Numerical Simulation Method Research Articles

Evolution law of overlying rock fracture field in goaf mining with double-roof-cutting retaining roadway

This study comprehensively combines physical analog modeling, numerical simulation, on-site monitoring, and other methods to explore the overburden rock fissure development characteristics under double-roof-cutting (DRC) with retained roadway conditions. The analysis of performed tests, simulations, and on-site monitoring proves that under the above mining conditions, the stress transfer between the roof plates of the open area and the roadway on both sides of the cut top is interrupted, the overburden load being retained in the middle of the open area. The stress in the middle of the open area of the former is increased by 5% compared with that of the latter, with a higher degree of stress increase. The amount of overburden rock subsidence in the open area of the former is reduced by 45–80% compared with the latter. Under DRC, heights of the overlying rock collapse and fissure zones are 18 m and 40 m, respectively, versus 15 m and 46 m of those without roof-cutting. Fissures in both zones are the most developed, turning into gas transportation channels. This study findings provide theoretical basis for exploring the gas transportation patterns in double-cutting top tunnels.

Numerical Modeling and Optimization Design of Embedded Rubber Waterstops in Tunnel Lining

Tunnel water leakage is a common issue. Embedded rubber waterstops are crucial in ensuring the waterproofing performance of mountain tunnels. The deformation performance of a rubber waterstop directly impacts its effectiveness, with structural parameters playing a key role. This study employs numerical simulation methods to quantitatively assess the impact of structural parameters—such as the central hole, ribs, and flanges—on the deformation performance of waterstops. The parametric analysis reveals significant variations in how different structural components affect the deformation performance, as indicated by the defined deformation stress influence rate. Specifically, the deformation performance of the embedded waterstop under tensile, compression, and settlement deformations shows a correlation with factors such as the ratio of the central hole opening rate to thickness and the inner and outer diameters. Additionally, an optimization analysis, taking both economic and performance factors into account, was conducted on 16 types of waterstops with different central hole parameters, from which the optimal waterstop was selected. This research provides a scientific basis for enhancing the deformation performance of waterstops and optimizing their structure.

Numerical Analysis of Transient Burn Injury Grading Through Coupled Heat Transfer and Damage Integral Modeling

The accurate assessment of parameters such as burn degree, volume, and depth is a prerequisite for the effective treatment of patients. However, as an unsteady heat transfer process, the temperature of the burn damage volume changes over time, and it is difficult to accurately calculate the integral value of the damage, which is used to assess the burn degree. Therefore, it is impossible to accurately determine the location and volume of damage at all burn degrees. In this study, the C language is used to program a user-defined function of the burn damage integral formula, and the coupled numerical simulation method is used to calculate the heat transfer and damage in a high-temperature water burn process. Then, the temperature and burn damage integral value of each point can be determined to accurately assess and distinguish the burn degree in real time, and estimate the position distribution, volume size, and transient change trend of each burn degree. Under the working conditions selected in this paper, the heat source mainly affects the epidermis and dermis directly below, and has less influence on the area above, which is in convective heat transfer. The damage integral value is very sensitive to temperature, and the highest damage integral value caused by 373 K is two and four orders of magnitude higher than that of 363 K and 353 K, respectively. The increase in the heat source temperature caused the volume of a third-degree burn to increase rapidly in the early stage of injury, but the volume of second-degree and first-degree burns did not change much. After heating at 373 K for 15 s and delaying the action for 45 s, the volume of first-, second-, and third-degree burns accounted for 0.4, 2.9, and 1.9%, respectively, and the total volume of damage accounted for only 5.2% of the total volume.

A literature review on model tests for flooding and motions of damaged ships

During the past decades, experiments with scale models have been widely conducted to study the flooding process and motions of damaged ships, both in calm water and in waves. Survivability tests in irregular beam seas have been well-established and widely used, also commercially, to verify the compliance with the so-called Stockholm Agreement regulatory requirements. However, model tests for both transient and progressive flooding modes have mainly targeted at obtaining experimental data for validation of numerical simulation methods. This is becoming more important as increased computing capacity has enabled practical use of first principle tools for assessing damages stability. In this review, the different model test types and typical experimental setups are analyzed. In addition, the applied scales factors are studied and some research gaps are pointed out. Despite notable achievements in the past, further model tests are still considered essential for obtaining reliable experimental data on certain flooding mechanisms. Consequently, some recommendations for future experiments are also given.

Numerical investigation on the error of volume-averaged reaction rate model for the low-velocity filtration combustion with hybrid-scale method

Numerical investigation on the error of volume-averaged reaction rate model for the low-velocity filtration combustion with hybrid-scale method

Research and evaluation of turbulent jet ignition mode for improving combustion performance of ethanol rotary engine

Research and evaluation of turbulent jet ignition mode for improving combustion performance of ethanol rotary engine

Enhancing overall performances of large constructed wetlands using an integrated approach of numerical simulation and response surface method--Taking Bagong hybrid CWs as an example.

Constructed wetlands (CWs) with low carbon properties represented an effective approach for treating low-polluted water and improving water quality. Here, a research scheme was proposed to achieve maximum operation benefits of the large-scale CWs through parameter identification, operation simulation, evaluation, and analysis of the water quality process. Based on the two-dimensional water hydrodynamic model coupling with the Eco-Lab water quality module (with nutrients), simulation for Bagong hybrid CWs was successfully conducted. Variables were estimated using response surface design (RSD), and the values of model parameters were calibrated in accordance with central combination design (CCD) experiments. Ten key parameters in the water quality process affecting the overall pollutant removal of CWs were identified, and the water quality model of the CWs could be replicated well with the actual situation within the 95% confidence interval. The water purification effect of the CWs under five different influent flow conditions was simulated, and the maximum hydraulic loading (0.036m3·(m-2·h-1)) of the CWs was determined with the effluent water quality to meet the design requirements. The integrated method could effectively enhance the efficiency of parameter calibration and significantly reduce the simulation workload. The results of pollutants migration and transformation under different influent conditions could provide a universally applicable and valid method in engineering applications, and process a promising application prospect.

Numerical simulation method for the laser powder bed fusion process by lattice Boltzmann and multi-phase field methods

Numerical simulation method for the laser powder bed fusion process by lattice Boltzmann and multi-phase field methods

Numerical study on leakage, diffusion and accident consequences of liquid hydrogen jet and analysis of influencing factors

Numerical study on leakage, diffusion and accident consequences of liquid hydrogen jet and analysis of influencing factors

A data-driven prediction method over the lifecycle of fracturing and production of horizontal wells in shale

Efficient determination of hydraulic fracture lengths and comprehensive comprehension of post-fracturing production performance are crucial for optimizing fracturing design and maximizing ultimate recovery. Nevertheless, numerical simulation methods demand high professional expertise and entail significant computational resources. Meanwhile, the complex coupling of multiple factors makes the direct application of existing neural networks to hydraulic fracturing scenarios challenging. To efficiently forecast the post-fracturing fracture network and the dynamic evolution of the pressure field during production, an intelligent prediction model for post-fracturing fractures is developed by integrating the fast Fourier transform structure, convolutional auto-encoder, and U-Net structure. This model is capable of predicting the intricate fracture morphology after fracturing. Furthermore, leveraging a feature fusion architecture combining the convolutional long short-term memory neural network and the channel attention module, a dynamic prediction model for the pressure field during post-fracturing production is proposed to capture pressure field fluctuations over time. The combination of these two models yields an intelligent prediction approach for horizontal well fracturing. The performance of the intelligent prediction model for post-fracturing fractures is evaluated by means of the F1 score, and a score higher than 0.90 is accomplished. The absolute error is used to assess the dynamic prediction model of the pressure field during post-fracturing production, with a single grid pressure error less than 1.0 MPa. The research findings suggest that the proposed intelligent prediction method for fracturing operations can enhance prediction efficiency and provide novel insight for optimizing fracturing design and augmenting final production capacity.

Modeling the water transport in water invasion channel with water invasion unit numerical simulation based on intelligent proxies

For gas reservoirs with edge water, water easily transport into the gas reservoir along the water invasion dominant channel, which results that the water production is higher than expected during the development of gas wells, and then affects the production of gas wells. We had derived a water invasion unit numerical simulation model of oil–water two-phase (WINS). It simulated the water invasion dynamic change in the hyperosmotic zone. But the Buckley–Leverett water flooding front propulsion equation is no longer applicable to the saturation tracking method in the gas reservoirs. The main reason is that the fluid transport between the gas–water two-phases is different from the traditional incompressible fluid transport. In this paper, a new water invasion unit numerical simulation method based on intelligent proxies and optimal control theory in complex gas reservoirs (WINS-G) is proposed. Compared with the WINS, the saturation tracking method of water invasion channel is improved. And it demonstrates a new insight into the water transport in water invasion channel. Through the discussion of model fitting efficiency, it is found that the number of invalid grids is reduced by WINS-G based on the idea of proxy model, and the work efficiency is improved by automatic history fitting on the basis that the model can meet the basic requirements of accuracy.

Influence of the hull shape of a submerged body on its movements in a near-surface water environment

ABSTRACT Forces and moments affecting a submerged body by liquid can have a significant effect on the nature of its movement under low submergence conditions. The study considers the movement of submerged bodies with various cross-sectional shapes near the free water surface, using the methods of experimental and numerical simulation. We numerically analysed the influence of the hydrodynamic pressure field formed around the body on the wave pattern when moving at different velocities, and determined the dependency of the wave resistance coefficient for models with given parameters. We determined the nature of the change in the theoretical dependencies of the lift force and trimming moment on the Froude number. The use of the towing tank allowed us to obtain the dependencies of the relative vertical displacement of submerged bodies of various shapes under the influence of the lift force and trim angles during their movement.

Analysis on the dust prevention mechanism of air curtain in fully mechanized excavation tunnel

Aiming at reducing the dust pollution during the tunneling process and improving the application efficiency of air curtain dust prevention technology, according to the changes of radial jet velocity (vr), axial extraction velocity (ve) and extraction distance (L) in the formation process of air curtain, the numerical simulation method was used to analyze the rules of airflow structure evolution and the diffusion characteristics of dust particles in fully mechanized excavation tunnel. The results indicate that as vr and ve increase, the migration path of the wall jet of the air curtain changes into an axial direction; as L decreases, the migration distance increases accordingly. These phenomena make the airflow distribution in the working face tends to be uniform. The dust diffusion distance reduces as well, wherein, the range of the discrete area of dust particles decreases sharply, until all dust particles are concentrated in the accumulation area. On this basis, the vr, ve and L were optimized and applied in the 63up08 fully mechanized working face. By the application of the optimal parameters, the average dust removal efficiency at the driver’s position increased by 71%. The dust concentration was reduced and the working environment had been improved effectively.

Multi-physics field coupling simulation and experimental study of new green and low energy consumption lithium molten salt electrolyser

ABSTRACT A new type of lithium molten salt electrolytic cell was studied by using multi-physics coupling numerical simulation method and verified by experiment. The distribution of temperature, potential, current density, fluid force and flow field in electrolytic cell was investigated. The results show that the minimum pole distance of the cell is 6 mm, which effectively reduces the pressure drop on the electrolyte to 0.1 V. The mixture of electrolyte and lithium metal can effectively transfer mass through the electrode gap, while the resulting chlorine gas acts as a power source for the entire electrolytic cell, and electric field analysis shows a significant reduction in energy consumption, validating the energy saving potential of the new structure. Pilot tests have determined an energy consumption of 28 KWH/kg of lithium with a current efficiency of 87.5%, a nearly 50% reduction in energy consumption and a more than 30% improvement in current efficiency compared to conventional systems.

Richards equation for the assessment of landslide hazards

In this study, we investigate numerical simulation models for water flow in variably saturated (unsaturated) soils. These models are crucial for addressing soil-related challenges and analyzing water-related risks, particularly in the context of water resource management, soil water-induced disasters, and the agricultural impacts of global environmental changes. The Richards equation is one of the most widely used models for simulating water flow in porous media, especially in unsaturated soils. However, as a highly nonlinear parabolic partial differential equation (PDE), it has limited analytic solutions, which often lack precision in practical scenarios. This necessitates the development of innovative and robust numerical methods for accurate simulations. We introduce a numerical procedure that linearizes the Richards equation using the Kirchhoff integral transformation, followed by discretization with various time-stepping schemes. This approach enables efficient and accurate modeling of water flow. To extend its application, we integrate the numerical solution with a hydrological infinite slope stability model to evaluate landslide hazards. Specifically, we calculate the factor of safety index based on an axisymmetric form of the Richards equation, which helps identify potential landslidenprone areas. Furthermore, our model provides a framework for predicting landslides by considering the interplay between water flow and the physical, geological, and topographical characteristics of a landscape. This integrated approach offers valuable insights for geohazard assessment and the mitigation of water-induced risks

Slit tube responses and rock fracture characteristics in slit charge blasting under high in situ stress

AbstractDeep mining of natural resources, like coal, is increasingly utilizing directional blasting technology with slit charge for rock blasting at greater depths. This study, based on numerical simulation methods, analyzes the dynamic behavior of slit charge blasting in three aspects: slit tube dynamic response, hoop stress evolution, and crack propagation. According to research findings, the failure mode of the slit tube mainly manifests as a tensile fracture of the inner wall and a shear fracture at the end connection, where the end connection of the slit tube is the weak point of the overall structure. The dynamic response of the slit tube mainly exhibits radial response in the vertical direction of the slit and hoop response in the slit direction. The hoop tensile stress plays a crucial role in determining the spread of cracks caused by explosions. As the in situ stress increases, the peak hoop tensile stress reduces, and the peak hoop compressive stress increases. This hinders the propagation of cracks. In addition, the directional impact is most pronounced in the middle of the borehole, with the longest primary directional crack observed. Conversely, the directional impact is least favorable near the bottom of the borehole. When the in situ stress reaches 60 MPa, the purpose of directional fracture has not been achieved, suggesting combining presplit blasting for in situ stress relief to improve rock breaking efficiency.

Numerical and Experimental Investigations of a Double‐Suction Pump With a Middle Spacer and a Staggered Impeller

ABSTRACTDouble‐suction pumps are among the most commonly used mechanical devices in irrigation and drainage. To investigate the effects of the impeller configuration with a spacer and staggered arrangement on the internal flow field and radial force characteristics of a double‐suction centrifugal pump, a comparison investigation was conducted using the same type of pump with three different impeller configurations: a symmetrically arranged impeller without a spacer, a symmetrically arranged impeller with a spacer and a staggered 25° arrangement impeller with a spacer. This study employed a combination of experimental and numerical simulation methods to analyse changes in the head, efficiency, transient radial force and internal flow field under three typical operating conditions. The results indicate that the staggered 25° arrangement impeller with a spacer results in a higher head and efficiency than both the symmetrically arranged impellers without a spacer and those with a spacer across most working conditions. Furthermore, the efficiency improvement is most significant at low flow rates for the staggered 25° arrangement impeller with a spacer compared with the other configurations. In terms of the internal flow field, the addition of a spacer and staggered 25° arrangement impeller effectively reduces the high‐velocity flow, making the pressure distribution gradient more reasonable and the turbulent kinetic energy distribution more uniform. Additionally, adding spacers and employing staggered arrangements effectively reduces the steady‐state radial forces as well as the main frequency amplitude of the radial force fluctuations on the impeller. This improves both the high‐velocity flow structure attenuation rate and outlet flow stability for double‐suction impellers. By comparing and analysing the external characteristics, internal flow field and radial force characteristics of different impeller configurations, this study proposes an improved impeller scheme based on a spacer and staggered arrangement, which provides a new optimization idea for improving the efficiency and stability of double‐suction centrifugal pumps in irrigation systems.

Dynamic Response Analysis of Dowel-Slot Grouting Assembly Station under earthquake action

In order to study the seismic performance of Dowel-Slot Grouting Assembly Station, the displacement and stress changes of the station and the cast-in-place station under horizontal, vertical and horizontal-vertical coupled earthquakes were compared by the finite element numerical simulation method based on a subway station in Changchun. The results indicate that the two stations have the same stress concentration position and the same weak point under different seismic actions, and both meet the aseismic requirements. Compared with the traditional cast-in-place station, the assembly station has obvious advantages in vertical seismic performance, but the horizontal seismic ability is relatively weak, and the difference of the displacement Angle between layers is 20%~60%. Compared with the difference of 46.43% in the maximum seismic stress and 28.51% in the vertical seismic time, the difference of 58.02% in the coupled seismic action shows that the stress concentration is more obvious. It provides reference for further optimization of assembly station.

NumSimEX: A method using EXX hydrogen exchange mass spectrometry to map the energetics of protein folding landscapes.

Hydrogen exchange mass spectrometry (HXMS) is a powerful tool to understand protein folding pathways and energetics. However, HXMS experiments to date have used exchange conditions termed EX1 or EX2 which limit the information that can be gained compared to the more general EXX exchange regime. If EXX behavior could be understood and analyzed, a single HXMS timecourse on an intact protein could fully map its folding landscape without requiring denaturation. To address this challenge, we developed a numerical simulation method called NumSimEX that models EXX exchange for arbitrarily complex folding pathways. NumSimEx fits protein folding dynamics to experimental HXMS data by iteratively comparing the simulated and experimental timecourses, allowing for determination of both kinetic and thermodynamic protein folding parameters. After analytically verifying NumSimEX's accuracy, we demonstrated its power on HXMS data from beta-2 microglobulin (β2M), a protein involved in dialysis-related amyloidosis. In particular, using NumSimEX, we identified three-state kinetics that near-perfectly matched experimental observation. This proof-of-principle application of NumSimEX sets the stage for harnessing HXMS to expand our understanding of proteins currently excluded from traditional protein folding methods. NumSimEX is freely available at https://github.com/JaswalLab/NumSimEX_Public.

Investigation on microperforated sandwich structures with light weight and broadband sound absorption: Influences of foam filling and core configurations

Structures with light weight and broadband sound absorption is of vital importance for noise control applications in engineering practice. Foams exhibit broadband but poor low frequency sound absorption, micro-perforated sandwich structures conversely possess good sound absorption at low frequencies due to resonance, the bandwidth is however limited. Micro-perforated sandwich structures with foam filling are therefore proposed in the paper to obtain wideband low-frequency sound absorption. An integrated analytical, numerical and experimental research is conducted to investigate sound absorption and lightweight characteristics of four commonly used micro-perforated sandwich structures with honeycomb (PHSP), corrugated (PCSP), N hybrid (PNHSP) and honeycomb-corrugated (PHCSP) cores. An analytical model is built to estimate sound absorption coefficient (SAC) based on the acoustic impedance theory and Johnson-Champoux-Allard model. Numerical simulation and experimental measurement methods are conducted simultaneously to validate the analytical model. The influences and underling mechanism of foam filling and filling configurations are explored, and it is found that melamine foam filling can enhance low-frequency sound absorption bandwidth of micro-perforated sandwich structures, and half-filled foam can bring in higher absorption peak values than fully filled foam due to more violent resonance. To overall evaluate both the lightweight and sound absorption performance of varied sandwich cores, a comprehensive evaluation index by the sound absorption and relative mass is developed. Results show that the PCSPs with lower half part filled foam perform best at both sound absorption and lightweight among all sandwich structures. Results of this paper can provide guidance for the application of sandwich structures.