Search Results (320)

A kinetic and thermodynamic multi-phase model has been developed to describe the adsorption of gases on ice surfaces and their subsequent diffusional loss into the bulk ice phase. This model comprises a gas phase, a solid surface, a sub-surface layer, and the ice bulk. The processes represented include gas adsorption on the surface, solvation into the sub-surface layer, and diffusion in the ice bulk. It is assumed that the gases dissolve according to Henry’s law, while the surface concentration follows the Langmuir adsorption equilibrium. The flux of molecules from the sub-surface layer into the ice bulk is treated according to Fick’s second law. Kinetic and thermodynamic quantities as applicable to the uptake of small carbonyl compounds on ice surfaces at temperatures around 200 K have been used to perform model calculations and corresponding sensitivity tests. The primary application in this study is acetic acid. The model simulations are applied by fitting the experimental data obtained from coated-wall flow-systems (CWFT) measurements, with the best curve-fit solutions providing reliable estimations of kinetic parameters. Over the temperature range from 190 to 220 K, the estimated desorption coefficient, k_des, varies from 0.02 to 1.35, while adsorption rate coefficient, k_ads, ranges from 3.92 and 4.17, and the estimated diffusion coefficient, D, changes by more than two orders of magnitude, increasing from 0.03 to 13.0. Sensitivity analyses confirm that this parameter estimation approach is robust and consistent with underlying physicochemical processes. It is shown that for shorter exposure times the loss of molecules from the gas phase is caused exclusively by adsorption onto the surface and solvation into the sub-surface layer. Diffusional loss into the bulk, on the other hand, is only important at longer exposure times. The model is a useful tool for elucidating surface and bulk process kinetic parameters, such as adsorption and desorption rate constants, solution and segregation rates, and diffusion coefficients, as well as the estimation of thermodynamic quantities, such as Langmuir and Henry constants and the ice film thickness. Full article

The adverse-pressure-gradient (APG) severely disrupts the inherent symmetry of the turbulent boundary layer (TBL). The universal physical behavior and scaling laws observed under zero-pressure-gradient (ZPG) conditions are significantly altered under APG, thereby challenging the predictive accuracy of turbulence models. To address this breakdown, we develop a generalized mixing length model by incorporating APG effects into a baseline ZPG framework. The model is directly constructed using APG-extended wall laws—superposing the log law and the half-power law for the mean velocity—and the logarithmic decay law for the total shear stress. Validated against ten databases spanning the entire APG region, various Reynolds numbers, and both equilibrium and non-equilibrium flows, the model demonstrates accurate predictions for both mixing length and mean velocity profiles. The key achievements are as follows: (i) a significant simplification of model parameters, wherein the inner model can be reduced to a parameterless scaling law, while outer parameters were reduced from five to two; and (ii) the unification of predictions across the entire APG range. This work demonstrates that consistent modeling of APG effects bridges slight and strong APGs, enabling a unified description of the APG region before separation and providing critical insights for turbulence modeling. Full article

In many mountainous areas of China, frequent geological disasters pose a serious threat to human life and property. The Luding “9.5” earthquake triggered a large number of landslide disasters, causing serious loss of life and property. Therefore, it is extremely urgent to carry out research on the stability analysis and treatment methods of landslides in the Luding area. In this paper, the Caiyangba landslide in Yanzigou Town, Luding County, is taken as the research object. The slope model is constructed by Midas to study the stability development law of Caiyangba landslide under different rainfall conditions and seismic conditions, and to explore the feasibility of the “anchor lattice treatment method”. The results show that the “anchor lattice treatment method” can effectively improve the stability of the slope under rainfall conditions. The improvement effect of slope stability decreases with the increase in rainfall duration and rainfall. The development law of the slope stability coefficient with rainfall duration in WMG (the working condition of not adopting the “anchor lattice treatment method” is referred to as WMG) and MG (the working condition of adopting the “anchor lattice treatment method” is referred to as MG) conditions conform to the development law of exponential function, and the expression of instantaneous change rate of slope stability coefficient is derived. The above function can also well explain the development law of X-direction displacement and Y-direction displacement of SP (school: monitoring point) and RP (road: monitoring point); the development law of the instantaneous change rate of displacement. Under the influence of ground motion, the improvement effect of the “anchor lattice treatment method” on the slope stability coefficient is limited, but the improvement effect of slope stability increases with the increase in seismic intensity. The slope stability coefficient and the displacement of SP and RP show obvious fluctuation with time, and the fluctuation law is similar to that of ground motion records. It is recommended to add a gravity-retaining wall at the foot of the slope. The teaching building reduces the number of floors and increases the number of pile foundations. Roads should restrict the passage of heavy vehicles, such as cars and strictly stacked items. The above results can provide a theoretical reference for the sustainable treatment and sustainable development of landslides in the Luding area. Full article

This study proposes a novel graded-thickness, thin-walled aluminum alloy (Al) circular tube energy-absorbing structure and conducts comprehensive parametric modeling and multi-objective optimization research. The 7050Al tube was selected for analysis of its energy absorption characteristics via numerical simulations and drop-weight impact tests. Through simulation calculations and drop hammer impact verification tests, the number and location of concertina lobes after crushing, as well as the force variation law of the structure during the crushing process, were analyzed. The results indicate that generating annular folds at the impact end can significantly enhance impact absorption and suppress structural instability. Drop-weight test results further validate the superior crashworthiness of the proposed 7050Al tube under dynamic loading conditions and confirm the accuracy of the numerical crushing model. To enable rapid and precise structural modifications, a Python-based parametric modeling framework has been developed. A fully automated parametric optimization workflow has been established within Isight to facilitate the efficient, multi-objective optimization of the structure’s design. This methodology provides a robust tool for designing customizable energy-absorbing structures with tailored crashworthiness performance. Full article

This work introduces a block-coupled finite volume method for simulating the large-strain deformation of incompressible hyperelastic solids. Conventional displacement-based finite-volume solvers for incompressible materials often exhibit stability and convergence issues, particularly on unstructured meshes and in finite-strain regimes typical of biological tissues. To address these issues, a mixed displacement–pressure formulation is adopted and solved using a block-coupled strategy, enabling simultaneous solution of displacement and pressure increments. This eliminates the need for under-relaxation and improves robustness compared to segregated approaches. The method incorporates several enhancements, including temporally consistent Rhie–Chow interpolation, accurate treatment of traction boundary conditions, and compatibility with a wide range of constitutive models, from linear elasticity to advanced hyperelastic laws such as Holzapfel–Gasser–Ogden and Guccione. Implemented within the solids4Foam toolbox for OpenFOAM, the solver is validated against analytical and finite-element benchmarks across diverse test cases, including uniaxial extension, simple shear, pressurised cylinders, arterial wall, and idealised ventricle inflation. Results demonstrate second-order spatial and temporal accuracy, excellent agreement with reference solutions, and reliable performance in three-dimensional scenarios. The proposed approach establishes a robust foundation for fluid–structure interaction simulations in vascular and soft tissue biomechanics. Full article

This study addresses the trade-off between accuracy and efficiency in predicting the aerodynamics and wakes of large wind turbines. We developed a unified immersed boundary–actuator line framework with large-eddy simulation. The actuator line efficiently represents blade loading, while the immersed boundary method (IBM) with a wall model resolves near-blade turbulence. The solver uses a staggered Cartesian discretization and is accelerated by a hybrid CPU/GPU implementation. An implicit signed-distance geometry treatment and a ghost cell wall function based on Spalding’s law reduce near-wall grid requirements and eliminate body-fitted meshing. Flow past a three-dimensional cylinder at Re = 3900 validates the accuracy and good grid convergence of the IBM. For the wind turbine, three meshes show converged thrust and torque, with differences below 1% between the two finer grids. At the rated condition (U_∞ = 11.4 m/s), thrust and torque agree with STAR-CCM+ and FAST, with deviations of 6.3% and 1.2%, respectively. Parametric cases at 4–10 m/s show thrust and torque increasing nonlinearly with inflow, approximately quadratically, in close agreement with reference models. As wind speed rises, the helical pitch tightens, the wake broadens, and breakdown occurs earlier, consistent with stronger shed vorticity. The framework delivers high fidelity and scalability without body-fitted meshes, offering a practical tool for turbine design studies and extensible wind plant simulations. Full article

Aortic valve calcification is the process of calcium buildup on the leaflets of the aortic valve, preceding functional insufficiency. Calcification underlies the development of aortic stenosis by stiffening the valve leaflets, leading to restricted aortic valve opening during systole and obstructed blood flow. However, a more comprehensive understanding of the hemodynamic effects of altered valve properties is required. Therefore, it is crucial to investigate the biomechanical properties of aortic valve leaflets susceptible to calcification. To examine fluid flow in an aorta segment with leaflets of different stiffness, a two-way fluid–structure interaction model was developed. The leaflet’s behavior was modeled using two constitutive laws—linear-elastic and isotropic hyperelastic—followed by numerical testing and comparative analysis. Using the material parameter values $c_{01}$ and $c_{10}$ within the ranges of 22–60 and 22–60 kPa, respectively, the hyperelastic model was examined. The valve leaflets’ Young’s modulus ranged from 1 to 22 MPa, while their Poisson’s ratio ranged from 0.35 to 0.45. A high correlation between Poisson’s ratio and wall shear stress was found. With an elastic modulus of 22 MPa and the highest Poisson’s ratio of 0.45, the maximum wall shear stress was 81.78 Pa during peak flow velocity and complete valve opening, while the lowest wall shear stress was 0.38 Pa. We can infer from the study’s results that, when considering the isotropic structure and nonlinear characteristics of valve leaflets, the Delfino hyperelastic model more accurately depicts their complex behavior. Full article

A complex operating environment and high operating temperature lead to the uneven temperature field distribution of key components of the molten salt Linear Fresnel collector in a way that compromises the collector’s safety and stability. To investigate the influence of different working conditions on the temperature field of the molten salt Linear Fresnel collector under multi-physical field conditions, this study develops a three-dimensional numerical model based on ANSYS that integrates the loading of solar radiation and thermal–fluid coupling, compares and verifies the accuracy of the model through the collector field data of the actual operation, and systematically analyzes the distribution characteristics of the receiver tube and outlet temperature field and its rule of change. The results show that temperatures of the receiver tube and exit during operation exhibit pronounced non-uniform distribution characteristics, in which the inlet flow rate of the molten salt and intensity of solar irradiation have the most critical influence on the temperature distribution throughout the receiver tube and its exit, and the heat transfer temperature difference between the molten salt and heat conduit wall is reduced as the inlet temperature raises, which makes the receiver tube and molten salt outlet temperature gradient slightly reduced. This study not only supplements and improves the numerical simulation study of the molten salt Linear Fresnel collector under complex working conditions but also reveals the distribution law of the temperature field between the receiver tube and the outlet, which provides adequate numerical support for the safe and stable operation of the collector. Full article

Accurate object detection and measurement within indoor environments—particularly unfurnished or minimalistic spaces—pose unique challenges for conventional computer vision methods. Previous research has been limited to small objects that can be fully detected by applications such as YOLO, or to outdoor environments where reference elements are more abundant. However, in indoor scenarios with limited detectable references—such as walls that exceed the camera’s field of view—current models exhibit difficulties in producing complete detections and accurate distance estimates. This paper introduces a geometry-driven, redundancy-based framework that leverages proportional laws and architectural heuristics to enhance the measurement accuracy of walls and spatial divisions using standard smartphone cameras. The model was trained on 204 labeled indoor images over 25 training iterations (500 epochs) with augmentation, achieving a mean average precision (mAP@50) of 0.995, precision of 0.995, and recall of 0.992, confirming convergence and generalisation. Applying the redundancy correction method reduced distance deviation errors to approximately 10%, corresponding to a mean absolute error below 2% in the use case. Unlike depth-sensing systems, the proposed solution requires no specialised hardware and operates fully on 2D visual input, allowing on-device and offline use. The framework provides a scalable, low-cost alternative for accurate spatial measurement and demonstrates the feasibility of camera-based geometry correction in real-world indoor settings. Future developments may integrate the proposed redundancy correction with emerging multimodal models such as SpatialLM to extend precision toward full-room spatial reasoning in applications including construction, real estate evaluation, energy auditing, and seismic assessment. Full article

The new type of gold cone filter cartridge has dual functions of increasing filter area and enhancing pulsed-jet cleaning, but the issue of patchy cleaning remains to be addressed. This study further enhances the pulsed-jet cleaning performance of cone filter cartridges by employing a porous diffusion nozzle. The temporal and spatial distributions of pulse jet velocity and pressure under the condition of porous nozzles were investigated through numerical modeling. The variation law of pressure on the side wall of the filter cartridge was analyzed. The influence of jet distance of porous nozzles on pulsed-jet pressure and pulsed-jet uniformity was experimentally investigated. Dust filtration and cleaning experiments were conducted, and the filtration pressure drop, dust emission concentration, and comprehensive filtration performance were compared. It was found that the airflow jetted by the porous diffusion nozzle is more divergent than that of the common round nozzle. This results in a larger entrainment of the jet stream, a milder collision of the jet stream with the cartridge cone, and a slower overall velocity reduction. More airflow is generated into the filter cartridge and accumulated; the accumulated static pressure covers a larger range of the upper section of the filter cartridge, with a longer duration of static pressure. In the online dust filtration and cleaning experiment, compared with the condition of the common round nozzle, the porous nozzle can reduce the residual pressure drop by 27.0%, increase the filtration cleaning interval by a factor of 3.80, reduce the average dust emission concentration by 45.2%, and increase the comprehensive performance index Q_F by 5.2%. The research conclusions can provide references for the design and optimization of industrial filter cartridge dust collectors. Full article

Permeability of fissured sorbing rocks, such as coal and shale, controls gas transport and is relevant to a variety of scientific problems and industrial processes. Multiple gas transport and rock deformation mechanisms affect permeability evolution, including gas rarefaction effects, gas-sorption-induced anisotropic matrix–fracture interaction, and anisotropic deformation induced by effective stress variation. In this paper, a generic anisotropic permeability model is proposed to address the impacts of the above mechanisms and effects. Specifically, the influence of matrix–fracture interactions on permeability evolution is depicted through the nonuniform matrix swelling caused by the gas diffusion process from fracture walls into the matrix. The following characteristics are also incorporated in this model: (1) anisotropic mechanical and swelling properties, (2) arbitrary box-shaped matrix blocks due to the anisotropic rock structure, (3) adsorbability variation of different matrix blocks because of complex rock compositions, (4) adsorption hysteresis, and (5) dynamic tortuosity. The directional permeability models are derived based on the anisotropic poroelasticity theory and anisotropic swelling equations considering adsorption hysteresis. We use a gas-invaded-volume ratio to describe the nonuniform swelling of matrix blocks. Additionally, swelling of blocks with different adsorption and mechanical properties are characterized by a volume-weighted function. Finally, the anisotropic tortuosity is defined as a power law function of effective porosity. The model is verified against experimental data. Results show that four-stage permeability evolution with time can be observed. Permeability evolution in different directions follows its own ways and depends on anisotropic swelling, mechanical properties, and structures, even when the boundary conditions are identical. Adsorption hysteresis controls the local shrinkage region. Tortuosity variation significantly affects permeability but has the smallest influence on the local swelling region. The existence of multiple matrix types complicates the permeability evolution behavior. Full article

High-precision angular contact ball bearings (ACBBs) are critical components in advanced manufacturing equipment, where rotation accuracy directly determines system performance and stability. Considering error superposition and equipment processing capability comprehensively, this study establishes an error analysis and control model of the ACBBs, studies the error transmission law, and puts forward a rotation accuracy control strategy for batch manufacturing of precision ACBBs. The ACBBs 7020C/P4, 7020AC/P4, 7020A/P4, and 7020B/P4 (four conventional contact angles of 15°, 25°, 30°, 40°) were taken as examples to verify the experiment. The error of the calculation compared with actual test results was not more than 7.5%, which had good accuracy and practicability. The research shows that the roundness error of bearing raceway, the thickness difference in bearing ring wall, and the parallelism error of raceway to end face were the main influencing factors of bearing rotation accuracy Kia, Sia, Kea, and Sea. The influence coefficient of raceway roundness error on the axial runout of bearing (Sia, Sea) decreased rapidly with the increase in contact angle, while the influence coefficient on radial runout (Kia, Kea) remained constant. The rotation accuracy error of the outer ring was always greater than that of the inner ring, and this law was not affected by the contact angle. Moreover, with the increase in contact angle, the radial runout of the inner and outer rings of the bearing increased. During actual machining, bearings with larger contact angle place lower demands on the equipment process capability index (Cp), particularly on the parameter Cer. This reduction in required capability is equivalent to an effective Cp improvement of about 30%. Full article

Buried pipelines in permafrost areas are affected by harsh environments, especially those with defects and damages, which are prone to failure or even leakage accidents. However, current research is limited to single-factor analysis and fails to comprehensively consider the interaction relationships among temperature fields, moisture fields, and stress fields. Therefore, based on the thermodynamic equilibrium equation and the ice–water phase transition theory, this paper constructs the temperature field equation including the latent heat of phase transition, the water field equation considering the migration of unfrozen water, and the elastoplastic stress field equation. A numerical model of the heat–water–force three-field coupling is established to systematically study the influence laws of key parameters such as burial depth, water content, pipe diameter, and wall thickness on the strain distribution of pipelines with defects. The numerical simulation results show that the moisture content has the most significant influence on the stress of pipelines. Pipelines with defects are more prone to damage under the action of freeze–thaw cycles. Based on data analysis, the safety criteria for pipelines were designed, the strain response surface function of pipelines was constructed, and the simulation was verified through experiments. It was concluded that the response surface function has good predictability, with a prediction accuracy of over 90%. Full article

Urban deep excavations conducted near operational tunnels necessitate stringent deformation control. This study investigates the Baiyun Station excavation by employing a three-dimensional finite-element model based on the Hardening Soil Small-strain (HSS) constitutive law, calibrated using Phase I field monitoring data on wall deflection, ground settlement, and tunnel displacement. Material parameters for the HSS model derived from the prior Phase I numerical simulation were held fixed and used to simulate the Phase II excavation, with peak errors of less than 5.8% for wall deflection and less than 2.9% for ground settlement. The model was subsequently applied to evaluate the impacts of Phase II excavation. The key contribution of this study is a monitoring-driven HSS modeling framework that integrates staged excavation simulation with field-based calibration, enabling quantitative assessment of tunnel responses—including settlement troughs, bow-shaped wall deflection patterns, and the distance-decay characteristics of lining displacement—to support structural safety evaluations and protective design measures. The results demonstrate that the predicted deformations and lining stresses in adjacent power and metro tunnels remain within permissible limits, offering practical guidance for excavation control in densely populated urban areas. Full article

For the possible damage to overhead pipelines caused by gas explosions in utility tunnels, an overall three-dimensional finite-element model of utility tunnel–soil–pipeline is established, the overpressure loads are applied to the inner wall of the gas chamber in the utility tunnel, the dynamic response laws of the utility tunnel and the pipeline are calculated and analyzed, and anti-explosion protection measures are proposed. The results show that the degree of damage to the pipe wall is determined by both the explosion-impacted area and the soil constraint. Under the same explosion-impacted area, the peak horizontal displacement of the monitoring point without soil constraint is 1.64 times that with soil constraint, and 1.29 times for the peak vertical displacement. The damage to the lower part of the pipeline is significantly greater than that to the upper part of the pipeline, and the damage to the pipeline decreases with an increase in the horizontal angle between the utility tunnel and the pipeline. The diameter deformation rates were 49% at α = 0° and 84% at α = 45°, with α = 90° showing the least damage. Therefore, it is suggested that the overhead pipeline is perpendicular to the utility tunnel. As the vertical distance between the utility tunnel and the pipeline increases, the diameter deformation rate and displacement of the pipeline both decrease, and when this distance is greater than 3 m, the influence on the pipeline significantly decreases. Therefore, it is recommended that the distance between the pipeline and the utility tunnel should be at least 3 m. In addition, the damage caused by gas explosions to the overhead pipeline can be reduced by reinforcing the gas chamber, using energy-absorbing materials around the utility tunnel, and setting up hollow piles between the utility tunnel and pipelines. Full article