Search Results (188)

The hot deformation behavior and microstructure evolution of a novel near-α Ti65 titanium alloy with an initial lamellar microstructure were investigated by isothermal compression. Compression tests were conducted at 950–1010 °C in the α + β phase region and 1050–1110 °C in the β phase region, with strain rates of 0.01–10 s⁻¹ and deformation amounts of 30–75%. The flow behavior, strain-compensated Arrhenius constitutive model, processing map and microstructural evolution were systematically analyzed. The results indicate that the flow stress decreases with increasing temperature and decreasing strain rate, while flow softening is more pronounced in the α + β region than in the β region. The apparent activation energies are 1050.27 kJ/mol for the α + β region and 203.51 kJ/mol for the β region, indicating distinct deformation mechanisms. The established constitutive models exhibit high prediction accuracy, with R and AARE values of 0.98 and 5.97% in the α + β region and 0.99 and 4.29% in the β region, respectively. Processing-map analysis identifies two instability domains at high strain rates: 990–1020 °C/3.5–10 s⁻¹ in the upper α + β region and 1060–1110 °C/1.65–10 s⁻¹ in the β region. Microstructural observations reveal that dynamic spheroidization of lamellar α dominates deformation in the α + β region, whereas dynamic recovery accompanied by limited β dynamic recrystallization occurs in the β region. Increasing deformation amount at 980 °C and 0.01 s⁻¹ promotes α-lamella fragmentation, spheroidization, grain refinement and texture weakening. The maximum pole density decreases to 6.23 mrd at a high deformation amount. By directly correlating strain-dependent processing-map characteristics with quantitative microstructural and crystallographic evolution, this work provides a microstructure-based basis for optimizing the hot-working window of Ti65 alloy with an initial lamellar microstructure. Full article

Structural fractures and karst cavities are widely developed in deep and ultra-deep carbonate reservoirs, providing preferential pathways for rapid fluid migration while increasing the risk of severe drilling fluid loss. To investigate the lost-circulation mechanism in fractured-vuggy formations, a hydro-mechanically coupled gas–liquid two-phase seepage model was established by considering the multiple-media characteristics of matrix, fractures and cavities, as well as rock deformation and fluid compressibility. We hypothesize that gas–liquid property differences and hydro-mechanical changes in conductivity jointly control drilling fluid loss, with the gas–liquid property contrast exerting the stronger effect under the simulated conditions. In the model, flow in the matrix and fractures is described by Darcy’s law, while high-velocity flow in cavities is characterized using the Forchheimer non-Darcy equation. The coupling between the seepage field and stress field is achieved by incorporating the effective stress relationship, using the Kozeny–Carman porosity–permeability evolution model and the Goodman fracture deformation model. The coupled equations were implemented in COMSOL. Model validation confirms the reliability of the proposed model in predicting drilling fluid loss. The fracture–vug system significantly enhances fluid exchange between the wellbore and formation. Pressure propagates rapidly along fractures and vugs at the early stage and subsequently diffuses into the surrounding matrix, while the loss rate generally decreases with time. After 120 min, hydro-mechanical coupling increased the loss rate from 1.15 × 10⁻³ to 1.23 × 10⁻³ m³/s and the cumulative loss volume from 11.41 to 12.06 m³. Compared with the single-phase model, the gas–liquid two-phase model predicted a 4.82-fold higher loss rate. Fracture aperture, vug size, bottomhole pressure differential, and rock mechanical properties are the principal factors controlling loss intensity and pressure propagation. Through effective stress variations, hydro-mechanical coupling modifies porosity, permeability, and fracture aperture, thereby affecting formation conductivity and dynamic loss behavior. These results provide theoretical guidance for lost-circulation mechanism analysis, risk assessment, and plugging optimization in deep fractured-vuggy carbonate formations. Full article

Soft-ground finite-element analyses commonly reduce curved Oedometer compression to one constant slope, obscuring where stress-level curvature affects boundary-value predictions. AJOP-T embeds the differentiable Arc Joint via Optimum Parameters map in continuous teardrop bounding-surface plasticity while retaining the inherited yield geometry, non-associated flow, radial mapping and SMP-transformed stress. High-order denotes only the map’s derivative hierarchy: its first two derivatives define tangent hardening and hardening curvature, not gradient, fractional, nonlocal or rate order. This first-phase formulation is deliberately rate-independent and retains constant κ to isolate compression-map hardening; time-dependent and nonlinear cyclic swelling responses are outside its claims. The formulation recovers constant-slope hardening asymptotically, yields a closed-form admissibility boundary, is invariant under SMP, and recovers the parent isotropic normally consolidated settlement equation. Four natural-clay compression maps were fitted; triaxial evidence is fitted for comparison except for one held-out Eastern Osaka extension path. Three implementations agree to at least five significant figures. Paired undrained strip-footing analyses reduce centre settlement by 31.8% in the curved regime but only 0.27% near the high-stress asymptote. A predicted 1.6% low-stress strength-ratio drift is below the reviewed data scatter and is not claimed as experimentally validated. Full article

High-fidelity reservoir simulation is too costly for multi-query tasks such as history matching and production optimisation. Existing reduced-order models (ROMs) mitigate this cost but generally lack uncertainty quantification, spatial sparsity, and interpretable mode-to-geology mappings. We introduce USX-PGD (Uncertainty-aware, Sparse, and eXplainable Proper Generalised Decomposition), a non-intrusive ROM for two-phase immiscible flow that addresses all three gaps within a single greedy Alternating Least Squares framework. USX-PGD is benchmarked against Proper Orthogonal Decomposition (POD), standard Proper Generalised Decomposition (PGD), and an intermediate Uncertainty-aware Sparse PGD (US-PGD) variant, on a formation-aware upscaled coarse-grid ($30\times 110\times 34$ cells) representation of the SPE10 Model 2 benchmark, a heterogeneous two-phase reservoir with permeability contrasts spanning six orders of magnitude. US-PGD adds sparsity-promoting thresholding and bootstrap resampling to certify a confidence interval on reconstruction accuracy; USX-PGD further adds formation energy decomposition, mode dominance mapping, breakthrough attribution, and mode sensitivity indexing, attributing the reduced-order modes to identifiable geological formations. All four methods reproduce the reference production curves to within $11.03$–$11.05\%$ NRMS at online reconstruction times of 51–63 ms; the sparse and explainable variants achieve comparable accuracy while additionally providing $41.8\%$ spatial sparsity and a certified $95\%$ confidence interval. All four ROMs compress and replay an already-simulated trajectory, not predict new, unsimulated scenarios; USX-PGD is offered as a reproducible, physically transparent foundation for such multi-query workflows, with predictive extension identified as future work. Full article

We develop a KvN/Weyl/Wigner/Moyal phase-space formulation for shock-containing compressible, irrotational, barotropic Euler flow. Smooth branches are represented by branchwise Wigner distributions, while piecewise-smooth entropy-admissible shocks generate an interface-supported defect in the weak phase-space balance. This defect is concentrated on the moving shock surface and is weighted by the normal relative transport flux between the one-sided branches. An exact planar constant-state three-dimensional example shows how the same mass flux is transferred between distinct velocity-space supports and how its moments recover the classical jump structure. We also introduce a shock solution of the one-dimensional Burgers equation with a triangular initial profile as an exactly solvable reduced benchmark. In this example, the shock trajectory, transported branch weights, branchwise Wigner transforms, and a two-component localized phase-space defect are obtained in closed form. The construction is a restricted branchwise representation of Euler shocks already selected by the Rankine–Hugoniot and entropy conditions; it is not a new admissibility criterion or a complete global Wigner theory across discontinuities. The formulation separates smooth phase-space evolution from singular interface contributions within a unified construction and provides a compact diagnostic description of shock-supported phase-space structure. Full article

In salt cavern compressed air energy storage (CAES) systems, slag particles entrained by high-pressure airflow can cause pipeline wear and flow instability, posing challenges to long-term operational safety. However, direct experimental studies are constrained by high-pressure, large-scale conditions and transient multiphase flow complexities. This study uses Fluent, a numerical simulation method based on gas–solid two-phase flow theory, to investigate the flow characteristics, particle dynamics, and erosion behavior in the above-ground pipeline of CAES system. Results reveal uneven gas velocity distribution, with the lowest flow (≤2.3 (m/s)) in the main pipeline favoring particle deposition, and complex vortex structures at branch connections. Particles accumulate on the outer wall of 90° elbows due to centrifugal effects, leading to localized erosion, with severe wear occurring at impact angles of 20–30°. Over a 30-year operational cycle, the predicted maximum wear depth is 0.38 mm, which remains below the existing protective cladding thickness of 0.5 mm. The findings not only provide a theoretical basis and design insights for optimizing wear protection strategies, but also hold positive implications for enhancing the economic sustainability and environmental benefits of large-scale energy storage systems. Full article

Constitutive models for clays have historically treated yield geometry, plastic-flow direction, and compression as separate problems, with little regard for their interaction. This paper presents a controlled numerical assessment of how three components—Chatwong et al.’s verified teardrop yield surface, a stress-fractional flow rule, and an AJOP-derived hardening modulus— interact when coupled in a 2 × 2 × 2 factorial design. The components are integrated incrementally along one idealized shear-strain-controlled constant-p′ path with an approximate undrained variant for two independently calibrated clays (Boston Blue Clay and London Clay) under a specified state-dependent fractional order. Within this scope, the main flow effect is consistently the largest single quantity for both soils, and the flow × compression interaction is comparably large wherever defined. Compression’s role grows substantially with the overconsolidation ratio, and the main geometry effect is markedly soil-dependent, scaling with the surface-shape parameter. Two structural singularities are identified: a phase-transformation point in the teardrop surface’s non-associated flow rule, absent from the fractional rule, and a hardening singularity in the AJOP-based modulus, whose tangent falls to the swelling index at a finite, soil-dependent preconsolidation stress, bounding the evaluable overconsolidation range of the compression-related interactions; a proportional-κ variant removes this singularity by construction while preserving the factorial ranking, identifying it as a property of the constant-κ embedding, not of AJOP itself. Under an approximate undrained path, the geometry × flow interaction carries over unchanged, while compression’s role is suppressed several-fold. The borrowed yield surface and flow rule are validated independently against 379 points from real undrained triaxial tests across four calibrated soils using this paper’s own re-calibrated predictions; the fractional–AJOP framework itself is assessed for internal consistency only, and its laboratory validation, together with K₀, cyclic and multi-axial paths, remains for future work. Full article

Rapid filling of urban drainage pipelines during intense rainfall can compress entrapped air and trigger pressure surges or geysering when air release through manhole-cover openings is restricted. Unlike studies focusing on simplified pipes or isolated shafts, this work examines the coupled air–water response of a prototype-scale drainage section with drop structures, branch inflows, variable-diameter inverted siphons, multiple shafts, and restricted manhole-cover venting. A three-dimensional unsteady air–water two-phase model was established and applied to nine two-stage inflow scenarios after validation against published rapid-filling pressure data. The results show that hydraulic slugs segmented the continuous crown air layer into localized air pockets and produced a high-pressure concentration zone upstream of the downstream diameter change, with a maximum shaft-top pressure of 29.2 kPa under the representative high-flow condition. In local shafts, insufficient venting through small openings, bottom water sealing, and continuous air supply jointly induced delayed geysering cycles characterized by pressure accumulation, breakthrough, relief, and re-accumulation, with a period of 110–120 s and peak pressures of 19–21 kPa. The second-stage rapid-filling flow rate dominated downstream peak pressures; when it increased from 9 to 11 m³/s, the peak pressure at a representative downstream shaft rose from 16 to 34 kPa. These findings clarify the mechanisms of high-pressure concentration and delayed geysering under restricted venting and support the identification of pressure-sensitive nodes in complex drainage networks. Full article

The expansion of deep-buried tunnels into complex geological settings has heightened the risk of encountering high-pressure gas strata. This study addresses a critical knowledge gap regarding safe rock-pillar thickness when tunneling through high-pressure CO₂-bearing formations, motivated by a 2.3 MPa CO₂ blowout event encountered during the geological investigation of a deep railway tunnel in western China. Numerical simulations were conducted using Phase2/RS2 (2D plane-strain models for the tunnel floor) and FLAC3D (3D models for the tunnel face) to evaluate plastic zone evolution and displacement responses under prescribed equivalent static CO₂ pressure conditions and rock-mass degradation scenarios. The simulations represent a mechanical assessment under a prescribed pressure condition rather than a fully coupled gas-flow–mechanical analysis. Under the equivalent static CO₂ pressure assumption, the calculated plastic zone depth increased from 10.2 m in the no-pressure case to 17.4 m under the 2.3 MPa pressure condition, while the maximum floor displacement increased from 0.4 cm to 11.0 cm. These results represent a conservative mechanical response under the adopted pore-pressure efficiency assumption and should not be interpreted as a direct simulation of gas compressibility, capillary effects, pressure diffusion, or gas–water two-phase behavior. Under the adopted parametric degradation scenarios, rock-mass strength reduction further increases the calculated plastic zone depth and displacement. In the strong degradation case, the plastic zone depth reaches 32.6 m and the maximum displacement reaches 19.0 cm. These values should be interpreted as sensitivity-analysis results for the assumed degraded rock-mass conditions, rather than as general predictions for all fractured or weathered rock masses. For face stability, the critical coalescence distance between excavation-disturbed and high-pressure-affected zones was identified as 15 m for intact rock, advancing to 20 m and 30 m under 10% and 20% strength reductions, respectively. Based on these findings, preliminary conservative reference values are proposed for risk identification when tunneling toward high-pressure CO₂-bearing fractured zones. The calculated floor plastic zone depth of 17.4–32.6 m and the face coalescence distance of 15–30 m should be interpreted as mechanical warning indicators under the adopted equivalent static pressure assumption. These values have not yet been validated by construction-stage monitoring data and should therefore be updated using gas-pressure measurements, deformation monitoring, support response, drainage performance, and field back-analysis during tunnel construction. Full article

To ensure that the necessary gas-phase safety space is retained after the filling of a liquid hydrogen cylinder and to reduce the risk of rapid pressure rise caused by overfilling, a 34 L vehicle-mounted liquid hydrogen cylinder was taken as the research object. A non-isothermal two-dimensional numerical model considering gas–liquid two-phase flow, heat transfer, and phase change was established. The dynamic and thermal characteristics of cylinders with and without a gas phase space were compared under different filling rates. The results show that, during liquid hydrogen filling, the liquid phase first accumulates at the bottom of the main chamber. Then, the liquid level rises and compresses the upper gas phase, and part of the liquid hydrogen enters the gas-phase space in the later stage. The gas-phase space can delay the occupation of the safety gas cushion by liquid hydrogen, allowing a certain volume of compressible gas to remain during overfilling. The pressure variation presents three stages: a rapid increase in the initial stage, a slower increase in the middle stage, and another rapid increase in the final stage. These stages are related to liquid hydrogen flash evaporation, gas-phase cooling and condensation, and compression of the remaining gas, respectively. The tank temperature generally shows a rapid decrease followed by a slower decrease. As the filling rate increases, the liquid level rises faster, the gas–liquid interface disturbance becomes stronger, the liquid hydrogen enters the gas-phase space earlier, the pressure rise rate increases, and the buffering effect weakens. The results indicate that the gas-phase space structure can improve the safety margin in the final stage of liquid hydrogen cylinder filling, but the filling rate should still be reasonably controlled in actual filling processes. Full article

A numerical study of shock wave propagation through multiple raindrops is presented using a density-based compressible two-phase flow solver coupled with a sharp-interface volume-of-fluid (VoF) method. The piecewise linear interface calculation (PLIC) approach is employed to reconstruct gas–liquid interfaces and capture droplet deformation during shock interaction. The numerical framework is first validated using a one-dimensional gas–liquid shock tube problem and a shock–helium bubble interaction benchmark. The method is then applied to investigate shock interactions with single, double, and multiple raindrops under compressible flow conditions. Numerical results show that complex wave structures, including shock reflection, diffraction, and wave interference, develop during shock propagation through raindrop fields. Interactions between neighboring droplets lead to local pressure amplification and non-uniform flow structures. Full article

To clarify the oil–gas multiphase flow behavior of natural gas/CO₂ composite flooding in the dual-medium system of the BZ26-6 fractured reservoir, systematic oil–gas relative permeability experiments were conducted under reservoir temperature and pressure conditions. Using the steady-state method, the effects of core type, gas composition, and reservoir pressure on relative permeability behavior were investigated. The results show that the relative permeability curves are characterized by relatively high oil-phase permeability and low gas-phase permeability. Increasing the CO₂ fraction generally enhances oil mobilization and displacement efficiency, whereas the two-phase co-flow zone may reach an optimum at an intermediate CO₂ fraction, depending on the core structure. Specifically, with increasing CO₂ fraction, displacement efficiency increased from 37.05% to 43.70% in fractured metamorphic cores and from 60.74% to 64.63% in fractured carbonate cores. In contrast, decreasing reservoir pressure may induce stress-sensitive fracture compression, narrow the co-flow zone, and reduce flow capacity. Oil–gas two-phase flow behavior is strongly controlled by reservoir structure, with fractured carbonate cores exhibiting higher displacement efficiency and a wider co-flow region than fractured metamorphic cores. Within the scope of this study, a CO₂ fraction of 40% appears to be a comparatively favorable composite-gas composition when both displacement performance and gas-source economics are considered. Full article

Shock-induced gas/water interfacial instability is important in multiphase flow processes involving rapid deformation, mixing, and breakup. In this study, the evolution of shock-impacted gas/water interfaces was investigated using high-speed images from previously conducted shock-tube experiments and two-phase numerical simulations. Interface contours were extracted through digital image processing, and spatial Fourier analysis was used to describe the modal evolution of interfacial perturbations. A numerical model based on the VOSET interface-capturing method and the SST $k-\omega$ turbulence model was established, with the compressibility of both phases considered. A mode number–amplitude–time (K-L-t) diagnostic framework was proposed. The results show that this framework can distinguish the dominant stages associated with Richtmyer–Meshkov (RM), Rayleigh–Taylor (RT), and Kelvin–Helmholtz (KH) instabilities. In the double-liquid-column case, the downstream interface exhibits a delayed transition, which may be associated with shielding and wake interference. Increasing the shock Mach number accelerates modal growth and advances the transition times, whereas increasing the liquid-column diameter delays the instability evolution because of larger inertia. A modified RM dispersion equation incorporating compressibility and finite-thickness effects was further proposed, showing improved agreement with the CFD-extracted initial growth rates. Full article

The training of physics-informed neural networks (PINNs) for nonlinear multiphase flow in porous media is hampered by gradient conflicts between the individual components of the composite loss function. To address this problem, we propose a weighted gradient consistency metric that jointly accounts for the magnitudes and directions of the gradients of each loss term. Theoretical estimates of the convergence rate are derived, relating the proposed metric to the spectral properties of the preconditioner. The method is evaluated through a comparative study of optimizers—Adam, L-BFGS, and self-scaled Broyden—applied to three formulations of increasing complexity: a linear Buckley–Leverett model, a compressible two-phase model, and a fully nonlinear model with non-Newtonian rheology. The experiments demonstrate that self-scaled methods consistently achieve higher gradient alignment, faster loss reduction, and improved approximation accuracy compared to standard quasi-Newton and first-order baselines. Full article

Compressed CO₂ energy storage (CCES) in deep sedimentary basins offers a promising option to integrate carbon management with long-duration energy storage. However, most existing subsurface energy-storage studies focus on salt caverns or generic porous reservoirs, while the potential of evaporite-bounded carbonate reservoirs remains insufficiently explored. This study presents the first application-oriented numerical assessment of CCES in Southern Ontario. It investigates the feasibility of CCES in the Upper Silurian Salina Group beneath offshore Lake Huron, focusing on a porous A-2 carbonate interval vertically confined by B and A-2 halite caprocks. A fully coupled three-dimensional thermo-hydro-mechanical model is developed in COMSOL Multiphysics 6.3 to simulate two-phase (brine-CO₂) Darcy flow, heat transfer, and poroelastic deformation under a realistic Michigan Basin stress, pressure and geothermal regime. After an initial cushion-gas stage at 8 kg/s that establishes a caprock-parallel supercritical CO₂ wedge beneath the B-salt, 24 h injection-production cycles are imposed for two years, followed by a five-month high-resolution window. Three well completion strategies are compared: full-length, upper-only, and split (upper + lower) perforations. Results indicate that in all simulations the CO₂ plume stabilizes as a persistent gas cap beneath the B-salt, far-field pressures remain close to hydrostatic, and reservoir deformations are very small, pointing to a substantial geomechanical safety margin. Among the three completion strategies, the split completion provides the best compromise: it maintains high and relatively stable CO₂ production while avoiding the stronger lower-zone depressurisation seen in the full-length case and the more limited working volume of the upper-only case. These findings suggest that a Salina A-2 carbonate reservoir bounded by B and A-2 salts can accommodate cyclic CCES under realistic basin conditions, and that appropriately designed split completions offer a practical balance between storage utilisation and operational robustness in this setting. Full article