, making it an important candidate for alternative energy. Although research on the stability of screen pipes during horizontal-well hydrate production is currently limited, its importance in sustainable energy extraction is growing. This study therefore considers the effects of hydrate phase change, gas–water seepage, energy and mass exchange, reservoir deformation, and screen pipe influence and develops a coupled thermal–fluid–solid–chemical field model for horizontal-well natural gas hydrate production. The model results were validated using experimental data and standard test cases from the literature. The results obtained by applying this model in COMSOL Multiphysics 6.1 showed that the errors in all simulations were less than 2%, with errors of 12% and 6% observed at effective stresses of 0.5 MPa and 3 MPa, respectively. The simulation results indicate that the presence of the screen pipe in the hydrate reservoir exerts little effect on the decomposition of gas hydrates, but it effectively mitigates stress concentration in the near-wellbore region, redistributing the effective stress and significantly reducing the instability risk of the hydrate reservoir. Furthermore, the distribution of mechanical parameters around the screen pipe is uneven, with maximum values of equivalent Mises stress, volumetric strain, and displacement generally occurring on the inner side of the screen pipe in the horizontal crustal stress direction, making plastic instability most likely to occur in this area. With other basic parameters held constant, the maximum equivalent Mises stress and the instability area within the screen increase with the rise in the production pressure drop and wellbore size, and the decrease in screen pipe thickness. The results of this study lay the foundation for wellbore instability control in the production of offshore natural gas hydrates via depressurization. The study provides new insights into sustainable energy extraction, as improving wellbore stability during the extraction process can enhance resource utilization, reduce environmental impact, and promote sustainable development in energy exploitation. Full article

Drilling fluid loss is a common and complex downhole problem that occurs during drilling in deep fractured formations, which has a significant negative impact on the exploration and development of oil and gas resources. Establishing a drilling fluid loss model for the quantitative analysis of drilling fluid loss is the most effective method for the diagnosis of drilling fluid loss, which provides a favorable basis for the formulation of drilling fluid loss control measures, including the information on thief zone location, loss type, and the size of loss channels. The previous loss model assumes that the drilling fluid is driven by constant flow or pressure at the fracture inlet. However, drilling fluid loss is a complex physical process in the coupled wellbore circulation system. The lost drilling fluid is driven by dynamic bottomhole pressure (BHP) during the drilling process. The use of a single-phase model to describe drilling fluids ignores the influence of solid-phase particles in the drilling fluid system on its rheological properties. This paper aims to model drilling fluid loss in the coupled wellbore–-fracture system based on the two-phase flow model. It focuses on the effects of well depth, drilling pumping rate, drilling fluid density, viscosity, fracture geometric parameters, and their morphology on loss during the drilling fluid circulation process. Numerical discrete equations are derived using the finite volume method and the “upwind” scheme. The correctness of the model is verified by published literature data and experimental data. The results show that the loss model without considering the circulation of drilling fluid underestimates the extent of drilling fluid loss. The presence of annular pressure loss in the circulation of drilling fluid will lead to an increase in BHP, resulting in more serious loss. Full article

Composite breakwater is a commonly employed structure for coastal and harbor protection. However, strong hydrodynamic impact can lead to failure and instability of these protective structures. In this study, a two-dimensional fluid-porous-solid coupling model is developed to investigate the stability of composite breakwaters. The fluid-porous model is based on the Volume-Averaged Reynolds-Averaged Navier-Stokes equations, in which the nonlinear Forchheimer equations are added to describe the porous layer. The solid model employs the Nodal-based Discontinuous Deformation Analysis (NDDA) method to analyze the displacement of the caisson. NDDA is a nodal-based method that couples FEM and DDA to improve non-linear processes. This proposed coupled model permits the examination of the influence of the thickness and porosity of the porous layer on maximum impacting wave height (${\mathrm{IWH}}_{\max }$) and the turbulent kinetic energy (TKE) generation. The results show that high porosity values lead to the dissipation of TKE and reduce the ${\mathrm{IWH}}_{\max }$. However, the reduction in the ${\mathrm{IWH}}_{\max }$ is not monotonic with increasing porous layer thickness. We observed that ${\mathrm{IWH}}_{\max }$ reaches an optimum value as the porous layer thickness continues to increase. These results can contribute to improve the design of composite breakwaters. Full article

Rotary lip seals serve as critical sealing components in industrial equipment, traditionally relying on the reverse pumping theory for their sealing mechanism. However, increasing operational demands characterized by high fluid pressure differentials, elevated speeds, and multi-physics coupling environments have revealed limitations in the applicability of the classical theory. This study aims to develop a comprehensive model to quantitatively characterize rotary lip seal performance, specifically frictional torque and reverse pumping rate, and to elucidate underlying mechanisms beyond classical theory. We developed a Mixed Thermo-Hydrodynamic Lubrication (MTHL) model that explicitly integrates fluid–solid–thermal coupling effects to simulate seal behavior under complex operating parameters. The simulations reveal that reverse pumping rate increases near-linearly with rotational speed from −8.54 mm³/s (0 m/s) to 122.82 mm³/s (3 m/s) and 220.27 mm³/s (6 m/s), validating classical theory, while under elevated fluid pressure differentials, a distinct non-monotonic trend emerges: rates evolve from 122.82 mm³/s (0.10 MPa) to 172.93 mm³/s (0.12 MPa), then decline to 52.67 mm³/s (0.18 MPa), and recover to 69.87 mm³/s (0.22 MPa), a phenomenon that cannot be explained by classical sealing mechanisms. Mechanistic analysis indicates that this anomaly stems from a competitive interaction between pressure-driven and shear-driven flow. This discovery not only enhances the reverse pumping theoretical system but also provides a theoretical foundation for optimizing sealing performance under diverse operational conditions. Full article

Over the last decades, Computational Fluid Dynamics (CFD) has become a fundamental tool for the design of gas turbine combustors, partly making up for the costs and duration issues related to the experimental tests involving high-pressure reactive processes. Nevertheless, high-fidelity simulations of reactive flows remain computationally expensive, particularly for conjugate heat transfer (CHT) analyses aimed at predicting liner metal temperatures and characterising wall heat losses. This work investigates the robustness of a cost-effective numerical setup for CHT simulations, focusing on the prediction of cold-side thermal loads in industrial combustor liners under realistic operating conditions. The proposed approach is tested using both Reynolds-Averaged Navier–Stokes (RANS) and unsteady Stress-Blended Eddy Simulation (SBES) turbulence models for the combustor flame tube, coupled via a time desynchronisation strategy with transient heat conduction in the solid domain. Cold-side heat transfer is modelled using a 1D correlation-based tool, runtime coupled with the CHT simulation to account for cooling-induced thermal loads without explicitly resolving complex cooling passages. The methodology is applied to a single periodic sector of the NovaLT^TM16 annular combustor, developed by Baker Hughes and operating under high-pressure conditions with natural gas. Validation against experimental data demonstrates the methodology’s ability to predict liner metal temperatures accurately, account for modifications in cooling geometries, and support design-phase evaluations efficiently. Overall, the proposed approach offers a robust trade-off between computational cost and predictive accuracy, making it suitable for practical engineering applications. Full article