Pressure Evolution Research Articles

Numerical Simulation of Thermo-Hydro-Mechanical Coupling of Model Test for Nuclear Waste Disposal

This article presents a simulation of a long-term retardation performance Mock-up test of the multi-field coupling of buffer materials, with the aim to study the thermo-hydro-mechanical (THM) processes occurring in the engineered barrier system of a high-level waste (HLW) repository. In view of the theory of mixtures and mechanics of continuous media, the coupled THM mathematical model of unsaturated buffer materials is established, considering heat transport and multiphase fluid flow. Using the buffer material Mock-up test of multi-field coupling as a model, the partial differential equation (PDE) module in the general finite element software COMSOL Multiphysics was developed by a second development stage. The dynamic response process of buffer material under the condition of THM coupling was numerically simulated, and the spatial distribution and variation law of suction, porosity, horizontal displacement, temperature and swelling pressure in the engineered barrier were investigated. The porosity of the buffer material under THM coupling was influenced by the swelling pressure and the suction. The welling pressure evolution of the buffer material may be influenced by the thermal expansion induced by high temperature and the swelling pressure generated by buffer material saturation. The evolution of the horizontal displacement of the heater used to simulate a container with radioactive waste was validated. This paper provides technical reference for the design and safety evaluation of underground laboratory barrier engineering in China.

The Emerging Predictive and Prognostic Role of Aggressive-Variant-Associated Tumor Suppressor Genes Across Prostate Cancer Stages.

Aggressive variant prostate cancer (AVPC) is characterized by a molecular signature involving combined defects in TP53, RB1, and/or PTEN (AVPC-TSGs), identifiable through immunohistochemistry or genomic analysis. The reported prevalence of AVPC-TSG alterations varies widely, reflecting differences in assay sensitivity, treatment pressure, and disease stage evolution. Although robust clinical evidence is still emerging, the study of AVPC-TSG alterations in prostate cancer (PCa) is promising. Alterations in TP53, RB1, and PTEN, as well as the combined loss of AVPC-TSGs, may have significant implications for prognosis and treatment. These biomarkers might help predict responses to various therapies, including hormonal treatments, cytotoxic agents, radiotherapy, and targeted therapies. Understanding the impact of these molecular alterations in patients with PCa is crucial for personalized management. In this review, we provide a comprehensive overview of the emerging prognostic and predictive roles of AVPC-TSG alterations across PCa stages. Moreover, we discuss the implications of different methods used for detecting AVPC-TSG alterations and summarize factors influencing their prevalence. As our comprehension of the genomic landscape of PCa disease deepens, incorporating genomic profiling into clinical decision making will become increasingly important for improving patient outcomes.

Ablation pressure evolution and applicability of exponential laws in laser ramp compression

The laser ablation pressure is often estimated by an exponential scaling law, which is determined by integral averaging of 1–2 ns short pulses. Here, we report a direct, continuous measurement of ablation pressure of a 3–10 ns ramp 351-nm laser pulse. Aluminum is deposited on LiF window, ablation pressure is inferred from the particle velocity of interface using the backward integration method, combined with incident ramp shaped laser intensity, and the real-time laser-driven ablation pressure as a function of incident laser power density on an aluminum target is obtained. For the same ablation pressure scale, when intensity is higher than 1TW/cm2, the surface illuminated intensity of laser should be modified with the cosine of incident angle, which agrees well with the modified Manheimer model [Scheiner and Schmitt, Phys. Plasmas 26(2), 024502 (2019)]. On the other hand, the incidence angle has the least effect when the intensity is below 0.1 TW/cm2. In the range of 0.1–1 TW/cm2, a significant loss in ablation pressure is observed, deviating notably from the exponential scaling relationship. This characteristic makes the laser direct drive ramp loading technique unfriendly to elastoplastic and phase transition problems.

Numerical and experimental investigation of resin flow, heat transfer and cure in a 3D compression resin transfer moulding process using fast curing resin

Compression resin transfer moulding (CRTM) has been widely used to manufacture automotive parts with reduced production cycle times. With the development of fast curing thermosetting resins, the CRTM process is a viable option for the high production rates in the transportation industry. However, the dynamic resin curing behaviour poses a potential risk of manufacturing defects in the part. In order to reduce the risk during the development of the tool and the process parameters, this paper proposes a modelling framework for the CRTM process when using fast curing resin systems. The work specifically focused on the coupling between heat transfer, resin cure, resin flow and preform compaction using a commercial code, PAM-RTM. The tool captures accurately the preform filling, temperature and resin pressure evolution during the injection and compression phase. The application of the framework was demonstrated for a complex 3D demonstrator. The predicted preform filling had an accuracy of 73% for the flow front evolution compared to the experimental results. This work demonstrates the validity of the framework proposed when dealing with resin systems that are challenging to process.

Simulation research on the blister evolution behaviors of UMo/Zr monolithic fuel elements

Blister behavior is one of the main failure modes of UMo/Zr monolithic fuel elements during irradiation. The temperature of fuel elements may increase greatly so that the fuel elements may be destroyed. Post-irradiation annealing tests are used to study the blister behaviors of fuel elements under high temperature. In this study, a simulation method is developed based on the finite element method to study the evolution of blister behaviors of UMo/Zr monolithic fuel elements in the blister tests, taken into considering that the evolution of bubble pressure should be coupled with the deformation of cladding. The influence of creep rate of the cladding on the evolution of blister height is analyzed. The study shows that the unrecoverable creep deformation of the cladding, which occurs under high temperature, is the major factor in the increment of bubble height. The increase of bubble height mainly occurs during the heat preservation process and the initial stage of cooling process. The creep rate of cladding is positively related to the evolution of bubble height.

Nonlinear pressure evolution in wellbore during the tubing conveyed perforation process

Abstract With increasing wellbore depth, the environmental conditions become progressively more severe, characterized by elevated temperatures and pressures. Consequently, the pressure variations within the well induced by Tubing Conveyed Perforation (TCP) operations exhibit a more pronounced intensity. These nonlinear pressure fluctuations generate significant impact loads at the bottom of the perforating gun, which can cause failure of the perforating tubing. A transient nonlinear pressure field model of perforation explosion was established based on hydraulic-mechanical coupling to effectively control the risk of accidents. The model considers the effects of several hundred perforation charges and their precise placement in relation to blind holes, thus taking into account the impact of shot density. As a result, the model more accurately reflects actual field conditions. The study investigated the evolution of nonlinear pressure fields at different positions of the entire tubing under perforation explosion and analyzed the influence of different factors on nonlinear pressure fluctuations at the bottom of the perforating gun. The results showed that the peak pressure of the perforation section was much higher than that of the tubing section and the rathole section, maintaining at approximately 200 MPa. The pressure wave attenuated to the initial wellbore pressure of about 80 MPa only seven meters away from the perforation section center. The peak pressure at the bottom of the perforating gun was positively correlated with the initial wellbore pressure, perforating fluid density, shot density, and quantity of explosive. These results provided guidance for the prediction of TCP wellbore nonlinear pressure fluctuation.

Effective Stress-Based Numerical Method for Predicting Large-Diameter Monopile Response to Various Lateral Cyclic Loadings

Extreme marine environmental cyclic loading significantly affects the serviceability of monopiles applied for the foundation of offshore wind turbines (OWTs). Existing research has primarily used p-y methods or total stress-based models to investigate the behavior of monopile–marine clay systems, overlooking the pore pressure development in subsea clay. Studies on the effective stress-based behavior of clay under various lateral cyclic loading conditions are limited. This paper presents an effective stress-based 3D finite element numerical method developed to predict key behaviors of pile–clay systems, including permanent pile rotation under cyclic loading, pile bending moment, and the evolution of pore pressure in subsea clay. The model is verified by contrasting the simulations results to centrifuge experimental results. Cyclic lateral loading is divided into average cyclic load and amplitude of cyclic load to investigate their impacts on the pile–clay system response. The research findings offer insights for the design of large-diameter monopiles under complex cyclic loading conditions.

Hydrocarbon Accumulation and Overpressure Evolution of the Ordovician Carbonate Reservoirs in the Tahe Area, Tarim Basin, NW China

The recovery of reservoir paleo-pressure has been a key focus in hydrocarbon accumulation research. The evolution of paleo-pressure in carbonate reservoir rocks has long been a research challenge for researchers. Using the Tahe area in the Tarim Basin as a case study, this paper proposes an idea for studying the paleo-pressure evolution in carbonate rocks through fluid inclusions. A series of methods, including cathodoluminescence, fluid inclusion petrography, laser in situ U–Pb isotope dating, and microthermometry, were employed to determine the stages of hydrocarbon accumulation. Additionally, the paleo-pressure of oil inclusions from different stages has been restored, and the pressure evolution of the Ordovician carbonate reservoirs in the Tahe area was reconstructed. The study identifies four stages of oil charging in Ordovician carbonate reservoirs. The four oil-charging events occurred during the Caledonian (459–450 Ma), Hercynian (320–311 Ma), late Indosinian (227–213 Ma), and Yanshanian (134–117 Ma) periods. The overpressure evolution indicates that the Cambrian source rocks reached the first oil generation peak and started to expel hydrocarbons during the late Caledonian period. Oil mainly migrated vertically along strike-slip faults and accumulated in fracture-cavity karst reservoirs. At the same time, the reservoir pressure increased rapidly. Subsequent tectonic compression caused uplift and erosion, leading to the destruction of the oil reservoirs and a decrease in pressure. During the Hercynian period, hydrocarbons migrated and accumulated in reservoirs, leading to an increase in reservoir pressure. Subsequently, a slight formation uplift occurred, which caused a decrease in pressure. During the late Indosinian period, the third stage of oil accumulation led to an increase in reservoir pressure. Tectonic uplift during the Yanshanian period caused reservoir destruction and adjustment, resulting in a decrease in pressure. Reservoir pressure increased with oil charging during the Yanshanian period. Subsequently, a large number of faults developed in the study area, causing further destruction and re-adjustment of the oil reservoirs, which led to a decrease in pressure to the current state of normal pressure or weak overpressure.

Correlation characteristics of oscillation dynamic and acoustic behavior of a sonoluminescence cavitation bubble

The acoustic cavitation oscillation behavior of a single bubble and the resulting characteristic pressure evolution is a complex dynamic phenomenon. The coupling mechanisms among many characteristic pressures that affect the oscillation characteristics are still ambiguous. A correlation method is applied to analyze the degree of correlation between characteristic pressures and bubble oscillations. The effects of ambient pressure, bubble state, and propagation of driving acoustic pressure on bubble oscillation and size were investigated. The results indicate that the viscosity is the dominant factor affecting bubble oscillating velocity during the growth or collapse processes. The surface tension is strongly correlated with the bubble oscillation, and the oscillating velocity of a bubble greatly suppresses the effect of the viscosity on the bubble oscillation. In particular, the sinusoidal variation in driving acoustic pressure strongly correlates with bubble radius oscillation, and its correlation with bubble acceleration increases linearly. Moreover, two linear relationships between the ambient pressure and the frequency to the characteristic radius are obtained.

Effect of shear-thinning rheology on the dynamics and pressure distribution of a single rigid ellipsoidal particle in viscous fluid flow

This paper evaluates the behavior of a single rigid ellipsoidal particle suspended in homogeneous viscous flow with a power-law generalized Newtonian fluid rheology using a custom-built finite element analysis (FEA) simulation. The combined effects of the shear-thinning fluid rheology, the particle aspect ratio, the initial particle orientation, and the shear-extensional rate factor in various homogeneous flow regimes on the particles dynamics and surface pressure evolution are investigated. The shear-thinning fluid behavior was found to modify the particle's trajectory and alter the particle's kinematic response. Moreover, the pressure distribution over the particle's surface is significantly reduced by the shear-thinning fluid rheology. The FEA model is validated by comparing results of the Newtonian case with results obtained from the well-known Jeffery's analytical model. Furthermore, Jeffery's model is extended to define the particle's trajectory in a special class of homogeneous Newtonian flows with combined extension and shear rate components typically found in axisymmetric nozzle flow contractions. The findings provide an improved understanding of key transport phenomenon related to physical processes involving fluid–structure interaction such as that which occurs within the flow field developed during material extrusion–deposition additive manufacturing of fiber-reinforced polymeric composites. These results provide insight into important microstructural formations within the print beads.

Comparison of mechanical response of head structure with different brain material models under impact

Abstract Brian material models and mechanical properties are very important for pressure evolution experiments and numerical simulations in head structure under impact. A simplified head structure with core-shell finite element model was established, and the motion, skull stress, skull deformation, and brain stress were numerically simulated with different soft tissue material models. The equivalence of the material model in stress propagation simulation was discussed. In the present work, it showed that when the head with impact velocity of 1m/s, the head structure rebound with a velocity of 0.6 m/s ∼ 0.8m/s, and occurred between 600μs and 1000μs due to different material models, at this time, the stress wave oscillation propagated in the skull underwent 3-5 repeated loads. The positive pressure on the impact side of brain tissue could reach 400kPa ∼ 800kPa, the negative pressure on the opposite side was between −150 kPa to −385kPa, the skull strain was between −1.8 ‰ to −3.7 ‰, and the skull stress was between 25.3MPa ∼ 41.2MPa. In a larger range of impact velocities, material models with strain rate effect have more advantages in stress wave transmission and pressure changing within the core-shell structure. The strain rate effect characterized only by creep and relaxation has limited effects on impact simulation, and directly introducing different strain rate mechanical property interpolation for hyperelastic model simulation is more effective.

Coupled Hydro-Gas-Mechanical 3D Modeling of LASGIT Experiment

Gas transport simulation in bentonite for radioactive waste disposal poses challenges for numerical models due to its complex microstructure. Understanding the processes involved is a prerequisite for assessing gas flow's impact on repository layouts. The DECOVALEX23 (D-2023) Task B (Large Scale Gas Injection Test: LASGIT) project aims to advance numerical techniques for predicting gas flow in repository systems through gas injection tests on compacted bentonite at the British Geological Survey (BGS). This study develops a comprehensive coupled hydro-gas-mechanical 3D numerical model to simulate the test, considering heterogeneous initial permeability and embedded fractures. Addressing bentonite swelling, three gap closure scenarios for the canister-bentonite blocks gap interface were considered. The model reproduces observed test behaviors, capturing preferential gas flow paths. Sensitivity analysis explores variations in volume factor sensitivity, calibration, hydraulic conductivity of interfaces, heterogeneity, permeability, and model parameters, contributing to a deeper understanding of the phenomenon's complexity. The proposed hydraulic modeling, enriched by considerations of gap closure states, predicts measured evolution of gas injection trends. suggesting reliability and potential applicability for similar conditions and facilitating a comprehensive analysis of its impact on gas testing processes. Additionally, the embedded fracture models underscore the critical role of fracture behavior and dilatancy in determining the system's hydro-mechanical response, with significant sensitivity to these factors influencing stress and pore pressure evolution. Hydro-mechanical models demonstrate that modeling approaches involving embedded fractures and dilatancy significantly influence gas pathways and entry gas pressure. System volume plays pivotal role in the analysis, while sensitivity analysis of contact transmissivity reveals potential influences on preferential gas pathway formation. Hydraulic and hydro-mechanical modeling methods show promise for further numerical investigations, indicating potential for yielding meaningful insights in future studies.

A phase-diagram-formulated EOS and fluid-solid coupling analysis for eco-friendly blasting of carbon dioxide phase transition

The Carbon dioxide (CO2) phase transition blasting is a state-of-the-art technology in fields of geotechnical, geological, and mining engineering, due to its advantages of high safety, environmental friendliness (Non-toxic and smoke-free), and cost-effective design benefited from the low-temperature characteristics. However, the evolution mechanism of CO2 within the pressure vessel before the blasting is still not clearly revealed. To address this issue, a phase-diagram-formulated Equation of State (EOS) is proposed to describe the phase evolution and mechanical behaviors of CO2. Furthermore, a fluid-solid coupling simulation model is established using the Euler grid-based Finite Element Method (FEM). The simulation model is validated through CO2 phase transition blasting experiments and then used for the mechanism analysis. The results reveal that the initial rapid rise, further slow increase, and extremely rapid decline of the pressure evolution in the vessel are dominated by the combination of heat absorption and external work, the phase transition of CO2, and the failure of the rupture disc, respectively. In addition, the influence laws of combustion agent energy, environment temperature and rupture disc strength on the blasting are systematically investigated. The final conclusions may provide useful insights for the design of CO2 phase transition blasting and the development of eco-friendly blasting technologies.

Numerical study of paste-bridge transfer process for laser induced high-viscosity silver paste

Laser-induced forward transfer (LIFT) is promising for solar-cell metallization and electronic printing due to its low dependence on paste viscosity and nozzle-free process. In this paper, the transfer process and morphological characteristics for LIFT of high-viscosity silver paste were studied through simulations and experiments. The shear-thinning rheological properties were considered using the fitted Carreau model. Variations of paste protrusion with single pulse energy and time were obtained from the high-speed imaging. The evolution of initial pressure that induces the paste protrusion was solved inversely and quantitatively expressed by a polynomial function. The internal pressure should be sufficiently larger than 40 MPa to induce the effective transfer. In the simulation, the induced bubble undergoes a non-spherical transition from mushroom to pea-pod and capsule shapes due to constraints from surrounding paste and substrate. The deposition morphology formed by the induced mushroom-shaped bubble shows high printing precision with thin width (<30 μm) and large height (∼10 μm). The simulated diameter and height of transferred single voxel agree with those from experimental measurement. It can gain insight into the transfer dynamics of high-viscosity pastes and provide process optimization for precision printing of voxels by LIFT.

Spatiotemporal evolution and influencing mechanisms of carbon pressure at the county scale: A case study of central-south Liaoning urban agglomeration, China

Achieving carbon neutrality necessitates a dual focus on minimizing carbon emissions and maximizing carbon sequestration, rather than solely concentrating on emission reduction. This study proposes a Carbon Pressure Index (CPI) to assess the equilibrium between emissions and sequestration, determine the factors influencing varying carbon pressure levels, and formulate region-specific strategies based on these levels. A nested methodological approach, combining spatiotemporal leaps analysis and quantile regression, is employed to appraise county-level carbon pressure dynamics across multiple quantiles in the central-south Liaoning urban agglomeration (CSLUA) from 2002 to 2021. Three principal findings were derived: Firstly, the spatiotemporal distribution of the CPI across CSLUA districts and counties demonstrates regional differentiations conforming to a gradient pattern, with values declining from urban centers toward peripheral areas. Carbon pressure is greater in the west, less in the east, and critically high in the central-western zones. Secondly, the spatial distribution of the CPI indicates clear high-high and low-low agglomeration clusters, suggesting persistent local structures that indicate path dependence and resistance to change in carbon pressure transfer. While the central-western regions exhibit further changes, the eastern areas maintain relative stability. Thirdly, environmental technology factors constrain most districts and counties, while the combined influence of industrial activity and population, along with economic and urbanization pressures, have predominant effects in smaller areas in the central-western region. This highlights the effectiveness of the nested spatiotemporal leaps and quantile regression model in explaining the driving forces underlying the spatiotemporal shifts in CPI. The results suggest that attaining superior regional low-carbon development requires rectifying the asymmetry between carbon sources and sinks, considering the driving forces of diverse transition pathways and their interactions, to finally achieve synergistic optimization that incorporates both shared and unique regional characteristics.

Investigating Electro-Chemo-Mechanical Properties of Conversion Cathodes for Solid-State Batteries

Solid-state batteries (SSBs) could offer higher energy density and improved safety compared to traditional Li-ion batteries. Challenges remain, however, including contact loss/fracture and the effective design of high-conductivity cathode composites. Intercalation-type oxides such as LiNixMnyCo1-x-yO2 (NMC) are widely used in SSB cells. However, these materials have limited capacity and are expensive. Conversion materials such as sulfur, sulfides, and fluorides, on the other hand, show much higher capacity and have been widely investigated for batteries with liquid electrolytes. While their use in conventional Li-ion batteries is challenging due to detrimental interactions with the liquid electrolyte, solid-state batteries (SSBs) offer a potential solution due to improved stability with solid electrolytes. However, conversion cathodes undergo relatively large volume changes during charging and discharging reactions. This volume expansion and contraction is of particular concern for SSBs, since such changes in the all-solid-state environment may lead to interfacial contact loss, cracks within the composite cathode, and degradation of performance.Here, we investigate the electro-chemo-mechanical evolution of various high-capacity conversion-type solid-state cathode composites (sulfur and other transition metal sulfides). X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) reveal redox reactions at transition metal sites in the composite cathodes, and electron microscopy is correlated to these measurements to determine how cracks evolve within the composite electrodes throughout cycling. The combined electrochemical and spectroscopic measurements reveal that while sulfur has a single conversion step, transition metal sulfides have a more complex, multi-step conversion mechanism. Real-time stack-pressure monitoring is used to provide insight into how stack pressure changes are linked to the diverse reaction pathways during charge and discharge of different conversion cathode materials. We show that there is different pressure evolution behavior for various conversion materials, and the electrode microstructure is also shown to influence stack pressure evolution. Overall, this study gives insight into material evolution and degradation mechanisms, guiding the design of superior cathodes for SSBs.

Frost heave cracking and uniaxial compression failure behavior of sandstone samples containing a flaw filled with water

The frost heave failure mechanism of fractured rock mass is a complicated problem faced by engineering construction in cold area. In this study, low temperature frost heave test and post-freezing uniaxial compression test on sandstone samples with a water-filled flaw were carried out. The frost heave cracking mode, frost heave pressure, frost heave cracking criterion and the effect of frost heave-induced cracks on post-freezing uniaxial compression failure behavior under different flaw inclination angles (0 ~ 90°) and freezing temperatures (–10~–40 °C) were investigated. Frost heave cracks initiate and extend along the coplanar direction of flaws. The frost heave damage degree decreases with the increase of flaw inclination angle. As the freezing temperature drops, the flaw cracking length first increases greatly, and then decreases, reaching the maximum at − 15 °C. The evolution of frost heave pressure can be divided into six stages: pre-freeze stage, rapid increase stage, rapid decrease stage, stable stage, slight rebound stage and dissipation stage. The peak frost heave pressure first increases and then decreases with the increase of flaw inclination angle, and reaches the maximum at 60°, and increases as the freezing temperature drops. Formulas for calculating the critical stress intensity factor KIC for flaw frost heave cracking are provided, considering flaw inclination angle or freezing temperature. When the flaw is within a certain range of inclination angles (45 ~ 75°), cracks under uniaxial compression will extend from the frost heave-induced cracks.

Numerical Simulation Study of Salt Cavern CO2 Storage in Power-to-Gas System

China’s renewable energy sector is experiencing rapid growth, yet its inherent intermittency is creating significant challenges for balancing power supply and demand. Power-to-gas (PtG) technology, which converts surplus electricity into combustible gas, offers a promising solution. Salt caverns, due to their favorable geological properties, are among the best choices for large-scale underground energy storage in PtG systems. CO2 leakage along the interlayer and salt rock–interlayer interfaces is a key constraint on the CO2 tightness of subsurface salt caverns. This paper focuses on the critical issue of tightness within salt cavern CO2 storage, particularly in the Jintan region. A coupled hydro-mechanics mathematical model is developed to investigate CO2 transportation and leakage in bedded salt caverns, with key variables such as permeability range, pore pressure evolution, and permeability changes being analyzed. The results reveal that permeability plays a decisive role in determining the CO2 transportation rate and leakage extent within the salt rock layer. Notably, the CO2 transportation rate and influence range in the mudstone interlayer are significantly larger than those in the salt rock over the same period. However, with prolonged storage time, the CO2 transportation rate and pressure increase in both salt rock and mudstone interlayer exhibit a decreasing trend, eventually stabilizing as the CO2 pressure front reaches the boundary of the simulation domain. Furthermore, elevated operating pressure markedly expands the permeability range and results in higher cumulative leakage. For a specific salt cavern, the CO2 leakage range can reach up to 142 m, and the leakage volume can reach 522.5 tonnes with the increase in operating pressure during 35 years of operation. Therefore, the setting of operational pressure should fully consider the influence of permeability and mechanical strength of the salt rock and mudstone interlayer. These findings provide valuable insights into optimizing the sealing performance of salt cavern CO2 storage systems under varying conditions.

Modeling and Simulation of Multi‐Material and Complex‐Shaped Gun Propellant Combustion in Closed Vessels

AbstractThe geometric shape and material structure of gun propellant grains control the pressure evolution during combustion and, consequently, the performance of the ammunition. Due to the large number of degrees of freedom, additive manufacturing offers novel opportunities for grain shape and structure design. However, this new freedom necessitates the development of new algorithms for modeling and simulation of surface regression. In traditional combustion models, it is assumed that the propellant′s burn rate is a global quantity on its surface, which enables separate simulation of the surface regression and pressure evolution. To exploit the full potential of additive manufacturing and optimize designs for different applications, it is necessary to simulate grain structures with locally different burn rates on the surface. This work presents a model to simulate quantitatively the combustion of multi‐material and complex‐shaped solid propellant grains in a closed vessel for the first time. A lumped parameter pressure model is coupled with a surface regression simulation based on the level set method. The model is validated by comparison to analytical surface regression. Then, for the first time, a combustion simulation of a multi‐material ball propellant grain consisting of two hemispheres in a closed vessel is presented. Compared to a combustion simulation using global and weighted mean burn rate values, the pressure and vivacity curve shows significant differences. This demonstrates impressively that for predicting the performance potential of multi‐material and complex‐shaped solid gun propellant grains, a quantitative and accurate combustion simulation is indispensable.

Magnetic structure and magnetic properties of Fe3BO5 and Mn3BO5 ludwigites

The magnetic ground state of transition metal ludwigites Fe3BO5and Mn3BO5was studied via the combination of representations analysis and the following DFT total energy calculations of possible magnetic configurations. The distinct in the magnetic properties of ludwigites was analyzed through estimation of exchange constants. The pressure evolution of manganese magnetic moments in Mn3BO5reveals the site-dependent behavior of magnetic moments. The manganese magnetic moments in 4-2-4 triads experience the sharp decrease above the pressure of 50 GPa, whereas magnetic moments in 3-1-3 triads have the weak dependence on pressure. The pressure-induced transition from half-metal state to metal state is also being found in Mn3BO5.